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Assessment of Building Structures under Extreme Loading. Bassam A. Izzuddin Department of Civil & Environmental Engineering. Buildings under Extreme Loading. Modelling capabilities Progressive collapse Ongoing research. Modelling Capabilities. Computational Structural Mechanics Group
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Assessment of Building Structures under Extreme Loading Bassam A. IzzuddinDepartment of Civil & Environmental Engineering
Buildings under Extreme Loading • Modelling capabilities • Progressive collapse • Ongoing research GEMS 2011 Meeting
Modelling Capabilities • Computational Structural Mechanics Group • 2 academic staff (Izzuddin, Macorini) • 2 RA’s, 8 PhD students • http://www.imperial.ac.uk/csm • Focus on structures subject to extreme loading • Developments in computational mechanics • Applied structural engineering research • Novel modelling solutions for engineering practice • Development of advanced program ADAPTIC GEMS 2011 Meeting
Modelling CapabilitiesADAPTIC • Advanced structural analysis program developed at Imperial College over past 20 years • Blast, fire, earthquake and extreme static loading • Steel, reinforced concrete and composite structures • Whole building response: frame, slabs, walls, connections,… • Geometric and material nonlinearity • Robust and efficient solution procedures • Modelling of large scale structures using HPC GEMS 2011 Meeting
Modelling CapabilitiesSimplified Methods • Framework for progressive collapse assessment • Steel beams subject to fire and blast loading • Steel/composite beams with partial strength connections • Membrane action in slabs • Influence of material rate sensitivity GEMS 2011 Meeting
Modelling CapabilitiesIntegrated Building Response • Frame/slab substructure under sudden column loss GEMS 2011 Meeting
Modelling CapabilitiesIntegrated Building Response • Composite (ribbed) floor slab system under fire GEMS 2011 Meeting
Modelling CapabilitiesConnection Failure • Detailed connection models with/without rate effect GEMS 2011 Meeting
Modelling CapabilitiesSlab failure • Mechanics-based models for slabs subject to membrane action and reinforcement rupture GEMS 2011 Meeting
Modelling CapabilitiesMasonry Structures • Material model • 3D Mesoscale model • FE modelling • Multi-scale modelling of masonry structures under extreme loading Wpl1 GEMS 2011 Meeting
Modelling CapabilitiesPartitioned Modelling on HPC • Hierarchic partitioned approach for targeted model refinement and parallelisation on HPC GEMS 2011 Meeting
Progressive Collapse AssessmentDesign-Oriented Framework • Robustness limit state • Prevention of collapse of upper floors • Stretching design envelope from strength to ductility limit • Two stages of assessment • Nonlinear static response accounting for ductility limit • Simplified dynamic assessment GEMS 2011 Meeting
Progressive Collapse AssessmentDesign-Oriented Framework • Maximum gravity load sustained under sudden column loss • Multi-level framework • Reduced model where deformation is concentrated • Columns can resist re-distributed load • Floors identical in components and loading • Planar effects are neglected GEMS 2011 Meeting
Progressive Collapse AssessmentNonlinear Static Response • Need models beyond conventional strength limit, including hardening, tensile catenary and compressive arching actions • Sudden column loss similar to sudden application of gravity load to structure without column • Maximum dynamic response can be approximated using amplified static loading (ld P) GEMS 2011 Meeting
Progressive Collapse AssessmentSimplified Dynamic Approach • Based on conservation of energy • Work done by suddenly applied load equal to internal energy stored • Leads to maximum dynamic displacement (also to load dynamic amplification) • Definition of “pseudo-static” response GEMS 2011 Meeting
Ongoing Research Projects • Robustness of composite buildings under localised fire (EU project: Liege, Imperial, Coimbra, …) • Influence of material rate sensitivity on building robustness (Imperial, Trento) • Keeping our structures standing and our people alive – The next 25 years (DHS project: Texas, Imperial, PEC, WPM) GEMS 2011 Meeting
Ongoing Research ProjectsDHS Project • Testing of 3D floor systems to failure under column loss GEMS 2011 Meeting
Ongoing Research ProjectsDHS Project • Sudden column loss vs blast damage • Column loss is an upper bound thus useful for design Sudden column loss GEMS 2011 Meeting
Ongoing Research ProjectsDHS Project • Significance of uplift under external blast GEMS 2011 Meeting