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- Composite Steel and Concrete Structural Members
- Reinforced concrete
- Steel and Composite Structures
- Reinforced concrete
Composite Steel and Concrete Structural Members
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.
An FE model was developed for the composite truss and was validated using experimental results. 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.
Steel-concrete composite structural members are formed by bonding a steel component to a concrete component, so that the two components function as an integrated unit [ 1 ]. Composite structures can efficiently utilise the properties of the constituting materials to achieve material saving and cost efficiency. Composite members have been extensively applied in civil engineering, e. Among these members, the composite beam, which consists of a steel beam on which a reinforced concrete slab is cast with shear connectors, is the most widely used, because the properties of both materials are fully utilised i.
To ensure composite action, shear connectors are commonly employed at the steel-concrete interface for resisting slippage and separation between the concrete slab and steel beam [ 1 ]. There are many types of mechanical shear connectors with various shapes, sizes, and methods of attachment, such as studs, bolts, channels, and angles. The stud connector is probably the most commonly used connector for steel-concrete composite beams [ 1 ]. To investigate the strength and load-slip behaviour of the stud shear connection, push tests have been widely conducted [ 6 — 8 ].
The failure modes of the stud connection mainly include failure at the shank of the stud, fracture in the welding zone, and concrete crushing [ 9 ]. The shear capacity of the stud generally depends on the diameter of the stud, strength of the steel used for the stud, and material properties of the concrete i.
Many calculation formulas have been proposed by researchers for estimating the strength and load-slip relationship of stud connections [ 9 , 10 ]. Current standards use similar formulas to estimate the shear capacity of stud connectors F u0.
Taking the standard GB [ 11 ] as an example and ignoring partial factors, we have where A s is the cross-sectional area of the stud, E c is the elastic modulus of concrete, f c is the strength of concrete, and f u is the ultimate strength of stud connectors. The US and Europe standards adopt different coefficients to replace 0. Composite trusses are capable of achieving a large span with low cost, providing routes for ventilation and electrical lines and reducing the overall floor-to-floor height [ 14 ].
Robinson and Fahmy [ 15 ] experimentally investigated a composite joist with a partial shear connection. The joist failed via the buckling of the top chord in compression prior to full yielding of the bottom chord, and a design method was proposed for the composite joist with a partial shear connection.
Two full-scale composite trusses were tested under bending by Brattland and Kennedy [ 16 ], which failed via shear-connector failure, followed by the overloading of the top chords. Muhammad [ 17 ] tested two composite trusses and adopted puddle welding or small screws as shear connectors.
The composite truss with the puddle-welding connector exhibited better composite action, with a significantly higher flexural capacity and failed via the overall buckling of the top chords, while shear-bond failure was observed for the other specimen.
Lopez [ 18 ] performed an in situ study on a composite truss floor system, and the buckling of diagonals near the support, which experienced strong axial forces, was identified as the major failure mode. A parametric study on a composite truss was conducted by Bouchair et al.
According to previous studies, the failure modes of composite trusses vary greatly, e. The complexity of the failure modes makes it difficult to develop an accurate method for predicting the structural behaviour of composite truss beams.
In recent years, the steel-concrete composite space truss, which is made of tubular steel members, has attracted the attention of architects and researchers owing to its aesthetical qualities and higher out-of-plane stability compared with the plane truss.
As reported by Reis and Oliveira Pedro [ 21 ], the composite space truss with a triangular section was first proposed by Jean Muller and applied in Roize Bridge. Thus far, a few studies have been performed on this type of composite truss.
An unexpected local failure near the support occurred during the test, which was caused by the large compressive forces in the diagonals. A moment-curvature model was proposed in [ 22 ], which exhibited reasonable accuracy. Machacek and Cudejko [ 23 , 24 ] performed an experimental and numerical study on composite steel and concrete trusses to investigate the shear-force distributions along the beams.
Reviewing the literature reveals a lack of studies on the steel-concrete composite space truss, which may hinder the application of this type of structural member. The influence of the degree of the shear connection on the structural performance of the composite truss has not been clarified. Furthermore, design methods are required to estimate the bending capacity of the composite truss.
