Search Results (39)

Early-stage dynamic responses of naval structures under underwater explosion shock loads exhibit high-frequency, intense amplitude fluctuations and short durations, serving as critical factors for the development of plastic deformation and other damage characteristics. These structural dynamics demonstrate prominent nonlinear and non-stationary features. This study focuses on the nonlinear evolutionary patterns of early-stage plastic shock responses in underwater explosion-impacted ship structures. Utilizing phase space reconstruction, unimodal mapping, and symbolic dynamics theory, we analyze the nonlinear and non-stationary characteristics along with their evolutionary patterns in experimental data. First, scaled model experiments under varying shock factors were conducted based on a stiffened cylindrical shell prototype, investigating the spatiotemporal evolution of nonlinear and non-stationary dynamic responses under different shock loads while characterizing their uncertainty features. Second, model tests were performed on deck-type cabin structures and plate frameworks derived from a naval vessel’s deck prototype, further analyzing the evolutionary patterns of early-stage plastic dynamic responses and verifying the method’s effectiveness and universality. Research findings indicate that (1) early-stage plastic shock responses of ships under underwater explosions exhibit multiple dynamical behaviors including chaotic motion, periodic motion, and quasi-periodic motion, and (2) during the initial plastic phase, orbital parameters approximate 0.8, providing guidance for test condition setup and initial parameter selection in underwater explosion experiments on naval structures. Full article

Explosions pose significant risks to large-span steel bridges, which are integral to modern transportation networks and construction projects. This study evaluates the blast resistance of the orthotropic bridge deck of the Taizhou Yangtze River Bridge using numerical simulations validated by explosion tests. Five vehicular bomb scenarios, as specified by the Federal Emergency Management Agency, were analyzed to understand the damage mechanisms under above-deck explosions. Results show that all scenarios cause petal-shaped openings in the top plate, fractures in U-stiffeners, and plastic deformation in diaphragms. Larger TNT masses lead to additional failures, such as outward bending and bottom plate openings. Energy dissipation primarily occurs through plastic deformation and failure of various deck components, with the extent depending on the TNT mass. The vehicle shell significantly reduces damage for smaller charges (454 kg TNT) but has a minor effect for larger charges (>4536 kg TNT). This research enhances the understanding of blast resistance in orthotropic steel decks, a key component in modern bridge construction, and informs practices for designing resilient structures. Full article

Widely employed in diverse engineering applications, stiffened steel plates are often subjected to biaxial compressive loads. Under these conditions, buckling may occur, initially within the elastic range but potentially progressing into the elasto-plastic domain, which can lead to permanent deformations or structural collapse. To increase the ultimate buckling stress of plates, the implementation of longitudinal and transverse stiffeners is effective; however, this complexity makes analytical stress calculations challenging. As a result, numerical methods like the Finite Element Method (FEM) are attractive alternatives. In this study, the Constructal Design method and the Exhaustive Search technique were employed and associated with the FEM to optimize the geometric configuration of stiffened plates. A steel plate without stiffeners was considered, and 30% of its volume was redistributed into stiffeners, creating multiple configuration scenarios. The objective was to investigate how different arrangements and geometries of stiffeners affect the ultimate buckling stress under biaxial compressive loading. Among the configurations evaluated, the optimal design featured four longitudinal and two transverse stiffeners, with a height-to-thickness ratio of 4.80. This configuration significantly improved the performance, achieving an ultimate buckling stress 472% higher than the unstiffened reference plate. In contrast, the worst stiffened configuration led to a 57% reduction in performance, showing that not all stiffening strategies are beneficial. These results demonstrate that geometric optimization of stiffeners can significantly enhance the structural performance of steel plates under biaxial compression, even without increasing material usage. The approach also revealed that intermediate slenderness values lead to better stress distribution and delayed local buckling. Therefore, the methodology adopted in this work provides a practical and effective tool for the design of more efficient stiffened plates. Full article

