The Horizontal Bearing Capacity of Composite Concrete ...horizontal bearing capacity of CCFSTPs when they interact with the surrounding rock and soil mass. e functional diﬀerence

Research ArticleThe Horizontal Bearing Capacity of CompositeConcrete-Filled Steel Tube Piles

Yunxiu Dong 12 Zhongju Feng1 Haibo Hu 1 Jingbin He 1 Qilang Zhang3

and Fuchun Wang1

1Highway School Changrsquoan University Xirsquoan Shaanxi 710064 China2School of Civil Engineering Longdong University Qingyang Gansu 745000 China3Guangdong Nanyue Transportation Investment amp Construction Co Ltd Guangzhou Guangdong 510000 China

Correspondence should be addressed to Yunxiu Dong dongyunxiu_0524163com

Received 31 July 2019 Revised 30 November 2019 Accepted 19 December 2019 Published 9 January 2020

Academic Editor Chun-Qing Li

Copyright copy 2020 Yunxiu Dong et alis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Steel casings (SCs) are extensively and increasingly used to stabilize the borehole wall in the construction of bridge pilefoundations Steel casings (SCs) together with reinforced concrete piles (RCPs) form composite concrete-filled steel tube piles(CCFSTPs) which differ significantly from ordinary RCPs in horizontal bearing capacity In this study based on the charac-teristics of CCFSTPs the horizontal bearing capacity of a CCFSTP was examined through a centrifugal model test with the lengthof the steel casing (LSC) and the modulus of the soil mass in the steel casing soil compaction zone (ESCSC_zone) as variables Pile-sidesoil resistance load-displacement curves and pile moment curves were obtained for the CCFSTPe results show that increasingLSC within a range of 12 cm significantly increases the ultimate horizontal bearing capacity of the CCFSTP and further increasingLSC beyond 12 cm produces a continuous increase in the ultimate horizontal bearing capacity of the CCFSTP but only to aninsignificant extent In addition increasing ESCSC_zone increases the ultimate horizontal bearing capacity of the CCFSTP but to arelatively small extent e results of this study provide a theoretical basis and technical support for the design and constructionof CCFSTPs

1 Introduction

Pile foundation [1ndash10] is an important part of highwaybridge construction In the construction of cast-in-placebored piles the steel casing is usually used to stabilize theborehole wall or solve the slurry leakage problem of hugecaves When the steel casing is recycled they are calledreinforced concrete piles (RCPs) However steel casings(SCs) used during construction are difficult to be recycledafter piles are built due to subsequent construction re-quirements and their relatively large buried depth ustogether with reinforced concrete (RC) the SC form aconcrete-filled steel tube composite structure which is calledcomposite concrete-filled steel tube (CFST) piles (CCFSTPs)in this study Moreover CCFSTPs have a large cross-sectionat the top and a small cross-section at the bottom as shownin the Figure 1 e bearing capacity of a CCFSTP has a

greater safety margin than that of an ordinary RCP of thesame diameter In fact CCFSTPs have already been widelyused in the construction of highway bridges However SC isbasically considered to be a safety margin for the pilefoundation e preservation of this safety margin needs tobe considered in design technique

Scholars worldwide have conducted research relevant tocomposite CFST structures e technical specification forCFST structures of China issued in 2014 mainly introducesdesign methods for circular CFSTs is specification usesconfinement theory and assumes that an increase in coreconcrete strength is directly proportional to the horizontalpressure provided by the outer steel tube [11] Severalcountries including the US and Japan have conductedresearch relevant to the use of CFST structures to buildfoundations e American Institute of Steel ConstructionrsquosLoad and Resistance Factor Design Specification stipulates

HindawiAdvances in Civil EngineeringVolume 2020 Article ID 3241602 15 pageshttpsdoiorg10115520203241602

design methods for composite columns is specificationconsiders the overall stability of members under axialcompression by treating CFST members as pure steelmembers and incorporating the strength of the concrete intothat of the steel [12] e Architectural Institute of Japanrsquosconcrete-filled steel tube (CFST) specification considers theconfining effects of the steel tube on the core concrete whencalculating the bearing capacity of a circular CFSTmember[13] e British Standards Institutersquos Steel Concrete andComposite Bridge Specification for design of concretebridges states that the core concrete is three-way compressedunder the constraint of a steel pipe and the strength is in-creased when calculating the bearing capacity of a circularCFSTmember [14] European Standardization CommitteersquosEurocode 4 Design of steel and for buildings pointed out thatthe design of the steel concrete composite structure issuperimposed on the full plastic section and then thebearing capacity is corrected by comparison and analysis ofthe test [15] Johansson et al [16] studied the mechanicalbehaviors of 13 CFST column specimens under three dif-ferent loading conditions through a static test and found thatthe bond strength greatly affected the confinement effectswhen the load was applied only to the concrete part and thusaffects mechanical properties of the columns Trentadueet al [17] proposes closed-form approximations of the axialforce-bending moment interaction diagrams for reinforcedconcrete columns and concrete-filled steel tubes with cir-cular cross-section Yousuf et al [18] studied the behavior ofhollow and concrete-filled stainless steel tubular columnsunder static and impact loading Patel et al [19 20] de-scribed verification and applications of a multiscale modelfor CFST columns Brown et al [21] Aguirre et al [22] andMontejo et al [23] studied the nonlinear seismic behavior ofreinforced concrete-filled steel tubes Jung et al [24] im-proved shear design equations through further experimentaland analytical research on shear resistance and behavior ofcircular CFT Du et al [25] and Ding et al [26] investigatedthe failure modes the impact force time history curves andthe strain time history curves to evaluate the behavior of theCFCST member under an impact load Zhu et al [27] andWang et al [28] studied the factors influencing the bearingcapacity of concrete-filled steel tube columns All of the

aforementioned studies focus on the mechanical propertiesand bearing capacity of composite steel tube-concretestructures However there is a lack of research on thehorizontal bearing capacity of CCFSTPs when they interactwith the surrounding rock and soil mass e functionaldifference between bridge pile foundations and CFST col-umns results in a difference in the horizontal bearing ca-pacity between CCFSTPs and CFST columns erefore itis necessary to study the horizontal bearing capacity ofCCFSTPs

In this study based on the centrifugal model test thehorizontal bearing capacity of a CCFSTP affected by thelength of the steel casing (LSC) and the elastic modulus of thesoil mass in the steel-casing soil compaction (SCSC) zone(ESCSC_zone) are examined e load transfer mechanism forthe CCFSTP under horizontal loading is analyzed with theaim of providing a technical basis for the design and con-struction of bridge pile foundations

2 Experimental Investigation

In order to study the horizontal bearing capacity of the pilesa series of centrifugal model tests were carried out to analyzethe effect of steel casing and soil modulus in the steel casingsoil compaction zone on the bearing capacity of the piles

21 Physical Model In order to study the difference inhorizontal bearing capacity between composite concrete-filled steel tube piles (CCFSTPs) and ordinary reinforcedconcrete pile (RCP) 4 model CCFSTPs and 1 model RCPwere designed as shown in Table 1 and Figure 2 taking intoaccount the influence of steel casing length e piles arefriction piles

e ground in the model is composed of 40 cm thicknoncollapsible loess In practice the steel casing has acompaction effect on the soil around the pile To truly reflectthe mechanical conditions of the original CCFSTP the soilcompaction effects of the steel casing on the horizontalbearing capacity of the CCFSTP were simulated in the modeltest by altering ESCSC_zone (the SCSC zone is a zone with athickness of 15mm around the steel casing where 15mm is

A

A-A

(a) (b) (c)

B-B

C-C

D-D

A B B C C

D D

Figure 1 Composition of CCFSTP (a) Steel casing (SC) (b) Reinforced concrete pile (RCP) (c) Composite concrete-filled steel tube pile(CCFSTP)

2 Advances in Civil Engineering

the radius of the steel casing) Due to the difficulty of op-erating within the limited space inside the model chamber asoil compaction mould designed in-house was used toprepare the foundation soil in the SCSC zone in advance[26] as shown in Figure 3

In this paper steel casing length LSC and ESCSC_zone wereselected as the variables Table 2 summarizes the test conditions

22 Material Properties Because cast-in-situ piles arecomposed of reinforced concrete it is difficult to form thesame strength of concrete as the prototype piles as soon aspossible erefore similar materials will be used for sim-ulation according to the recognition criteria e modelmaterial is controlled by the bending stiffness EI (elasticmodulus and moment of inertia) as shown in equation (1)In this study aluminum pipe was used as material for theordinary reinforced concrete pile Table 2 shows the char-acteristics of test piles Because Youngrsquos modulus of theprototype pile is 187GPa the similarity rate of 100 isavailable according to equation (1) and Table 3

n4EmIm EpIp

n4Emπ D4m minus d4

m1113872 1113873

64

EpπD4p

64 (1)

where Em is Youngrsquos modulus of the model Ep is Youngrsquosmodulus of the prototype Im is inertia moment of themodel Ip is inertia moment of the prototype n is thesimilarity rate Dm is outer diameter of the model dm isinner diameter of themodelDp is diameter of the prototype

Four model piles of composite concrete-filled steel tubepiles have the same materials with the ordinary reinforcedconcrete pile e steel casing was simulated by a steel pipeTable 4 shows the characteristics of the steel casing

e main physical properties of the noncollapsible loesswere tested by a consolidation test (Figure 4(a)) a moisturecontent test (Figure 4(b)) and a direct shear test(Figure 4(c)) Density was obtained according to the massand volume of the soil Compression modulus was obtainedby the consolidation test e moisture content was mea-sured by the moisture content test e internal frictionangle and cohesive force were calculated by the direct sheartest e results are shown in Table 5

