Bolted joints in steel structures are generally subject to combined actions. The research on ultimate capacity of bolted joints under combined tension and shear actions, twin shear actions, and combined tension-twin shear actions is relatively limited. The aim of this paper is to calibrate the fracture locus of grade 10.9 bolts using the mesoscale critical equivalent plastic strain (MCEPS). We use ductile fracture simulation to numerically evaluate the ultimate resistance of bolts subject to multiaxial loading and compare the results with the current design standards. The results show that predictions for grade 10.9 bolts subject to multiaxial loading in Chinese code GB 50017 and American code AISC-360 are not on the safe side, while predictions in European code EN1993-1-8:2005 are slightly on the conservative side. We propose two modification factors to improve prediction of bolt strength subject to multiaxial loading; namely the multiaxial loading factor for shear resistance ξv and the multiaxial loading factor for tensile resistance ξt.@en

For long-span composite bridges with corrugated steel webs, the encased concrete near the intermediate support section increases the weight of the girder, reduces pre-stressing efficiency, and causes difficulties in the construction process. The authors in the companion paper [1] proposed a corrugated steel web with vertical or/and horizontal stiffeners to replace or shorten the length of concrete encasement. In parallel with experimental study described in the companion paper, this paper further investigates the shear performance of proposed stiffened corrugated steel webs by numerical and analytical methods. Firstly, finite element (FE) models considering material nonlinearity, welding residual stress, and geometric imperfection were established and validated against the experimental results. Then the effects of web thickness, corrugation depth, height and thickness of stiffeners on shear strength and failure modes were analyzed based on the validated FE models. Finally, both experimental and numerical shear strength were used to evaluate the applicability of existing calculation methods proposed by different scholars to predict the shear capacity of stiffened corrugated steel web. The comparisons reveal that calculation methods proposed by Hassanein & Kharoob [2] and Leblouba et al. [3] predict the shear capacity of pure corrugated steel web more accurately, and all existing calculation methods underestimate corrugated steel web with vertical stiffeners. Therefore, the analytical model for accurately predicting shear strength of stiffened corrugated steel web need to be developed, which will be investigated in subsequent studies.@en

Failure of bolts exposed to tension is generally avoided in the design of bolted connections due to the smaller deformation capacity of bolts than the connected plates. This is one of the reasons why few studies focus on the tensile failure behaviour of bolts. However, failure behaviour of bolts is essential for the advanced finite element analysis especially relevant to the deformation capacity and failure mode of bolted connections. This paper presents a numerical study on the fracture of partially threaded bolts under tension incorporating damage models, with which the failure mechanism of bolts can be better understood. The post-necking stress–strain relation is firstly calibrated to describe the behaviour of bolt threaded parts at large deformation. Then, direct tension tests on partially threaded bolts with different threaded lengths within the grip are modelled using ABAQUS with the explicit solver. Two criteria for fracture are investigated: the void growth model (VGM) and a model proposed by Bao and Wierzbicki (BW). The former is adopted to simulate the tensile fracture of bolts and the latter is used to predict the thread stripping failure. Results indicate that bolt failure modes of tensile fracture and thread stripping can be well predicted by combining the calibrated post-necking stress–strain relation and a suitable fracture criterion in the analysis. It is revealed that the large plastic strain in the threads introduced by thread rolling process is a major reason for the thread stripping failure.@en

