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Introduction Tasks achieved in GP I Earthquake load Alternative # 2 Design of compression & zero force members Design of tension members Design of end beams & columns Design of welded connection Design of bolted connection Material cost Comparison and final design Conclusion
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Outline
Introduction
Currently, Al Ain International Airport is under extension work due to:
o Growth in the passenger flightso Increase in the airline traffic to Al Ain
Our graduation project was motivated by the ongoing expansion of Al Ain International Airport.
The roofing system of a typical airport’s terminal was selected, analyzed and then designed.
The major objective was to utilize the theory of structures
principals and the Load and Resistance Factor Design
concepts to;
o Model
o Analyze
o Design
the steel elements and connections forming the main
supporting element of the long-span roofing system.
Objective
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Comprehensive literature review was conducted on common
construction material, structural systems, and dimensions of existing or
proposed airport terminals.
Two alternative architectural designs were selected.
A general structural layout was generated using the AutoCAD software to
describe all the components of the first alternative system.
GP I Summary
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The initial computer model was developed for the first alternative
system using the structural analysis software SAP2000.
The various design loads acting on the first alternative system including
dead loads, roof live loads and wind loads were calculated based on the
latest American standards developed by the American Society of Civil
Engineers (ASCE7-05).
A detailed 3D model was developed using SAP2000 to simulate the
behavior and response of the selected structural system under the
computed loads.
GP I Summary
First Alternative: Multi-Curvature Arch
Generation of the Alternatives
Second Alternative: Traditional Single-Curvature Arch
Generation of the Alternatives
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An earthquake is a shake of the earth's
surface usually occurred by the release of
underground stress along fault lines. This
release causes movement in masses of
rock and resulting seismic waves.
Earthquake Load
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Severe Lateral load
Very complex & uncertain
Potentially more damaging than wind loads
Earthquake Load
Earthquake Load
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Designing buildings to resist earthquakes
requires that ground motions be translated
into forces acting upon a building.
Earthquake forces are called lateral forces.
The magnitude of earthquake load depends
on the mass of the structure and on the
horizontal acceleration imparted from the
ground shaking.
Earthquake Load
Earthquake Load
Case # 1
Case # 2
Earthquake Load Calculations
The procedure of calculating the earthquake load acting on the building structure is in
accordance with ASCE7-05/IBC 2009 standards .
o Required values, factors and coefficients :
W (KN) Ss R I Fa Fv S1 Ct x H (m) T
560.574 0.675 3.25 1.25 1.13 1.53 0.27 0.0488 0.75 30 0.626
Ta
T
analysis
k SMS SM1 SD1 SDs CsCs
[min]
Cs [max] Vb (KN)
0.892 2.5 1.063 0.7628 0.4131 0.2754 0.5085 0.1956 0.01 0.1692 94.853
Earthquake Load Calculations
Ss Values:
Abu Dhabi = 0.6
Dubai = 0.83
Al Ain = 0.675
Seismic activity in UAE (MCE)
Abu Dhabi
Dubai
Al Ain
Abu Dhabi
Dubai
Al Ain
S1Values:
Abu Dhabi = 0.24
Dubai = 0.33
Al Ain = 0.27
Seismic activity in UAE (MCE)
Long - Period Transition Period :
TL = 8
Seismic activity in UAE
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Earthquake Load Calculations
Base Shear (Vb) ; the total lateral load caused by the earthquake at the base of the structure.
Vb = Cs W
WhereVb ; the seismic base shear.
W ; the effective seismic weight “the total dead load of the entire building”.
Cs ; the seismic response coefficient
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Earthquake Load Calculations
The lateral seismic force (Fxf) ;
Fxf = Cvfx V b
The calculated base shear is distributed among all floors with respect to:o the heights of the building o their effective weight
Vertical distribution factor (Cvxf ) ;
Cvfx=( Wxf hxf k / Σi=1 n Wi hi k )(Ct hn x)
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Joint W (KN) h (m) hk Whk Cvfx= Fxf FINAL Fxf
46 26.666 2.026 2.119 56.495 0.002 0.216 0.43347 26.762 4.978 5.507 147.389 0.006 0.565 1.12948 26.859 8.542 9.778 262.615 0.011 1.006 2.01249 26.859 12.359 14.480 388.917 0.016 1.490 2.98050 26.859 16.043 19.109 513.230 0.021 1.966 3.93351 26.859 19.223 23.158 621.994 0.025 2.383 4.76652 26.859 21.577 26.184 703.261 0.028 2.695 5.38953 26.934 22.729 27.672 745.314 0.030 2.856 5.711
Alternative # 1Results
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Results
Joint W (KN) h (m) hk Whk Cvfx Fxf FINAL Fxf (KN) 41 16.261 1.671 1.726 28.063 0.001 0.096 0.19242 26.710 4.938 5.461 145.853 0.006 0.499 0.99843 26.735 8.100 9.241 247.059 0.010 0.845 1.69144 26.735 11.139 12.965 346.628 0.014 1.186 2.37245 26.735 14.044 16.588 443.486 0.017 1.518 3.03546 26.735 16.808 20.078 536.798 0.021 1.837 3.674
Case #1
Case #
2
Alternative # 2 Results
Joint # a1 a2 Dead Load (Ib) Dead Load (Kips) Dead Load (KN)41 0 12.435 1827.866 1.828 8.13042 12.435 12.466 3002.458 3.002 13.35543 12.466 12.466 3005.333 3.005 13.36844 12.466 12.466 3005.333 3.005 13.368
The various design loads calculations were performed based on
[ASCE/SEI 7-05].
