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A systematic study into the behavior of reinforced semi-rigid piles in response to lateral monotonic and cyclic loading in clay was performed with centrifuge modeling tests (100×g). The aim was to investigate the pile–soil interaction mechanism of reinforced semi-rigid piles and to give some generally applicable design advice for reinforcing semi-rigid piles with cement-improved soil. For monotonic loading, the overall load–deflection behavior, profile of bending moment, net soil pressure and pile deflection have been fully studied, in addition to the p–y curves and excess pore pressure response of reinforced and unreinforced piles. It is found that shallow cement-improved soil reinforcement can greatly improve the lateral capacity of piles. In addition, a hyperbolic tangent model was proposed to fit the p–y curves obtained from monotonic tests for reinforced and unreinforced piles. For cyclic loading, it was found that compared with unreinforced piles, reinforced semi-rigid piles reduce the accumulation of pile deflection and the degradation of stiffness. The trends of the cyclic bending moment and cyclic p–y curves are also revealed. A series of supplementary finite element analyses were conducted to study the effects of reinforcement parameters (reinforced width, reinforced depth and strength of cement-improved soil) on lateral pile capacity. It is suggested that shallow reinforcement with a reinforced width of 5D and a reinforced depth above the rotation point of a semi-rigid pile is both economical and practical. [ABSTRACT FROM AUTHOR]

Assembled T-shaped aluminum alloy components represent a new type of structural member in aluminum alloy structures with broad application prospects. In this study, axial compression tests were carried out on 32 aluminum alloy components, considering parameters such as the cross-sectional type and slenderness ratio of the components, to obtain the ultimate bearing capacity and failure mode of the members. The test results show that, for the equilateral assembled T-shaped aluminum alloy components with obvious strong and weak axes, bending instability was most common, and local buckling of the plate occurred when the slenderness ratio of the component was relatively small. For the unequal T-shaped aluminum alloy structures without an obvious strong or weak axis, torsional buckling instability occurred, accompanied by local deformation of the connecting limbs due to mutual compression. A verified finite element model was also established. Based on this model, a parametric analysis was conducted to study the influence of parameters such as initial defects, slenderness ratio, and cross-sectional type on the axial compressive bearing capacity of the assembled T-shaped aluminum alloy components. The experimental and numerical results were then compared with Chinese and European standards, revealing that the standard calculation methods tend to be unsafe. Finally, the calculation parameters for component defects in Chinese and European standards were revised. [ABSTRACT FROM AUTHOR]

To date, scholars' research on the stability behavior of the arch structure mainly focuses on solid–web section arches, steel tubular truss arches and concrete-filled steel tubular arches, but the stability behavior of the novel spatial grid arch structure, which integrates the characteristics of grid structure and arch structure, is not yet clear. Based on the Eye of the Yellow Sea pedestrian bridge project in Rizhao, China, the stability behavior of this large-span spatial grid arch structure was studied, in this paper, by the project's structure design team. The project is a glass covered steel arch pedestrian bridge with a span of 177 m, a height of 63.5 m, an elliptical section with a long axis of 18 m, and a short axis of 13.5 m. The elastic and the nonlinear elasto-plastic stability behavior considering different initial geometric imperfections, was analyzed by the ABAQUS finite element model. The buckling modes and the full-range load-displacement curve of the structure were analyzed, and the stress distribution, deformation mode and overall structural performance during the whole loading process were analyzed. The effects of initial imperfections, geometric nonlinearity and material nonlinearity on the ultimate load-carrying capacity of the structure were studied. The stability behavior of large-span spatial grid arch structure was studied in this paper, which provides an important reference for the design and analysis of such structures. [ABSTRACT FROM AUTHOR]

The crude oil in pipelines should remain at high temperature and pressure to satisfy the fluidity requirement of deep-sea oil transportation and consequently lead to the global buckling of pipelines. Uncontrolled global buckling is accompanied by pipeline damage and oil leakage; therefore, active buckling control of pipelines is needed. Pipe-in-pipe (PIP) systems have been widely used in deep-sea oil pipelines because of the protection and insulation characteristics of the outer pipe to the inner pipe. In this study, sleeper-distributed buoyancy is used as an active buckling control method for the global buckling of PIP systems with initial imperfections. The accuracy of this technique is verified by comparing the finite element model of a 3D pipeline with experimental data. The effects of buoyancy density, pipe–soil friction coefficient, initial imperfection, stiffness ratio of inner and outer pipes, and buoyancy unit interval on the global buckling performance are also analyzed. The critical buckling force and lateral displacement of this method are studied using an analytic solution, and the relevant calculation formulas are obtained and verified to provide a basis for its engineering application. [ABSTRACT FROM AUTHOR]

