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Currently available performance-based methodologies for assessing the fragility of structures subjected to tsunami neglect the effects of tsunami-induced vertical loads due to internal buoyancy. This paper adopts a generalized methodology for the performance assessment of structures that integrates the effects of buoyancy loads on interior slabs during a tsunami inundation. The methodology is applied in the fragility assessment of three case-study frames (low, mid and high-rise), representative of existing masonry-infilled reinforced concrete (RC) buildings typical of Mediterranean region. The paper shows the effect of modelling buoyancy loads on damage evolution and fragility curves associated with different structural damage mechanisms for existing RC frames with breakaway infill walls including consideration of blow-out slabs. The outcomes attest that buoyancy loads affect the damage assessment of buildings during a tsunami, especially in the case of mid and high-rise structures with blow-out slabs. The rate of occurrence of slabs uplift failure increases with the number of stories of the building, indicating the need to account for such damage mechanism when assessing the performance of structures. It is also found that buoyancy loads slightly affect the fragility curves associated to other structural damage mechanisms for existing RC buildings commonly monitored for fragility assessment. [ABSTRACT FROM AUTHOR]

The behaviour of pre-code reinforced concrete (RC) columns in sequence of fire and earthquake is not well understood and can be critical in case of buildings which experienced fire and are either unrepaired or poorly repaired when exposed to an earthquake. This study proposes a framework on how to construct a simplified model to assess the post-fire cyclic behaviour of such columns. Emphasis is given to the development of simplified material models which can be used to describe the performance of the confined concrete, as its post-fire behaviour is not well studied. The model's performance is validated against the experimental results of a square, non-seismically designed RC column. Three scenarios are considered. The reference scenario, where the column is exposed only to cyclic loading. In the other two, the column is firstly exposed to an ISO-834 time–temperature curves in a furnace of 30 min and 90 min duration and after it cooled down, it is exposed to cyclic loading. The results showed that simplified material models can be used to capture the post-fire cyclic behaviour of an RC column, built without seismic design. It was also found that the confined model adopted played an important role after the peak strength is reached. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of the effect of load path on force-displacement response, damage patterns, and failure modes of slender lightly reinforced concrete (RC) columns. A review of available experimental tests, which include columns subjected to multiaxial loading protocols, is first presented. Next, a new experimental campaign on 18 column specimens tested under constant axial load and lateral displacement-controlled load paths is described. The results of the tests performed confirm that the response under biaxial load paths is qualitatively and quantitatively different from that observed for uniaxial load paths. The first and foremost qualitative difference is that the damage mechanisms change and the failure mode can change as a result. This, in turn, leads to quantitative differences in ultimate and collapse deformation, and therefore ductility and hysteretic dissipation capacity. [ABSTRACT FROM AUTHOR]

