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Steel corrosion is by far the biggest durability issue for many reinforced concrete bridge structures worldwide. The columns in these bridges can be critical, especially for seismic resistance. In this study, glass-fibre-reinforced-polymer bars were investigated as an alternative to steel for sustainable and resilient bridge construction. As lateral reinforcement is more susceptible to corrosion, and structures fully reinforced with fibreglass bars display softer responses with lower shear and flexural capacity, fibreglass spirals and longitudinal steel reinforcement were used in the tested columns. The experimental programme included the design, construction and seismic testing of full-scale (508 mm diameter) and half-scale (356 mm diameter) columns. The other variables investigated were the axial load and the amount and spacing of spirals. For both column sizes, fibreglass spirals provided increasing confining pressure to the concrete core with increased deformations. For the full-scale columns, no adverse size effects were observed in comparison to the half-scale columns. The columns produced large ductility and energy dissipation. Results from selected representative specimens are presented here to establish the feasibility of using fibreglass spirals in circular bridge columns. Resilience can thus be built into new columns through innovative durable fibreglass lateral reinforcement, with similar if not superior behaviour to steel-reinforced columns. [ABSTRACT FROM AUTHOR]

Traditional ancient Tibetan buildings (TATBs) date back hundreds of years. The seismic performance of TATBs constructed with stones and mud was analyzed by utilizing structural subscale features (materials, walls, and structures). The key to load-bearing in TATBs is the three-leaf stone wall. Based on the mechanical properties of materials, compression tests and quasistatic static tests of walls, this paper confirms that the seismic resistance capacity of the three-leaf stone wall of TATBs is unable to meet Chinese standards. The aims of this study are to present the dynamic behavior of TATBs by shaking table tests. According to the experimental data, the transcendence intensity magnification calculation method is modified to calculate the seismic vulnerability of TATBs. The results show that when the peak acceleration of ground motion is 1.042 m/s2, 1.598 m/s2 and 2.881 m/s2, TATBs undergo slight damage, moderate damage, and severe damage, respectively. [ABSTRACT FROM AUTHOR]

This paper investigates a steel moment resisting frame (MRF) with a novel type of self‐centering (SC) base isolators, wherein superelastic shape memory alloy (SMA) U‐shaped dampers (SMAUDs) work as core components. A two‐story steel MRF model equipped with two SMAUD‐based isolators was designed and built in the laboratory, and a series of shake table tests were conducted to examine the dynamic behavior and seismic performance of the frame. Throughout all the tests, no interventions, such as repair or replacement of frame or isolator members, were done. Shake table test results demonstrated that the SMAUD‐based isolators could withstand multiple strong earthquakes with stable SC behavior. The utilization of SMAUD‐based isolators provided effective protection for the frame, enabling it to restore its original position with minimal structural damage. A numerical model of the tested steel MRF with SMAUD‐based isolators was also built. The results obtained from the numerical analyses agreed with those of the shake table tests satisfactorily. A comparative study of the seismic performance between the MRF with SMAUD‐based isolators and the MRF with traditional steel U‐shaped damper‐based isolators was also conducted in the shake table tests. The results showed that SMAUD‐based isolators not only inherit the isolation function of conventional isolators to protect the frame but also possess an SC ability to eliminate residual isolator deformation effectively. Moreover, SMAUD‐based isolators demonstrate remarkable resilience to withstand multiple strong seismic events without any need for repair or replacement. [ABSTRACT FROM AUTHOR]

The present study proposes a new technique for retrofitting corroded beam–column joints (BCJs) using high‐strength fiber reinforced concrete (HSFRC) and stirrups replacement. The entire corrosion‐affected concrete was removed and replaced with HSFRC. The corroded reinforcing bars were cleaned and treated to resist the progression of the corrosion mechanism. The severely pitted stirrups were replaced with new stirrups. Four exterior BCJ specimens were tested under seismic loading to determine the effectiveness of the proposed retrofitting scheme. The efficacy of the proposed retrofitting scheme is determined in terms of the hysteresis response, stiffness degradation, cumulative energy dissipation, ductility, and damage index. A significant delay in the fracture of severely pitted reinforcing bars was experienced for the corrosion‐damaged retrofitted specimens compared to the corroded unretrofitted specimen. The cumulative energy dissipation of the corroded unretrofitted and corroded retrofitted specimens was 0.4 and 1.3 times that of the reference specimen, respectively, indicating the effectiveness of the retrofitting strategy, as both specimens had similar corrosion rates. The test results indicated that the proposed retrofitting technique effectively improved the seismic performance of the corrosion‐damaged BCJs. [ABSTRACT FROM AUTHOR]

The shear wall system with cast‐in situ concrete infilled walls has been widely used in high‐rise buildings due to its significant advantages in construction. In this paper, quasi‐static tests were conducted on the shear walls with and without cast‐in situ concrete infilled walls to analyze their failure modes, load‐bearing capacity, stiffness, energy dissipation capacity, and ductility. A simplified model of the shear wall with cast‐in situ concrete infilled walls was proposed based on the fiber element model in OpenSees. The test results showed that the shear wall specimens with cast‐in situ concrete infilled walls exhibited full‐section compression or tension failure, and the cast‐in situ concrete infilled walls did not show obvious damage. Compared with the shear wall without infilled walls, the overall stiffness, load bearing capacity, and energy dissipation capacity of the shear wall specimens with cast‐in situ concrete infilled walls improved, indicating better seismic performance than those without infilled walls. Comparison between the hysteresis and skeleton curves derived from the tests and those simulated by the proposed simplified model revealed errors within 15% for stiffness, yield bearing capacity, and ultimate bearing capacity for shear walls with cast‐in situ concrete infill walls, affirming the effectiveness and accuracy of the model. [ABSTRACT FROM AUTHOR]

Records of pile lengths are not available for several hundred high-mast light towers (HMLTs) throughout the state of Minnesota. The foundation systems, typically steel H-piles or concrete-filled steel pipe piles connected to a triangular concrete pile cap, risk overturning in the event of peak wind loadings if the foundation piles are not sufficiently deep to provide the designed uplift capacity. Without prior knowledge of the in situ pile lengths, an expensive tower foundation retrofit or replacement effort would need to be undertaken. However, the development of a nondestructive screening tool to determine the in situ pile length—compared with replacing or retrofitting all towers with unknown foundation geometries—would potentially provide significant cost savings. The main goal of the research is the development of nondestructive evaluation testing techniques for determining in situ pile lengths using steady-state vibration and hammer-impact seismic testing. The foundation testing protocol involves (1) a preliminary site investigation to determine the shallow subsurface geometry and orientation of the foundation pile cap, (2) the use of seismic cone penetrometer (SCP) attached to a cone penetration test rig to capture the induced steady-state and impact waveforms, and (3) data-driven analysis of field testing results to determine the pile lengths. [ABSTRACT FROM AUTHOR]

