Over the past decade, ultra-high toughness cementitious composites (UHTCCs) have been extensively investigated due to their superior tensile properties and deformation capacity. The incorporation of UHTCC into engineering structures can significantly enhance their seismic performance. This paper presents a state-of-the-art review of the application of UHTCC in seismic-resisting structures, encompassing composite structures formed with reinforced concrete or steel, as well as applications in the strengthening and repairing of newly constructed or existing structures. The review first introduces the application of UHTCC in flexure-dominated members, such as beams and columns, and their contribution to enhancing structural seismic performance. Subsequently, it discusses the effectiveness of UHTCC in shear-dominated members, including coupling beams, short columns, and shear walls. Following the analysis at the member level, the paper further explores the seismic performance of joints formed by connecting different members, including beam–column, slab–column, column–column, and wall–beam joints. Furthermore, the application of UHTCC in global structural systems is analyzed, covering the behavior of frame structures and coupled shear wall structures under both static and dynamic seismic loading. Meanwhile, the use of UHTCC for the strengthening and repairing of masonry wall-related and reinforced concrete structures is also presented. Finally, this paper proposes potential future research directions for UHTCC in seismic-resisting structures, providing a comprehensive reference for the further development of this field.
Accurate estimation of seismic hazard is a fundamental requirement for achieving resilient and cost-efficient structural design. Traditional Probabilistic Seismic Hazard Analysis (PSHA) typically employs a constant minimum earthquake magnitude mmin for all seismic sources. This simplification can result in either overestimation or underestimation of hazard levels, as it disregards variations in structural performance and source-specific fault characteristics. This paper proposes a Performance-based Probabilistic Seismic Hazard Analysis (PbPSHA) framework in which mmin is determined individually for each fault by incorporating fault-to-site distance, structural performance objectives, and building vulnerability. The proposed methodology incorporates risk components into the hazard assessment and applies an iterative process that couples hazard estimation with damage evaluation until convergence of the mmin is attained. Two numerical examples are presented to demonstrate the methodology. The first example evaluates an existing reinforced-concrete building, determining fault-specific mmin values based on nonlinear dynamic analysis and fragility-based performance criteria. These values are subsequently incorporated into the PbPSHA framework and compared with the results of conventional PSHA employing a constant mmin assumption, revealing notable differences under design-level hazard conditions. The second example applies the iterative PbPSHA approach to a new building design, illustrating its capability to integrate performance objectives into hazard definition during early design stages. Results confirm that PbPSHA provides a more physically meaningful and risk-consistent hazard representation, while also indicating that a simplified approach using the average fault-specific mmin value can serve as a computationally efficient alternative when detailed iteration is not feasible. The proposed methodology enhances the rationality and defensibility of seismic hazard analysis by establishing fault-specific and performance-consistent magnitude thresholds. This approach enhances the reliability of seismic design and risk management, especially for structures with strict performance requirements or those located in regions characterized by diverse seismic sources.
The purpose of this research is to evaluate the effect of using a truss-type skybridge and different design methods on the performance of tall structures. Three design methods were examined, including force-based design, energy-based performance design, and a supplementary configuration using isolators and dampers, which was also examined to illustrate an upper-bound elastic scenario for comparison purposes. The study first analyzed twin 50-story towers, followed by a 50-story and a 40-story tower with a core-braced and outrigger truss system. After initial design, the structures were nonlinearly modeled in PERFORM-3D software and subjected to 28 near-field ground motion records recommended by FEMA P695, and the average responses were finally compared. The results illustrated that the force-based design method could not provide appropriate performance for the skybridge under seismic loads. The energy-based performance method ensured the skybridge met the Life Safety performance level, while the force-based method with isolators and dampers guaranteed elastic behavior of the skybridge. The findings also indicated that both the use of a sky bridge and its design methods significantly affect structural performance. In the twin towers, the average roof displacement decreased by 9.2% when the skybridge was designed using the energy-based performance design method and 7% when designed using the force-based method with isolators and dampers.