The new ASCE 7-16 Chapter 6 offers a comprehensive and practical methodology for the design of structures for tsunami loads and effects. While it provides prescriptive tsunami loading and design requirements, Chapter 6 also allows for the use of performance-based nonlinear analysis tools. However, the specifics of load application protocol and system and component evaluation for such a nonlinear approach are not provided. This paper presents a procedure for performing nonlinear static pushover analysis for tsunami loading within the framework of the ASCE 7-16 standard. Through this approach, the user can both estimate the effective systemic lateral load-resisting capacity of a building and the local component demand. This enables the identification of deficiencies in structural elements with respect to the ASCE 7-16 standard acceptance criteria. To demonstrate the procedure, a prototypical reinforced concrete multistory building exposed to high tsunami hazard on the US Northwest Pacific Coast is assessed. This is a building with sufficient height to provide last-resort refuge for people having insufficient time to evacuate outside the inundation zone. The results of the nonlinear static pushover analyses show that the structural system has sufficient lateral strength to resist ASCE 7-16 prescribed tsunami loads, but fails the checks for component-based loading, with the exterior ground-story columns observed to fail in flexure and shear. The example demonstrates that use of the tsunami nonlinear static analysis procedure allows the identification of structural deficiencies such that a targeted strengthening of the building can be conducted (i.e., flexural and shear strengthening of the seaward and inland columns for the case study building presented), leading to significantly reduced costs. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a comprehensive comparison of different dynamic and static approaches for assessing building performance under sequential earthquakes and tsunami. A 10‐storey reinforced concrete seismically designed Japanese vertical evacuation structure is adopted as a case study for the investigation. The case study building is first assessed under sequential earthquake and tsunami nonlinear response history analyses: the first time this is done in the literature. The resulting engineering demand parameters are then compared with those obtained when the analysis procedure is systematically simplified by substituting different static approaches for the nonlinear response history analyses in both the earthquake and tsunami loading phases. Different unloading approaches are also tested for the cases when an earthquake pushover is adopted. The results show that an earthquake nonlinear response history analysis, followed by a transient free vibration and a tsunami variable depth pushover, provides the best alternative to full dynamic analyses in terms of accuracy and computational efficiency. This structural analysis combination is recommended and has the advantage that it does not require the tsunami inundation time history to be known in advance. The proposed double pushover approach is instead deemed only suitable for the collapse assessment of regular low to mid‐rise buildings and for the development of collapse fragility functions. An important observation made is that sustained earthquake damage seems not to affect the tsunami resistance of the case study building when the fully dynamic analysis is carried out for the sequential loading. This observation will be the subject of future work. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The seismic damages commonly observed on beam-column joints of old reinforced concrete structures, built with plain bars and without proper detailing, justifies the need to further study the behaviour of this type of structures. The response of these structures when loaded cyclically, as occurs during the earthquakes, is partially controlled by the bond properties between the reinforcing bars and the surrounding concrete. This paper presents the results of an experimental campaign of unidirectional cyclic tests carried out on six full-scale beam-column joints built with plain bars. These joint specimens are representative of existing reinforced concrete structures, that is, built without adequate reinforcement detailing for seismic demands. For comparison, an additional specimen is built with deformed bars and tested. The seven specimens are designed and detailed to allow the investigation of the influence of bond properties, lapping of the longitudinal bars in columns and beams, bent-up bars in the beams, slab contribution and concrete strength. The lateral force-drift relationships, global dissipated energy evolution, contribution of the joint, beams and columns to the global dissipated energy, ductility, equivalent damping, final damage observed, homogenized reinforced concrete damage index, displacement components, curvature evolutions and Eurocode requirements are presented and discussed. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

• Different response of reinforced concrete frame to earthquake and tsunami. • The prior earthquake slightly influences the earthquake-tsunami fragility curves. • Column shear failure is found to govern collapse mechanism under tsunami. Many coastal regions lying on subduction zones are likely to experience the catastrophic effects of cascading earthquake and tsunami observed in recent events, e.g., 2011 Tohoku Earthquake and Tsunami. The influence of earthquake on the response of the structure to tsunami is difficult to quantify through damage observations from past events, since they only provide information on the combined effects of both perils. Hence, the use of analytical methodologies is fundamental. This paper investigates the response of a reinforced concrete frame subjected to realistic ground motion and tsunami inundation time histories that have been simulated considering a seismic source representative of the M9 2011 Tohoku earthquake event. The structure is analysed via nonlinear time-history analyses under (a) tsunami inundation only and (b) earthquake ground motion and tsunami inundation in sequence. Comparison of these analyses shows that there is a small impact of the preceding earthquake ground shaking on the tsunami fragility. The fragility curves constructed for the cascading hazards show less than 15% reduction in the median estimate of tsunami capacity compared to the fragility functions for tsunami only. This outcome reflects the fundamentally different response of the structure to the two perils: while the ground motion response of the structure is governed by its strength, ductility and stiffness, the tsunami performance of the structure is dominated by its strength. It is found that the ground shaking influences the tsunami displacement response of the considered structure due to the stiffness degradation induced in the ground motion cyclic response, but this effect decreases with increasing tsunami force. [ABSTRACT FROM AUTHOR]

A significant number of existing reinforced concrete building structures were designed and built before 1970, prior to the enforcement of modern seismic design codes. The response of these structures when subjected to cyclic loads, such as that induced by earthquakes, is strongly influenced by the bond properties between the reinforcing bars and the surrounding concrete. This paper describes the results of a testing campaign composed of seven unidirectional cyclic tests and one monotonic test performed on full-scale columns built with plain bars, without adequate reinforcement detailing for seismic demands. An additional unidirectional cyclic test was carried out on a specimen with deformed bars for reference. The influence of bond properties, a cold joint at the base, lapping of longitudinal reinforcing bars, amount of reinforcing steel, cross-section dimensions and imposed loading history (monotonic or cyclic) is discussed. Finally, a correction coefficient to the expressions of EC8-3 for the calculation of ultimate rotation capacity of columns with plain reinforcing bars is proposed. [ABSTRACT FROM AUTHOR]

