progressive collapse analysis

R.JEYANTHI

PROGRESSIVE COLLAPSE

CAUSES

Design mistake

Faulty construction

Abnormal load events

Pressure Loads Impact Loads

- Internal gas explosions - Aircraft impact

- Blast - Vehicular collision

- Wind over pressure - Earthquake

- Extreme values of - Overload due to

environmental loads occupant overuse

PROGRESSIVE COLLAPSE DESIGN STRATEGIES

TYPE OF APPROACHES

DIRECT

SPECIFIC LOCAL

RESISTANCE

ALTERNATE PATH

METHOD

INDIRECT

PRESCRIPTIVE DESIGN RULES

OBJECTIVE

To design G+8 RC structure

To analyze the structure by Non linear static analysis method

To perform pushover analysis for the structure with removal of critical columns fully and partially

To determine the potential for progressive collapse

To give the preventive measures

SCOPE

Reduction of potential for progressive collapse in new and renovated Federal buildings

Potential of progressive collapse is assed using Non linear static analysis

method since it gives economical design

STUDYING THE VULNERABILITY OF STEEL MOMENT RESISTANT FRAMES SUBJECTED TO PROGRESSIVE COLLAPSE

Mojtaba Hosseini, Nader Fanaie and Amir Mohammad Yousefi

Steel Building

10 storey building, 5x5 panels each 5x5m

Analysis Nonlinear Dynamic Procedure

Removal Corner columns from 1st storey, 5th storey, 8th storey and 9th storey

S/W Open Sees program

Results After the removal of corner column A1compressive axial forces of adjoining column and in other columns

CASE I increased 8.8 times the primary forces and 5.21 times.

CASE II increased 8.6 times the primary forces and 5.16 times

CASE IIICASE IV

increased 8.67 times the primary forces and 5.19 timesincreased 8.66 times the primary forces and 5.23 times

Conclusion The axial force values of adjoining columns are 30% and 40% greater than their ultimate strengths Safety is achieved by increasing column dimensions or using new materials and methods.

PROGRESSIVE COLLAPSE ANALYSIS OF A REINFORCED CONCRETE FRAME BUILDING

Shefna L Sunamy, Binu P, Dr. Girija K

Building description

12 storey R.C. building. Six bays of 5 m in the longitudinal direction , four bays of 5 m in the transverse direction

Modeling & analysis

The structure is modeled using SAP 2000 Non Linear static progressive collapse analysisSeismic loading is considered (Zone II, III, IV ,V)

Column removal scenario

Long side column removed Short side column removed Corner column removed

DCR Demand capacity ratio should satisfy acceptance criteria

GSA guidelines

DCR < 2.0 for typical structural configurations DCR < 1.5 for atypical structural configurations

Conclusion Seismically Designed building resist progressive collapse.Nonlinear static analysis reveals hinge formation starts from the location having maximum demand capacity ratio.To mitigate progressive collapse an alternate load path has to be provided (Providing bracings, increasing column dimension)

Progressive Collapse Analysis of Reinforced Concrete Framed Structure Raghavendra C, Mr. Pradeep A R


-For the analysis, a typical frame of height 37.5 m is considered -All the supports are modeled as fixed supports

Analysis - Linear Static analysis is used to analyze the structure

Software -ETABS v9.7 for the IS 1893 load combinations

Column removal

- For PC analysis the columns at eight different location is removed for each case

Progressive

Collapse Analysis

-RC frame in the earthquake zones 2, 3, 4 and 5 is designed usingETABS program for dead, live, wind and seismic loads.

- The specified GSA load combination was applied- The Demand Capacity Ratio (DCR), the ratio of the member force and themember strength is calculated.

Conclusion - While removing the column the intersecting beams of the shorterspan beams tend to take the extra burden load and DCR values ofthat beams were more compared to longer span beams.- To avoid the progressive failure of beams and columns, adequatereinforcement is required to limit the DCR within the acceptancecriteria.

PROGRESSIVE COLLAPSE ANALYSIS OF REINFORCED CONCRETE FRAMED STRUCTURE

Rakshith K , Radhakrishna

Buildingdescription & Modeling

Typical frame structure of height 37.5m is considered.

