Response Of Composite Beams Research Articles

Responses of composite beams with high-performance fiber-reinforced concrete

This investigation focuses on the moment resistance of a composite beam with high-performance synergized fiber-reinforced concrete (HPFRC) by performing analytical and experimental works. At first, the HPFRC containing 1.0 vol% long hooked steel fibers blended with 0.5 vol% short smooth steel fibers was explored to produce an important synergy in direct tension. The synergy coefficients according to tensile parameters of the HPFRC were ranked as follows: strain capacity < peak tensile stress < peak toughness. Next, six composite beams consisting of normal concrete and HPFRC were tested under three-point bending. The HPFRC placed at an extreme compressive/tensile zone generated a favorable effect on enhancing moment capacity. Finally, an analytical model using section analysis was proposed to estimate the moment resistance of the composite beam with HPFRC.

Domain-boundary element method for forced vibrations of fiber-reinforced laminated beams

A domain-boundary element method for forced vibration analysis of fiber-reinforced laminated composite beams is introduced. Utilizing static fundamental solutions as weight functions in weighted residual statements, governing partial differential equations of motion are reduced to a system of four coupled integral equations. Domain discretization leads to a system of ordinary differential equations in time, which is solved by the Houbolt method. Developed procedures are verified through comparisons to analytical solution for isotropic beams. Parametric results illustrate elastodynamic responses of composite beams subjected to various loading types. It is shown that angle-ply laminates undergo higher displacements compared to cross-ply laminates.

Low velocity impact analysis of beams made of short carbon fiber/carbon nanotube-polymer composite: A hierarchical finite element approach

ABSTRACTThe low velocity impact response of beams made of carbon nanotube (CNT)/short carbon fiber (SCF)-reinforced polymer is investigated based on a hierarchical finite element approach. First, the random distribution of CNTs into the polymer matrix is modeled using a three-phase representative volume element (RVE); and the elastic modulus and density of CNT-reinforced polymer are predicted. In the RVE, the interphase region formed due to the interaction between CNTs and the matrix is considered. Then, reinforcement with SCFs is considered, and the elastic properties of SCF-CNT-polymer hybrid composite are obtained. Finally, the low velocity impact response of composite beams is analyzed.

In-plane shear compression behaviour of steel-glass composite beams with laminated glass webs

Steel-glass composite beams with the combination of glass webs and steel flanges are known to be able to attain good ductility in contrast to pure glass panels. As a concentrated load is introduced away from the middle of the beam span, its resultant stress concentration can induce shear compression failure on the glass web which is distinguished itself from flexure failure as reported in the literature. This paper presents an experimental study on the in-plane shear compression behaviour of composite beams with laminated glass webs. Distinct failure mode related to load induced edge delamination traces on the glass web is reported. Based on the test results, the distribution of acting strains and stresses within the composite beams is plotted. The formation of inclined cracks on the glass web is justified as the stress trajectories are prone to bend to form a diagonal tension stress state. It is shown from the response of composite beams that the strength and elastic stiffness of composite beams are improved when the adhesives with better mechanical properties are used. Afterwards, it is shown that the strengths of test specimens are greater than these of counterpart glass stabilizing fins or stiffening fins due to the flexibility of adhesive joining. Finally, the test strengths have been evaluated based on the edge delamination traces and the equilibrium of the energy dissipation of proposed mechanism. It is demonstrated that the proposed mechanism in contrast to referred formulae is able to give a better prediction of strength.

