PARTIAL INTERACTION DESIGN OF COMPOSITE BEAMS

The main objective of this study is to provide advanced information about the behavior of stresses and effective widths for different cases of interaction. Four models of composite beams consist of steel I-Beam, light gauge and concrete slab reinforced with fine net of steel are tested. Two main parameters in the experimental work are taking into consideration, the thickness of slab and the degree of interaction which, is controlled by the number and diameter of shear connectors. The measurements include; the longitudinal strain distribution at different cross sections are measured by electrical strain gauges connected to the data logger, also the left and right slippage are measured by two displacement transducer connected to the data logger device. The central deflection of the composite beam is also measured by displacement transducer. All readings are taking at different load step measured automatically by the load cell connected by data logger.Non linear finite element analysis was performed using the nonlinear finite element program (Cosmos/m). Four types of elements were used in the nonlinear finite element model. Eight nodes solid element with three translations per node was taken to represent the concrete slab. Four nodes shell element with three translations and three rotations per node was used to represent steel I-Beam sheets. [Gap elements are used with different values of friction to simulate several cases of interaction degrees]. Very soft truss• element in space is a 2-node uniaxial element which has three translation degrees of freedom per node was used to overcome the disconnectivety problem between the steel I-Beam and reinforced concrete slab. The behavior of the finite element analysis showed a good agreement comparing with the experimental results.In order to examine the- effect of the line load, 12-models were used in the nwnericaI study to study the effect of the interaction degrees.Based on the experimental work and the numerical analysis studied in this investigation. The distribution of stresses at the top of slab at different sections in partially composite beams were found different than in the fully contact one. Therefore the following conclusions can be extracted:1- The value of the effective width in various codes IS very conservative and must be greater.2- Decreasing of partial interaction between the slab and I-Beam section leads to increasing the effective width of the slab, because less friction between the reinforced concrete slab and the I-Beam leads to the slab resist the normal stresses nearly separate.3- For the same steel section and same interaction degree, the increasing of thickness of slab leads to increasing the stresses on the top fiber of slab.4- Increasing the friction leads to decreasing ill the stresses of reinforced concrete slab and steel I-Beam.5- Increasing the friction leads to decreasing in the central deflection for steel I-Beam and the slippage between reinforced concrete slab and steel I-Beam.6- Increasing thickness of slab leads to decreasing in the central deflection for steel I-Beam and the slippage between reinforced concrete slab and steel I-Beam.7 - In case of 4-concectrated loads because of separation of beams the normal transversal stresses between the loads on edges of slab greater than at the center.8- Destribution of the effective width on slab along the beam , nearly uniform at line load case, but in case of 4-concectrated loads is variable.1- At experimental and theoretical work the width of the slab may be widely more than in this research, if the beam is separately tested.2- The same study may be done at several steel I-Beam sections and spans are needed to be studied.3- The relation between the friction (at this interface between steel and concrete) and the degree of interaction is needed to be studied.4- The case of continuous beam is needed to be studied