It is modeled using ETABS v9.7 software. Linear static analysis is conducted on each of these models.

Analysis Analysis is carried out by ETABS Software for IS 1893 load combinations.

Column removal

Critical Column are removed for progressive collapse analysis in different cases. Separate linear static analysis is performed for each case.

DemandCapacity ratio

DCR for flexure at all storeys is calculated for three cases of column failure. Demand capacity ratio < 2.0 (acceptance criteria as per GSA 2003

Results C1 removed

B1 and B5 exceed acceptance criteria value suggested by GSA for progressive collapse guidelines

C16removed

B23 and B24 exceed acceptance criteria value suggested by GSA for progressive collapse guidelines as

C18removed

B25 and B26 exceed acceptance criteria value suggested by GSA for progressive collapse guidelines

Conclusion Progressive failure of beams and columns is avoided by adequate reinforcement is required to limit the DCR within the acceptance criteria. It can develop alternative load paths

Progressive Collapse of Steel Frames Kamel Sayed Kandil, Ehab Abd El Fattah Ellobody

Steps carried out:

Modeling

Cases considered

Results

2D models for different cases and 3D model is analysed and

compared

3, 6, 9, 12 storey building is considered for damping ratio 5%,

6%, 8%, 10%

Finally all the cases were compared

Conclusion: Increase in damping ratio decrease the lateral deflection

Increase in no of stories decreases the potential for

progressive collapse

Evaluation of progressive collapse potential of multi-story moment resisting steel frame buildings under lateral loading

H.R. Tavakoli , A. Rashidi Alashti

Analysis method

Nonlinear static analysis for progressive collapse under seismic loading 3-D and 2-D models of SMRF were considered for push over analysis (ETABS)

LateralLoading pattern

Triangular load pattern

Uniform load pattern

Capacity curve for both the pattern in determined

ColumnRemoval

Critical column is made to lose 40%, 70% and 100% of effective area.

Capacity curve for each cases are determined and compared.

ToDetermine

Robustness indicatorDuctility ratio Plastic hinge rotation

Conclusion Number of stories and bays are Increased capacity of the structure to resist progressive collapse under lateral loading also increased. Increasing the number of bays and stories, induces a higher level of robustness index.

3-D Nonlinear Static Progressive Collapse Analysis of Multi-story Steel Braced Buildings

H.R. Tavakoli, A. Rashidi Alashti & G.R. Abdollahzadeh


Special dual system SMRF with concentrically X braces CASE I - 5 stories buildings with 4 spans CASE II - 15 stories buildings with 6 spans

Lateral load patterns

Uniform pattern +ve and –ve Triangular pattern +ve and -ve

ToDetermine

Robustness indicatorDuctility ratio Plastic hinge rotation

Conclusion Triangular pattern induce the least capacity curve for intact and damage structureRobustness index in uniform and triangular pattern is almost the same. Number of stories and bays are increased larger capacity to resist progressive collapse under lateral loading and higher level of robustness index obtained.

Progressive Collapse Assessment of RC Structures under Instantaneous and Gradual Removal of Columns

A.R. Rahai, M. Banazadeh, M.R. Seify Asghshahr & H. Kazem


5 story RC structure model with RC resisting moment frames at either side was designed using a high ductility level.

Column removal scenario

Three columns are removed, Instantaneously Gradually

Analysis method

For instantaneous removal method static analysis is performed

In gradual reduction method concrete strength reduction factor is determined

Modeling 3D model of the RC structure was developed using Opensees software

Results Instantaneous removal- 4 sec once column C1 was removed - Maximum vertical displacement is 1.411 m occurring at t=1.19 sec.

Gradual removal- 34200 sec once column C1 was removed- Maximum vertical displacement is 1.03m.

Progressive Collapse Analysis Of Building

Miss. Preeti K. Morey Prof S.R.Satone

Mathematicalmodeling

Using STADD Pro software 3d model of a frame is analyzed

DCR ( AcceptanceCriteria)

For typical structure (symmetrical structure) = DCR≤ 2.0For typical structure (unsymmetrical structure) = DCR≤ 1.5 DCR= M max / Mp

Performanceanalysis

C1 , C3 is removed and critical column is identified for both static and seismic case. Result of column wise DCR of Linear Static analysis and linear dynamic analysis for both static and seismic case is considered.

