partitioned modelling for nonlinear dynamic analysis of rc buildings under earthquake loading b.a....
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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
2CC2013 – Cagliari
Overview
Introduction
Nonlinear dynamic analysis of RC buildings
Partitioned modelling for parallel processing
Application study
Conclusion
3CC2013 – Cagliari
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
4CC2013 – Cagliari
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
Nonlinear dynamic analysis of RC buildings
5CC2013 – Cagliari
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)
Partitioned Modelling for Parallel Processing
Placeholder super-element on parent side
Dual partition super-element on child side
Case 1: A parent and 2 child partitions (parent has only partition super elements)
6CC2013 – Cagliari
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
Partitioned Modelling for Parallel Processing
7CC2013 – Cagliari
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
8CC2013 – Cagliari
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
9CC2013 – Cagliari
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
Model Child partitions
Maximum front width
Wall-clock time
Speed-up
Monolithic (A) - 318 13hr 37min -
Partitioned (B) 4 510 4hr 45min 2.89
Partitioned (C) 14 198 0hr 30min 27.3
10CC2013 – Cagliari
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