To study the mechanical properties of asymmetric K-shaped square tubular joints with built-in stiffening rib lap joints, axial tensile tests were carried out on one K-shaped joint without built-in stiffening ribs and four K-shaped joints with built-in stiffening ribs using an electro-hydraulic servo structural testing system. The effects of the addition of stiffening ribs and the welding method of the stiffening ribs on the mechanical properties were studied comparatively. The failure mode of the K-shaped joint was obtained, and the strain distribution and peak displacement reaction force in the nodal region were analyzed. A finite element analysis of the K-shaped joint was carried out, and the finite element results were compared with the experimental results. The results showed that the addition of transverse reinforcement ribs and more complete welds shared the squeezing effect of the brace on the chord. Arranging more reinforcing ribs in the fittings makes the chord more uniformly stressed and absorbs more energy while increasing the flexural load capacity of the fittings’ side plates. The presence of a weld gives a short-lived temperature increase in the area around the crack, and the buckling of the structure causes the surface temperature in the buckling area to continue to increase for some time. The temperature change successfully localized where the structure was deforming and creating cracks. The addition of the reinforcing ribs resulted in a change in the deformation pattern of the model, and the difference occurred because the flexural capacity of the brace with the added reinforcing ribs was greater than that of the side plate buckling. Full article

To study the fire resistance of castellated composite beams with semi-rigid restraints, temperature rise tests with constant loads were performed on two full-scale castellated composite beams with circular holes and semi-rigid restraints to compare the influence of whether stiffeners were set or not under semi-rigid restraints on the fire resistance of castellated composite beams. The results indicate that during the fire, the primary failure mode of castellated composite beams with semi-rigid restraints is the buckling failure of the web and lower flange in the negative moment zone at the beam end. Composite beams with stiffeners exhibited less buckling of the web and lower flange than those without stiffeners; for steel beams without stiffeners, the web and lower flange show overall lateral instability. Following the fire, the composite beams initially exhibit downward vertical deformation. After 5–10 min, when the web temperature is around 500 °C, it matures upward to the initial position. After 50 min, when the temperature of the web is around 800 °C, it starts to deform downward continuously. During the cooling stage, the end plates at the lower flange of the steel beam and the steel column show a separation phenomenon. By comparing the joint deformation and the mid-span displacement, the fire resistance performance of semi-rigid restrained castellated composite beams is better than that of hinged and rigid restraints. Numerical simulation analyses were carried out on the castellated composite beams. The simulation results showed a high degree of consistency with the test results, which effectively validated the accuracy and reliability of the proposed finite-element model. Full article

The structure of thermoset composite laminated plates is made by stacking layers of plies with different fiber orientations. Similarly, the stiffened panel structure is assembled from components with varying ply configurations, resulting in thermal residual stresses and processing-induced deformations (PIDs) during manufacturing. To mitigate the residual stresses caused by the geometric features of corner structures and the mismatch between the stiffener-skin ply orientations, which lead to PIDs in composite-stiffened panels, this study proposes a multi-objective stacking optimization strategy based on an improved adaptive genetic algorithm (IAGA). The viscoelastic constitutive model was employed to describe the modulus variation during the curing process to ensure computational accuracy. In this study, the IAGA was proposed to optimize the ply-stacking sequence of L-shaped stiffeners in composite laminated structures. The results demonstrate a reduction in the spring-in angle to 0.12°, a 50% improvement compared to symmetric balanced stacking designs, while the buckling eigenvalues were improved by 20%. Additionally, the IAGA outperformed the traditional non-dominated sorting genetic algorithm (NSGA), achieving a threefold increase in the Pareto solution diversity under identical constraints and reducing the convergence time by 70%. These findings validate the effectiveness of asymmetric ply design and provide a robust framework for enhancing the structural performance and manufacturability of composite laminates. Full article

