Search Results (3,742)

The seismic vulnerability of existing reinforced concrete (RC) buildings that constitute a large portion of the urban building stock has become a growing concern for urban safety. This situation was once again revealed by the massive destruction that occurred in RC structures following the 2023 Kahramanmaraş earthquakes. Particularly in buildings constructed before 1990 and without adequate engineering services, destruction and damage were much greater. In this paper, structural models were created with inadequate transverse reinforcement, low-strength concrete, and inadequate concrete cover thickness, which all play a critical role in the seismic performance of the buildings. Structural analyses were updated for high-performance concrete jacketing models, considering the deformation status obtained for each inadequate parameter. It has been determined that the high-performance concrete can significantly increase structural performance, especially significant increases in shear strength capacities without the need for transverse reinforcement. Full article

To accurately assess the seismic risk of bridges, this study systematically conducted probabilistic seismic hazard–fragility–risk assessments using a reinforced concrete continuous girder bridge as a case study. First, the CPSHA method from China’s fifth-generation seismic zoning framework was employed to calculate the Peak Ground Acceleration (PGA) with 2%, 10%, and 63% exceedance probabilities over 50 years as 171.16 gal, 98.10 gal, and 28.61 gal, respectively, classifying the site as being with 0.10 g zone (basic intensity VII). Second, by innovatively integrating the Response Surface Method with Monte Carlo simulation, the study efficiently quantified the coupled effects of structural parameter and ground motion uncertainties, a finite element model was established based on OpenSees, and the seismic fragility curves were plotted. Finally, the risk probability of seismic damage was calculated based on the seismic hazard curve method. The results demonstrate that the study area encompasses 46 potential seismic sources according to China’s fifth-generation zoning. The seismic fragility curves clearly show that side piers and their bearings are generally more susceptible to damage than middle piers and their bearings. Over 50 years, the pier risk probabilities for the intact, slight, moderate, severe damage, and collapse are 68.90%, 6.22%, 15.75%, 7.86%, and 1.27%, while the corresponding probabilities of bearing are 3.54%, 44.11%, 25.64%, 7.74%, and 18.97%, indicating significantly higher bearing risks at the moderate damage and collapse levels. The method proposed in this study is applicable to various types of bridges and has high promotion and application value. Full article

In regions where seismic loads pose a significant danger to the structural stability of buildings, developing sustainable solutions for increasing the ductility of structural members is of great importance. One of the contemporary, emerging approaches is to use the greater confinement of concrete using multispiral reinforcement. A numerical model of two variants of Multispiral-Reinforced Concrete Columns (MRCCs) that differ in their axial loads using FEA was developed and validated. A non-linear combined fracture-plasticity concrete model with the crack band approach and an embedded reinforced model with bond slip were used. The main finding is that higher axial loads do not significantly increase the stiffness response, but reduce ductility (achieved drift). The achieved force agreement between the simulation and the experiment is within $2\%$ at the peak and within $24\%$ at the largest column drift in the post-peak region. For the purpose of rapid prototyping, a plugin that enables the user to quickly change various properties of MRCC geometry using an automated approach instead of modeling individual variants from zero is proposed. This overall approach was developed to both save on user time spent modeling and on the great costs that involve manufacturing and testing of real-scale specimens. Full article

Autoclaved lightweight concrete (ALC) exhibits considerable potential as a wall material in prefabricated structures, but its high water absorption and limited mechanical properties limit its widespread application. Ultra-high-performance concrete (UHPC), which possesses superior mechanical strength and durability, presents a promising reinforcement strategy. This study proposes the development of a UHPC-ALC composite wall material to enhance structural performance. The effects of shrinkage-reducing agent (SRA) content and expansive agent (EA) dosage on UHPC properties were systematically investigated. Results indicate that increasing SRA content improves the fluidity of UHPC and significantly reduces early autogenous shrinkage while the optimal EA dosage enhances both its mechanical properties and volume stability. Furthermore, an interfacial agent was employed to enhance the bonding performance between UHPC and ALC resulting in an average bonding strength of 0.93 MPa which represents a 675% increase compared with the untreated group. Finite element simulations and mechanical tests revealed that the composite material demonstrates a compressive strength of 11.2 MPa and a flexural strength of 6.8 MPa which corresponds to increases of 111.3% and 325%, respectively, relative to monolithic ALC. The composite demonstrated ductile failure and the experimental damage modes were consistent with those of the simulation results. This study offers guidance for optimizing UHPC-based composite wall materials via the multi-scale regulation of shrinkage behavior, interfacial properties, and structural design. Full article