To fill this knowledge gap, this paper presents an experimental and analytical study on the flexural responses of steel-concrete composite truss beams SCCTBs. Three simply supported composite trusses with different configurations of shear connection studs were evaluated via three-point bending tests. A finite-element FE model was developed and validated by the experimental results. A parametric study was conducted to investigate the effects of the degree of the shear connection on the flexural response of the composite trusses.
Finally, a design method was proposed for predicting the ultimate capacity, and it exhibited good agreement with the experimental and FE results. Three SCCTBs, which consisted of a steel truss, a concrete slab on it, and shear connectors resisting the slippage between them, were tested. The main parameter was the degree of the shear connection i.
A square pyramid structure was selected for the steel truss to achieve sufficient lateral stiffness. The steel truss was made of circular tubes with fillet welds connecting them together. Stud connectors were employed to connect the steel truss and the concrete slab Figure 1. The critical amount of shear connectors was defined as the quantity of shear connectors that made the shear resistance of the shear connectors equal to the yield capacity of both the top and bottom chords.
According to Code for design of steel structures [ 11 ], the critical amount of shear connectors for the composite truss is To investigate the effect of the quantity of shear connectors on the flexural response of the composite truss, three quantities of shear connectors were selected: 30, 34, and 42 corresponding to specimens B1, B2, and B3, respectively.
A shear interaction factor k is defined as the ratio of critical amount of shear connectors to actual amount of stud connectors. As a result, the shear interaction factors for specimen B1, B2, and B3 are 0.
Three tensile coupons, which were cut from steel tubes, and three reinforcement coupons were tested to obtain the material properties of the steel tubes in the truss and the rebars in the concrete slab. The test results, including the yield strength f y , ultimate strength f u , and elongation, are presented in Table 1 average values. The concrete slab was made of ordinary Portland cement concrete with a strength grade of C The measured material properties of the concrete slab are presented in Table 1 average values.
Here, the cubic strength f cu0 was converted into the cylindrical strength f c , and E c represents the elastic modulus. The composite truss was simply supported on steel bases, in which roller support was achieved by placing steel rods between the beam and the bases, as shown in Figure 3 a. The dial gauges were fixed on the bottom surface of the concrete slab using a custom-manufactured holder, which was mounted in the concrete slab.
The spindles of the dial gauges were in contact with a timber plate, which was glued to the top chord of the steel truss. Therefore, the relative movement between the concrete slab and the steel truss could be measured. The vertical LVDTs were placed on the bottom surface of the concrete slab and the top chord of the steel truss. In addition, two vertical LVDTs were placed at the supports to measure their settlements.
Longitudinal strain gauges were also attached to the middle part of each chord and diagonal, as shown in Figure 3 d. All the data, including the loads, deflections, and strains, were simultaneously acquired by a dataTaker and recorded on a personal computer, as shown in Figure 3 e.
A concentrated force was acted at midspan by the hydraulic jack. To avoid the local concrete crushing, a loading beam was designed to disperse concentrated force, as shown in Figure 3 e. After everything was examined, the test was started. The cracks initially appeared in the middle area of the concrete slab.
The amount of cracks increased with the load. Finally, the cracks expanded and ran through the concrete slab, as shown in Figure 4. The cracks on the bottom side of the concrete slab indicate that the neutral axis was located in the slab; thus, tensile stress was induced on the bottom surface of the slab.
The failure of the composite truss was caused by the yielding of the bottom chords and the concrete crushing of concrete slab. After specimen failure, extensive cracks were observed on the bottom side of the concrete slab. The load-deflection curves of the specimens are shown in Figure 5 , where the deflection is the deflection at the midspan subtracted by the support settlement. The stiffness slope of the load-deflection curve was almost identical for the specimens, i. Then, the nonlinear response was observed.
The curves deviated from each other owing to the different connector arrangements. Finally, the concrete slab at the middle of the beam specimen crushed, signifying the failure mode of SCCTBs.
Meanwhile, the ultimate bearing capacity of the designed beam specimens was mainly controlled by the collapse of the concrete slab. On the one hand, a concentrated force was applied at the middle of the beam specimen so that a large local compressive stress was generated at the loading point. On the other hand, the bending moment also created a compressive stress at the loading point of the concrete slab.
Hence, multidirectional compressive stress field existed in this region, leading to an easy concrete crushing of these designed SCCTBs. As shown in Figure 5 and Table 2 , the stiffness of specimen B1 decreased most rapidly, with the lowest ultimate load of The stiffness and ultimate load of the composite truss increased with the shear connection factor k.
