The role of masonry infill in progressive collapse mitigation of multi-storey buildings
File(s)
Author(s)
Brás Xavier, Helder Francisco
Type
Thesis
Abstract
The research presented in this thesis addresses the influence of non-structural masonry infill on
the resistance of multi-storey buildings to progressive collapse under sudden column loss
scenarios. In particular, the mechanical response of infilled frames in peripheral bays is
investigated within the scope of a design-oriented robustness assessment framework.
A ductility-centred progressive collapse assessment methodology recently developed at Imperial
College is employed as a rational procedure to quantify structural robustness for sudden column
loss. This allows due consideration of structural redundancy, ductility, strength, dynamic effects
and energy absorption capabilities in a unified manner. In this way, robustness quantification is
shifted from typical code recommendations into a sound performance-based mechanical
assessment. The realistic contribution of masonry panels towards collapse arrest is examined
considering the results from full-scale laboratory tests and accurate numerical simulations. Novel
real-scale tests were performed on different two-bay frames with brick-masonry infill subjected to
incremental pushdown deformation, capturing the dominant deformation mode actually found
following removal of an edge column. In these physical tests, it was observed that the failure
mechanisms and damage patterns displayed by the infilled frames under pushdown deformation
are similar to those activated by lateral pushover loading. Chiefly, clear evidence of diagonal
cracking and shear sliding, eventually culminating in crushing of the compressed corners were
recorded during the tests. Different infill configurations were tested, including central openings
and initial gaps between masonry and frame elements. Overall, a global stable response was
observed even at the expense of severe damage in the masonry panels. Importantly, a monotonic
supply of energy absorption was noticed with increasing vertical deformation, which translates
into considerable robustness reserve associated with the confined infill walls. Secondly, advanced
mesoscale finite element simulations were employed in order to capture the complex frame-infill
interaction in the early stages of pushdown response, where it has been observed in a realistic case
study that progressive collapse is effectively arrested at small dynamic deformations, with
minimal damage to the masonry panels and surrounding structural elements. Finally, application
of the robustness assessment framework allowed a critical comparison between the collapse
resistance arising from secondary mechanisms typically considered in this context (such as floor
membrane and beam catenary effects) and that related to the presence of masonry infill. While
the former are quite effective at relatively large deformations, the latter is shown to add
substantial contribution at small displacements.
The conclusions in this thesis are particularly relevant within the context of retrofitting operations
for robustness enhancement of existing structures, as a result of the growing demand for
upgraded resilience of urban infrastructure. On the other hand, due account for masonry infill
subject to proper quality control during the construction process is recommended for rational
robustness design of new buildings.
the resistance of multi-storey buildings to progressive collapse under sudden column loss
scenarios. In particular, the mechanical response of infilled frames in peripheral bays is
investigated within the scope of a design-oriented robustness assessment framework.
A ductility-centred progressive collapse assessment methodology recently developed at Imperial
College is employed as a rational procedure to quantify structural robustness for sudden column
loss. This allows due consideration of structural redundancy, ductility, strength, dynamic effects
and energy absorption capabilities in a unified manner. In this way, robustness quantification is
shifted from typical code recommendations into a sound performance-based mechanical
assessment. The realistic contribution of masonry panels towards collapse arrest is examined
considering the results from full-scale laboratory tests and accurate numerical simulations. Novel
real-scale tests were performed on different two-bay frames with brick-masonry infill subjected to
incremental pushdown deformation, capturing the dominant deformation mode actually found
following removal of an edge column. In these physical tests, it was observed that the failure
mechanisms and damage patterns displayed by the infilled frames under pushdown deformation
are similar to those activated by lateral pushover loading. Chiefly, clear evidence of diagonal
cracking and shear sliding, eventually culminating in crushing of the compressed corners were
recorded during the tests. Different infill configurations were tested, including central openings
and initial gaps between masonry and frame elements. Overall, a global stable response was
observed even at the expense of severe damage in the masonry panels. Importantly, a monotonic
supply of energy absorption was noticed with increasing vertical deformation, which translates
into considerable robustness reserve associated with the confined infill walls. Secondly, advanced
mesoscale finite element simulations were employed in order to capture the complex frame-infill
interaction in the early stages of pushdown response, where it has been observed in a realistic case
study that progressive collapse is effectively arrested at small dynamic deformations, with
minimal damage to the masonry panels and surrounding structural elements. Finally, application
of the robustness assessment framework allowed a critical comparison between the collapse
resistance arising from secondary mechanisms typically considered in this context (such as floor
membrane and beam catenary effects) and that related to the presence of masonry infill. While
the former are quite effective at relatively large deformations, the latter is shown to add
substantial contribution at small displacements.
The conclusions in this thesis are particularly relevant within the context of retrofitting operations
for robustness enhancement of existing structures, as a result of the growing demand for
upgraded resilience of urban infrastructure. On the other hand, due account for masonry infill
subject to proper quality control during the construction process is recommended for rational
robustness design of new buildings.
Version
Open Access
Date Issued
2015-03
Date Awarded
2015-12
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Macorini, Lorenzo
Izzuddin, Bassam A.
Sponsor
Fundacao para a Ciencia e a Tecnologia
Grant Number
SFRH / BD / 70935 / 2010
Publisher Department
Civil and Environmental Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)