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On 1 January, 2024, a moment-magnitude 7.6 earthquake hit Ishikawa Prefecture, located on the main island of Japan facing the Japan Sea. Tsunami followed the strong shaking, and the maximum inundation height was 5.1 m in Shika Town. Strong shaking in Wajima City resulted in widespread damage to buildings and a fire that burnt the Wajima Morning Market. As of 16 February, 241 casualties had been reported, and 42% of them were due to building collapses. In response to all the described damage, a joint field investigation was conducted by Japan and New Zealand. This paper provides an outline of the earthquake and the damage observed in the affected area. [ABSTRACT FROM AUTHOR]

To meet the recent requirements of low-damage design, there is a growing need to retrofit building structures with a self-centering dissipation system. This system serves a dual purpose: reducing lateral drift and providing supplemental damping to enhance the seismic performance of buildings. This research focuses on assessing the efficiency in seismic response of structures retrofitted with an innovative self-centering hysteretic damper called a Self-Centering Disc Slit Damper (SC-DSD). The SC-DSD consists of four slit dampers and pre-compressed Belleville disc springs that provide self-centering and energy dissipation capabilities. This study investigates the SC-DSD’s working mechanism, theoretical formulation, and design method of SC-DSD dampers for their application in multistory building structures. A reinforced concrete (RC) structure is selected as a case study building that is retrofitted with SC-DSDs and conventional slit dampers. Subsequent seismic performance assessments are conducted using detailed pushover to evaluate the global behavior and capacity of the structure used for the design of the damping system. Nonlinear time history analysis is performed to simulate the dynamic behavior of the retrofitted structure under a variety of seismic excitations. This analysis considers a range of ground motion records to capture different intensity levels and frequency content. Comparing these analyses reveals that the designed SC-DSDs effectively reduce seismic responses while minimizing residual displacement up to 95% when contrasted with both the bare structure and the structure retrofitted with conventional steel slit dampers.

Recentering structure with a viscous damping system is an emerging structural system with remarkable seismic resilience. This system can exhibit sufficient energy‐dissipating capacity during a major earthquake and eliminate the residual deformation through recentering mechanism afterward. However, the seismic response of the considered system is still confusing due to its complex dynamic behavior. Thus, it is hard to estimate the peak responses of the system during a major earthquake. This study proposes a simplified analysis method for estimating the peak responses of recentering structures with viscous damping systems based on an equivalent two‐stage substitute model. Considering the considerable strain energy of recentering structures during vibrations, this method proposes to employ effective stiffness based on the equal‐energy principle in an equivalent two‐stage substitute model. Based on this concept, corresponding equations are derived for capturing the peak transient responses of the considered system. Results of response history analysis validate that the proposed method can reasonably estimate maximum relative displacement, relative velocity, and absolute acceleration. Given its satisfactory accuracy, this method is promising while conducting seismic design of recentering structures with viscous damping systems. [ABSTRACT FROM AUTHOR]

The present study developed a method for evaluating the response, damage, and repair cost of super high‐rise reinforced concrete (RC) buildings subjected to large‐amplitude earthquakes. The response was numerically assessed using three‐dimensional 40‐story RC frame models under the predicted seismic motions of earthquakes along the Sagami Trough and Nankai Trough considering the effects of slip behavior, slab cooperative width, and stud‐type dampers. Even when the RC mainframe exhibited slip, the peak response deformation was effectively reduced by the friction dampers incorporated into each story. A probabilistic approach based on fragility was used to evaluate the damage and repair cost of the building models. The distributions of the damage states and repair cost for each story under the predicted seismic motions of earthquakes along the Sagami Trough and Nankai Trough were determined, and the total repair cost in relation to the total construction cost was evaluated. The occurrence of damage state 1 had a relatively large effect on the evaluated total repair cost under the evaluation conditions used in this study. A nonlinear relationship was observed between the input magnification and the total repair cost. The friction dampers reduced the damage and total repair cost. [ABSTRACT FROM AUTHOR]

The author has developed a new method for evaluating the seismic performance of existing structures from measured accelerations based on the capacity spectrum method. This involves comparing the performance curve, which is the equivalent nonlinear behavior of a simplified single-degree-of-freedom system, and the demand curve, which is the relationship between the response acceleration and displacement spectra. Two telecommunication towers in Japan were instrumented in 2016, and their responses during several earthquakes have been recorded. This paper discusses the evaluation of damage during the two earthquakes. Moreover, parameters such as the predominant period and the required performance are discussed. The proposed system evaluated both towers as being “elastic.” The damping ratios of the towers are very low, which caused the oscillations to continue for more than 5 min after the mainshock of each earthquake because of long-period components of the seismic motion

