Transcript Imperial College London

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
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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
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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
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Partitioned Modelling for Parallel Processing
Case 1:
2: A parent and 2
3:
a
child partitions
partition (Same
(parent
(parent
also
as
has
case
only
models
2partition
buta parent
partsuper
of
structure
and
elements)
child roles
made with
other elements)
reversed)
Placeholder super-element on
parent side
Dual partition super-element
on child side
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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
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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
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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
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Application Study
Identical accuracy for monolithic and partitioned models
Excellent speed-up for partitioned models
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
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
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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
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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