CONCLUSION Case II - RC Frame with removal of column c3 has highest DCR value in comparison with case I. DCR of column c3 is 1.98 which is less than 2 i.e. GSA criteria. Hence the frame is less vulnerable to progressive collapse.

Analytical Study of Seismic Progressive Collapse in one-Story Steel BuildingF. Nateghi Alahi

Introduction Corner-column building was weakened to navigate the initial damage toward a certain part of the structure. Nonlinear static analysis was carried out

FEM GSA progressive collapse guidelines were applied

NumericalAnalysis

Combination of gravity loads was applied to the structure and then the push-over analysis was carried Plastic hinges of Damaged and primary model was compared. Push over curve indicates that damaged model has less secondary stiffness than the primary one.

Conclusion Collapse pattern is in a way that the deformation of damaged frame increases near the failed column and further away from it, deformation of the frames decreases. So during an earthquake progressive collapse gets started fromdamaged frames then passes through the others beside it.

Linear and nonlinear analysis of progressive collapse for seismic designed steel moment frames.

M. A. Hadianfard & M. Wassegh

Structuralmodel

3-story and 6-story SMRF designed for medium level and very high level seismic zones

Analysis -Linear static analysis & Non Linear static analysis carried out as per 1. GSA 2003, 2. UFC 2009

- Push down curves are determined

Conclusions - potential of progressive collapse decreases with increasing the height of the structures - In short steel structures steel structures designed for higher seismicity, there is less possibility of occurrence of progressive collapse.- In LSA, the resisting-capacity of progressive collapse of UFC 2009 is less than the GSA 2003. And for NLSA it is vice versa- For mitigating progressive collapse, the gravity loads should not have one-way patterns, so that gravity loads will not be concentrated in some elements and the potential of progressive collapse can be decreased in the structure.

Progressive Collapse Analysis of an RC Building with Exterior Non-Structural WallsMENG-HAO TSAI*, TSUEI-CHIANG HUANG

Types of Exterior Non-Structural Walls

Parapet-type wall, Wing-type wall , Panel-type wall.

Building description Column loss scenario

Elastic displacement Progressive Collapse Analysis

10-story, MRRC building with a 2-story basement In 1st storey at 3 different location columns are removed

(Case 1A, 1B, 2A) RC frame > parapet walls >wing walls >panel walls linear static analysis and Non linear static analysis

Conclusion Linear static analysis results - DCRs of beams are generally reduced with consideration of the exterior walls

Nonlinear static analysis results - collapse resistance of the RC building subjected to column loss may be significantly increased with the wing-type walls

Fragility Assessment of Progressive Collapse BuildingsKuan-Hsoung Chen

Objective

Modeling

- To identify the progressive damage by the nonlinear pushover analysis.- 2D nine-story, 3bay MRF building

Column loss scenario

Capacity curves

- 8 cases were considered- T of various locations of column removal scenarios were determinedNonlinear pushover analysis-capacity of column loss in 1st story is 3 times greater than column in roof story.- Strength of removal interior columns are greater than corner column loss.

Nonlinear hinges plastic hinges is generated from lower story to higher story with an increase of incremental vertical loadings

Conclusions - Ground level column loss activate the damage above the column removal and don’t propagate to its neighboring spans. - The roof level column loss only leads to local damage

Assessment of progressive collapse-resisting capacity of steel moment frames

Jinkoo Kima, Taewan Kimb

Analysis procedure

Acceptance criterion(as per GSA2003)procedure for linear static analysis

Applied loads for static and dynamic analyses

-DCR vary from 1.25 to 3.0

- Remove column , carry linear static analysis

- Check DCR in each structural member- At each inserted hinge, equal but opposite moments are applied -Steps are repeated until DCR of any member does not exceed the limit - For static analysis both the GSA 2003 and the DoD 2005 use dynamic amplification factor of 2.0 in load combination

Analysis of model Open sees software- Linear dynamic and Non linear dynamic analysis is carried out

Conclusion - SMRF designed for lateral load is less vulnerable for progressive collapse. -potential for progressive collapse was highest when a corner column was suddenly removed.- progressive collapse potential decreased as the number of story increased.