Structures may predominantly inelastically deform in a single direction during earthquakes and incur greater damage. This behavior is known as seismic ratcheting and can be caused by eccentric gravity loads. Code clauses were introduced in Canada and New Zealand to amplify displacements obtained from static analysis methods to consider seismic ratcheting effects. However, such clauses are based on analyses of reinforced concrete (RC) wall or single‐degree‐of‐freedom (SDOF) structures, and methods to mitigate seismic ratcheting behavior were not explicitly provided. In this study, parametric analyses of steel and RC moment resisting frame buildings were performed to evaluate the adequacy of code clauses, identify parameters which influence seismic ratcheting behavior, and propose methods to mitigate such behavior. It was found that the New Zealand code underestimated the displacement increase for RC buildings, though it was able to envelope the displacement increase for steel buildings while the Canadian code was conservative. Additionally, the displacement increase was found to be sensitive to the building's post‐yield behavior and ground motion properties. However, assumptions of these properties during design may not be reflective of the actual building and seismic conditions, indicating that a reliable estimate of the increase in displacement is difficult to obtain. Instead, employing mitigation measures to reduce seismic ratcheting effects, such as designing to higher seismic demands, adding a secondary structural system to increase the building's post‐elastic stiffness, or providing more balanced lateral strengths after adjusting for eccentric gravity load effects are better measures to counter seismic ratcheting effects caused by eccentric gravity loads. [ABSTRACT FROM AUTHOR]

The displacements estimated using seismic accelerations are useful for post-earthquake inspection of structural damage. In previous studies, displacements were usually obtained through non-trivial measurement or double integration of the measured acceleration response and then an additional correction process. However, from the signal processing perspective, double integration induces substantial numerical errors. In this study, a displacement estimation approach is developed based on the extended Kalman filter (EKF) with an embedded Bayesian noise-parameters updating technique. The displacement is estimated by EKF with updated time-varying noise parameters based on a Bouc–Wen model. Numerical simulations and a shaking‐table test are presented to demonstrate the proposed method. [ABSTRACT FROM AUTHOR]

Ceilings, windows, and wall tiles were installed in a 3-story reinforced concrete structure subjected to shake-table tests. Alternative detailing for each type was used to evaluate their impact on seismic performance. The ceiling built using conventional detailing had no catastrophic damage but incurred crushing of plasterboards, creating a gap between the ceiling and the surrounding beams. For sliding windows, damage which could cause injuries was not observed, whereas glass cracking was observed for fixed windows. For tiles, the use of organic adhesive prevented tiles from falling, compared to the use of mortar where tile spalling was observed. [ABSTRACT FROM AUTHOR]

Shake-table tests of a 3-story reinforced concrete building with cladding casted to be monolithic with frame elements, with seismic slits or cut reinforcing bars present in some cladding elements to ensure a desirable deformation mechanism, was performed at E-Defense to evaluate its post-disaster functionality. The building satisfied response objectives; behaving elastically with 0.33% drift or less during a "severe earthquake motion" defined in the Japanese Building Standard Law, and has a base shear capacity coefficient greater than 0.55. However, the damage was greater than expected due to deformations concentrating on a few cracks, resulting in continuous functionality not necessarily being achieved. [ABSTRACT FROM AUTHOR]

A framework to extract a building's hysteretic response based on decomposing floor acceleration recordings into different ranks (i.e., decomposition levels) using the discrete wavelet transform (DWT) and then reconstructing signals considering only ranks which corresponded to the building's predominant response mode was recently proposed. However, current rank selection approaches require subjective judgment. This study looks to develop an unbiased rank selection method to enable automation of the hysteresis extraction framework for easier adoption in practice. The selection methodology was developed using response history analysis of several multistory reinforced concrete (RC) frame buildings and validated using data from large‐scale shake‐table tests performed at the E‐Defense testing facility. It was observed that the proposed approach was able to accurately capture the response of RC frame buildings well in majority of cases. The exception to this was for significantly damaged buildings as the use of double integration of accelerations to estimate displacements and the DWT method meant that residual deformations were not well captured. However, significant strength degradation was still observed in the extracted hysteresis behavior for these cases, and thus these buildings would have been correctly classified as being heavily damaged. The step‐by‐step process to automatically select ranks is presented in the paper, and possible revenues for further improvement of the hysteretic response extraction framework are discussed. [ABSTRACT FROM AUTHOR]