The connection joints in support and hanger systems for nonstructural components are prone to serious damage under vertical loads (including heavy pipeline gravity and vertical seismic actions), which poses an adverse impact on life safety and results in substantial property loss. Occlusive bolt connection, as one of the most frequently used connection types in load-bearing support and hanger systems, plays a critical role in determining the overall strength and stability of these systems. The cyclic and monotonic tests were conducted on occlusive bolt connections using cold-formed thin-walled channels to investigate the influence of different cross-sectional types and thicknesses. Different failure modes were observed under vertical loads, and the variation patterns of strength, stiffness degradation, strength degradation, and cyclic energy dissipation capacity of the connections were analyzed. Moreover, a refined finite element model and the formula for calculating the tensile yield load of the occlusive connection were established and verified, showing that the main failure types of occlusive bolt connection are tearing failure and shear failure at rolled edges. The tensile strength of the connection increases in two stages: the first stage is represented by the bending of the rolled edge corner, and the second stage is the tension of the upper flange. The yield strength can be effectively enhanced by increasing the thickness of cold-formed thin-walled channels and the edge distance of the channel nut, but it eventually stabilizes beyond a certain value. Furthermore, increasing the strength of channels shall further increase the yield strength and peak strength of the occlusive bolt connection.

Seismic reliability assessments of water and power supply networks are typically conducted under the assumption of system independence. This article introduces a novel framework for evaluating the seismic reliability of interdependent water and power supply networks, grounded in a comprehensive analysis of their interdependence mechanisms. The proposed framework integrates network flow theory and the Monte Carlo simulation method, leveraging network flow theory to determine the functional status of various system nodes and employing Monte Carlo simulations to account for random factors such as earthquake intensity. The practicality of the framework is validated through a case study in Shangcheng District. The numerical results reveal that: (1) the proposed method effectively evaluates the seismic reliability of interdependent water and power supply networks, and (2) the interdependent mechanisms and network topology significantly impact the seismic reliability of these networks.

As arteries of transportation infrastructure, highway bridge networks (HBNs) are essential for normal residential and commercial activities yet are susceptible to natural or man-made disasters. Their redundancy during emergencies is crucial for effective disaster mitigation and management. To address that, this study explores the ability of HBNs to independently withstand and recover from emergency events. A system-level emergency response simulation method is proposed, integrating seismic hazard analysis, network configurations, traffic data, physical damage to regional bridges, and other factors while accounting for various sources of uncertainty. The potential increase in traffic demand and decrease in bridge capacity in emergency scenarios is also analyzed. Further, a set of comprehensive multi-criteria indicators is introduced to evaluate the redundancy of HBNs. The proposed methodologies are expected to provide a preliminary but effective improvement of resilience assessment for HBNs, facilitating the inspection and recovery processes.

The Palghar district of Maharashtra has recently received attention because of frequent occurrences of earthquakes in its vicinity in the last few years since November 2018. The district falls under seismic zone III, as per the seismic zonation map of India. As the recent earthquake activities have been preceded by many major seismic events in the region, it necessitates to re-evaluate the level of seismic hazard of the area in a reliable and realistic way. With this aim in mind, the probabilistic seismic hazard map of Palghar district with regard to Peak Ground Acceleration (PGA) and 5% damped pseudo-spectral acceleration (PSA) at 0.2 and 1.0 s for 10% and 2% probability of exceedance (PoE) in 50 years at engineering bedrock level is presented. The estimation of hazard is performed in a finer grid resolution of 0.02° × 0.02° and takes into consideration the nonuniform distribution of earthquake probability within a seismic source zone (SSZ) and data-driven selection of suitable ground motion prediction equations (GMPEs) with appropriate weight factors. The spatial variation of the hazard level as reflected in the hazard maps, demonstrates notable improvements over the earlier studies. The PGA at the atomic power plant in the district is found to be 0.15g for DBE condition. The results can be used for designing earthquake-resistant structures in addition to assessing seismic safety of the existing structures.

