Steel-concrete Composite Truss Research Articles

Shear strength of steel-concrete composite “NPS® Basic” truss beams

NPS® Basic beams are steel-concrete composite truss beams with a steel-plate bottom chord and plain-bar top chord, completed with concrete cast in situ, that are part of the NPS® frame system. Determining the shear behavior and strength of NPS® Basic beams is challenging due to the complex resisting mechanisms involved and because of the various peculiarities these beams present. This paper provides the necessary theoretical, numerical and experimental evidence for the identification of a rational design procedure of NPS® Basic beams subjected to shear loads.The state of the knowledge of the shear response of steel-concrete composite truss beams is first summarized, including available experimental evidence and code-based design methodologies. A preliminary assessment of these shear design approaches is performed, by comparison with the limited experimental results available. Then, the existing shear behavior database is expanded by generating a large amount of data via non-linear numerical analyses (calibrated against the available experimental evidence) of a set of shear-critical case-study beams. The results of this parametric study are combined with the available experimental evidence to support recommendations of a rational shear design approach.

Study on Load–Slip Curve of a PBL Shear Key at a Steel–Concrete Composite Joint

The steel–concrete composite truss adopts a new type of steel-concrete composite joint with high rigidity and load-carrying capacity. In order to more conveniently and clearly grasp the working mechanism of Perfobond Leiste (PBL) shear keys in the core area of new composite structures such as steel–concrete composite trusses, the lack of strong theoretical support for the theoretical formula of load–slip relationships in the entire loading process of single PBL shear keys is solved. By proposing a straight–curved–straight three-stage simplified load–slip curve with respect to the PBL shear key, the stress process of the PBL shear key is divided into three stages—the elastic stage, plastic stage, and strengthening stage—based on the compressive yield and failure critical point of tenon concrete in the shear key. With reference to the calculation method of the bearing capacity of the order pile under horizontal loads and by calculating the shear stiffness of the shear key, a theoretical formula suitable for separating the load–slip relationship of a single PBL shear key in the entire loading process of the ear plate composite joint is proposed. The results show that, in the elastic section, the slope of the curve is related to the concrete reaction coefficient and the material parameters of the penetrating steel bar; moreover, in the strengthened section, the coefficient is related to the shear modulus of the penetrating steel bar, and a more uniform length distribution of the penetrating steel bar between the two joint plates will improve the initial stiffness of the PBL shear key to a certain extent. The results of the proposed method are in good agreement with the finite element results and experimental values. This research study’s results can provide a convenient design method for the design of the internal PBL shear keys of new composite structure joints, promoting the promotion and application of new composite structures and advancing the development of the engineering field.

Stress on Steel-concrete Composite Truss Joints Research Status and Application Overview

Based on the comprehensive analysis of various stress research schemes for steel-concrete composite truss joints, the current research status of steel-concrete composite truss joints and epoxy resin concrete at home and abroad are systematically elaborated. The existing problems in the current composite truss joints are analyzed, and possible solutions are proposed. At present, the research on epoxy resin concrete has been very extensive. Epoxy resin concrete has high strength, good toughness, high impact strength, good chemical corrosion resistance, wear resistance, water resistance, frost resistance, tensile resistance and compressive resistance, which make it widely used in engineering. The problem of using epoxy resin concrete instead of ordinary concrete in steel-concrete composite truss is put forward, analyzed and discussed.

Flexural Response of Steel-Concrete Composite Truss Beams

This paper presents an experimental and analytical study on the flexural response of a steel-concrete composite truss beam. This integrated unit consists of a triangular steel truss, a concrete slab on it, and stud connectors. Three simply supported composite trusses with different configurations of shear connection (η) were evaluated via three-point bending tests. The effects of the shear connectors’ configuration on the flexural response (i.e., load-deflection, load-slippage, and load-strain curves) of the composite trusses were examined. The commercial finite-element (FE) software ANSYS was employed to conduct numerical simulations. An FE model was developed for the composite truss and was validated using experimental results. A parametric study was performed to investigate the effect of the shear connectors’ configuration on the flexural response of the composite trusses. If η < 1, the bending capacity increased with η. In contrast, if η ≥ 1, the effect of η on the bending capacity was negligible. Finally, a design method based on the degree of the shear connection was proposed to predict the ultimate capacity of the composite truss, and the predictions agreed well with the experimental results.

