Analysis of deflections of composite slabs with profiled sheeting up to the ultimate moment

This paper deals with an investigation of the deflections of composite slabs. The deflection of composite slabs depends directly on the shear stiffness of the connection between profiled steel sheeting and concrete. A method for calculating deflections of slabs is presented in this paper. This method is based on a theory of built-up bars, which allows one to take into account directly the shear stiffness of the connection. Influences on the stiffness of the structure of normal cracks in the concrete layer and plastic deformations of concrete that has been subjected to compression are also taken into account in the analysis method. The method gives one an opportunity to assess variations of these factors at all stages of the slab’s behaviour from the start of loading up to the ultimate moment. Results of the experimental investigations of a connection (contact) between steel profiled sheeting (Holorib type) and concrete are presented in this paper. In the results of these investigations, three stages of behaviour of the contact are distinguished. A connection shear characteristic is determined for each stage, which is used for calculating the deflection of the slab.Experimental investigations were performed on deflections of composite slabs with a Holorib type of profiled sheeting. Variations in experimental deflections of slabs were explored from the beginning of loading up to the ultimate moment.Theoretical calculations of deflections for the experimental slabs were made. Calculations were performed according to the method proposed by the authors. A comparison of experimental and theoretical values of deflections revealed that agreement between these values was sufficiently good at all stages of the slab’s behaviour.     

Modelling and analysis of two-way composite slabs

The paper deals with the modeling and analysis of the ultimate behavior of two-way composite slabs. A software package of COSMOS/M 2.6 is used. Non-linear material properties are considered. The proposed finite element model is validated by making a comparison with full-scale tests published in literature for one and two-way composite slabs. Many parameters are studied, such as slab aspect ratio and slab slenderness ratio. The effect of embossments flattening is considered. The effect of cold steel straps which are fixed to the bottom steel deck flange perpendicular to corrugation direction is studied, including the variation of its thickness and distribution. Also the effect of shear studs is considered. The effect of all previous parameters on the ultimate capacity, distribution of reactions into both weak and strong directions, and slab deflection are investigated. The results are also recorded at the serviceability limit state. The analytical results of the two-way composite slabs are compared with the corresponding results of one-way composite slabs. A dramatic increase occurs on slab loads and distribution of reactions into the weak direction. A considerable decrease occurs on slab deflection as a result of using steel straps and studs.     

Shear bond mechanism of composite slabs — A universal FE approach

The strength of concrete slabs composited with cold-formed profiled steel decks is normally governed by the longitudinal shear bond failure at the steel concrete interface. The design methods for the longitudinal shear bond strength adopted in the current construction practice such as the m-k method and partial interaction method all based on the full-size tests, which are expensive and time consuming, however are also semi-empirical. A universal FE approach of composite slabs is presented, in which the shear bond interaction between the steel deck and the concrete is treated as a contact problem considering adhesion and friction. Both geometrical and material nonlinearities are all considered in the FE model. The preliminary FE analysis is verified in simulation of the pull-out tests as far as the cohesion and the frictional bond of the contact interface are considered. The fine FE analysis using the contact model is further carried out in study of the composite slabs in flexural bending. The FE analysis based on the nonlinear contact concept is verified and validated by comparing the test results for both the pull out and bending tests of the composite slabs. Comparisons of the experimental and the FE analytical results indicate that the FE analysis based on the interface contact model, agree well with the test results, and is capable of predicting the performance and the load carrying capacity of composite slabs.     

Factors governing the shear response of prestressed concrete hollowcore slabs under fire conditions

This paper presents results from numerical studies on the effect of critical factors governing the shear response on prestressed concrete (PC) hollowcore slabs exposed to fire. A validated three dimensional finite element model is applied for evaluating failure of fire exposed prestressed concrete (PC) hollowcore slabs under different limiting states, including through shear. This model accounts for temperature induced property degradation in concrete and prestressing strands, cracking in concrete, varying fire exposure, loading and restraint conditions. The factors varied in the parametric study include, slab depth, load level, loading pattern, axial restraint, level of prestressing, and fire scenario. Results from parametric studies show that slab depth, load level, loading pattern, axial restraint, level of prestressing and fire scenario have significant influence on the fire response of PC hollowcore slabs, and failure under these conditions can occur through shear limiting state prior to reaching flexural limiting state. Results from parametric studies are further utilized to propose a simplified approach for evaluating shear capacity PC hollowcore slabs under fire conditions.     

