Search Results (73)

Longitudinal shuttle-shaped concrete-filled steel column with cruciform sections (LSS-CFST-CS) is highly valued by architects and structural engineers for its distinctive appearance and significant architectural impact in spatial steel structures. However, there are currently no available studies addressing the buckling behavior, load-carrying capacity, and strength design methods of such structures. This study numerically investigates the elastic buckling behavior, load-carrying capacity, and design methods of LSS-CFST-CS under axial compression, as well as under combined axial compression and bending moment. First, closed-form solutions for the elastic buckling load under axial compression are derived for a pinned–pinned tapered concrete-filled steel column (TCFST) with cruciform sections and standard LSS-CFST-CS, respectively. The resulting solutions are validated against finite element (FE) numerical results from a wide range of LSS-CFST-CS examples, and the corresponding buckling modes are examined. Next, a unified expression for the elastic buckling load under axial compression is established for both types of TCFST and standard LSS-CFST-CS. Finally, a parametric study incorporating initial geometric imperfections is conducted to investigate the load-carrying capacity of LSS-CFST-CS and to quantify the influence of key parameters on stability capacity. On this basis, design recommendations for the stability capacity are proposed for axial compression and combined axial compression and bending moment of LSS-CFST-CS, respectively. Full article

Conventional buckling-restrained braces (BRBs) with rectangular steel tube confinement suffer from stress concentration and inefficient material utilization, limiting their seismic performance. To address these limitations, this study proposes a novel non-rectangular concrete-filled steel tube BRB system incorporating elliptical and corrugated cross-sections. Comprehensive finite element simulations using ABAQUS are conducted to systematically investigate the influence of key geometric parameters—wall thickness (1–14 mm), corner radius (40–55 mm), and corrugation angle (30–75°)—on hysteretic behavior, load-bearing capacity, and failure modes. The results demonstrate that optimized non-rectangular sections achieve load-bearing capacity comparable to conventional rectangular designs (e.g., elliptical section with 12 mm wall thickness reaches 10.02 MN, a 75% increase over 1 mm thickness) while significantly improving material efficiency. Corrugated sections exhibit enhanced weak-axis performance, with equivalent viscous damping ratios exceeding the NIST-recommended threshold of 0.25. Parametric analyses reveal that wall thickness above 12 mm yields diminishing returns; corner radius reduction to 40 mm triggers local buckling yet increases peak capacity; and corrugation angles exceeding 50° induce instability. All non-buckling models satisfy AISC compression strength adjustment factor requirements (β ≤ 1.3). This study systematically evaluates non-rectangular BRB geometries, filling a critical gap in the literature and providing design guidelines that leverage shape optimization to enhance both seismic resilience and material economy. Full article

In this paper, the forked-web joint configuration was introduced first, in order to transfer the shear and moment forces better and avoid the local buckling problem that usually happens in narrow steel beams and concrete-filled steel tubular (CFST) column joints. Experiments including three specimens of that joint were then conducted, considering different axial compression ratios of the column. The test results indicated that no failure phenomenon happened to the proposed joint when the equivalent rotational angle was no more than 1/50. However, the final failure mode of each specimen was still local buckling and tearing failure of beam flanges due to the excessively large stress. Finally, based on the tests and FEA results, a corresponding improvement, including a single-web configuration with U-shape and triangular stiffeners, was thus brought forward and numerically verified in terms of rotational stiffness, failure mode, and the hysteretic curve. The FEA results revealed that the rotational stiffness of the proposed single-web joint with triangular stiffeners for beams and U-shape stiffeners for CFST columns efficiently increased from 0.87 to 3.83, and it was almost twice that of the narrow beam-column joint with internal horizontal diaphragms. Moreover, the previous undesirable tearing failure mode was finally avoided by adopting high-strength steel Q550 for the joint beam part. Full article

L-shaped concrete-filled steel tubular (CFST) columns have attracted increasing attention in recent years due to their favorable seismic performance and their ability to reduce column protrusions into interior wall surfaces. Existing studies on L-shaped CFST columns have mainly focused on a specific cross-section form, and the mechanical behavior of L-shaped CFST columns with different limb length ratios and inter-limb angles has not yet been sufficiently investigated. To further examine the axial compressive performance of L-shaped CFST columns, this study designed and tested eight L-shaped CFST columns by considering the cross-section form, limb-length ratio, and inter-limb angle as key parameters. In addition, a simplified formula for predicting the axial load capacity of L-shaped CFST columns was proposed based on the unified theory. The test results indicated that the cross-section form significantly affects both load-carrying capacity and ductility. For the equal-limb specimens, the peak load of the C-type specimen was 8% and 9% higher than that of the A-type and B-type specimens, respectively, whereas the displacement ductility coefficient of the A-type specimen was 48% and 47% higher than that of the B-type and C-type specimens, respectively. Compared with the unequal limb specimens, the equal limb specimens exhibited an increase in peak load of more than 20%; moreover, the displacement ductility coefficients of the A-type and B-type specimens increased by 48% and 61%, respectively. Increasing the inter-limb angle enhanced the peak load but reduced the ductility, and it led to a gradual shift in the failure mode from local buckling of the steel tube to overall bending. The findings of this study contribute to a more comprehensive understanding of the mechanical behavior of L-shaped CFST columns and can provide reference for their design and optimization. Full article