23 Instrument of Experiments In this study TLJ-3 typegeotechnical centrifuge at Changrsquoan University with aneffective radius of rotation of 2m was used as shown inFigure 5e maximum centrifugal acceleration is 200g Ithas a container and a balancing container as a beam typeof the centrifuge e dimensions of the container are700mm in length 500mm in height and 360mm inwidth ere are 40 channels on the centrifuge whichcould transmit the collected data to the computer isstudy satisfied the similitude laws [29] Detailed similituderatios between the model and the prototype are shown inTable 6

BE120-3AA strain gauges with a sensitivity factor of20ndash22 and a resistance of 120Ω were used to measurethe strain of the piles To ensure a relatively high survival

Table 1 Size of model piles

Model pile number L (cm) LSC (cm) D (mm) DSC (mm) t (mm) tSC (mm)CCFSTP-1 35 20 25 30 2 2CCFSTP-2 35 16 25 30 2 2CCFSTP-3 35 12 25 30 2 2CCFSTP-4 35 8 25 30 2 2RCP-0 35 0 25 0 2 2Note L represents the length of themodel pile LSC represents the length of the steel casingD represents the outside diameter of themodel pileDSC representsthe outside diameter of the steel casing t represents the thickness of the model pile tSC represents the thickness of the steel casing

20cm 16cm 12cm 8cm

(a)

0cm

(b)

Figure 2 Photograph of the model piles (a) Composite concrete-filled steel tube piles with different steel casing length (b) Conventionalreinforced concrete pile without steel casing

Advances in Civil Engineering 3

rate for the resistance strain gauges after being buried inthe soil layer the model piles were cut open lengthwiseand six pairs of strain gauges were placed on oppositesides at a certain interval on the inner wall After thestrain gauges were affixed the model piles were pastedand restored by epoxy resin and the position of the pileshaft strain gauges were laid out as shown in Figure 6Since the depth of the pile body into the soil layer is 30 cmand the pile length is 35 cm the position of the first group

of the strain gauge is 5 cm away from the pile top esecond group to the fifth group of the strain gauge arelocated according to the length of steel casing To save thenumber of strain gauges and reflect the strain near thepile bottom the sixth group of strain gauges is arranged2 cm away from the pile bottom

e aluminium pipes and steel pipes were bonded withepoxy resin regardless of the friction between them Finallysandpaper was used to polish the outer surface of the model

Concrete cushion block

Stainless steel hoop

SCSC zone

Steel casing

Soil compactioncasing pipe

Model pile

53

44

44

4 35

1310

(a)


(b)

Figure 3 Schematic diagram of the soil compaction mould (unit cm)

Table 2 Test conditions

Name Steel casing length LSC (cm) ESCSC_zone (MPa)RCP 0 10ENon-SCSC zone

CCFSTPs

8 12 16 and 20 11ENon-SCSC_zone

811ENon-SCSC_zone 12ENon-SCSC_zone

13ENon-SCSC_zone 14ENon-SCSC_zone and15ENon-SCSC_zone

Note ldquoENon-SCSC_zonerdquo signifies the compressive modulus of the soil mass in the non-SCSC zone

Table 3 Characteristics of test piles

g levelPile length L Outside diameter D ickness t

Youngrsquos modulus E (GPa)Model (mm) Prototype (m) Model (mm) Prototype (m) Model (mm) Prototype (m)

100 350 35 25 25 2 02 402

Table 4 Characteristics of steel casing

g levelLength LSC Outside diameter D ickness t

Youngrsquos modulus E (GPa)Model (cm) Prototype (m) Model (mm) Prototype (m) Model (mm) Prototype (m)

100

20 20

30 3 2 02 16416 1612 128 8


pile to make its bearing characteristics more similar to theactual pile BW11-12 string compression-type minisoilpressure cells (diameter 12mm definition 1 με sensitivityfactor (025plusmn 001) range 0ndash12MPa accuracy0001MPa) were affixed to each pile at a certain interval tomeasure the pile-side soil resistance Figure 3 shows theplacement of the strain gauges and the soil pressure cells onthe CCFSTP

24 Test Procedure e specific steps are as follows and themain test procedures are shown in Figure 7

(a) To ensure uniform density of the soil in the con-tainer compress a certain mass of soil into a certainvolume In this test the soil density is 17 gcm3 andeach layer of soil is compressed to 2 cm Since thecontainer length is 70 cm and the width is 36 cmeach layer of soil is compressed to 5040 cm3 so thesoil quality required for each layer is 8568 g Firstweigh 8568 g of soil and put it into a plastic bagen use a shovel to evenly spread the soil into thecontainer Finally use a vibrator to compress the soilto 2 cm en drill holes according to the pile po-sition as shown in Figure 8 e depth of the hole is30 cme aperture was slightly smaller than the pilediameter which makes the axial resistance betweenpile and soil closer to the actual value Finally thepile was pressed into the hole

Table 5 Physical properties of loess

Name Density ρ(gcm3)

Compressive modulusENon-SCSC zone (MPa)

Moisture contentω ()

Cohesionc (kPa)

Internal frictionangle φ (deg)

Loess 17 198 135 27 21

Instrument compartment

Channel

Container

Balancing container

Arm

Base

(a)

Operating cabinet

Photographingcomputer Measuring computer

(b)

Figure 5 TLJ-3 type geotechnical centrifugal

(a) (b) (c)

Figure 4 Tests (a) consolidation test (b) moisture content test (c) direct shear test

Table 6 Similitude ratios in centrifugal model tests

Parameter RatioLength 1 nDiameter 1 nDisplacement 1 nMoment of inertia 1 n4

Stress and strain 1 1Force 1 n2

Note Centrifugal acceleration nmiddotg


(b) e container was put into the centrifuge(c) Firstly the reaction frame was bolted to the con-

tainer en soil pressure cells strain gauges andthe displacement gauges were connected to thecentrifuge channel

(d) 100 g level was conducted for five minutes(e) e data was transferred to the computer(f ) Repeate the steps above when one load ends Hor-

izontal loading was achieved by adding steel plates tothe loading platform (a hook at end of the strand)and the horizontal loading was divided into eightlevels the loading was 25N 50N 75N 100N125N 150N 175N and 200N as shown inFigure 9

3 Results and Discussion

31 CCFSTP Side Soil Resistance Similar patterns can beobserved for the variation in the pile-side soil resistance with

LSC under various horizontal loads Here and later the testcondition with a horizontal load of 150N is taken as anexample for analysis Figure 10 shows the variation patternsof the pile-side soil resistance with LSC

e pile-side soil resistance of the CCFSTP is lower thanthat of the ordinary RCP for the same depth and the pile-side soil resistance gradually decreases as the steel casinglength increases For the CCFSTP the pile-side soil resis-tance increases first and then decreases with increasingdepth e pile-side soil resistance approached zero at adepth of approximately 17 cm below the surface and itincreased as the depth increased further is is likely toindicate that the CCFSTP underwent inflection deformationat a depth of approximately 17 cm below the surface As thesteel casing length increased the maximum pile-side soilresistance of the CCFSTP gradually decreased e maxi-mum pile-side soil resistance of the CCFSTP is 1253 kPa1230 kPa 1205 kPa and 1181 kPa when steel casing lengthis 8 cm 12 cm 16 cm and 20 cm respectively which are109 126 144 and 161 lower than that of the

Strain gaugePressure cell

Model pile

75

84

times 3

= 12

5 times

4 =

20

35

25

75

8

(a)

BE120-3AA strain gauges

(b)

BW11-12 pressure cells

(c)

Figure 6 Placement of the strain gauges and the soil pressure cell (unit cm)


ordinary RCP respectivelyis is because as the steel casinglength increases the stiffness of CCFSTP increases More-over the diameter of the steel casing is slightly larger thanthe borehole size which has extrusion effect on the soil andwith the increase of the length of the steel casing the ex-trusion area of the steel casing and the soil increases andlarger pile-side soil resistance can be obtained Conse-quently the depth of the soil mass on the side of the pileaffected by the pile is increased which lead to a decrease inthe maximum pile-side soil resistance

Figure 11 shows the variation patterns of the pile-sidesoil resistance with ESCSC_zone

As ESCSC_zone values increases the pile-side soil resis-tance of the CCFSTP increases However the pile-side soilresistance of the CCFSTP remains lower than that of the

A A

B

B

(a)

25cm 20cm 25cm

10cm

35cm

5cm

(b)10

cm35

cm5c

m

18cm 18cm

(c)

Figure 8 e position of the model piles (a) Planar graph (b) A-A section diagram (c) B-B section diagram

Soil Pile Displacement gauge Reaction frame

First pour the soilinto the container

and compact it

en drill a holeand press the piles

into the hole

Install the displacementgauge on the reaction

frame

Fix the reactionframe to the container

Put the containerinto the centrifuge

Figure 7 e main test procedures

Adding round steel plates with holes to the hook at the end ofthe strand

Figure 9 Horizontal loading device


ordinary RCP e maximum soil resistances on the side ofthe CCFSTP were 1181 kPa 1208 kPa 1237 kPa1256 kPa and 1278 kPa when ESCSC_zone 11ENon-SCSC_zone12ENon-SCSC_zone 13ENon-SCSC_zone 14ENon-SCSC_zone and15ENon-SCSC_zone respectively which are 161 141121 107 and 92 lower than that of the ordinary RCPrespectivelyis is because as the modulus of soil mass in thesteel casing soil compaction zone increases the soil massaround the CCFSTP becomes denser and the area of the soilaround of the pile affected by the pile decreases resulting inan increase in the maximum pile-side soil resistance

