To evaluate the beneficial effect of rubber bearings on the seismic performance of underground station structures, three-dimensional finite element models of seismic soil-structural systems are established for a single-layer double span subway station. The seismic mitigation effect is investigated by employing the pushover analysis method. The obtained results indicated that the installation of rubber bearings can effectively alleviate stress concentration and damage degree of the central column, especially at its end area. Compared with the conventional column, the elastic and elastoplastic deformation capacity of the column fitted with rubber bearings both improved significantly. It was also found that the load bearing and deformation performance decrease with the increase of the axial pressure ratio. Furthermore, the lateral force distribution mechanism of the structural system fitted with the rubber bearings is significantly different from the original structure; the deformation and internal forces of central column of the seismic mitigation structure decreased substantially, but side walls' deformation and internal forces increased slightly. The proportion of shear force taken by the central column has decreased, while the side walls have taken larger share, i.e., the rubber bearings facilitated the transfer of seismic forces from the middle column to the side wall.

This paper presents a comprehensive on-site decision-making framework for assessing the structural integrity of a jacket-type offshore platform in the Gulf of Mexico, installed at a water depth of 50 m. Six critical analyses-(i) static operation and storm, (ii) dynamic storm, (iii) strength-level seismic, (iv) seismic ductility (pushover), (v) maximum wave resistance (pushover), and (vi) spectral fatigue-are performed using SACS V16 software to capture both linear and nonlinear interactions among the soil, piles, and superstructure. The environmental conditions include multi-directional wind, waves, currents, and seismic loads. In the static linear analyses (i, ii, and iii), the overall results confirm that the unity checks (UCs) for structural members, tubular joints, and piles remain below allowable thresholds (UC < 1.0), thus meeting API RP 2A-WSD, AISC, IMCA, and Pemex P.2.0130.01-2015 standards for different load demands. However, these three analyses also show hydrostatic collapse due to water pressure on submerged elements, which is mitigated by installing stiffening rings in the tubular components. The dynamic analyses (ii and iii) reveal how generalized mass and mass participation factors influence structural behavior by generating various vibration modes with different periods. They also include a load comparison under different damping values, selecting the most unfavorable scenario. The nonlinear analyses (iv and v) provide collapse factors (Cr = 8.53 and RSR = 2.68) that exceed the minimum requirements; these analyses pinpoint the onset of plasticization in specific elements, identify their collapse mechanism, and illustrate corresponding load-displacement curves. Finally, spectral fatigue assessments indicate that most tubular joints meet or exceed their design life, except for one joint (node 370). This joint's service life extends from 9.3 years to 27.0 years by applying a burr grinding weld-profiling technique, making it compliant with the fatigue criteria. By systematically combining linear, nonlinear, and fatigue-based analyses, the proposed framework enables robust multi-hazard verification of marine platforms. It provides operators and engineers with clear strategies for reinforcing existing structures and guiding future developments to ensure safe long-term performance.

The 7.7 and 7.6 magnitude Pazarc & imath;k and Elbistan earthquakes that struck Kahramanmara & scedil; on 6 February 2023 caused widespread structural damage across many provinces and are considered rare in seismological terms. While many reinforced concrete (RC) buildings designed under current earthquake regulations sustained significant damage, some older RC buildings with outdated designs sustained only moderate damage. This study aims to analyze the seismic performance of such older RC buildings to understand why they did not collapse or suffer severe damage. An 8-story RC building in Ad & imath;yaman province, damaged by the earthquake, was considered for analysis. The region's seismicity and local site conditions were assessed through borehole operations, geotechnical laboratory tests, and seismic field tests. The soil profile was modeled, and one-dimensional seismic site response analyses were performed using records from nearby stations (TK 4615 Pazarc & imath;k and TK 4612 G & ouml;ksun stations) to determine the foundation-level earthquake record. Nonlinear static pushover analysis was carried out via SAP2000 and STA4CAD, utilizing site response analysis and test results taken from the reinforcement and concrete samples of the building. The findings, compared with the observed damage, provide insights into the performance of older RC buildings in this region.

