Search Results (490)

Vertical prestressing is critical for shear resistance in long-span PC continuous rigid-frame bridges, yet existing design methods rely on the inaccurate superposition of single-tendon stress fields, neglecting mechanical interaction between adjacent tendons. This study derives the first closed-form elastic analytical solution for the vertical normal stress field under two interacting prestressing tendons, explicitly capturing the coupling term. Validated against high-fidelity Finite Element Analysis (FEA), the solution achieves a Mean Absolute Percentage Error (MAPE) below 6.8%, outperforming conventional superposition methods by 6.8–17.7 percentage points. The analysis reveals a transition from diffusion-dominated to superposition-dominated stress regimes and establishes a predictive linear relationship between tendon spacing and the depth of the prestressing blind zone. The section at one-fourth of the web height below the top edge is identified as the critical control section, leading to a proposed maximum spacing limit of 0.34 times the web height to ensure a stress uniformity coefficient greater than 0.95. This criterion represents a 13.3% increase over empirical rules and a 27.5% increase over the JTG 3362-2018 limit, enabling estimated savings of 52,000 CNY per typical four-span bridge while maintaining structural safety. This represents a 13.3% increase over empirical rules and a 27.5% increase over the limit in JTG 3362-2018, enabling estimated savings of 52,000 CNY per typical four-span bridge while maintaining structural safety. Full article

The research presented in this work focuses on the structural optimization of a multilayer CFRP (carbon fiber reinforced polymer) laminate integrated within a railway carbody frame. The primary objective is to implement a systematic design methodology aimed at achieving significant mass reduction while preserving the mechanical performance and safety margins required by railway standards. To this end, a multi-stage optimization framework was developed to explore the sensitivity of fiber orientation on the laminate’s failure behavior, directly coupled with high-fidelity finite element models for objective performance extraction. The investigation was initially conducted using an asynchronous optimization strategy, where the orientation of each individual ply was decoupled and analyzed independently. This phase revealed that a tailored, ply-specific approach is essential to address the varying structural requirements across the laminate thickness. Through this methodology, an optimal sequence of 36°/54°/126° was identified, achieving a significant 40.83% reduction in the Tsai–Wu failure index compared to a standard 0°/0°/0° baseline. Subsequently, a synchronous rotation analysis was performed to compare these results against conventional single-orientation design strategies. While the synchronous optimum was identified at 54°, it yielded a lower failure index reduction of 24.81%. The comparison highlights a further 16% performance gain enabled by the asynchronous method. Finally, the validation confirmed that these in-plane improvements were achieved without compromising interlaminar integrity, as the interlaminar shear stress (ILSS) remained constant and safe. This framework provides an objective and rigorous tool for the railway industry, replacing empirical design methods with a high-performance, data-driven approach. Full article

This study presents a probabilistic assessment of seismic loss and recovery for residential buildings in Bucharest, Romania, using the FEMA P-58 framework implemented in SP3. A typology set is developed to represent the building stock, accounting for structural system, construction period, and height. The analysis evaluates scenario-based losses, functional recovery times, and expected annual loss (EAL) across seismic hazard levels representative of Vrancea earthquakes. Results show that frame-based systems are highly sensitive to building height, with the highest losses and longest recovery times in older mid- and high-rise buildings. For pre-1990 construction, masonry-infilled reinforced concrete frames are more representative than bare frames and drive the vulnerability of the older building stock. Reinforced concrete shear wall systems perform better, with lower losses and faster recovery across all categories. Nonstructural damage, especially drift-sensitive components, is a contributor to both repair cost and downtime. The results are interpreted comparatively, highlighting the role of structural system, code era, and height. While absolute values depend on modeling assumptions, the study provides a consistent basis for identifying vulnerable typologies and supporting risk mitigation and resilience planning. Full article