Accurate assessment of the damage to a structure is the key to structural health monitoring. Among them, one effective means to assess the real-time status of the structure is by establishing a finite element model (FEM) of the structure and updating it synchronously. Previous research mainly updates the FEM of the structure with a certain moment in time without considering the continuous changes of structural parameters over a longer time. In this paper, we propose a FEM updating method for steel truss structure based on knowledge-enhanced deep reinforcement learning, which introduces long short-term memory (LSTM) network based on a deep deterministic policy gradient (DDPG) algorithm and constructs a knowledge-enhanced noise function (NF) module based on parametric analysis. The NF-LSTM-DDPG algorithm can fit a continuous variation of structural parameters. The ablation experiments revealed that the LSTM network and the NF module facilitate the exploration and learning ability of the DDPG algorithm. The NF-LSTM-DDPG algorithm is used in an actual steel truss structure case, and the variation rules of the elastic modulus and support deviations obtained from the solution are consistent with the actual situation. The average relative error of the 34 strain measurement points after updating is 14.147 %, and the relative error is higher than 20 % in only 13 days out of 187 days of continuous monitoring. Five days were selected for the comparative study, and the experimental results show that the relative error of the NF-LSTM-DDPG algorithm is 13.206 %, which is higher than that of the particle swarm optimization algorithm and the simulated annealing algorithm. The change of elastic modulus updated based on the NF-LSTM-DDPG algorithm is more reasonable than other algorithms. • Reinforcement learning model can fit the continuous variation of structural parameters in the finite element model. • Improved deep deterministic policy gradient algorithm by introducing long short-term memory and noise function module. • Constructing knowledge-enhanced noise function modules based on parameter correlations. • The NF-LSTM-DDPG algorithm is better than the particle swarm optimization algorithm and simulated annealing algorithm in terms of accuracy and stability. [ABSTRACT FROM AUTHOR]

Fire disaster-induced collapse rarely occurs for space grid structures because of their high redundancy and their fire protection design. Consequently, with reasonable evaluation and repair, most space grid structures after fire can still be used. The post-fire axial compression properties of welded hollow spherical joints, which have been commonly used in space grid structures, were studied through experimental and numerical analyses. Then, the influence of factors such as material mechanical properties, loading condition and plastic residual deformation on the post-fire mechanical properties were analyzed. A calculation formula was presented to evaluate the post-fire bearing capacity of welded hollow spherical joints. • Test on pre-damaged welded hollow spherical joints after exposure to fire. • Residual mechanical behavior and failure mode were obtained. • Finite element analysis was developed to study the post-fire residual behavior. • Mechanical behavior significantly changed with increasing exposure temperature and residual deformation. • Calculation methods were proposed to estimate residual bearing capacity. [ABSTRACT FROM AUTHOR]

Surface electric field (SEF) strength plays an important role in studying corona discharge and is widely utilized in the research of corona loss and ion flow field in transmission line projects. The electrical field invariant theory after corona occurs is widely adopted to describe the SEF, but it is not consistent with the actual corona discharge situation. Thus, how to accurately evaluate the change of SEF is crucial for the design of overhead lines. Space charge caused by corona around the wire surface is closely related to the SEF; therefore, it is feasible to use the space charge to characterize SEF. In this work, a system for space charge density measurement is established in the laboratory to analyze the distribution of space charge under different voltages and temperatures. The validity of the experimental results was verified by finite element method (FEM), and the maximum charge density ratio is proposed to correct the variation formula of SEF. The experimental results show that SEF is not equal to the onset field intensity, and displays a decreasing trend after corona initiates, which can be used to rectify the electrical field invariant theory. [ABSTRACT FROM AUTHOR]

In aluminum alloy reticulated shell structures with gusset joints, the roof panel is effectively connected with the structural members through a clamp connection, enabling the roof panels to participate in the force resisting system. The performance of the connection between the roof panels and the members is the foundation for studying the collaborative action of the roof panels and the members. Relevant studies have shown that when the roof panels participate in the force resisting system, there is mainly a tensile force in the roof panels perpendicular to the axis of the members. Therefore, this paper experimentally studied the mechanical performance of the clamp connection between the roof panels and the members under the tensile force in the roof panels, and employed two-dimensional plane digital image correlation (DIC) to measure the deformation of the specimen section during the entire loading process, thus exploring the force transmission mechanism of the connection. The tensile capacity of the connection can be divided into four stages: roof panel sliding, roof panel tension–shear, lower limb bending of the strip, and roof panel bending stages. The mechanical index of the connection is primarily determined by the tension–shear stage of the roof panel, and the ultimate strength and stiffness can be determined as the peak load and linear segment stiffness of the connection at this stage. The refined finite element model was further established, and it was verified that the model could efficiently simulate the mechanical properties of the connection through comparison with the test. Parametric analysis shows that with an increase in the friction coefficient between materials, roof panel thickness, angle between roof panel and flange, and bolt length adjustment, the restraint on the roof panel increases, and the failure mode of the clamp connection changes. Based on the parametric analysis, the recommended values of the friction coefficient between the materials, minimum panel thickness, minimum bolt screw depth, and maximum bolt spacing are provided. Finally, combined with the theoretical analysis, calculation formulas for the tensile strength and stiffness of the connection were proposed. A comparison with the test results indicates that the prediction accuracy of the formula proposed in this study is good. • The force transfer mechanism of aluminum alloy roof panel-member coupler connection under tensile force is obtained. • A high accuracy refined finite element model of aluminum alloy roof panel-member coupler connection is established. • Suggestions on design of aluminum alloy roof panel-member coupler connection are given. • Calculation formulas for the ultimate bearing capacity and stiffness of the connection were proposed. [ABSTRACT FROM AUTHOR]