Design of steel moment frames considering progressive collapseJinkoo Kim and Junhee Park

Analysis of structure

• 3x3 bay and 9-story. Span length are varied as 6 m, 9 m, and 12m.• Nonlinear dynamic analysis using the program code OpenSees

Progressive collapse potential.

- Vertical deflection as bay width and girder size decreases .- beam size may lead to strong beam weak Column.- Weak story is prevented if summation of plastic moment capacity of columns > than beam.

Plastic design

- vertical deflection if damping ratio and stiffness ratio

Conclusion Structures redesigned by plastic design method to prevent progressive collapse turned out to satisfy the given failure criterion in most of the model structures.

METHODOLOGY

Detailed study of literature review

G+8 RCC building is taken for Project

Prepare AUTO CAD plan for G+8 structure

Modeling in ETABS

Non linear static analysis is carried out

Identification of critical column

Removal of critical column to initiate progressive collapse

DCR, Robustness indicator are determined

Result comparison – before & after progressive collapse

check for acceptance criteria as per GSA 2003 guidelines

By this evaluation a building can be assessed whether it can withstand progressive collapse

AUTO CAD DRAWINGS

ETABS Modeling

Front and side elevation of building

Non Linear static analysisSteps to be followed: Preliminary Pushover Analysis

Procedure:- Modeling of structure is carried out- Load cases are defined

- Loads are assigned- Load combinations are provided as per IS 875 part 5

Seismic load case:

Response spectrum user defined file

ELX Res spec x

ELY Res spec y

Wind load case:Applied as point load in floor diaphragms

WLX Wind load along X direction

WLY Wind load along Y direction

Gravity load case:

DL Self weight

DI Super imposed load

LL 1 live load greater that 3

LL 2 live load lesser than 3

Load combination as per IS 875 part 5DL – Dead load, DI – Dead Imposed, WLX- Wind load in direction, WLY – Wind load in Y direction,

EQX,EQY – Seismic load in X&Y direction

Basic Load Case COMB001 - 1.5 DL + 1.5 DL1 + 1.5 DL2 + 1.5 LL1 + 1.5 LL2 + 1.5 LL3

Seismic Load CasesCOMB002 - 1.2 DL + 1.2 DL1 + 1.2 DL2 + 0.6 LL1 + 0.3 LL2 + 1.2 ELX COMB003 - 1.2 DL + 1.2 DL1 + 1.2 DL2 + 0.6 LL1 + 0.3 LL2 + 1.2 ELY COMB004 - 1.5 DL + 1.5 DL1 + 1.5 DL2 + 1.5 ELX COMB005 - 1.5 DL + 1.5 DL1 + 1.5 DL2 + 1.5 ELY COMB006 - 0.9 DL + 0.9 DL1 + 0.9 DL2 + 1.5 ELX COMB007 - 0.9 DL + 0.9 DL1 + 0.9 DL2 + 1.5 ELY

Wind Load Cases COMB008 - 1.2 DL + 1.2 DL1 + 1.2 DL2 + 1.2 LL1 + 1.2 LL2 + 1.2 LL3 + 1.2 WLX COMB009 - 1.2 DL + 1.2 DL1 + 1.2 DL2 + 1.2 LL1 + 1.2 LL2 + 1.2 LL3 - 1.2 WLX COMB010 - 1.2 DL + 1.2 DL1 + 1.2 DL2 + 1.2 LL1 + 1.2 LL2 + 1.2 LL3 + 1.2 WLY COMB011 - 1.2 DL + 1.2 DL1 + 1.2 DL2 + 1.2 LL1 + 1.2 LL2 + 1.2 LL3 - 1.2 WLY COMB012 - 1.5 DL + 1.5 DL1 + 1.5 DL2 + 1.5 WLX COMB013 - 1.5 DL + 1.5 DL1 + 1.5 DL2 - 1.5 WLX COMB014 - 1.5 DL + 1.5 DL1 + 1.5 DL2 + 1.5 WLY COMB015 - 1.5 DL + 1.5 DL1 + 1.5 DL2 - 1.5 WLY COMB016 - 0.9 DL + 0.9 DL1 + 0.9 D + 1.5 WLX COMB017 - 0.9 DL + 0.9 DL1 + 0.9 DL - 1.5 WLX COMB018 - 0.9 DL + 0.9 DL1 + 0.9 DL2 + 1.5 WLY COMB019 - 0.9 DL + 0.9 DL1 + 0.9 DL2 - 1.5 WLYLoad combination as per GSA Guidelines For static Analysis2 ( LL + 0.25 DL)