This study investigates the impact of progressive cable loss on the seismic performance of cable-stayed bridges using fragility curve analysis under multi-component earthquake excitations. A detailed finite element model of the Bill Emerson Memorial Bridge was developed using OpenSees and validated against existing experimental data. Fragility curves were then generated for scenarios involving the sequential failure of one to four cables under seven selected ground motion records. The fragility analysis focused on the pylons, the most critical structural components of cable-stayed bridges. Following the calculation of the ductility and behavior factor of the pylon, four seismic limit states were defined, and the failure probability of bridge was computed based on the regional seismicity. The results demonstrate that cable-stayed bridges have high seismic capacity and resilience; failure of up to three sequential cables does not significantly increase the probability of total collapse compared to the normal condition. However, the loss of four cables leads to a near-unity failure probability at low intensity levels, indicating a complete loss of structural integrity.
Reinforced concrete (RC) beam-column substructures are the key supports of frame structures, which experiences compressive arch action (CAA) and tensile catenary action (TCA) to resist the progressive collapse. Existing expression models involve complicated inference processes, which struggle with generalized application due to specific simplified assumptions. This paper proposes a new progressive collapse resistance prediction model of RC substructures driven by interpretable hybrid machine learning methods. A high-quality database integrated with 10-dimensional features is established, including CAA and TCA stages during progressive collapse. Three different machine learning models are proposed to conduct a comparison including random forest (RF), least square boosting (LSBoost), and generalized additive models (GAM). Particle swarm optimization (PSO) algorithm is adopted herein to obtain the optimal machine learning model parameters. The Shapley (SHAP) analysis is performed to reveal the prediction process of machine learners involving global interpretable, local interpretable and feature dependence. The results show that PSO-RF model has a better peak prediction accuracy than PSO-LSBoost and PSO-GAM models during CAA and TCA stages. Based on SHAP learning, it is known that the span-to-height ratio and cross-sectional area have significant impacts on the model's prediction results. The proposed PSO-RF model has superior computational accuracy than existing physical models, which provides a key support for the codes revision of RC structures to resist progressive collapse.
Modular steel structures are a typical prefabricated form of assembled construction, and are increasingly recognized as a cornerstone of China's construction industrialization due to their high construction efficiency and environmental sustainability. The mechanical performance of inter-module connections is critical to the overall seismic behavior of a structure. This study proposes a Fully Prefabricated Liftable Connection (FPLC) for modular steel structures. Quasi-static tests were conducted on two full-scale specimens to explore failure mechanisms, hysteresis characteristics, and energy dissipation patterns of FPLC with weakening beam-end. A refined finite element model was developed and validated against experimental results. Twelve parametric models were generated to explore the influence of beam-column sections and bolt configurations on the structural performance of FPLC. The analytical formulas were derived for the initial stiffness and bending capacity, together with a restoring force model. It can be concluded that the enhanced beam section significantly improves load-bearing and energy dissipation capacities with acceptable ductility reductions, while the weakening beam-end increases energy dissipation efficiency. The proposed theoretical formulas can provide guidance for engineering design of FPLC.
Reinforced concrete structures are increasingly vulnerable to deterioration by steel reinforcement corrosion, resulting in severe loss of fracture strength and service life, particularly in severe environmental exposure. Carbon fiber reinforced polymers (CFRPs) are a corrosion-resistant alternative with high-strength performance for construction in seismic and corrosive environments. This work studies the structural behavior of CFRP-reinforced concrete (CRC) frames through numerical simulation and validates them against experimental results. Five full-size CRC frames, with four beams and four columns in a grid arrangement, were loaded monotonically and reversed laterally under constant gravity loads. CFRP bars were used as longitudinal and transverse reinforcement. Parametric analysis was conducted using nonlinear pushover analysis (POA) in SAP2000 (v2014) based on reinforcement area and cross-section member variations. The result shows that CRC frames have sufficient strength, energy dissipation, and deformation capacity, which justifies using CFRP as a long-term alternative to steel in seismically active and corrosive environments. The study's findings confirm the feasibility of designing large-scale ductile structures by driving key structural parameters, such as concrete compressive strength and beam-column rotational stiffness. Additionally, doubling the rotational stiffness caused the ductility ratio to be fourfold. Additionally, enhancing concrete confinement, particularly with lateral confinement stress being four times greater than vertical stress, resulted in a nearly 187% ductility increase under unconfined circumstances. These results emphasize joint stiffness and confinement's crucial role in achieving optimum seismic performance.