Long-period ground motions (LPGMs), rich in low-frequency content, can resonate with long-period structures like high-rise buildings, leading to severe damage. As seismic design shifts from safety toward resilience, limited attention to LPGMs makes it difficult to ensure the seismic resilience of long-period structures. This study used Perform-3D software to model three high-rise reinforced concrete (RC) frame–shear wall structures with varying periods and one with infill walls for resilience assessment. The resilience indicators and seismic resilience grades under LPGMs and ordinary ground motions (OGMs) were compared using the Standard for Seismic Resilience Assessment of Buildings (GB/T38591-2020) and the Guideline for Evaluation of Seismic Resilience Assessment of Urban Engineering Systems (RISN-TG041-2022), which are national standards in China. The results show that the structural response under LPGMs is significantly different from that under OGMs. In particular, the influence of LPGMs on displacement-sensitive non-structural components is much greater than OGMs. Resilience indicators were higher under LPGMs. The presence of infill walls notably reduced resilience indicators, with a stronger effect under OGMs. Based on GB/T38591-2020, the seismic resilience of each structure generally decreases by 1–2 grades under LPGMs, while evaluations based on RISN-TG041-2022 show similar ratings under both LPGMs and OGMs. Full article

High-frame-rate (HFR) ultrasound imaging enables the acquisition of up to several thousand frames per second, substantially improving the temporal resolution of echocardiography. This technical advancement allows visualization of rapid mechanical and hemodynamic events that are not captured by conventional systems. In this review, we summarize the methods used to achieve HFR acquisition and examine their application across three principal domains: deformation imaging, mechanical wave imaging, and blood flow imaging. In deformation imaging, clinical studies have demonstrated higher feasibility for myocardial motion tracking and more reliable temporal deformation parameters. Mechanical wave imaging has emerged as a complementary domain, using HFR acquisition to capture transient mechanical events and estimate regional myocardial stiffness under both physiological and pathological conditions. In flow imaging, improved temporal resolution enables detailed visualization of rapid intracardiac flow and the evaluation of complex hemodynamic patterns. This technology expands the scope of functional and quantitative cardiac assessment and is emerging as a valuable modality for noninvasive diagnosis and monitoring in cardiovascular disorders. Full article

The steel frame-shear wall composite system has excellent lateral resistance performance in prefabricated steel structure buildings. However, the traditional steel plate concrete shear wall is prone to early buckling of the steel plate and concentrated interface damage under cyclic loading, which limits its energy dissipation capacity. This study presents a steel plate-enhanced reinforced concrete shear wall (SPRCSW) with an internal corrugated steel plate and double-layer steel mesh working together and conducts a selection study based on finite element analysis. Under the same design conditions, the peak bearing capacity in the positive and reverse directions of the SPRCSW is increased by approximately 55.4% and 46.9%, respectively, compared to the ordinary reinforced concrete shear wall, with a ductility coefficient reaching 6.08. The stiffness decline is mild, and the hysteretic curve is complete. Then, this paper forms an SR-SPRCSW composite structural system by combining the new shear wall with a steel frame using semi-rigid joints. Through the comparison of the finite element analysis and low-cycle reverse loading test results of the SR-SPRCSW structure, it is verified that the overall structural system shows good agreement in hysteretic response, skeleton curve characteristics, and failure mode under both research methods, with the peak shear bearing capacity error of less than 1% and the overall bearing capacity deviation controlled within 8%. On this basis, the key parameters of the semi-rigid joints in the SR-SPRCSW structure are analyzed. The results show that the strengthening of the “top and bottom + double web” angle steel joint can raise the peak bearing capacity of the SR-SPRCSW structure by approximately 26.1% and the yield displacement by approximately 29.5%; increasing the strength grade and diameter of high-strength bolts can heighten the initial stiffness and bearing capacity of the overall structure, but ductility slightly decreases; the thickness of the angle steel has a significant impact on the stiffness and deformation capacity of the structure, and a recommended range of values with better comprehensive performance is provided. The findings offer valuable insights for designing seismic-resistant semi-rigid steel frames with steel plate reinforced concrete shear walls and optimizing their parameters. Full article