Welded hollow spherical joint is an extremely widely used connection pattern in space lattice structures. Understanding the behavior of the welded hollow spherical joint after elevated-temperature exposure is critical for the fire damage assessment of the entire space lattice structures. In this study, both experimental and numerical studies were conducted to reveal the mechanical behavior of eccentrically loaded welded hollow spherical joints subjected to eccentric loads after cooling from three elevated temperatures up to 1000°C, wherein two different methods were considered, namely, air and water cooling. Associate mechanical performance, such as load versus longitudinal displacement and load versus steel tube rotation responses, initial stiffness, load-bearing capacities, and strain development, were obtained and further analyzed. The results showed that the behavior of welded hollow spherical joints began to change when the exposure temperatures exceeded 600°C, with obvious reductions in both stiffness and strength. In addition, the influences of different cooling methods were significant. The joints cooled by water generally presented higher load-bearing capacities than those cooled by air. Furthermore, three-dimensional finite element analysis was conducted via ABAQUS software. After validating the finite element model against experimental results, parametric studies were performed and a practical formula was proposed to calculate the load-bearing capacity of welded hollow spherical joints subjected to eccentric load after elevated-temperature exposure. [ABSTRACT FROM AUTHOR]

Bar-plate configuration has a vital function in the intensive study of corona discharge mechanism. To study the discharge characteristics of the steady current stage in this configuration, this paper proposes a hybrid numerical algorithm composed by the finite-element method and the finite-volume method. The former solves Poisson’s equation and calculates the value of onset field intensity. The latter solves the current continuity equation, in which a time-varying charge item is added. This charge item can increase the stability of the hybrid algorithm. This paper also proposes a new selection strategy for the initial charge and inception voltage on the bar electrode surface. Based on this algorithm, corona current under different electrode radii, gap distances, and applied voltages was calculated. In this way, the distribution characteristics of an electric field intensity and space charge density along the whole gap in the model can be obtained through the experiment. To verify the validity of the algorithm, the related experiment is carried out in the laboratory. The simulation results have a good consistency with the experimental results, verifying the validity of the algorithm proposed in this paper. [ABSTRACT FROM AUTHOR]

Space charge distribution is a valuable indicator of ion flow field and is widely utilized to assess electromagnetic environment for transmission line. The finite-element method (FEM) is widely used to solve this problem. However, Kaptzov assumption in FEM assumes that onset voltage is unchangeable after corona occurs, which does not tally with the actual situation. This paper adopted the finite-element iteration method (FEIM), which uses empirical formula instead of assumptions to calculate the charge density. The surface field intensity is not constant in the empirical formula because the empirical formula takes the effects of space charge on surface field into consideration. So this is more consistent with actual situation. In order to verify the accuracy of the algorithm, sound pulse method is applied to measure the charge density around the conductor in the laboratory. Simulation results show that the charge density obtained in this paper agrees with the data in the experiment, which verifies the validity of the empirical formula for calculation of space charge density. Compared with a method considering Kaptzov assumption, FEIM is closer to the experiment in area around conductor line and near the ground. This indicates that empirical formula in FEIM is more effective than Kaptzov assumption in these two domains. [ABSTRACT FROM AUTHOR]

The application of aluminium alloy space structures is increasingly widespread. There is a new single-layer aluminium alloy spatial grid structure with H-shaped members web openings nowadays. In this paper, the flexural performance of H-shaped aluminium alloy members with web openings in this structure is studied through experiments, finite element analysis and theory. Parametric analysis is carried out to study the influence of initial imperfections, opening parameters and section properties on the flexural performance of the members. The conclusions are as follows: (1) The presence of initial imperfections can significantly reduce the ultimate load-carrying capacity of the component. The initial imperfection reduced the member capacity by 6.3% to 12.7%. (2)The web openings will affect the failure mode of flexural members with H-shaped web openings. When the opening ratio is 0.7, the bearing capacity of the test specimen decreases by 31.2%–47.1%. The local buckling of the flange and web occurs at the same time as the failure of the vierendeel mechanism. (3) The bearing capacity of narrow flange members can be reduced by 2.3 times as much as that of wide flange members. The greater the section width to height ratio, the greater the ultimate bearing capacity of the member. (4) The finite element method and theoretical formula proposed in this paper can better simulate the bearing capacity and failure mode of H-shaped aluminium alloy members with web openings under bending. • Flexural performance of H-shaped aluminium alloy members with web openings. • Numerical studies on the flexural performance of H-shaped aluminium alloy members with web openings. • Related parameters affect the bearing capacity of H-shaped aluminium alloy members with web openings. • The calculation method for bearing capacity of H-shaped aluminium alloy members with web openings. [ABSTRACT FROM AUTHOR]

• Glulam spliced joint connected by steel strips and self-tapping screws was proposed. • The feasibility of the three-dimensional finite element model was verified. • Theoretical analysis was provided to estimate the stiffness and ultimate moment. A glulam spliced joint connected with self-tapping screws and prestressed steel strips was proposed and investigated. An experimental study was conducted considering the variation in the arrangement of the self-tapping screws and steel strips. The specimen with an inclination of 60° screws exhibited the highest ultimate load, whereas the specimen with screws in the X-position with the inclination of 60° had the highest ductility. Finite element analysis was performed and verified to be effective in simulating the mechanical behavior of the proposed joint. Moreover, the proposed theoretical model exhibited a high accuracy when predicting the bearing capacity and stiffness. [ABSTRACT FROM AUTHOR]