Dynamic structure–soil–structure interaction (SSSI) for periodically arranged structure system under incident plane SH wave is investigated using the indirect boundary element method. The solution is presented through response of an infinite number of equally spaced, identical structures (periodically arranged structure system) supported by rigid foundations embedded in a soil layer overlying elastic bedrock. The presented method has the advantages of high accuracy, low computational cost, and low memory requirement. In parametric analysis, whether only immediately adjacent structures contribute significantly to the structural response in dense areas is analyzed first. Numerical results showed that the structural response for periodically arranged structure system may be evidently different from that of a finite array of structures model. While the immediately adjacent structures have the most significant effect, the effect of farther structures is still non-negligible. Then, the effects of separation distance and soil layer are investigated. It is shown that the separation distance may reduce or amplify the structural response compared with that for single structure, which could be as large as 67.5% and 59.7%, respectively, for building relative displacement. The soil layer also has prominent influence. With decreasing soil layer stiffness or soil layer thickness, the building's relative displacement amplitude increases. The conclusions may be useful for prediction of seismic response for design and interpretation of recorded response of full-scale structures in densely built areas.
High-level sports events and performing arts activities are imposing increasingly stringent requirements on the functional facilities of modern gymnasiums, which leads to a growing variety of equipment suspended beneath roof structures, such as center-hung scoreboards, lighting systems, large-sized audio equipment, and elevating stages. These large suspended masses are prone to violent swinging with significant impact effects during strong earthquakes. However, existing literature lacks sufficient research on the seismic response characteristics of long-span roof structures with suspended heavy equipment. This study systematically investigates the natural vibration characteristics, seismic ultimate bearing capacity, and failure modes of a structural system comprising a suspended heavy mass, a single-layer spherical latticed shell, and its lower supporting structure. The results indicate that the length of the suspension cables and the stiffness of the lower supporting structure have some influence on the mode shapes and natural frequencies of the structural system. Increasing the cable length or enhancing the support stiffness both lead to an improvement in the system's ultimate seismic bearing capacity. Notably, for a single-layer spherical reticulated shell suspending large-mass equipment, under unidirectional horizontal seismic wave input, the structure invariably fails due to dynamic strength failure; under three-directional seismic wave input, dynamic instability failure occurs when the suspended equipment is attached to the upper platform, and dynamic strength failure occurs when not attached to the upper platform. The findings of this study provide a reference for the design optimization and safety assessment of long-span roof structures with suspended heavy equipment.
High-performance concrete (HPC) plays a critical role in hydraulic and seismic-prone infrastructure, where both mechanical strength and resilience under earthquake loading are essential. Accurate estimation of uniaxial compressive strength (UCS) is crucial for ensuring structural safety and durability, yet direct testing is often time-consuming, costly, and difficult to integrate into construction workflows. In this study, we propose a novel data-driven framework that combines a Dung Beetle Optimization (DBO)-enhanced LightGBM model with SHapley Additive exPlanations (SHAP) to predict the compressive strength of HPC and elucidate the influence of mix design parameters on structural performance under seismic loads. The proposed framework is validated using real-world datasets from large-scale hydropower projects. Results demonstrate a high predictive accuracy, and SHAP analysis identifies key parameters–cement content, curing age, water-to-cement ratio, and supplementary materials such as blast furnace slag–that significantly influence both strength development and earthquake resilience. The framework provides actionable insights for designing seismic-resilient HPC, optimizing material proportions, and supporting construction decisions under complex environmental onditions.