Bulletin of Earthquake Engineering最新文献

The shear resistance computed using Annex J of Part 1–1 of Generation 2 of Eurocode 2—on strengthening of RC members for static loads with externally-bonded Fibre-reinforced-polymers (FRPs)—exceeds by about 25% on average the cyclic shear resistance of 64 FRP-jacketed shear-critical RC specimens in the international literature. The semi-empirical cyclic shear resistance approach for FRP-wrapped RC members in Annex A of Part 3 of Generation 1 of Eurocode 8 is in good average agreement with the results of these tests, but conflicts with the rational, mechanics-based approach for shear resistance against static actions in Generation 2 of Eurocode 2, which has already been adopted in Generation 2 of Eurocode 8 for members without FRP jackets, adapted to the specific needs of seismic design. This latter approach is modified and extended to cover RC members with closed FRP jackets in a more technically sound way than in Annex J of Generation 2 of Eurocode 2. The new approach fits the available cyclic test results without bias or lack-of-fit with respect to the key variables controlling cyclic shear resistance, gives slightly better accuracy than the semi-empirical one in Generation 1 of Eurocode 8 and does much better in correctly identifying as not failing in shear FRP-wrapped RC members which have failed in flexure or not failed at all during cyclic testing.

An efficient design method should provide practitioners with a means for sizing timber buildings to meet specific performance levels against estimated earthquake intensities. Displacement and energy design considerations in force-based design (FBD) procedures are not as precise as intended in complex systems, such as mid- to high-rise timber buildings. The main aim of this study is to tailor the direct displacement-based design (D-DBD) classical framework to platform-type cross-laminated timber (CLT) shear wall structural systems and validate their performance for low-rise to high-rise timber mixed-use buildings. A comparison with results obtained via the FBD analyses is also provided. To this end, timber buildings with heights of 4, 8 and 12 stories are designed via the D-DBD and FBD methods. The seismic performance of platform-type CLT wall buildings is assessed in terms of the repair cost, repair time and casualty rate using FEMA P-58 methodology. The seismic response of CLT shear walls shows that the FBD method may lead to an expensive overdesign, especially in high-rise platform-type CLT walls. Conversely, the D-DBD method develops structural systems which can sustain a comparable level of damage from low- to high-rise platform-type CLT walls. Although the seismic loss assessment of buildings shows slightly better performance for the FBD method than the D-DBD method, it is worth noting that the D-DBD method does not lead to an unsafe building. Consequently, the D-DBD method sounds like a proper alternative approach for designing the CLT shear walls to achieve target performance levels without requiring a premium upfront cost.

To enhance the post-earthquake traffic flow capacity of bridge structures, various energy dissipation braces (EDBs) have been developed and applied. However, the effect of various EDBs on the improvement of the post-earthquake functionality of the bridge is difficult to evaluate mainly due to the imperfections in the functional indexes of bridge structures. This study aims to quantify the multi-level residual drift ratios of RC bridge piers based on traffic flow capacity, and to assess the seismic failure of RC bridge piers with different EDBs based on traffic flow capacity. To this end, the traffic flow was categorized into five levels based on the relationship between the traffic flow capacity and the seismic performance of the bridge. The post-earthquake performance states were evaluated on the basis of the residual drift ratio as a performance indicator, and the corresponding residual drift ratio thresholds for bridge structures under different function levels were determined as 0.06%, 0.24%, 0.49%, and 0.85% based on the numerical analysis results. Using traffic flow capacity as the limit states, the failure probabilities of the RC bridge bents with buckling restrained braces (BRBs) and self-centering energy-dissipation braces (SCEBs) were further investigated. The results show that traditional BRBs show better performance with respect to the maximum drift ratio while the SCEBs show better performance with respect to the residual drift ratio. It is indicated that the SCEB is much more effective in improving the repairability and post-earthquake traffic flow capacity of the bridge.