32 Horizontal Bearing Capacity of the CCFSTPFigure 12 shows the load-displacement curves and load-displacement gradient curves of the CCFSTP under variousvalues of LSC

As demonstrated in Figure 12 under the same horizontaldisplacement the longer the length of the steel casing the

greater the load the pile can bear e load-displacementgradient curves of the CCFSTP under various LSC valuescontain no notable inflection points indicating that the pilehas not been damaged As a result the ultimate bearingcapacity of the pile cannot be determined based on theinflection points of the curves In this paper the ultimatehorizontal bearing capacity of the CCFSTP is controlled bydisplacement e horizontal load corresponding to whenthe CCFSTP underwent a horizontal displacement of04mm is used as its ultimate bearing capacity [30] Let αH bethe degree of impact on the ultimate horizontal bearingcapacity of the pile αH (H minus H0)H0 times 100 where H0 isthe ultimate horizontal bearing capacity of the ordinaryreinforced concrete pile (RCP) and H is the ultimate hor-izontal bearing capacity of the CCFSTP Figure 13 showshow the ultimate horizontal bearing capacity of the CCFSTPvaries with the steel casing length

As shown in Figure 13 the ultimate horizontal bearingcapacity of the CCFSTP is higher than that of the ordinaryRCP and it increased as LSC values increased e ultimatehorizontal bearing capacity of RCP (LSC 0 cm) is 695Ne ultimate horizontal bearing capacity of the CCFSTP is789N 837N 854N and 858N when the steel casinglength is 8 cm 12 cm 16 cm and 20 cm respectively Withthe increase of steel casing length the horizontal ultimatebearing capacity of CCFSTP increases gradually e reasonis that the diameter of the steel casing is slightly larger thanthe borehole size which has extrusion effect on the soil andwith the increase of the length of the steel casing the ex-trusion area of the steel casing and the soil increases andlarger pile-side soil resistance can be obtained e afore-mentioned analysis shows that the ultimate horizontalbearing capacity of the CCFSTP increased to a relativelylarge extent as the steel casing length increased within arange of 12 cm and that the ultimate horizontal bearingcapacity of the CCFSTP continued to increase as the steelcasing length increased beyond 12 cm albeit to a relativelysmall extent When the steel casing length is 8 cm the ul-timate bearing capacity is increased by 133 indicating thatthe existence of steel casing can improve the ultimate bearingcapacity When the steel casing length is 16 cm the increaseof ultimate bearing capacity is 227 It is only 25 higherthan the CCFSTP with a steel casing length of 12 cm is isbecause when the steel casing length exceeds a certain valuethe increase of the steel casing length has little effect on thehorizontal bearing capacity of the CCFSTP

Figure 14 shows the load-displacement curves and theload-displacement gradient curves of the CCFSTP undervarious values of ESCSC_zone

As demonstrated in Figure 14 the load-displacementgradient curves of the CCFSTP under various values ofESCSC_zone contain no notable inflection points indicatingthat the pile has not been damaged Similarly the ultimatebearing capacity of the CCFSTP is also controlled by hor-izontal displacement In addition it can also be seen fromFigure 14 that under the same horizontal displacement thelarger the modulus of soil mass in the steel casing soilcompaction zone the greater the load the pile can bearFigure 15 shows the variation pattern of the ultimate

8cm16cm

0cm12cm20cm

25

20

15

10

5

0

Dep

th (c

m)

0 25 50 75 100 125 150Pile-side soil resistance (kPa)

Figure 10 Change rule of the pile-side soil resistance with LSC

10ENon-SCSC_zone

12ENon-SCSC_zone14ENon-SCSC_zone

11ENon-SCSC_zone



25

20

15

10

5

0

Dep

th (c

m)

Figure 11 Change rule of the pile-side soil resistance withESCSC_zone


horizontal bearing capacity of the CCFSTP foundation withESCSC_zone

As shown in Figure 15 the ultimate horizontal bearingcapacity of the CCFSTP is higher than that of the ordinaryRCP and it increases as ESCSC_zone values increases eultimate horizontal bearing capacity of RCP (ESCSC_zone

10ENon-SCSC_zone) is 695N e ultimate horizontal bearingcapacity of the CCFSTP is 789N 810N 828N 836N and844N when the ESCSC_zone values is 11ENon-SCSC_zone12ENon-SCSC_zone 13ENon-SCSC_zone 14ENon-SCSC_zone and15ENon-SCSC_zone respectivelyWith the increase of modulusof soil mass in the steel casing soil compaction zone thehorizontal ultimate bearing capacity of CCFSTP increasesgradually when the length of steel casing is constant emain reason is that with the increase of modulus of soil massin the zone which is around CCFSTP the soil aroundCCFSTP is not easy to be compressed and the pile-side soilresistance increases It can be seen that the ultimate hori-zontal bearing capacity of the CCFSTP increased to a rel-atively large extent as ESCSC_zone values increased within a

range of 13ENon-SCSC_zone and that the ultimate horizontalbearing capacity of the CCFSTP continued to increase as theESCSC_zone values increased beyond 13ENon-SCSC_zone albeitto a relatively small extent When the ESCSC_zone value is11ENon-SCSC_zone the ultimate bearing capacity is increasedby 133 indicating that the increase of soil modulusaround the pile can improve the ultimate bearing capacityWhen the ESCSC_zone value is 14ENon-SCSC_zone the increaseof ultimate bearing capacity is 201 It is only 11 higherthan the ESCSC_zone value is 13ENon-SCSC_zone is is becausewhen the soil modulus around the pile exceeds a certainvalue the increase of the soil modulus around the pile haslittle effect on the horizontal bearing capacity

33 Bending Moment of the CCFSTP Figure 16 shows thechange rule of the bendingmoment of the CCFSTP with LSC

It can be seen from the Figure 16 that at the same depthwith the increase of steel casing length the maximumbending moment of CCFSTP increases gradually For boththe RCP and the CCFSTP with an LSC of 8 cm the bendingmoment first increased and then decreased along the lengthdirection as the depth increased In addition the bendingmoment started to sharply decrease at a certain depth and isnegative after reaching zero and it eventually became zerois indicates that when the steel casing length is 8 cm a pileundergoes inflection deformation along the length directionat a certain depth Moreover when the steel casing length isgreater than 12 cm the bendingmoment of the pile increasesfirst and then decreases along the length direction and thendecreases sharply at a certain depth but it does not becomenegative as the depth continues to increase As the steelcasing length increases the location of the cross-section of apile at which its maximum bending moment occurs movesdownward e main reason is similar to the analysis inSection 31 with the increase of the length of the steel casingthe extrusion area of the steel casing increases and the pile-side soil resistance increases In addition as the length of the

8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

00

02

04

06

08

10

12

Disp

lace

men

t (m

m)

(a)

8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)

Figure 12 Load-displacement curves and load-displacement gradient curves of the CCFSTP under various LSC values

HαH

0

5

10

15

20

25

30

α H (

)

50

60

70

80

90

100

H (N

)

0 205 1510LSC (cm)

Figure 13 Effects of LSC on the ultimate horizontal bearing ca-pacity of the CCFSTP


steel casing increases the stiffness of the CCFSTP increasesso the position where the maximum bending moment oc-curs moves down

Figure 17 shows the change rule of the maximumbending moment of the CCFSTP and the location of thecross-section of the CCFSTP at which its maximum bendingmoment occurred as LSC increased

As shown in Figure 17 the maximum bending momentof the CCFSTP increases as the steel casing length increasesemaximum bending moment of the CCFSTP is 247Nmiddotm271Nmiddotm 278Nmiddotm and 280Nmiddotm when the steel casinglength is 8 cm 12 cm 16 cm and 20 cm respectively whichare 165 278 3115 and 321 higher than that of theordinary RCP Evidently when the steel casing length is lessthan 12 cm the steel casing length relatively significantlyaffects the maximum bending moment of the CCFSTP theeffects of the steel casing length on the maximum bendingmoment of the CCFSTP decrease as the steel casing length

increases beyond 12 cm As the steel casing length increasesthe location of the cross-section of the CCFSTP at which itsmaximum bending moment occurs moves slowly down-ward is suggests that the location of the cross-section ofthe CCFSTP at which its maximum bending moment occursis insignificantly affected by the steel casing length after thesteel casing length reaches a certain value is is becausewhen the steel casing length exceeds a certain value theincrease of the steel casing length has little effect on themaximum bending moment of the CCFSTP

Figure 18 shows the change rule of the bending momentof the CCFSTP with the ESCSC_zone

Similar patterns can be observed in Figure 18 for thevariations in the bending moment of the CCFSTP and theordinary RCP along the length direction e bending

0 50 100 150 200

10ENon-SCSC_zone


11ENon-SCSC_zone


Load (N)

00

02

04

06

08

10

12D

ispla

cem

ent (

mm

)

(a)

10ENon-SCSC_zone


11ENon-SCSC_zone


0 50 100 150 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)

Figure 14 Load-displacement curves and load-displacement gradient curves of the CCFSTP under various ESCSC_zone values

HαH

1510 11 12 13 14ESCSC_zone (multiple of ENon-SCSC_zone)

50

60

70

80

90

100

H (N

)

0

5

10

15

20

25

30

α H (

)

Figure 15 Effects of ESCSC_zone on the ultimate horizontal bearingcapacity of the CCFSTP

8cm16cm

0cm12cm20cm

ndash5 0 5 10 15 20 25 30Bending moment of the pile (Nmiddotm)

30

25

20

15

10

5

0

Dep

th (c

m)

