Assessment of Building Structures under Extreme Loading

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Assessment of Building Structures under Extreme
Loading

• Bassam A. IzzuddinDepartment of Civil
  Environmental Engineering

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Buildings under Extreme Loading

• Modelling capabilities
• Progressive collapse
• Ongoing research

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Modelling Capabilities

• Computational Structural Mechanics Group
• 2 academic staff (Izzuddin, Macorini)
• 2 RAs, 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

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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

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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

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Modelling CapabilitiesIntegrated Building
Response

• Frame/slab substructure under sudden column loss

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Modelling CapabilitiesIntegrated Building
Response

• Composite (ribbed) floor slab system under fire

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Modelling CapabilitiesConnection Failure

• Detailed connection models with/without rate
  effect

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Modelling CapabilitiesSlab failure

• Mechanics-based models for slabs subject to
  membrane action and reinforcement rupture

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Modelling CapabilitiesMasonry Structures

• Multi-scale modelling of masonry structures under
  extreme loading

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Modelling CapabilitiesPartitioned Modelling on
HPC

• Hierarchic partitioned approach for targeted
  model refinement and parallelisation on HPC

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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

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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

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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 (ld P)

• Need models beyond conventional strength limit,
  including hardening, tensile catenary and
  compressive arching actions

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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

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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)

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Ongoing Research ProjectsDHS Project

• Testing of 3D floor systems to failure under
  column loss

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Ongoing Research ProjectsDHS Project

• Sudden column loss vs blast damage
• Column loss is an upper bound thus useful for
  design

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Ongoing Research ProjectsDHS Project

• Significance of uplift under external blast