New evaluation and modeling procedure for horizontal shear bond in composite slabs

A new method for modeling the horizontal shear bond in steel deck-concrete composite slabs is proposed. The method considers the slab slenderness as the strength parameter that affects the accuracy of horizontal shear bond modeling. A calculation procedure called the Force Equilibrium method is developed to generate shear bond stress versus end slips relationship (shear bond property) from bending tests. An interpolation procedure is also presented to estimate the shear bond property curves for slabs of varying slenderness using two sets of bending test data. The shear bond property curves are applied to connector elements of finite element models to model the horizontal shear bond behavior in composite slabs. The results of this study show that the shear bond of composite slabs under bending varies with the slenderness parameter, and hence influences the slab strength and behavior, as well as affecting the accuracy of the finite element analyses. The finite element analyses conducted on slabs with different slenderness utilizing a single shear bond property, which are not varied according to the slenderness parameter, may lead to either safe or unsafe results, depending on the geometry of the slabs.     

The composite effect of steel fibres and stirrups on the shear behaviour of beams using self-consolidating concrete

Based on the investigation of the influence of steel fibre on the workability of fresh self-consolidating concrete (SCC), this paper presents the experimental results carried out on a series of simply supported SCC rectangular beams, using steel fiber reinforcement with and without stirrups, and subjected to four-point symmetrically placed vertical loads. The major test variables are the steel fibre content and stirrup ratios. The current study on the shear strength of conventional reinforced concrete (RC) beams verifies the shear strength of SCC beams with steel fibres. The investigation indicates that the shear strength significantly increases by increasing the fibre content; the addition of steel fibres in an adequate percentage can change the failure mode from a brittle shear collapse into a ductile flexural mechanism. The stirrups can be partially replaced by steel fibres. The combination of steel fibres and stirrups demonstrates a positive composite effect on the mechanical behaviour. The shear strength recorded experimentally is compared with the value obtained from the proposed formula, and the correlation is satisfactory.     

Capacities of headed stud shear connectors in composite steel beams with precast hollowcore slabs

In steel-concrete composite beams, the longitudinal shear force is transferred across the steel flange/concrete slab interface by the mechanical action of the shear connectors. The ability of the shear connectors to transfer these longitudinal shear forces depends on their strength, and also on the resistance of the concrete slab against longitudinal cracking induced by the high concentration of shear force. Most of the research in composite construction has concentrated on the more traditional reinforced concrete and metal deck construction, and little information is given on shear capacity of the headed studs in precast hollowcore slabs. In this paper, a standard push test procedure for use with composite beams with precast hollowcore slabs is proposed. Seven exploratory push tests were carried out on headed studs in solid RC slabs to validate the testing procedures, and the results showed that the new test is compatible with the results specified in the codes of practice for solid RC slabs. Once a standard procedure is established, 72 full-scale push tests on headed studs in hollowcore slabs were performed to determine the capacities of the headed stud connectors in precast hollowcore slabs and the results of the experimental study are analysed and findings on the effect of all the parameters on connectors’ strength and ductility are presented. Newly proposed design equations for calculating the shear connectors’ capacity for this form of composite construction are also be given.     

Bending resistance of composite slabs made with thin-walled steel sheeting with indentations or embossments

The paper studies the behaviour of thin-walled steel sheeting with embossments. The study aims to determine the contribution of the embossed areas of the steel sheeting to the total strength in pure tension and in pure bending. For this study, various three-dimensional finite element models are constructed, which take accurately into account the nonlinear response of the problem. The study concludes that there is a strong relation between the area of the embossment region that can be considered as active and the ratio between the depth of the embossment and the thickness of the profile.     