This paper presents a theoretical study on the seismic behavior and working mechanisms of eccentrically braced composite frames with vertical shear links. A theoretical model is established based on structural mechanics principles to analyze the internal force distribution and deformation patterns under lateral loading. Formulas for the lateral stiffness, bending moments in beams and columns, and joint rotations are derived. A multi-stage theoretical skeleton curve model is proposed, identifying key points such as cracking, yielding, peak strength, and failure, along with corresponding methods for calculating load and displacement values. The theoretical results show good agreement with experimental data, effectively predicting the structural stiffness, load-bearing capacity, and deformation behavior. Key design parameters affecting structural performance are identified, including the beam–column linear stiffness ratio, geometric properties of the shear link, and brace stiffness. The study provides a theoretical basis and practical methodology for the seismic design of such structures. Full article

Standard compatibility-based truss models, including the Disturbed Stress Field Model (DSFM), often underestimate the shear strength and deformation capacity of reinforced-concrete (RC) beam-column joints. This study investigates the origin of this bias through a systematic inverse identification framework and derives joint-core constitutive relationships tailored to the highly confined, nonuniform stress states of joints. Inverse analyses show that improving confinement effectiveness alone leads to unrealistic parameter saturation and cannot reproduce the measured energy absorption, indicating that conventional compression-softening formulations remain excessively punitive for joint cores. When confinement activation and softening are identified simultaneously, a clear mechanism shift emerges: unlike panel-based theories that link softening to tensile-cracking measures (principal strain ratio), joint softening is overwhelmingly governed by the principal compressive strain, consistent with crushing-dominated damage accumulation. Based on these trends, unified power-law expressions are proposed for both passive confinement activation and damage-induced softening as functions of principal compressive strain only, adhering to a parsimonious formulation without auxiliary variables such as concrete strength or reinforcement ratio ($R^2\approx 0.89$). The model is validated on an independent database of 113 specimens, including high-strength concrete and exterior joints, eliminating the systematic conservatism of the standard DSFM and improving the mean experimental-to-predicted strength ratio from 0.85 to 1.01 while reducing the coefficient of variation from 34.5% to 13%. The proposed formulation supports more reliable joint shear backbone predictions for seismic assessment of RC frame buildings. Full article

Limitations of the cone penetration test, especially to accurately determine undrained shear strength (S_u) in soft soil deposits with high in situ stresses, have motivated the development of alternative devices, such as the T-bar and ball penetration tests, commonly referred to as flow penetrometers. These devices can estimate, in a single test, both the undrained shear strength (S_u) and the remolded strength (S_ur). When equipped with pore pressure sensors, they also provide valuable information on soil stratigraphy and consolidation parameters, making them versatile tools for characterizing soft soils. This study presents the development of two flow penetrometers, piezoball and piezo-T, highlighting relevant aspects of their design and calibration, followed by experimental campaigns conducted in two Brazilian clay deposits (Tubarão/SC and Sarapuí/RJ). Field tests enabled a direct comparison between the flow penetrometers and conventional methods, both in terms of S_u and S_ur. The investigation also examined the coefficient of consolidation of the soft soils. The results demonstrate good repeatability and consistent values for the bearing capacity factors (N_b and N_t) and remolded behavior (N_b-rem and N_t-rem). Regarding the performance of the pore pressure transducers, the piezoball test demonstrated good performance in pore pressure measurements and derived coefficients of consolidation. In contrast, despite the proposed design modifications, the piezo-T exhibited instability in the readings. Although the findings are derived from specific sites, the discussion is framed in light of the ranges reported internationally, highlighting potential local implications and reinforcing the need to expand robust geotechnical databases to support future applications. Full article

