Deflection Of Composite Beams Research Articles

Analysis of Equivalent Flexural Stiffness of Steel–Concrete Composite Beams in Frame Structures

Vertical deflection of a frame beam is an important indicator in the limit-state analysis of frame structures, particularly for steel–concrete composite beams, which are usually designed with large spans and heavy loads. In this study, the equivalent flexural stiffness of composite frame beams is analysed to evaluate their vertical deflection. A theoretical beam model with a spring constraint boundary and varied stiffness segments is established to consider the influence of both the rotation restraint stiffness at the beam ends and the cracked section in the negative moment region, such that the inelastic bending deformation of the composite beams can be elaborately described. By an extensive parametric analysis, a fitting formula for evaluating the equivalent flexural stiffness of the composite beams, including the effects of the rotational constraint and the concrete cracking, is obtained. The validity of the proposed formula is demonstrated by comparing its calculation accuracy with those of existing design formulas for analysing the equivalent flexural stiffness of the composite beam members. Moreover, its utility is further verified by conducting non-linear finite element simulations of structural systems to examine the serviceability limit state and the entire process evolution of beam deflections under vertical loading. Finally, to facilitate the practical application of the proposed formula in engineering design, a simplified method to calculate the deflection of composite beams, which utilises the internal force distribution of elastic analysis, is presented based on the concept of equivalent flexural stiffness.

Static analysis of composite beams on variable stiffness elastic foundations by the Homotopy Analysis Method

New analytical solutions for the static deflection of anisotropic composite beams resting on variable stiffness elastic foundations are obtained by the means of the Homotopy Analysis Method (HAM). The method provides a closed-form series solution for the problem described by a non-homogeneous system of coupled ordinary differential equations with constant coefficients and one variable coefficient reflecting variable stiffness elastic foundation. Analytical solutions are obtained based on two different algorithms, namely conventional HAM and iterative HAM (iHAM). To investigate the computational efficiency and convergence of HAM solutions, the preliminary studies are performed for a composite beam without elastic foundation under the action of transverse uniformly distributed loads considering three different types of stacking sequence which provide different levels and types of anisotropy. It is shown that applying the iterative approach results in better convergence of the solution compared with conventional HAM for the same level of accuracy. Then, analytical solutions are developed for composite beams on elastic foundations. New analytical results based on HAM are presented for the static deflection of composite beams resting on variable stiffness elastic foundations. Results are compared to those reported in the literature and those obtained by the Chebyshev Collocation Method in order to verify the validity and accuracy of the method. Numerical experiments reveal the accuracy and efficiency of the Homotopy Analysis Method in static beam problems.

Numerical parametric study on steel-concrete composite floor beams vibrations due to pedestrian traffic

Human perception of floor vibrations and uncompromised serviceability of equipment are two most important acceptability criteria considering floor vibrations. While verification of deflection is a simple and well-known procedure in structures' design for serviceability limit state, the fulfilment of floor vibrations acceptability criteria are presented in different standards in the form of various calculation procedures. Results achieved through those calculation procedures are presented in the form of various classification of floor structures. Classification of composite floor structures due to vibrations is inconsistent considering different calculation procedures. Comparison of various calculation procedures for the definition of composite floor vibrations is presented in this paper. In addition, a parametric analysis is performed on the wide range of steel-concrete composite floor structures, through analysis of various composite floor layouts and a wide range of imposed loads values. The analysis of the relation between deflection, vertical vibrations and accelerations of steel-concrete composite floor beams is presented in this paper. The results of the parametric analysis are given through direct relation between deflections of composite beams and achieved floor class for the fulfilment of vibrations acceptability criteria due to the pedestrian walking.

Experimental Verification of Design Models in a Static and Dynamic Loading Test

Nowadays more and more often investors and constructors are building constructions by combining two of the most common materials: reinforced concrete and steel. By understanding their behavior we can squeeze a mountain of used material with better results. They make it possible to take advantage of good mechanical properties of concrete in compression and steel in tension. One of the commonest types of composite structures is deck bridges with encased filler beams. These types of construction have been employed in Slovakia and all over Europe without any major change since the beginning of the 19th century. Several steel sections of modified shapes and dimensions were designed and tested in the Laboratories of the Institute of Structural Engineering at the Technical University in Košice. The main goal was to design and experiment with deck bridges made of various sections so as to maximise their cost-effectiveness by reducing the amount of steel consumed. Based on theoretical analyses, specimens were prepared in the laboratory, consisting of a variety of fully encased steel sections. It was cast into the prepared steel formwork placed on a fixed bearing plate so as to prevent deflection of composite beams during the concreting process.