• Combining DT and hierarchical DL to realize intelligent identification of structural damage. • Study an establishment method of high-fidelity digital twin model based on offline data and online data-driven. • Develop a program for automatic establishing damage database of cable dome structure. • Propose a DL framework which can identify the damage type, location and degree with high accuracy. • The approach can provide a new basis for structural damage identification with broad application prospects. Accurate identification of structural damage is the most critical step in structural health monitoring. Traditional damage identification strategies are easily interfered by environmental and human factors, resulting in low-accuracy of identification. In this light, a combined digital twin (DT) and hierarchical deep learning (DL) approach for intelligent damage identification in cable dome structures is proposed in this paper. Based on actual engineering cases, a DT model that accurately maps the physical structure of the cable dome is constructed using APDL based on data. A cable dome structure damage sample database is then automatically established through the large-scale finite element analysis of DT. Finally, the damage features of the data samples are extracted using the hierarchical DL framework proposed in this study. Accuracy verification based on cable force confirms that the established DT model can accurately reflect the mechanical state of the physical structure. The identification results of the trained network on a test set demonstrate that the proposed framework can intelligently identify the damage type, damage location, and damage degree in the cable dome structure with a high accuracy and strong robustness. The proposed intelligent damage identification approach is feasible and reliable and can provide a new basis for structural damage identification with broad application prospects. [ABSTRACT FROM AUTHOR]

• The behavior of glulam bolted joints with prestressed steel strips was studied. • Numerical models considering compressive and tensile crack were created. • The theory of elastic foundation with fictious piles was introduced. The glulam bolted joint with prestressed steel strips was proposed and investigated systematically. Experimental study was conducted considering the variation of pre-strain of steel strips. The presence of prestressed steel strips led to a delay in the onset and propagation of cracking with a pronounced increase in bearing capacity compared with ordinary glulam bolted joints, i.e. by 41.15%, 52.01% and 53.33%, respectively, and significantly higher deformation capacity, with the ductility increasing by 15.38%, 88.11% and 104.90% respectively. A three-dimensional finite element analysis considering mixed-mode cohesive zone modeling was performed and verified to be effective to reproduce crack path observed in the experiments. Moreover, a quasi-non-linear fracture mechanics model based on a Timoshenko beam on elastic foundation theory was extended in order to take into account the influence of the prestressed steel strips on the ultimate bearing capacity. Analytical results demonstrated how ultimate bearing capacity changed with pre-strain, thickness, width and spacing of strips and a series of design recommendations were supplied. [ABSTRACT FROM AUTHOR]

This paper presents a systematic experimental and analytical study on the stability behavior of steel tube–coupler scaffolds (STCSs), wherein upper horizontal tubes transfer construction loads. Four specimens with common geometric sizes were constructed and tested statically in the lab to obtain the strength and failure modes. Advanced nonlinear finite element analysis, which considers the initial member imperfection and semi-rigid behavior of right-angle couplers, was conducted on the specimen models by using ANSYS to obtain the stress distribution, strength, and failure modes of the STCS. Analysis results were compared with the experimental results. The following can be concluded from the experimental and analytical results. (1) The main failure mode of the STCSs is the local instability of a vertical steel tube if the upper layer joints have sufficient anti-slipping capacity. Otherwise, the main failure mode is the slipping and fracture of right-angle couplers. (2) The strength of STCSs is sensitive to upper joint type. The load capacity of ST2 with the strengthened joint is 1.30 times that of ST1 with a common joint, and the load capacity of ST4 with a common joint is 1.16 times that of ST3 with a weak joint. (3) The numerical simulation method presented in this paper is generally consistent with the full-scale test results and has a maximum difference of 11.08%. [ABSTRACT FROM AUTHOR]

• Compressive performance of H-shaped aluminum alloy members with web openings. • Numerical studies on the compressive performance of H-shaped aluminum alloy members with web openings. • Web opening parameters affect the bearing capacity of H-shaped aluminum alloy members with web openings. • The calculation method for bearing capacity of H-shaped aluminum alloy members with web openings. In this study, experimental, numerical, and theoretical approaches are adopted to comprehensively investigate the compressive bearing capacity and failure modes of H-shaped aluminium alloy members with web openings. The influence of the opening parameters, section size, and slenderness ratio on the bearing capacity of such alloy members is analysed, and a calculation method is presented. Finite element models are established in Abaqus with the same configurations as the test specimens. The following conclusions are drawn from the analysis results: 1) The web openings weaken the practical section and destroy its continuity. Moreover, they affect the force flow transmission, thereby reducing the bearing capacity of the component and changing its failure mode. 2) Web openings have significantly larger impact on members with smaller slenderness ratios. The failure modes of members with different slenderness ratios are therefore different. 3) When the slenderness ratio is approximately 60, the weakening of the load displacement along the strong axis due to the web openings is significantly higher than that along the weak axis. 4) When the opening ratio exceeds 0.7, the openings greatly affect the stability of the components. In contrast, when the opening ratio is less than 0.3, the openings have negligible impact on the component stability. The numerical and theoretical analysis results are compared and verified by the experimental results. [ABSTRACT FROM AUTHOR]

This study proposed a reinforced connection with an outer annular stiffener for square hollow section (SHS) columns and H–beams. Low-cyclic-load tests were designed for three strengthening specimens and one common specimen. The verified finite element model was used to study the impact of the welding thermal effect, axial compression ratio, and vertical stiffener size on the seismic performance of joints. The results showed that joints reinforced with an outer annular stiffener for SHS columns and H–beams can effectively transfer loads. Compared to common joints, their moment resistance increased by 75%–113%, the energy dissipation coefficient increased by 5.5%–20.4%, and the moment resistance of the strengthened joints was significantly different in the positive and negative directions. In the process of welding strengthening, the influence of the welding thermal effect can be ignored. When the axial compression ratio was greater than 0.7, the moment resistance decreased by more than 14%. The strengthening was optimal when the vertical stiffener thickness was not less than 40% of the column wall thickness or 6 mm, the enlarged flange connection plate was completely wrapped, and the lap length was within 10–20 mm of the upper and lower steel angles [Display omitted] • Low-cyclic-load tests were carried out on a reinforced connection under load. • The reinforced connection of the SHS column and H–beam can transfer the load. • An indirect thermal–structural coupling method was applied. • Corresponding design suggestions of vertical rib dimensions were proposed. [ABSTRACT FROM AUTHOR]

