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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 - PowerPoint PPT Presentation
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Imperial CollegeLondon
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
26 January 2011 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
36 January 2011 GEMS 2011 Meeting
• 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
46 January 2011 GEMS 2011 Meeting
Modelling CapabilitiesADAPTIC
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
56 January 2011 GEMS 2011 Meeting
Modelling CapabilitiesIntegrated Building Response
• Frame/slab substructure under sudden column loss
66 January 2011 GEMS 2011 Meeting
Modelling CapabilitiesIntegrated Building Response
• Composite (ribbed) floor slab system under fire
76 January 2011 GEMS 2011 Meeting
Modelling CapabilitiesConnection Failure
• Detailed connection models with/without rate effect
86 January 2011 GEMS 2011 Meeting
Modelling CapabilitiesSlab failure
• Mechanics-based models for slabs subject to membrane action and reinforcement rupture
96 January 2011 GEMS 2011 Meeting
Duc
tility
lim
it
Modelling CapabilitiesMasonry Structures
• Multi-scale modelling of masonry structures under extreme loading
106 January 2011 GEMS 2011 Meeting
Modelling CapabilitiesPartitioned Modelling on HPC
• Hierarchic partitioned approach for targeted model refinement and parallelisation on HPC
116 January 2011 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
126 January 2011 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
136 January 2011 GEMS 2011 Meeting
Progressive Collapse AssessmentNonlinear Static Response
• Sudden column loss similar to sudden application of gravity load to structure without column– Maximum dynamic response can be approximated using
amplified static loading (d P)
146 January 2011 GEMS 2011 Meeting
• Need models beyond conventional strength limit, including hardening, tensile catenary and compressive arching actions
• 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
Progressive Collapse AssessmentSimplified Dynamic Approach
156 January 2011 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)
166 January 2011 GEMS 2011 Meeting
Ongoing Research ProjectsDHS Project
• Testing of 3D floor systems to failure under column loss
176 January 2011 GEMS 2011 Meeting
Ongoing Research ProjectsDHS Project
• Sudden column loss vs blast damage– Column loss is an upper bound thus useful for design
186 January 2011 GEMS 2011 Meeting
Suddencolumn loss
Ongoing Research ProjectsDHS Project
• Significance of uplift under external blast
196 January 2011 GEMS 2011 Meeting
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