The load-slippage curves of the tested specimens are shown in Figure 6 , in which the slippage is the relative movement between the concrete slab and the top chord at the midspan. Initially, the load increased linearly with the increase of the slippage, as the composite truss was in the elastic phase.
The connector quantity significantly affected the slippage of the composite truss. With the increase of the connector quantity, the slippage decreased, as shown in Figure 6. When the shear interaction factor increased from 1. It is concluded that after a full shear connection was reached i. The load-strain curves for the bottom chord and for the concrete slab at the midspan are presented in Figures 7 and 8 , respectively. In Figure 7 , the load-strain curves are linear and almost identical.
When the truss approached failure, the strain in the bottom chord did not increase dramatically, confirming that the failure of the composite truss was not caused by bottom-chord yielding. In contrast, the load-compressive strain curves for the concrete slab Figure 8 were highly nonlinear, and the strain reached approximately 0. As the strain gauges were located at the midheight i. The influence of the connector quantity on the stress-strain curve was not evident, likely because the neutral axis was in the concrete slab.
The geometric dimensions of the FE model were identical to those of the tested specimens, as shown in Figure 1. The concrete slab was modelled with the eight-node solid element SOLID65 having three degrees of freedom at each node i.
Reinforced concrete , concrete in which steel is embedded in such a manner that the two materials act together in resisting forces. The reinforcing steel—rods, bars, or mesh—absorbs the tensile, shear, and sometimes the compressive stresses in a concrete structure. Plain concrete does not easily withstand tensile and shear stresses caused by wind, earthquakes, vibrations, and other forces and is therefore unsuitable in most structural applications. In reinforced concrete, the tensile strength of steel and the compressive strength of concrete work together to allow the member to sustain these stresses over considerable spans. Reinforced concrete Article Media Additional Info. Print Cite verified Cite. While every effort has been made to follow citation style rules, there may be some discrepancies.
This book deals with the analysis and behaviour of composite structural members that are made by joining a steel component to a concrete component. The emphasis of the book is to impart a fundamental understanding of how composite structures work, so engineers develop a feel for the behaviour of the structure, often missing when design is based solely by using codes of practice or by the direct application of prescribed equations. It is not the object to provide quick design procedures for composite members, as these are more than adequately covered by recourse to such aids as safe load tables. The subject should therefore be of interest to practising engineers, particularly if they are involved in the design of non-standard or unusual composite structures for buildings and bridges, or are involved in assessing, upgrading, strengthening or repairing existing composite structures. The fundamentals in composite construction are covered first, followed by more advanced topics that include: behaviour of mechanical and rib shear connectors; local buckling; beams with few shear connectors; moment redistribution and lateral-distortional buckling in continuous beams; longitudinal splitting; composite beams with service ducts; composite profiled beams and profiled slabs; composite columns; and the fatigue design and assessment of composite bridge beams. For practising and consulting engineers and undergraduate and postgraduate students studying the behaviour of composite structures.
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It presents the concepts, definitions and design philosophy for basic structural elements, including composite slabs, beams and columns, and.
Steel and Composite Structures
Reinforced concrete RC , also called reinforced cement concrete RCC , is a composite material in which concrete 's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is usually, though not necessarily, steel bars rebar and is usually embedded passively in the concrete before the concrete sets. Modern reinforced concrete can contain varied reinforcing materials made of steel, polymers or alternate composite material in conjunction with rebar or not. Reinforced concrete may also be permanently stressed concrete in compression, reinforcement in tension , so as to improve the behaviour of the final structure under working loads. In the United States, the most common methods of doing this are known as pre-tensioning and post-tensioning.
Static analysis of FGM cylinders by a mesh-free method M. Foroutan, R. Moradi-Dastjerdi,and R. Abstract In this paper static analysis of FGM cylinders subjected to internal and external pressure was carried out by a mesh-free method. In this analysis MLS shape functions are used for approximation of displacement field in the weak form of equilibrium equation and essential boundary conditions are imposed by transformation method.
This paper presents an experimental and analytical study on the flexural response of a steel-concrete composite truss beam.
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Composite structures of steel and Chapter 3 Simply-supported composite slabs and beams. a member composed of concrete and structural steel, nor of the use of Warwick, for facilities provided, and most of all to the writer's wife.
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