Figure 16 Change rule of the bending moment of the CCFSTPwith LSC


moment increases first then decreases and starts to decreasesharply at a certain depth it becomes negative after reachingzero and eventually decreases to zero e bending momentof the CCFSTP is greater than that of the ordinary RCP at thesame cross-section For the CCFSTP with the same length ofsteel casing its maximum bending moment gradually de-creased as modulus of soil mass in the steel casing soilcompaction zone increasede main reason is that with theincrease of modulus of soil mass in the zone the soil aroundCCFSTP is not easy to be compressed and the pile-side soilresistance increases Figure 19 shows the change rule of themaximum bending moment of the CCFSTP and the locationof the cross-section of the CCFSTP at which the maximumbending moment occurred with increasing ESCSC_zone

As ESCSC_zone values increases the maximum bendingmoment of the CCFSTP decreases but it remains greaterthan that of the ordinary RCP e maximum bending

moment of the CCFSTP is 247Nmiddotm 238Nmiddotm 230Nmiddotm222Nmiddotm and 216Nmiddotmwhen the modulus of soil mass in thesteel casing soil compaction zone is 11ENon-SCSC_zone12ENon-SCSC_zone 13ENon-SCSC_zone 14ENon-SCSC_zone and15ENon-SCSC_zone respectively which are 165 12385 47 and 19 higher than that of the ordinary RCPrespectively Moreover as ESCSC_zone increases the locationof the cross-section of the CCFSTP at which its maximumbending moment occurs moves upward However due tothe presence of the steel casing the location of the maximumbending moment remains below the location of the cross-section of the ordinary RCP at which its maximum bendingmoment occurs is suggests that changes in ESCSC_zonehave no significant effects on the location of the cross-section of the CCFSTP where its maximum bending mo-ment occurs is is mainly because when the modulus ofsoil mass in the steel casing soil compaction zone exceeds acertain value it is difficult for the soil around the CCFSTP tocontinue to be compressed and the increase of soil modulushas little effect on the maximum bending moment ofCCFSTP

34 Calculation of Optimal Reinforcement for CCFSTPs andIts Validation Based on an Engineering Structure e aboveanalysis shows that the bending resistance of the CCFSTP ishigher than that of the ordinary RCP However in pilefoundation design the effects of the steel casing on the pilebending resistance are not taken into consideration insteadthe steel casing is only considered as a safety margin whichis evidently unreasonable erefore it is necessary to an-alyze optimal reinforcement design for CCFSTPs

For an ordinary RCPmdasha circular eccentric compressionmember with uniform circumferential reinforcementmdashwhen the number of longitudinal reinforcement is no lessthan six the longitudinal reinforcement can be converted toan equivalent steel ring with a total area of 1113936

ni1Asi (Asi is the

cross-sectional area of a single longitudinal reinforcement

5

6

7

8

9

10

Maximum bending momentLocation of the cross-section for maximumbending moment

Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)

5 10 15 200hSC (cm)

15

20

25

30

35

Max

imum

ben

ding

mom

ent (

Nmiddotm

)

Figure 17 Change rule of the maximum bending moment of theCCFSTP and the location of the cross-section of the CCFSTP


30

25

20

15

10

5

0

Dep

th (c

m)

10ENon-SCSC_zone


11ENon-SCSC_zone


Figure 18 Change rule of the bending moment of the CCFSTPwith ESCSC_zone

10 11 12 13 14 1515

20

25

30

35

ESCSC_zone (multiple of ENon-SCSC_zone)


Max

imum

ben

ding

mom

ent (

Nmiddotm

)

5

6

7

8

9

10

Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)

Figure 19 Change rule of the maximum bending moment of theCCFSTP and the location of the cross-section of the CCFSTP atwhich the maximum bending moment occurred


and n is the number of longitudinal reinforcement) and aradius of rs [31]

Let us set r as the cross-sectional radius of a pilefoundation (ie the design radius) and rs as the distancebetween the centre of the wall thickness of the equivalentsteel ring and the centre of the cross-section (the same as thedistance between the centre of the longitudinal reinforce-ment and the centre of the cross-section) en thethickness ts1 of the steel ring equivalent to the longitudinalreinforcement is

ts1 1113936

ni1Asi

2πrs

1113936

ni1Asi

πr2middot

r

2αζr

2α (2)

where ζ is longitudinal reinforcement ratio (ζ 1113936ni1Asiπr2)

andα is ratio of the radius of the equivalent steel ring to thedesign radius of the pile foundation (α rsr)

Similar to the calculation of the bending resistance byconverting the longitudinal reinforcement to an equivalentsteel ring the steel casing in the CCFSTP can also beconverted to an equivalent steel ring with a radius of rs at thesame location as the longitudinal reinforcement based on theequivalence principle of cross-sectional bending resistanceIn this way the steel casing and the longitudinal rein-forcement can be both included in the calculation of thebending resistance of the pile foundation which will providea basis for optimal reinforcement design for CCFSTPsFigure 20 shows the method for converting the steel casingto an equivalent steel ring

Based on the principle that the cross-sectional bendingresistance of the steel casing equals that of the equivalentsteel ring we have

E1I1 E2I2 (3)

where E1 and E2 are elastic moduli of the steel casing and thelongitudinal reinforcement respectively (Pa) and I1 and I2are moments of inertia of the steel casing and the longi-tudinal reinforcement relative to the centre of the cross-section respectively (m4)

For each steel casing and the equivalent steel ring thewall thicknesses are far smaller than the distance between itscentre and the centre of the cross-section (ts≪ rprime ts2≪ rs)us

I1 πrprime3ts I2 πr

3s ts2 (4)

where rprime is distance between the centre of the wall thicknessof the steel casing and the centre of the cross-section (m) rs

is distance between the centre of the wall thickness ofthe equivalent steel ring and the centre of the cross-section(m) ts is wall thickness of the steel casing (m) and ts2 iswall thickness of the steel ring equivalent to the steel casing(m)

By substituting equation (4) into equation (3) we have

ts2 E1rprime

3

E2r3s

middot ts E1

E2αprime3 middot ts (5)

where αprime is ratio of the radius of the equivalent steel ring tothe radius of the steel casing (αprime rsrprime)

nprime As

Asi

2πrsts2

Asi

2E1rprime

3ts

E2r20r

2s

(6)

where nprime is the number of longitudinal reinforcementequivalent to the steel casing As is the cross-sectional area ofthe steel ring equivalent to the steel casing (m2) r0 is theradius of the longitudinal reinforcement (m) and theremaining parameters have the same meaning as previouslydescribed

As demonstrated in equation (6) in the bearing structuresystem of a CCFSTP a steel casing with an elastic modulus ofE1 a wall thickness of ts and a radius of rprime play the same roleas nprime number of longitudinal reinforcement with an elasticmodulus of E2 and a radius of r0 On this basis longitudinalreinforcement can be reasonably optimized for pilefoundations

35 A Case Study CCFSTPs are widely used as the bridgefoundations of Guangzhou-Jiangmen Expressway A casestudy is performed with the FY3-0 pile foundation of theFuzhouhe Bridge in the Jiangnan segment of the TJ05section of the Guangzhou-Jiangmen Expressway e FY3-0 CCFSTP contains longitudinal rebars of the same type anddiameter but with three different lengths along the length ofthe pile (see Table 7)

e CCFSTP remains in a water environment for anextended period of time and consequently its steel casing iscorroded to some extent erefore the effects of corrosionon the steel casing need to be considered According to theSpecification for Pile Foundations of Harbor Engineering[32] and Specification for Design of Highways ReinforcedConcrete and Prestressed Concrete Bridges and Culverts[33] a corrosion rate of 003mmyear can be used for steelstructures in river ports Based on a design service life of 100years a thickness of 3mm is included in the steel casing as asafety margin against corrosion us when calculating thehorizontal bending resistance of the pile foundation thecontribution of this 3mm thickness of the steel casing shouldbe deducted

Based on equation (6) the number of longitudinal rebarsequivalent to the steel casing in the pile foundation can becalculated By substituting E1 205times105MPaE2 2times105MPa rprime 09m rs 064m r0 00125m andts 0007m into equation (6) we obtain

nprime 2 times 205 times 105 times 093 times 00072 times 105 times 001252 times 0642

1635 (7)

Based on the above calculation the bending resistance ofthe FY3-0 CCFSTP provided by the built-in steel casing isequivalent to that provided by 163 longitudinal rebars with adiameter of 25mm is indicates that the steel casing canprovide sufficient bending resistance to the pile foundationerefore structural reinforcement should be designed forthe CCFSTP with a minimum reinforcement ratio of 05according to the Design Specification for Reinforced Con-crete for Highways and Prestressed Concrete Bridges andCulverts while ensuring that the steel casing has a sufficienteffective wall thickness [33]


e FY3-0 has a diameter D of 15m For a structuralreinforcement design based on a minimum reinforcementratio of 05 the number of the aforementioned longitu-dinal rebars required is

n AρAsi

πr2ρπr20

314 times 0752 times 0005

314 times 001252 18 (8)

Considering that the steel casing is mainly located in theupper section of the pile foundation a reinforcement op-timization principle that reduces the number of relativelyshort longitudinal rebars should be used Based on the actualreinforcement in the FY3-0 CCFSTP (Table 8) it is de-termined that only the No 3 rebars in the original designneed to be optimized Eventually 12 No 3 rebars are re-moved As a result rebars with a total length of 3149m havebeen saved

4 Conclusions

e ultimate horizontal bearing capacity of the CCFSTP isto some extent higher than that of an ordinary RCP elonger the steel casing the lower the maximum pile-side soilresistance As the modulus of soil mass in the steel casing soilcompaction zone increases the maximum pile-side soilresistance increases When the pile-side soil mass is

relatively soft increasing the steel casing length can com-pensate for the deficiency in the pile-side soil resistance emaximum bending moment of the CCFSTP is greater thanthat of an ordinary RCP e longer the steel casing thegreater the maximum bending moment of the CCFSTP andthe lower the location of the cross-section of the CCFSTP atwhich the maximum bending moment occurs e greaterthe ESCSC_zone value the smaller the maximum bendingmoment of the CCFSTP and the higher the location of thecross-section of the CCFSTP at which the maximumbending moment occurs

