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Bridges are one of the most critical and costly structures on road networks. Thus, their integrity and operation must be preserved to prevent safety concerns and connectivity losses after seismic events. Recent large-magnitude earthquakes have revealed a series of vulnerabilities in multi-span highway bridges. In particular, skewed bridges have been severely damaged due to their susceptibility to developing excessive in-plane deck rotations and span unseating. Although seismic design codes have been updated to prescribe larger seating lengths and have incorporated unseating prevention devices, such as shear keys and cable restrainers, research on the seismic performance of skewed bridges with passive energy-dissipation devices is still limited. Therefore, this study focuses on assessing the effectiveness of implementing hysteretic dampers on skewed bridges. With that aim, dampers with and without recentering capabilities are designed and incorporated in representative Chilean skewed bridges to assess their contribution to seismic performance. Three-dimensional nonlinear finite element models, multiple-stripe analysis, and fragility curves are utilized to achieve this objective. The results show that incorporating bidirectional dampers can effectively improve the seismic performance of skewed bridges at different hazard levels by limiting in-plane deck rotations independently of their skew angle. Additionally, the influence of external shear keys and damper hysteretic behavior is analyzed, showing that these parameters have a low influence on bridge performance when bidirectional dampers are incorporated. [ABSTRACT FROM AUTHOR]

At present time, ground-motion prediction models neglect the directionality observed in horizontal components of earthquake ground motions, that is, the important changes in ground-motion intensity that occur with changes in azimuth. This study presents an investigation of the directionality of a recently proposed measure of ground-motion intensity during the 6 February 2023, Mw 7.8 Pazarcık and Mw 7.5 Elbistan earthquake doublet in the Kahramanmaraş region of Türkiye, which resulted in the collapse of more than 35,000 buildings and caused almost 60,000 fatalities. The studied intensity measure is referred to as FIV3, which has been shown to be better correlated with structural collapse than the spectral acceleration at the fundamental period of the structure. The improved intensity measure is period-dependent and is computed as the sum of the three largest incremental velocities with the same polarity obtained from the area under segments of a low-pass filtered ground acceleration time series. The following aspects are studied in this article: variation of FIV3 intensity with changes in the orientation; variation of FIV3 intensity with changes in the period of vibration; attenuation of FIV3 intensities with increasing distance; and spatial distribution of the orientation of maximum FIV3 intensity. This study is based on 231 pairs of records from the Mw 7.8 main event and 222 pairs of records from the Mw 7.5 event. Similarly to the directionality of spectral ordinates, it is found that the directionality of FIV3 intensity also increases with increasing period. Strong directionality occurred not only in the near field but up to distances as large as 400 km from the epicenter. The orientation of maximum FIV3 intensity is found to occur close to the transverse orientation, consistent with observations for the orientation of maximum spectral ordinates during strike-slip earthquakes. [ABSTRACT FROM AUTHOR]

Current seismic design codes define safety levels based on the seismic risk of individual structures, such as specifying a maximum probability of collapse in 50 years. The design remains the same whether the structure is located within a sparsely populated area or within a densely populated area provided that both areas have the same seismic hazard. A novel seismic design approach, referred to as regional‐risk‐targeted seismic design is proposed in which the design level is based on a target seismic risk at the regional scale, as opposed to at the individual structure level. The proposed approach, which is aimed at new constructions, allows local governments to define acceptable levels of regional seismic risk and modify the seismic design criteria contained in national standards to satisfy them. As the possible consequences of a seismic event increase at the regional level, the design level becomes more stringent to control the regional seismic risk to acceptable limits. A series of simplifications are considered to facilitate its application. We illustrate the application of the proposed regional‐risk‐targeted seismic design with three examples in the city of San Francisco, California. In these examples, we iteratively compute the modifications to the maximum seismic risk on individual structures required to comply with specific target levels of regional seismic risk. In the proposed approach, the maximum tolerable seismic risk in individual structures depends not only on the seismic hazard at the site, but also on the number of structures and density in the region of interest. It is concluded that the proposed seismic design approach provides a more rational tool for local government officials to set and calibrate seismic design criteria to comply with their locally‐defined acceptable levels of regional seismic risks within a probabilistic risk management framework. [ABSTRACT FROM AUTHOR]

Over the last two decades, the performance-based earthquake engineering (PBEE) framework developed by the Pacific Earthquake Engineering Research (PEER) Center has gained the attention of researchers and practitioners worldwide. This framework was originally focused on quantifying the seismic risk of individual structures. However, with the advent of the "seismic resilience" concept, broader definitions of stakeholders and performance metrics on a regional scale are desirable. In this context, we present a formalized extension of the PEER PBEE framework for its use in groups of structures spatially distributed over a region, herein referred to as RPBEE framework. As an example, we use the RPBEE framework for computing the total number of damaged structures, the expected total economic loss, and the probability distribution of total economic losses within a region. We highlight differences with the original PEER framework and challenges arising from the implementation of the new RPBEE framework for future research and adoption, along with potential ways to overcome them. [ABSTRACT FROM AUTHOR]

We evaluate the relative seismic risk between one- and two-story single-family houses, critically assessing the practice of lumping them into a single class for regional risk assessments. Two-story houses are more flexible and experience, on average, spectral displacements 4.7 times larger than those of one-story houses. Furthermore, two-story houses highly concentrate deformation demands on their first stories, resulting in story drifts 4.6 times larger than those in one-story houses. Therefore, two-story houses experience significantly higher damage, which is consistent with observations after different earthquakes. Results suggest that classification systems should be updated, separating one- and two-story houses into different categories. [ABSTRACT FROM AUTHOR]