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Non-structural elements play a crucial role in the overall seismic performance of buildings, as has been largely demonstrated in recent earthquakes that have stuck densely populated regions. Therefore, the development of performance-based seismic design and assessment methodologies for non-structural elements is becoming an important research topic within earthquake engineering. A crucial aspect in such methodologies is the accurate prediction of the seismic demands acting on non-structural elements in terms of consistent absolute acceleration and relative displacement floor response spectra for the most common types of structural seismic force resisting systems. Masonry-infilled reinforced concrete frames are one of the most common building typologies in high seismicity regions, such as the Mediterranean region. This study proposes a simplified procedure to estimate consistent absolute acceleration and relative displacement floor response spectra in masonry-infilled reinforced concrete frames based on an existing methodology to estimate consistent floor response spectra in bare reinforced concrete frames. Nine archetype masonry-infilled reinforced concrete buildings with different numbers of storeys and arranged with three masonry infill typologies were considered as case-study archetypes, and were used to validate the proposed methodology using nonlinear time history analyses. The proposed procedure can accurately estimate consistent absolute acceleration and relative displacement floor response spectra for masonry-infilled reinforced concrete buildings that respond both in the elastic and nonlinear ranges for all the non-structural period range. The estimates of floor response spectra given by the proposed procedure are fully consistent with the well-known pseudo-spectral relationship for the entire non-structural period range. [ABSTRACT FROM AUTHOR]

This article presents a numerical study on the influence of the anchorage shear hysteresis on the seismic response of nonstructural components (NSC) connected to multi-storey reinforced concrete (RC) buildings, and of the anchorage itself. To cover a variety of different types of shear hysteresis shapes, this contribution considered the experimental results obtained for five types of post-installed anchors. The results were used for calibrating the hysteresis model of the anchorage connecting an ideal NSC with rigid fixture and a 12-storey RC building host-structure. Using a suit of 40 earthquake records and assuming a single NSC at each storey level anchored by a single fastener, a series of non-linear dynamic analyses of the structure-fastener-nonstructural system was carried out. The results showed significant differences in terms of maximum acceleration and force of the NSC and anchorage, respectively, depending on the type of anchor. These seismic demands were sometimes larger than those required by the reviewed code provisions for rigid NSC, but also for the most restrictive code-case for flexible NSC. The results presented different amounts of scatter, mostly related to the size of the annular gap and of the loading stiffness of the anchorage. It is shown that the maximum force achieved by the anchorage is directly related to the peak relative velocity of the NSC within the gap region. It was concluded that the shape of the shear hysteresis of the anchorage highly influences the response of the NSC and the anchor itself and should not be neglected in practice. [ABSTRACT FROM AUTHOR]

This study investigated the seismic demand of continuity plates (CP) in Special Moment Frames (SMFs), including built-up I-shape beams. Six reference experiments for SMF connections were considered, including beams with unequal depths on both sides of the column, to compare the seismic demand for CP with the corresponding value of the AISC code formula. The effects of beam shape properties, connection type, shear strain of the panel zone (PZ), different construction detailing and straight/inclined CP in dual/trapezoidal PZ were included in this study. In addition, companion analytical studies were performed to evaluate CP seismic demand. The results of the experiments and numerical analyses showed that the AISC code underestimates seismic demand for CP in joints with beams having sizes outside the geometries of hot-rolled structural sections. Poor seismic performance of the code-designed CP led to premature yielding and out-of-plane local buckling of CP, which were observed in the reference experiments and confirmed by numerical models. Finally, an equation for CP seismic demand was developed based on findings of this research. It was demonstrated that the proposed seismic demand met the required seismic criteria using this equation, and it also kept CP within the safe structural margins. [ABSTRACT FROM AUTHOR]

As an alternative to conventional seismic force resisting systems, controlled rocking steel braced frames (CRSBFs) can effectively eliminate permanent structural damage after earthquakes. Together with the rocking action in the braced frame, post-tensioning (PT) elements and fuse members are used to provide self-centering and energy dissipation, respectively. This study firstly aims to assess the influence of design parameters related to the fuse and PT materials on the seismic response of CRSBFs. These factors include the yield strength, initial stiffness, and strain hardening ratio of the fuse, the initial force and modulus of elasticity of the PT strands, and the gravity load on the rocking column. Additionally, different analysis cases are considered to include the effects of frame aspect ratio and earthquake intensity level. Nonlinear response history analyses are performed with factor combinations generated using a design of experiment methodology. The second goal of the study is focused on optimizing the seismic response of CRSBFs with respect to the influential factors identified in the sensitivity analyses. Using a response surface methodology and desirability approach, multiple-response optimization is applied to determine the design variable values needed to simultaneously minimize the maximum transient and residual roof drift ratio and peak floor acceleration. Among other results, it is found that the fuse strain hardening ratio and PT strand modulus of elasticity do not significantly influence the seismic response demands in CRSBFs. The results of the multi-response optimization demonstrate that the initial PT force is most useful for minimizing all three seismic response demand parameters. [ABSTRACT FROM AUTHOR]