In this paper two cable force determination methods were proposed based on the principle of direct determination, respectively based on using steel pipe ring crushing or strand tapered anchorage to connect cable. Experimental investigation was conducted to test the two force measurement devices; the results indicated that the two cable force measurement devices could effectively transfer the cable's internal force, while the first one (with steel pipe ring crushing) could not stably connect the cable. After calculating and analyzing the reasonable core structure size of the second device by the finite element analysis software, the structural practice of such devices were provided. The proposed cable force determination method using the strand tapered anchorage owns simple operation, low cost and high accuracy, which can provide a reference for similar tests and practical engineering. [ABSTRACT FROM AUTHOR]

Abstract: In regards to the defect of respectively handling three conditions, this paper puts forward a new unified expression fitting for different boundary conditions. It also obtains the parameter values of expression in different boundary conditions. Take the infinite square cylinder putting into cold liquor as an example, it works out a program using the improved new boundary treatment to simulate cylinder temperature field. This paper gets distributions of temperature field at four different times. The results of simulation not only meet the physical situation, but also have high precision compared with the theoretical solutions. Since being easy to deal with complex boundary conditions, the new way makes the FEM useful again in engineering calculation and research. [Copyright &y& Elsevier]

Abstract: Systematic experimental and analytical studies are presented in this paper on the stability of structural steel tubes and coupler scaffolds without X-bracing (hereinafter referred to as STCS). Twelve full-scale STCS specimens with various geometric properties were constructed and tested statically in the lab, in order to obtain the strength as well as the failure modes of typical STCS’s. Advanced nonlinear finite element analysis was conducted on the specimen models using the ANSYS program, in order to obtain the strength and failure modes of the STCS’s and to compare with experimental results. Parametric studies were carried out based on the FEA results, in order to investigate the influence of various geometric properties on the stability behavior of STCS’s. Based on both the experimental and the analytical results, it can be concluded that the typical failure mode of STCS’s is global buckling about the weak axis. The strength was found to be sensitive to the rotational stiffness of the coupler, the storey height, and the U-head height, but insensitive to the post spacing and the sweeping staff height. Furthermore, a simplified model and formula were established for the strength of STCS’s under uniform load and presented in the paper, which were verified by the experimental and analytical results and which turned out to be accurate enough in predicting the strength. In the end, recommendations are proposed for the design of STCS’s based on the research results, which provides a very useful reference for the industry as well as academia for design and future research. [Copyright &y& Elsevier]

The full-lock coil cable clamp node is an important joint in cable structures, and its sliding will reduce the bearing capacity and stability of the structure. Based on cable clamp node slide resistance tests and finite element analyses, the bolt pre-tightening force, cable tensioning sequence, and parameters such as the cable diameter were investigated to determine their influence on the cable clamp slide resistance. The stress distribution and variation in cable in the process of cable clamp sliding with steel wire was obtained. The main conclusions are as follows. (1) The bolt fastening force is basically proportional to the ultimate anti-slide bearing capacity of the cable clamp. The reduction coefficients for an 80 mm cable with initial fastening forces of 125 kN, 175 kN, and 225 kN are 0.49, 0.56, and 0.61, respectively. (2) Tensioning the cable first and then tightening the bolt can effectively improve the ultimate anti sliding bearing capacity of the cable clamp. The ultimate anti sliding bearing capacity of the cable clamp tested in this paper is increased by 38%. (3) Under the condition of the same initial fastening force, with increasing cable diameter, the sliding bearing capacity decreases linearly. (4) During cable clamp sliding, the stress of the cable in the slide direction of the cable clamp decreases, while the stress of the cable on the other side increases. (5) A calculation equation for the slide resistance ultimate bearing capacity of full-lock coil cable clamps considering the cable diameter and cable clamp length is obtained. [Display omitted] • The anti-sliding tests of the cable clamp joint was carried out, and the tightening force loss of bolts was monitored. • The refined model of the cable clamp joint with full-lock coil cable is established. • The effects of cable diameter and cable clamp length on the anti-sliding properties were studied. • The calculation formula of fastening force loss of high-strength bolt is presented. • The formula of anti-sliding ultimate bearing capacity of cable clamp was obtained. [ABSTRACT FROM AUTHOR]

Thermal effect and preload are significant factors affecting the mechanical properties of strengthened members in engineering structures. This study concerns the welding thermal effect and mechanical properties of circular steel tubes strengthened by welding angle steel under the preloading condition. The mechanical properties of circular steel tubes strengthened by welding angle steel under the preloading condition were studied with the axial compression tests. The indirect thermal-structural coupling method was proposed and verified by finite element analysis, further compared with the tests. At last, a series of parametric studies were conducted to investigate the influence of loaded strengthening on mechanical properties of circular steel tubes strengthened by welding angle steel under the preloading condition. The corresponding permissible stress ratio and calculation method for the ultimate earing capacity and the axial thermal deformation were proposed. The results provide a basis for the strengthening design of the circular steel tube under the preloading condition. [Display omitted] • Axial compression tests for circular steel tubes strengthened by welding angle steel under preloading condition. • Corresponding FEA with proposed indirect thermal-structural coupling method. • Corresponding parametric studies for influence of loaded strengthening. • Corresponding permissible stress ratio and calculation method for ultimate bearing capacity and axial thermal deformation. [ABSTRACT FROM AUTHOR]