Analysis on natural vibration characteristics of steel-concrete composite truss beam

In order to study the natural vibration characteristics of steel-concrete composite truss beam (SCCTB), the influence of multiple factors such as interface slip, shear deformation and moment of inertia are considered. Afterwards, based on the Hamilton principle the vibration control differential equation and natural boundary conditions of SCCTB are deduced. By solving SCCTB differential equations of vibration control, an analytical calculation method is proposed for analyzing the natural vibration characteristics of SCCTB. The natural frequencies of SCCTBs with different degrees of shear connection and effective lengths are calculated by using the analytical method, and the results are compared against those obtained from ANSYS finite element numerical calculation method. The results show that the analytical method considering the influence factors such as interface slip, shear deformation and moment of inertia are in good agreement with those obtained from ANSYS finite element numerical calculation method. This evidences the correctness of the analytical method and show that the method proposed exhibits improvement over the previously developed theories for the natural vibration characteristics of SCCTB. Finally, based on the analytical method, the influence factors of SCCTB natural vibration characteristics are analyzed. The results indicate that the influence of interface slip stiffness on SCCTB\'s natural frequency is more than 10% and therefore cannot be neglected. Moreover, shear deformation has an effect of more than 35% on SCCTB\'s natural frequency and the effect cannot be ignored either in this case too.

Theoretical and experimental study on deflection of steel-concrete composite truss beams

This paper investigates the deflection of the steel-concrete composite truss beam (SCCTB) at the serviceability limit state. A precise solution for the distributed uplift force of the SCCTB, considering five different loading types, is first derived based on the differential and equilibrium equations. Furthermore, its approximate solution is proposed for practical applications. Subsequently, the shear slip effect corresponding to the shear stiffness of the stub connectors, uplift effect corresponding to the axial stiffness of the stub connectors and shear effect corresponding to the brace deformation of the steel truss are considered in the derivation of deflection. Formulae for estimating the SCCTB deflection are proposed. Moreover, based on the proposed formulae, a practical design method is developed to provide an effective and convenient tool for designers to estimate the SCCTB deflection. Flexure tests are carried out on three SCCTBs. It is observed that the SCCTB stiffness and ultimate load increase with an increase in the shear interaction factor. Finally, the reliability of the practical design method is accurately verified based on the available experimental results.

Improved Finite Beam Element Method to Analyze the Natural Vibration of Steel-Concrete Composite Truss Beam

Based on Hamilton’s principle, this study has developed a continuous treatment for the steel-concrete composite truss beam (SCCTB). It has also deduced the SCCTB element stiffness matrix and mass matrix, which include the effects of interface slip, shear deformation, moment of inertia, and many other influencing factors. A finite beam element method (FBEM) program for SCCTB’s natural vibration frequency has been developed and used to calculate the natural vibration frequencies of several SCCTBs with different spans and different degrees of shear connections. The FBEM’s calculation results of several SCCTBs agree well with the results obtained from ANSYS. Based on the results of this study, the following conclusions can be drawn. For the SCCTB with high-order natural vibration frequency and with short span, the effect of the shear deformation is greater. Hence, the effect of the shear deformation on the SCCTB’s high-order natural vibration frequency cannot be ignored. On the other hand, the effect of the interface slip on the SCCTB’s high-order natural vibration frequency is insignificant. However, the effect of the interface slip on the SCCTB’s low-order natural vibration frequency cannot be ignored.

Connection Performance in Steel–Concrete Composite Truss Bridge Structures

AbstractConnections for steel–concrete composite trusses (SCCTs) for bridge applications were investigated. Eight specimens on a scale of 1/3 of the actual bridge were tested under static loading using connections with different gusset plates, including rectangular (RGP), π shape (PSGP), and J shape (JSGP). A detailed account of the design considerations, loading procedure, and experimental parameters is provided. A three-dimensional (3D) finite-element (FE) model was developed to analyze the mechanical behavior of these three composite truss connections. The results of the FE analysis were in good agreement with the experimental results. Both indicated excellent mechanical behavior for the investigated composite truss connections, with sufficient safety factors. The minimum yielding, cracking, and ultimate loads obtained from specimens were 2.65, 2.21, and 3.87 times the design load (907 kN), respectively. All specimens underwent considerable deformation, thereby suggesting satisfactory ductility. The pr...