A longitudinal reinforcement optimization equation forCCFSTPs is obtained based on a theoretical derivationwhich provides theoretical guidance for the reasonable re-inforcement of pile foundations Due to the presence of asteel casing a CCFSTP has excessive bending resistance Tosave on the project investment optimal reinforcement couldbe designed by using the reinforcement optimizationequation for piles to reduce the number of longitudinal barsinside the pile while ensuring sufficient bending resistance ofthe pile

Data Availability

e data used to support the findings of this study are in-cluded within the article

Design pile diameterprofile

Steel casing

O

r

rprimets

(a)


Equivalentsteel ring

O

r

rsts2

(b)

Figure 20 (a) Placement of the steel casing (b) Equivalent steel ring

Table 7 Reinforcement parameters of the FY3-0 CCFSTP

Pile length (cm) Pile diameter (m) Number of rebars Number Diameter (mm) Length (cm) Number of rebars Total length (m)

6300 15 41 25 64197 7 44942 25 36243 8 28993 25 26243 15 3936

Table 8 Parameters used in the calculation of optimal reinforcement for the FY3-0 CCFSTP

Elastic modulus of thesteel casing E1(times105MPa)

Elastic modulus of therebars E2 (times105MPa)

Radius of thesteel casing rprime

(cm)

Effective wall thickness ofthe steel casing t (mm)

Radius of therebars r0 (mm)

Radius of theequivalent steel ring rs

(cm)205 2 90 7 125 64


Conflicts of Interest

e authors declare that there are no conflicts of interestsregarding the publication of this paper

Acknowledgments

e study was supported by the Key Transportation Scienceand Technology Program of Guangdong Province underGrant no 2011-01-001 e authors would also like to ex-press their great appreciation to Chenxin Xi for helping inthe development of the experiments and to Hangzhou Su forrefining and finalising the manuscript

References

[1] Z Feng H Hu Y Dong et al ldquoEffect of steel casing onvertical bearing characteristics of steel tube-reinforced con-crete piles in loess areardquo Applied Sciences vol 9 no 14p 2874 2019

[2] J X Lai H Q Liu J L Qiu and J X Chen ldquoSettlementanalysis of saturated tailings dam treated by CFG pile com-posite foundationrdquo Advances in Materials Science and En-gineering vol 10 2016

[3] J Lai H Liu J Qiu et al ldquoSettlement analysis of saturatedtailings dam treated by CFG pile composite foundationrdquoAdvances in Materials Science and Engineering vol 2016pp 1ndash10 2016

[4] Q-Q Zhang L-P Li and Y-J Chen ldquoAnalysis of com-pression pile response using a softening model a hyperbolicmodel of skin friction and a bilinear model of end resistancerdquoJournal of Engineering Mechanics vol 140 no 1 pp 102ndash1112014

[5] Q-Q Zhang S-W Liu S-M Zhang J Zhang and K WangldquoSimplified non-linear approaches for response of a single pileand pile groups considering progressive deformation of pile-soil systemrdquo Soils and Foundations vol 56 no 3 pp 473ndash484 2016

[6] Q-Q Zhang and Z-M Zhang ldquoA simplified nonlinear ap-proach for single pile settlement analysisrdquo Canadian Geo-technical Journal vol 49 no 11 pp 1256ndash1266 2012

[7] Y Dong Z Feng J He H Chen G Jiang and H YinldquoSeismic response of a bridge pile foundation during a shakingtable testrdquo Shock and Vibration vol 2019 Article ID 972601316 pages 2019

[8] J Wang W Li and Z Song ldquoDevelopment and imple-mentation of new triangular finite element based on MGEtheory for bi-material analysisrdquo Results in Physics vol 13Article ID 102231 2019

[9] X Tian Z Song and J Wang ldquoStudy on the propagation lawof tunnel blasting vibration in stratum and blasting vibrationreduction technologyrdquo Soil Dynamics and Earthquake Engi-neering vol 126 Article ID 105813 2019

[10] Z Feng H Hu R Zhao et al ldquoExperiments on reducingnegative skin friction of pilesrdquo Advances in Civil Engineeringvol 10 2019

[11] Ministry of Housing and Urban-Rural Development of thePeoplersquos Republic of China Technical Specification for Con-crete Filled Steel Tubular Structures (GB 50936-2014) ChinaArchitecture amp Building Press Beijing China 2014

[12] American Institute of Steel Construction (AISC) Specificationfor Structural Steel Buildings (ANSIAISC 360-16) American

Institute of Steel Construction (AISC) Chicago IL USA2016

[13] Architectural Institute of Japan (AIJ) Recommendations forDesign and Filled Steel Tubular Structures Architectural In-stitute of Japan Tokyo Japan 2008

[14] British Standards Institution Steel Concrete and CompositeBridges Part 5 Code of Practice for Design of CompositeBridges (BS5400-5) British Standards Institution LondonUK 2005

[15] British Standards Institution Design of Composite Steel andConcrete Structures (Eurocode 4) British Standards Institu-tion London UK 2007

[16] M Johansson and K Gylltoft ldquoMechanical behavior of cir-cular steel-concrete composite stub columnsrdquo Journal ofStructural Engineering vol 128 no 8 pp 1073ndash1081 2002

[17] F Trentadue G Quaranta and G C Marano ldquoClosed-formapproximations of interaction diagrams for assessment anddesign of reinforced concrete columns and concrete-filledsteel tubes with circular cross-sectionrdquo Engineering Struc-tures vol 127 pp 594ndash601 2016

[18] M Yousuf B Uy Z Tao A Remennikov and J Y R LiewldquoTransverse impact resistance of hollow and concrete filledstainless steel columnsrdquo Journal of Constructional Steel Re-search vol 82 no 82 pp 177ndash189 2013

[19] V I Patel Q Q Liang and M N S Hadi ldquoBiaxially loadedhigh-strength concrete-filled steel tubular slender beam-col-umns part II parametric studyrdquo Journal of ConstructionalSteel Research vol 110 no 75 pp 200ndash207 2015

[20] V I Patel Q Q Liang andM N S Hadi ldquoNonlinear analysisof axially loaded circular concrete-filled stainless steel tubularshort columnsrdquo Journal of Constructional Steel Researchvol 101 no 101 pp 9ndash18 2014

[21] N K Brown M J Kowalsky and J M Nau ldquoImpact of Dt onseismic behavior of reinforced concrete filled steel tubesrdquoJournal of Constructional Steel Research vol 107 pp 111ndash1232015

[22] D A Aguirre M J Kowalsky J M Nau M Gabr andG Lucier ldquoSeismic performance of reinforced concrete filledsteel tube drilled shafts with inground plastic hingesrdquo Engi-neering Structures vol 165 2018

[23] L A Montejo L A Gonzalez-Roman and M J KowalskyldquoSeismic performance evaluation of reinforced concrete-filledsteel tube pilecolumn bridge bentsrdquo Journal of EarthquakeEngineering vol 16 no 3 pp 401ndash424 2012

[24] E-b Jung S-H Lee J-H Yoo C Roeder and D LehmanldquoShear behavior of large-diameter concrete filled tube (CFT)rdquoInternational Journal of Steel Structures vol 17 no 4pp 1651ndash1665 2017

[25] G F Du M Babic F H Wu X Zeng and X M BieldquoExperimental and numerical studies on concrete filled cir-cular steel tubular (CFCST) members under impact loadsrdquoInternational Journal of Civil Engineering vol 3 pp 1ndash162018

[26] X Ding Y Fan P Li and G Kong ldquoVertical dynamic re-sponse of a concrete filled steel tube due to transient impactload analytical solutionrdquo International Journal of StructuralStability and Dynamics vol 16 no 1 Article ID 16400142016

[27] A-Z Zhu W Xu K Gao H-B Ge and J-H Zhu ldquoLateralimpact response of rectangular hollow and partially concrete-filled steel tubular columnsrdquoKin-Walled Structures vol 130pp 114ndash131 2018

[28] C Wang X Liu and P Li ldquoExperimental behavior of con-crete-filled steel tubular members subjected to lateral loadsrdquo


Advances in Materials Science and Engineering vol 2018Article ID 9065378 15 pages 2018

[29] National Energy Administration Specification for Geotech-nical Centrifuge Model Test Techniques (DLT 5102-2013)China Electric Power Press Beijing China 2013

[30] X N GongHandbook for Pile Foundation Engineering ChinaArchitecture amp Building Press Beijing China 2016

[31] Z Fang ldquoStrength and deformation of R C eccentricallycompressive members with circular sectionrdquo China Journal ofHighway amp Transport vol 7 no 1 pp 55ndash58 1994

[32] Ministry of Transport of the Peoplersquos Republic of ChinaSpecification for Pile Foundations of Harbor Engineering (JTS167-4-2012) China Communications Press Beijing China2012

[33] Ministry of Transport of the Peoplersquos Republic of ChinaSpecification for Design of Highways Reinforced Concrete andPrestressed Concrete Bridges and Culverts (JTG D62-2012)China Communications Press Beijing China 2012


International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

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VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

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Journal of

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Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

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Control Scienceand Engineering