Space frames are mostly steel structures whose material and mechanical properties are largely affected by the high temperature of fire such that the bearing capacity of the structure deteriorates. Welded hollow spherical joints, as the most widely used form of joints in space frames, are the key factors affecting structural stress. Thus, the resistance to fire of such joints must be further studied. In this paper, the mechanical properties of welded hollow spherical joints (abbreviated WHSJ) with H-beam under elevated temperature are investigated through experiment and finite element analysis. Axial compression tests at 300 °C, 500 °C, and 700 °C are used to analyze the failure modes of the joints under axial compression at high temperatures. The experiments obtained load–displacement curves, yield and ultimate bearing capacities, ductility, and initial axial stiffness. Furthermore, results are used to validate the finite element model. Through parametric analysis of temperature, steel grade, ribbed or non-ribbed, diameter, wall thickness, and H-beam section, the present study proposes formulas for designing joints with ultimate bearing capacity and initial axial stiffness to withstand high temperatures. • Test on welded hollow spherical joints with H-beams under high temperature. • Axial compressive mechanical behavior and failure mode were obtained. • Finite element analysis was presented and verified by test data. • The parametric analysis of welded hollow spherical joints at high temperature is conducted. • The formulas were proposed to calculate axial bearing capacity and initial axial stiffness under high temperature. [ABSTRACT FROM AUTHOR]

• H-beam welded hollow sphere developed buckling failure subjected to eccentric compression. • The design formula of H-beam welded hollow sphere subjected to eccentric compression was proposed. • The test results verified the rationality of the proposed formula. • The bearing capacity of joints is greatly affected by ribbing, H-beam height, flange width, and hollow sphere size. • The axial force–bending moment relationship curve of the joint is independent of its geometric size. An H-beam welded hollow spherical joint is a new kind of spatial grid structure. In this study, the eccentric-loaded behavior of H-beam welded hollow spherical joints was studied, and the influential law of material strength, joint size, and stiffening rib on its mechanical properties was analyzed through experimental research and numerical simulation. Parametric analyses were conducted to study the eccentric-loaded behavior of H-beam welded hollow spherical joints subjected to pure bending or the combined action of axial force and bending moment using a finite element model verified through experiments. The calculation formula of the bending bearing capacity of the joints and the axial force-bending moment curve were also obtained. Finally, the design rule for eccentric compression was proposed and verified through test results. [ABSTRACT FROM AUTHOR]

Rectangular concrete-filled steel tube (CFT) columns are widely used in buildings due to their high bearing capacity and convenient joint construction. The CFT columns with high-strength materials can significantly reduce the cross-sectional dimensions and the dead weight. To investigate the fire resistance of rectangular high-strength CFT columns in real structures, the test was carried out on two columns restrained by a full-scale steel frame. The time course curves of the CFT under fire for cross-section temperature, axial displacement at the top of the column, and axial stress were analyzed. The failure modes, fire resistance limits, and heat conduction processes of boundary-restrained CFT under elevated temperatures are clarified. The effect of thick fireproofing coating thickness on the fire resistance of CFT is revealed. Besides, the sequential thermal coupling model for fire resistance analysis of rectangular high-strength CFT was established using finite element analysis. The axial restraint stiffness ratio and rotational restraint stiffness ratio are introduced to quantitatively evaluate the end restraint action of the column. Finally, the experimental data demonstrated the accuracy of the temperature field model and high-temperature test model. The test and finite element analysis of rectangular high-strength CFT with frame restraint reveals the real fire resistance of columns in the structure. • Behaviors of restrained rectangular high-strength CFT column under elevated temperature. • The effect of thick fireproofing coating on the fire resistance of high-strength CFT is revealed. • The sequential thermal coupling model for fire resistance analysis of specimens was established. • The axial and rotational restraint stiffness ratio is introduced to describe the end restraint. [ABSTRACT FROM AUTHOR]

• The behavior of glulam spliced joints with self-tapping screws was studied. • Numerical models considering crack propagation were created. • The theoretical equation was established based on fracture mechanics. Tests were conducted to determine the flexural bearing capacities of glulam spliced joints connected by self-tapping screws (STSs) in five different configurations. The flexural performances and failure modes of these joints were analyzed and an extended finite element method was utilized to establish numerical models of the STS-connected glulam spliced joints while considering crack propagation. The simulation results were in excellent agreement with the test. Moreover, theoretical formulas for the flexural bearing capacity and a flexural stiffness model of STS-connected glulam spliced joints were developed. The research findings indicated that the vertical STSs were more effective in enhancing the bending capacity of the joints than the angled STSs in the vertical plane. Specifically, when using full 90° STSs, the bending capacity increased by 35.57% compared to when using full 60° STSs. The elastic rotational stiffness values of the joints were also improved by using a mixed-angle arrangement of STSs. Specifically, when utilizing a mixed arrangement of 90° and 60°, the elastic stiffness values increased by 33.44% and 63.20% compared to when using full 90° and full 60°, respectively. However, while using STSs in the horizontal plane at the vertical gap significantly enhanced the flexural bearing capacities of the spliced joints, it also led to a significant reduction in the ductility of the joints. [ABSTRACT FROM AUTHOR]