Interaction between masonry infill walls (MIWs) and a main structural system can impact the overall structural performance. However, there is no test to investigate the impact of MIWs on self-centering prestressed concrete (SCPC) frames, nor has there been a probabilistic performance evaluation considering the coupling effects of peak interstory drift ratio (PIDR) and residual interstory drift ratio (RIDR). This study compares the seismic performance of SCPC frames with and without MIWs through quasi-static tests and seismic risk assessment under mainshock–aftershock (MSAS) sequences. To begin, quasi-static tests on one-story SCPC frames with and without MIWs are performed to assess their seismic performance. A numerical simulation method for the SCPC frame with MIWs is then proposed and validated. Following that, the seismic performance of four multistory SCPC frames with and without MIWs is investigated under MSAS sequences at the maximum considered earthquake level. Finally, the seismic vulnerability assessment, considering the coupling effect of PIDR and RIDR under MSAS sequences, is conducted. The results indicate that cracks on the MIW present diagonal stepped cracks, and the MIW does not cause damage to the SCPC frame. When the MIW is damaged, the RIDR of the SCPC-MIW frame increases significantly; when the crack development is stable, the RIDR increases slowly as the interstory drift increases but remains at a very low level. Besides, when the MIW is damaged, an obvious deformation concentration effect occurs on the SCPC-MIW frame. The SCPC-MIW frame has a lower probability of exceeding the immediate occupancy level P(IO) than the SCPC frame, but it has a higher probability of exceeding the repairable level P(RE) when the seismic intensity is relatively small. Overall, the P(IO) and P(RE) of the SCPC and SCPC-MIW frames are higher under MSAS sequences than under MS-only sequences, except for the SCPC25 frame. [ABSTRACT FROM AUTHOR]

In this study, nonlinear isoparametric shell elements with variable edge order and moving nodes from CBAL4M to CBAL12M were developed and integrated into FINITE. Specific mapping and surfaces for two‐dimensional isoparametric shell elements, shape functions, and their derivatives are presented. The advantage of the developed shell element is that it can represent not only the smeared reinforcement on the wall and slab but also the discrete special reinforcement that is important for crack propagation in the nonlinear simulation of RC structures. With the advantage of movable nodes, the discrete reinforcement can be effectively covered and the position of the discrete reinforcement can be determined. When modelling reinforced concrete structures dominated by shear walls, the use of variable edge orders at the slab‐wall interfaces where high stresses or forces are expected reduces the calculation time and capacity by using an optimal number of nodes for hybrid modelling. Nonlinearity is considered only in the form of material nonlinearity with a stress‐strain curve, tension stiffening, and cracking including crack rotation. The analytical model is validated by comparing the results at the element level of the Vecchio and Collins test panels at the University of Toronto and at the structural level of the five‐story shear wall building with staggered openings at the University of Michigan. Nonlinear hybrid simulations of 2D and 3D models of 2‐story and 5‐story shear wall‐dominated RC buildings are investigated with the developed element considering ultimate load curves, deflection shapes, crack patterns, stress distributions, and 3D effects and force mechanisms. For this purpose, a three‐story scaled test model was constructed and tested to simulate the seismic behavior. The test results are also compared with the analytical results of SAP2000 and the developed nonlinear shell element. The seismic capacity of the test model and the analytical models was similar at 31 tons. The developed element can be effectively used for modelling and nonlinear hybrid simulation of RC buildings and can also be applied to prestressed concrete structures for tendon modelling. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the ability of propolis‐coated ureteric stents to solve complications, especially urinary tract infections (UTIs) and crusting, in patients with long‐term indwelling ureteric stents through antimicrobial and anti‐calculus activities. Materials and Methods: Polyurethane (PU) ureteric stents were immersed in the ethanol extract of propolis (EEP), a well‐known antimicrobial honeybee product, and subjected to chemical, hydrophilic, and seismic tests. The antimicrobial activity of the EEP coating was then examined by in vitro investigation. Proteus mirabilis infection was induced in rats within uncoated and EEP‐coated groups, and the infection, stone formation, and inflammation were monitored at various time points. Results: The characterisation results showed that the hydrophilicity and stability of the EEP surface improved. In vitro tests revealed that the EEP coating was biocompatible, could eliminate >90% of bacteria biofilms attached to the stent and could maintain bacteriostatic properties for up to 3 months. The in vivo experiment revealed that the EEP‐coating significantly reduced the amount of bacteria, stones, and salt deposits on the surface of the ureteric stents and decreased inflammation in the host tissue. Conclusions: Compared with clinically used PU stents, EEP‐coated ureteric stents could better mitigate infections and prevent encrustation. Thus, this study demonstrated that propolis is a promising natural dressing material for ureteric stents. [ABSTRACT FROM AUTHOR]

To quantify the seismic effectiveness of the most commonly used fishing line tie up method for securing museum collections and optimize fixed strategies for exhibitions, shaking table tests of the seismic systems used for typical museum collection replicas have been carried out. The influence of body shape and fixed measure parameters on the seismic responses of replicas and the interaction behavior between replicas and fixed measures have been explored. Based on the results, seismic effectiveness evaluation indexes of the tie up method are proposed. Reasonable suggestions for fixed strategies are given, which provide a basis for the exhibition of delicate museum collections considering the principle of minimizing seismic responses and intervention. The analysis results show that a larger ratio of height of mass center to bottom diameter led to more intense rocking responses. Increasing the initial pretension of fishing lines was conducive to reducing the seismic responses and stress variation of the lines. Through comprehensive consideration of the interaction forces and effective securement, it is recommended to apply 20% of breaking stress as the initial pretension. For specific museum collections that cannot be effectively protected by the independent tie up method, an optimized strategy of a combination of fishing lines and fasteners is recommended. [ABSTRACT FROM AUTHOR]

Replaceable flexural and shear fuse-type coupling beams are used in hybrid coupled shear wall (HCSW) systems, enabling concrete buildings to be promptly recovered after severe earthquakes. This study aimed to analytically evaluate the seismic behavior of flexural and shear fuse beams situated in short-, medium- and high-rise RC buildings that have HCSWs. Three building groups hypothetically located in a high seismic hazard zone were studied. A series of 2D nonlinear time history analyses was accomplished in OpenSees, using the ground motion records scaled at the design basis earthquake level. It was found that the effectiveness of fuses in HCSWs depends on various factors such as size and scale of the building, allowable rotation value, inter-story drift ratio, residual drift quantity, energy dissipation value of the fuses, etc. The results show that shear fuses better meet the requirements of rotations and drifts. In contrast, flexural fuses dissipate more energy, but their sectional stiffness should increase to meet other requirements. It was concluded that adoption of proper fuses depends on the overall scale of the building and on how associated factors are considered. [ABSTRACT FROM AUTHOR]

The bidirectional ductile end diaphragm concept uses energy-dissipating buckling restrained braces (BRB) as fuses located at the end of a bridge superstructure's floating spans. This system using BRBs can provide seismic resilient and damage-free bridges fully operational immediately after an earthquake. A shake-table testing program was conducted to subject a 1/2.5-scale specimen to series of ground motions. The specimen tested represents one span of a five-span bridge having BRBs connected to the abutment and the pier next to it. The purpose of these tests was to experimentally validate proposed connection details when subjected to the three-dimensional (3D) displacement histories (compared with the axis of the BRBs) that resulted from bidirectional ground motions and the fact that the connections must accommodate inclined BRB layouts. The test protocol included earthquake displacement histories that represent design demands, cycles of thermal excitations, and (to eventually make the BRBs fail) extreme motions. The testing program validated the effectiveness of the proposed concept and the ability of BRBs to sustain multiple ground motions before failure. [ABSTRACT FROM AUTHOR]

