Search Results (56)

The present study investigates the influence of the configurations of anchor bolts and stiffeners on the monotonic response under moment conditions in the major axis and compression force of partial-strength exposed column base plate connections in order to ameliorate their response, limiting the number of welded details. Parametric finite element simulations were performed based on models calibrated against experimental results available from the recent literature. The results show the efficiency of the investigated configurations, namely, (i) the presence of rib stiffener results in high stiffness and strength with a reduction in ductility; (ii) the linear pattern of anchor bolts (e.g., rectangular distribution) is characterized by the limited contribution of the outer anchor bolts to the overall resistance of the connection; (iii) the trapezoidal pattern of the anchor bolts exhibit a better mechanical performance as well as their efficiency; and (iv) the increase in compression force influences the mechanical response of the base connection with an increase in both resistance and rigidity until the column is stable against the moment–axial force interaction. 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

This paper presents a comprehensive on-site decision-making framework for assessing the structural integrity of a jacket-type offshore platform in the Gulf of Mexico, installed at a water depth of 50 m. Six critical analyses—(i) static operation and storm, (ii) dynamic storm, (iii) strength-level seismic, (iv) seismic ductility (pushover), (v) maximum wave resistance (pushover), and (vi) spectral fatigue—are performed using SACS V16 software to capture both linear and nonlinear interactions among the soil, piles, and superstructure. The environmental conditions include multi-directional wind, waves, currents, and seismic loads. In the static linear analyses (i, ii, and iii), the overall results confirm that the unity checks (UCs) for structural members, tubular joints, and piles remain below allowable thresholds (UC < 1.0), thus meeting API RP 2A-WSD, AISC, IMCA, and Pemex P.2.0130.01-2015 standards for different load demands. However, these three analyses also show hydrostatic collapse due to water pressure on submerged elements, which is mitigated by installing stiffening rings in the tubular components. The dynamic analyses (ii and iii) reveal how generalized mass and mass participation factors influence structural behavior by generating various vibration modes with different periods. They also include a load comparison under different damping values, selecting the most unfavorable scenario. The nonlinear analyses (iv and v) provide collapse factors (Cr = 8.53 and RSR = 2.68) that exceed the minimum requirements; these analyses pinpoint the onset of plasticization in specific elements, identify their collapse mechanism, and illustrate corresponding load–displacement curves. Finally, spectral fatigue assessments indicate that most tubular joints meet or exceed their design life, except for one joint (node 370). This joint’s service life extends from 9.3 years to 27.0 years by applying a burr grinding weld-profiling technique, making it compliant with the fatigue criteria. By systematically combining linear, nonlinear, and fatigue-based analyses, the proposed framework enables robust multi-hazard verification of marine platforms. It provides operators and engineers with clear strategies for reinforcing existing structures and guiding future developments to ensure safe long-term performance. 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 application of fillet welding in the shipbuilding industry is essential for composing different structural components such as stiffened plates and panels, which are the sub-structural elements of the entire hull. The connection between the base plating and its reinforcement members as stiffeners may be found in different fillet welding configurations such as continuous and intermittent chain welding. The application of each welding configuration may differ according to the importance of the structural component, its location and the acting load. The aim of the present work is to experimentally evaluate the ultimate compressive capacity of a stiffened plate with different base plating thicknesses and a welded stiffener using different fillet welding configurations. The results are presented in the form of different relationships between axial force–vertical/lateral displacement relationships and corresponding collapse modes. Discussion and analysis of results are performed for a deep understating of both the local and global behaviour of the stiffened plate, accounting for the absorbed energy within the elastic regime and up to the ultimate limit, with developed regression formulations. Also, a comparison between the experimental results and existing empirical formulations is performed, showing a good agreement and reasonable behaviour. Full article