Composite girder with corrugated steel web is one of the promising concrete-steel hybrid structures with superior properties and cost effectiveness widely applied in highway and railway bridges. The connection between concrete slabs and corrugated steel web is an important part of such composite structure. In order to improve pouring quality and durability of concrete for joint structure between corrugated steel webs and concrete lower slab, the validity of placing lower slab on the inner side of corrugated steel webs was confirmed and a new joint structure with perforated plate connectors was proposed. Push-out tests on proposed joint structure with different parameters including the welding width and the plate thickness were carried out to study their shear strength, shear stiffness, failure modes and relative slip characteristics. Subsequently, three-dimensional finite element models taking material non-linearity and nonlinear contact between steel and concrete interface into consideration were built and validated by the push-out tests. Afterwards, parametric studies were performed to further investigate the influences of geometrical parameters (such as width, height and thickness of perforated steel plate) and material parameters including steel yielding strength and concrete compressive strength on ultimate shear strength and failure mode of the joint structure. Analytical results indicate that the shear loading capacity is increased with the thickness, the width and height of perforated plate, and the compressive strength of concrete. However, steel yielding strength, presence or absence of perforating rebar, have a negligible effect on ultimate shear strength of the joint structure. Finally, prediction equations of shear capacity were provided and compared with experimental and numerical results. The calculated shear capacity agrees well with experimental and numerical ones, indicating provided analytical equations can accurately predict shear capacity for such novel joint structure.@en

In order to evaluate the shear performance of sand-coated glass fiber-reinforced polymer (GFRP) perforated connectors (SCGPC) embedded in concrete, 8 pull-out tests were conducted. Finite element (FE) analysis considering GFRP failure and cohesion between GFRP and concrete of SCGPC were conducted for parametric analysis. Effects of surface treatment, hole's radius, embedment length, and multi holes were examined. The test and theoretical analysis revealed that the strength of SCGPC is considerably larger than GFRP Perforated Connector (GPC). The stiffness of SCGPC is determined by the adhesion between concrete and GFRP. When GFRP plate's thickness is less than the critical thickness, the embedment length plays a major role in the strength of SCGPC. When embedment length is less than the effective bond length, the shear strength of SCGPC is governed by both the adhesion and GPC's shear capacity; otherwise, the strength of SCGPC is governed by the adhesion strength. Furthermore, an empirical equation was suggested to predict the shear strength of SCGPC. The equation involves the failure mechanism of both bond and GPC and deals the strength of SCGPC into two ranges according to the embedment length. Good agreement was achieved between the strength prediction by the suggested equation and the parametric analysis result.@en

Many bolted connectors were proposed for use in steel-concrete composite structures over the past few decades. This is because using bolted connectors could make the assembly and disassembly of steel-concrete composite structures more convenient and reusing the dismantled structural components could also improve structural sustainability. Lots of static and fatigue experimental tests on steel-concrete bolted connectors were conducted but detailed finite element simulations including fracture of bolted connectors were rarely reported. This paper presents a series of simulations of a demountable steel-concrete bolted connector in push-out tests, which was proposed and reported by the authors of this paper before. Damage models of bolt and concrete materials are incorporated in the simulations to better understand the behaviour of the bolted connector and the failure mode of the push-out tests. Direct tension tests on bolts are simulated to calibrate the stress-strain relationship of bolt material and assumed pure shear tests on bolts are modelled to validate the fracture criterion used in the simulations. Results of modelling push-out tests indicate that the friction force at the steel-concrete interface accounts for a part of shear resistance of the bolted connector in push-out tests conducted. The load-slip curves and the fracture of bolts in push-out tests can be approximately predicted by incorporating damage models of bolt and concrete materials and considering an appropriate friction coefficient. The effects of concrete damage model, clearance in bolt hole, and pretension of short bolt on the shear performance of the bolted connector are discussed at last.@en

The headed stud connectors are widely used in a variety of innovative engineering applications of the infrastructure sector. The fatigue life of headed studs is significantly affected by the residual stress introduced from welding procedures. It is very important to develop a reliable numerical method to predict the fatigue performance of headed stud connectors. In this paper, the efficiency of fatigue life prediction, using the nominal stress (NS) and the hot spot stress (HSS) methods based on finite element simulation, is compared. The limitation using the NS method to predict the fatigue life of studs is discussed in this paper. The efficiency of the HSS analysis technique is validated by the fatigue test results in the literature.@en