A series of model tests about vibroflotation were conducted to investigate soil property change on silica sand foundations, especially for earthquake-resistant behavior. First, the process of double-point vibroflotation was investigated with a simulative vibrator system. Thereafter, shaking table tests were conducted to evaluate seismic responses. The results illustrated that the relative density was significantly enhanced after the first vibratory period, with the highest enhancement appearing at the vibropoint in the plane and the middle layer along the depth. As for the seismic tests, the excess pore pressure ratios show that the vibroflotation can apparently improve the liquefaction-resistance capacity of the silica sand foundation. Moreover, the shear stiffness of the unconsolidated foundation decreases distinctly under 0.2g earthquake motion, while the consolidated foundation remains capable of transmitting acceleration. Inflicting white noise before the any earthquake motion and after 0.2g earthquake, the result shows that the predominant frequency of unconsolidated foundation decreases apparently. The dynamic shear stress–strain curves were compared, while the development law of the time history was also investigated. These results demonstrated that this method can obviously prevent the shear stiffness attenuation. To sum up, the vibroflotation compaction method can make a great densification and increase the earthquake-resistant capacity. [ABSTRACT FROM AUTHOR]

Fine-grained sand deposits in subtropical regions are valued for their low settlement percentages, providing high load-bearing capacity for foundations. Despite existing literature, certain behaviors of these deposits, particularly under cyclic loading in unsaturated conditions with stiffness control, still need to be better understood. Given the potential for shaft friction degradation in cyclically loaded axial piles, this gap is critical. This paper comprehensively investigates the mechanical properties of PE-Sand from a Southern Brazil deposit under cyclic loads, integrating laboratory and field analyses. Characterization involved granulometric, specific gravity, consolidation, matric suction, microscopic, mineralogical, and chemical tests. Uncommon unsaturated direct shear tests were performed, evaluating shear interface degradation under one-way and two-way cyclic loads. Standard penetration and seismic piezocone tests at 25m depth contrasted field properties. Findings identified uniform micaceous quartz sand. A novel conceptual model for PE-sand cohesion emerged from stiff-direct shear tests. Cyclic tests revealed heightened interface degradation with fewer cycles at increased load amplitudes. Fatigue results converged to a cumulative damage value, signifying material criticality limiting sand-sand interface resistance. Field exploration confirmed a heterogeneous sand deposit with geotechnical properties akin to laboratory findings. This study contributes nuanced insights into fine sand behavior under cyclic loading in unsaturated conditions, bridging gaps in existing knowledge. [ABSTRACT FROM AUTHOR]

In this paper, a new foam concrete-extruded polystyrene composite wall panel (FCPW) is proposed. In order to investigate the response of these wall panels to the loading conditions that may occur during an earthquake event, a total of three specimens were designed in this study to study the seismic performance of the wall panels with different sizes of cyclic loads applied to them. By analyzing the seismic parameters such as hysteresis curve, skeleton curve, ductility and stiffness degradation factor of the wall panels, it is concluded that the wall panels have good seismic performance. Both the test phenomenon and damage mechanism indicate that shear damage is the damage form of the specimen. Comparing the specimens, it can be seen that the height-to-width ratio and the strength of the specimen itself have obvious effects on the seismic performance. The larger the height-to-width ratio is, the larger the ductility is and the better the seismic performance is. The smaller the thickness of the concrete is, the smaller the ductility is and the worse the seismic performance is. This study helps to update the iteration of composite wall panels composed of extruded plastic board and concrete and provide a reference for future research. [ABSTRACT FROM AUTHOR]

Given the widespread use of lightweight composite wall panels in building structures, it is crucial to comprehend their seismic performance. This paper proposes a new lightweight concrete composite exterior wallboard (LCEW) featuring truss-type thermal barrier connectors (TBCs). Through the proposed static test, the damage morphology and hysteresis curve of the specimen are obtained; the hysteresis characteristics, skeleton curve, stiffness degradation, etc., are investigated; and the damage modes are summarized. The results demonstrate that the steel frame structure can effectively adapt to the use of LCEW, resulting in an approximately 20% increase in the frame structure's bearing capacity. Second, the wall panels with a uniform transverse arrangement of TBCs could not perform as well, as they could only delay the crack opening. To give full play to its effect, it should be combined with the direction of the main tensile zone of the wall panels. Meanwhile, the sliding gusset connections effectively released the frame action at the system level. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study conducted on the behavior of drop-in anchors in uncracked concrete slabs. Both seismic (cyclic) load tests and static load tests to collapse are performed on drop-in anchors subjected to tension or shear forces. Three different anchor sizes are subjected to seismic qualification testing, followed by a static load test to collapse. The test results confirm the capability of the tested anchors to sustain simulated pulsating seismic tension and shear loading with frequency ranges between 0.1 and 2.0 Hz. It was observed that no tension failure occurred at the end of the cyclic load tests for all the tested anchors, and their residual inelastic maximum displacement at the end of the cyclic tension test was relatively small. Moreover, the experimental results show that the anchors' ultimate capacities are higher than those specified by the anchor manufacturer. Finally, the anchors' experimental pullout shear capacities are compared with the failure prediction equations in the literature and design codes. It is found that the theoretical models provide a conservative prediction of the concrete breakout of anchors in tension compared to the experimental ultimate loads. The coefficient for pry-out strength (kcp) equal to 2 or slightly smaller than 2 is likely to predict a better pry-out capacity with the experimental results compared to the application of the high conservative value of kcp equal to 1, as given in the code. [ABSTRACT FROM AUTHOR]

This study aims to reveal the control mechanism of viscoelastic (VE) energy dissipation braces with strong mechanical nonlinear characteristics on the seismic response of reinforced concrete (RC) frame structures. Firstly, a new STM32-Matlab-OpenSees joint hybrid test platform is developed by introducing OpenSees, which is convenient for structural modeling and fast for structural calculation. The overall architecture and operation of the hybrid test platform are comprehensively analyzed. Then, a series of simulated seismic hybrid tests on three-dimensional (3D) RC frame structures with VE energy dissipation braces under different seismic waves are successfully carried out. Lastly, the hybrid test results of this structure system at different working conditions are compared and analyzed comprehensively. The research results show that the developed platform breaks the boundary limitation that OpenSees relies on the framework software OpenFresco and can only be connected to specific control systems in the hybrid test. Thus, it greatly expands the application scope of flexible configuration controller and actuator categories for the hybrid test platform, and it also provides a good reference value for the establishment and implementation of similar hybrid test platforms. Under the action of various seismic waves, VE energy dissipation braces has good universality for the shock absorption of RC frame structures. The damping control effect and energy dissipation efficiency of VE energy dissipation braces are significantly different under various seismic waves. In the design of RC frame structures with VE energy dispersion braces, it is very necessary to conduct the seismic analysis of the structures under multiple ground motions with wide frequency domain. The additional position of VE energy dissipation braces should be an important analysis indicators in the optimization design of the structures. [ABSTRACT FROM AUTHOR]

