94 research outputs found
TOWARDS FRAGILITY ANALYSIS FOR CONCRETE BUILDINGS IN FIRE: RESIDUAL CAPACITY OF CONCRETE COLUMNS
Fragility assessment of a RC structure under tsunami actions via nonlinear static and dynamic analyses
Current guidelines for design and assessment of buildings under tsunami actions do not explicitly state how to apply tsunami loads to buildings and which analysis methods to use in order to assess the structural response to the tsunami loads. In this paper, a reinforced concrete (RC) moment-resisting frame, which is designed as a tsunami evacuation building, is selected as a case study and subjected to simulated 2011 Tohoku tsunami waves. To assess tsunami impact on the model building, different nonlinear static analyses, i.e. constant-height pushover (CHPO) and variable-height pushover (VHPO), are compared with nonlinear dynamic analysis. The results of VHPO provide a good prediction of engineering demand parameters and collapse fragility curves obtained from the dynamic analysis under a wide range of tsunami loading. On the other hand, CHPO tends to overestimate interstorey drift ratio (IDR) and underestimate column shear by about 5–20%. It provides a larger fragility, i.e. about 10% in median value, for global failure and a smaller fragility for local shear failure. On the basis of these results, it is recommended that VHPO be used in future fragility analysis of buildings subjected to tsunami. However, pushover methods might not be adequate in cases where the tsunami inundation force time-histories are characterised by a “double-peak”, which subjects the structure to a two-cycle load. Finally, it is found that tsunami peak force is better correlated to IDR than flow velocity and inundation depth for the considered structure. This suggests that the peak force would be a more efficient intensity measure than the other two in the development of tsunami fragility curves
Experimental assessment of the monotonic and cyclic behaviour of exterior RC beam-column joints built with plain bars and non-seismically designed
The seismic behaviour of reinforced concrete structures built with plain reinforcing bars is sometimes conditioned by the slippage between the reinforcing bars and the surrounding concrete in the elements as exterior beam-column joints. The anchorage of the beam reinforcing bars in the core joint with weak concrete confinement, inappropriate reinforcement detailing for seismic loads and poor bond properties are the common reasons for collapse of many structures. This paper presents the results of four unidirectional cyclic tests and two unidirectional monotonic tests carried out on full-scale exterior beam-column joints built with plain and deformed reinforcing bars. These specimens are representative of reinforced concrete structures built without adequate reinforcement detailing for seismic loads. The influence of bond properties, lapping of the longitudinal bars, anchorage of the beam reinforcing bars and loading on the beam-column joints response are investigated
Seismic performance of fire damaged structures: preliminary analysis of a 14-story case study structure
Fires in residential buildings are one of the major and most frequent disasters affecting
urban areas. Most fire-damaged buildings are repaired after the fire rather than demolished and
replaced. In case of extreme fire events, the decision to repair the building usually involves
extensive engineering investigation including materials testing and detailed damage assessment.
However, these are often disregarded in case of small to medium size fires, where damage to
structural elements may be less visible. In these cases, the repair process focuses on reinstating
the aesthetic appearance of the building with limited consideration of how the strength of fireaffected structural elements may have been degraded. But what if the fire-affected building is
sited in a seismic area? How will a fire-damaged building perform under seismic loading? The
present paper presents an initial study that looks to help answer these questions. The paper
evaluates the seismic performance of a typical high-rise reinforced concrete building in Istanbul
(of tunnel-form construction), considering several fire damage scenarios. This region is
considered for case study purposes due to its high seismic hazard and the high number of
residential fires experienced every year (according to the data published by the Istanbul Fire
Brigade). The case study structures are modelled in OpenSeesPY, with fire damage modelled
considering deterioration in the material properties of the structural components under different
scenarios of fire intensity and spread within the building. Nonlinear time history analyses are
performed on the undamaged and fire-damaged structures to investigate the changes in the
seismic response. The results highlight the increased seismic vulnerability of the fire-damaged
structures and provide insights into which fire scenarios most affect the structure's seismic
performance
Governance, resilience, and justice. A conversation with the Chilean earthquake engineering community
This article explores the space that a justice narrative has within the earthquake engineering community (EEC)
in Chile. Following a set of semi-structured interviews, we discuss the understanding that the EEC has of
seismic risk governance and its relationship with disaster risk management. As such, it partly provides a selfreflection of the EEC about its historical development, current challenges, and future directions. Preliminary
results show that the narrative of resilience appears as the current challenge to rethinking earthquake
engineering practice, pushing for a paradigmatic shift from lifesaving to damage prevention. Topics beyond
the traditional scope of engineering practice such as the political dimension of technical decisions and the
concept of seismic justice are understood as relevant and valuable, yet its practical application remains unclear
and therefore distant
Tsunami fragility curves of a RC structure through different analytical methods
Recent tsunami events have stimulated research activity into tsunami fragility functions which have been largely based
on empirical data. However, empirical fragility functions are biased because the influence of earthquake and tsunami
damage are difficult to separate. We develop a new theoretical framework to assess the structural performance of a
building due to tsunami inundation by drawing on recent experimental and theoretical progress at UCL on building.
Different nonlinear static analyses, i.e. constant-height pushover (CHPO) and variable-height pushover (VHPO), are
compared with nonlinear dynamic analysis in assessing the fragility curves of a case study structure for a set of realistic
tsunami wave traces. The results of VHPO provide a good prediction of collapse fragility curves obtained from the
dynamic analysis under a wide range of tsunami time-histories. On the other hand, CHPO provides a larger, i.e. about
10% in median value, fragility in case global failure is considered and a smaller fragility for local shear failure. On the
basis of these results, it is recommended that VHPO be used in future fragility analysis of buildings subjected to tsunami
Impact of corrosion deterioration on the seismic performance of steel frame structures
Steel structures designed before the introduction of modern seismic design codes may
be characterised by high seismic vulnerability due to their reduced ductility capacity. Additionally,
these structures may be affected by significant corrosion deterioration, as one of the major
atmospheric degradation phenomena when built in corrosive environments. Corrosion
deterioration leads to a thickness reduction of sections, reduced bearing capacity, stiffness
degradation and loss of energy dissipation capacity. Thus, old-corroded steel structures located
in seismically active regions could experience a reduction of their seismic performance,
significantly increasing the failure probability under earthquake events. The present study
investigates the effect of atmospheric corrosion deterioration on steel frames and uses a nonseismically designed three-storey moment-resisting frame for case-study purposes. Atmospheric
corrosion models based on the recommendation of ISO 9224:2012 have been adopted
considering a 50-years ageing time and modelled as uniform corrosion on steel members. A
probabilistic seismic performance assessment of the pristine and ageing steel frames is
performed through Incremental Dynamic Analyses (IDAs). IDAs are performed for a set of 43
ground motion records accounting for the influence of the earthquake input’s uncertainty (i.e., the
record-to-record variability). The corrosion effects on the seismic performance are evaluated by
monitoring both global and local engineering demand parameters (EDPs), allowing the
development of seismic fragility functions at components- and system-level
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