Numerical analyses incorporating appropriate damage models provide an opportunity to predict the strength and deformation capacity of steel structures. This paper presents a practical calibration for the ductile damage model of S355 and high-strength steel S690Q, S700MC, S960Q based on tensile coupon test results. A combined linear and power expression is adopted to calibrate the post-necking damaged stress–strain relations of the investigated steels, upon which the undamaged stress–strain relations are estimated further. Damage initiation criterion is based on the Rice-Tracey model and damage evolution law is related to the calibrated damaged stress and the estimated undamaged stress. Fracture of the tensile coupons is modelled using a critical damage variable. Tensile coupon tests on the investigated steels are modelled in ABAQUS with the explicit solver. Results show that combining the proposed post-necking stress–strain relations and ductile damage model generates very good predictions for strain localization and final fracture of the tensile coupons. Numerical engineering stress–strain curves agree well with the experimental results. It also indicates that high-strength steels are more susceptible to damage than S355. The damage variable of S960Q is about 2 times as large as that of S355 from the onset of necking to the final fracture.@en

Design optimization of fiber-reinforced polymeric (FRP) composite products is essential to facilitate their applications in engineering structures. For bridge structures, the main design optimization goals are the reduction of FRP material consumption and the structure weight, which aim to reduce the initial construction cost and achieve a longer bridge span. Compared with conventional steel–concrete composite bridges, FRP-steel composite bridges possess more design variables and more complex design process, which necessitate the simplified optimization models. This paper aims to propose a two-scale design optimation method for FRP bridge deck on the steel girder. The macro behavior of the pultruded FRP composite bridge deck is analyzed. Regarding the micro level, the equivalent properties of pultruded GFRP lamination are calculated by combining micromechanics and classical lamination theory (CLT). The above-mentioned macro pultruded GFRP bridge level and the micro fiber/resin level were bridged based on the assumption that the micro-component effective homogenized strain equals to the corresponding macro strain. The two-scale lamination optimization of pultruded GFRP bridge deck is finally achieved by finding optimized two-scale design variables that can achieve the minimum bridge weight or the lowest initial construction cost with all listed constraint requirements satisfied. A pultruded FRP deck supported on equally-spaced steel girders was selected as a case study to show how to obtain the optimized two-scale parameters by using this proposed optimization method. The optimized results of the top flange thickness, tu, the bottom flange thickness, tl, the web height, hw, and the web thickness per meter, tw, are 46.02 mm, 45.86 mm, 300.0 mm and 37.42 mm, respectively. Results also showed that the optimized ratio of the 0°-lamina, 45°-lamina, and the 90°-lamina are77.9%, 17.1%, 5.0%. The optimized fiber volume fraction is 65.2%.@en

In this paper, analytical and numerical homogenization methods are proposed to effectively simulate the macroscopic characteristics of a pultruded composite lamina. A continuum damage model was implemented via user material subroutine to model fiber failure, while the Mohr-Coulomb plastic criterion is employed to model matrix damage. In order to simulate the damage of the fiber-matrix interface, the relationship between traction and displacement is established. The proposed theoretical and numerical models were verified by tensile, compressive, and shear test results. The outcomes of this study indicated that both theoretical, numerical prediction values agree well with experimental verification results confirming the validity of the proposed methodology in providing a reliable reference for structural design of pultruded fiber reinforced polymeric (FRP) composite structures.@en

Steel-concrete composite high bridge pier has been applied increasingly in China and around the world. Most applied steel type in the composite piers are H-shaped steel and steel pipe, while seldom research or practice is associated with angle steel. This paper conducted parametric study on the composite column with equal-leg angle steel and aimed to investigate the ultimate load and displacement ductility of the composite columns with different parameters. The parameters include the type of shear connector (stud and perfobond connectors), the type of structural steel (H-shaped steel and angle steel), steel-plate hooping ratio, shear-span ratio, and axial compression ratio. Finite element analysis was conducted for each specimen, which incorporated the concrete confinement effect, as well as the inelastic behavior of concrete, structural steel, and longitudinal and transverse steel bars. The equal-leg angle steel composite column was found to have slightly higher strength and displacement ductility than H-shaped steel composite column. The increase of steel-plate hooping result in larger strength and displacement ductility for the composite column, and the increase of shear-span ratio and axial compression ratio decrease the displacement ductility. Research results suggest stud and perfobond shear connectors should be applied as axial compression ratio being larger than 0.2 and 0.3, respectively. This paper provides reference for research and engineering practice of the concrete encased angle steel composite columns and bridge piers.@en