Comprehensive assessment of the active/passive seismic stability of shallow tunnel faces is an urgent and complex task. This work establishes a promising three-dimensional (3D) approach using upper-bound limit analysis to evaluate the active and passive seismic stability of shallow shield tunnel faces. The outcrop failure model and inside failure model are provided for active failure analysis. To capture the spatiotemporal variations of seismic loading, the pseudodynamic approach is employed to assess the limit active and passive support pressures. Comparisons with published studies and numerical simulations demonstrate that the proposed 3D approach greatly improves existing 2D results for limit active and passive support pressures. A detailed investigation is then conducted to analyze the effects of pseudodynamic parameters, surface surcharge, and buried depth on face stability of shallow tunnels. Finally, the proposed approach is further tested by conducting the seismic face stability analysis of Changsha Metro 2 tunnel based on actual seismic response. The results indicate that the surface surcharge has a greater influence on limit passive support pressure than limit active support pressure, and increasing of buried depth leads to a larger safety range of limit support pressure. Practical Applications: Active and passive face failure of shallow tunnels under earthquakes can endanger the safety of tunnels and ground surfaces, leading to severe casualties and property losses. Determination of limit support pressures under seismic forces is a critical task in shield tunnel construction. This work establishes an approach to assess 3D active and passive seismic stability of shallow shield tunnel faces. Time–space variations of seismic loading are incorporated to accurately determine limit active and passive support pressures using pseudodynamic approach. Effects of seismic parameters, surface surcharge, and buried depth on face stability of shallow tunnels are then presented and discussed. Finally, the proposed approach is tested by conducting the seismic face stability analysis of Changsha Metro 2 tunnel based on actual seismic response. The results indicate that surface surcharge has a greater influence on limit passive support pressure compared with limit active support pressure, and increasing buried depth leads to a larger safety range of limit support pressure. The proposed approach determines a safety range of limit support pressures more accurately for shallow shield tunnels during earthquakes. [ABSTRACT FROM AUTHOR]

A self-centering isolated pier (SIP) with an elliptical rocking interface is proposed to enhance the seismic performance of bridge piers. Pseudostatic tests were conducted on two SIPs (one with and the other without tie bars) to study their damage patterns and hysteretic characteristics. Additionally, a finite-element model of a SIP was constructed to study the effect of SIP parameters on its hysteretic characteristics, such as the long radius of the ellipse, the ratio of the long to the short radii of the ellipse, the distance from the tie bar to the centerline of the pier, and the axial compression ratio. The results indicated that the pier bodies of the two SIPs are in the elastic stage. Increasing the long radius of the ellipse and axial compression ratio can enhance the hysteretic characteristics of the SIP. However, these larger values could lead to yield failure of the pier bottom. Furthermore, an increase in the ratio of the long to the short radii of the ellipse results in a progressively less plump hysteretic curve for the SIP, leading to a reduction in energy dissipation capacity. Nevertheless, an increase in this ratio can improve the self-centering ability of SIPs. The distance from the tie bar to the centerline of the pier has little effect on hysteretic characteristics of the SIP. [ABSTRACT FROM AUTHOR]

Borehole strain gauges play a crucial role in geophysical, seismological, and crustal dynamics studies. While existing borehole strain gauges are proficient in measuring horizontal strains within vertical boreholes, their effectiveness in capturing vertical and oblique strains is limited due to technical constraints arising from the cylindrical probe's characteristics. However, the accurate measurement of three-dimensional strain is essential for a comprehensive understanding of crustal tectonics, dynamics, and geophysics, particularly considering the diverse geological structures and force sources within the crustal medium. In this study, we present a novel approach to address this challenge by enhancing an existing horizontal-component borehole strain gauge with a bellows structure and line strain measurement technology to enable vertical and borehole oblique strain measurements. Integrating these enhancements with horizontal strain measurement capabilities enables comprehensive three-dimensional borehole strain measurements within the same hole section. The system was deployed and tested at the Gongxian seismic station in Sichuan Province. Clear observations of solid tides were recorded across horizontal, oblique, and vertical measurement units, with the tidal morphology and amplitude being consistent with the theoretical calculations. The achieved measurement sensitivity of 10-10 meets the requirements for borehole strain measurement, enabling the characterization of three-dimensional strain states within boreholes through association methods. [ABSTRACT FROM AUTHOR]

To realize the prefabricated structure of special‐shaped concrete‐filled steel tubular (CFST) column frame and enhance the level of indoor room utilization, this paper proposed a novel prefabricated frame with special‐shaped CFST columns and H‐shape steel beams connection with side plate. To investigate seismic behavior of this prefabricated frame structure, a 2‐story and 2‐bay CFST frame specimen was fabricated and tested under reversed cyclic loading. The failure mode, hysteresis behavior, degradation of lateral stiffness and bearing capacity, ductility and energy dissipation were analyzed. Experiment results indicated that failure mode presented strong columns and weak beams. Hysteresis curve of frame showed fully shuttle‐shaped. The mean story drift angle was 1/36 at ultimate stage. Equivalent viscous damping coefficient was 0.038–0.464. The bearing capacity degradation was relatively gentle, but the overall stiffness degradation was more obvious. It suggested that the frame had proper seismic and energy dissipation property. After the test, the seismic property of test frame was further investigated through the numerical simulation approach. The failure mode and skeleton curve obtained from the simulation were nearly consistent with test results, indicating that numerical analysis results were precise and with high reference meaning. [ABSTRACT FROM AUTHOR]

This study aims to characterize the frequency magnitude distribution factor (b-value) for Nepal and its surrounding area-thereby focusing on conducting spatiotemporal and depth-wise analysis of b-value fluctuations before the November 9, 2022 earthquake of magnitude MW 6.3. Using the non-parametric Kolmogorov–Smirnov (K–S) test, earthquake events with a magnitude MW ≥ 3.5 reported between 1900 and 2022 from the earthquake catalog compiled by the International Seismological Centre (ISC) and the United States Geological Survey (USGS) were analysed. We determined the minimum magnitude of completeness (MC) using the Maximum Curvature Method (MAXC). Furthermore, we divided the study region into equal-sized square grids and computed b-values using the maximum likelihood technique for each grid. We analysed the relationship between the b-value and seismic parameters such as focal depth, seismic moment release, and radon gas anomalies, along with their spatial correlations and patterns. Results indicate minimal seismicity in the lower crust compared to the upper crust and lead to establish an inverse relationship between the b-value and seismic moment release. We established plausible correlations between temporal variations of the b-value and variations in radon gas concentration as an earthquake precursor in different medium. Additionally, we utilized the Gumbel extreme value theory to estimate the mean return period, the most likely maximum yearly earthquake, and probabilities of recurrence of different magnitudes across different periods for credible seismic hazard analysis. We found the most likely maximum yearly earthquake for the region to be 5.53, with a mean return period of 5 years for the November 9, 2022 earthquake. The mean return period of earthquakes with magnitudes ranging from 5.0 to 6.5 (MW) was estimated to be 5–10 years. These findings contribute to a better understanding of the intricate seismotectonic configuration of the region and serve as earthquake precursors for potential future destructive earthquakes. [ABSTRACT FROM AUTHOR]

A shaking table test of a 1/60 scale cross-fault bridge model considering the effects of soil–bridge interactions was designed and implemented, in which the bridge model was placed in two individual soil boxes to simulate the bridge across a strike-slip fault. Three seismic ground motion time-histories with permanent displacements were selected as input excitations to investigate the influence of seismic ground motions with different frequency characteristics on the seismic response of the testing soil–bridge model. The one-side input method was used to simulate the seismic response of bridges across faults. The seismic responses of the soil and bridge in terms of acceleration, strain, and displacement were analyzed. The test results show that the one-side input method can simulate the seismic response of the main girder displacements well and the displacements and strains of piers and piles of the bridge structure spanning a fault. The strain responses at near-fault pile foundations are much larger than those farther away from the fault. Compared with other bridges, the cross-fault bridge is more prone to torsional and displacement responses during earthquakes. Surface fault rupture can lead to permanent inclination of the bridge piers, which should be paid more attention to in the practical engineering design of the bridges. Soil–bridge interactions can suppress the amplification effect of soil on ground motions. The test results can provide a reference for future research and the design of cross-fault bridges. [ABSTRACT FROM AUTHOR]