This study addresses a fundamental shortcoming in conventional dynamic stability analyses of space trusses: traditional rod elements or unsegmented beam models fail to capture member buckling under severe seismic excitation, often mischaracterizing structural failure modes, namely mistaking collapse due to instability for mere loss of loadbearing capacity. To overcome this limitation, we propose a multi-segment beam numerical method that discretizes each member into multiple segments enhanced with high order shape functions. Validation through modal analyses of simply supported beams, isolated space trusses, and space truss–frame systems reveals that while conventional unsegmented beam models accurately predict low order vibration frequencies, they entirely neglect member buckling in higher modes. Under strong earthquake loading, these models misleadingly indicate global stability accompanied by gradual degradation of load capacity. In contrast, the multi-segment beam model simultaneously resolves low order global vibrations and high order local buckling phenomena, unveiling progressive seismic instabilities triggered by member buckling. Dynamic stability analyses confirm that the multi-segment approach reliably identifies the true critical failure mode. This paper recommends that in the modal analysis and seismic stability analysis of space trusses, the space truss members should be divided into three segments with cubic shape functions selected for the analysis. This methodology thus provides precise predictions of failure mechanisms and critical seismic thresholds, enabling dependable safety evaluations for long-span spatial structures in seismic regions. Full article

This study examines how circular and star-shaped damage affects Aluminum-2024-T3 helicopter fuselage panels, focusing on damage shape, size, and location. Using finite element analysis, conventional stiffened panels are compared with isogrid rib-stiffened ones under combined compression and shear. Isogrid panels show superior performance, with reduced displacements, lower von-Mises stress, higher stiffness, and improved damage resistance, especially against star-shaped damage. They retain higher natural frequencies and stability under damage, while conventional panels lose performance, especially in mode one. Isogrid panels also achieve higher buckling load factors, maintaining structural integrity despite damage, making them ideal for design optimization despite a 16.7% weight increase. Full article

This study presents an analysis of transverse vibration behavior of a fluid-conveying pipe mounted on an elastic foundation, incorporating both classical analytical techniques and modern physics-informed neural network (PINN) methodologies. A partial differential equation (PDE) architecture is developed to approximate the solution by embedding the physics PDE, initial, and boundary conditions directly into the loss function of a deep neural network. A one-dimensional fourth-order PDE is employed to model governing transverse displacement derived from Euler–Bernoulli beam theory, with additional terms representing fluid inertia, flow-induced excitation, and stochastic force modelled as Gaussian white noise. The governing PDE is decomposed via separation of variables into spatial and temporal components, and modal analysis is employed to determine the natural frequencies and mode shapes under free–free boundary conditions. The influence of varying flow velocities and excitation frequencies on critical buckling behavior and mode shape deformation is analyzed. The network is trained using the Resilient Backpropagation (RProp) optimizer. A preliminary validation study is presented in which a baseline PINN is benchmarked against analytical modal solutions for a fluid-conveying pipe on an elastic foundation under deterministic excitation. The results demonstrate the capability of PINNs to accurately capture complex vibrational phenomena, offering a robust framework for data-driven modelling of fluid–structure interactions in engineering applications. Full article

This paper explores the application of the generalized beam theory (GBT) in analyzing the buckling behavior of isotropic and composite thin-walled beams with open cross-sections, both with and without branching. The composite beams are composed of orthotropic laminate layers arranged in arbitrary symmetrical orientations. By integrating GBT with the Ritz method and solving the associated generalized eigenvalue problem (GEP), an efficient and robust semi-analytical framework is developed to assess the stability of such isotropic and orthotropic members. The novelty of this work is not the GBT cross-sectional formulation itself, but its implementation at the beam level using a Ritz formulation leading to a generalized eigenvalue problem for the critical buckling loads and mode shapes that capture coupled global, local, and distortional modes in isotropic and orthotropic composite members. This makes the method suitable for early-stage design studies and parametric investigations, where many design variants (geometry, laminate lay-up, and aspect ratios) must be screened quickly without building large-scale high-fidelity finite element (FE) models for each case. The preliminary outcomes, when compared with those obtained using FE, confirm the approach’s effectiveness in evaluating buckling responses, particularly for open-section composite beams. Ultimately, the combined use of GBT and the Ritz method delivers both physical insight and computational efficiency, allowing engineers and researchers to address complex stability issues that were previously difficult to solve. In summary, the methodology can be correctly used for stability assessment of thin-walled composite members prone to interacting global–local–distortional buckling, especially when rapid, mechanistically transparent predictions are required rather than purely numerical FE output. Full article

