Filipe L. A. Ribeiro

Conventional seismic design methods rely on structural inelastic hysteretic response to dissipate seismic energy. This approach often results in extensive damage and substantial direct and indirect losses following high-intensity earthquakes, thereby affecting the overall resilience of communities. To address this issue, modern earthquake engineering is facing an extraordinarily challenging era in providing affordable, high-seismic-performance structures able to minimise both seismic damage and repair time. To this end, the ERIES SC-RESTEEL (Self-Centring seismic-RESilient sTEEL structures) project examines the structural response, repairability, resilience, and performance recovery of low-damage self-centring steel Moment-Resisting Frames (MRFs) equipped with friction devices and post-tensioned bars with disc springs at column bases and beam-to-column joints. Shaking table tests will be conducted at LNEC (Laboratório Nacional de Engenharia Civil) in Lisbon, Portugal, to investigate the performance of a large-scale 3-storey steel MRF. Key objectives include evaluating the seismic performance of the structure, its reparability strategy, and the performance after repairs. This paper presents the test specimen design, advanced Finite Element analyses of various joint configurations, and the preparatory work for the tests. The findings offer valuable insights into the expected experimental outcomes.

North Macedonia lies near the boundary between the Eurasian and African tectonic plates. The movement of these tectonic plates leads to frequent moderate to strong earthquakes, making the Balkan region one of the most seismically active areas in the Mediterranean. In North Macedonia, the Skopje earthquake of July 26, 1963, was one of the most destructive events, causing significant damage and losses to the region's building inventory. It struck Skopje, the most densely populated area of the country.The Skopje earthquake has been extensively studied. However, it has been observed that input parameters (i.e., depth, magnitude, fault kinematics) used in fault modeling vary between different sources, highlighting the lack of consistency in the models used to characterize seismic hazard on the region. These uncertainties are related to the limited availability of seismological information, a problem that generally affects many historical earthquakes. Since fault characterization has a significant impact on surface ground motion and, consequently, on the seismic risk assessment, particular attention must be given to the input parameters used in scenario modeling.This study aims to assess the impact of different modeling approaches regarding the depth, magnitude, and kinematics of the 1963 Skopje earthquake on seismic risk evaluation of the Skopje region. Particular attention is given to the selection of Ground Motion Models (GMMs), as some may not be sensitive to certain parameters under consideration. The exposure model is developed using aggregated data from North Macedonia's latest census conducted in 2021. Vulnerability models for the building typologies identified in the census are derived from the GEM vulnerability database and implemented through a GIS scheme. The uncertainties associated with the exposure and vulnerability models are briefly addressed.The hazard and risk analyses are carried out using the state-of-the-art software, the OpenQuake Engine, and the risk analysis results are ultimately presented in terms of damages to the building inventory, as well as direct and indirect losses.

The safety and resilience of school buildings against natural disasters is of paramount importance since schools represent a reference point for communities. Such significance is not only related to the direct consequences of collapse on a vulnerable part of the population, but also due to the importance of schools in the post-disaster recovery. This work is focused on the risk and resilience assessment of school buildings in Lisbon (Portugal) under seismic events. The results of this study, in which a subset of 32 schools are analyzed, are used to define a prioritization strategy to mitigate the seismic risk of the Lisbon City Council school building portfolio and to assess the overall resilience of the school network. Numerical modeling of the school buildings is performed in order to estimate losses in terms of the built-up area of the schools and recovery times associated with different seismic scenarios, which are probabilistically defined specifically for the sites of the buildings, accounting for the local soil conditions and associated amplification effects. Based on the obtained risk estimates, which are compared to reference values established on international guidelines and specialized literature, the Lisbon City Council and LNEC jointly defined a short- and medium-term risk mitigation plan, starting with a detailed inspection and assessment of the most vulnerable school buildings and continuing to the implementation of retrofitting measures.

Finite-length plastic hinge (FLPH) models have shown advantages over the concentrated plasticity hinge (CPH) models. However, empirical phenomenological relationships, such as Modified Ibarra–Medina–Krawinkler (ModIMK) deterioration model, were mainly calibrated for use in CPH models. ModIMK relationships are versatile and have been applied to steel, reinforced concrete, and timber structures. Herein, a calibration procedure of FLPH models and a unified algorithm for use of ModIMK relationships in CPH and FLPH models are presented. Results from included examples validate the proposed algorithms, which were implemented in OpenSees. Additionally, results highlight that FPLH models avoid errors and convergence pitfalls of CPH models.

Summary: This paper presents an analytical study evaluating the influence of ground motion duration on structural damage of 3‐story, 9‐story, and 20‐story SAC steel moment resisting frame buildings designed for downtown Seattle, WA, USA, using pre‐Northridge codes. Two‐dimensional nonlinear finite element models of the buildings are used to estimate the damage induced by the ground motions. A set of 44 ground motions is used to study the combined effect of spectral acceleration and ground motion significant duration on drift and damage measures. In addition, 10 spectrally equivalent short‐duration shallow crustal ground motions and long‐duration subduction zone records are selected to isolate duration effect and assess its effect on the response. For each ground motion pair, incremental dynamic analyses are performed at at least 20 intensity levels and response measures such as peak interstory drift ratio and energy dissipated are tracked. These response measures are combined into two damage metrics that account for the ductility and energy dissipation. Results indicate that the duration of the ground motion influences, above all, the combined damage measures, although some effect on drift‐based response measures is also observed for larger levels of drift. These results indicate that because the current assessment methodologies do not capture the effects of ground motion duration, both performance‐based and code‐based assessment methodologies should be revised to consider damage measures that are sensitive to duration. Copyright © 2016 John Wiley & Sons, Ltd

The use of empirically calibrated moment-rotation models that account for strength and stiffness deterioration of steel frame members is paramount in evaluating the performance of steel structures prone to collapse under seismic loading. These deterioration models are typically used as zero-length springs in a concentrated plasticity formulation; however, a calibration procedure is required when they are used to represent the moment-curvature (M−χ) behavior in distributed plasticity formulations because the resulting moment-rotation (M−θ) response depends on the element integration method. A plastic hinge integration method for using deterioration models in force-based elements is developed and validated using flexural stiffness modifications parameters to recover the exact solution for linear problems while ensuring objective softening response. To guarantee accurate results in both the linear and nonlinear range of response, the flexural stiffness modification parameters are computed at the beginning of the analysis as a function of the user-specified plastic hinge length. With this approach, moment-rotation models that account for strength and stiffness deterioration can be applied in conjunction with force-based plastic hinge beam-column elements to support collapse prediction without increased modeling complexity

This paper proposes a reliability-based framework for quantifying structural robustness considering the occurrence of a major earthquake (mainshock) and subsequent cascading hazard events, such as aftershocks that are triggered by the mainshock. These events can significantly increase the probability of failure of buildings, especially for structures that are damaged during the mainshock. The application of the proposed framework is exemplified through three numerical case studies. The case studies correspond to three SAC steel moment frame buildings of three, nine, and 20 stories, which were designed to pre-Northridge codes and standards. Two-dimensional nonlinear finite-element models of the buildings are developed with the Open System for Earthquake Engineering Simulation framework (OpenSees), using a finite length plastic hinge beam model and a bilinear constitutive law with deterioration, and are subjected to multiple mainshock-aftershock seismic sequences. For the three buildings analyzed herein, it is shown that the structural reliability under a single seismic event can be significantly different from that under a sequence of seismic events. The reliability based robustness indicator shows that the structural robustness is influenced by the extent to which a structure can distribute damage