Comprehensive field investigations into the axial cyclic loading behaviour of open steel pipe piles driven and aged in low-to-medium-density chalk identify the conditions under which behaviour is stable, unstable or metastable. Post-cycling monotonic tests confirmed that stable cycling enhanced pile capacity marginally, while unstable cases suffered potentially large losses of shaft capacity. Metastable conditions led to intermediate outcomes. The patterns by which axial deflections grew under cyclic loading varied systematically with the normalised loading parameters and could be captured by simple fitting expressions. Cyclic stiffnesses also varied with loading conditions, with the highest operational shear stiffnesses falling far below the in situ seismic test values. The monotonic and cyclic axial responses of the test piles were controlled by the behaviour of, and conditions within, the reconsolidated, de-structured, chalk putty annuli formed around pile shafts during driving. Fibre-optic strain gauges identified progressive failure from the pile tip upwards. Large factors of safety were required for piles to survive repetitive loading under high-level, two-way conditions involving low mean loads, while low-amplitude one-way cycling had little impact. A simple 'global' prediction procedure employing interface shear and cyclic triaxial tests is shown to provide broadly representative predictions for field behaviour. [ABSTRACT FROM AUTHOR]

The nondestructive spectral analysis of surface waves (SASW) technique determines the shear wave velocities along the wide wavelength range using Rayleigh-type surface waves that propagate along pairs of receivers on the surface. The typical configuration of source-receivers consists of a vertical source and three vertical receivers arranged in a linear array. While this approach allows for effective site characterization, laterally variable sites are often challenging to characterize. In addition, in a traditional SASW test configuration system, where sources are placed in one direction, the data are collected more on one side, which can cause an imbalance in the interpretation of the data. Data interpretation issues can be resolved by moving the source to opposite ends of the original array and relocating receivers to perform a second complete set of tests. Consequently, two different Vs profiles can be provided with only a small amount of additional time at sites where lateral variability exists. Furthermore, the testing procedure can be modified to enhance the site characterization during data collection. The advantages of performing SASW testing in both directions are discussed using a real case study. [ABSTRACT FROM AUTHOR]

The seismic performance of arch bridges is dependent on the strength of bridges and the built-on soil site types. To investigate the influence of soil-structure interaction (SSI) on the seismic response of an arch-foot arch bridge with a sand-gravel soil site, several shaking-table tests for a 1/90 downscaled arch-foot model placed on sand-gravel soil were conducted based on the engineering prototype of the third Pingnan Bridge with a long-span concrete-filled steel-tube (CFST) arch bridge. The test results showed the following: (1) The seismic acceleration response of both the sand-gravel soil site and arch foot were amplified, which is related to both the non-linear dynamic behavior of sand-gravel soil and frequency-spectrum characteristics of the input seismic waves. (2) The sliding displacement of the arch foot under strong ground motions increased accompanied with a settlement of the soil surface. However, the safety risk of the arch foot may be underestimated in seismic design. (3) The dynamic shear stress-strain loops of sand-gravel soil exhibited a high-energy dissipation capacity, and the energy-transfer mechanism at the interface between the model soil and arch foot was integrated. The results obtained are expected to provide insights into the dynamic interaction behavior of the gravel soil and arch bridge systems and the seismic design of arch bridges built on sand-gravel soil sites in practical engineering. [ABSTRACT FROM AUTHOR]

This paper presents an extensive numerical study on the seismic performance of steel eccentrically braced frames (EBFs) designed according to the ASCE 7-16 standard. A series of EBF building structures ranging from 2 to 12 stories located in downtown Los Angeles are designed with different yielding links, including conventional and replaceable links. The performance of the structures is investigated through nonlinear time-history analyses (NLTHAs) under a suite of 40 ground motions, selected and scaled to match the target uniform hazard spectrum. The peak deformations are first examined to assess the performance of the buildings as well as the design procedure. Residual deformations are also evaluated and critically compared with acceptable limits, to provide insight into the downtime and recovery time of EBFs after major earthquakes. Previous studies have demonstrated that the response of stable yielding systems to major earthquakes is often accompanied by significant residual deformations, and that residual drifts exceeding 0.5% can cause hindrance to the buildings occupants. In EBFs, in addition to residual drifts, residual link rotations are also relevant and expected to be more severe due to the localization of inelastic deformations in the yielding link. For replaceable modular yielding links, significant residual link rotations after major earthquakes will hinder repairs and the link replacement process, which is one of the important design objectives. The performance of EBFs is also compared with what was observed in previous studies for buckling restrained braced frames and special moment resisting frames. In the end, the results from the extensive NLTHAs are used to establish a relationship between peak drifts and peak link rotations in EBFs. [ABSTRACT FROM AUTHOR]

The choice of stiffness profile can be crucial in a site response analysis. This research aims to study site response predictions at the large-scale seismic test site in Lotung, Taiwan, employing three different approaches to choosing the stiffness profile in nonlinear and equivalent linear analyses. These approaches consider point average, layer average, and deposit average stiffness profiles. One strong and one weak earthquake event recorded at the site are simulated with these three stiffness profile approaches. Moreover, the stiffness profiles are tested under sets of seven modified real input motions (selected from the European Strong-Motion Database) at various seismic intensity levels. The results indicate that the different stiffness profiles have a minimal effect on the nonlinear site response predictions, in particular for input motions having a PGA greater than or equal to 0.05 g. The spectral acceleration values and PGA and shear strain profiles from nonlinear site response analyses change negligibly when using different approaches to derive the stiffness profile. In the equivalent linear site response analysis, the spectral acceleration predictions are strongly influenced by the stiffness profile approach, regardless of the PGA level of the input motions. The stiffness profile has a more significant role in equivalent linear site response analysis than in nonlinear site response analysis. Therefore, the point average stiffness profile should be used in equivalent linear site response analysis. [ABSTRACT FROM AUTHOR]

Soil microstructure, often defined as the combination of particle arrangement and bonding, can strongly influence the stiffness and strength of sedimentary deposits. As undisturbed soil sampling is a challenging task in fine-grained soils, seismic in situ testing is becoming increasingly more important to investigate its mechanical behaviour. The aim of this article is to evaluate the influences of sediment depositional age and structure-forming processes on the degree of soil structure development in Alpine deposits. Seismic in situ and laboratory testing comprising X-ray diffraction (XRD), scanning electron microscopy (SEM), pore water chemical analysis and hydrochemical modelling were executed at three Austrian test sites, namely Lokalbahn Salzburg, Rhesi and water reservoir Raggal. Based on the comparison of in situ shear wave velocities (VS,SDMT) with bender element results (VS,BE), executed on reconstituted soil specimens, it is shown that the Pleisto–Holocene-aged deposits are characterized by a VS,BE/VS,SDMT ratio of < 1, indicating the presence of microstructure. However, the youngest sediments (< 50 years) exhibit the weakest microstructure (VS,BE/VS,SDMT ≈ 1). The increase of soil structure with sediment age is represented by the updated normalized small-strain rigidity index, K*G, which is situated at the proposed transition between structured and unstructured soils (K*G = 330), ranging between 250 and 350, at all test sites. The development of microstructure can be attributed to the precipitation of calcite (CaCO3) cements in open pores, which strengthens the interparticle bonding between detrital quartz, feldspar, clay minerals and carbonate grains, subsequently reducing the soil's porosity with increasing sediment age. [ABSTRACT FROM AUTHOR]

