Response of Masonry Cavity Cladding under Blast Loading

Response of Masonry Cavity Cladding under Blast Loading J. Gu, L. Macorini, B. A. Izzuddin Computational Structural Mechanics Group Civil and Environmental Engineering Department Imperial College London

Cladding systems under blast loading Khobar Towers bomb, 1996, Saudi Arabia Quarters foreign military personnel most of the 19 U. S. servicemen who lost their lives were heavily injured by the high-speed projectiles of the failed exterior cladding Tianjin explosions, 2015, China Civil-Comp Conference, 2015, Prague 1/8

Contents • Reduced models of masonry cavity cladding • Modelling techniques • Responses of the reduced models under blast loading • Comparison of the reduced models against a complete model Civil-Comp Conference, 2015, Prague 2/8

Masonry cavity cladding Height: 900 mm Length: 1600 mm Depth: 102. 5 mm+80 mm+100 mm=282. 5 mm Unconfined reduction: Unrestrained side edges Confined reduction: Fully restrained side edges Civil-Comp Conference, 2015, Prague 3/8

Contents • Reduced models of masonry cavity cladding • Modelling techniques • Responses of the reduced models under blast loading • Comparison of the reduced models against a complete model Civil-Comp Conference, 2015, Prague 2/8

Modelling techniques • Mesoscale description for masonry panels Civil-Comp Conference, 2015, Prague 4/8

Modelling techniques • • Mesoscale description for masonry panels Partitioning scheme: each panel is modelled as a separate child partition to allow parallel computation. Correlation of panels and wall ties are achieved and realized on the parent level. Civil-Comp Conference, 2015, Prague Partition 2 Partition 1 4/8

Modelling techniques • • • Mesoscale description for masonry panels Partitioning scheme: each panel is modelled as a separate child partition to allow parallel computation. Correlation of panels and wall ties are achieved and realized on the parent level. Partition 2 Partition 1 Mix-dimensional coupling: master-slave elements are adopted to couple the 6 -dof nodes of the beam-column elements with the 3 -dof nodes in the mesoscale models. Civil-Comp Conference, 2015, Prague 4/8

Contents • Reduced models of masonry cavity cladding • Modelling techniques • Responses of the reduced models under blast loading • Comparison of the reduced models against a complete model Civil-Comp Conference, 2015, Prague 2/8

Unconfined model reduction • Concentrated deformation: Deformation is concentrated at lowest bed joints while panels remain relatively undamaged. Civil-Comp Conference, 2015, Prague 5/8

Unconfined model reduction • Concentrated deformation: Out-of-plane displacements at the top of both panels Deformation concentrates at the lowest bed joints while the panels remain relatively undamaged. • Brittle failure: With Δt=100 ms, when the intensity of the applied deflagration wave is above 40 mbar, brittle failure is triggered. Damage increases with intensity Civil-Comp Conference, 2015, Prague 5/8

Unconfined model reduction • Applied and transferred blast loads Concentrated deformation: Deformation is concentrated at lowest bed joints while panels remain relatively undamaged. Brittle failure: With Δt=100 ms, when the intensity of the applied deflagration wave is above 40 mbar, brittle failure is triggered. Damage increases with intensity. Transferred blast load Applied blast load 5 4 Forces (k. N) • 6 40 mbar-intensity 3 2 1 0 -1 0 Quasi-static response: Prior to brittle failure, blast load is fully transferred to floor system; after brittle failure, transferred blast load drops significantly. 0. 05 0. 1 Time (s) 0. 15 0. 2 12 Transferred blast load Applied blast load 10 Forces (k. N) • 8 80 mbar-intensity 6 4 2 0 -2 0 0. 05 Civil-Comp Conference, 2015, Prague 0. 1 Time (s) 0. 15 0. 2 5/8

Confined model reduction • Negligible deformation of block leaf: Due to the limited load-transferring ability of wall ties and enhanced stiffness, the block leaf experiences very small deformations. Civil-Comp Conference, 2015, Prague 6/8

Confined model reduction • Negligible deformation of block leaf: Due to the limited load-transferring ability of wall ties and enhanced stiffness, the block leaf experiences very small deformations. • Distributed deformation in brick leaf: Deformation along restrained edges and central vertical line. Civil-Comp Conference, 2015, Prague 6/8

Confined model reduction • Negligible deformation of block leaf: Due to the limited load-transferring ability of wall ties and enhanced stiffness, the block leaf experiences very small deformations. Distributed deformation in brick leaf: Deformation along restrained edges and central vertical line. • Ductile response: As intensity increases from 100 mbar to 600 mbar, quasi-static response is observed Brick leaf displacement (mm) • Out-of-plane displacement at the top of the brick leaf 3. 5 100 mbar 3 400 mbar 2. 5 600 mbar 2 1. 5 1 0. 5 0 0 0. 05 Civil-Comp Conference, 2015, Prague 0. 1 Time (s) 0. 15 0. 2 6/8

Contents • Reduced models of masonry cavity cladding • Modelling techniques • Responses of the reduced models under blast loading • Comparison of the reduced models against a complete model Civil-Comp Conference, 2015, Prague 2/8

Verification against complete model Complete model 6 m Unconfined reduction Confined reduction Applied blast load Complete model - transferred blast load Unconfined simplification -transferred load Forces (k. N) 15 Wpl 1(N/mm) 12 9 6 3 0 0 0. 02 0. 04 0. 06 Time (s) Civil-Comp Conference, 2015, Prague 0. 08 0. 1 7/8

Verification against complete model Complete model 6 m Confined reduction Unconfined reduction Civil-Comp Conference, 2015, Prague 7/8

Verification against complete model Complete model 6 m Unconfined reduction Confined reduction Applied blast load Complete model - transferred blast load Confined simplification - transferred blast load 12 Forces (k. N) 20 15 10 5 0 -5 -10 0 0. 05 0. 1 Time (s) 0. 15 Transferred blast load 25 Confined reduction Left edge Right edge Base edge 10 8 6 4 2 0 -2 0 0. 05 -4 Civil-Comp Conference, 2015, Prague 0. 15 Time (s) 7/8

Verification against complete model Applied and transferred blast loads of the complete model 60 Transferred blast load 50 Applied blast load Forces (k. N) 40 30 20 10 0 -10 -20 0 0. 05 0. 15 Time (s) Civil-Comp Conference, 2015, Prague 8/8

Thank you for your time and attention J. Gu, L. Macorini, B. A. Izzuddin Computational Structural Mechanics Group Civil and Environmental Engineering Department Imperial College London