This paper investigates how accounting for contact conditions and a step abutment in the foundation affects the seismic damage behaviour of concrete gravity dams. For this purpose, a pushover analysis was conducted utilising two distinct calculation models based on continuum damage mechanics. The first model uses a continuous mesh between the dam and the soil foundation without modelling any discrete interfaces, while the second considers the dam and soil meshes separately with contact relations. To improve accuracy, the numerical simulations were conducted for each case with three different damage models. The results indicate how considering contact conditions has a significant impact not only on the overall seismic response but also on the distribution and progression of the damage field in the dam. More precisely, the areas where damage occurs in the vicinity of the foundation zones differ between these two models. The first model results indicate damage first appearing near the heel, while with the second model the damage begins near the abutment. This is demonstrated using the Beni-Haroun gravity dam as a structural case study.

The behavior of center columns in shallow-buried underground subway station structures resembles that of high-rise buildings. In both cases, these columns experience significant vertical loads during earthquake events and are susceptible to brittle failure due to inadequate deformation capacity. In this study, the design concept of split columns, commonly employed in high-rise structures, is adapted for application in a two-story, two-span subway station. Initially, a comparative analysis was conducted using quasi-static pushover analysis to assess the horizontal deformation characteristics of traditional and split columns under high axial loads. Subsequently, a comprehensive quasi-static pushover analysis model encompassing the soil-structure interaction was formulated. This model was employed to investigate differences in seismic performance between traditional and innovative underground structures, considering internal forces, deformation capacity, and plastic damage of crucial elements. The analysis results demonstrate that the incorporation of split columns in a two-story, two-span subway station enhances the overall seismic performance of the structure. This enhancement arises from the fact that split columns mitigate excessive shear forces while effectively utilizing their vertical support and horizontal deformation capacities.

Large earthquakes in the last 25 years have caused significant damage to buildings and infrastructure, including the partial or total collapse of storage tanks in various industries. Elephant foot buckling, or local buckling at the base, is one of the main failure modes observed in these structures, and this failure mode can lead to their collapse and/or complete loss of contents. Although hydrostatic and hydrodynamic loads typically affect the seismic response of tanks, the effect of soil type on tank buckling behavior has not been widely studied or recognized. This research aims to evaluate the effect of soil type on seismic fragility of tanks by analyzing typical storage tanks used in the wine industry. The work focuses on elephant foot buckling for tanks with both unanchored and anchored bases and compares the influence of three different types of soil and two different tank geometries. The approach uses the capacity spectrum method, as opposed to the more commonly used incremental dynamic analysis, to determine a critical peak ground acceleration to cause buckling at the tank. The tanks were subjected to 21 Chilean seismic records with three different soil types and a no-soil condition. From the results a lognormal fragility curve, and its median and standard deviation, are calculated. The results indicate that unanchored tanks built softer soils exhibit poorer performance, while tanks in competent soils and rock exhibit good performance. Anchored tanks show less sensitivity to soil types than unanchored tanks. The study demonstrates the importance of considering soil-foundation-structure interaction for wine storage tanks, but the results indicate that many comparable storage structures will be similarly affected.

Reinforced concrete frame buildings are at risk of earthquake. Improving their response by adequate strengthening provision is an issue of major importance. Among the recent techniques introduced to increase the seismic resistance of this type of structure, shape memory alloy materials were found to bepromising. They have largedamping properties and significant re-centering capacity that reduce seismic efforts and limit damage. This work was dedicated to assessing the enhancement of building seismic capacity based on shape memory alloys of different sorts. Reinforcement consists of using rebars made from this material to replace longitudinal steel rebars in the critical zones of beams. A comparison of seismic performance induced by this technique with that associated with the conventional option relying entirely on steel as reinforcement was conducted. This was performed in the case of a medium-rise regular building subjected to medium and strong earthquakes when strengthened using four different shape memory materials including nickel titanium and ferrous-based alloys. SeismoStruct software was used to simulate the building through the static pushover analysis and the nonlinear time-history dynamic analysis. The building was anchored in the soil assumed to be rigid and the inelastic displacement-based beam element was used to discretize the structural members by setting up five integration sections and 150 fibers. In comparison with the steel-based option, it was found in both sites of construction that the use of shape memory yields an improvement in seismic resistance and re-centering performance. By using these smart reinforcements, the residual maximum inter-story displacement was reduced to less than a quarter of its value associated with the steel-based reinforcement. Furthermore, ferrous-based shape memory alloys were identified to yield a cost-effective strengthening alternative with regards to the common nickel titanium option and less than 10% of relative variation was observed in comparison with this latter.