The traveling wave effect and soil–structure interaction have significant influence on the seismic response of large-span bridges with complex site conditions. In this paper, a 1/10 scaled-down large-span rigid-framed bridge model was designed and fabricated, and a shaking tables test considering the traveling wave effect and soil–structure interaction was carried out on a large-scale continuous rigid bridge model by a real-time substructure hybrid test technique. Influences of the traveling wave effect and soil–structure interaction on the seismic responses of the rigid-framed bridge specimen were systematically analyzed with experimental data. The test results showed that when the apparent wave speed was small, the traveling wave effect increased the seismic responses of the rigid-framed bridge. With the increase in apparent wave speed, the structural response under traveling wave excitation and uniform excitation was basically the same. The SSI effect lead to a great change in the seismic input peaks and spectral characters at the bottom of the pier, and increased the seismic responses of the rigid-framed bridge. When both traveling wave and the SSI effect were considered, there was a phase difference in the seismic excitation. The dynamic responses of a continuous rigid-framed bridge could not be simply obtained by superposition of the separate traveling wave effect or SSI effect. Meanwhile, the real-time substructure test method in this paper solved the problems that the traditional soil box experiment cannot be applied to the test of a large-scale model, the soil and bridge structure find it difficult to meet the unified similarity ratio, and the boundary conditions are difficult to simulate accurately. [ABSTRACT FROM AUTHOR]

A trigger system is typically employed in active seismic testing to trigger and synchronize multichannel surface wave data acquisition. The effect of the trigger system on the dispersion image of surface waves is empirically known to be negligible, however, theoretical explanation regarding the effect of the trigger system is insufficient. This study systematically examines the theory for surface wave dispersion analysis and proves that the effect of the trigger system on a dispersion image is negligible via a solid theoretical explanation. Subsequently, based on the new theoretical explanation, an alternative method that uses only the relative phase difference between sensors to extract dispersion characteristics with better conceptual clarity is proposed. Two active surface wave testing cases are considered to validate the theory and method. The results indicate that (1) an accurate trigger system is not necessary for surface wave data acquisition, and (2) it is unnecessary to assume that the impact point is the generation point of the surface waves for the experimental dispersion analysis. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tube (CFST) arch bridges have a high center of gravity and a substantial mass, resulting in a discernible seismic response. Consequently, long-span CFST arch bridges must retain exceptional seismic performance and appropriate seismic control design. In this study, the dynamic response and seismic performance of a unique swallow-type CFST arch bridge when subjected to longitudinal earthquake forces were analyzed using numerical simulation methods. The displacement and axial force response results and their laws of the key bridge components were obtained. Taking into account seismic checking calculations, two damping measures were proposed for the CFST arch bridge, as the relative displacement of the girder end exceeded the allowable value specified. The appropriate design parameters for viscous dampers and lead shear dampers were examined. Additionally, the seismic performance of these dampers was verified through a shaking table test using a 1:16 scale model. The findings indicated that when subjected to Wenchuan Wolong wave action, the relative displacement between the steel box girder and the concrete girder of the bridge was significantly larger, leading to girder end pounding. The limit values were surpassed by 32.5% and 50%, when subjected to the uniform and traveling wave excitations, respectively, thus indicating that the expansion joint was the most vulnerable component. Following the selection of optimal parameters for the dampers, the dampers exhibited the capability to mitigate seismic and pounding impacts. Long-span CFST arch bridges with dampers were found to effectively reduce the seismic response of the skewback strain and vault, as well as the relative displacement of the girder ends. Furthermore, the average maximum damping rates achieved by the viscous damper and the lead shear damper reached 44.9% and 44.6%, respectively. [ABSTRACT FROM AUTHOR]

A viscoelastic damper (VED) reinforcement option focusing on recovering the seismic performance of earthquake-damaged historic timber structures on a slope, as regulated by a direct displacement-based design procedure, was proposed in an attempt to extend the service life of culture buildings while ensuring deformation control of the weak area. A timber frame with an unequal height of column feet (UF) was designed, and a timber frame with an equal height of column feet (EF) served as the control group. The two full-scale timber frames consist of two-story units, a roof, and four spans. A series of cyclic loading tests were conducted on Models EF and UF to investigate the seismic performance of timber frames before and after reinforcement. It was found that the pulling out of the tenon and the sliding of column feet was significant at the upper embedding end. The upper embedding story is the weak area of the timber structure on a slope. The damage patterns of the two damped frames were not significantly different from those of the corresponding bare frames, and the ductility coefficients of all tested frames were greater than 10. The test results also revealed that the designed VED restored the seismic performance of the UF to the undamaged level while effectively controlling the deformation of its weak area. In addition, the effect of uniformly arranged dampers on the seismic performance of timber frame UF was also investigated. [ABSTRACT FROM AUTHOR]

This paper presents the design and commissioning of a novel pseudo‐static test apparatus for underground structures that accounts for soil‐structure interaction by simulating the soil with suitably designed springs. The developed apparatus was employed to conduct 1:10 large scale tests on a two‐story three‐span prefabricated subway station structure. Two comparative cyclic load tests were conducted: one involved the developed springs‐structure system; and one involved the structure alone (no springs). The test results demonstrated important differences in the damage location, damage degree, bearing capacity, and deformation capacity of the prefabricated subway station structure under the two loading conditions (i.e., with and without springs). The presence of springs (i.e., soil‐structure interaction) enhanced the lateral collapse resistance of the underground structure and affected the inter‐story displacement ratio (IDR) between the upper and lower layers of the two‐story prefabricated subway station structure. However, it did not affect the deformation coordination of the walls and columns of each layer. A finite element model of the prototype station was also established to conduct dynamic time history analysis simulating the soil‐structure interaction. The results from the dynamic analysis validated the effectiveness of the pseudo‐static test method employing the spring‐structure system. The excellent agreement between the calculated dynamic responses and the responses obtained from the pseudo static tests confirmed the ability of the developed apparatus to conduct seismic tests on complex large‐scale underground structures such as prefabricated subway stations. Thus, this test methodology might be utilized to attain valuable insights into the seismic performance of prefabricated subway stations at a relatively low cost and effort. [ABSTRACT FROM AUTHOR]

