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Block tearing and local buckling of aluminum alloy gusset joint plates
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Aluminum Alloy Gusset (AAG) joints widely used in the single-layer latticed shells have a significant application prospect in spatial structures. Unfortunately, studies on the resistance of AAG joints are insufficient, leading to a lack of applicative design methods for this joint system. This paper is devoted to investigate the resistance of AAG joint plates. Firstly, tests on fourteen AAG joint specimens are carried out to explore their collapse modes. Experimental phenomena show that the main collapse modes of AAG joint plates include the block tearing of top plates and the local buckling of bottom plates. Secondly, Finite Element (FE) simulations to investigate the mechanical behavior of AAG joints are performed by means of the non-linear FE code ABAQUS. Thirdly, formulae for predicting the block tearing resistance and the local buckling resistance of AAG joint plates are proposed, which are based on theoretical analyses. Fourthly, test results are of great help in the determination of parameters k and α which are adopted to modify the block tearing resistance and the local buckling resistance respectively. Finally, a comparison of test results verifies that theoretical formulae are applicable. In addition, in order to avoid the block tearing and the local buckling of AAG joint plates, convenient design criteria are provided.
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... A large number of researchers have conducted in-depth studies of aluminum alloy gusset joints, as they are applied in more practical engineering projects. From 2015 to 2016, Guo et al. [8][9][10][11] conducted axial compression tests on 63 Chinese-made 6061T6 aluminum alloy profiles and verified the relevant specifications. They summarized the failure modes of AAG (aluminum alloy gusset) joints through experiments and simulations, proposed a formula for the bending stiffness of AAG joints, and recommended calculation formulas for the tearing resistance and local buckling resistance of AAG joint plates. ...
Current research on aluminum alloy gusset joints has neglected the influences of the angle between members and the curvature of the joint plate on joint performance. This study introduces the concept of the planar angle and establishes 16 joint models using ABAQUS finite element software with parameters such as the planar angle, arch angles, joint plate thickness, web thickness, and flange thickness. The load-bearing capacity of the novel aluminum alloy arch gusset joint is theoretically analyzed, and the concepts of strong and weak axes are proposed. The failure modes and significance of different parameters regarding the bearing capacity and initial stiffness of the joint under various parameters are summarized. The results indicate that the planar and arch angles significantly affect the bearing capacity, stiffness, and failure mode of the joint.
... Guo et al. [1][2][3] conducted an experimental study on the out-of-plane bearing capacity of plate joints and obtained the failure modes of the joints under different plate thicknesses. They found that as the plate thickness increased, the stiffness of the joints increased. ...
In the article, the semi-permanent aluminum alloy portal frame is used as the research background, beam-column joints are used as the research object, and experimental and numerical analyses are carried out. The influence of different bolt diameters and arch angles on the mechanical properties of beam-column joints under vertical load was analyzed using five sets of experiments. The experimental results show that the load–displacement curves of different bolt diameters in the elastic stage are basically consistent. After entering the plastic stage, the ultimate load first increases and then decreases, and the ultimate displacement is basically consistent. According to the experiment, there is no significant difference in the load–displacement curve when the arch angle increases from 90 degrees to 108 degrees. When the arch angle increases to 126 degrees, the stiffness and ultimate bearing capacity of the node under vertical load significantly increase. Then, a numerical analysis model was established to analyze the mechanical performance of beam-column joints under horizontal loads. The numerical analysis results indicate that under horizontal load, as the diameter of the bolt increases, the yield load, yield displacement, ultimate load, and ultimate displacement of the beam-column node exhibit no significant changes, and the change amplitude is minimal. When the beam-column node is subjected to horizontal loads, as the arch angle increases, the yield and ultimate displacement increase by 2.14 times and 2.78 times, respectively, and the yield and ultimate load decrease by 58% and 48%, respectively. Finally, a simplified design method for beam-column joints was proposed based on experiments and numerical analysis.
Regarding the damage incurred by aluminum alloy latticed shells under fire loads, a crucial aspect in assessing structural integrity is examining the residual bearing capacity of aluminum alloy gusset (AAG) joints. Consequently, this paper conducted experimental and numerical analyses on the post-fire flexural behavior of AAG joints. Initially, twelve AAG joints underwent post-fire tests, revealing that the failure patterns differed between thin-plate joints (exhibiting block tearing of gusset plates) and thick-plate joints (exhibiting member buckling). Notably, the initial stiffness approximately remained constant, while a trilinear relationship emerged between the ultimate flexural bearing capacity and the maximum post-fire temperature. Subsequently, finite element (FE) analysis was carried out, and the accuracy of FE models was verified by comparing the FE results with the test results. A comprehensive parametric analysis, considering various plate thicknesses, post-fire temperatures, and aluminum alloy brands, was then conducted. Ultimately, employing statistical regression, theoretical equations were formulated to estimate both bending stiffness and bearing capacity for AAG joints after exposure to fire.