Modern engineering increasingly operates within socio-technical networks, such as the interdependence of energy grids, transport systems, and building codes, where decisions must be reliable and transparent. Large language models (LLMs) such as GPT promise efficiency by interpreting domain-specific queries and generating outputs, yet their predictive nature can introduce biases or fabricated values—risks that are unacceptable in structural engineering, where safety and compliance are paramount. This work presents a dataset that embeds generative AI into validated computational workflows through the Model Context Protocol (MCP). MCP enables API-based integration between ChatGPT (GPT-4o) and numerical solvers by converting natural-language prompts into structured solver commands. This creates context-aware exchanges—for example, transforming a query on seismic drift limits into an OpenSees analysis—whose results are benchmarked against manually generated ETABS models. This architecture ensures traceability, reproducibility, and alignment with seismic design standards. The dataset contains prompts, GPT outputs, solver-based analyses, and comparative error metrics for four reinforced concrete frame models designed under Ecuadorian (NEC-15) and U.S. (ASCE 7-22) codes. The end-to-end runtime for these scenarios, including LLM prompting, MCP orchestration, and solver execution, ranged between 6 and 12 s, demonstrating feasibility for design and verification workflows. Beyond providing records, the dataset establishes a reproducible methodology for integrating LLMs into engineering practice, with three goals: enabling independent verification, fostering collaboration across AI and civil engineering, and setting benchmarks for responsible AI use in high-stakes domains. Full article

Mixed structures with lightweight steel added stories are particularly vulnerable to damage and failure at the joints during seismic events. To evaluate the secondary seismic behavior of the joints in lightweight steel added stories after seismic damage repair, a low-cycle load test was conducted in this study. Following the initial damage, carbon fiber-reinforced polymer (CFRP) was applied for reinforcement, along with epoxy resin for the repair of concrete cracks. The experimental analysis focused on the structural deformation, failure characteristics, and energy dissipation capacity in both the original and repaired joint states. On the basis of the experimental findings, finite element analysis was carried out to examine the influence of varying CFRP layer configurations on the seismic performance of the repaired joints. The results revealed a significant change in the damage pattern of the repaired specimen, shifting from secondary surface damage to significant concrete deterioration localized at the bottom of the column. The failure mechanism was characterized by the CFRP-induced tensile forces acting on the concrete at the column base, following considerable deformation at the beam’s end. When compared to the original joint, the repaired joints exhibited markedly improved performance, with a 33% increase in horizontal ultimate strength and an 85% increase in energy dissipation capacity at failure. Additionally, the rotation angle between the beams and columns was effectively controlled. Joints repaired with two layers of CFRP demonstrated superior performance in contrast to those with a single layer. However, once the repaired joints met the required strength, further increasing the number of CFRP layers had a minimal influence on the mechanical properties of the joints. The proposed CFRP-based seismic retrofit method, which accounts for the strength degradation of concrete in damaged joints due to earthquake-induced damage, has proven to be both feasible and straightforward, offering an easily implementable solution to improve the seismic behavior of structures. Full article

Reinforcement corrosion significantly reduces the load-bearing capacity, ductility, and energy dissipation of reinforced concrete (RC) structures, thereby increasing their seismic failure risk. To enhance the seismic performance of in-service RC structures, this study employs an FRP mesh–engineered cementitious composite (ECC) retrofitting method and develops a multi-objective optimization decision-making framework. A finite element model incorporating reinforcing steel corrosion, concrete deterioration, and bond–slip effects is first established and validated against experimental results. Based on this model, a six-story RC frame is selected as a case study, and eight alternative FRP mesh–ECC retrofitting schemes are designed. Five core indicators are quantified, namely annual collapse probability, expected annual loss, capital expenditure, carbon emissions, and downtime. The results indicate that FRP mesh–ECC retrofitting can significantly improve the seismic performance of corroded RC structures. The overall uniform retrofitting scheme (SCS-2) achieves the most significant improvements in seismic safety and economic performance, but they are associated with highest capital expenditure and carbon emission. Story-differentiated schemes (SCS-3 to SCS-6) provide a trade-off between performance enhancement and cost–emission control. While partial component-focused schemes (SCS-7 and SCS-8) cut cost and carbon but do not lower seismic downtime. Furthermore, the improved fuzzy-TOPSIS method with interval weights and Monte Carlo simulation indicates that the balanced scheme SCS-1 delivers the most robust performance across five dimensions, with a best probability close to 90%. The results confirm the potential of FRP mesh–ECC retrofitting at both component and structural levels and provide a practical reference for selecting seismic retrofitting strategies for existing RC structures. Full article