Assessment of liquefaction susceptibility of sediments in alluvial plains is considered one of the first step for infrastructure planning, hazard mitigation, and land use management in seismically active regions. Subtle geomorphological features resulting from depositional processes could greatly contribute to estimating the liquefaction likelihood since they also dictate the type and distribution of sediments. Our case study is from the Piniada Valley (Greece), where widespread liquefaction phenomena were triggered by the 2021 Mw 6.3, Damasi earthquake. As we compiled a detailed geological map for the purposes of this investigation and correlated it to the spatial distribution of the earthquake-induced liquefaction phenomena, we observed that most of liquefaction surface evidence are related to point bars and abandoned river channels formed the last century. In particular, the areal liquefaction density was estimated at 60.7 and 67.1 manifestations per km², for the point bars and abandoned channels, respectively. Following this outcome, we propose a refinement of the existing liquefaction susceptibility classifications by including point bar bodies as a distinct category, characterized by a very high susceptibility to liquefaction. In addition, we discuss the correlation between the observed liquefaction manifestations and the shallow lithofacies, sand or mud prone areas, within point bars. The outcome arisen by this research is that most of liquefaction phenomena (> 70%) occurred on the area covered by coarser materials deposited on the upstream part of high sinuosity meanders.

This research presents an interdisciplinary study on the impact of planning policies on the seismic vulnerability of historic areas, encompassing architecture, urban planning, and engineering aspects. It examines the spatial and temporal dynamics of urbanization and population growth, which alter cities' seismic exposure and vulnerability over time. Urban and engineering research methods are used to assess the seismic vulnerability variability in Yungay Quarter, a historic district west of downtown Santiago, Chile, with buildings constructed between 1839 and 2022. The study begins with a thorough review of Chilean urban planning policies and building regulations, combined with a detailed survey of the construction features in the historical neighborhood to classify building types. Next, the macro-seismic method is applied to a representative sample of 484 buildings to calculate vulnerability indices for unreinforced masonry and reinforced concrete structures, which are then used to estimate damage distributions. Seismic fragility curves for each building class are derived based on peak ground acceleration. These fragility curves are incorporated into risk assessments for potential ruptures along the San Ramon, Santiago splay and a deep intra-slab splay fault. The resulting risk scenarios can guide future urban planning policies and processes affecting this historical urban center. The innovations introduced by this work include a summary of how changes and updates to planning policies have influenced construction practices in the Yungay Quarter from 1839 to 2022 and the translation of these urban changes into variations in building fragility functions, enabling a comprehensive assessment of the potential impacts on these buildings from various potential.

Estimating earthquake ground motions at reference bedrock is a major issue in site-specific seismic hazard assessment. Deriving or adjusting empirical ground motion models (GMMs) for reference bedrock is challenging and affected by large epistemic uncertainties. We propose a methodology to simulate region-specific reference bedrock time histories by combining spectral decompositions of ground motions with Empirical Green’s Functions (EGFs) simulation technique. First, we adopt the nonparametric spectral decomposition approach to separate the contribution of source, path, and site. We remove the average source and site effects from observed small-magnitude recordings in the target region through deconvolution in the Fourier domain. This way, the obtained deconvolved EGFs represent path term only. Then, we couple the EGFs with k^− 2 kinematic rupture models for target scenario events. For each target magnitude, a set of rupture models following a ω-squared source spectrum are generated sampling the uncertainties in kinematic source parameters (e.g., slip distribution, rupture velocity, hypocentral location, stress drop, and rupture dimensions). The proposed approach is validated using recorded ground motions at reference sites from multiple earthquakes in Central Italy. The power of this approach lies in its ability to map the path-specific effects into the ground-motion field, providing 3-component time histories covering a wide frequency range, without the need for computationally expensive approaches to simulate 3D wave propagation. The region-specific, site-effects-free dataset produced by this approach can be used alone or in combination with existing empirical datasets to adjust existing GMMs, derive new GMMs, or select hazard-consistent time histories to be used in soil and structural response analyses.