Single layered domes are susceptible to large deflections and their post-buckling behavior is influenced by the connection system used. Numerous investigations have been carried out on the stiffness characteristics and of hollow spherical joints and their effect on the post-buckling behaviour of domes. However, research on the behavior of circular plated joints and their effect on the dome post-buckling are limited. Factors such as the combination of forces transferred to the joint, thickness of the circular joint plates and location of the joint in the dome have been found to influence the behaviour of the joint and the deformation of the connections reduce the limit point of the dome. Therefore, this study highlights the influence of the deformability of the circular plated joints on the elastic post-buckling behaviour of single layer domes. The deformation of the circular plated joints are investigated by geometric nonlinear finite element analysis in ABAQUS. It is found that the deformations increase with increase in ratio of minor to major force and the variation in stiffness of the plates along these directions are greater for thicker plates. Provision of shear connector i.e., a plate element between the webs of members along the direction of principal tension is effective in limiting the connection deformations. The deformability of the joints under various loading conditions are presented based on the results of the numerical investigations. The effect of the circular plate deformations on the stability of the dome are analysed using the corotated-Updated Lagrangian formulation where, the stiffnesses of the circular plates obtained from the ABAQUS analysis are included as linear springs in series with the members of the dome. Reduction in the limit point of the domes is observed, particularly with thinner circular plates.
This study presents enhancements made to traditional aluminum alloy gusset (AAG) joints, including the integration of a central stiffening (CS) system, an inter-panel stiffening (IS) system, and a peripheral stiffening (PS) system. Three sets of tests on a full-scale specimen are conducted to investigate the improved AAG joint's axial stiffness, in-plane and out-of-plane bending stiffness, as well as ultimate load-bearing capacity. Nonlinear refined finite element models (FEMs) are established and validated through experimental results. Theoretical mechanical models are developed by integrating experiments and FEMs. These models elucidate the contribution of the stiffening systems to the joint's mechanical performance. The CS system is proven to significantly assist in load transfer, particularly in out-of-plane bending conditions. The IS system enhances overall inter-panel integrity, especially during the plastic deformation phase under out-of-plane bending moments. The PS system improves joint stiffness by participating in load transmission under both axial load and in-plane bending moments. Compared to traditional AAG joints, the combined effects of the three stiffening systems enhance overall structural integrity, stiffness, and load-bearing capacity. This enables the full utilization of component material properties and provides excellent ductility before failure occurs.
In previous research, an aluminum alloy honeycomb plate cylindrical reticulated shell structure was designed. The bearing capacity test and numerical analysis show that the numerical analysis model of honeycomb plate cylindrical reticulated shell structure is reliable. In this paper, the seismic performance of the honeycomb plate cylindrical reticulated shell structure was investigated by modal analysis and time-procedure analysis. The results show that the low-order vibration modes of the cylindrical reticulated shell structure are generally dominated by lateral translational, plane torsional or vertical vibration. The natural frequency of cylindrical reticulated shell structure with bottom plate is greater than that of cylindrical reticulated shell structure without bottom plate, which has more reasonable mass, stiffness distribution. The cylindrical reticulated shell structure with bottom plate has better seismic performance, and its deformation under rare earthquake meets the specification requirements.
Aluminium alloy gusset (AAG) joints are typical semi-rigid joints widely used in single-layer reticulated shells. Despite the semi-rigid behaviour of the AAG joints, structural analyses still show that dangerous situations can occur. To study the semi-rigid performance of the AAG joints, experiments on fourteen AAG joints are conducted. Initially, the failure modes of the AAG joints are summarised in terms of their collapse phenomena and the stress distributions of the plates are discussed based on the measured strain. Subsequently, the primary characteristics of the M-φ curves of the AAG joints are obtained. The bending stiffness properties of AAG joints are also investigated. The experimental results indicate the following: (1) the primary failure modes include member rupture, member buckling, block tearing of the top plates and local buckling in the bottom plates; (2) the moment-rotation relationship of the AAG joints exhibits a significant inelastic response; and (3) as the thickness of the gusset plate increases, the initial stiffness of the joint increases.
New polyhedron space frame structure is adopted in the National Swimming Center 'Water Cube'. Circular hollow sections, square hollow sections and rectangular hollow sections are employed as structural members, while welded hollow spherical joints are employed to connect the members. This paper investigates the structural behavior and load-carrying capacity of welded hollow spherical joints connected with square steel tubes and subjected to axial forces, bending moments and combined loading of the two. Based on the elastic-perfectly plastic model and the Mises yield criterion, a finite element model for the analysis of these joints is established, in which the effect of geometric nonlinearity is taken into account. A major parametric study was then carried out employing this model. It is shown that when the welded spherical joint is subjected to combined axial forces and bending moments, the axial force-bending moment correlation is independent from their geometric parameters, such as the diameter and the wall thickness of the spherical joint, and the side length of the steel tube. Experiments on four typical full-scale joints were conducted to understand directly the structural behavior and the collapse mechanism of the joint, and also to validate the finite element model. A simplified theoretical solution is also derived for the loading-carrying capacity of the joint based on the punching shear failure model, and the basic form for the design equation is obtained. Finally, by utilizing the results from the simplified theoretical solution, finite element analysis and experimental study, the practical calculation method is established for the load-carrying capacity of the joints subject to axial forces, bending moments and the combined loading. For the latter case, the concept of influence coefficient considering the action of bending moment on axial force bearing capacity, or vice versa, and the calculation formula are given as well. The results from this study can be applied for direct design, and also provide a reference for the revision of relevant design codes.