Experimental and Numerical Investigation on Bending Capacity of Steelconcrete Composite Truss Girder

This article presents an experimental investigation on the bending capacity of steel-concrete composite truss girder (SCCTG). Four full-scale specimens named CB1, CB2a, CB2b and CB3 respectively, are tested and numerical analyzed. Stress distribution, load-displacement relationship, load-slip relationship and ultimate bending capacity of SCCTGs are investigated. The results show that SCCTG follows plane section assumption on the whole. SCCTG has a higher ultimate bearing capacity and good performance of deformation. Concrete slab and the steel truss can work together better using denser studs. In elastic stage, the effective width of the SCCTG flange plate remains the same with negligible variation. While in plastic stage, the effective width increases. Tests also prove that there is obvious shear lag effect in the concrete compression flange. Three-dimensional numerical model by finite element package ABAQUS is established to examine the bending behaviour of SCCTG. Hopefully, an acceptable correlation has been observed between the analytical and experimental results. There is obvious shear lag effect in the concrete compression flange. Shear lag should be paid great attention when designing and calculating the bearing capacity and deformation of SCCTG.

Experimental research on end joint of steel-concrete composite truss

Steel-concrete composite truss is characterized by such advantages: high stiffness, low height and construction costs. Moreover, it has promising application prospects. Since the interfacial load between concrete and steel is still indeterminate, experimental research and finite element analysis were carried out on two samples in scale of 1:3 models of composite truss joint models. A detailed account of the design philosophy, structural origin, loading procedure and test items followed. Test results showed that under design load, the joints were at elastic stage all along. Joints cracking load was twice as much as the design load. Their yield load was 3.2 times the design load and the ultimate load was 3.5 times the design load. The joints had a high safety factor which met the design requirements. The joints failing process was that cracks appeared on concrete first, and the web members yielded soon after, leading to joint yield. Now that both the concrete chord and the steel web members failed, there is no obvious increase in joint bearing capacity after joint yield. But the joints underwent severe deformation and possessed good ductility. For this reason, the joints could be applied in engineering practice.

Zhengzhou Yellow River road‐cum‐railway bridge, China

AbstractZhengzhou Yellow River road‐cum‐railway bridge accommodates both the Beijing–Guangzhou passenger railway line and the Zhengzhou–Xinxiang inter‐city highway, which cross the Yellow River at Zhengzhou, China (Fig. 1). The bridge is 9177 m long and has two distinct sections[1]: the first is a six‐pylon continuous steel‐concrete composite truss extradosed bridge with a span arrangement of 120 5 ¥168 120 m; the second is a continuous steel‐concrete composite truss with a span arrangement of 5 ¥120 m. The main bridge has a double deck, with a six‐lane carriageway on the upper deck and a twin‐track railway on the lower deck. An inclined truss structure is used for the main bridge superstructure. The upper deck is of concrete, the lower deck uses orthotropic steel solution. The analysis revealed that the main bridge has good rigidity and favourable service conditions for high‐speed trains. The main steel truss was constructed by incremental launching.

Connection in Steel-Concrete Composite Truss

The design specifications of composite truss, included in the American standard (ASCE), are not covered in the European standards (Eurocodes). In this study, to investigate the behavior of the composite trusses, a finite element (FE) model is developed using the software CAST3M. The influence of various parameters, such as the diameter of the shear connectors, the top chord section, the degree of connection, and the material characteristics, on the behavior of the composite truss and the shear connectors are analyzed. The model shows that the shear connection in the steel-concrete composite truss reduces its deflection by approximately 50% in comparison to the steel truss. The significant influence of the top chord section on the shear forces in the shear connectors was observed.

Analysis of the Behaviour of Steel-Concrete Composite Truss

The design specifications of composite truss, included in the American standard (ASCE), are not covered in the European standards (Eurocodes). In this study, to investigate the behaviour of the composite trusses, a finite element model (FEM) is developed using the software CAST3M. The influence of various parameters, such as the diameter of the shear connectors, the degree of connection, the top chord section and the material characteristics on the behaviour of the composite truss and the shear connectors are analyzed. The model shows that the shear connection in the steel-concrete composite truss reduces its deflection by approximately 50 % in comparison with the steel truss. The significant influence of the top chord section on the shear forces in the shear connectors was observed.