MAM Colaps Progresiv Curs AMI - Mai 2013

8/13/2019 MAM Colaps Progresiv Curs AMI - Mai 2013

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APLICATII ALE MECANICII MATERIALELOR IN EVALUAREA

RISCULUI DE COLAPS PROGRESIV AL STRUCTURILOR

Studiu de caz

1. Colaps progresiv

2. Cauze: - naturale

- man-made

3. Istoric - Roman Point Apt. Building /London, 1968

- The Alfred P. Murrah Federal Building / Oklahoma City, 1995


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Roman Point Apt. Building

London, 1968


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The Alfred P. Murrah Federal Building / Oklahoma City, 1995


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1. Programe de calcul comerciale (FEM)simple : LSA

- avansate: NSA& NDA

2. ASI (Applied Science International)

ELS software -> AEM

- comportare elastica

- fisurare

- deformatii mari- separarea/ruperea unor elemente

- miscarea de rigid a corpurilor dizlocate

- coliziuni intre corpuri dizlocate si structura

- identificarea cauzelor si prognozarea efectelor

Prognozarea riscului de colaps progresiv


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Pod metalic in Mineapolis (2007)


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Oklahoma City (1995)


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1. Filosofie de proiectare

2. Alternative Path Method (APT)

GSA Guidelines (2003)

analiza seismica- continuitate structurala

- redundanta structurala- ductilitate

3. Proceduri: missing column scenarios - Dept. of Defence (DoD)

Unified Facilities Criteria (UFC 4-023- 03- revised July 2009)

4. Cerinte de cod:EN 1990sect. 2.1 IBC 2009

ASCE/SEI 7-05 EC1

ACI 318-05 BS 5950-2000

NBC 2005/Canada Saudi Building Code (SBC 301-2007)


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1. P100-2006sect. 4.4.1.2cerinte de evitare a CP:

2. Proiectare antiseismica & integritate structurala

3. Studii teoretice:

* Baldridge & Humay (2003)12 etaje - zona 2B (UBC)

- zona 4

Progressive Colapse vs. Seismic Design


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Baldridge & Humay (2003)

Fig. 1: Effects of losing an external column to a blast loading: (a) exterior blast loading;

(b) conventional design: progressive collapse; and (c) alternate load path design: noprogressive collapse


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Baldridge & Humay (2003)

Fig. 2: Response of beam for missing column scenario: (a) gravity-load designed beam;

and (b) seismically designed beam


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Bilow & Kamara (2004)12 E - 3 x 7,30m ; 5 x 7,30 m

3 categorii seismice (A, C, D)


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Wei Yi et al.ACI Structural JournalAugust 2008Experimental Study on PC-Resistant Behaviour of RC Frame Structures

- Stadii de lucru

- Mecanisme de transmitere a solicitarii


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Kazunori FujikakeJournal of Structural EngineeringAugust 2009Impact Response of RC Beam


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Kazunori FujikakeJournal of Structural EngineeringAugust 2009Impact Response of RC Beam


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Kazunori FujikakeJournal of Structural EngineeringAugust 2009 Impact Response of RC BeamComparatie intre comportarea sub sarcini statice si dinamice (impact)


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Ioani, Cucu & Mircea C. (2007), (2008), (2010):Ioani, Marchis, Moldovan, Bredean & Botez (2012): Vulnerability to progressive collapse of RC buildings

Figure 1. Possible blast behavior of frame structure.

Fig. 4. Missing column scenarios for exterior columns

stst

stdyn Ph

PP 2

11

(1))25.0(2 LDLoad

(2)

Obiective:

Following the GSA Guidelines (2003)-LSA [3], the present paper examines the vulnerability of a medium-rise building,

having a RC reinforced concrete framed structure seismically designed for Bucharest (Romania) according to P 100-92,

a zone of high seismic risk (degree VIII on the MSK Intensity Scale, zone C, seismic coefficient PGA/g=0.20).


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Ioani, Cucu & Mircea C. (2007), (2008), (2010):Seismic design vs. progressive collapse: a RC framed structure case study

where QUD- acting force (demand) in the component or connection (moment, axial force, shear and possible combinedforces) and Q

CE- expected ultimate un-factored capacity of the component or connection (=1.0).

Expected strength is defined as the mean maximum resistance expected over a range of deformations to which the

concrete component is likely to be subjected( DoD 2009); expected yield strength of reinforcing steel includes

consideration of material overstrength and strain hardening( 1.25-GSA; 1.50-DoD/concrete&1.25-DoD/steel).