In view of the application status and technical challenges of steel–wood composite joints in architecture, this paper proposes an innovative connection technology to solve issues such as susceptibility to pry-out at beam–column joints and low load-bearing capacity and to provide various reinforcement methods in order to meet the different structural requirements and economic benefits. By designing and manufacturing four groups of beam–column joint specimens with different reinforcement methods, including no reinforcement, structural adhesive and angle steel reinforcement, 4 mm thick steel sleeve reinforcement, and 6 mm thick steel sleeve reinforcement, monotonic loading tests and finite element simulations were carried out, respectively. This research found that unreinforced specimens and structural adhesive angle steel-reinforced joints exhibited obvious mortise and tenon compression deformation and, moreover, tenon pulling phenomena at load values of approximately 2 kN and 2.6 kN, respectively. However, the joint reinforced by a steel sleeve showed a significant improvement in the tenon pulling phenomenon and demonstrated excellent initial stiffness characteristics. The failure mode of the steel sleeve-reinforced joints is primarily characterized by the propagation of cracks at the edges of the steel plate and the tearing of the wood, but the overall structure remains intact. The initial rotational stiffness of the joints reinforced with angle steel and self-tapping screws, the joints reinforced with 4 mm thick steel sleeves, and the joints reinforced with 6 mm thick steel sleeves are 3.96, 6.99, and 13.62 times that of the pure wooden joints, while the ultimate bending moments are 1.97, 7.11, and 7.39 times, respectively. Using finite element software to simulate four groups of joints to observe their stress changes, the areas with high stress in the joints without sleeve reinforcement are mainly located at the upper and lower ends of the tenon, where the compressive stress at the upper edge of the tenon and the tensile stress at the lower flange are both distributed along the grain direction of the beam. The stress on the column sleeve of the joints reinforced with steel sleeves and bolts is relatively low, while the areas with high strain in the beam sleeve are mainly concentrated on the side with the welded stiffeners and its surroundings; the strain around the bolt holes is also quite noticeable. Full article

The failure mode of thin-walled C-channel beams typically manifests as premature local buckling of the compression flange, leading to insufficient utilization of material strength in both the flange and the web. To address this issue, this study adopts the approach of increasing the number of bends to reinforce the flange and adding V-shaped stiffeners in the middle of the web to reduce the width-to-thickness ratio of the plate elements, thereby delaying local buckling and allowing for greater plastic deformation. However, the challenge lies in the irregular cross-sectional shape and complex buckling patterns. Therefore, this paper aims to explore a suitable cross-sectional form to expand the application of stainless steel members. Subsequently, three-point bending tests were conducted on the optimally designed stainless C-channel beam with folded flanges and mid-web stiffeners. The finite element simulation results were compared and analyzed with the experimental results to validate the model’s effectiveness. After verifying the correctness of the finite element model, this study conducted numerical parameterization research to investigate the effects of the shear span ratio, complex edge stiffeners, web height–thickness ratio, and V-shaped stiffener size on the shear performance of stainless steel folded flange C-beams. The results show that changing the shear span ratio has a significant impact on the shear capacity and vertical deflection deformation of components; increasing the web height–thickness ratio can enhance the shear capacity of the component; elevating the V-shaped stiffener size can slightly improve the shear capacity of components; and for the stainless steel C-shaped beam with folded flanges and intermediate stiffening webs, adding edge stiffeners cannot remarkably promote the shear capacity of the component. Full article

To investigate the design principles and simplified calculation model of large-size PBL-stiffened steel–concrete joints, this study uses a Y-shaped rigid frame-tied arch composite bridge as an engineering background. Based on deformation coordination theory, a combination of theoretical analysis and numerical simulation was employed to derive a simplified calculation model that accounts for boundary conditions such as the stiffness of steel beam end restraints and the local bearing effect of the bearing plate. Parametric analysis of the steel–concrete joint was conducted. The results indicate that the derived simplified calculation model exhibits good accuracy and is suitable for calculating force transfer in various components of the steel–concrete joint under different boundary conditions. Using the simplified model, the effects of parameters such as steel–concrete joint length, connector stiffness, and structural axial stiffness on the axial force transfer in primary force-bearing components (connectors and bearing plates) were studied. The findings reveal that an excessively long steel–concrete joint does not effectively reduce maximum shear force; variations in connector stiffness primarily affect connectors farther from the bearing plate without changing the shear force distribution. Increasing the axial stiffness of the steel structure within a certain range can improve the maximum shear force in connectors, whereas increasing the axial stiffness of the concrete structure has the opposite effect. Full article