This study experimentally investigates the strengthening performance and failure behavior of reinforced concrete slabs coated with high elastic modulus polyurea(HEPU). To address the limited strengthening effect of conventional polyurea due to its low elastic modulus and strength, HEPU was applied to slab specimens with varying coating thicknesses (1, 2, and 3 mm). To evaluate the effectiveness of the HEPU reinforcing method, experiments were conducted with varying coating thicknesses, and the results were compared with those of unstrengthened specimens. The results showed that HEPU strengthening significantly enhanced flexural strength and stiffness, with improvements increasing proportionally with coating thickness. Additionally, the polyurea coating enhanced crack resistance and adhered well to the concrete, preventing delamination or detachment up to final failure. The slabs maintained ductile behavior even after HEPU rupture, although load resistance decreased post-rupture. However, the strengthening effect diminished due to the rupture of the HEPU, indicating limited effectiveness in improving ductility. These findings provide insights into the design and application of polyurea-based strengthening techniques for reinforced concrete structures. Full article

This study presents a strut-and-tie modeling (STM) framework for reinforced concrete (RC) deep beams strengthened with intraply hybrid composites (IRCs), integrating comprehensive experimental data from beams with three different span lengths (1.0 m, 1.5 m, and 2.0 m). Although the use of fiber-reinforced polymers (FRPs) for shear strengthening of RC members is well established, limited attention has been given to the development of STM formulations specifically adapted for hybrid composite systems. In this research, three distinct IRC configurations—Aramid–Carbon (AC), Glass–Aramid (GA), and Carbon–Glass (CG)—were applied as U-shaped jackets to RC beams without internal transverse reinforcement and tested under four-point bending. All experimental data were derived from the authors’ previous studies, ensuring methodological consistency and providing a robust empirical basis for model calibration. The proposed modified STM incorporates both the axial stiffness and effective strain capacity of IRCs into the tension tie formulation, while also accounting for the enhanced diagonal strut performance arising from composite confinement effects. Parametric evaluations were conducted to investigate the influence of the span-to-depth ratio (a/d), composite configuration, and failure mode on the internal force distribution and STM topology. Comparisons between the STM-predicted shear capacities and experimental results revealed excellent correlation, particularly for deep beams (a/d = 1.0), where IRCs substantially contributed to the shear transfer mechanism through active tensile engagement and confinement. To the best of the authors’ knowledge, this is the first study to formulate and validate a comprehensive STM specifically designed for RC deep beams strengthened with IRCs. The proposed approach provides a unified analytical framework for predicting shear strength and optimizing the design of composite-strengthened RC structures. Full article

To evaluate the frost resistance of basalt fiber-reinforced concrete (BFRC) and predict its service life, this study conducted 225 quick freeze–thaw (F-T) cycle tests. Specifically, it systematically investigated how basalt fiber (BF) volume content (0.1%, 0.2%, 0.3%) and the incorporation method (single-doped 18 mm, mixed-doped 6 mm/12 mm/18 mm) affect concrete frost resistance. Meanwhile, a two-parameter Weibull distribution model was established to quantitatively predict the service life of BFRC. The results showed that BF significantly improved the frost resistance of concrete: the reference group without BF had a relative dynamic elastic modulus (RDEM) of less than 60% after 25 F-T cycles, while the group with 0.3% volume content of single-doped 18 mm BF still maintained structural integrity after 225 F-T cycles, with a frost resistance grade exceeding F225. Furthermore, within the scope of this study, the frost resistance effect of single-doped 18 mm BF was better than that of mixed-doped BF, and the frost resistance of concrete gradually improved with the increase in BF volume content. In high-altitude cold regions (e.g., Songpan County, Sichuan Province) with 85 annual F-T cycles, the predicted service life of BFRC with 0.3% single-doped BF reached 49 years, which was approximately 25 times that of the reference group (2 years). This study delivers a systematic comparison of the frost resistance between single-doped long and mixed-doped BF, along with a targeted life prediction model for high-altitude cold regions (85 annual F-T cycles, annual temperatures below 6 °C), which collectively offer a theoretical and technical basis for BFRC durability design in freeze–thaw environments. Full article

