Carrying Capacity Analysis Of Composite Beams Of Steel And Concrete

Composite beams of steel and concrete are new type structures in which the steel beams and the concrete board are integrated by shearing force connectors to take advantage of the respectives of tension and compression.As this composite structures have merits of both steel and concrete and overcome their shortcoming,so its performance is more than a single structure made of superior materials,notable benefit of technology and economics have been achieved.The first investigation of composite beams of steel and concrete began in the early 20th Century.Looking back at the course of development of the composite beams of steel and concrete,the research and application of composite beams has been several decades of history. Though composite beams have been applied and researched extensively, it is not enough in investigating and experimenting the composite and carrying capacity especially of the vertical shear of cross-section with respect to reinforced concrete structures and steel structures.The composite beam section in our Steel Structure Design Code(GBJ50017-2003) has been established by learning from foreign experience,combining our material and structural properties and on the basis of the results of experimental studies of China Engineering. The calculation theory- Flexibility theory and Simplified Plastic theory is basically following the design specifications of the foreign theory.without considering the concrete haunch in calculating the moment of resistance and the whole concrete portion in calculating the resistance to vertical shear.Such simplification is conservative for composite beams with haunches especially with deep haunches.In this paper,in the light of above-mentioned problem research in the stress condition and failure of composite beams is done first,and then a new method is proposed through theoretical analysis based on properties of the composite beam. In the elastic analysis of composite beams,the concept of changing section is given up.Based on composite beam itself and under the premise of the basic assumptions,the formulas to the resistance in elastic state and to the resisting shear that considering the contribution of the concrete haunch on the action are then given by mechanical analysis. These formulas accord with the designer's habit in the form and consider the influence of the concrete haunch. And the precision is superior than the conversion section method.In the plastic analysis of composite beams,it is proposed that the composite beam arrives at the ultimate limit states of capacity when the stain of the outside edge of the cross-section reaches the ultimate stain.The formulas to the moment of resistance on the action of the pure moment and to the resisting shear considering the contribution of the concrete haunch on the action of...