In traditional end plate column splices, bolts are placed double symmetrically on the four sides of square hollow sections (SHS). In order to reduce the required gap between the façade and the column, the end plate could be flushed on one or two sides of SHS for the column along the façade or at the corner of a building, respectively. However, the analytical solution (Component method) for the traditional column splice is not applicable in this case. This paper addresses the tensile behaviour of asymmetric column splices, where a cover plate is used on the end plate flushed side. Columns are dominantly loaded in compression and bending, but to verify the component's interaction, the column splices are tested in tension in this paper. The tensile behaviour is investigated through the experiment, the finite element (FE) analysis, and the component method. Eight tensile tests were conducted. The FE model is validated against the experiment. A bi-linear model is employed to characterise the column splice yield resistance, which shows a good agreement with the ultimate resistance of the FE model using a constitutive model without strain hardening. The effective length measured from the FE model is approximately two times that calculated by equations. Using the measured effective length, the component method predicts the characterised yield resistance well (average 13% lower). In comparison, the resistance is underestimated by 35% on average if the calculated effective length is used.

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Acoustic emission (AE) is often used for structural health monitoring (SHM) in the wide field of engineering structures and one of its most beneficial attributes is the ability to localize the damage/crack based on the AE events. The vast majority of ongoing work on AE monitoring focues on geometrically simple structures or a confined area, but the AE source location strategies are rather complicated for real engineering structures. In this paper, an effective method for source localization in realistic structures is presented based on the application of artificial neural networks (ANN), using finite element (FE) simulation results of Lamb waves as the modelling basis. Pencil lead break experiments and related FE simulations on a steel-concrete composite girder are conducted to evaluate the performance of the method. The identification of different wave modes is carried by comparing alternative onset time detection methods. Numerical results are found to be matching closely with the experimental results. To get a reliable ANN model, the validated FE model is used to create a comprehensive database with five different sensor arrangements. It is found that the proposed method is superior to the classical Time of Arrival (TOA) method with the same input data. The results indicate that using trained neural networks based on numerical data is a viable option for AE source location in the case of the I-shaped girder, increasing the likelihood of design and optimization of the AE technique in monitoring realistic structures.

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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 assessment of fatigue crack propagation of steel structures is essential and important especially to improve the application of high strength steel in construction. The load ratio R, reflecting mean stress effects, will be changed with crack extension in the steel structures with complicated geometry. In this paper, the Walker equation is employed to fit the fatigue crack propagation rate of steel grades S355 and S690 based on experimental data in the literature to incorporate the mean stress effects. The material fatigue crack propagation parameters with 95%, 97.7%, and 99% guarantee of Walker equation were obtained by a stochastic analysis using the Monte Carlo method. The fatigue life was firstly predicted by the analytical method and was used as a baseline for numerical fatigue crack propagation simulation. A user-defined fatigue crack propagation subroutine based on the Walker equation was developed using phantom nodes-based extended finite element method (PN-XFEM) and Virtual Crack Closure Technique (VCCT) to consider the mean stress effects. The proposed three-dimensional fatigue crack propagation simulation subroutine is successfully validated of both steel grades, S355 and S690.

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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.

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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.

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The development of numerical simulation for Ultra-high-performance concrete (UHPC) and Ultra-high-performance fiber-reinforced concretes (UHPFRC) is fundamental for the design and construction of related structures. The simplified engineering stress-strain relationship and the input values are necessary in the finite element modeling. Four-linear curves and modified Kent–Park model were proposed to describe the engineering tensile and compressive stress-strain relationship, respectively. An attempt was made to simulate the fracture of UHPC and UHPFRC using concrete damaged plasticity model and element deletion strategies. The predicted tensile and compressive behaviors of UHPC and UHPFRC were successfully validated by the test results in the literature. For a better understanding of the mechanical behavior of UHPC and UHPFRC exposed to biaxial loadings, mixed-mode crack propagation simulation on the double-notched specimens exposed to combined shear-tensile and shear-compressive forces was discussed.

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Predicting the ultimate capacity of components made of high strength steel (HSS) is a numerically challenging task. The fracture performance of HSS from different steel grades, producers, and manufacturing processes (rolling, cold forming, etc.) varies greatly. It is costly to conduct a series of experiments for each typical HSS structural component to identify the parameters of the fracture model. An attempt is made to evaluate the fracture material properties based only on the standardized uniaxial stress-strain curve. The uncoupled fracture model was implemented through a user subroutine VUMAT (ABAQUS) to evaluate the ductile fracture of HSS, where a rate-independent non-linear isotropic J2 hardening model is used in combination with a separate Hosford-Coulomb fracture model. The detailed procedure to identify the material parameters based on only the uniaxial stress-strain curve of steel grades S700 and S960 are provided for the sake of illustration of possible applications. The proposed fracture model and identified parameters are validated based on the experimental results of the HSS plate with different hole sizes in the middle of the dog bone specimens. Besides, a desktop study of a single K gap joint with β = 0.5 made of square hollow sections using S700 and S960 is used to illustrate a possible application of the fracture model in a simplified model of the structural joint.