A quick and accurate estimate of the seismic demand of tall buildings is one of the important issues in the seismic evaluation of buildings. Nonlinear response time history analysis method (NLRHA) is considered as the most accurate and rigorous method, but the computation requirement of NLRHA for tall buildings can be complex and very time-consuming. Whereas the conventional pushover procedure is not capable of reasonably estimating seismic demand of mid and high rise-buildings, due to the oversimplification of conventional pushover approaches and the complexity of seismic performance of buildings. In this paper, a quick, yet effective, method of analysis, named as a spectrum-based pushover analysis (SPA) method, is proposed to estimate the seismic demand of tall buildings. In the SPA procedure, the very complex and complicated dynamic coupling effect of modes of the nonlinear seismic performance of a building is simplified, and the consecutive pushover technique is adopted to consider the simplified coupling effect. Comparison of the results obtained from NLRHA, the modal pushover analysis method, the consecutive modal pushover analysis method and the proposed SPA method is made. It is seen that the SPA method predicted the seismic demand of buildings well, including the inter-storey drift ratio and hinge plastic rotation, which are very close to those of NLRHA. Owing to its accuracy, effectiveness, and spectrum-based calculation procedure, the proposed SPA procedure is considered to be a very promising tool for predicting the seismic demand of tall buildings. [ABSTRACT FROM AUTHOR]

Highway bridges are essential structures in the transportation system of any country in the world. Many highway bridges are reinforced concrete (RC) bridges that were constructed before the 1980s, prior to current seismic regulation codes. The continuous modification of regulation codes makes it necessary to evaluate structures, and in many cases, existing bridges require interventions to increase their seismic capacity. Among the different techniques used to improve bridge capacity, encasing the columns with RC jackets increases the strength and stiffness of the substructure. RC jacketing increases the column cross sections, improves the seismic capacity and reduces the seismic vulnerability of the bridge substructures. This work presents a parametric study to assess the expected demands of seismically deficient medium length highway bridges retrofitted with RC jacketing aimed at determining the best jacket parameters. A suite of twenty strong ground motions, recorded from a subduction seismic source close to the Pacific Coast in Mexico, was selected to characterize the seismic demand. The bridge superstructures are simply supported with five 30 m long spans for a total length of 150 m. The bridge models have five possible pier heights of 5, 10, 15 20 and 25 m and three different jacket thicknesses and steel ratios. Pushover analyses and capacity spectra of the family of accelerograms allow for the determination of the pier demands by obtaining the performance point as the intersection of the capacity and demand curves. The results allow for the determination of the influence of each parameter on the expected seismic behavior of the bridge models, with the aim of selecting the most suitable jacket characteristics to improve the seismic bridge performance. [ABSTRACT FROM AUTHOR]

Nonstructural components (NSCs) should be subjected to a careful and rational seismic design, in order to reduce the economic loss and to avoid threats to the life safety, as well as what concerns structural elements. The design of NSCs is based on the evaluation of the maximum inertia force, which is related to the floor spectral accelerations. The question arises as to whether Eurocode 8 is able to predict actual floor response spectral accelerations occurring in structures designed according to Eurocode 8. A parametric study is conducted on five RC frame structures in order to evaluate the floor response spectra. The structures, designed according to Eurocode 8, are subjected to a set of earthquakes, compatible with the design response spectrum. Time-history analyses are performed both on elastic and inelastic models of the considered structures. Eurocode formulation for the evaluation of the seismic demand on NSCs does not well fit the numerical results. Some comments on the target spectrum provided by AC 156 for the seismic qualification of NSC are also included. [ABSTRACT FROM AUTHOR]

In the paper, five procedures for the assessment of the seismic performance of low-rise RC buildings at different levels of complexity are presented and discussed. They include simple procedures based on methods originally developed in Japan (levels 1 and 2), the N2 method with two variants of the mathematical model (levels 3 and 4), and non-linear dynamic analysis (level 5). The procedures have been applied to seismic assessments of three RC building structures. A small difference between the N2 and NDA results was observed, whereas the results of the procedures at the first two levels are much more conservative. On the other hand, the amount of input data and of computational work increases with the increasing complexity level. Research is still needed on the definitions of capacities, especially the shear capacity of the structural members, and on the capacity of the whole structure. The initial effective stiffness of the structure proved to be the most important quantity which determines the seismic demand. [ABSTRACT FROM AUTHOR]

Infill walls are commonly used in RC frame structures but are neglected in the structural analysis. It is well known that infill walls could have a significant effect on the structural performance of RC frames under seismic actions, as recently occurred in Italy during the L'Aquila event; furthermore, in many cases, the damage to infill walls is due to out-of-plane actions that can pose a risk to human life (falling of heavy parts). The current paper addresses the behavior of out-of-plane infill walls by conducting parametric linear dynamic time-history analyses. The scope of the parametric study is to evaluate the seismic demand of out-of-plane infill walls by considering the variation of the walls' properties and the position in the building. Finally, the code provisions for evaluating the seismic action on the infill walls by equivalent static forces are examined and compared with the analytical results from the detailed dynamic analysis. [ABSTRACT FROM AUTHOR]

Coastal bridges that are exposed to marine environments always suffer serious corrosion, which degrades their structural performance during the long-term service period. This paper investigates the time-dependent seismic demand and fragility of coastal bridges for their residual service life. First, the equal exceeding probability method was established to consider the reduction in the seismic hazard level for the residual service life of the structures. A finite element model of sound and aging structures was built by analyzing the different corrosion characteristics of bridge columns in the atmospheric zone, splash and tidal zone and submerged zone due to chloride penetration in concrete. The incremental dynamic analysis method was adopted to analyze the seismic demand and establish the fragility curves of the sound and aging bridges under both the design spectral acceleration and the reduced earthquake inputs for comparison. The results of this analysis indicate that the seismic demand of the structure significantly decreases, and the probability of failure of the structural system does not support the common opinion of increasing in the residual service period, if the shortening of the service period is considered in the analysis. [ABSTRACT FROM AUTHOR]