Vibration Analysis of Steel-Concrete Composite Box Beams considering Shear Lag and Slip

In order to investigate dynamic characteristics of steel-concrete composite box beams, a longitudinal warping function of beam section considering self-balancing of axial forces is established. On the basis of Hamilton principle, governing differential equations of vibration and displacement boundary conditions are deduced by taking into account coupled influencing of shear lag, interface slip, and shear deformation. The proposed method shows an improvement over previous calculations. The central difference method is applied to solve the differential equations to obtain dynamic responses of composite beams subjected to arbitrarily distributed loads. The results from the proposed method are found to be in good agreement with those from ANSYS through numerical studies. Its validity is thus verified and meaningful conclusions for engineering design can be drawn as follows. There are obvious shear lag effects in the top concrete slab and bottom plate of steel beams under dynamic excitation. This shear lag increases with the increasing degree of shear connections. However, it has little impact on the period and deflection amplitude of vibration of composite box beams. The amplitude of deflection and strains in concrete slab reduce as the degree of shear connections increases. Nevertheless, the influence of shear connections on the period of vibration is not distinct.

Analytical Solutions for the Viscoelastic Response of Composite Beams Including Partial Interaction

This paper addresses the issue of the deformations that occur in composite steel-concrete beams caused by the quasi-viscoelastic effects of creep and shrinkage of the concrete slab, and in which the effects of partial shear interaction (PI) at the interface between the slab and the steel joist are included in the analysis. By making recourse to an algebraic representation of the viscoelastic response of the concrete, the formulation in this paper leads to a unique and useful solution of the problem in closed form, which follows from the establishment of a second order linear differential equation. The solution therefore does not require a discretisation along the beam as is usually required for numerical techniques, but only one discretisation in the time domain, and furthermore the resulting solution is generic in the sense that it may be applied for a variety of loading and restraint conditions. Specific solutions, which are validated against a numerical technique reported elsewhere, are presented for the cases of a simply supported beam, an encastré beam and for a propped cantilever.

Closed-form solution for the cross-section warping in short beams under three-point bending

The transverse shear behavior of composite beams can be critical and therefore must be properly represented by the various models of structures usually employed either to predict their behavior or to identify experimentally their properties. In this work, a simple analytical approach based on higher-order theories is proposed that accounts for the cross-section warping in beams. Then the solution of a beam under three-point bending is solved and the accuracy of both displacement and strain distribution predictions is shown through comparisons with the FE analysis results. In this formulation, the cross-section locking at mid-span is ensured owing to the dependence of the transverse shear strain upon the position along the beam axis. Eventually, comparisons with experimental measurements demonstrate the ability of these simple analytical solutions to grasp the main phenomena which control the response of composite beams under three-point bending loading, i.e. the arising of transverse shear.

Response of composite beam under low-velocity impact of multiple masses

A theoretical method is presented to analyse the low-velocity impact dynamics of a system which consists of a laminated beam and multiple impactor masses. The contact forces between the beam and the impactors are treated as the internal forces of the system. The beam displacement field is defined using a higher-order shear deformation theory and the interaction behween the beam and the impactor masses is described with the modified Hertzian contact law. The potential and kinetic energies of the system (the energies associated with the beam and the impactors) are formulated in terms of the displacement field of the beam and the modified contact law. These are substituted into the Lagrangian equation to derive the governing equations of the system, which are nonlinear second-order differential equations. Simple polynomials are assigned to the shape functions of the beam in order to satisfy arbitrary boundary conditions. The present method is general in that it allows the impactors to be of different masses striking the beam with different initial velocities at arbitrary locations on the top surface of the beam. There is no limitation on the number of impactors that can be considered.

Response of Composite Beams to an Internal Actuator Force

Shape memory alloy hybrid composite materials have demonstrated numerous control capabilities. One such capability is the controlled bending of structures. In this paper the response of a cantilevered beam to an internal actuator is examined. The modeling of the compressive force exerted by the induced strain of the actuator on the beam is discussed. The results obtained from treating the force as an external follower force are presented. The response to an internal force such as exerted by an internal shape memory alloy actuator is quite different from that produced by loads due to sources external to the beam. Contrary to normal expectations such an internal force although compressive does not produce any buckling tendencies or any other instabilities in the beam. This principle which is already in use in the design of civil engineering structures is discussed in detail. If the actuators are embedded off of the neutral axis, then due to the eccentricity the beam bends, but again without any buckling tendency. The experimental results obtained for this configuration are also presented.