Two simplified models, including a theoretical approach and a finite element method (FEM) model, are proposed to calculate recovery length and study the force redistribution mechanism in a semi-parallel wire cable with broken wires. In the advanced theoretical model, the symmetrical construction and extrusion stress transfer characteristic of the semi-parallel wire cable are considered. The clench effect of the polyethylene sheath and the prestressed helical wire are considered in the derivation. The simplified FEM model can exhibit mechanical performance at both wire and cable levels. It uses helically placed beam elements to simulate twisted wires, divergently arranged rigid beam elements at the wire cross section to simulate extrusion effect, and nonlinear spring elements to consider the contact and friction between the helical wires. Results show that the recovery length is influenced by the compaction effect of wrapped sheath, as well as the twist angle and position of the broken wire. Under the symmetrical break condition, the recovery lengths calculated using the two methods are in a good agreement with each other, and force redistribution mainly results from the friction effect. Under the asymmetrical break condition, however, force redistribution is dominated by the induced unbalanced moment. [ABSTRACT FROM AUTHOR]

• A new ultra-strong thin-walled steel tube and coupler scaffold is developed. • Six full-scale UTSTCS specimens were designed and tested. • Parametric analysis was performed based on FEM considering semi-rigid behavior. • A design method to predict the ultimate bearing capacity of UTSTCSs is proposed. In this study, to improve the erection efficiency and reduce the weight of structures, an ultra-strong thin-walled steel tube and coupler scaffold (UTSTCS) is developed and investigated. Notably, the weight of this UTSTCS is ∼60% that of traditional scaffolds. Six ultra-high full-scale UTSTCS specimens are constructed and tested to determine the bearing capacity of the UTSTCS. A finite element model is built considering the initial member imperfection and semi-rigid behavior of right-angle couplers, based on which parametric studies are then conducted to investigate the method for determining the ultimate bearing capacity and influence of various geometric properties on the stability behavior of UTSTCSs. Compared with that of traditional scaffolds, the vertical bearing capacity of UTSTCSs does not decrease appreciably when the weight of the steel tube is reduced by 40%. Under a uniform vertical load, the main failure modes of UTSTCSs are top coupler slipping, top horizontal tube bending, and post bending. The joint type of the upper layer members, story height, and post spacing have evident influences on the bearing capacity. Moreover, the results of the proposed method for predicting the ultimate bearing capacity of UTSTCSs are in good agreement with the numerical simulation and experimental results. [ABSTRACT FROM AUTHOR]

This study proposes a novel strengthened joint with external rib plates for the H-shaped-beam square-column (HBSC) steel frame. The thermal effect of welding under load on the flexural performance of this joint was examined experimentally, numerically, and theoretically, both during and after the welding process. The following significant findings have been reported. The rib plates do not convey the axial pressure when welded to the column wall; consequently, the maximum thermal strain occurs on the column wall below the weld seams, reducing the column's stiffness and negatively contributing to the joint's flexural resistance. While the rib plates transmit force when they are welded to the angle steel, at this time, the rib plates experience the most significant thermal strain. The thermal effects of welding have been evaluated using a finite element model (FEM). Considering thermal effects, the FEM suggests a reduction factor of 0.90 for the load-bearing capacity. The yield strength of the strengthened joint is roughly double that of the unstrengthened joint, indicating that the reinforcement is effective. The initial stress ratio of the column must be kept below 0.7 to limit the rate at which the yield strength of the strengthened joint decreases as the compressive load increases. The stress distribution ratio between the vertical rib and the column wall has been determined using a simplified mechanical model. Based on the yield line principle, a formula for calculating the yield capacity of the strengthened joint has been derived. • The flexural performance of steel beam-square column joints strengthened by external rib plate can be improved. • The bearing capacity of strengthened joints reduces a little when the welding heat is considered. • Before welding, the initial stress ratio of the column must be maintained below 0.7. • The load borne by the vertical rib was greater than that of the column wall. [ABSTRACT FROM AUTHOR]

Upheaval buckling may occur in high-temperature and high-pressure subsea pipe-in-pipe (PIP) systems. Finite element method and dimensional analysis method are used to investigate the upheaval buckling response and critical buckling force of PIP systems with full-contact imperfections. Results show that imperfections, along with clearance (the gap between the centralizer and outer pipe) and stiffness ratio of the inner and outer pipe, influence buckling response and buckling force. Two empirical formulas that correspond to two typical imperfection profiles are proposed to calculate the critical upheaval buckling force of PIP systems on the basis of dimensional analysis and numerical results. The proposed empirical formulas show good accuracy. [ABSTRACT FROM AUTHOR]