Nonlinear seismic analysis procedures can accurately estimate structural responses but are computationally intensive, making them impractical for engineering design. This study provides the first comprehensive evaluation of N2 and modal pushover analysis for eccentrically braced frames (EBFs), revealing their strengths and limitations in predicting link rotations, shear demands, and drift distribution under Canadian seismic hazards. Analyzed were four-, eight-, and 14-storey chevron EBFs under real and artificial ground motions compatible with the response spectrum of Vancouver, Canada. The findings indicate that inelastic link rotations for all EBFs remain below the design limit of 0.08 rad, except for the upper two floors of the 14-storey EBFs. Seismic analysis reveals that maximum inelastic link shear forces often exceed design recommendations. It is also observed that both the N2 method and MPA procedure could reasonably predict the peak roof displacements for low-rise EBF buildings. In addition, while the MPA procedure provides better predictions of maximum inter-storey drifts over all storeys for medium-to-taller EBFs, inter-storey drifts are not predicted well in the N2 method. Additionally, the current code formula for estimating the fundamental period of EBFs predicts shorter periods than those obtained from analysis. An improved formula for estimating EBF periods is proposed. Full article

This paper introduces an enhanced beam formulation for predicting the natural frequencies of thin-walled composite beam-type structures under initial loading. Each wall of the cross-section is idealized as a thin, symmetric, and balanced angle-ply laminate. The formulation is based on Hooke’s law and a geometrically nonlinear framework, taking into account restrained warping and large-rotation effects, respectively. Shear deformation effects are incorporated by applying the Timoshenko–Ehrenfest beam theory for bending and a modified Vlasov theory for nonuniform torsion. Coupling between transverse shear forces and warping-induced torsional moments arising from cross-sectional asymmetry is explicitly included. A consistent mass matrix, accounting for coupling between translational, rotational, and warping degrees of freedom, is derived using a kinetic-energy-based approach for the thin-walled beam element. Within the framework of Hamilton’s variational principle, the governing equations of the structure in global coordinates are formulated, and the associated eigenvalue problem is derived. The proposed formulation is validated through selected benchmark examples, demonstrating its effectiveness in predicting the natural frequencies of geometrically nonlinear, shear-deformable thin-walled beam and frame structures under initial loading. Full article

Protein-based parenteral drug products processed in a filling line can be exposed to shear stress of varying magnitude depending on the operation. These shear stresses and other factors, such as interfacial stress, have been the focus of many studies in recent years on the cause of product degradation. Estimating shear stress in individual operating units represents the first step towards a more in-depth study of the shear-induced product instability. In this frame, the present manuscript shows an innovative workflow to obtain a computational model of a peristaltic pump and evaluate the exposure of the product to shear stresses. This was accomplished through Computational Fluid Dynamics simulations combined with Lagrangian Particle Tracking techniques. In this way, the shear stress history of each individual product particle passing through the peristaltic pump was taken into account. The results provide insight into shear stress dynamics within a peristaltic pump and show potential for future applications. Full article

Profile conveyor belts are used in operational applications where the transport of bulk materials is required at high inclinations on conveyor belts, typically in the range of 30–40°. This paper deals with the analytical determination of the critical angle of inclination of a homogeneous transverse profile (protrusion), beyond which relative movement of bulk material occurs on the surface of the conveyor belt. The compressive forces induced by the known gravity component of the bulk material acting on a 20 mm high transverse protrusion were experimentally measured on a specially designed laboratory apparatus. The measurements were performed at different inclination angles of the folding plate, which simulated the working surface of the conveyor belt. During the experiments, the investigated bulk material—river gravel with a grain size of 4 ÷ 8 mm—was placed in a plastic frame with a width corresponding to the defined loading width of the conveyor belt. On the basis of the measured values of compressive forces, the static coefficient of shear friction in contact with grains of bulk material with two types of surfaces, namely plastic and rubber, was analytically determined. From the experimental data, the mean values of the static shear friction coefficient were determined, which were 0.33 for the plastic surface and 0.48 for the rubber surface, with the orientation of the protrusion perpendicular (90 deg) to the longitudinal axis of the conveyor belt. The experimental investigation also included the determination of the internal friction angle of the river gravel. The results show that when bulk material is conveyed by a profile conveyor belt, it is possible to safely convey material with a cross-sectional height greater than the height of the transverse protrusion, provided that the conveyor inclination angle does not exceed the internal friction angle of the bulk material. Full article