The transition from polylithic (composed of many parts) to monolithic (one part) design in automotive components presents an opportunity for a reduction in part count, weight, processing routes, and production time without compromising performance. The traditional design approaches for rooftop tents assemble various sheet metal and extrusions together using different joining processes such as welding, adhesive bonding, bolting, and riveting. This is often associated with disadvantages, such as increased weight, high production time, and leaking joints. This research, therefore, presents the development of a monolithic, lightweight, stiffened, non-rotational automotive rooftop tent that is manufactured via the deep-drawing process. An onsite company case study was conducted to analyze the polylithic product and its production process to determine its limitations. This was followed by the design of a lightweight, non-rotational monolithic product whose purpose is to eliminate the identified disadvantages. The stiffness geometries were developed to enhance the overall structural integrity without adding unnecessary weight. The Analytic Hierarchy Process (AHP) was used to analyze and evaluate alternative layouts against criteria such as complexity, tool design, symmetry, rigidity, and cost. Simulations conducted using NX 2024 software confirmed the effectiveness of this design. The results show that the monolithic rooftop tent has a comparable stiffness performance between the lightweight, monolithic rooftop tent and the heavy, polylithic rooftop tent. At the same time, the part count was reduced from twenty-three (23) single parts (polylithic) to a one (1) part (monolithic) rooftop tent, the weight was reduced by 15.6 kg, which translates to a 30% weight reduction without compromising the performance, processing routes were reduced from eight (8) to three (3), production time was reduced by 120 min, and leaking was eliminated. It can, therefore, be concluded that the design and manufacturing of monolithic rooftop tents leads to a lighter and stronger product. Full article

Cable-stiffened steel columns (CSSC) have a high load-carrying capacity and strong stability compared to ordinary steel columns. In practical engineering, the connection between the crossarm and main column of a CSSC is usually welded. However, the welding-residual stress adversely affects the steel column. In this study, pre-cast CSSCs, with a pinned connection between the crossarm and main column, are presented. The new type of pre-cast CSSCs avoid the welding-residual and are easy to disassemble. A model test and numerical analysis of its global stability behavior under eccentric compression is conducted. Based on the analysis, the buckling modes of these columns are defined and a method for determining the governing imperfection in a nonlinear buckling analysis is proposed. The effects of slenderness ratio, cross-arm length, cable diameter, and other parameters on the load-carrying capacities of the columns are investigated using the proposed method. The results of this study can be used as a reference for the engineering designs and specifications of pre-cast CSSCs. Full article

Steel tubular column-to-steel beam (STCSB) connections are critical parts in offshore structures, where complex component connections and the stress concentration are of significant concern. This study conducted stress concentration tests on welded STCSB connections and subsequently developed a finite element (FE) model for the connections, with the experimental results validating the accuracy of the model. The discussion focused on the influence of parameters such as the width-to-diameter ratio of the beam to the column, the diameter-to-thickness ratio of the column, the diameter-to-thickness ratio of the column to the beam, and the height-to-thickness ratio of the beam web on the fatigue performance. The study proposed optimization methods including the addition of stiffeners and outer flange plates. The findings indicate that optimized connection configurations can effectively mitigate stress concentration in the connected areas, thereby enhancing the structural stability and fatigue life. The width-to-diameter ratio of the beam to the column and the diameter-to-thickness ratio of the column significantly affect the fatigue performance of welded STCSB connections, with an increased width-to-diameter ratio of the beam to the column or a reduced diameter-to-thickness ratio of the column leading to a substantial decrease in the maximum stress concentration factors (SCFs). The addition of stiffeners and adjustment of the outer flange plate can improve stress concentration effects in the connection area. Full article