• Considering slab and transverse beams in testing existing structures is crucial. • They significantly affect load carrying capacity and failure mechanism. • FRP retrofit effectiveness is higher for less realistic beam-column joint geometries. • Practical aspects of retrofit application need to be considered. • Realistic specimens can be effectively strengthened by the proposed retrofit scheme. The seismic behaviour of reinforced concrete (RC) structures is critically influenced by the complex mechanical interactions at beam-column joints. To ensure the desired hierarchy of failure is achieved when retrofitting existing structures, numerical and experimental assessments need to represent realistic structures. A review of published literature indicates that most experimental work on the seismic behaviour pre-1970′s RC beam-column connections considers sub-assemblies without slabs or transverse beams, which are unrepresentative of reality. To evaluate the effect of these elements on the failure mechanism, retrofit need and retrofit effectiveness, experiments on four full-scale beam-column joints are carried out. Two specimens with and without slab and transverse beams, are tested in their as-built and FRP strengthened configurations. As expected, the experimental results demonstrate that the progression of damage and failure mechanisms differ significantly when slabs and transverse beams are present, confirming previous numerical and experimental evidence on the strong contribution of these elements on the overall joint behaviour. Moreover, a significantly higher retrofit effectiveness is observed for the specimen without slab and transverse beam. This implies that experiments on retrofitted joints without slab and transverse beam can lead to a focus on joint shear strengthening alone as they inadequately represent the hierarchy of strengths of the framing members. They can also lead to an overestimation of retrofit effectiveness. These observations have implications when considering common simplifying assumptions made in the numerical modelling of RC moment resisting frames when assessing their seismic performance. [ABSTRACT FROM AUTHOR]

• First experimental ciclic tests performed on RC retrofited columns which have previously suffered damage from realistic fire exposures. • Experimental campaign carried out on six full-scale RC columns with detailing representing existing Mediterranean buildings designed to old seismic codes are subjected to fire and then cyclic loading. • Assessement of a strengthening method used to increase the concrete strength through confinement and to increase the displacement ductility and energy dissipation capacity under seismic loading. • Temperature evolution obtained during the fire exposures in two cross-sections of the columns. • Comparisons of force–displacement global responses, dissipated energy evolutions, strength degradation and observed damage of the tested columns. A structure, during its life, may be subjected to multiple hazards. These hazards are sometimes combined over a short period of time, or in some cases occur many years apart, with the first hazard influencing the structural response under a second hazard. A reinforced concrete (RC) structure previously damaged by fire and then exposed to seismic loading is one such example. To assess such structures, the effects of fire on the cyclic performance of RC elements needs to be better understood. Moreover, it is also important to develop and validate strengthening methods that can reinstate or improve the seismic performance of fire-damaged RC elements. This paper presents the results of a novel experimental campaign where six full-scale RC columns with detailing representing existing Mediterranean buildings designed to old seismic codes are subjected to fire and then cyclic loading. Four RC columns were damaged after exposure to 30 or 90 min of the ISO 834 standard fire curve in a furnace and then tested under uniaxial cyclic lateral loading up to failure. Two of these columns were repaired and strengthened post-fire with Carbon Fibre Reinforced Polymer (CFRP) wrapping. The strengthening method aimed to increase the concrete strength through confinement, and to increase the displacement ductility and energy dissipation capacity under seismic loading. Two additional control columns, one as-built and another strengthened, were cyclically tested for comparison with the fire-damaged columns. It was found that the 30 min fire exposure resulted in few concrete cracks, whilst cover spalling and general cracking was observed in the 90 min fire exposure. A significant decrease in the displacement ductility and dissipated energy of the columns was observed following fire exposure, even for the 30 min fire. The columns that had post-fire repair and CFRP strengthening, showed better cyclic performance than the control column without fire exposure. It was also found that post-fire strengthened columns may reach similar seismic performance than similarly strengthened columns without previous fire damage. [ABSTRACT FROM AUTHOR]