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Partitioned modelling for nonlinear dynamic analysis of RC buildings under earthquake loading. B.A. Izzuddin, L. Macorini and G. Rinaldin www.imperial.ac.uk/csm. Overview. Introduction Nonlinear dynamic analysis of RC buildings Partitioned modelling for parallel processing
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Partitioned modelling for nonlinear dynamic analysis of RC buildings under earthquake loading B.A. Izzuddin, L. Macorini and G. Rinaldin www.imperial.ac.uk/csm
Overview • Introduction • Nonlinear dynamic analysis of RC buildings • Partitioned modelling for parallel processing • Application study • Conclusion
Introduction • Retrofitting and strengthening RC buildings in earthquake regions • Nonlinear dynamic analysis for seismic assessment • Accuracy vs computational demand • Partitioned modelling on distributed memory HPC • Overcoming memory bottleneck for large-scale structures • Reduced simulation time through parallelisation
Nonlinear dynamic analysis of RC buildings • Interactions between frame, floor slabs and lateral resistance system • Geometric and material nonlinearity • Modelling of frame members with 1D elements • Fibre elements with nonlinear material models • Modelling of floor slabs and shear walls with 2D elements • Step-by-step time-integration scheme • Accuracy, stability and dissipation of higher modes (e.g. HHT) • Prohibitive memory and computational demands for real RC buildings
Partitioned Modelling for Parallel Processing Case 2: A parent and a child partition (parent also models a part of structure made with other elements) Case 3: A parent and a child partition (Same as case 2 but parent and child roles reversed) Case 1: A parent and 2 child partitions (parent has only partition super elements) Placeholder super-element on parent side Dual partition super-element on child side
Partitioned Modelling for Parallel Processing • Child partitions represented in parent by placeholder super-elements • Parent and child partitions processed in parallel • Child partition wrapped by dual super-element along interface boundary • Parallelisation through communication between placeholder/dual super-elements • Effective recovery of super-element resistance/stiffness via frontal solution method • Benefits of partitioned modelling approach using distributed memory HPC • Overcoming memory bottlenecks and parallel element computations in subdomains • Additional performance benefits due to parallelisation of frontal solution with reduced front widths
Application Study • Irregular 4-storey RC building • Modelling of beams/columns with 1D elements of fibre-type • Modelling of floor slab diaphragm action using equivalent planar bracing units • Geometric and material nonlinearity • Seismic excitation in two horizontal X-Y directions
Application Study • Three computational models with different number of partitions • Model (A): monolithic (1 process) • Model (B): 4 child partitions (5 processes) • Model (C): 14 child partitions (15 processes) • Partition interface boundaries at column locations for models (B) and (C) • Small number of parent nodes compared to child partitions • Effective for reducing communication overhead between processes • Avoids wall-clock time being imposed by solution of equations at parent level • Ideal speed-up equal to number of child partitions
Application Study • Identical accuracy for monolithic and partitioned models • Excellent speed-up for partitioned models • Exceptional speed-up for Model (C) exceeding number of child partitions • Considerable reduction in front width • Effective implementation of parallel frontal solver on distributed memory HPC systems
Conclusion • Nonlinear dynamic analysis of buildings subject to earthquake loading • Computational demand can be prohibitive for real structures • Partitioned modelling approach for parallel HPC • Based on parent/child partitions and associated processes • Identical accuracy to monolithic approach with use of dual super-elements for recovery of condensed resistance/stiffness at partition interface boundary • Computational benefits in terms of speed-up and overcoming memory bottleneck • Application to 4-storey RC building subject to earthquake loading • Exceptional speed-up of 27 with only 14 child partitions • Additional benefits arising from effective parallelisation of frontal solver leading to reduced front widths • Practical prospect for nonlinear seismic assessment of real structures
Partitioned modelling for nonlinear dynamic analysis of RC buildings under earthquake loading B.A. Izzuddin, L. Macorini and G. Rinaldin www.imperial.ac.uk/csm