Residual drifts are an important measure of post-earthquake functionality in bridges and buildings, and can determine whether the structure remains fit for its intended purpose or not. This study aims at investigating numerically, through finite element (FE) analysis in ABAQUS, the cyclic response of exterior steel I beam-hollow column connection using welded shape memory alloys (SMA) bolts and seat angles. This is followed by validating the numerical model using an accredited experimental data available in the literature through different techniques, (1) SMA bolts, (2) SMA angles, (3) SMA bolts and angles. The parameters investigated included: SMA type, SMA angle thickness, SMA bolt diameter, SMA angle stiffener and SMA angle direction. The cyclic performance of the steel connection was enhanced further by varying the bolt diameter, plate thickness, angle type and direction. The results revealed that the connections equipped with a combination of SMA plates and SMA angles reduced the residual drift by up to 94%, and doubled the self-centering capability compared to conventional steel connections. Moreover, the parametric analysis showed that Fe-based SMA members could be a good alternative to NiTi based SMA members for improving the self-centering capability and reducing the residual drifts of conventional steel connections. Full article

Welding residual stress will aggravate the fatigue cracking damage of the structure and have an essential impact on the structure’s load-bearing capacity. The welding sequence will directly affect the size and distribution of welding residual stress. To this end, this paper establishes a thermal–mechanical sequential indirect-coupling finite-element analysis model, researches the residual stress of steel-plate composite girder bridges considering the welding sequence, and verifies the analysis results through field tests. Then, a three-span steel-plate composite continuous girder bridge was taken as the research object, and the residual stress of the stiffener welds in seven welding sequences was analyzed. On this basis, the equivalent peak-stress method is used to evaluate and predict the fatigue strength of the weld. The research results show that welding residual stresses change the multiaxial stress state of fatigue details. Although under the same external load cyclic stress, the difference in welding sequence directly leads to a significant difference in the equivalent peak stress of the stiffeners, and this difference results in different fatigue properties of the stiffeners. The research results can provide a basis for the welding process and fatigue analysis of stiffener welds in steel-plate composite girder bridges. Full article

Joining high strength 2xxx series aluminum is known to be complex and difficult; these alloys are traditionally considered non-weldable for fusion welding. This paper describes details on welding AA2029-T8 for skin-stiffened structures using refill friction stir spot welding (RFSSW). RFSSW is a solid-state process invented in the early 2000s that produces spot welds that are strong, lightweight, flush, and hermetic. Cycle times between 1 and 3 s are discussed, and process forces within a range of 8 to 14 kN are demonstrated. Furthermore, lap-shear quasi-static tensile strengths are shown to be between 10 kN and 12 kN in 9 mm diameter spots. A comparison of the performance of RFSSW welds made with various tool materials—which include H13 tool steel, tungsten carbide, and MP159—is detailed. Comparisons of parameters, weld consolidation, and heat-affected zones are presented with discussion related to heat generation specific to each tool material. Full article

Orthotropic steel bridge decks (OSDs) are very popular all over the world because of the low dead load, high stiffness in the longitudinal direction, high strength ratio to weight, and can be used in various types of bridges. The life of these bridges is affected by fatigue cracks in different portions. One of major areas where the fatigue cracks appear in these bridges is rib-to-deck connection. In this research finite element analysis is carried out by using ABAQUS/CAE 2022 software to determine the ways to increase the fatigue life at rib to deck connection in OSDs. In the first part, smaller models are simulated; stress concentration is analyzed and hot spot stress (HSS) is calculated according to International Institute of Welding (IIW) and Det Norske Veritas (DNV) recommendations. In the second part, a parametric analysis is carried out to analyze the effect of weld penetration, thickness of deck, thickness of rib and rib to deck connection type. In the third part, simulation of models similar to the real field is carried out to determine whether the double welded connections are better than single welded connections. Different models are analyzed for different load cases like single wheel load, double wheel load and also the position of the wheels is changed. The boundary conditions are changed to analyze whether the boundary condition has any significant effect on the result obtained. It is found that thicker decks, thinner ribs, and low penetrated welded connections reduce the stress concentrations at rib to deck connections which ultimately increase fatigue life. Among the parameters examined, deck thickness is the most important parameter. It is found that the percentage of stress increase with percentage decrease in deck thickness follows a power relation. The overall fatigue life of double welded connection is excepted to be lower since the stress concentration is maximum at the weld toe at deck on the outer side of the closed stiffener; however, if the cracks initiate on the inner side of closed stiffener, the cracks at the weld root of single welded connection can propagate much rapidly than the cracks initiating on the inner side of the closed stiffener at the weld toe, thereby reducing the fatigue life of the single-welded specimen significantly. Full article