Deflection calculation method on GFRP-concrete-steel composite beam

A calculation method was presented to calculate the deflection of GFRP-concrete-steel beams with full or partial shear connections. First, the sectional analysis method was improved by considering concrete nonlinearity and shear connection stiffness variation along the beam direction. Then the equivalent slip strain was used to take into consideration of variable crosssections. Experiments and nonlinear finite element analysis were performed to validate the calculation method. The experimental results showed the deflection of composite beams could be accurately predicted by using the theoretical model or the finite element simulation. Furthermore, more finite element models were established to verify the accuracy of the theoretical model, which included different GFRP plates and different numbers of shear connectors. The theoretical results agreed well with the numerical results. In addition, parametric studies using theoretical method were also performed to find out the effect of parameters on the deflection. Based on the parametric studies, a simplified calculation formula of GFRP-concrete-steel composite beam was exhibited. In general, the calculation method could provide a more accurate theoretical result without complex finite element simulation, and serve for the further study of continuous GFRP-concrete-steel composite beams.

A new model for composite beams with partial interaction

A theoretical formulation for the deflection of composite beams with consideration of interface slip is derived. The exact closed-form characteristic equations for composite beams with interlayer slip are derived for the boundary conditions. The equations also consider deflections and slips in the cross-section, leading to determinations of internal forces in the cross-section. Based on the research, practical applications are compared with the corresponding transformed section method. The results show that the theory is correct and convenient for solving problems of the analysis of steel–concrete composite box girders. Arbitrary cross-internal forces of the steel–concrete composite box girders are also obtained. The results provide a theoretical basis for the safe design of steel–concrete composite box girders.

A theoretical model of deflection for composite box girder considering interface slip

The present study investigated the effects of shear slip on the deflection of composite beams. A theoretical formulation of the deflection for composite beams considering interface slip was derived. Further, the exact closed form characteristic equations for composite beams with interlayer slip are derived for the boundary conditions. Numerical simulations of simply supported beam subjected to different load cases were conducted. The analytical solutions show an excellent agreement with the numerical results. Finally, the proposed method was extended to analyse the deflection of the different pitch of shear connector composite beam and to some extent validate the mechanical sensitivity.

Long-Term Behavior of Prestressed Composite Beams at Service Loads for One Year

The combined effects of creep and shrinkage of concrete and relaxation of prestressing tendons cause gradual changes in the internal forces and deflections of composite beams. However, most of the research work conducted on prestressed steel–concrete composite beams has focused on short-term behavior; research findings on the long-term behavior are scarce in the literature. For the wide-scale use of prestressed composite beams in civil engineering applications, the long-term behavior must be investigated. This paper presents an experimental program designed to examine the long-term behavior of prestressed composite beams under sustained load conditions for one year. The test program consisted of two prestressed composite beams and one nonprestressed composite beam. On the basis of the age-adjusted effective modulus method and energy principle, the creep stiffness matrix and the creep force matrix of prestressed composite beams were developed. A time-dependent analytical model is presented to predict the l...

Buckling of the steel component of a composite member caused by shrinkage and creep of the concrete component

AbstractThe effects of shrinkage and creep in conventional reinforced and prestressed concrete members are quite well understood, and the effects of these time‐varying characteristics of the concrete component on the deflections of composite beams and columns have received a good deal of attention in recent years. However, creep and shrinkage effects may cause a redistribution of internal actions within a composite member, which increases significantly the compression within the steel component, and that may therefore lead to considerations of the possible buckling instability of the steel component. This paper reviews the research work that been documented only quite recently, which has been undertaken on the potential for composite structures using a thin external skin with a concrete infill to buckle locally, and the possible instabilities that may arise in the negative moment region of a continuous composite beam, due to the shrinkage and creep of the concrete. This paper also puts the possibilities of these instabilities into a practical perspective, indicating where this unique type of steel buckling may need to be a design consideration in the most efficient use of steel–concrete composite construction.

A New Class of Distributed Sensors

A new class of distributed sensors is presented which can measure both the linear and angular deflections of composite beams. The sensor relies in its operation on a set of wires which are embedded off the neutral axes of the composite beams. The wires are arranged in a special manner which allows continuous monitoring of the deflection curve of the beam. The output signals of the wires are processed to determine the linear and angular displacements at critical discrete points along the beam axis. The theoretical and experimental performance of the sensor is presented in both the time and frequency domains. Comparisons are given between the experimental performance of the distributed sensor and that of conventional laser sensors in order to demonstrate the accuracy and merits of the distributed sensor. The results obtained suggest the potential of this new class of sensors as a viable means for monitoring the static and dynamic deflections of flexible composite SMART beams and plates.

ANALYSIS OF COMPOSITE GIRDERS WITH DEFORMABLE CONNECTORS.

In the case of a composite bridge beam, a perfect connection between the steel and concrete components exists only theoretically. In some types of connector design a rigid connection is achieved, others are more deformable and so a certain slip of the concrete deck with respect to the steel flange is inevitable. The problem is described as more severe when fewer connectors than the number required for full interaction are used. The influence of a deformable connection on the stress level and deflections of composite beams is investigated by the folded plate theory from which a versatile method of analysis is developed. Conclusions and recommendations for practical use of the method, derived from a parametric study, are also presented. (Author/TRRL)