Journal of



Journal ofEngineeringVolume 2018

SensorsJournal of



RotatingMachinery


Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation


Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

design methods for composite columns is specificationconsiders the overall stability of members under axialcompression by treating CFST members as pure steelmembers and incorporating the strength of the concrete intothat of the steel [12] e Architectural Institute of Japanrsquosconcrete-filled steel tube (CFST) specification considers theconfining effects of the steel tube on the core concrete whencalculating the bearing capacity of a circular CFSTmember[13] e British Standards Institutersquos Steel Concrete andComposite Bridge Specification for design of concretebridges states that the core concrete is three-way compressedunder the constraint of a steel pipe and the strength is in-creased when calculating the bearing capacity of a circularCFSTmember [14] European Standardization CommitteersquosEurocode 4 Design of steel and for buildings pointed out thatthe design of the steel concrete composite structure issuperimposed on the full plastic section and then thebearing capacity is corrected by comparison and analysis ofthe test [15] Johansson et al [16] studied the mechanicalbehaviors of 13 CFST column specimens under three dif-ferent loading conditions through a static test and found thatthe bond strength greatly affected the confinement effectswhen the load was applied only to the concrete part and thusaffects mechanical properties of the columns Trentadueet al [17] proposes closed-form approximations of the axialforce-bending moment interaction diagrams for reinforcedconcrete columns and concrete-filled steel tubes with cir-cular cross-section Yousuf et al [18] studied the behavior ofhollow and concrete-filled stainless steel tubular columnsunder static and impact loading Patel et al [19 20] de-scribed verification and applications of a multiscale modelfor CFST columns Brown et al [21] Aguirre et al [22] andMontejo et al [23] studied the nonlinear seismic behavior ofreinforced concrete-filled steel tubes Jung et al [24] im-proved shear design equations through further experimentaland analytical research on shear resistance and behavior ofcircular CFT Du et al [25] and Ding et al [26] investigatedthe failure modes the impact force time history curves andthe strain time history curves to evaluate the behavior of theCFCST member under an impact load Zhu et al [27] andWang et al [28] studied the factors influencing the bearingcapacity of concrete-filled steel tube columns All of the

aforementioned studies focus on the mechanical propertiesand bearing capacity of composite steel tube-concretestructures However there is a lack of research on thehorizontal bearing capacity of CCFSTPs when they interactwith the surrounding rock and soil mass e functionaldifference between bridge pile foundations and CFST col-umns results in a difference in the horizontal bearing ca-pacity between CCFSTPs and CFST columns erefore itis necessary to study the horizontal bearing capacity ofCCFSTPs

In this study based on the centrifugal model test thehorizontal bearing capacity of a CCFSTP affected by thelength of the steel casing (LSC) and the elastic modulus of thesoil mass in the steel-casing soil compaction (SCSC) zone(ESCSC_zone) are examined e load transfer mechanism forthe CCFSTP under horizontal loading is analyzed with theaim of providing a technical basis for the design and con-struction of bridge pile foundations

2 Experimental Investigation

In order to study the horizontal bearing capacity of the pilesa series of centrifugal model tests were carried out to analyzethe effect of steel casing and soil modulus in the steel casingsoil compaction zone on the bearing capacity of the piles

21 Physical Model In order to study the difference inhorizontal bearing capacity between composite concrete-filled steel tube piles (CCFSTPs) and ordinary reinforcedconcrete pile (RCP) 4 model CCFSTPs and 1 model RCPwere designed as shown in Table 1 and Figure 2 taking intoaccount the influence of steel casing length e piles arefriction piles

e ground in the model is composed of 40 cm thicknoncollapsible loess In practice the steel casing has acompaction effect on the soil around the pile To truly reflectthe mechanical conditions of the original CCFSTP the soilcompaction effects of the steel casing on the horizontalbearing capacity of the CCFSTP were simulated in the modeltest by altering ESCSC_zone (the SCSC zone is a zone with athickness of 15mm around the steel casing where 15mm is

A

A-A

(a) (b) (c)

B-B

C-C

D-D

A B B C C

D D

Figure 1 Composition of CCFSTP (a) Steel casing (SC) (b) Reinforced concrete pile (RCP) (c) Composite concrete-filled steel tube pile(CCFSTP)





n4EmIm EpIp

n4Emπ D4m minus d4

m1113872 1113873

64

EpπD4p

64 (1)








20cm 16cm 12cm 8cm

(a)

0cm

(b)








SCSC zone

Steel casing


Model pile

53

44

44

4 35

1310

(a)


(b)




CCFSTPs








100 350 35 25 25 2 02 402




100

20 20

30 3 2 02 16416 1612 128 8









Cohesionc (kPa)


Loess 17 198 135 27 21


Channel

Container

Balancing container

Arm

Base

(a)

Operating cabinet


(b)


(a) (b) (c)
















Model pile

75

84

times 3

= 12

5 times

4 =

20

35

25

75

8

(a)


(b)


(c)






A A

B

B

(a)

25cm 20cm 25cm

10cm

35cm

5cm

(b)10

cm35

cm5c

m

18cm 18cm

(c)




and compact it


into the hole


frame














8cm16cm

0cm12cm20cm

25

20

15

10

5

0

Dep

th (c

m)



10ENon-SCSC_zone


11ENon-SCSC_zone



25

20

15

10

5

0

Dep

th (c

m)









8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

00

02

04

06

08

10

12

Disp

lace

men

t (m

m)

(a)

8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH

0

5

10

15

20

25

30

α H (

)

50

60

70

80

90

100

H (N

)

0 205 1510LSC (cm)









0 50 100 150 200

10ENon-SCSC_zone


11ENon-SCSC_zone


Load (N)

00

02

04

06

08

10

12D

ispla

cem

ent (

mm

)

(a)

10ENon-SCSC_zone


11ENon-SCSC_zone


0 50 100 150 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH


50

60

70

80

90

100

H (N

)

0

5

10

15

20

25

30

α H (

)


8cm16cm

0cm12cm20cm


30

25

20

15

10

5

0

Dep

th (c

m)








ni1Asi (Asi is the


5

6

7

8

9

10


Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)

5 10 15 200hSC (cm)

15

20

25

30

35

Max

imum

ben

ding

mom

ent (

Nmiddotm

)



30

25

20

15

10

5

0

Dep

th (c

m)

10ENon-SCSC_zone


11ENon-SCSC_zone



10 11 12 13 14 1515

20

25

30

35



Max

imum

ben

ding

mom

ent (

Nmiddotm

)

5

6

7

8

9

10

Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)





ts1 1113936

ni1Asi

2πrs

1113936

ni1Asi

πr2middot

r

2αζr

2α (2)





E1I1 E2I2 (3)




3s ts2 (4)




ts2 E1rprime

3

E2r3s

middot ts E1



nprime As

Asi

2πrsts2

Asi

2E1rprime

3ts

E2r20r

2s

(6)







1635 (7)




n AρAsi

πr2ρπr20


314 times 001252 18 (8)


4 Conclusions




Data Availability



Steel casing

O

r

rprimets

(a)



O

r

rsts2

(b)




6300 15 41 25 64197 7 44942 25 36243 8 28993 25 26243 15 3936





(cm)




(cm)205 2 90 7 125 64




Acknowledgments


References








































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia





n4EmIm EpIp

n4Emπ D4m minus d4

m1113872 1113873

64

EpπD4p

64 (1)








20cm 16cm 12cm 8cm

(a)

0cm

(b)








SCSC zone

Steel casing


Model pile

53

44

44

4 35

1310

(a)


(b)




CCFSTPs








100 350 35 25 25 2 02 402




100

20 20

30 3 2 02 16416 1612 128 8









Cohesionc (kPa)


Loess 17 198 135 27 21


Channel

Container

Balancing container

Arm

Base

(a)

Operating cabinet


(b)


(a) (b) (c)
















Model pile

75

84

times 3

= 12

5 times

4 =

20

35

25

75

8

(a)


(b)


(c)






A A

B

B

(a)

25cm 20cm 25cm

10cm

35cm

5cm

(b)10

cm35

cm5c

m

18cm 18cm

(c)




and compact it


into the hole


frame














8cm16cm

0cm12cm20cm

25

20

15

10

5

0

Dep

th (c

m)



10ENon-SCSC_zone


11ENon-SCSC_zone



25

20

15

10

5

0

Dep

th (c

m)









8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

00

02

04

06

08

10

12

Disp

lace

men

t (m

m)

(a)

8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH

0

5

10

15

20

25

30

α H (

)

50

60

70

80

90

100

H (N

)

0 205 1510LSC (cm)









0 50 100 150 200

10ENon-SCSC_zone


11ENon-SCSC_zone


Load (N)

00

02

04

06

08

10

12D

ispla

cem

ent (

mm

)

(a)

10ENon-SCSC_zone


11ENon-SCSC_zone


0 50 100 150 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH


50

60

70

80

90

100

H (N

)

0

5

10

15

20

25

30

α H (

)


8cm16cm

0cm12cm20cm


30

25

20

15

10

5

0

Dep

th (c

m)








ni1Asi (Asi is the


5

6

7

8

9

10


Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)

5 10 15 200hSC (cm)

15

20

25

30

35

Max

imum

ben

ding

mom

ent (

Nmiddotm

)



30

25

20

15

10

5

0

Dep

th (c

m)

10ENon-SCSC_zone


11ENon-SCSC_zone



10 11 12 13 14 1515

20

25

30

35



Max

imum

ben

ding

mom

ent (

Nmiddotm

)

5

6

7

8

9

10

Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)





ts1 1113936

ni1Asi

2πrs

1113936

ni1Asi

πr2middot

r

2αζr

2α (2)





E1I1 E2I2 (3)




3s ts2 (4)




ts2 E1rprime

3

E2r3s

middot ts E1



nprime As

Asi

2πrsts2

Asi

2E1rprime

3ts

E2r20r

2s

(6)