When subjected to seismic activity, tall isolated buildings with a high aspect ratio are susceptible to overturning as a result of the failure of rubber isolation bearings under tension. In order to address this issue, a guided-rail tension device (GR) has been developed to enhance the tensile strength of rubber bearings. Furthermore, a novel guided-rail isolation rubber bearing (GR&RB) has been proposed as a potential solution. Quasi-static tests have been conducted to investigate the mechanical properties of the GR, as well as the GR&LNR600 and LNR600. Additionally, numerical finite element analysis has been employed to study the seismic response of the GR&RB under El Centro seismic action in a high-rise building with an aspect ratio of approximately 4. The experimental results suggest that the inclusion of GRs has a limited effect on the horizontal mechanical attributes of rubber isolation bearings. Nevertheless, it simultaneously enhances their tensile strength, demonstrating a significant augmentation of 4.23 times. Moreover, the mechanical behavior of the GR aligns with the Hook model. The numerical analysis suggests that the utilization of GR&RB can mitigate the tensile stress levels of rubber isolators. Furthermore, it is recommended to augment the elastic tensile stiffness of the GR while reducing the open value to enhance the tensile efficiency, with the potential to attain up to 75% efficiency in tensile performance. [ABSTRACT FROM AUTHOR]

In shallow-water ocean-bottom cable (OBC) seismic data, the ineffectiveness of conventional surface-related multiple elimination (SRME) methods due to poor seabed records is addressed. This research utilizes the seismic wavefield received by multiple cables from a single shot gather to predict shallow water multiple models for that shot gather. Initially, the seismic data within a finite aperture around a seismic trace in the time domain shot gather is treated as the known seismic wavefield. This seismic wavefield is then extrapolated along the water layer to this seismic trace, following the Fresnel diffraction principle. The extrapolated data becomes the shallow water multiple model for this seismic trace. This process is repeated for each trace in the shot gather to obtain the shallow water multiple model of the entire shot gather. Forward modeling tests have shown that smaller data apertures can effectively avoid the impact of spatial aliasing on multiple model prediction. To address the overlap of primary waves and shallow water multiples in deep seismic data, which have lower dominant frequencies, the multiple model data is used as a known seismic wavefield and extrapolated along the water layer again. This produces second-order and higher-order multiple models. Applying this model to suppress multiple waves can minimize primary waves loss. This entirely data-driven approach necessitates solely water depth information, imposing no additional conditions. Both forward modeling and real seismic data testing validate the efficacy of this method in shallow water. [ABSTRACT FROM AUTHOR]

This paper introduces a novel wavelet-based methodology for identifying the modal parameters of a structure in the aftermath of an earthquake. Our proposed approach seamlessly combines a subspace method with a stationary wavelet packet transform. By relocating the subspace method into the wavelet domain and introducing a weighting function, complemented by a moving window technique, the efficiency of our approach is significantly augmented. This enhancement ensures the precise identification of the time-varying modal parameters of a structure. The capacity of the stationary wavelet packet transform for rich signal decomposition and exceptional time-frequency localization is harnessed in our approach. Different subspaces within the stationary wavelet packet transform encapsulate signals with distinct frequency sub-bands, leveraging the fine filtering property to not only discern modes with pronounced modal interference, but also identify numerous modes from the responses of a limited number of measured degrees of freedom. To validate our methodology, we processed numerically simulated responses of both time-invariant and time-varying six-floor shear buildings, accounting for noise and incomplete measurements. Additionally, our approach was applied to the seismic responses of a cable-stayed bridge and the nonlinear responses of a five-story steel frame during a shaking table test. The identified modal parameters were meticulously compared with published results, underscoring the applicability and reliability of our approach for processing real measured data. [ABSTRACT FROM AUTHOR]

Spectral transform, known as a curvelet, enables sparse representations of complex data. Denoising wave propagation in disordered media and pattern recognition are just a few of the numerous domains in which denoising has a potential application. Based on directional basis functions, this spectral method represents objects with discontinuities along a smooth curve. In this study, we used this technique to eliminate ground roll, an unwanted feature signal that can be seen in seismic data obtained by sonating the earth's geological formations. Additionally, we improved the curvelet transform threshold denoising method combined with a fast non-local mean to remove seismic random noise. First, cyclic translation and block complex domain threshold methods were introduced into the curvelet transform threshold denoising, and the traditional curvelet threshold denoising method was improved to obtain the best denoising results; Subsequently, the removed noise was filtered using a fast non-local mean method to obtain a valid signal. Finally, the data obtained in the above two steps were added to obtain the final denoising result. The results of the model tests and actual seismic data denoising showed that the denoising results obtained using this method had a higher signal-to-noise ratio and fidelity than that using the other methods. [ABSTRACT FROM AUTHOR]

Assessing the constrained modulus is a critical step in calculating settlements in granular soils. This paper describes a novel concept of how the constrained modulus can be derived from seismic tests. The advantages and limitations of seismic laboratory and field tests are addressed. Based on a comprehensive review of laboratory resonant column and torsional shear tests, the most important parameters affecting the shear modulus, such as shear strain and confining stress, are defined quantitatively. Also, Poisson's ratio, which is needed to convert shear modulus to constrained modulus, is strain-dependent. An empirical relationship is presented from which the variation in the secant shear modulus with shear strain can be defined numerically within a broad strain range (10−4–10−0.5%). The tangent shear modulus was obtained by differentiating the secant shear modulus. According to the tangent modulus concept, the tangent constrained modulus is governed by the modulus number, m, and the stress exponent, j. Laboratory test results on granular soils are reviewed, based on which it is possible to estimate the modulus number during virgin loading and unloading/reloading. A correlation is proposed between the small-strain shear modulus, G0, and the modulus number, m. The modulus number can also be derived from static cone penetration tests, provided that the cone resistance is adjusted with respect to the mean effective stress. In a companion paper, the concepts presented in this paper are applied to data from an experimental site, where different types of seismic tests and cone penetration tests were performed. [ABSTRACT FROM AUTHOR]

The seismic response of buried pipeline is significantly affected by the soil around the pipeline. In this study, a numerical analysis model of the pipeline and the soil around the pipeline is built, and the finite element numerical analysis of its seismic response law is conducted to address the problem of pipeline soil seismic coupling response. A shaking table test of the seismic response of buried pipeline under two-way seismic excitation is performed based on the developed two-way layered shear continuum model soil box. The peak strain response at the middle section of the pipeline grows fastest, the peak strain of the pipeline under non-uniform seismic excitation constantly exceeds that under uniform excitation, and the axial strain of the pipeline exhibits more sensitivity to earthquake than the bending strain, as indicated by the results of numerical analysis and shaking table test. The peak value of soil acceleration response under non-uniform excitation exceeds under uniform excitation. The displacement of soil increases with the height. The pipeline soil interaction becomes more intense under non-uniform excitation, and the relative movement between pipeline and soil becomes more significant. The seismic excitation more significantly affects the axial displacement of soil. The peak value of soil acceleration response varies from larger along the pipeline to larger along the axis with the increase of the loading grade. A slight difference exists between the peak value of axial and transverse acceleration response of the pipeline. The peak value of pipeline acceleration response declines in the axial direction than the peak value of soil acceleration response, whereas it rises in the transverse direction than the peak value of soil acceleration response, especially under non-uniform excitation. As revealed by the above results, the effect of bidirectional non-uniform seismic excitation on the lateral pipeline soil interaction is enhanced, and soil is more seriously damaged. [ABSTRACT FROM AUTHOR]

This paper focuses on the seismic response of symmetrical underground subway stations to seismic waves with varying frequencies and peak ground accelerations (PGAs), essential in light of growing urban underground transit systems. A 1/40 scale station model was subjected to seismic simulations using waves from the Wenchuan and Tangshan earthquakes and an artificial wave spanning 0.1 g to 0.5 g PGAs. Shaking table tests revealed that seismic impacts divide at PGA = 0.3 g; high-frequency waves affect structures more below this threshold, while low-frequency waves have more impact above it. The columns on the third basement level responded more to seismic activity, particularly at their base. The study recommends prioritizing the seismic design of these columns during station construction, especially in earthquake-prone zones. Understanding the dynamic effects of different frequencies and amplitudes is crucial for selecting and reinforcing materials and structural designs to enhance seismic resistance. [ABSTRACT FROM AUTHOR]