The use of a corrugated steel plate shear wall (CSPSW) lateral load-bearing system in a steel moment frame (SMF) significantly increases the system’s energy absorption and stiffness. However, the design of CSPSWs involves many parameters and details that greatly increase the complexity of the structure’s response. This study aims to evaluate the effectiveness of the geometric parameters of this system using modern optimization algorithms and an alternative mathematical technique, Response Surface Methodology (RSM). Five geometric parameters, namely crest width (a), diagonal section width (b), corrugation depth (c), sheet thickness (t), and aspect ratio of plate dimension (d), were analyzed to improve the performance of CSPSWs. Design of experiments (DOE) was performed using Design-Expert software, and the required response surface methodology models were designed based on the dimensions of the five variables. Structure weight per meter reduction was set as the optimization goal of the problem. The problem constraints were also defined based on an increase in load-bearing capacity and a reduction in the equivalent plastic strain (PEEQ) percentage in three safety levels 80%, 85% and 90%. Subsequently, the alternative equations developed by RSM to define the objective function and nonlinear constraints were also optimized using modern algorithms in MATLAB 2015. Results revealed a coefficient of determination (R²) of 0.9995 between the experimental and numerical findings and a 1% error between the values obtained from the optimization and reanalysis of the finite elements. Also, they showed an increase in the frame’s lateral load-bearing capacity with the CSPSW, along with a reduction in weight. Full article

Earthen materials are attractive sustainable building solutions due to their low embodied energy and ecological benefits. However, their inherent weaknesses, such as low strength and poor durability, severely restrict modern engineering applications. Traditional physical or chemical modification methods struggle to balance significant improvement in mechanical performance with the preservation of their core sustainable attributes. To overcome this long-standing challenge, this study proposes a paradigm-shifting solution: a prefabricated monolithic lattice–earth composite wall structure. This system abandons the single-material-centered modification approach. Instead, through macroscopic system-level composite design, reinforced concrete lattices and earthen blocks are prefabricated into integral wall panels in a factory. These panels then work collaboratively with the peripheral frame through reliable integral connections. Via quasi-static tests and theoretical analysis on four scaled wall specimens with different design parameters, this study systematically reveals the working mechanism and performance regulation principles of this composite system. The core findings indicate: (1) The system achieves multiple seismic defense lines and a controllable energy dissipation path through a sequential damage mechanism: “earthen material cracking and friction → lattice yielding and energy dissipation → final defense by the frame.” (2) The ratio of the equivalent lateral stiffness of the prefabricated wall panel to the stiffness of the outer frame is a key dimensionless design parameter controlling the failure mode (ductile shear or brittle bending), and the lattice configuration is an effective means to adjust this parameter. (3) Based on tests and an equivalent stiffness model, quantitative design guidelines are proposed, focusing on optimizing lattice density (recommended: 3–4 lattice columns), limiting the aspect ratio (preferably ≤1.5), and ensuring “strong connections.” This study demonstrates that the system, without sacrificing the intrinsic sustainable advantages of earthen materials, successfully endows them with high performance, meeting modern seismic code requirements and potential for prefabricated construction through system integration innovation. It provides a new path with theoretical foundation and practical feasibility to resolve the core contradiction in the modernization of traditional earthen buildings—the incompatibility between ecological attributes and engineering performance. This lays an important foundation for developing next-generation high-performance green building structural systems. Full article