To study the mechanical performance of bolted connections with different structural forms of reinforced rings, based on the results of monotonic loading tests on two bolted connections between a concrete-filled steel tubular column and a steel beam with an outer reinforcing ring, this article uses ABAQUS v.2020 software to establish a three-dimensional refined finite element analysis model of such connections using appropriate constitutive models for concrete and steel. Subsequently, the effect of the dimensions of the steel beam, reinforcing ring, and cover plate on the load-bearing properties and the failure mechanism of the connections is investigated, and the numerical model is consistent with the verification test results. Then, the numerical simulations comparing bolted exterior reinforced rings under seven different construction measures (i.e., number of bolts, stiffeners) based on a conventional welded exterior reinforced rings with rigid connections (i.e., CGJ) are standardized. The research results indicate that when four rows of bolts are introduced on exterior reinforced rings, the web of steel beam is welded with stiffeners, and the top and bottom reinforced rings are also added with stiffeners; this bolted connection with an external reinforcing ring (i.e., GZ-7) can achieve the rigidity and load-bearing capacity of a fully welded external reinforcing ring rigid connection. At the same time, the reinforcing ring plate is bolted to the flange of the steel beam, and the force transmission path at the connection is changed to avoid the brittle fracture easily caused by the welded flange joints. It is also in line with the development trend of sustainable construction of “assembly” and “disassembly”. Full article

This study investigates the secondary bonding of aircraft skin/stiffener assemblies using press conduction welding with carbon fiber/polyetherketoneketone thermoplastic composites and polyetherimide adhesive. Recognizing the challenges posed by conventional welding methods in maintaining material integrity and uniformity, this research explores an alternative methodology that mitigates these issues while ensuring high-strength bonds. The press conduction welding parameters were selected based on single-lap shear tests and applied in the bonding of skin and omega stiffener components. The temperature range was determined using differential scanning calorimetry. The pressure was held at 1 MPa for 180 s. The welding temperature that produced a high-bonding strength was identified experimentally; these key variables were then used in the welding process of the skin and omega stiffener. By analyzing how the fibers tear and the effectiveness of interdiffusion between the plies, we were able to gain insights into the bonding strength and fractured surface. The findings suggest that press conduction welding provides a viable route for secondary bonding in thermoplastic composite structures, highlighting its advantages in terms of processing efficiency and integrity. This study contributes to the understanding of the mechanical behaviors of bonded joints and underscores the significance of temperature control in the welding process. Full article

The safe and cost-effective design of wind turbine towers is a critical and challenging aspect of the future development of the wind energy sector. This process should consider the continuous growth of towers in height and blades in length. Among potential failure modes of tubular steel towers, shell local buckling due to static axial compressive stresses from the rotor, blades, and tower weight, as well as dynamic flexural compressive stresses from wind actions on the rotating blades and the tower itself, are dominant as thickness is optimized to reduce weight. As man door and ventilation openings are necessary for the towers’ operation, the local weakening of the tower shell in those areas leads to increased buckling danger. This is compensated for by tower manufacturers by the provision of stiffening frames around the openings. However, the cold-forming and welding of these frames are among the most time-consuming aspects of tower fabrication. Working towards the optimization of this design aspect, the buckling response of tubular steel towers near such openings is investigated by means of nonlinear finite element analysis, accounting for geometrical and material nonlinearity and imperfections (GMNIA), and also considering several wind directions with respect to the openings. The alternatives of stiffened and unstiffened openings are investigated, revealing that a thicker shell section around the opening may be sufficient to restore lost stiffness and strength, while the stiffener frame may also be eliminated, offering substantial benefits in terms of manufacturing effort, time and cost. Full article