Abstract ：

This paper proposes a novel method for increasing the distortional frame rigidity of off-rail box girder bridges for cranes by reinforcing the diaphragm with staggered truss. The study starts by using the Matrix Displacement Method to determine the shear angle of the staggered truss diaphragm under two assumptions: hinge joint and rigid joint. To obtain closed -form solutions for the transversal and longitudinal deformations and warping stress of the crane girder, the study employs the Initial Parameter Method and considers the compatibility of shear deformation at joints between the diaphragms and the girder. The theoretical solutions are validated through finite element analysis, which also confirms that the hinge-joint assumption accurately represents the shear angle of the staggered truss diaphragm in girder distortion. Additionally, the study conducts extensive parameter analyses to examine the impact of staggered truss dimensions on distortional stress and deformation. Furthermore, the study compares the distortional warping stresses of crane girders reinforced with staggered truss diaphragms and those reinforced with perforated ones, emphasizing the importance of incorporating stagger truss in diaphragms. Overall, this paper provides a thorough evaluation of the proposed approach's effectiveness in enhancing the distortional frame rigidity of off-rail box girder bridges for cranes. The findings offer valuable insights into the design and reinforcement of diaphragms using staggered truss to enhance the structural performance of crane girders.

Keyword ：

distortion distortion box girder box girder matrix displacement method matrix displacement method steel structure steel structure diaphragm diaphragm stiffener stiffener truss truss

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Abstract ：

A novel shop-welded joint for H-beam to concrete-filled steel tubular column with field-bolted flange splicing used in prefabricated steel structure is proposed. Four full-scale specimens were tested under cyclic loads, and the effects of bolt diameter, beam flange cover plate, widened beam flange at the end, and the flange thickness on the seismic performance of joints were studied by experiments and numerical simulation. The seismic performance of the shop-welded joint is compared to that of traditional welded joints. According to the results, the beam flange thickened by welding cover plate and widened by welding plate at the beam end can improve the yield resistance, ultimate resistance, stiffness, ductility, and energy dissipation capacity of the joint, while the bolt diameter and the flange thickness did not make significant influences. The shop-welded joints could be regarded as rigid. Adding cover plate, widening beam flange, or increasing column base flange thickness can effectively reduce the beam end stress and avoid brittle failure of welds under rare earthquakes. Simplified formulas for the yield and ultimate loads of the shop-welded joint were proposed.

Keyword ：

FE analysis FE analysis Seismic performance Seismic performance Shop-welded joint Shop-welded joint CFST column CFST column Cyclic test Cyclic test Field-bolted flange splicing Field-bolted flange splicing

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Abstract ：

To improve the construction efficiency and achieve a rigid connection under design load, an innovative H-section beam-to-square steel tubular (SST) column bolted connection with inclined braces is proposed. The innovative bolted joint can realize bolted assembly between beam and column as well as between column and column, and it exhibits satisfactory stiffness and strength under earthquake with few bolts. Three groups of beam-column bolted joints with different types of inclined braces were designed, and tests and finite element analysis (FEA) were implemented under cyclic loading. The mechanical behaviour, deformation process, failure modes, and energy dissipation of all specimens were observed, and the effect of the type and length of inclined brace on seismic behaviour of joints was analyzed. The results showed that all specimens exhibited satisfactory ductility, plastic deformation capacity and energy-dissipation capacity. All tested joints with inclined braces showed failure mode of severe local buckling of beam section outside the connecting area, and the strength, stiffness and energy dissipation capacity of bolted joints with inclined braces were significantly improved. The joints with an H-shaped brace dissipate more energy than those with a channel brace, particularly when the web of the H-shaped brace is perpendicular to the beam web. Furthermore, the strength, stiffness and energy dissipation capacity of innovative joints with long diagonal braces are higher than those with short diagonal braces. On the basis of the test results and numerical analysis, simplified calculations for the slip resistance, yield resistance and ultimate resistance of the bolted joints with inclined braces are proposed and validated against tests.

Keyword ：

Seismic performance Seismic performance Prefabricated steel structure Prefabricated steel structure Inclined brace Inclined brace Bolted column -to -column connection Bolted column -to -column connection Bolted beam -column joint Bolted beam -column joint

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Abstract ：

In this study, an H-section steel beam with circular holes in a web wrapped with ceramsite concrete (SBWCC) was studied. Static load-bearing capacity tests and finite element analysis were performed on two groups of specimens with different sections. The H-section steel and wrapped ceramsite concrete were well bonded. The load-bearing capacity of the SBWCC was 10% larger than that of the pure H-section steel beam without holes in the web, except for its dead weight. The stiffness of the SBWCC was slightly larger than that of the pure H-section steel beam without holes. The wrapped ceramsite concrete avoided the elastic local instability of the steel beam flange and web. Based on the finite element model verified by experiments, the influences of hole diameter, hole spacing, and U-shaped stirrups on the flexural capacity of the specimens were analyzed. The formulas for the load-bearing capacities and short-term stiffness of the SBWCC were proposed and verified by tests and finite element analysis.