Dead Load Calculations
Results
Live load acting on a typical truss joint:
Results
Joint # x1 x2 Live Load (Ib) Live Load (Kips) Live Load (KN)
49 9.954 10.360 1649.211 1.649 7.336
50 10.360 10.733 1712.419 1.712 7.617
51 10.733 11.072 1770.246 1.770 7.874
52 11.072 11.376 1822.480 1.822 8.106
Live Load Calculations
Direction #1: Perpendicular to 204 m Direction #2:
Perpendicular to 118.5m
The main equation
In wind load calculations, it is important to divide the system itself to different sections.
Wind Loads Calculations
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Wind direction
Results
Joint (deg)θ (rad)θ P (KN) Px (KN) Pz (KN)
41 60 1.0470.783 0.678 0.3912.543 -0.775 -2.422
42 58.5 1.0212.421 2.064 1.2655.945 5.069 3.106
43 55.5 0.9682.884 2.377 1.6336.413 5.285 3.632
Wind Loads Calculations
The design of the airport roofing system using AutoCAD software
Computer Model
118.5 m
31 m
4 m
System’s MaterialSteel (A572-G50)
Roofing System TypeSpace Truss
The different joints and elements were labeled in an Excel spreadsheet to be used as an input in SAP2000 Software
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Computer Model
Horizontal Structural Elements Beams &
Columns
Supports (Hinges)
Assigning Structural Loads in SAP2000
• To simulate the behavior and response of the structural system under the computed loads .
• To conduct full structural analysis of the entire system.
Assignment of the dead load Assignment of the live load
Assignment of the wind load Assignment of the earthquake load
Assigning Structural Loads in SAP2000
The analysis was carried out according to 11 loads combinations
Analysis Stage
1.2D +1.6L
1.2D + 1.6W + 0.5L
1.2D + 1E + 0.5L
Truss 3Truss 24
Steel SectionCircular cross-section
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SAP 2000 Output
Table : Sample SAP2000 Output
Frame Station OutputCase Case Type P
Text in Text Text Kip
686 147.098 D+L Combination -459.261
687 147.098 D+L Combination -346.644
688 149.035 D+L Combination -239.020
689 149.035 D+L Combination -141.728
690 147.572 D+L Combination -51.544
690 147.572 D+E1+L Combination 57.957
oThe major objective of this phase is to insure the safety and economy of the system by comparing the element's resistance with the applied load.
o A comparison was done between the two units based on the tension and compression forces for each of the combination.
Final Design Process
Type of load Comparison Design for
Compression only - Compression
Tension only - Max. Tension
Compression or Tension Compression > Tension Max. Compression
Compression or Tension Compression < Tension
Max. Tension & Max. Compression (Consider the biggest
section)
o Based on the type of load, the structural elements were classified as: • Zero force members • Compression members• Tension members
Final Design Process
o Design of Zero-Force Members
Zero-force members are special members that are designed to satisfy stiffness criterion only (i.e.; strength is not an issue).
These members should be designed following stiffness requirement of compression members.
Design of Compression Members
o Steel is known to be sensitive to buckling and, therefore, special
attention should be given to buckling behavior of these elements.
Data obtained from LRFD manual
o Procedure of designing the compression members
Design of Compression Members
Design of Compression Members
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Tension members are structural elements that are subjected to axial tensile forces.
Design of Tension Members
Failure mode #1 Design of steel due to yielding in the gross section.
Failure mode #2 Design of steel due to tensile rupture in net sections
Design of tension members
Specifications and Final Design
After designing the different elements, the appropriate steel section was selected for each element.
The design of the first upper cord is identical to the second one and same for the diagonals.
Alternative #1
Alternative #2
Steel sections
End columns and beams are secondary elements that are intended to withstand self weight of cladding sheets. They should be able to provide adequate strength for moments resulting from wind loads.
Alternative #1
Design of end beams and columns
Alternative #2
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Steel members are usually connected in the fabrication shop by welding.
