This paper focuses on the stability issues of geological and engineering structures and conducts research from two perspectives: the mechanism of slope landslides under micro-seismic action and the cyclic failure behavior of concrete materials. In terms of slope stability, through the combination of model tests and theories, the cumulative effect of circulating micro-seismic waves on the internal damage of slopes was revealed. This research finds that the coupling of micro-vibration stress and static stress significantly intensifies the stress concentration on the slope, promotes the development of potential sliding surfaces and the extension of joints, and provides a scientific basis for the prediction of landslide disasters. This helps protect mountain ecosystems and reduce soil erosion and vegetation destruction. The number of cyclic loads has a power function attenuation relationship with the compressive strength of concrete. After 1200 cycles, the strength drops to 20.5 MPa (loss rate 48.8%), and the number of cracks increases from 2.7 per mm(3) to 34.7 per mm(3) (an increase of 11.8 times). Damage evolution is divided into three stages: linear growth, accelerated expansion, and critical failure. The influence of load amplitude on the number of cracks shows a threshold effect. A high amplitude (>0.5 g) significantly stimulates the propagation of intergranular cracks in the mortar matrix, and the proportion of intergranular cracks increases from 12% to 65%. Grey correlation analysis shows that the number of cycles dominates the strength attenuation (correlation degree 0.87), and the load amplitude regulates the crack initiation efficiency more significantly (correlation degree 0.91). These research results can optimize the design of concrete structures, enhance the durability of the project, and indirectly reduce the resource consumption and environmental burden caused by structural damage. Both studies are supported by numerical simulation and experimental verification, providing theoretical support for disaster prevention and control and sustainable engineering practices and contributing to ecological environment risk management and the development of green building materials.

Steel and reinforced concrete buildings are popular structural systems. The design of these buildings is regulated by deterministic building codes. In this context, it is established that if building codes are followed, the structure will resist demands without collapsing. However, no regulation is required to control the damage of structures in terms of performance criteria. In this paper, the seismic performance and structural reliability of both steel and reinforced concrete buildings, respectively, are analyzed as a benchmark case of study. Both buildings are designed in an earthquake-prone area for two soil types, respectively. Subsequently, nonlinear dynamic analyzes are conducted and the seismic responses of the models are determined in terms of inter-story drift. To obtain seismic responses, eleven characteristic ground motions of the region are selected corresponding to three performance levels: (1) immediate occupancy, (2) life safety, and (3) collapse prevention, respectively. It was documented that the resulting maximum inter-story drift was much lower than the one obtained from modal analysis. In addition, the risk was computed in terms of reliability index integrating a novel probabilistic approach with performance-based design criteria. According to the results, a small variation in the structural risk among the buildings under consideration is observed. However, buildings designed for rigid soil proved to be more reliable. Additionally, it is observed that the buildings designed with current regulations are too conservative based on the performance criteria limits. Hence, structures located on earthquake-prone areas may be overdesigned when implementing deterministic building codes.

The underground concrete silo, designed as a hollow cylinder with a large aspect ratio and thin walls, is highly susceptible to failure caused by intentional or accidental soil explosions. To enhance its protection, this study investigates the dynamic tensile responses and failure mechanisms of underground concrete silos subjected to high-yield soil explosions. The concept of nominal crack width is proposed to quantitatively describe the degree of overall bending-induced tensile responses and failure of the concrete silo. The influences of explosive weights, standoff distances, and the aspect ratios and thicknesses of the underground concrete silo are quantitatively explored first. On this basis, a dimensionless number combining these major influencing factors is derived using dimensional analysis. The derived dimensionless number has a clear physical meaning, reflecting three aspects: the inertia of the blast loading, the resistance ability of concrete material to bending responses and failure, and the resistance ability of silo structure to bending responses and failure. The results demonstrate that the proposed dimensionless number effectively correlates with the overall bending-induced tensile responses and failure of silo structures across various geometries and explosion scenarios, exhibiting a good linear relation with the dimensionless nominal crack width of the concrete silo. With its solid physical foundation, the dimensionless number offers practical applications in scaling analysis and fast damage assessment. Specific examples of these applications are presented and discussed in this study.