Keyword ：

steel beam wrapped with concrete steel beam wrapped with concrete short-term stiffness short-term stiffness load-bearing capacity load-bearing capacity flexural performance test flexural performance test ceramsite concrete ceramsite concrete

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Abstract ：

The long-span curved surface steel structure of Beijing Daxing International Airport terminal is super long and large, and the form of the supporting C-shaped column is novel, the structural load bearing is complex. A 1/60 scale model was designed for shaking table test to study its dynamic characteristics under the actions of 8 degree frequent, seismic precautionary and rare earthquakes. The acceleration, displacement and strain under the conditions of one-way, two-way and three-way ground motions were analyzed. The test results show that the response of the overall model is the largest under three-way ground motion, and the structure is greatly affected by the vertical seismic action. The vertical response in the central area is intense, and the horizontal seismic response in other areas is even, which shows that the integrity of the model is good. The supporting structure has good lateral stiffness and its strain response is greatly affected by the horizontal seismic action. The inter-story drift angle under the condition of 8 degree frequent earthquake is 1/639, the inter-story drift angle under the condition of 8 degree rare earthquake is 1/54, which meets the requirement of seismic code. The structure does not collapse under the condition of 9 degree rare earthquake and does not show apparent failure. It is proved that the structure prototype has reasonable safety reserve. The seismic principle that 'the structure hasn't damaged under frequent earthquake, repairable under precautionary earthquake, and doesn't collapse under rare earthquake' is reached, thus the structural design is reasonable. The design of C-shaped column is reasonable, and it has good supporting action and lateral stiffness. © 2021, Editorial Office of Journal of Building Structures. All right reserved.

Keyword ：

Rare earths Rare earths Earthquakes Earthquakes Seismic design Seismic design Steel structures Steel structures Airport buildings Airport buildings Steel testing Steel testing Stiffness Stiffness

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Abstract ：

The static performance of a slidable bolt-assembly connection between a double-angle truss and square hollow structural section (SHSS) column was studied using experiments and finite-element simulations. Four specimens with different sizes or types of bolt holes on the gusset plate were tested and analyzed. The slip resistance, yield strength, ultimate strength, and failure mechanism of each connection were obtained. The static and seismic performances of the connections were compared with those of a welded connection, bolted-welded connection, and all-bolted fixed connection. The results showed that the ductility of the slidable bolt-assembly connection exceeded a value of 10, which was higher than the values for the other connections, but the slip resistance was the lowest. The slip resistance of the bolt-assembly connection under a static load was larger than that under a seismic load. The ultimate strength of the bolt-assembly connection was equal to that of the welded connection, and the stiffness was almost the same as that of the welded connection before the slip. The ultimate strengths of the slidable bolt-assembly connections were almost the same under static and cyclic loads. The slip distance increased by 23 mm when the bolt hole diameter was increased by 2 mm. However, the dimensions and shapes of the bolt holes on the gusset plate only had slight effects on the slip resistance, yield strength, and ultimate strength of the joint. A load-bearing model and formulas for calculating the various strengths of the slidable bolt-assembly connection were proposed. © 2020 Elsevier Ltd

Keyword ：

Bolts Bolts Trusses Trusses Yield stress Yield stress Failure (mechanical) Failure (mechanical) Plates (structural components) Plates (structural components) Traction (friction) Traction (friction) Seismology Seismology Welding Welding

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Abstract ：

In this paper, an H-shaped steel beam wrapped with ceramsite concrete was studied. The H-shaped steel with circular hole in the web was wrapped with ceramsite concrete, and the U-shaped stirrups were used to improve the bonding performance between concrete and H-shaped steel. The ceramsite concrete has good thermal insulation, low heat transfer coefficient, good waterproof performance and light weight. Thus, it can improve the fire-proof and corrosion-resistant capability of steel beam with a little weigh increasing. In order to study the bearing capacity and concrete wrapping effect, the static tests and finite element analysis were carried out on two groups of specimens with different sections. The results show that the built-in steel beam and the wrapped ceramsite concrete are well bonded. The wrapped ceramsite concrete contributes to the bearing capacity of the beam, which can be increased by about 10% compared with the pure steel beam without holes in the web. Compared with the pure steel beam without holes in the web, the overall stiffness has little change. The bending performance of the specimen is similar to that of the reinforced concrete beam, while the wrapped ceramsite concrete avoids the local instability of the beam flange. According to the finite element model verified by experiments, the influences of the diameter of the holes, the spacing of the holes and the spacing of U-shaped stirrups on the flexural capacity of the specimens were analyzed through parametric analysis. Under the conditions specified in GB 50017-2017 'Standard for design of steel structures', the bearing capacity of the specimen with web opening diameter less than 60% the beam height is higher than that of the pure steel beam without web openings. Opening spacing and U-shaped stirrup spacing have little effect on flexural capacity. The formulas for calculating the bearing capacity of specimens are derived and verified, and the formulas can accurately predict the flexural capacity for this type of beam. © 2021, Editorial Office of Journal of Building Structures. All right reserved.

