Bulletin of Earthquake Engineering最新文献

Jerk is the rate of change of an object’s acceleration in time. In this paper, an examination of the influence of jerk on the damage of RC frame buildings exposed to seismic actions was performed. First, the possibilities for jerk determination, when sensors are unavailable, were discussed. The research was conducted by using the experimental data, obtained from three RC frame buildings exposed to shake table tests. Two 3-story and one 5-storey building, tested at the E-Defense facility in Miki City, Hyogo, Japan, were considered. Peak absolute jerks in the considered buildings were presented and analyzed. Among others, it was found that there is no obvious correlation between the times at which peak absolute accelerations and jerks occur. In some cases, peak values occur at similar time instances, whereas in others they are related to quite different ones. Afterwards, jerk energy, its curvature, and novel damage index, were introduced and explained, and a proposal of a new method for the structural damage assessment and classification was provided. Its practical application was demonstrated on the three considered RC frame buildings, and promising results were obtained and discussed in the paper. The proposed method is quite straightforward; it can provide a quick assessment of the structural response in terms of nonlinearity and damage, both for the foundations and superstructure; and it can contribute to the further development of structural health monitoring techniques.

Following the February 6, 2023, earthquakes in Türkiye, visible damage reports were received from the historical Antalya Clock Tower. Initial field assessments revealed several structural cracks, and eight of these were selected for long-term monitoring. During this period, both free and forced vibration data were collected using triaxial accelerometers to better understand the tower’s dynamic characteristics. After approximately one month, the observed crack propagation indicated a rapid degradation of structural integrity, prompting the implementation of an emergency strengthening intervention. Temporary confinement elements were installed to stabilize the structure and prevent further deterioration. Subsequently, Ground Penetrating Radar (GPR) surveys and in-situ material tests were conducted to identify internal voids and evaluate the existing masonry properties. Using the data obtained, a detailed finite element model of the tower was created. This model was first calibrated using the recorded vibration data, and then subjected to a series of analyses to investigate seismic behavior. Response Spectrum and nonlinear Pushover analyses were performed to evaluate the tower’s performance and to guide the design of a permanent strengthening strategy. The selected solution involved externally wrapping the tower with carbon fiber composite ropes and filling cracks and voids with injection grout. The number, diameter, and layout of the ropes were optimized through parametric simulations and then implemented on-site. Post-strengthening monitoring confirmed the effectiveness of the intervention, as no further crack widening was detected. This study presents a complete assessment, analysis, and strengthening process for a historical masonry tower, emphasizing the critical role of staged diagnostics and advanced numerical modeling in heritage conservation.

The quantitative characterization of post-earthquake functional loss and dynamic recovery processes in RC frame structures is the cornerstone for evaluating their seismic resilience. In this paper, a quantitative model for assessing functional loss in RC frame structures is established, spanning from the component to the floor and the structural scale, by analyzing the hierarchical transmission mechanism of functional loss. Additionally, a simulation of the recovery process is conducted using time progression and benchmark algorithms to obtain a complete functional recovery curve. Based on this, an assessment method for the seismic resilience of RC frame structures is established, using functional loss, repair time, and repair rate as metrics. Subsequently, the RC frame structures with different numbers of floors and fortification intensities are built using OpenSees software. The influences of various parameters on the seismic resilience of RC frame structures are analyzed. The results show that as the seismic design intensity increases, both the functional loss and repair time of the structure continue to grow, while the repair rate remains approximately equal under large earthquakes and super earthquakes but relatively slow under moderate earthquakes. Under the same seismic design intensity, the functional loss and repair time of the 6-degree (0.05 g) and 7-degree (0.10 g) fortification structures are significantly lower than those of other fortification structures, while the functional loss and repair time of the 7-degree (0.15 g) fortification structure are the largest. The repair rates of structures across different fortification intensities remain approximately equal. As the number of floors increases, the repair time of the structure tends to rise, while the functional loss and repair rate tend to decrease. The research results can provide a reference for the seismic resilience evaluation of offshore urban systems and the realization of the national resilience urban-rural development goals.