1635 (7)




n AρAsi

πr2ρπr20


314 times 001252 18 (8)


4 Conclusions




Data Availability



Steel casing

O

r

rprimets

(a)



O

r

rsts2

(b)




6300 15 41 25 64197 7 44942 25 36243 8 28993 25 26243 15 3936





(cm)




(cm)205 2 90 7 125 64




Acknowledgments


References








































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia







SCSC zone

Steel casing


Model pile

53

44

44

4 35

1310

(a)


(b)




CCFSTPs








100 350 35 25 25 2 02 402




100

20 20

30 3 2 02 16416 1612 128 8









Cohesionc (kPa)


Loess 17 198 135 27 21


Channel

Container

Balancing container

Arm

Base

(a)

Operating cabinet


(b)


(a) (b) (c)
















Model pile

75

84

times 3

= 12

5 times

4 =

20

35

25

75

8

(a)


(b)


(c)






A A

B

B

(a)

25cm 20cm 25cm

10cm

35cm

5cm

(b)10

cm35

cm5c

m

18cm 18cm

(c)




and compact it


into the hole


frame














8cm16cm

0cm12cm20cm

25

20

15

10

5

0

Dep

th (c

m)



10ENon-SCSC_zone


11ENon-SCSC_zone



25

20

15

10

5

0

Dep

th (c

m)









8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

00

02

04

06

08

10

12

Disp

lace

men

t (m

m)

(a)

8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH

0

5

10

15

20

25

30

α H (

)

50

60

70

80

90

100

H (N

)

0 205 1510LSC (cm)









0 50 100 150 200

10ENon-SCSC_zone


11ENon-SCSC_zone


Load (N)

00

02

04

06

08

10

12D

ispla

cem

ent (

mm

)

(a)

10ENon-SCSC_zone


11ENon-SCSC_zone


0 50 100 150 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH


50

60

70

80

90

100

H (N

)

0

5

10

15

20

25

30

α H (

)


8cm16cm

0cm12cm20cm


30

25

20

15

10

5

0

Dep

th (c

m)








ni1Asi (Asi is the


5

6

7

8

9

10


Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)

5 10 15 200hSC (cm)

15

20

25

30

35

Max

imum

ben

ding

mom

ent (

Nmiddotm

)



30

25

20

15

10

5

0

Dep

th (c

m)

10ENon-SCSC_zone


11ENon-SCSC_zone



10 11 12 13 14 1515

20

25

30

35



Max

imum

ben

ding

mom

ent (

Nmiddotm

)

5

6

7

8

9

10

Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)





ts1 1113936

ni1Asi

2πrs

1113936

ni1Asi

πr2middot

r

2αζr

2α (2)





E1I1 E2I2 (3)




3s ts2 (4)




ts2 E1rprime

3

E2r3s

middot ts E1



nprime As

Asi

2πrsts2

Asi

2E1rprime

3ts

E2r20r

2s

(6)







1635 (7)




n AρAsi

πr2ρπr20


314 times 001252 18 (8)


4 Conclusions




Data Availability



Steel casing

O

r

rprimets

(a)



O

r

rsts2

(b)




6300 15 41 25 64197 7 44942 25 36243 8 28993 25 26243 15 3936





(cm)




(cm)205 2 90 7 125 64




Acknowledgments


References








































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia









Cohesionc (kPa)


Loess 17 198 135 27 21


Channel

Container

Balancing container

Arm

Base

(a)

Operating cabinet


(b)


(a) (b) (c)
















Model pile

75

84

times 3

= 12

5 times

4 =

20

35

25

75

8

(a)


(b)


(c)






A A

B

B

(a)

25cm 20cm 25cm

10cm

35cm

5cm

(b)10

cm35

cm5c

m

18cm 18cm

(c)




and compact it


into the hole


frame














8cm16cm

0cm12cm20cm

25

20

15

10

5

0

Dep

th (c

m)



10ENon-SCSC_zone


11ENon-SCSC_zone



25

20

15

10

5

0

Dep

th (c

m)









8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

00

02

04

06

08

10

12

Disp

lace

men

t (m

m)

(a)

8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH

0

5

10

15

20

25

30

α H (

)

50

60

70

80

90

100

H (N

)

0 205 1510LSC (cm)









0 50 100 150 200

10ENon-SCSC_zone


11ENon-SCSC_zone


Load (N)

00

02

04

06

08

10

12D

ispla

cem

ent (

mm

)

(a)

10ENon-SCSC_zone


11ENon-SCSC_zone


0 50 100 150 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH


50

60

70

80

90

100

H (N

)

0

5

10

15

20

25

30

α H (

)


8cm16cm

0cm12cm20cm


30

25

20

15

10

5

0

Dep

th (c

m)








ni1Asi (Asi is the


5

6

7

8

9

10


Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)

5 10 15 200hSC (cm)

15

20

25

30

35

Max

imum

ben

ding

mom

ent (

Nmiddotm

)



30

25

20

15

10

5

0

Dep

th (c

m)

10ENon-SCSC_zone


11ENon-SCSC_zone



10 11 12 13 14 1515

20

25

30

35



Max

imum

ben

ding

mom

ent (

Nmiddotm

)

5

6

7

8

9

10

Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)





ts1 1113936

ni1Asi

2πrs

1113936

ni1Asi

πr2middot

r

2αζr

2α (2)





E1I1 E2I2 (3)




3s ts2 (4)




ts2 E1rprime

3

E2r3s

middot ts E1



nprime As

Asi

2πrsts2

Asi

2E1rprime

3ts

E2r20r

2s

(6)







1635 (7)




n AρAsi

πr2ρπr20


314 times 001252 18 (8)


4 Conclusions




Data Availability



Steel casing

O

r

rprimets

(a)



O

r

rsts2

(b)




6300 15 41 25 64197 7 44942 25 36243 8 28993 25 26243 15 3936





(cm)




(cm)205 2 90 7 125 64




Acknowledgments


References








































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia











Model pile

75

84

times 3

= 12

5 times

4 =

20

35

25

75

8

(a)


(b)


(c)






A A

B

B

(a)

25cm 20cm 25cm

10cm

35cm

5cm

(b)10

cm35

cm5c

m

18cm 18cm

(c)




and compact it


into the hole


frame














8cm16cm

0cm12cm20cm

25

20

15

10

5

0

Dep

th (c

m)



10ENon-SCSC_zone


11ENon-SCSC_zone



25

20

15

10

5

0

Dep

th (c

m)









8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

00

02

04

06

08

10

12

Disp

lace

men

t (m

m)

(a)

8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH

0

5

10

15

20

25

30

α H (

)

50

60

70

80

90

100

H (N

)

0 205 1510LSC (cm)









0 50 100 150 200

10ENon-SCSC_zone


11ENon-SCSC_zone


Load (N)

00

02

04

06

08

10

12D

ispla

cem

ent (

mm

)

(a)

10ENon-SCSC_zone


11ENon-SCSC_zone


0 50 100 150 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH


50

60

70

80

90

100

H (N

)

0

5

10

15

20

25

30

α H (

)


8cm16cm

0cm12cm20cm


30

25

20

15

10

5

0

Dep

th (c

m)








ni1Asi (Asi is the


5

6

7

8

9

10


Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)

5 10 15 200hSC (cm)

15

20

25

30

35

Max

imum

ben

ding

mom

ent (

Nmiddotm

)



30

25

20

15

10

5

0

Dep

th (c

m)

10ENon-SCSC_zone


11ENon-SCSC_zone



10 11 12 13 14 1515

20

25

30

35



Max

imum

ben

ding

mom

ent (

Nmiddotm

)

5

6

7

8

9

10

Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)





ts1 1113936

ni1Asi

2πrs

1113936

ni1Asi

πr2middot

r

2αζr

2α (2)





E1I1 E2I2 (3)




3s ts2 (4)




ts2 E1rprime

3

E2r3s

middot ts E1



nprime As

Asi

2πrsts2

Asi

2E1rprime

3ts

E2r20r

2s

(6)







1635 (7)




n AρAsi

πr2ρπr20


314 times 001252 18 (8)


4 Conclusions




Data Availability



Steel casing

O

r

rprimets

(a)



O

r

rsts2

(b)




6300 15 41 25 64197 7 44942 25 36243 8 28993 25 26243 15 3936





(cm)




(cm)205 2 90 7 125 64




Acknowledgments


References








































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia





A A

B

B

(a)

25cm 20cm 25cm

10cm

35cm

5cm

(b)10

cm35

cm5c

m

18cm 18cm

(c)




and compact it


into the hole


frame














8cm16cm

0cm12cm20cm

25

20

15

10

5

0

Dep

th (c

m)



10ENon-SCSC_zone


11ENon-SCSC_zone



25

20

15

10

5

0

Dep

th (c

m)









8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

00

02

04

06

08

10

12

Disp

lace

men

t (m

m)

(a)

8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH

0

5

10

15

20

25

30

α H (

)

50

60

70

80

90

100

H (N

)

0 205 1510LSC (cm)









0 50 100 150 200

10ENon-SCSC_zone


11ENon-SCSC_zone


Load (N)

00

02

04

06

08

10

12D

ispla

cem

ent (

mm

)

(a)

10ENon-SCSC_zone


11ENon-SCSC_zone


0 50 100 150 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH


50

60

70

80

90

100

H (N

)

0

5

10

15

20

25

30

α H (

)


8cm16cm

0cm12cm20cm


30

25

20

15

10

5

0

Dep

th (c

m)








ni1Asi (Asi is the


5

6

7

8

9

10


Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)

5 10 15 200hSC (cm)

15

20

25

30

35

Max

imum

ben

ding

mom

ent (

Nmiddotm

)