In addition to general shear loading, perfobond shear connectors (PBLs) also undertake tensile uplift forces at the interfaces between steel parts and concrete components. The tensile behavior of PBLs is as significant as the shear behavior to the safety of composite bridge structures. For further evaluating the combined shear-tensile response of PBLs, it is necessary to first investigate the tensile mechanism of PBLs. Accordingly, uplift tests with three specimens under static and cyclic loading were performed to investigate the tensile behavior of PBLs. The test results showed that the breakouts of concrete blocks dominated the failure of PBLs in tension. The residual separation was negligible when the tension force was below 30 percent of the capacity. Subsequently, a detailed finite element (FE) model for the uplift test was established and validated based on the test results. The strain path inside concrete blocks was presented as a cup shape, whose dimension was relevant to the embedded depth of holes and the boundary conditions. Further, 360 FE models with varying hole diameters, perforated rebar diameters, embedded depths, and concrete strength were conducted to explain the tensile mechanism and provide databases for the theoretical analyses. The results showed that the diameter of perforated rebars was irrelevant to the tensile capacity and stiffness of PBLs, while both the tensile capacity and stiffness increased with the embedded depth and concrete strength. Besides, the tensile stiffness was also related to the hole diameter. Consequently, according to the forms of existing tensile capacity expressions for headed studs and Mindlin's solution, the equations for the tensile capacity and stiffness of PBLs were derived.@en

The prestressed concrete girder with corrugated steel webs is one of the most promising steel-concrete hybrid structures applied to highway and railway bridges, owing to its excellent mechanical properties and efficient material utilisation. Composite bridges with corrugated steel webs (CBCSWs) have undergone rapid development in China since 2005, resulting in remarkable technical progress in many aspects. A state-of-the-art review of CBCSWs in China is presented. Based on data collected for over 90 CBCSWs built in China during the years 2005-2018, characteristics relating to bridge span, structural type and construction methods are comprehensively analysed. Some mechanical issues regarding the design and construction of typical CBCSWs are elaborated to understand fully their structural performance and promote their development. Furthermore, a few representative CBCSWs are expounded in relation to their innovative structural design and construction techniques; their respective characteristics are highlighted. Finally, several conclusions are drawn and future research directions are predicted: the CBCSW is a competitive bridge solution when 80-200 m main spans are required; advanced materials, innovative structure types and advanced construction methods making good use of corrugated steel web are the source of its development. The experiences in this study can serve as a useful base for constructing more excellent and impressive CBCSWs.@en

The prestressed concrete girder with corrugated steel webs is one of the most promising steel-concrete hybrid structures applied to highway and railway bridges, owing to its excellent mechanical properties and efficient material utilisation. Composite bridges with corrugated steel webs (CBCSWs) have undergone rapid development in China since 2005, resulting in remarkable technical progress in many aspects. A state-of-the-art review of CBCSWs in China is presented. Based on data collected for over 90 CBCSWs built in China during the years 2005-2018, characteristics relating to bridge span, structural type and construction methods are comprehensively analysed. Some mechanical issues regarding the design and construction of typical CBCSWs are elaborated to understand fully their structural performance and promote their development. Furthermore, a few representative CBCSWs are expounded in relation to their innovative structural design and construction techniques; their respective characteristics are highlighted. Finally, several conclusions are drawn and future research directions are predicted: the CBCSW is a competitive bridge solution when 80-200 m main spans are required; advanced materials, innovative structure types and advanced construction methods making good use of corrugated steel web are the source of its development. The experiences in this study can serve as a useful base for constructing more excellent and impressive CBCSWs.@en

