The increasing need to reduce damage and downtime in modern buildings has led to the development of a low-damage design philosophy, where the earthquake loads can be resisted with damage confined to easily replaceable components. Post-tensioned (PT) concrete walls have emerged as a popular lowdamage structural system that have been implemented in a range of buildings. In order to provide essential evidence to support the development of lowdamage concrete structures, a system-level shake-table test was conducted on a two-storey low-damage concrete wall building implementing state-of-art design concepts. The test building included PT rocking walls that provide the primary lateral-load resistance in both directions, a frame that utilized slotted beam connections, and a range of alternative energy dissipation devices that were installed at wall base or/and beam-column joints. The building was subjected to 39 tests with a range of intensity ground motions, incorporating both unidirectional and bidirectional ground motions on the structure with different combinations of wall strength and energy dissipating devices. The building performed exceptionally well during the intense series of tests, confirming the suitability of both the design methods and the connection detailing implemented. The building achieved an immediate occupancy performance objective even when subjected to maximum considered earthquake hazard shaking. The building exhibited only minor damage at the conclusion of testing, with distributed cracking in the floors and cosmetic spalling in the wall toes that did not compromise structural capacity or integrity and could be easily repaired with minimal disruption.The test has provided a rich dataset that is available for further analysis of the building response and validation of design methods and numerical models.

The seismic isolation code which must be used for all seismic isolated buildings in the United States is conservative in many of its provisions. While seismic isolation is flourishing in other countries, it is underused in the United States. For static analysis and for the selection of time histories, the spectrum is constant-velocity for periods of one second and longer, leading to large displacements for long period systems and forcing the designer to use added damping to reduce these displacements. The damping systems used are hysteretic with the characteristic that damping decreases with increasing displacement. To achieve the damping needed to reduce these large displacements, expected from very rare seismic input, means that at smaller displacements, caused by realistic levels of seismic input, the damping will be very much higher, and there may be stiffening of the isolation system, meaning that the building may not act as isolated and there may be an impact on sensitive internal equipment. This paper shows how highly damped isolation systems are counterproductive to isolation and suggests an alternative approach that will conform to code requirements but ensure that, at moderate earthquake inputs, the equipment remains protected, and the large code-mandated displacements are kept to acceptable levels.

Reinforced concrete (RC) buildings are commonly used around the world. With recent earthquakes worldwide, rapid structural damage inspection and repair cost evaluation are crucial for building owners and policy makers to make informed risk management decisions. To improve the efficiency of such inspection, advanced computer vision techniques based on convolutional neural networks have been adopted in recent research to rapidly quantify the damage state (DS) of structures. In this article, an advanced object detection neural network, named YOLOv2, is implemented, which achieves 98.2% and 84.5% average precision in training and testing, respectively. The proposed YOLOv2 is used in combination with the classification neural network, which improves the identification accuracy for critical DS of RC structures by 7.5%. The improved classification procedures allow engineers to rapidly and more accurately quantify the DSs of the structure, and also localize the critical damage features. The identified DS can then be integrated with the state‐of‐the‐art performance evaluation framework to quantify the financial losses of critical RC buildings. The results can be used by the building owners and decision makers to make informed risk management decisions immediately after the strong earthquake shaking. Hence, resources can be allocated rapidly to improve the resiliency of the community.

The benefits of tracking, identifying, measuring features of interest from structure responses have endless applications for saving cost, time and improving safety. To date, structural health monitoring (SHM) has been extensively applied in several fields, such as aerospace, automotive, and mechanical engineering. However, the focus of this paper is to provide a comprehensive upto-date review of civil engineering structures such as buildings, bridges, and other infrastructures. For this reason, this article commences with a concise introduction to the fundamental definitions of SHM. The next section presents the general concepts and factors that determine the best strategy to be employed for SHM. Afterward, a thorough review of the most prevalent anomaly detection approaches, from classic techniques to advanced methods, is presented. Subsequently, some popular benchmarks, including laboratory specimens and real structures for validating the proposed methodologies, are demonstrated and discussed. Finally, the advantages and disadvantages of each method are summarized, which can be helpful in future studies.

Structural bolts are critical components used in different structural elements, such as beam-column connections and friction damping devices. The clamping force in structural bolts is highly influenced by the bolt rotation. Much of the existing vision-based research about bolt rotation estimation relies on traditional computer vision algorithms such as Hough transform to assess static images of bolts. This requires careful image preprocessing, and it may not perform well in the situation of complicated bolt assemblies, or in the presence of surrounding objects and background noise, thus hindering their real-world applications. In this study, an integrated real-time detect-track method, namely, RTDT-bolt, is proposed to monitor the bolt rotation angle. First, a real-time convolutionalneural-networks-based object detector, named YOLOv3-tiny, is established and trained to localize structural bolts. Then, the target-free object tracking algorithm based on optical flow is implemented to continuously monitor and quantify the rotation of structural bolts. In order to enhance the tracking performance against background noise and potential illumination changes during tracking, the YOLOv3-tiny is integrated with the optical flow tracking algorithm to redetect the bolts when the tracking gets lost. Extensive parameter studies were conducted to identify optimal tracking performance and examine the potential limitations. The results indicate that the RTDT-bolt method can greatly enhance the tracking performance of bolt rotation, which can achieve over 90% accuracy using the recommended range for the parameters.

SUMMARY Concrete core‐wall structural systems are prevalent for high‐rise residential buildings in the West Coast of the United States. To assess the seismic performance characteristics of this system, a 42‐story core‐wall residential building was designed for a site in Los Angeles, CA. The building was designed using two different design approaches. The first design followed prescriptive requirements of US building codes, except height limits were disregarded. The second design followed a performance‐based procedure. Analytical models of each design were subjected to a series of earthquake ground motions representative of very frequent to very rare shaking intensities. Effectiveness of the various design methods is assessed considering structural performance indices, initial costs, and repair costs associated with anticipated earthquake ground shaking. The results illustrate the seismic performance potential of this structural system and demonstrate the application of a practical seismic performance assessment approach for buildings. Copyright © 2012 John Wiley & Sons, Ltd.

No abstract

No abstract