Reinforced soil retaining walls (RSWs) for railways are key subgrade structures that bear cyclic loads from trains, and their long-term durability directly affects railway operation safety. The mechanical behavior of RSWs under cyclic loading has been extensively investigated in previous studies, primarily focusing on seismic conditions or conventional structural configurations. While these works have established fundamental understanding of load transfer mechanisms and deformation patterns, research on their responses to long-term train-induced vibrations, particularly for concrete-block-panel-wrapped RSWs, an improved structure based on traditional concrete-block-panel RSWs, remains limited. To investigate the dynamic responses of the concrete-block-panel-wrapped RSW, a model test was conducted under cyclic loading conditions where the amplitude was 30 kPa and the frequency was 10 Hz. The model size was 3.0 m in length, 1.0 m in width, and 1.8 m in height, incorporating six layers of geogrid. Each layer of geogrid was 2.0 m in length with a vertical spacing of 0.3 m or 0.15 m. The results indicate that as the number of load cycles increases, deformation, acceleration, static and dynamic stresses, and geogrid strain also increase and gradually stabilize, exhibiting only marginal increments thereafter. The maximum horizontal displacement reaches 0.08% of the wall height (H), with horizontal displacement increasing uniformly along the height of the wall. The vertical acceleration in the non-reinforced soil zone is lower than that in the reinforced soil zone. The horizontal dynamic stress acting on the back of the panel remains minimal and is uniformly distributed along the height of the wall. The maximum geogrid strain was found to be 0.88%, corresponding to a tensile stress amounting to 20.33% of its ultimate tensile strength. The predicted failure surface approximates a bilinear configuration, consisting of one line parallel to the wall face at a distance of 0.3H from the back of the soil bags and another line inclined at an angle equal to the soil’s internal friction angle (φ) relative to the horizontal plane. This study has important reference significance for the application of concrete-block-panel-wrapped RSWs in railways. Full article

The concrete pouring process is difficult to observe inside formwork. With increasingly complex formwork systems and denser reinforcement layouts, honeycomb defects and surface pores are prone to form at beam–column joint core locations. The modeling of pouring processes that were performed earlier is insufficient and there is relatively little research on simulating concrete void defects at typical joints. Therefore, a refined numerical model based on the three-dimensional particle flow method was established to simulate the flow of fresh concrete within formwork and predict concrete voids after pouring. The feasibility of the particle flow method was verified through numerical simulations of slump flow and J-ring tests. Several groups of joint models were set up based on different influencing factors, and the developed particle flow model was used for pouring simulations to investigate the influence of various factors on concrete void formation. The results show that the void volume and distribution patterns obtained from experiments and simulations are basically consistent. The numerical model can accurately simulate the working performance of self-compacting concrete and predict the size and location distribution of pouring defects. Based on both experimental and numerical studies, the following suggestions are proposed to avoid potential void defects in practical concrete pouring projects: reasonably select the number and diameter of joint longitudinal bars; appropriately increase the spacing of column stirrups; appropriately reduce the maximum coarse aggregate particle size; and choose concrete with better fluidity and filling ability. Full article