组合楼板的全过程挠度分析

对组合楼板的挠度进行研究,其值直接取决于异型钢板与混凝土间连接的剪切刚度。基于架构理论,直接考虑连接的剪切刚度,提出计算组合楼板挠度的方法,考虑混凝土层正常裂缝和受压下塑性变形对结构刚度的影响。采用本方法,可获得这些影响因素从初始阶段至极限状态全范围的变化情况。对异型钢板与混凝土的连接试件进行试验,结果表明:其连接性能分3个阶段。每个阶段都有不同的剪切特性,用于计算楼板挠度。从加载初期至极限状态,分析Holorib异型板组合楼板变形试验值的变化。采用本方法计算的楼板变形值,与试验值吻合较好。     

组合楼板的全过程挠度分析

对组合楼板的挠度进行研究,其值直接取决于异性钢板与混凝土间连接的剪切刚度。基于架构理论,直接考虑连接的剪切刚度,提出计算组合楼板挠度的方法,考虑混凝土层在普通裂缝和受压下塑性变形对结构刚度的影响。采用本方法,可获得这些影响因素从初始阶段至极限状态全范围的变化情况。对异形钢板与混凝土的连接试件进行试验,结果表明:其连接性能分3个阶段。每个阶段都有不同的剪切特性,用于计算楼板挠度。从加载初期至极限状态,分析Holorib异形板组合楼板变形试验值的变化。采用本方法计算的楼板变形值与试验值吻合较好。     

Dynamic analysis of composite systems made of concrete slabs and steel beams

Structural engineers have long been trying to develop solutions using the full potential of its composing materials. At this point there is no doubt that the structural solution progress is directly related to an increase in materials science knowledge. These efforts in conjunction with up-to-date modern construction techniques have led to an extensive use of composite floors in large span structures. On the other hand, the competitive trends of the world market have long been forcing structural engineers to develop minimum weight and labour cost solutions. A direct consequence of this new design trend is a considerable increase in problems related to unwanted floor vibrations. For this reason, the structural floors systems become vulnerable to excessive vibrations produced by impacts such as human rhythmic activities. The main objective of this paper is to present an analysis methodology for the evaluation of the composite floors human comfort. This procedure takes into account a more realistic loading model developed to incorporate the dynamic effects induced by human walking. The investigated structural models were based on various composite floors, with main spans varying from 5 to 10 m. Based on an extensive parametric study the composite floors dynamic response, in terms of peak accelerations, was obtained and compared to the limiting values proposed by several authors and design standards. This strategy was adopted to provide a more realistic evaluation for this type of structure when subjected to vibration due to human walking.     

The behaviour of reinforced concrete slabs in fire

In this paper a robust model is presented based on the previous layer procedure developed by the author to also take into account the effects of concrete spalling on the behaviour of concrete slabs under fire conditions. In this study, a detailed analysis of a uniformly loaded reinforced concrete slab subject to different degrees of concrete spalling under a standard fire regime is first carried out. Further, a series of analysis of floor slabs with different degrees of concrete spalling is also performed on a generic reinforced concrete building. A total of 16 cases have been analysed using different degrees of spalling on the slabs, with different extents and positions of localised fire compartments. It is clear that adjacent cool structures provide considerable thermal restraint to the floor slabs within the fire compartment. And it is evident that the compressive membrane force within the slabs is a major player in reducing the impact of concrete spalling on the structural behaviour of floor slabs in fire.     

The tensile membrane action of unrestrained composite slabs simulated under fire conditions

Following a major fire test programme on a full-scale, steel-framed building it was found that the composite flooring system, comprising lightweight concrete, anti-crack mesh reinforcement and steel deck, had a greater inherent fire resistance than suggested by current codified design methods. It was felt that this was due to tensile membrane action occurring in the slab at large displacements. This led to an independent test being conducted at the Building Research Establishment where a 9.5 m×6.5 m composite slab, with nominal horizontal restraint to its edges, was tested to failure. To simulate the behaviour of the slab in fire, the steel deck was removed, leaving the concrete and anti-crack reinforcement, before load was applied. Tensile membrane action was shown to occur, with the failure load being approximately double that calculated using the classic yield line theory.     