Maximum displacement occurs for the combination 1.5DL+ 1.5DI + 1.5WLY For this combination the bending moment action and axial force on the columns in the ground floors were compared to identify the critical members

Alternate path methodThe ratio of bending moment of the damaged building to the intact building is calculated to check the bending moment behavior of the adjacent columns and adjoining beams of the removed column

Based on this the alternate path for the load flow can be figured out

Bending Moment Behavior of structural elements in Case1 (for load combination based on IS 875 part 5)

Bending Moment acting on frame

Bending Moment ratio(Intact to collapsed frame)

Bending Moment Behavior of structural elements in Case1 (for load combination based on GSA guidelines)

Bending Moment acting on frame


Bending Moment Behavior of structural elements in Case2 (for load combination based on IS 875 part 5)

Bending Moment acting on frameBending Moment ratio

(Intact to collapsed frame)

Bending Moment Behavior of structural elements in Case2 (for load combination based on GSA guidelines)

Bending Moment acting on frameBending Moment ratio

(Intact to collapsed frame)

Bending Moment Behavior of structural elements in Case3 (for load combination based on IS 875 part 5)Bending Moment acting on frame


Bending Moment Behavior of structural elements in Case3 (for load combination based on GSA guidelines)Bending Moment acting on frame


In the case1 the bending moment of the columns in the storeysabove the location of removed column remains unchanged, where as the bending moment of the columns in the storey adjacent to either side of the removed column as been increased. And the bending moments of adjoining beams were also increased.

In the case2 also the bending moment of the columns in the storeys above the location of removed column remains unchanged and the bending moment of columns in the storey adjacent to either side of the removed column as been increased. And the bending moments of adjoining beams were also increased.

In the case 3 the bending moment of the columns in the storeysabove the location of the removed column has been reduced and the bending moments has been increased for the remaining columns in the ground storey. And the bending moments of adjoining beams were also increased.

Demand Capacity ratio

Demand Capacity Ratio (DCR) is the ratio of Member force to the Member strength.

DCR = Member force/ Member strength

Allowable DCR < 2, for typical structural configuration,

< 1.5, for atypical structural configuration.

DCR is calculated for the each elements in the frame which consists of removed column

DCR values for case 1(for gravity loads) (for gravity loads and lateral

loads)


loads)

According to the GSA guideline atypical frame building having DCR values greater than 1.5 indicate that the portion is severely damaged and have more damage potential.

It can be seen that in the third case that the demand to capacity ratio (DCR) values exceeds the acceptance criteria in the first and second storey beam. But in other spans damage could not propagate.

(for gravity loads) (for gravity loads and lateral loads)

The maximum DCR value experienced by the frame is 1.71. So in the third case there is possibility for the spread of collapse.

The maximum DCR value experienced by the frame is 1.7. So in the third case there is possibility for the spread of collapse.

Robustness Indicator

Here since the robustness Indicator is almost equal to 1, the structure is able to provide an alternative load path if the structure is damaged.

Cases Removed

column

V damaged Robustness

indicator

Case1 Middle 6837KN 0.99

Case2 Inner 6837KN 0.99

Case3 Corner 6836KN 0.94

Summary From Comparing the Bending Moment and shear force

for Intact structure and all the three cases it has beenconcluded that in case 3 the bending moment andshear has been increased more (ie When the cornercolumn is removed BM and SF increase morecompared to other cases).

After determining the DCR values for gravity loadsalone and lateral loads, then it is compared.

Robustness Indicator is calculated for Intact and otherthree cases and it is not equal to 0ne expect for intact,which shows that the building is vulnerable.

progressive collapse analysis

Engineering