A significant part of the European building stock is outdated and seismically vulnerable, particularly in earthquake-prone regions such as Slovenia. Masonry buildings, which make up approximately 65% of Slovenia’s building stock, are especially at risk. To better understand how retrofitting can reduce seismic vulnerability, this study introduces a parametric pushover curve (PPC) and fragility model for retrofitted masonry buildings. The PPC model relies on a set of parameters for both existing and retrofitted masonry buildings, providing a tri-linear pushover curve. It can be used to plan retrofitting measures such as mortar grouting/repointing, jacketing, or reinforced jacketing combined with vertical ties. While the introduced model is relatively general, its applicability throughout Europe depends on the level of detail used in assessing the model’s input parameters, which are influenced by construction practices across different regions and time periods. In this study, the parameters were assessed based on construction and retrofitting practices in Slovenia, assuming limited knowledge of the building structure, which relies on building-specific data from the public real estate register. This approach enabled the assessment of seismic retrofitting impacts on several thousand masonry buildings. The estimated parametric pushover curves indicate that retrofitted buildings exhibit greater seismic resistance, as reflected in damage-state peak ground acceleration values, with improvements varying by retrofit method and construction period. Repointing/grouting and jacketing provide moderate enhancements, while reinforced concrete jacketing and vertical ties offer the most significant improvements, particularly in preventing collapse-level damage states. Additionally, the model enables the definition of fragility curves at the building class level, including estimates of the standard deviation of the logarithmic values of damage-state peak ground accelerations. A slight decrease in this standard deviation was observed in retrofitted buildings, particularly in multi-storey structures.

Nepal’s earthquake risk is intensified by rapid urbanization, substandard construction practices, limited preparedness, and vulnerable reinforced (RC) buildings. Many RC structures are either non-engineered or built using outdated Mandatory Rules of Thumb (MRT) (NBC 205:1994), termed “pre-engineered”, which no longer meet current standards. The Gorkha earthquake exposed severe vulnerabilities, highlighting the need for retrofitting interventions to enhance seismic resilience. While previous studies assessed existing low- to mid-rise RC buildings, significant gaps remain in the application of conventional methods, open-source software, and cost-effective retrofitting schemes that incorporate both traditional and innovative techniques across diverse building typologies. This study selected six typical buildings including symmetrical, plan-irregular, and vertically irregular structures of three- and four-stories. The seismic vulnerability of non-engineered and pre-engineered buildings within these typologies was assessed through non-linear static and dynamic analyses performed in OpenSees. Retrofitting methods, including RC jacketing, Steel jacketing, and Fiber-reinforced cementitious matrix (FRCM) including Glass FRCM and Hemp FRCM, were applied to upgrade these structures to meet the latest seismic design code NBC 105:2020. Incremental dynamic analysis (IDA) was conducted, and fragility functions were derived for each building model before and after retrofitting. The findings indicated that retrofitted models exhibited higher ductility and lateral load-carrying capacity, reduced inter-story drifts, and delayed damage onset under increasing seismic loads, thereby meeting current code requirements. At 0.4 PGA, the probability of exceeding the life-safety limit state decreased from 100% to 45% in non-engineered buildings and from 90% to 38% in pre-engineered buildings. Glass-FRCM was the most effective, while Hemp-FRCM was least effective. Irregular structures required more extensive retrofitting than symmetrical ones.

Seismic risk analysis is crucial for assessing and mitigating the impacts of earthquakes on infrastructure. A fundamental component of this analysis involves the selection of hazard-consistent ground motions that exhibit good consistency with seismic hazard curves over various periods and encompass a wide range of hazard levels. Traditional methods for selecting such hazard-consistent ground motions often have limitations, typically maintaining consistency at only a limited number of periods and using discrete intensity levels, potentially leading to inaccurate risk assessments. This study proposes an innovative methodology that overcomes these limitations by employing equivalent earthquakes, which are derived from specialized seismic hazard disaggregation techniques. Unlike traditional methods that focus on a target response spectrum corresponding to a specified hazard level, this new method utilizes seismic hazard curves at multiple periods as the primary targets. The ground motions selected using this method cover a wide range of seismic hazard levels, with particular emphasis on higher hazard levels associated with rare events. Numerical examples in the study demonstrate that ground motions selected by the proposed method maintain robust consistency with the site-specific seismic hazard curves over various periods. Importantly, the proposed method is independent of the fundamental periods of specific structures, allowing for its application in accurate seismic risk analyses for various buildings at the same site. This comprehensive methodology is expected to enhance the field of seismic risk analysis by improving the accuracy and applicability of hazard-consistent ground motion selection. However, it is important to note that the proposed method is designed for risk-based applications, where a larger number of ground motions are selected. One limitation of the method is that it may not be as practical for intensity-based assessments.

