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A shake table test using a full-scale 2-story steel moment frame was conducted to investigate the peak floor acceleration (PFA) and the peak component acceleration (PCA), which directly affect the seismic demand on nonstructural elements. The main focus of this study was to evaluate the effects of structural and component nonlinearity on the nonstructural seismic demand. The PFA reduction suggested by ASCE 7-22 to account for structural nonlinearity was shown to be larger than the experimental results for low-to-moderate ductility levels. The analysis on the resonant PCA showed the importance of structural nonlinearity on the elastic CAR (=PCA/PFA). The high resonant PCA around the fundamental period of the elastic test frame (7 times PFA) was effectively decreased as the test frame experienced a moderate level of ductility; PCA was lowered by 36% and 25% on the 2nd and roof floors, respectively. The effect of component yielding on the PCA was evaluated based on the test results of steel racks mounted on flexible and rigid access floors. The PCA reduction depending on the component ductility level was less than the relevant provisions of ASCE 7-22, and the reason was discussed from the perspective of the pinched hysteretic behavior of the tested specimens. [ABSTRACT FROM AUTHOR]

The endurance time (ET) method is an effective dynamic analysis method for seismic response analysis of structures. It has been recently used for analytical fragility analysis. However, the available ET-based fragility analysis methods have two limitations: 1) the prediction error of the structural median responses estimated by the ET method is ignored; and 2) the record-to-record variability inherent earthquake ground motions is not well considered. To overcome the above limitations, another ET-based fragility analysis method is proposed, where only three times of ET nonlinear analyses are required. To do this, three specific endurance time excitation functions (ETEFs) are generated in correspondence to the mean and 16% and 84% percentile of response spectra of a selected suite of ground motion records (i.e. ${\rm{ ETE}}{{\rm{F}}_m}$ ETE F m , ${\rm{ETE}}{{\rm{F}}_{v1}}{\rm{ }}$ ETE F v 1 and ${\rm{ETE}}{{\rm{F}}_{v2}}$ ETE F v 2 , respectively). The structural response under ${\rm{ ETE}}{{\rm{F}}_m}$ ETE F m is used to estimate the median response of structures under the selected suite of ground motion. Moreover, the structural responses under ${\rm{ETE}}{{\rm{F}}_{v1}}{\rm{ }}$ ETE F v 1 and ${\rm{ ETE}}{{\rm{F}}_{v2}}{\rm{ }}$ ETE F v 2 are used to quantify the record-to-record variability in earthquake ground motions. The fragility relationships are developed by both point and interval estimate methods since another logarithmic standard deviation is introduced to account for the difference between the median responses predicted using ${\rm{ ETE}}{{\rm{F}}_m}$ ETE F m and those predicted by the dynamic analysis. To validate the proposed method, two RC frame structures with six and nine stories are taken as the study cases. The fragility results based on the proposed ET-based method and those based on the cloud method are compared. It is found that the proposed ET-based fragility analysis method could generate reliable fragility estimation, whereas requiring limited computation cost. The proposed method would provide another simplified way for the rapid fragility assessment of structures. [ABSTRACT FROM AUTHOR]

This paper develops the probabilistic seismic demand models of circular tunnels under the transversal seismic load. The uncertainties of ground motion, soil profile, tunnel depth, and lining size are considered. Since the quasi-static analyses may significantly underestimate the seismic responses of tunnels, the results of dynamic numerical analyses are adopted to construct probabilistic models that are more accurate. The constructed model is unbiased and can facilitate the fragility analysis of tunnels. As a demonstration, the proposed probabilistic models are used to estimate the seismic fragility curves of a particular tunnel. [ABSTRACT FROM AUTHOR]

An essential and emerging task in the area of performance-based seismic assessment of bridges is to improve the estimation of the seismic demands. Existing research proved that the bridge column is one of the dominant components in estimating the bridge system vulnerability. However, the seismic performance of bridges with tall piers is not deeply investigated yet. This study aims to address this problem through analysis of multi-span concrete box-girder bridges with tall piers. This study implements a clustering algorithm that identifies optimized groupings which can set up the basis to establish the best choice for generating MLPSDMs. The evaluation results implicate better performance of cluster-wise multiple models than a single model to represent the variation in the bridge demands. The insights gained from the findings of this study can pave the way toward a better realization of the seismic performance of bridges having tall piers. [ABSTRACT FROM AUTHOR]

The uplift effects on the seismic demands of flexible SDOF structures rocking on a stiff surface were numerically investigated, under impulse excitations. The final results were represented in the form of spectra for the seismic demands including the foundation rotation angle, structural drift and base shear. Comparing the results indicated that as the normalized natural frequency surpassed a specific threshold, the drift and base shear of the structure allowed to uplift were more than twice those of corresponding fixed-base structure. Moreover, an increase in structural damping did not necessarily reduce the seismic demands of uplifting systems. [ABSTRACT FROM AUTHOR]

In this study is investigated the performance of different glass fibre-reinforced polymer strengthening schemes on infilled reinforced concrete (RC) frames. The main objective was to limit the damage to beam–column joints and inter-storey drift ratios and to protect RC frames against the negative effects caused by infill-RC frame interaction. Five specimens were tested: one without infill and four infilled with full-scale hollow clay block masonry unit, three of which were strengthened with different schemes. Results showed that the beam–column joints could remain undamaged, lateral strength and stiffness were enhanced, inter-storey drift was limited, and new load carrying systems are generated. [ABSTRACT FROM AUTHOR]