Fiber-reinforced polymer (FRP) has been widely used to retrofit existing structures to improve their seismic performance. A reinforced concrete frame structure is designed as a case study structure to study the impact of FRP retrofitting on the seismic risk of corroded structures. Finite element models are established using the OpenSEES finite element platform for intact structures, corroded structures, and FRP-retrofitted corroded structures by considering two corrosion damage degrees and four FRP retrofitting schemes. Based on the results of seismic fragility and risk analysis, combined with the economic loss models, the retrofitting schemes are evaluated using the benefit-cost ratio (BCR) as the indicator. Three factors, including the economic development level of the building site, remaining service life, and changes in discount rates, are considered in the economic loss assessment. The impact of these factors on the benefits of structural retrofitting is analyzed through three cases. The results indicate that greater economic benefits are generated by retrofitting structures in economically developed regions with higher corrosion damage degree. Meanwhile, it is found that ignoring the remaining service life of the structure may lead to an overestimation of the retrofitting benefits. Finally, considering different discount rates, it is found that higher discount rates lead to lower BCR values. The conclusions of this study will benefit engineers in formulating reasonable FRP seismic retrofitting schemes for existing structures.

During the 2022 M6.9 Menyuan earthquake, a high-speed railway bridge that is 5 km away from the fault experienced complex movements of girders but no girder falling, which is a contrast with the “Domino” falling of girders of a highway bridge that is 7 km away from the fault during the 2021 M7.4 Maduo earthquake. Inspired by the comparison, this paper investigates the constraint effects of the rail on the movement of the bridge which is usually ignored in seismic response of the bridge. The finite element model of an 8-span simply-supported girder bridge with CRTS I double-block ballastless tracks laying on top is established. Five groups of three-component earthquake records were selected as seismic input to test the constraint effects of the rail under different seismic loads. The results show that, with the constraint of the rail, the amplitude and duration of the acceleration response at the middle span in the longitudinal direction increases, whereas the longitudinal displacement difference between the beam joint and the pier top decreases, reducing the risk of girder falling. In the transverse direction, the rail constraint leads to the reduction of the displacements of the side spans. In the vertical direction, the constraint effect of the rail does not significantly change the peak acceleration and displacement of the bridge.

Real-time hybrid simulation (RTHS) is a promising experimental method to evaluate structural dynamics. It divides the to be simulated structure into a numerical substructure (NS) and a physical substructure (PS), and has been lauded for its versatility and cost-effectiveness. In RTHS, a transfer system is used to guarantee synchronization among substructures, resulting in the fact that the actuator control scheme plays a vital role in attaining high accuracy and stability. This is particularly true for multi-axial RTHS (maRTHS), where several actuators are used to impose precise controls on the PS. In maRTHS, internal coupling issues are more troublesome, and the control-structure interactions and servo-actuator dynamics are more complicated than in single axial RTHS, making actuator control more challenging. With this in mind, we propose a robust compensation strategy, combining H_∞ loop shaping theory and polynomial extrapolation, to tackle servo-hydraulic dynamics issues for maRTHS problems. The proposed method consists of an H_∞ loop shaping feedback controller and polynomial extrapolation. The former can stabilize the servo-hydraulic actuator and PS dynamics and achieve approximate decoupling among the actuators, while the latter will further reduce the time delay as well as amplitude discrepancies. The integration of these control strategies facilitates a flexible design scheme that handles various uncertainties and has high stability. Initially, a comprehensive design procedure of the proposed method is provided. Subsequently, the effectiveness of this method is demonstrated through a series of virtual RTHSs, using a recently established maRTHS benchmark model. The simulated results indicate that the proposed approach holds considerable promise for high-precision experiment synchronization, and robustness in the face of uncertainties, including numerical structure variability, seismic excitations, and multiple-actuator properties.

Medium-rise soft story special moment resisting frame (SMRF) buildings can be found in many active seismic regions worldwide. This paper assesses seismic vulnerability of medium rise soft story SMRF building from a highly active seismic region under near field, fling step, far field, and mixed strong motion excitations. Fragility functions are derived for peak ground acceleration (PGA), peak ground velocity (PGV), and spectral acceleration (S_a) as intensity measures (IM) to identify possible anomalies in the selection of IMs while performing seismic vulnerability analyses. The results highlight that the fragility functions derived using mixed strong motion yield conservative estimate of exceedance probability for higher damage states in the near field regions. Moreover, at the considered maximum PGA (0.4  g) for many cities in Nepal, a seismically very active region in the world, most of the medium-rise soft story SMRF buildings would be unoccupiable due to the occurrence of extensive or collapse damage states under near field or fling step excitations.