Curved continuous steel box girders are extensively utilized in bridge construction due to their efficiency and environmental benefits. However, in regions with significant temperature fluctuations, temperature effects can result in cumulative deformation and stress concentration, which may severely impact structural safety and durability. This study examines the structural response of curved continuous steel box girders with five spans under diverse temperature conditions and also develops a comprehensive parameterized thermodynamic numerical model. The model assesses the influence of cross-sectional shape parameters, including the number of cross-sectional box chambers, diaphragm thickness, and height-to-width ratio, as well as longitudinal structural parameters such as planar configurations, width-to-span ratio, and support arrangements, along with the arrangement of stiffening ribs on the temperature-induced effects in the girders. The results indicate that optimizing the width and eccentricity of support stiffeners to 30% and 25%, respectively, in support plate size can significantly alleviate local temperature-induced stresses. Additionally, variations in longitudinal and transverse stiffeners manifest minimal impact on thermal performance. These findings provide a theoretical foundation for improved design and construction practices, offering practical design recommendations to mitigate temperature effects and enhance the longevity and safety of such structures. Full article

Multiscale parameter optimization for laser peen forming (LPF) on 6005A-T6 aluminum alloy plates was conducted through a combination of simulation and experimentation. By obtaining the optimal parameter, this study aims to explore the constrained deformation and forming laws of the integral stiffened plates. Detailed descriptions were provided regarding the dynamic response process and transient behavior of aluminum alloy plates under ultrahigh strain rates, along with an in-depth analysis of the stress evolution. The results reveal that laser beam diameter and laser beam energy can achieve large range forming, while the number of tracks facilitates the precise deformation adjustment. During the 12-track LPF process, there is an overall upward trend in deformation values accompanied by a dynamic increase in the bend curvature. After static relaxation, the deformation value recovers to 55.2% of the final bending curvature. The chord direction scanning of stiffened plates exhibits a larger bending curvature, indicating its greater forming capacity for large-sized single unfolding direction formation; whereas, the unfolding direction scanning of stiffened plates excels in achieving efficient integrated two-way forming. Full article

Gantries and beams, as the main load-bearing structures of heavy equipment, usually belong to the box structure consisting of outer walls and inner stiffened plates. The structure of the stiffener layout is bulky due to empirical design, leading to higher material consumption and impacting mechanical performance. There are challenges in effectively identifying load-transferred paths within 3D box structures through direct topological optimization. A method for optimizing the layout of internal stiffened plates of large box structures based on load paths is proposed in this paper. Initially, based on the load conditions acting on the structure, the 3D box structure is decomposed into 2D functional sections. Subsequently, the load paths on the functional cross-section are visualized according to the load path method. Finally, the stiffener layout of the ultimate optimized structure is designed according to the effective load path distribution. Taking the gantry of a heavy-duty aluminum ingot composite processing unit as an example, the optimization results indicate that the maximum stress of the structure decreased by 14.9%, the maximum deformation reduced by 32.95%, and the overall weight decreased by 14.4%. This demonstrates that the approach proposed in this paper is practical and effective for optimizing stiffener layouts in large-box structures. Full article

