1. B.A. Izzuddin, L. Macorini and G. Rinaldin www.imperial.ac.uk/csm
Partitioned modelling for nonlinear dynamic analysis of RC buildings under earthquake loading
B.A. Izzuddin, L. Macorini and G. Rinaldin

2. Overview Introduction Nonlinear dynamic analysis of RC buildings
Partitioned modelling for parallel processing
Application study
Conclusion

3. 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

4. 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

5. Partitioned Modelling for Parallel Processing
Case 3: A parent and a child partition (Same as case 2 but parent and child roles reversed)
Case 2: A parent and a child partition (parent also models a part of structure made with other elements)
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

6. 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

7. 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

8. 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

9. 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

10. 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

11. B.A. Izzuddin, L. Macorini and G. Rinaldin www.imperial.ac.uk/csm
Partitioned modelling for nonlinear dynamic analysis of RC buildings under earthquake loading
B.A. Izzuddin, L. Macorini and G. Rinaldin