Seismic Analysis and Fragility Assessment of Masonry Infilled Steel
Frame Structure by means of Incremental Dynamic Analysis (IDA)
and Cloud MethodMSc Civil Engineering (with Seismic Design)
Biao Song
Supervisor: Prof Dina D’Ayala
Over the past few decades, a large number of masonry infilled frame
structures have been built in seismic-prone regions around the world
with the advantages such as light weight, fast installation and cost
efficiency. During the past earthquakes, these structures have
constituted a significant part of high risk constructions in urban and rural
areas. However, based on traditional design, the masonry infills in steel
frames are considered as non-structural components and their influence
in providing stiffness and strength to the whole system is ignored by
engineers.
Therefore, this study aims to investigate the seismic behaviour of low-
rise and mid-rise steel frames with masonry infill walls by means of
Incremental Dynamic Analysis (IDA) and Nonlinear Time History
Analysis (NLTHA) based Cloud Analysis.
Methodology
Introduction & Main Aim
Design & Modelling
10 groups of models with different geometric properties have been
designed using ETABS 2015. In each group, the followings have been
considered:
Design codes: gravity design code (low code) and seismic design
code (high code);
Structural systems: moment resisting frame (MRF) and concentrically
braced frame (CBF).
Then, these models have been realised and analysed in SeismoStruct
(v.7) by considering the presence of masonry infills.
Selection of Earthquake Records
IDA & Cloud Analysis Results
Fragility Analysis ResultsBased on IDA Results
Based on Cloud Analysis Results
Selection of Damage Threshold
Damage States
Model 10 (MRF)Slight Moderate Extensive Complete
HAZUS 0.4 % 0.8 % 2 % 5.33 %
Manually defined
from SPO0.91 % 2.09 % 3.66 % 4.8 %
Discussion and Conclusion
Masonry infills can increase the lateral stiffness and strength of the
steel frame structures in a large extent and therefore the fragility
performance of them can be improved.
Considering the equivalent lateral loads in design stage (seismic
code) can enhance the lateral resistance, ultimate capacity and then
fragility performance of steel frame structures.
The steel grades only affect the strength of the steel frame structures.
The fragility curves have high sensitivity to the capacity of the whole
steel frame structure and the values of damage thresholds selected.
Design in ETABS 2015
Modelling and
analysing
models with
and without
masonry infills
in
SeismoStruct
(v.7)