Steel-concrete composite structures have been extensively used in building, bridges, and other civil engineering infrastructure. Shear stud connectors between steel and concrete are essential in composite members to guarantee the effectiveness of their behavior in terms of strength and deformability. This study focuses on investigating the shear stiffness of headed studs embedded in several types of concrete with wide range of compressive strength, and their effects on the elastic behavior of steel-concrete composite girders were evaluated. Firstly, totally 206 monotonic push-out tests from the literature were reviewed to investigate the shear stiffness of headed studs embedded in various types of concrete (NC, HPC, UHPC etc.). Shear stiffness of studs is defined as the secant stiffness of the load-slip curve at 0.5Vu, and a formulation for predicting defined shear stiffness in elastic state was proposed, indicating that the stud diameter and the elastic modulus of steel and concrete are the main factors. And the shear stiffness predicted by the new formula agree well with test results for studs with a diameter ranging from 10 to 30 mm in the concrete with compressive strength ranging from 22.0 to 200.0MPa. Then, the effects of shear stiffness on the elastic behaviors of composite girders with different sizes and under different loading conditions were analyzed, the equations for calculating the stress and deformation of simply supported composite girders considering the influence of connection's shear stiffness were derived under different loading conditions using classical linear partial-interaction theory. As the increasing of shear stiffness, the stress and deflection at the most unfavorable section under partial connected condition tend to be those under full connected condition, but the approaching speed decreases gradually. Finally, the connector's shear stiffness was recommended for fully connection in composite girders with different dimensions under different loading conditions. The findings from present study may provide a reference for the prediction of shear stiffness for headed studs and the elastic design of steel-concrete composite girder.@en

Steel-concrete composite structures have been extensively used in building, bridges, and other civil engineering infrastructure. Shear stud connectors between steel and concrete are essential in composite members to guarantee the effectiveness of their behavior in terms of strength and deformability. This study focuses on investigating the shear stiffness of headed studs embedded in several types of concrete with wide range of compressive strength, and their effects on the elastic behavior of steel-concrete composite girders were evaluated. Firstly, totally 206 monotonic push-out tests from the literature were reviewed to investigate the shear stiffness of headed studs embedded in various types of concrete (NC, HPC, UHPC etc.). Shear stiffness of studs is defined as the secant stiffness of the load-slip curve at 0.5Vu, and a formulation for predicting defined shear stiffness in elastic state was proposed, indicating that the stud diameter and the elastic modulus of steel and concrete are the main factors. And the shear stiffness predicted by the new formula agree well with test results for studs with a diameter ranging from 10 to 30 mm in the concrete with compressive strength ranging from 22.0 to 200.0MPa. Then, the effects of shear stiffness on the elastic behaviors of composite girders with different sizes and under different loading conditions were analyzed, the equations for calculating the stress and deformation of simply supported composite girders considering the influence of connection's shear stiffness were derived under different loading conditions using classical linear partial-interaction theory. As the increasing of shear stiffness, the stress and deflection at the most unfavorable section under partial connected condition tend to be those under full connected condition, but the approaching speed decreases gradually. Finally, the connector's shear stiffness was recommended for fully connection in composite girders with different dimensions under different loading conditions. The findings from present study may provide a reference for the prediction of shear stiffness for headed studs and the elastic design of steel-concrete composite girder.@en

This paper proposed an easy-installed rubber-ring perfobond connector (RPBL) to mitigate the shear concentration of partial holes in perfobond connector (PBL) groups. Four modified push-out tests with different rubber ring thicknesses were conducted to investigate the shear behavior of RPBLs. The test results showed that specimens experienced four stages, including (i) damage of bond, (ii) shear fractures of concrete dowels, (iii) tension-shear yielding of perforated rebars, and (iv) hardening and fractures of perforated rebars. The rubber rings can significantly improve the slip capacity and drop the shear stiffness of perfobond connectors. Compared with ordinary perfobond connectors, the yield slips of specimens with 2 mm, 4 mm and 6 mm thick rubber rings increase by 304%, 509% and 745%. Further, three-dimensional nonlinear parametric FEA (finite element analysis) models of modified push-out tests were established and verified by the test results. The shear mechanism of each component and the effects of rubber ring thickness on shear behaviors were discussed. Finally, the shear yield load equations and shear capacity equations of PBL and RPBL were proposed based on the collected modified push-out test results. The calculated results agree well with the test results.@en