This paper develops a novel design formula to estimate the residual strength of corroded stiffened cylindrical structures. It extends a previously established ultimate strength formulation for intact cylinders by introducing a corrosion-induced strength reduction factor. The foundational formula considers failure mode interactions like yielding, local buckling, overall buckling, and stiffener tripping. This research utilizes recent experimental and numerical investigations on corroded ring-stiffened cylinder models. Experimental results validate the numerical analysis method, showing good agreement in collapse pressures (2–4% difference) and shapes. The validated numerical method is then subject to an extensive parametric study, systematically varying corrosion characteristics. Results indicate a clear relationship between corrosion volume and strength reduction, with overall buckling being more sensitive. Based on these comprehensive results, a new empirical strength reduction factor (${\rho }_c$) is derived as a function of the corrosion volume ratio ($V_{non}$). This factor is integrated into the existing ultimate strength formula, allowing direct residual strength estimation for corroded structures. The proposed formula is rigorously verified against experimental and numerical data, showing excellent agreement (mean 1.00, COV 5.86%). This research provides a practical, accurate design tool for assessing the integrity and service life of corroded stiffened cylindrical structures. Full article

Web-tapered beams with I-sections, which are aesthetic and structurally efficient, have been widely used in steel structures. Web-tapered I-section beams bent about the strong axis may undergo out-of-plane buckling through lateral deflection and twisting. This primary stability failure mode in slender beams is known as lateral-torsional buckling (LTB). Unlike prismatic I-beams, the complex mode shape of web-tapered I-section beams makes it challenging or even impossible to derive a closed-form expression for the LTB load under certain transverse loading conditions. Therefore, the LTB assessment of web-tapered I-section beams is primarily performed using finite element analysis (FEA). However, this method involves multiple steps, requires specialized expertise, and demands significant computational resources, making it impractical in certain cases. This study proposes an analytical approach based on the Ritz method to evaluate the LTB of simply supported web-tapered beams with doubly or mono-symmetric I-sections. The proposed analytical method accounts for web tapering, I-section mono-symmetry, types and positions of transverse loads, and beam slenderness. The method was implemented in Mathematica to allow the rapid evaluation of the LTB capacity of web-tapered I-beams. The study validates the LTB loads computed using the developed Mathematica package against results from shell-based FEA. An excellent agreement was observed between the analytically and numerically calculated LTB loads. 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

Three-dimensional printing is a highly promising manufacturing technology that enables easy production of complex shapes. Composite lattice structures are highly efficient, having the advantages of fiber-reinforced composites and the excellent structural performance of lattice configurations. Highly efficient structures can be developed by combining the benefits of 3D printing and composite lattice structures. This study examined the effect of printing path and axial angle in joint areas on the compressive strength of composite lattice unit cells fabricated via continuous fiber 3D printing. Compression tests were conducted to analyze deformation, failure modes, and causes of failure. A finite element model was used to analyze buckling behavior and establish design criteria. Results showed that the printing path significantly influenced failure mode and strength, while a fabrication method without a defect at the joint was important for improving structural performance. Finally, design criteria, in terms of the knockdown factor and in-plane bifurcation buckling behavior, were developed based on experimental and numerical results. Full article

A novel L-shaped concrete-filled steel tube (CFST) column is proposed in this study. A finite element model of the column is developed using ABAQUS software to analyze its load transfer mechanism and axial compressive behavior. The effects of factors such as the steel strength, steel tube thickness, support plate configuration, and perforation of the support plates on the compressive performance of the column are investigated. The simulation results reveal that the column exhibits robust axial compressive performance. Increasing the steel strength and incorporating support plates (SP) effectively enhance the column’s compressive bearing capacity and positively influence the bearing capacity coefficient (δ). However, increasing the steel tube thickness results in a reduction in δ, indicating that the rate of increase in the bearing capacity diminishes with increasing thickness. The failure mode is primarily characterized by local buckling in the midsection of the steel tube’s concave corner. Measures such as increasing the steel strength and tube thickness and the use of support plates help to mitigate buckling at the concave corner, improve concrete confinement, and enhance the overall compressive performance of the column. Full article

An asymptotic analytical method is proposed to study the thermal post-buckling behaviors of fiber-reinforced composite (FRC)-laminated beams with geometric imperfections employing a modified zig-zag beam model. The beam model satisfied the discontinuity of the shear deformation at the interlayer interfaces and the stress boundary conditions on the upper and lower surfaces. Each imperfection was assumed to possess the same shape as the buckling mode, and the in-plane boundary conditions were presumed to be immovable. A two-step perturbation method was used to solve the nonlinear governing equations and obtain the equilibrium path. Subsequently, the initial defect sensitivity of the post-buckling behaviors was analyzed. The existence of the bifurcation-type equilibrium path for perfect beams is discussed in depth. Load–deflection curves for beams with various boundary conditions and ply modes were plotted to illustrate these findings. The effects of the slenderness ratio, elastic modulus ratio, thermal expansion coefficient ratio, ply modes, and supported boundaries on the buckling and post-buckling behaviors were also investigated. The numerical results indicate that the slenderness ratio significantly influences the critical buckling temperature, with thicker beams exhibiting higher buckling resistance. The elastic modulus ratio also plays a crucial role, with higher ratios leading to increased buckling strength. Additionally, the thermal expansion coefficient ratio affects the post-buckling load-bearing capacity, with lower ratios resulting in greater stability. 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