After two major earthquakes centred in Kahramanmara & scedil; on February 6, 2023, in T & uuml;rkiye, there was significant destruction of the building stock. More than fifty thousand people lost their lives, and many people lost their comfort of life even though they were rescued from the wreckage. Researchers have emphasized that this catastrophic consequence is generally caused by design and production errors and low material quality in almost all building types, especially reinforced concrete, steel, masonry, and prefabricated structures. Within the scope of this study, damage patterns and the design flaws of reinforced concrete structures in Malatya, which is one of the provinces affected by the Kahramanmara & scedil; earthquakes, were examined via a field study. During the fieldwork, it was determined that inadequate longitudinal reinforcement and stirrup reinforcement, in-depth reinforcement, and concrete quality, design errors in the column-beam junction area, ignoring the structure-soil interactions, short columns, torsional irregularity, and soft stories were the main factors that led reinforced concrete buildings to be heavily damaged or collapse. After the root causes of damage to reinforced concrete structures were examined, the measures and applications that should be taken to ensure that reinforced concrete structures can maintain their services in the event of earthquakes that are likely to occur in the future was discussed.

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.

The conventional similarity theory derived from dimensional analysis struggles with the well-known issue of non-scalability of material strain-rate effects between scaled models and prototypes. This limitation has significantly hindered the application of scaled model tests, particularly small-scale centrifugal model tests, in the study of structures against blast loading. To overcome this challenge, this study proposes a rate-dependent similarity theory for scaling the dynamic tensile responses and failure of large-scale underground concrete silos (46 m in height) subjected to large-yield soil explosions. The proposed theory includes a correction method derived from a verified dimensionless number, Dcs, which accurately reflects the overall bending-induced tensile response and failure mechanism of concrete silos. The correction strategy involves maintaining an equal Dcs between the scaled model and the prototype by adjusting the explosive weight and the concrete's static tensile strength in the scaled model to account for differences in strain-rate effects. To verify the theory, a series of geometrically similar silo models with scaling factors beta = 1, 1/2, 1/5, 1/10, 1/20, 1/50, and 1/100 were designed. High-fidelity numerical simulations were performed using a fully coupled numerical model encompassing the explosive-soil-silo system. The results demonstrate that, with the conventional dimensional analysisbased similarity theory, the tensile damage and failure of the scaled silo models differ significantly from those of the prototype. However, with the proposed rate-dependent similarity theory, the failure patterns of the silo models with beta = 1 similar to 1/100 are almost identical, indicating that the proposed theory can effectively address the troublesome issue of dissimilar material strain-rate effects between scaled models and prototypes. This similarity theory offers a solid theoretical foundation for designing scaled models that accurately reflect prototype behavior, thereby advancing the application of scaled model tests in the study of structures against blast loading.

This study evaluates the earthquake-induced movement of geogrid earth-retaining (GER) walls. A thorough investigation was conducted on a GER wall model, utilizing a comprehensive finite element (FE) analysis. This research focuses on investigating and designing hollow prefabricated concrete panels and conventional gravitytype stone masonry GER walls. It also displays comparative studies such as the displacement of the wall, deflection of the wall, lateral pressure of the wall, settlement of the backfill reinforcement, vertical pressure of the backfill, lateral pressure of the backfill, vertical settlement of the foundation, and settlements of soil layers across the height and acceleration of the walls of the GER walls. The FE simulations used a three-dimensional (3D) nonlinear dynamic FE model of full-scale GER walls. The seismic performance of models has also been examined in terms of wall height. It was found that the seismic motion significantly impacts the height of the GER walls. In addition, the validity of the proposed study model was assessed by comparing it to the conventional reinforcement concrete and gravity-type GRE wall and ASSHTO guidelines using finite element (FE) simulation results. Based on the findings, the hollow prefabricated concrete panels were the most practical alternative due to their lower deflection and displacement. Based on the observation, it was also found that the hollow prefabricated GER wall is the most viable option, as the settlement and lateral pressure in the former type are high.

Contemporary reinforced concrete structures suffer from the drawback of developing micro-cracks during their service due to causes related to shrinkage and fatigue. This may compromise their technical and functional serviceability due to the possible reduction in durability which may lead to a decrease in load carrying capacity of the structure. In recent years, experimental studies on biomineralization or biocementation have shown a potential to address this issue. Biocementation is the process in which microorganisms induce the production of calcium carbonate which can improve self-healing capabilities by filling the micro-cracks and pores in the structures, similar to the traditional lime-based materials. The most used pathway of biocementation is urea hydrolysis, which is brought about by the urease enzyme secreted by ureolytic bacteria. Although there have been numerous laboratory-scale studies that have yielded positive results, the widespread adoption of this technology in practical applications is still hindered by a range of constraints. The information about the solutions to resolve these limitations is fragmented and dispersed throughout the literature. This review aims to compile state-of-the-art knowledge in one place. This article provides a detailed assessment of the challenges in the application of biocementation and suggests strategies to overcome the obstacles that hinder its use in construction projects.