Presentation on theme: "Robustness assessment for multiple column loss scenarios"— Presentation transcript:
1 Robustness assessment for multiple column loss scenarios M. Pereira and B. A. IzzuddinDepartment of Civil and Environmental Engineering
2 Robustness assessment framework Damage ScenariosSingle Damage ScenarioMultiple Damage ScenariosSudden single column lossSudden single column lossSudden two adjacent column loss
3 Column loss scenario – Main Stages Nonlinear static response of the damaged structure under gravity loadingSimplified dynamic assessment to establish the maximum dynamic response under column loss scenariosDuctility assessment of the connections/structure
4 Dynamic response of a SDOF system – Point Load -=
10 Longitudinal edge beam - Rigid Column 2 Point LoadUniformly Distributed LoadSlight overestimation as expected in the static analysis more visible for 2 point load (concentrated masses)High frequencies excitation for uniformly distributed mass caseAccurate approximation of the dynamic response for both loading cases
11 Longitudinal edge beam - Flexible Column Uniformly Distributed LoadSlight overestimation in the static analysisHigh frequencies excitationGood approximation of the dynamic response for a case with variable deformation mode during loading
12 Individual floor level Detailed Floor Grillage ModelSimplified Floor Grillage ModelCompatibility between members assuming a governing modeand
13 Individual floor (Pseudo) Static vs. Dynamic Detailed Model (Pseudo) Static Detailed vs. Simplified ModelsGood approximation of floor vertical support reaction from individual beams (rigid columns) vertical reaction profilesBetter approximation of structural response from assembling individual beams with rigid columns, rather than flexible columnsUse of longitudinal edge beam for governing member and imposed compatibility in remaining floor membersAccurate approximation of the dynamic responseDominant trapezoidal mode of deformation for floor systemAdditional rotational restraint given by transverse beams torsional stiffnessVertical displacement point of zero system acceleration (maximum static displacement) corresponds to point of exact vertical reaction prediction as expectedUnder/overestimation of vertical support reaction is observed for total down/upwards acceleration
14 ConclusionsSuccessful extension of the multi-level simplified dynamic assessment to structures subjected to two adjacent columns lossDominant trapezoidal mode observed even for asymmetric load/structural configurationConsideration of reaction transmitted to surrounding structure for alternate load path assessment (including column resistance / connection shear failure)Further studies on effect of high frequency excitation in instantaneous system failure
15 Conclusions Comparing the dynamic and pseudo-static responses: Validity of the assumption of zero kinetic energy at maximum dynamic displacement for MDOF system;Conservative assumption of the inertial forces distribution for determination of dynamic vertical support reaction.Comparing detailed and simplified assembly models responses:Simplified models are feasible for structures exhibiting constant deformation mode during loading.
16 Multiple floors level Detailed Multiple Floors Model Simplified Multiple Floor ModelCompatibility between members assuming a governing modeand
17 Multiple floors (Pseudo) Static Detailed vs. Simplified Models (Pseudo) Static vs. Dynamic Detailed ModelSatisfactory approximation of floor vertical support reaction from individual beams (rigid columns) vertical reaction profiles taking into account moderate load redistribution between floorsGood approximation of structural response either using detailed floors assembly or starting from individual beams assembly.Equally satisfactory approximation using either 1st Floor or Roof longitudinal edge beams as governing membersAccurate approximation of the dynamic responseDominant trapezoidal mode of deformation for multiple floor systemVertical displacement point of zero system acceleration (maximum static displacement) corresponds to point of exact vertical reaction prediction as expectedUnder/overestimation of vertical support reaction is observed for total down/upwards acceleration
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