To evaluate the mechanical and fatigue behavior of composite suspender-girder anchorage joints in arch bridges, fatigue tests of two composite joints including pure-shear and shear-compression types were conducted and the load transfer mechanisms were evaluated based on the static loading. The experimental results indicated that both proposed composite anchorage joints presented great combined behavior. The load ratio of PBLs dropped sharply with the increase of embedded depth. Approximately 1/3 of the suspender tensile load was carried by the PBLs in the first row. Due to the redundant PBLs and large embedded depth, few loads were resisted by the bearing plate. Before and after the fatigue loading process, the shear amplitude of PBLs and the vertical stress distribution of concrete were almost consistent, indicating the favorable fatigue performance of joints. Parameterized solid nonlinear finite element models were established and verified by the test results to investigate the effect of total row number of PBLs and presence of bearing plate on the load transfer mechanics. The numerical results showed that the increase of total row number of PBLs enlarged the degree of irregularity of load distribution and reduced the load ratio of bearing plate. Finally, the load ratio formula of PBLs and bearing plate under serviceability stage was derived. The calculated load ratios were in good agreement with the test and numerical results. It was proposed that the total row numbers of PBLs were no >4 or 6 for the joints with or without bearing plate.@en

Perfobond shear connectors (PBLs) are increasingly applied in steel-concrete composite structures. The out-of-plane (lateral) shear behavior of PBLs is still unknown to researchers and designers, although the connectors undertake considerable out-of-plane shear forces in some applications. Thus, push-out tests with three specimens were first conducted to investigate the lateral shear performance of PBLs and further used to validate the corresponding numerical models. The test results show that perforated rebars and concrete dowels are irrelevant to the lateral shear capacity, while they can reduce the separations and improve the ductility. Secondly, parametric FEA (finite element analysis) models for the push-out tests were built and validated based on the test results. The plastic strains in concrete mainly develop at the regions close to the fillet welds. Further, 144 extended FEA models with varying height, length, and thickness of perfobond plates and concrete compressive strength were conducted to reveal the lateral shear mechanism of PBLs. By enlarging the plate height, the lateral shear capacity slightly increases, while the shear stiffness remains as constant. The shear capacity and stiffness increase with the plate length and thickness, as well as the concrete compressive strength. Finally, based on the existing shear capacity equations for channel and angle connectors, and the theory of elastic foundation beams, the expressions for the lateral shear capacity and stiffness of PBLs were put forward. The proposed equations agree with the results of the parametric study.@en

Perfobond shear connectors (PBLs) are increasingly applied in steel-concrete composite structures. The out-of-plane (lateral) shear behavior of PBLs is still unknown to researchers and designers, although the connectors undertake considerable out-of-plane shear forces in some applications. Thus, push-out tests with three specimens were first conducted to investigate the lateral shear performance of PBLs and further used to validate the corresponding numerical models. The test results show that perforated rebars and concrete dowels are irrelevant to the lateral shear capacity, while they can reduce the separations and improve the ductility. Secondly, parametric FEA (finite element analysis) models for the push-out tests were built and validated based on the test results. The plastic strains in concrete mainly develop at the regions close to the fillet welds. Further, 144 extended FEA models with varying height, length, and thickness of perfobond plates and concrete compressive strength were conducted to reveal the lateral shear mechanism of PBLs. By enlarging the plate height, the lateral shear capacity slightly increases, while the shear stiffness remains as constant. The shear capacity and stiffness increase with the plate length and thickness, as well as the concrete compressive strength. Finally, based on the existing shear capacity equations for channel and angle connectors, and the theory of elastic foundation beams, the expressions for the lateral shear capacity and stiffness of PBLs were put forward. The proposed equations agree with the results of the parametric study.@en