Aluminum alloy structures are widely used in the world due to their special advantages, and more than 10 large aluminum alloy space structures have been constructed in China up to now. This paper provides a state-of-the-art review report-on research on aluminum alloy structures related to material property, basic structural members, connection behaviors and structural system. In generally, the research work on aluminum alloy structures in many developed countries is relatively matured, especially for different basic structural members. While in China, such studies on aluminum alloy structures are being carried out more and more widely and deeply recently, most of which are focused on axially-compressed members, and no reliability analysis for aluminum alloy structures is conducted, mainly due to the lack of experiment data for statistic analysis. Therefore, it is very necessary to establish an experimental database for domestic aluminum alloy structures as a basic step to reliability analysis.
Socket joint systems are typical semi-rigid joints used in space structures. This paper presents numerical analyses of semi-rigid joint systems in which the bolts are pretensioned. Eleven numerical models of socket joints are studied: three of them are subjected to bending and the others are subjected to proportional bending and axial compression. Moment–rotation relationships of the joints are obtained using models in which the material and geometric nonlinearity are taken into account. The load-carrying mechanism of socket joint system is investigated in detail through the numerical analysis. Through comparison of the finite element analysis (FEA) and corresponding test measurements, it is shown that the proposed FEA models can be used effectively to describe the mechanical performance of the semi-rigid joints in spatial structures, including the initial bending stiffness, ultimate bending moment, deformation and the failure mode.
This paper presents the failure pattern, ultimate static strength and detailed behavior of un-stiffened T and Y tubular joints under axial brace compressive loading using finite element method performed by ABAQUS software package. Properties of the un-stiffened tubular joints were extracted from the available experimental-based tubular joint database. Utilizing the Modified Riks Method in numerical analyses led to an accurate simulation of joint behavior and also helped to investigate its correct failure pattern. The modes of failure observed throughout the numerical analysis were local bending of the chord member, ovalization and plastic failure of the chord. The results obtained from the numerical modeling revealed the critical areas on the joint surface with respect to ovalization, deflections and stresses. Also, the ultimate strength predicted by the numerical analysis was compared and validated with available experiment results. Despite the fact that much research has been conducted on tubular joints which have mostly focused on the estimation of ultimate strength or stress concentration factors rather than detail study of joint behavior, the present detail investigation has provided a thorough understanding of joint behavior under axial compressive loads. Such an in-depth and detail tubular joint investigation has been rarely reported in the open literature.
Socket joints and bolt-ball joints are typical semi-rigid joint systems widely used in spatial structures. In this paper, tests on fifteen joints are carried out to study their mechanical behavior. Three socket joint systems are subjected to bending moment and shear force, and another seven socket joint systems and five bolt-ball joint systems are subjected to bending moment, shear force and axial compressive force. The main characteristics of the moment–rotation relationship for the connections under different loading schemes are summarized and discussed. The results indicate that: (i) both socket and bolt-ball joint systems have good bending stiffness; (ii) the axial compressive force increases the initial bending stiffness of the joints; (iii) the axial compressive force has different effects on the bending moment capacity of different joints; and (iv) the yield process of moment–rotation curves of the joints is shortened due to the action of the axial compressive force.
Geometric non-linearities in single-layer domes can cause the loss of global stability, which is strongly influenced by both geometric parameters and joint rigidity. The rigidity of the joint requires deeper study, since it significantly affects the behaviour of these structures. To this end, a model is proposed for the ORTZ joint. The model is established from the dimensions and properties of the different elements of which the joint is composed and considers the possibility of the material reaching its yield point. After experimental verification, the model is implemented in a computer application. Finally, experimental tests have been conducted on two structures possessing very different features related to geometry and rigidity of joints. In both cases the proposed model has given a good estimation of the experimentally observed behaviour of the structures.
This paper presents numerical results on the ultimate strength behaviour in terms of load–displacement characteristics and failure mechanisms of completely overlapped tubular joints. The effect of the gap length on the behaviour of the joints is also investigated. In the study, the end of the lap brace was axially loaded. Criteria were set up to determine the minimum failure load. It was found that a joint subjected to compression load gave the lowest ultimate capacity. The geometric parameters of the chord were shown to have an insignificant impact on the joint behaviour. The joint strength increased as the gap reduced. A sharp increase in the joint strength at small gap was noted for a relatively high βTL(=dL/dT=0.768). The Y-joint capacity was reached at a sufficiently large gap. τTL(=tL/tT) had a crucial influence on the joint failure behaviour. A relatively mild βTL(=dL/dT=0.616) and τTL(=tL/tT=0.560) resulted in lap brace failure prior to joint collapse. The failure mechanisms changed from “chord” (through brace) bending, followed by localised plastification of the through brace face to yielding of the lap brace when the gap was reduced from a large gap to a small gap of 51 mm.