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