Differing from previous studies on free-drop tests, this study focuses on the ultimate bearing capacity and failure mechanism of the ship’s bow under slamming loads. A prototype ship’s bow is selected to design two simplified stiffened plates with different stiffeners, and the lateral slamming loads used are equivalent to flare slamming loads. Free-drop tests of the two simplified models are conducted, and the test setups and procedures are provided. The experimental results of slamming pressures and structural responses are obtained. By comparing with the simulation results obtained by Arbitrary Lagrangian-Eulerian (ALE) fluid–structure coupling, the convergence study, symmetry, and independence verifications are carried out. Finally, the dynamic ultimate bearing capacity of stiffened plates with different stiffnesses under lateral slamming loads is studied. The results show that stiffeners enhance the ability of stiffened plates to resist plastic deformation under slamming loads, and T-section stiffeners can provide greater resistance to plastic deformation than other types. Full article

In the paper, the eccentric compression behavior of the truss-reinforced cross-shaped concrete-filled steel tubular (CCFST) column is investigated. A total of eighteen CCFST columns were tested under eccentric compression, and the key test variables included the reinforced truss node spacing (s = 140 mm and 200 mm), slenderness ratio (λ = 9.2, 16.6, and 23.1), and eccentricity ratio (η = 0, 0.08, and 0.15). The failure mode, deformation characteristic, stress distribution, strain distribution at the mid-span of the steel tube, and the eccentric compression bearing capacity were assessed. The results show that due to the addition of reinforced truss, the steel plates near the mid-span of eccentrically compressed CCFST columns experienced multi-wave buckling rather than single-wave buckling after the peak load was reduced to 85%, and the failure mode of concrete also changed from single-section to multi-section collapse failure. Comparisons were made with the unstiffened specimen. The ductility coefficient of the stiffened specimen with eccentricity ratios of 0.08–0.15 and node spacings of 140 mm~200 mm increased by 70~83%, approaching that of the multi-cell specimens with an increasing steel ratio of 1.8%. In addition, by comparing the test results with the calculation results of four domestic and international design codes, it was found that the Chinese codes CECS159-2018 and GB50936-2014, and the Eurocode 4 (2004) can be better employed to predict the compression bearing capacity of truss-reinforced CCFST columns. Full article

Skewed supports complicate load paths in continuous steel I-girder bridges, causing secondary stresses and differential deformations. For a continuous bridge where tensile stresses are developed in the top flange of the steel girders over the intermediate supports, these effects may exacerbate potential fatigue issues for the top flanges. There is a gap in knowledge regarding the level of stress one can expect at these locations, and the stress level can render the problem either serious or trivial. This paper has been successful in providing this information, which was not available before. The study examines the fatigue performance of the top flange in girders over skewed supports. Results are presented from a detailed investigation consisting of 3D finite element modeling to evaluate 26 skewed bridges in the State of Florida that represent the wide range of geometries found in practice. The analysis focused on stress ranges in the top flanges and axial demands on end cross-frame members under fatigue truck loading. A preliminary analysis helped to select the appropriate element type and support conditions. The maximum factored stress range of 3.63 ksi obtained for the selected group of bridges remains below the 10 ksi fatigue threshold for an AASHTO Category C connection, alleviating the concerns about the fatigue performance of the continuous girder top flange over the intermediate pier. Hence, fatigue is unlikely to be a concern in the flanges at this location. Statistics on computed stress ranges and cross-frame forces that provide an understanding of the expected values and guidance for detailing practices are also presented. A limited comparative refined FE analysis on two different types of end cross-frame to girder connections also provided useful insight into the fatigue sensitivities of the skew connections. Half-Round Bearing Stiffener (HRBS) connections performed better than the customary bent plate connections. The HRBS connection reduces girder flange stress concentration range by at least 18% compared to the bent plate connection. The maximum stress concentration range in bent plate components is significantly higher than in the HRBS connection components. The work documented in this paper is important for understanding the fatigue performance of the cross-frames and girders in support regions in the upcoming 10th edition of the AASHTO Bridge Design Specifications that may include plate stiffeners oriented either normally or skewed to the girder web, or Half-Round Bearing Stiffeners. Full article