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Orthotropic steel decks (OSD's) are susceptible to fatigue failure due to cyclic loading. Often fatigue cracks are found in the joint between the deck plate and the trough. Due to the welding process, residual stresses are present in and around the joint. In this paper, the effect of residual stresses on the fatigue crack propagation rate has been evaluated. First, a FE model has been made to predict and validate the residual stress field of the OSD due to welding. The validation of residual stresses is made comparing measured data at the surface of the OSD and over the thickness of the deck flange. The residual stresses are used to subsequently model for a crack propagation analysis based on extended finite element method (XFEM). The fatigue crack simulation including residual stress field shows good correlation compared to the experimental data, while the simulation without residual stress field shows less correlation. The effects of the residual stresses are relatively large as the tensile transversal residual stresses increase the crack propagation, while the tensile longitudinal residual stresses decrease the crack propagation rate. The optimal modelling of the component of residual stresses is investigated.

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In recent years, wire arc additive manufacturing (WAAM) has increasingly attracted attention in the construction sector because of its ability to optimize the production of large metallic structural parts, and for use in connections suitable for easy execution and potential reuse. The technology has become mature leading to shorter fabrication times and less expensive total costs due to lower raw material costs. Therefore, it is timely to conduct the material tests to evaluate the plastic flow and fracture of the WAAM steel plate to gain material characterization for an efficient design of connections. In this paper, the coupon specimens are cut from the WAAM plates in different directions in relation to the printing orientation to investigate possible material anisotropy. Results of uniaxial coupon specimens, the stress-strain curve, are analyzed in three stages: the elastic stage, the plastic stage and the coupled plastic-damage stage. The FE simulation is performed to calibrate the true stress and strain curves in different stages.@en

The fatigue resistance of welded connections made of high strength steel (HSS) is one of the most important topics for the application of HSS in the construction sector. One of the most challenging issues is how to predict the fatigue life of welded structures with complex geometry based on the test results from relatively simple coupon specimens. However, there are generally pre-existing residual stresses in the welded coupon specimens during fatigue tests, and these residual stresses vary greatly in welded structures with complex geometry. This increases the difficulty in predicting the fatigue behaviour of welded structures based on results at coupon scale. Hence, it is important to establish a relationship between the residual stress independent material characteristics and fatigue life. The fatigue behaviour of complex welded structures can be predicted by this residual stress independent material characteristics calibrated at the coupon level and simulated local residual stress distribution. In this paper, the residual stress-free characteristics, hardness, is employed to predict the fatigue life of butt-welded joints. Besides, the residual stress of V-shaped butt welds on a plate made of high strength steels are analysed by modelling of the welding process based on subsequent thermal analysis and mechanical stress analysis by implementing kill/birth strategies. The results show that it contributes to a better prediction compared with experimental results after considering the residual stress effects.

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Wire arc additive manufacturing (WAAM) has increasingly attracted attention in the construction sector because of its ability to produce large metallic structural parts in short times. In this paper, Coffin-Manson and Morrow (CMM) equation is employed to compare the fatigue life of WAAM stainless steel with the structural steels S355 and S690. The results showed that the fatigue performance of structural steel is better than the WAAM stainless steel, the fatigue performance vertical to printing direction (WAAM-900) is better than it along the printing direction (WAAM-00). In addition, the fatigue cycle of the transition reversals of structural steel is much less than it of WAAM stainless. With the increasing the fatigue cycle, the maximum density of the strain amplitude ratio is gradually increased to 1.0. The probabilistic parameters of CMM equation were obtained by a stochastic analysis using Latin hypercube sampling strategies. The probabilistic strain-fatigue life behaviour obtained from the constant exponent sampling strategy is higher when compared with the varied exponent sampling strategy for both WAAM stainless and structural steels.

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The material reduction factor of rectangular hollow section (RHS) joints in a new version of Eurocode 3 part 1–8 is validate for steel with the nominal yield strength up to 700 MPa. In this paper, finite element simulations of gap K-joints are conducted to investigate effects of material properties, gap size of the joint, the brace to chord width ratio and welds type on the secondary bending stresses and the resistance. The governing failure mode considered for all the FE models is the chord face failure followed by brace sidewall failure. The ratio of axial stresses to the nominal stress was lower in the compressive brace made of higher strength steel grades compared to the mild strength grades. The maximum secondary bending stresses is 0.12–0.32 yield strength. The secondary bending stresses are increasing with the increase of the steel grade and the brace to chord width ratio and with reducing the gap size. The level of secondary bending stresses varied between 38% and 56% of the average normal axial stress. The secondary bending stresses of fillet-welded joints are larger than the butt-welded joints. The yield line model is used to predict the ultimate load and good agreement is obtained compared with FE results.