To address the deficiencies in traditional communication towers in mobile communication engineering, such as heavy weight, easy corrosion and poor durability, this study proposes replacing traditional communication towers with GFRP communication lattice towers with lightweight, high-strength and good durability. Firstly, GFRP material test and GFRP circle tube bending capacity test are conducted. The maximum bending moment that can be subjected to the anchorage end of GFRP circular tube is 18.20 kN·m. Finite element analysis of GFRP circular tubes verifies the accuracy of the bending test results. Secondly, a GFRP communication lattice tower with a height of 25 m is designed adopting GFRP circular tubes as tower columns. Through the bending test of the GFRP tower, it is verified that the connection between the columns and web members of the GFRP tower is reliable and the force pattern of the GFRP tower is reasonable. The large deflection theory can be adopted to the displacement of GFRP towers accurately. Thirdly, according to the actual engineering requirements, the finite element analysis of 25 m-high GFRP tower under the basic wind pressure of 0.45 kN/m2 is carried out by using 3D3S (a spatial structure design software). It can be obtained that the vibration mode of the GFRP communication tower shows two forms of lateral bending and axial torsion. 0° wind load direction has the greatest influence on the displacement of the GFRP tower. The stress ratio of each component in the GFRP tower is less than 1, indicating that no damage occurs in the GFRP tower. Finally, GFRP towers have good economic benefits, good environmental performance and wide range of application after comparing the GFRP tower and traditional steel tower. The demonstration project of the GFRP communication lattice tower is established in Qingyuan City, Guangdong Province, China. When subjected to a typhoon with a wind speed of 17.26 m/s, The horizontal displacement of the GFRP tower top is 10 m, which is about 2/5 of the height of GFRP tower. Although the displacement is large, the GFRP tower is still not destroyed. It can be concluded from the research in this paper that GFRP towers have low cost, good mechanical properties, good durability, and wide application range, which can promote the rapid construction of 5 G communication base stations. [Display omitted] • The bending moment of the GFRP tube can reach 18.20 kN·m. The finite element analysis match well with bending test. • A 25-m-high GFRP lattice tower is designed. The deformation of GFRP tower can be calculated by large deflection theory. • The vibration mode of the GFRP tower shows two deformation forms: lateral bending and axial torsion around the z-axis. • The GFRP tower has a large displacement but no damage, when subjected wind with the speed of 17.26 m/s. • Applying GFRP tower can effectively improve the construction efficiency of 5 G communication base station. [ABSTRACT FROM AUTHOR]

• On the basis of the experimental study on the global buckling of the sleeper–snake lay PIP system, the effects of different imperfection wavelengths and amplitudes on the global buckling of the PIP system were analyzed. • A numerical analysis model of global buckling was established, and the influences of different parameters on global buckling response were investigated. The accuracy of the numerical model was verified through experiments. • The calculation equation of the global critical horizontal lateral force of this type of PIP system was derived based on the experimental results and then verified. Offshore oil and gas exploration are gradually heading toward the deep sea and even the ultra-deep sea. According, the working temperature and pressure intensity of subsea oil and gas pipelines have increased by a considerable degree. This situation is accompanied by the global buckling problem in deep sea pipelines, which has become increasingly common. Meanwhile, ordinary single-layer pipelines cannot last for a long time under harsh deep-sea working conditions. Thus, multilayer pipelines, such as the pipe-in-pipe (PIP) structure and bundled pipelines, have gradually become top choices. However, the global buckling mechanisms of these multilayer pipelines are more complicated than those of single-layer pipelines. The sleeper–snake lay pipeline, which is an active control method for global buckling, was used in this study. The change and development laws of global buckling in a PIP structure at different wavelengths and amplitudes were determined through an experimental study. A dynamic solution method that considers artificial damping was adopted to establish finite element global buckling models of a PIP structure with initial imperfections. The effects of various factors, such as pipeline laying shape, sleeper–pipe function, and seabed–pipe function, on global buckling were analyzed. By the result of finite element method analysis, the initial imperfection, and sleeper–pipeline friction were determined to be the key factors that influenced critical pipeline buckling force. Accordingly, a reference for the design of PIP structures is presented. [ABSTRACT FROM AUTHOR]

Relaxation test on cable with large diameter is usually difficult and money consuming due to its extremely large ultimate tensile strength. A simplified finite element modeling method for stress relaxation simulation of steel wire, semi-parallel wire strands and spiral strands was proposed. Simplified relationship between stress relaxation and creep of steel wires was derived and a simplified modeling method on spiral wire composition was proposed. The whole numerical approach incorporated the steel wire creep model and the simplified cable compositions to realize the simulation of stress relaxation behavior of structural cables. The effectiveness of proposed creep calibration and cable stress relaxation simulations were verified through relaxation test data of single-wires and 19-wire semi-parallel wire strands. The 19-wire, 37-wire, 61-wire, 91-wire and 127-wire semi-parallel wire strands and spiral strands at different initial stress levels were all simulated. Due to the spiral wire composition and corresponding gradient wire stress distribution under axial tension, relaxation rate of semi-parallel wire strands and spiral strands were all larger than that of single steel wire. Semi-parallel wire strands presented a decreasing relaxation rate with the increase of cable dimension. Spiral strands had larger relaxation rate than similar-sized semi-parallel wire strands, and present a slight relaxation increase trend with cable dimension. The proposed finite element modeling method can realize the stress relaxation analysis of large diameter structural cables, with only stress relaxation test data of single wires or small diameter cables. [ABSTRACT FROM AUTHOR]

Construction simulation for a shell-shaped single-layer lattice shell located in Yujiapu was conducted based on ANSYS finite element software. According to actual construction process and the element birth and death technology, the stress changing tendency of key components was obtained and lifting process was analyzed in detail. The monitoring scheme was made and conducted to ensure the safety in erection process for the boxed components which were subjected to large axial force, shear force, moment and torsion at the same time. The results derived by monitoring and simulation were compared. The changing course of bearing displacement was calculated by using nonlinear spring element to accurately simulate mechanical property of double bearing. Results show that displacement would occur at each support due to erection sequence and temperature variation, which should be avoided by taking measures. The stress of lifting point is large during integral lifting process and it almost vanishes after unloading. The simulation method was validated by the agreement between results obtained by monitoring and simulation. The stress and displacement of key components are in control and the construction scheme can satisfy the need of construction. [ABSTRACT FROM AUTHOR]