速成墙板-钢筋混凝土组合楼板的受力性能研究

利用非线性有限元方法,对速成墙板-钢筋混凝土组合楼板受力全过程进行分析,结合实测数据,对计算所得的荷载-挠度曲线、截面应变及承载力进行了对比,并对结果进行分析,建立了力学分析模型,为今后对这种结构进行计算机模拟试验提供了参考依据。     

压型钢板-混凝土组合楼板纵向受剪承载力试验研究

针对组合楼板主要的破坏模式——纵向剪切破坏进行分析,对8块U76型压型钢板-混凝土组合楼板进行了静力试验。试验结果表明:组合板越厚、剪跨越小、剪力横向钢筋越多,组合板纵向受剪承载力就越高。通过与无栓钉组合板的试验结果比较分析,表明组合板中剪跨区的栓钉,能极大地提高受剪承载力;并通过试验得到组合板的荷载-纵向相对滑移关系曲线图,采用欧洲规范4的建议公式,以试验数据为依据,回归得出组合楼板的剪力粘结系数m、k,为该种楼板的工程设计提供参考依据。     

压型钢板-混凝土组合楼板剪切粘结性能研究

为研究YX75-200-600和YX76-344-688压型钢板-混凝土组合楼板的剪切粘结承载力和剪切粘结性能,进行了18块足尺寸简支压型钢板-混凝土组合楼板的载荷试验,并进行了相关的分析。试验结果表明:18个试件的破坏形态均为剪切粘结破坏,影响剪切粘结性能的主要因素有剪跨、压型钢板厚度和栓钉。由试验数据分析得到的端部有栓钉YX75-200-600压型钢板-混凝土组合楼板的剪切粘结系数m,k为228.12,-0.015,YX76-344-688压型钢板-混凝土组合楼板的剪切粘结系数m,k为246.9,-0.0028。     

Experimental and numerical investigation on the shear behaviour of friction-welded bar-plate connections embedded in concrete

Friction-welded bar-plate connections are a basic structural component of Bi-steel steel-concrete-steel sandwich construction. In Bi-steel members, the bar-plate connections, embedded in concrete, are subject to tension, shear and bending. The static and fatigue behaviour of the embedded connections subjected to bar tension is described in another paper [Xie M, Chapman JC. Static and fatigue tensile strength of friction-welded bar-plate connections embedded in concrete. Journal of Constructional Steel Research [in press]]. This paper presents experimental and numerical studies on the static behaviour of the friction-welded connections with the bar loaded in shear. Finite element analysis is carried out to examine the effects of variations in geometric and material parameters. The experimental results are used to derive an empirical equation for predicting the shear strength of embedded connections, and compared with existing test results and code specifications. Further papers will describe fatigue behaviour of the embedded connections subjected to bar shear, and static and fatigue tests on Bi-steel beams.     

闭口压型钢板-轻骨料屋面板抗弯试验研究

结合闭口压型钢板-轻质混凝土组合板的应用现状,阐述了该新型屋面结构的优点,通过试验对其抗弯刚度性能进行了研究,并总结了抗弯刚度的理论计算公式,得出计算结果与实测值吻合较好的结论.     

Theoretical and experimental study on composite steel-concrete shear walls with vertical steel encased profiles

The present work describes the theoretical study and the experimental tests on composite steel-concrete shear walls with steel encased profiles (CSRCW), performed at Politehnica University of Timi?oara, Romania. The composite steel-concrete structural shear walls with steel encased profiles can be used as horizontal resisting systems for buildings that require considerable large horizontal load capacity. The study consists in numerical analysis and tests on 1:3 scale experimental steel-concrete composite elements. The experimental elements differ by the arrangement of the steel shapes embedded in the cross section of the wall and by the cross section type of the steel encased element. Headed steel studs are provided to ensure the connection between the steel profiles and the concrete. The aim of this study is to analyze the nonlinear behavior of elements, focused on the connection between the steel profiles and the concrete respectively, to compare the behavior of shear walls with different steel shape encased profiles with typical reinforced concrete shear walls. Using the tests performed until failure, the maximum load, the deformation capacity and the dissipated energy were evaluated.     

基于抛物线形库仑-莫尔准则的钢筋混凝土板抗冲切承载力

在刚塑性冲切计算模型的基础上,采用二次抛物线形库仑 莫尔混凝土强度准则,运用虚功原理,建立考虑混凝土板中抗弯钢筋销栓作用的冲切承载力计算式。根据已有板冲切试验研究成果,如冲切角和破坏时刻抗弯钢筋应力等数据,对板冲切承载力计算式进行简化,给出简化计算式。与国内外混凝土板冲切试验数据进行计算比较后发现,简化计算式的计算结果较好地符合实测承载力;抗弯钢筋的销栓作用约占钢筋混凝土板总冲切承载力的6%～11%,而忽略抗弯钢筋的销栓作用会给计算结果带来较大影响。