In order to investigate the deformation behavior, mechanical characteristics of connections, and failure mode of translational precast concrete wall-panels under earthquake loading, a full-scale two-story steel frame model was designed. This test model consisted of 12 precast concrete wall-panels connected with fixed connections at the bottom end and translational-type connections at the top end. This model passed the shaking table testing, and the results demonstrate that the translational-type precast concrete exterior wall panel can ensure the sufficient relative displacement between the wall panel and the main structure under large earthquake loads. It has sufficient capacity to adapt the deformation between the main structure and the wall panels. During the test, localized cracking was observed on the wall panel, while all connections remained in elastic state. The connections between precast concrete exterior wall panels exhibited good performance, that indicates it is an effective tool to protect frame building hangings with exterior wall panels under strong earthquake events. [ABSTRACT FROM AUTHOR]

Determining the elastic modulus of rocks is one of the crucial parameters in civil and petroleum engineering. Asmari geological formation is widely outcropped in a significant part of the west and SW of Iran and NE of Iraq. Understanding the static elastic modulus of host rocks is crucial because of the design and construction of numerous geotechnical structures and the presence of large hydrocarbon reservoirs in this formation. To determine the elastic modulus of intact rocks, the uniaxial compressive strength test is typically used. However, in jointed rocks and deep areas, where obtaining samples may be challenging, costly, or even impossible, correlations between static–dynamic elastic modulus (Es − Ed) is more frequently employed. Although some scholars have proposed correlations between Es − Ed, they had determined dynamic modules based on the ultrasonic test. In the aforementioned test, intact samples are used and the effect of discontinuities would not be considered; hence, the results cannot be considered as rock mass representative. In this study, to consider field geotechnical conditions, the dynamic modules were determined based on the downhole seismic test (DS) in a tunnel in located the west of Iran. Then from the results of static elastic modulus, which were obtained from core samples, a linear correlation was proposed between Es − Ed. The root-mean-square error and variance accounted showed that the predicted static elastic modulus by the proposed correlation is more accurate to a large extent. In addition, unlike the ultrasonic-based Ed, the results showed that the DS-based Ed is less than Es. [ABSTRACT FROM AUTHOR]

Summary: Recycled steel wire is taken from used tires, and by procedures like mechanical cutting and friction treatment, it can be converted into industrial recycled steel fiber that meets precise criteria. Such green fiber may effectively limit the growth of fractures in concrete and diffuse the fracture energy of concrete when incorporated into concrete. An investigation of the effects of materials and horizontal reinforcement spacing on the seismic performance of shear wall specimens is presented in this research. The test and numerical simulation findings indicate that the RSFRC (recycled steel fiber reinforced concrete) shear wall's fracture is substantially narrower than that of a conventional shear wall and that the shear carrying capacity and deformation ductility of the shear wall have been greatly enhanced. The energy dissipation capacity of the RSFRC shear wall specimen with varying horizontal reinforcement spacing is significantly enhanced when compared to the conventional shear wall, and the ultimate displacements are reduced. RSFRC shear wall specimen has higher stiffness in the early stage, and the overall stiffness decreases slowly. With the decrease of fiber volume fraction of RSFRC shear wall in a certain range, the shear bearing capacity and stiffness of the model will decrease slightly, but the ductility will increase significantly. Compared with the RSFRC shear wall with fiber aspect ratio of 40 and 25, the bearing capacity and ductility of the two are close, but the RSFRC shear wall with low aspect ratio is slightly insufficient. When the axial compression ratio is in the range of 0.2–0.4, the horizontal shear capacity of RSFRC shear wall increases with the increase of vertical load, but the maximum horizontal displacement becomes smaller, and the model is damaged by compression. Using theoretical calculation, this work also creates the simplified calculation method and restoring force model for the bearing capacity of the diagonal section of RSFRC shear wall. The observed findings correspond well with the test hysteresis curve and may serve as a benchmark for future study. This study provides a new research direction for the seismic performance of RSFRC structures, as well as a solid theoretical foundation and promotion for future research. [ABSTRACT FROM AUTHOR]

Various lab-scale friction tests and seismic observations have highlighted the role of fault gauges in earthquake initiation in geological faults. These fault gauges consist of particles accumulated over thousands of years due to surface wear caused by friction. Understanding their properties is crucial as they significantly influence both the frictional strength and sliding stability of faults. This study investigates the friction stability parameter (a-b) under loading rates of 0.2-25 μΐΓΐ/s using velocity step tests on gypsum fault gauges under a low normal stress condition (0.9 MPa) and steady-state velocity step tests on fault gauges composed of varying ratios of kaolinite/calcite mixture under an effective normal stress of 3 MPa. The conclusions drawn from this study are as follows: 1) The (a-b) values obtained from near steady-state velocity step tests on gypsum fault gauges and those reported in previous studies under similar conditions were both negative. However, our results show that the former values were one order of magnitude lower than the latter, indicating a higher susceptibility to velocity weakening. 2) Steady-statevelocity steptests on the kaolinite/calcite mixture fault gauges demonstrated positive (a-b) values for all mixtures with varying kaolinite contents. Moreover, the (a-b) values were proportional to the kaolinite content. We established a functional relationship between the (a-b) values of the mixture fault gauge and the mass fraction of kaolinite, providing valuable insights for future experiments and numerical simulations related to fault stability. [ABSTRACT FROM AUTHOR]

On the basis of the highway subgrade construction of North Hobson Salt Lake mining area in Qinghai Province, the soil samples of high saline saturated sand adjacent to the salt lake were remolded, and four types of saturated sand containing 0%, 10%, 20%, and 30% salt were configured respectively, so as to explore the liquefaction effect of saline saturated sand under seismic load. After the indoor geotechnical test, the soil samples were reshaped, The liquefaction test of saline saturated sand was carried out by using the GDS dynamic triaxial device to simulate seismic load to investigate the liquefaction mechanism of saturated sand under different salt contents and verify the liquefaction discrimination standard, then based on the data of dynamic elastic modulus, dynamic shear modulus, damping ratio coefficient, and soil density obtained from previous soil tests and dynamic triaxial tests, four subgrade models with different salt contents were constructed using ANSYS simulation software according to actual engineering, and the settlement and deformation of the subgrade were analyzed by inputting EL-concrete seismic waves. The results show that the maximum value of axial stress of saturated sand decreases with the increase of salt content; the load vibration times of saline saturated sand reaching the initial liquefaction state are more than that of common saturated sand; the higher the salt content, the weaker the liquefaction resistance of saturated sand; when the pore pressure ratio coefficient reaches 1, the axial double amplitude strain εd of the soil also reaches 5%, and the soil reaches the initial liquefaction state; the area of shear stress and strain hysteresis curve increases with vibration load, and the elastic modulus decreases gradually; the shear dilation and compaction effects occur in each hysteresis cycle, and the former is greater than the latter, the research results have guiding significance for similar studies in highly saline saturated sand areas. [ABSTRACT FROM AUTHOR]