Post-Earthquake Rapid Damage Assessment of Road Bridges in Glina County

In December 2020, a strong earthquake occurred in Northwestern Croatia with a magnitude of ML = 6.3. The epicenter of this earthquake was located in the town of Petrinja, about 50 km from Zagreb, and caused severe structural damage throughout Sisak-Moslavina county. One of the biggest problems after this earthquake was the structural condition of the bridges, especially since most of them had to be used immediately for demolition, rescue, and the transport of mobile housing units in the affected areas. Teams of civil engineers were quickly formed to assess the damage and structural viability of these bridges and take necessary actions to make them operational again. This paper presents the results of the rapid post-earthquake assessment for a total of eight bridges, all located in or around the city of Glina. For the assessment, a visual inspection was performed according to a previously established methodology. Although most of the inspected bridges were found to be deteriorated due to old age and lack of maintenance, very few of them showed serious damage from the earthquake, with only one bridge requiring immediate strengthening measures and use restrictions. These measurements are also presented in this paper.

Rigid impacts of three-dimensional rocking structures

Studies of rocking motion aim to explain the remarkable earthquake resistance of rocking structures. State-of-the-art assessment methods are mostly based on planar models, despite ongoing efforts to understand the significance of three-dimensionality. Impacts are essential components of rocking motion. We present experimental measurements of free-rocking blocks on a rigid surface, focusing on extreme sensitivity of impacts to geometric imperfections, unpredictability, and the emergence of three-dimensional motion via spontaneous symmetry breaking. These results inspire the development of new impact models of three-dimensional facet and edge impacts of polyhedral objects. Our model is a natural generalization of existing planar models based on the seminal work of George W. Housner. Model parameters are estimated empirically for rectangular blocks. Finally, new perspectives in earthquake assessment of rocking structures are discussed.

Study of Building Safety Monitoring by Using Cost-Effective MEMS Accelerometers for Rapid After-Earthquake Assessment with Missing Data

Suffering from structural deterioration and natural disasters, the resilience of civil structures in the face of extreme loadings inevitably drops, which may lead to catastrophic structural failure and presents great threats to public safety. Earthquake-induced extreme loading is one of the major reasons behind the structural failure of buildings. However, many buildings in earthquake-prone areas of China lack safety monitoring, and prevalent structural health monitoring systems are generally very expensive and complicated for extensive applications. To facilitate cost-effective building-safety monitoring, this study investigates a method using cost-effective MEMS accelerometers for buildings’ rapid after-earthquake assessment. First, a parameter analysis of a cost-effective MEMS sensor is conducted to confirm its suitability for building-safety monitoring. Second, different from the existing investigations that tend to use a simplified building model or small-scaled frame structure excited by strong motions in laboratories, this study selects an in-service public building located in a typical earthquake-prone area after an analysis of earthquake risk in China. The building is instrumented with the selected cost-effective MEMS accelerometers, characterized by a low noise level and the capability to capture low-frequency small-amplitude dynamic responses. Furthermore, a rapid after-earthquake assessment scheme is proposed, which systematically includes fast missing data reconstruction, displacement response estimation based on an acceleration response integral, and safety assessment based on the maximum displacement and maximum inter-story drift ratio. Finally, the proposed method is successfully applied to a building-safety assessment by using earthquake-induced building responses suffering from missing data. This study is conducive to the extensive engineering application of MEMS-based cost-effective building monitoring and rapid after-earthquake assessment.

Post-earthquake fast damage assessment using residual displacement and seismic energy: Application to Mexico City

The simplicity, timeliness, and reliability of a post-earthquake assessment are fundamental for decision-makers in emergency management. An adequate risk assessment will help during the recovery and, therefore, increases the resilience of the community. Although within this context, the walk-down damage survey with the correct filling of evaluation forms and use of processing-data tools make possible a pertinent post-earthquake assessment, it is desirable to have measurable parameters that can complement the visual field evaluation with quantitative information. In some cases, basic quantitative measures, such as crack width, are not enough to make pertinent structural damage assessments. This article presents a fast and simple methodology to estimate the median maximum displacement and plastic energy demands on simple single-degree-of-freedom systems from the residual displacement they exhibit after being subjected to ground motions generated in the lakebed zone of Mexico City. Based on this, a discussion is offered on how a post-earthquake assessment can be improved by complementing the visual and measured information gathered on an existing structural system after an intense ground motion, with estimates of its maximum and cumulative plastic deformation demands derived from its residual deformation.

Rigid Impacts of Three-dimensional Rocking Structures

Studies of rocking motion aim to explain the remarkable earthquake resistence of rocking structures . State - of - the -art assessment methods are mostly based on planar models , despite ongoing efforts to understand the significance of three - dimensionality . Impacts are essential components of rocking motion . We present experimental measurements of free -rocking blocks , focusing on extreme sensitivity of impacts to geometric imperfections , unpredictability , and the emergence of three - dimensional motion via spontaneous symmetry breaking . These results inspire the development of new impact models of three dimensional facet and edge impacts of polyhedral objects . Our model is a natural generalization of existing planar models based on the seminal work of George W. Housner . Model parameters are estimated empirically for rectangular blocks . Finally , new perspectives in earthquake assessment of rocking structures are discussed .

Post-earthquake assessment of moderately damaged reinforced concrete plastic hinges

Modern reinforced concrete buildings are often designed to dissipate energy during strong earthquakes by permitting the controlled formation of plastic hinges. Plastic hinges require assessment of residual capacity in post-earthquake situations. However, few past studies have investigated this topic, and results from experiments focused on undamaged structures are not always transferable to post-earthquake situations. Data from an experimental program, in which both cyclic and earthquake-type loadings were applied to nominally identical reinforced concrete beams, are used to investigate the relationship between residual crack widths and rotation demands. Assessment of the peak deformation demands incurred during a damaging earthquake is critical for post-earthquake assessments, but residual crack widths are shown to be dependent on several factors in addition to the peak rotation demand. Non-dimensional metrics capturing the distribution of cracking are proposed as a more informative alternative. The reduction in stiffness that occurs as a result of earthquake-induced plastic hinging damage was also investigated. A proposed model is shown to give a lower-bound estimate of the residual stiffness following arbitrary earthquake-type loadings.