Keyword ：

Bearing capacity Bearing capacity Heat transfer performance Heat transfer performance Reinforced concrete Reinforced concrete Steel corrosion Steel corrosion Finite element method Finite element method Corrosion resistance Corrosion resistance Thermal insulation Thermal insulation Steel beams and girders Steel beams and girders Concrete beams and girders Concrete beams and girders

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Abstract ：

This study presents six pseudostatic tests on square hollow section steel (HSS) column to H-section beam bolted connections with double cover plates. The failure modes, load-displacement hysteresis curves, and backbone curves of the joints were obtained, as were the energy-dissipating capacity, stiffness, and strength. The seismic energy of the connections is dissipated by slip between the contact surfaces and plastic deformation of the beam, clamp plates and bolt holes. The joints have good rotation capacity, energy-dissipation capacity, and reasonable strength and stiffness. The connections are rigid used in bracing frame and unbracing frame before slip and semirigid for both after slip. They are full-strength in terms of strength classification. Before the interstory drift reaches 0.05, no obvious inelastic deformation occurs, indicating that the connections can be easily repaired by repositioning the connection and retightening the bolts after a severe earthquake because the interstory drift will be much less than 0.05 during a severe earthquake. A finite-element model (FEM) was established and validated through a comparison of the finite element analysis (FEA) and test results, and the bolt tension, stress distribution of the beam, and rotation of the column flange splicing connection were obtained from the FEA results. The tension of the bolt in the beam web decreased slightly, while the tension of the bolt in the beam flange decreased to 60-70% of the original pre-tension when the interstory drift reached 0.06. The column flange splice connection is rigid. Simplified formulas for joint strength were deduced and validated by testing and FEA.

Keyword ：

Bolt tension variation Bolt tension variation Contact surface slip Contact surface slip Slip resistance Slip resistance Slip connection Slip connection Bolted connection Bolted connection Seismic performance Seismic performance Bolted rigid connection Bolted rigid connection Bolted steel structure Bolted steel structure Prefabricated steel structure Prefabricated steel structure

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Abstract ：

Steel cable with its superior performance is used in steel structure as a brace. An X-deployed cable-braced bolt-assembly steel frame (CBBSF) was proposed. The seismic behaviors of an unbraced moment-resisting bolted steel frame (BSF) and four pairs of CBBSFs were tested and analyzed by the finite-element model under cyclic load. The steel frames of CBBSF arc the same, while the cables have the same sectional area in each pair and have varying sectional areas between different pairs. In each pair of CBBSF including CBBSF-F and CBBSF-W, the cables of CBBSF-F are pre-slacked, while the cables of CBBSF-W are not pre-tensioned or pre-relaxed. A formula for the lateral stiffness of the CBBSF was proposed. The hysteresis performance, strength, ductility, stiffness, self-centering capability, and failure mode of the CBBSFs were obtained and compared with each other and with the BSF. The influence of the cable sectional area and pre-slack on these behaviors was obtained. It was found that CBBSFs exhibit reasonable hysteresis performance, energy dissipation capacity, self-centering capability, and have large stiffness and strength. The hysteretic performance and energy dissipation capacity of CBBSF is better than BSF. The CBBSF with a larger cable sectional area has better self-centering capability. The energy dissipation capacity and ductility increased initial ly with the increase of cable sectional area, then, followed by a subsequent decrease. The cable pre-relaxation decreased the maximum cable force to avoid break, increased the yield displacement, ultimate displacement, and ductility of CBBSF, and slightly decreased the yield and ultimate strength. (C) 2020 Elsevier Ltd. All rights reserved.

Keyword ：

Lateral stiffness formula Lateral stiffness formula Cyclic loading test Cyclic loading test Cable pre-relaxation Cable pre-relaxation X-deployed cable-braced steel frame X-deployed cable-braced steel frame Bolt-assembly Bolt-assembly Energy dissipation capacity Energy dissipation capacity

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