30

25

20

15

10

5

0

Dep

th (c

m)

10ENon-SCSC_zone


11ENon-SCSC_zone



10 11 12 13 14 1515

20

25

30

35



Max

imum

ben

ding

mom

ent (

Nmiddotm

)

5

6

7

8

9

10

Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)





ts1 1113936

ni1Asi

2πrs

1113936

ni1Asi

πr2middot

r

2αζr

2α (2)





E1I1 E2I2 (3)




3s ts2 (4)




ts2 E1rprime

3

E2r3s

middot ts E1



nprime As

Asi

2πrsts2

Asi

2E1rprime

3ts

E2r20r

2s

(6)







1635 (7)




n AρAsi

πr2ρπr20


314 times 001252 18 (8)


4 Conclusions




Data Availability



Steel casing

O

r

rprimets

(a)



O

r

rsts2

(b)




6300 15 41 25 64197 7 44942 25 36243 8 28993 25 26243 15 3936





(cm)




(cm)205 2 90 7 125 64




Acknowledgments


References








































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia









8cm16cm

0cm12cm20cm

25

20

15

10

5

0

Dep

th (c

m)



10ENon-SCSC_zone


11ENon-SCSC_zone



25

20

15

10

5

0

Dep

th (c

m)









8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

00

02

04

06

08

10

12

Disp

lace

men

t (m

m)

(a)

8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH

0

5

10

15

20

25

30

α H (

)

50

60

70

80

90

100

H (N

)

0 205 1510LSC (cm)









0 50 100 150 200

10ENon-SCSC_zone


11ENon-SCSC_zone


Load (N)

00

02

04

06

08

10

12D

ispla

cem

ent (

mm

)

(a)

10ENon-SCSC_zone


11ENon-SCSC_zone


0 50 100 150 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH


50

60

70

80

90

100

H (N

)

0

5

10

15

20

25

30

α H (

)


8cm16cm

0cm12cm20cm


30

25

20

15

10

5

0

Dep

th (c

m)








ni1Asi (Asi is the


5

6

7

8

9

10


Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)

5 10 15 200hSC (cm)

15

20

25

30

35

Max

imum

ben

ding

mom

ent (

Nmiddotm

)



30

25

20

15

10

5

0

Dep

th (c

m)

10ENon-SCSC_zone


11ENon-SCSC_zone



10 11 12 13 14 1515

20

25

30

35



Max

imum

ben

ding

mom

ent (

Nmiddotm

)

5

6

7

8

9

10

Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)





ts1 1113936

ni1Asi

2πrs

1113936

ni1Asi

πr2middot

r

2αζr

2α (2)





E1I1 E2I2 (3)




3s ts2 (4)




ts2 E1rprime

3

E2r3s

middot ts E1



nprime As

Asi

2πrsts2

Asi

2E1rprime

3ts

E2r20r

2s

(6)







1635 (7)




n AρAsi

πr2ρπr20


314 times 001252 18 (8)


4 Conclusions




Data Availability



Steel casing

O

r

rprimets

(a)



O

r

rsts2

(b)




6300 15 41 25 64197 7 44942 25 36243 8 28993 25 26243 15 3936





(cm)




(cm)205 2 90 7 125 64




Acknowledgments


References








































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia








8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

00

02

04

06

08

10

12

Disp

lace

men

t (m

m)

(a)

8cm16cm

0cm12cm20cm

50 100 1500 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH

0

5

10

15

20

25

30

α H (

)

50

60

70

80

90

100

H (N

)

0 205 1510LSC (cm)









0 50 100 150 200

10ENon-SCSC_zone


11ENon-SCSC_zone


Load (N)

00

02

04

06

08

10

12D

ispla

cem

ent (

mm

)

(a)

10ENon-SCSC_zone


11ENon-SCSC_zone


0 50 100 150 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH


50

60

70

80

90

100

H (N

)

0

5

10

15

20

25

30

α H (

)


8cm16cm

0cm12cm20cm


30

25

20

15

10

5

0

Dep

th (c

m)








ni1Asi (Asi is the


5

6

7

8

9

10


Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)

5 10 15 200hSC (cm)

15

20

25

30

35

Max

imum

ben

ding

mom

ent (

Nmiddotm

)



30

25

20

15

10

5

0

Dep

th (c

m)

10ENon-SCSC_zone


11ENon-SCSC_zone



10 11 12 13 14 1515

20

25

30

35



Max

imum

ben

ding

mom

ent (

Nmiddotm

)

5

6

7

8

9

10

Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)





ts1 1113936

ni1Asi

2πrs

1113936

ni1Asi

πr2middot

r

2αζr

2α (2)





E1I1 E2I2 (3)




3s ts2 (4)




ts2 E1rprime

3

E2r3s

middot ts E1



nprime As

Asi

2πrsts2

Asi

2E1rprime

3ts

E2r20r

2s

(6)







1635 (7)




n AρAsi

πr2ρπr20


314 times 001252 18 (8)


4 Conclusions




Data Availability



Steel casing

O

r

rprimets

(a)



O

r

rsts2

(b)




6300 15 41 25 64197 7 44942 25 36243 8 28993 25 26243 15 3936





(cm)




(cm)205 2 90 7 125 64




Acknowledgments


References








































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia








0 50 100 150 200

10ENon-SCSC_zone


11ENon-SCSC_zone


Load (N)

00

02

04

06

08

10

12D

ispla

cem

ent (

mm

)

(a)

10ENon-SCSC_zone


11ENon-SCSC_zone


0 50 100 150 200Load (N)

0000

0002

0004

0006

0008

0010

0012

Disp

lace

men

t gra

dien

t (m

mN

)

(b)


HαH


50

60

70

80

90

100

H (N

)

0

5

10

15

20

25

30

α H (

)


8cm16cm

0cm12cm20cm


30

25

20

15

10

5

0

Dep

th (c

m)








ni1Asi (Asi is the


5

6

7

8

9

10


Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)

5 10 15 200hSC (cm)

15

20

25

30

35

Max

imum

ben

ding

mom

ent (

Nmiddotm

)



30

25

20

15

10

5

0

Dep

th (c

m)

10ENon-SCSC_zone


11ENon-SCSC_zone



10 11 12 13 14 1515

20

25

30

35



Max

imum

ben

ding

mom

ent (

Nmiddotm

)

5

6

7

8

9

10

Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)





ts1 1113936

ni1Asi

2πrs

1113936

ni1Asi

πr2middot

r

2αζr

2α (2)





E1I1 E2I2 (3)




3s ts2 (4)




ts2 E1rprime

3

E2r3s

middot ts E1



nprime As

Asi

2πrsts2

Asi

2E1rprime

3ts

E2r20r

2s

(6)







1635 (7)




n AρAsi

πr2ρπr20


314 times 001252 18 (8)


4 Conclusions




Data Availability



Steel casing

O

r

rprimets

(a)



O

r

rsts2

(b)




6300 15 41 25 64197 7 44942 25 36243 8 28993 25 26243 15 3936





(cm)




(cm)205 2 90 7 125 64




Acknowledgments


References








































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia







ni1Asi (Asi is the


5

6

7

8

9

10


Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)

5 10 15 200hSC (cm)

15

20

25

30

35

Max

imum

ben

ding

mom

ent (

Nmiddotm

)



30

25

20

15

10

5

0

Dep

th (c

m)

10ENon-SCSC_zone


11ENon-SCSC_zone



10 11 12 13 14 1515

20

25

30

35



Max

imum

ben

ding

mom

ent (

Nmiddotm

)

5

6

7

8

9

10

Loca

tion

of th

e cro

ss-s

ectio

n fo

rm

axim

um b

endi

ng m

omen

t (cm

)





ts1 1113936

ni1Asi

2πrs

1113936

ni1Asi

πr2middot

r

2αζr

2α (2)





E1I1 E2I2 (3)




3s ts2 (4)




ts2 E1rprime

3

E2r3s

middot ts E1



nprime As

Asi

2πrsts2

Asi

2E1rprime

3ts

E2r20r

2s

(6)







1635 (7)




n AρAsi

πr2ρπr20


314 times 001252 18 (8)


4 Conclusions




Data Availability



Steel casing

O

r

rprimets

(a)



O

r

rsts2

(b)




6300 15 41 25 64197 7 44942 25 36243 8 28993 25 26243 15 3936





(cm)




(cm)205 2 90 7 125 64




Acknowledgments


References








































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




ts1 1113936

ni1Asi

2πrs

1113936

ni1Asi

πr2middot

r

2αζr

2α (2)





E1I1 E2I2 (3)




3s ts2 (4)




ts2 E1rprime

3

E2r3s

middot ts E1



nprime As

Asi

2πrsts2

Asi

2E1rprime

3ts

E2r20r

2s

(6)







1635 (7)




n AρAsi

πr2ρπr20


314 times 001252 18 (8)


4 Conclusions




Data Availability



Steel casing

O

r

rprimets

(a)



O

r

rsts2

(b)




6300 15 41 25 64197 7 44942 25 36243 8 28993 25 26243 15 3936





(cm)




(cm)205 2 90 7 125 64




Acknowledgments


References








































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



n AρAsi

πr2ρπr20


314 times 001252 18 (8)


4 Conclusions




Data Availability



Steel casing

O

r

rprimets

(a)



O

r

rsts2

(b)




6300 15 41 25 64197 7 44942 25 36243 8 28993 25 26243 15 3936





(cm)




(cm)205 2 90 7 125 64




Acknowledgments


References








































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




Acknowledgments


References








































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia











RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia


Documents

The Horizontal Bearing Capacity of Composite Concrete ...horizontal bearing capacity of CCFSTPs when they interact with the surrounding rock and soil mass. e functional diﬀerence