In existing pre-disaster earthquake reconstruction cost estimation methods, the basic assumption is that the building meets building code standards. However, in Indonesia, many buildings do not meet these standards, requiring a special approach. One such approach is to categorize buildings based on damage levels that follow standardized damage criteria. The main objective of this research is to identify the cost drivers of earthquake rehabilitation and reconstruction at each level of damage. This research uses multiple linear regression analysis models for each damage level (light, medium, and heavy). The regression analysis was conducted on 79 public buildings (schools, clinics, and government buildings) from post-earthquake reconstructions in Lombok in 2018 and Mamuju in 2021, Indonesia. The results show that, at the light damage level, variable cost drivers were identified as seismicity, building occupancy level, total floor area, reconstruction duration, and total reconstructed ceiling area. At the moderate damage level, the identified variable cost drivers were seismicity, building occupancy level, reconstruction duration, total reconstructed wall area, and demolition cost per total area. At the heavy damage level, the variable cost drivers identified were seismicity, location class, structure type, total floor area, and total reconstructed wall area. Identifying cost drivers is important for improving the accuracy of pre-disaster estimation models. In addition, the identified cost driver variables also reflect the key variables in the standardized building code that are often not complied with in Indonesia, indicating that regulatory improvements could begin with these variables.

This study proposes an enhanced macroseismic method, based on RISK-UE LM1 Vulnerability Index model, for assessing the vulnerability of social housing buildings constructed between 1950 and 1975, which typically lack seismic provisions, feature repetitive architectural designs, and have either exceeded or are about to exceed their design working life. Initially, a comprehensive review of existing literature was conducted to identify relevant vulnerability parameters for calculating the Vulnerability Index. Huelva, located in southern Spain, was chosen as a pilot city due to the representativeness of its buildings and the availability of original project documents. Analysing these documents, along with microzonation studies and on-site visual inspections, facilitated an understanding of the structural types (primarily reinforced concrete moment-resistant frames or unreinforced masonry walls) and the further analysis of the selected vulnerability parameters. The new method improves upon the original by incorporating several enhancements, like integrating the number of floors into the Type of Soil Modifier, creating a Combined Modifier that amalgamates parameters based on the construction year, defining the Vertical Irregularity Modifier based on the building’s compactness ratio, and introducing a Slope of the Ground Modifier. Additionally, it considers pounding effects solely for staggered floor slabs and features adapted modifier weights for the specific building types. To address potential overestimation caused by summing multiple modifiers, the method employs a modified square root of the sum of squares (SRSS) approach, which provides a more robust estimation of their combined impact. The method was applied to buildings in Huelva using deterministic (recurrence of the 1755 Lisbon earthquake) and probabilistic (code, intensity VII) scenarios. Results reveal expected damage levels contradicting the damage control philosophy, indicating the need for preventing interventions and further research on similar structures.

On February 6, 2023, the Kahramanmaraş-centered earthquakes caused significant loss of life and extensive structural damage. These events have considerably increased research attention, especially on the seismic performance of retrofitted buildings. This study investigates a school building that was retrofitted in 2020 through the in-plane insertion of reinforced concrete shear walls but collapsed during the 2023 earthquakes. It is a significant case, as it is the only retrofitted building that collapsed according to official records. A comprehensive dataset was collected, comprising retrofitting plans, structural drawings, material and soil properties, and structural analysis reports. Finite element models of the retrofitted and non-retrofitted structures were developed in ETABS, and nonlinear pushover and time history analyses were performed. Pushover analyses assessed the retrofitting’s engineering suitability, while time-history analyses investigated the collapse mechanisms and overall seismic response. Results were compared in terms of story displacement, drift, forces, acceleration, energy components, and structural performance. Pushover analyses demonstrated up to an 80.6% reduction in both story displacements and drift ratios after retrofitting. However, damage levels in some columns increased, and improvements at upper stories remained limited. Time history analyses revealed reductions in displacement and drift demands of up to 89%, confirming overall performance gains. Stiffness increase caused substantial rises in story accelerations (up to 1600%) and shear forces (up to 70%), particularly in upper floors. These findings indicate that performance limitations stem from both design-related and construction-phase deficiencies. Therefore, future retrofitting strategies should adopt a holistic approach, integrating balanced stiffness distribution, optimized shear wall layout, precise connection detailing, and strict construction quality control.