According to the GSA Guidelines, acceptance criteria, the allowable DCR values for structural elements are: DCR 2.0

for typical structural configurations and DCR 1.5 for atypical structural configurations. Using the DCR concept of linear

elastic approach, structural elements that have DCR values exceeding the allowable magnitudes are considered to be

severely damaged or collapsed.

It is underlined that if the DCR for any member is exceeded, based upon shear force, the member is to be regarded as

a failed member. In addition, if the flexural DCR values for both ends of a member as well as the span itself are

exceeded (creating the classical three hinged failure mechanism), the member is also to be seen as a failed member.

For continuous elements, the flexural DCR value at an element section may exceed 1.0 because in this case flexural

demand can be redistributed along the length of the element to sections that have reserve flexural capacity [Baldrige &

Humay, 2005].

The magnitude and distribution of these demands will be given by the concept of DemandCapacityRatios defined

as [GSA, 2003]:

CEUD QQDCR

(3)


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Ioani, Cucu & Mircea C. (2007), (2008), (2010):

Seismic design vs. progressive collapse: a RC framed structure case study

Modelul structurii analizate cu programul

AutodeskROBOT Structural Analysis

Fig. 5. ROBOT Millenium model of a 13-story

RC building: missing column scenarios.

Analiza seismica

The seismic analysis is performed for Bucharest

(zone C on the Romanian zonation map with

ks=PGA/g=0.2).For Romania, the seismic coefficient ks varies from

0.08 to a maximum value of 0.32.

The magnitude of total equivalent seismic force S that

enters the load combination (Eq. 4) is calculated as

follows [P100-92,1992]:

GGTkS s 0945.0 (5)


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Detalii de armare

Proprietatile materialelor


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Eforturi in structura avariata: cazul C1

Figure 4.

Bending moments and flexure DCR values in beams,

case C1, transversal exterior frame under 2(D+0.25L).

Figure 5.

Shear forces and shear DCR values in beams, case C1,

transversal exterior frame under 2(D+0.25L).


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Structura avariata: cazul C3

Figure 6.

Damaged structure (case C3) under gravity loads

2(D+0.25L): beam moment diagrams

Figure 7.


2(D+0.25L): beam DCR values for flexure


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Structura avariata: cazul C3

Figure 8.


2(D+0.25L): beam shear diagrams

Figure 9.


2(D+0.25L): beam DCR values for shear


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CONCLUZII & COMENTARII

1)The GSA Guidelines [3] offer a realistic approach and performance criteria for these determinations.

2)A typical medium-rise building (13 stories) having RC frames, seismically designed for the Bucharest a zone of high

seismic risk- does not experience progressive collapse when subjected to different missingcolumnscenarios, according to

GSA Guidelines [3]. Similar results [1] have been found for a 12-story RC framed structure seismically designed for a

moderate (Zone 2B) or a high seismic risk zone (Zone 4) according to the requirements of a Uniform Building Code (UBC-

1991 edition).

3)The concept of DCR offers to engineers a valuable tool to identify the magnitude and distribution of potential areas of

inelastic demands and thus, the extension of potential collapse zone can be evaluated and compared to the maximum

allowable collapse area resulting from the instantaneous removal of an exterior or interior column.

4)The maximum computed DCR values well below the allowable values (2 for typical structural configuration and 1.5 for

atypical configuration) show that RC frames, seismically designed and detailed according to the former Romanian Seismic

Design Code P100-92 [5] for at least zone C on the Romanian territory seismic map (ks=0.20) have an inherent capacity to

better resist progressive collapse.

5)The numerical results indicate the possibility that similar structures erected even in lower seismic areas, for instance zone D(ks=0.16) or zone E (ks=0.12) [5], to fulfill the requirements for a structure of low potential for progressive collapse.

6)For the Romanian zones of high seismic risks as the zone C (ks=0.20), zone B (ks=0.25) and zone A (ks=0.32) [5], further

analyses are required to determine the vulnerability to progressive collapse of other types of structural systems, including the

existing RC frames of 7 to 9 story high.

7) It has to be underlined that even in the regions of low seismic activity, the use of Special Moment Frames rather than

Ordinary Moment Frames is highly recommended because it involves an average increase in the total construction cost of only

1 to 2 percent, and on the other hand, significantly improves the buildingsability to better resist the extreme loads of a blast

by reducing the potential of progressive collapse following an explosion [8].

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MAM Colaps Progresiv Curs AMI - Mai 2013