Joint connections are critical to the overall performance of prefabricated structures. This paper proposes a novel reverse-rotation locking sleeve connection method, designed to ensure the safety of joint engineering while optimizing construction processes, improving operational efficiency, and endowing the joints with excellent seismic energy dissipation performance. To evaluate the performance of this connection method, quasi-static tests under displacement-controlled lateral loading were designed and conducted on three reinforced concrete column specimens (Specimen A: conventional reinforcement–cast-in-place monolithic; Specimen B: conventional reinforcement–reverse-rotation locking sleeve connected; Specimen C: enhanced reinforcement–reverse-rotation locking sleeve connected). The failure modes, hysteretic characteristics, skeleton curves, ductility, energy dissipation capacity, load-bearing capacity, and stiffness degradation patterns of the specimens were systematically examined. The results indicate that Specimen B exhibited the most severe damage extent, while Specimen A demonstrated the best integrity; in contrast, Specimen B showed significant and rapid degradation in energy dissipation capacity during the intermediate-to-late stages of testing; the hysteretic curves of Specimens B and C were full in shape, without obvious yield plateaus; the skeleton curves of all specimens exhibited S-shaped characteristics, and the peak loads of Specimens A and C corresponded to a lateral displacement of 21 mm, while that of Specimen B corresponded to a lateral displacement of 28 mm; compared to the cast-in-place monolithic Specimen A, the reverse-rotation locking sleeve–connected Specimens B and C showed increases in ultimate load under positive cyclic loading by 18.7% and 5.5%, respectively, and under negative cyclic loading by 40.8% and 2.0%, respectively; the ductility coefficients of all three specimens met the code requirement, being greater than 3.0 (Specimen A: 5.13; Specimen B: 3.56; Specimen C: 5.66), with Specimen C exhibiting a 10.3% improvement over Specimen A, indicating that the reverse-rotation locking sleeve–connected specimens possess favorable ductile performance; analysis revealed that the equivalent viscous damping coefficient of Specimen C was approximately 0.06 higher than that of Specimen A, meaning Specimen C had superior energy dissipation capacity compared to Specimen A, confirming that the reverse-rotation locking sleeve connection can effectively absorb seismic energy and enhance the seismic and energy dissipation characteristics of the specimens. The load-bearing capacity degradation coefficients of all specimens fluctuated between 0.83 and 1.01, showing an initial stable phase followed by a gradual declining trend; the stiffness degradation coefficients exhibited rapid initial decline, followed by a deceleration in the attenuation rate, and eventual stabilization. This indicates that the reverse-rotation locking sleeve-connected specimens can maintain relatively stable strength levels and favorable seismic performance during the plastic deformation stage. Full article

Nuclear power plant (NPP) shear walls are typically ultra-thick and heavily reinforced, posing significant challenges for conventional cast-in-place (CIP) construction. To overcome these issues, this study proposes a precast concrete shear wall (PCSW) system with bolted connections. Owing to orthogonal wall layouts dictated by functional requirements, these structures are subjected to significant out-of-plane seismic demands, making their performance under such loading a critical design concern. Therefore, this paper investigates the out-of-plane seismic performance of scaled (1:2) models of PCSWs (300 mm thick) under an axial pressure ratio of 0.2 and without axial pressure through low-cycle repeated load tests, and compares them with corresponding CIP shear walls. All specimens exhibited flexural failure, while damage in PCSWs was relatively minor and concentrated within the grouting layer. Compared with CIP specimens, the precast specimens showed more pinching and smaller residual deformation, with cumulative energy dissipation reaching 70–80% of CIP specimens. The flexural load-bearing capacity of the precast specimens was close to that of the CIP specimens, with differences within 5%. The ductility of the precast specimens under axial pressure ratios of 0 and 0.2 was 4.54 and 2.68, respectively, differing from the CIP specimens by 16% and −10%. The stiffness degradation trends of both systems were essentially consistent. Overall, the results demonstrate that the out-of-plane seismic performance of PCSWs with bolted connections is broadly equivalent to that of CIP counterparts, confirming their feasibility for application in NPPs. Full article

In order to further explore the role of infill walls in the progressive collapse resistance of reinforced concrete (RC) spatial frames, based on ANSYS/LS-DYNA finite element analysis software, the refined numerical models of pure RC spatial frames and infilled RC spatial frames were constructed, respectively. By comparing it with the experimental results, the validity and accuracy of the model are verified. Subsequently, the effects of column removal devices and infill wall openings on the progressive collapse resistance of RC spatial frames were studied. The results show that the residual displacement of the model with a complete column removal device is 238.1% higher than that of the model with an incomplete column removal device, and the stiffness is reduced by 68.8%. The results obtained by an incomplete column removal device are often unsafe. The open-hole infill wall will form a diagonal strut in the corresponding area. The strength of the strut near the fixed end has the most significant effect on the structural stiffness after the column is removed and plays a controlling role. The reduction in the effective area of the strut reduces the strength of the strut and weakens the structural stiffness. When the opening is arranged in the mid-span position, the structural stiffness decreases more significantly. Full article