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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.

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The design of FRP profile-concrete composite sections, including beams and decks, is usually governed by the shear strength of the FRP profiles. However, analytical methods that can precisely predict the shear capacity of the composite sections have not been well developed, because there is lack of knowledge of the FRP-concrete composite action and distribution of shear stress along the FRP. This paper investigates the shear behaviors of FRP-concrete composite sections and develops formulae to predict the shear capacity of the composite sections. First, flexural tests of three FRP-concrete composite beams were conducted to investigate the shear failure mode and interface behaviors. All the beams failed in FRP shear fracture along horizontal direction. Then, push-out tests were used to determine the slip property for the FRP-concrete interface which reveals that FRP stay-in-place form and steel bolts can ensure full and partial composite action, respectively. Based on the experimental study, closed-form equations to compute the maximum shear stress are derived and validated against experimental data in this paper and literature. Finally, simple yet reliable equations of shear capacity are derived and recommended for engineers to design the FRP-concrete composite sections.

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Acoustic Emission (AE) is used in various fields of engineering and recently has been gained increasing attention in crack detection of cyclically loaded engineering structures. The crack location strategies are rather complicated for realistic structures with complex geometry. In this paper, pencil leads breaking (PLB) experiments and finite element simulation of lamb wave propagation are conducted to give a rational interpretation on acoustic wave propagation within composite structures. Identification of the fundamental extensional mode (S0) and flexural mode (A0) is successfully carried out. The proposed FE models are proven to be a suitable alternative/complement to the experiments, in the monitoring of realistic structures.@en

Owing to the superior mechanical performance and material efficiency, the combination of prestressed concrete (PC) slabs and corrugated steel webs (CSW) as PC girder with CSWs (PCGCSW) is extensively applied to railway and highway bridges. To overcome the shortcomings of traditional balanced cantilever construction (TBCC) of PCGCSW, reduce environmental impact, and promote sustainable construction, a novel asynchronous-pouring-construction (APC) technology is introduced in this paper. This improved method makes full use of the excellent shear capacity of the corrugated steel webs (CSWs) to support the hanging basket, increases the construction platforms to accelerate the construction speed. Based on a practical project of a long-span composite box girder bridge with CSWs in China, the construction process of the APC method is systematically introduced, and the structural safety and environmental sustainability of such bridge using APC technology are evaluated and compared with that using TBCC. The comparison results indicate that APC method can reduce the compressive stress of top concrete slab, but slightly increase the shear stress and deflection during the cantilever construction stage because the hanging basket is directly supported by CSWs. Besides, the weight of the improved handing basket in APC technology is reduced up to half in comparison that in TBCC. Accordingly, the APC technology saves a lot of energy consumption, reduces huge CO₂ emissions for construction equipment, and shorts construction period. Therefore, the utilization of APRC technology can ensure the bridge's safety and reliability, effectively accelerate construction speed, reduce the construction load, decrease the environmental pollution, and save the engineering cost, which can be regarded as a sustainable and environmental-friendly construction method for composite bridges with CSWs.

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Residual stresses change the stress ratio of fluctuating stresses, hence seriously affect the fatigue life of orthotropic steel decks (OSDs) under traffic loading. Residual stress distributions near the U rib-diaphragm joints are very complicated and need to be investigated further. In this paper, a systematic method has been proposed for calculating the residual stress field in the joint of U rib and diaphragm due to thermal cutting and welding. Firstly, a mathematical model of cutting heat sources was established to predict the temperature field. Then, a numerical elastoplastic thermomechanical model was built to predict the residual stress evolutions in a diaphragm-rib joint through the whole fabrication process involving flame cutting and welding. Moreover, the simulated temperature contours at the fusion zone and the residual stress distributions in the rib-diaphragm joint were compared and verified against the experimental ones. The numerical results showed a great agreement with the experimental ones, indicating that the heat source model can be used to accurately predict the temperature field during flame cutting. Finally, the validated numerical model was utilized to conduct parametrical analyses on the effects of thermal processing rates, e.g., the cutting and welding speeds and on the residual stress distribution in the rib-diaphragm joint. The results indicate that a faster cutting speed and a slower welding speed can decrease the residual stress magnitude at the rib-diaphragm joints and reduce the high-stress zone near the diaphragm cutouts.

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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.

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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, t_u, the bottom flange thickness, t_l, the web height, h_w, and the web thickness per meter, t_w, 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%.

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