In the construction site either welding or bolting could be used; however, bolting is more recommended for quality control, ease and safety reasons.
Connections
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There is a practical limit on the maximum length of steel members that could be carry to the construction site and that is about 12 to 14 meters
Connections
Alternative #1 Alternative #2
Welding process; The elements are heated and fused with molten metal added to the joint
The most commonly used welding techniques are :(1) Shielded Metal Arc Welding (SMAW), used for field welds.(2) Submerged Arc Welding (SAW), used for shop welds.
The SAW process provides more penetration into the base metal and higher strength than the SMAW process.
Type of Weld: Fillet WeldsFillet Welds (about 80% of all welds), those welds placed in a corner formed by two parts in contact (the parts to be welded)
Welded Connections
Type of Weld: Fillet WeldsAbout 80% of all welds, those welds placed in a corner formed by two parts in contact (the parts to be welded)
Types of length weld;•Longitudinal Welds(Welds that are perpendicular to direction of the load applied)
•Transverse Welds(Welds that are parallel to the direction of the applied load)
Welded Connections
The procedure for designing Welded connections
Welded Connections
∅Rn/in = 0.75(0.6 FEXX) (te) (1.5) Lw= Pu/( Rn/in)∅
Lw,min = 4Sw Lw,max = 100Sw
Connections for tension members, such as truss members, are classified as concentric shear connections, since the centroid of the connector group (fasteners or bolts) coincides with the centroid of the member.
Bolted Connections
Concentric connections
Two main load transfer mechanisms control such connections:
1. Bearing-Type Connections:• Transfer of loads depends on the Bearing at
bolt holes.• The most commonly used bolts are A325
and A490
2. Friction-Type (Slip-Critical) Connections:Load transfer depends on the friction betweenconnected parts.
Bolted Connections
The procedure for designing bolted connections
Bolted Connections
ØRn/bolt = 0.75 Ab Ft
Nb = Pu /(ØRn/bolt)
Smin = 0.67d
Smax = the smaller of [24t , 12]
S = π D / Nb
To calculate the overall cost of the project, the weight of the overall structural elements must be calculated.
The truss is divided to; Lower cord elements
Upper cord elements
Diagonals
Upper diagonals and
Horizontal elements
Purlins
Cost Estimation
Number of elements 39Section Pipe2SH40Weight (Ib/ft) 3.66Total Length (in) 6141.732Length (ft) 511.811Weight (Ib) 1873.228Weight (ton) 0.850
Data obtained
from LRFD manual
Horizontal elements (AL#2)
Truss PartLower
Chord
Upper
ChordDiagonal
Upper
Diagonal
Horizontal
ElementPurlin
Total Cost
(Dhs/ton)Total weight
(ton)3.534 4.71 8.1 2.6 0.4 0.4
Order (10%) 3.9 5.2 8.9 2.9 0.4 0.4
Truss
(Dhs/ton)27211.1 36266.7 62365 20216.4 3042.4 3042.4 152,144.1
System
(Dhs/ton)707489.2 942935.2 1621489.7 525627.5 79102.3 76059.9 3,952,704
Cost Estimation Alternative #1
Cost Estimation
Truss PartLower
Chord
Upper
ChordDiagonal
Upper
Diagonal
Horizontal
ElementPurlin
Total Cost
(Dhs/ton)Total weight
(ton)6.6 6.4 2.2 1.2 0.9 0.9
Order (10%) 7.3 7.0 2.4 1.3 0.9 0.9
Truss
(Dhs/ton)50879.5 49261.5 16717.5 9102.3 6541.2 6541.2 139,043.3
System
(Dhs/ton)1322867.1 1280799.4 434656.2 236658.9 170071.7 163530.5 3,608,584
Alternative #2
The project’s objective: to utilize the theory of structures principals and
the load and resistance factor design concepts to model, analyze and
design the steel elements and connections that make up the main
supporting element of the long-span roofing system.
For two different systems :
Full analysis and design.
Cost estimation.
Conclusion
The second alternative was found to be more efficient since it costs less than the first alternative.
This result meets our expectation since the second alternative is a single curvature arch which is more efficient in carrying loads as compared to the first alternative.
Some gained skills: Calculating the different types of load according to the detailed analytical
procedures presented by ASCE7-05, utilizing recent data such as the maps used in earthquake load calculations.
Using structural analysis software (SAP2000) to model and analyze the roofing system.
Employing the project advisor’s and coordinator’s feedback to improve our performance and learn from our mistakes.
Solving problems, overcome difficulties and acceptable time management. Enhancing team work.
• Finally, this project was very helpful and challenging at the same time.
• One remark among many is to conduct more projects and researches in the same field and other fields in Engineering to gain more experience, to develop our performance and to apply what we learnt in our career.
Thank You