In this paper the seismic assessment of rocking masonry walls is evaluated through the displacement-based approach. In particular, a case study is selected to analyse the rocking failure mechanism of the façade of an ancient masonry church, damaged during the 2016–17 Central Italy seismic sequence. For this purpose, a non-linear kinematic analysis is developed to define the load factor at the activation of the failure mechanism and its evolution until collapse, at large displacements. An advanced macro-block model is adopted to take into account the stabilising contribution of frictional resistances exerted by the interlocked walls. The seismic input is described through acceleration-displacement response spectra (ADRS), provided both by seismic codes and selected real accelerograms, and the seismic analysis is addressed according to the capacity spectrum method (CSM), in the form incorporated into the latest Commentary to the Italian Technical Standard for Construction (CNTC19). The capacity is compared with the seismic demand through safety indexes, in terms of both forces and displacements, and the relevant influence of the frictional resistances on increasing the capacity is discussed. Incremental static analysis (ISA) curves are presented as another approach useful to highlight the relation between the peak ground acceleration (PGA) and the displacement demand. [ABSTRACT FROM AUTHOR]

The seismic assessment of a road network depends largely on the characterization of the fragility of its bridge components. The accuracy of bridge seismic demand estimates and the use of proper intensity measures (IM) will significantly influence such task. The available literature has mainly focused on buildings or a limited number of bridge configurations and IMs, which may not be representative for bridge portfolio assessment studies. In this paper, the correlation quality between a larger pool of traditional and innovative IMs and the nonlinear dynamic response of typical Italian RC bridges is investigated to identify the best-performing IMs. [ABSTRACT FROM AUTHOR]

Structural damage during strong ground shaking is associated with both the seismic input energy and the ability of structural components to dissipate energy through viscous damping and inelastic cyclic response. The correlation of the damage potential of ground motions with seismic energy demand is an important element in developing energy-based design methodologies. This article proposes a new measure of the severity of ground motions by introducing the concept of effective cyclic energy (ECE) defined as the peak-to-peak energy demand (sum of hysteretic and damping energies) imposed on a structure over an effective duration that is equivalent to the time between two zero-crossings of the "effective velocity pulse." The proposed energy measure, which is dependent on the characteristics of the ground motion, is shown to be well correlated with peak seismic demand for a range of system parameters. The development of ECE also provides a basis for defining a non dimensional response index (γeff) to quantify the destructive potential of ground motions. The effectiveness of the new index parameter is validated using an extensive set of near-fault accelerograms and also compared to other ground motion severity indices. Finally, ECE demand of a MDOF system is estimated through modal-energy-decomposition of elastic and inelastic SDOF systems, and the concept of ECE spectrum is proposed to estimate the modal target energy demands for performance evaluation of structures. [ABSTRACT FROM AUTHOR]

On September 7, 1999 an earthquake with magnitude MW = 5.9 occurred close to the city of Athens in Greece. More than 80 buildings collapsed, about 150 deaths and hundreds of injuries were reported. Soon after the event a damage investigation was carried out by two of the authors in the most heavily struck areas. The most serious damages were observed in the northern suburbs of Athens, where reinforced concrete frames and masonry buildings represent the prevalent construction systems. The hysteretic energy demands imposed on RC buildings should have been rather severe considering the structural systems characteristics and the inadequate construction details. However, overstrengths, redundancy and especially the presence of infill walls, provided a significant increase of the seismic capacity and contributed to the survival of many buildings. The objective of the present work is to reproduce and analyse the response of typical RC frames subjected to the 1999 Athens earthquake in areas where the observed damage was particularly severe but no recordings of the ground motion were available. After a general overview of the seismotectonic environment, seismological data, observed macroseismic intensities, structural typologies and observed building behaviour, an attempt is made to identify representative excitations in the meizoseismal area. Specifically, the required accelerograms are obtained by modifying available records so as to reproduce a given global energy content and to be consistent with the observed damage. To study the seismic response of RC models, the obtained accelerograms are used to perform nonlinear dynamic analyses. [ABSTRACT FROM AUTHOR]

In this paper, probabilistic seismic demand analysis is adopted to investigate the seismic fragility of a certain typical irregular highway bridge in the Chinese western mountainous areas. Considering the uncertainties of ground motion and structural parameters, the sample library for seismic fragility analysis is constructed aided by Latin hypercube sampling method, and the nonlinear time history analysis for each sample is implemented to achieve the structural dynamic response under the seismic excitation. Moreover, the curvature ductility ratio and the relative displacement are regarded as the damage indexes for pier and bearing, respectively. Furthermore, the fragility nephograms for the whole piers and fragility curves for various critical sections with different damage states are obtained based on a lognormal distribution assumption and the reliability theory. Finally, the bridge system fragility curves are generated through the first-order reliability analysis method. Fragility curves obtained from the above proposed technique can be used to evaluate the seismic performance of irregular bridges, and it can lay a basis for post-earthquake damage assessment. [ABSTRACT FROM AUTHOR]