Research On Design Theory Of A New Type Of GFRP-Concrete Composite Beam

As FRP manufacturing process of composite material matures gradually,the advantages of FRP materials have also been recognized by more and more people.FRP materials have been widely used in the field of civil engineering.Since the price of FRP materials is higher than traditional materials,the composite structure of FRP and concrete begins to be studied.This paper presents a new composite beam with the combination of GFRP and concrete.The GFRP grid is adopted for the upper side;GFRP clapboard is used for the central part to prevent the concrete from flowing to the lower part:GFRP box structure is employed for the bottom.The GFRP profile and concrete can work together through shear connectors and sticky sand contact.This combination can take full advantage with structure of the two materials,and is highly economical.During construction,GFRP profile can be used as a permanent form that can speed up the construction progress.In this paper,theoretical calculations and numerical analysis of GFRP profile and concrete composite beam structure are conducted and some useful conclusions have been drawn.The main findings are:By referring to plenty of FRP relevant literature and summarizing previous experience,a new GFRP profile and concrete composite beam structure is proposed.The structure puts the advantages of concrete and GFRP materials into full play,and it is also economical.Stress and strain analysis is conducted for elastic and plastic stress of this cross-section composite beam.A formula of flexibility anti-bending flexural capacity and a formula of ultimate anti-bending flexural capacity are established.Formulas for calculating the shear stress and axial force are established through differential formulas for calculating the shear stress and axial force of connection interface are derived with the example of balanced load.After analysis of cross-section parameters of the three failure modes,it is found that during the cross-sectional design,try to make the position of the neutral axis right at the bottom of the concrete.In this way,GFRP profile can be fully utilized,and the structure can have a higher carrying capacity.Finally,analysis of the whole flexural process of beam is conducted with theoretical derivation and numerical simulation.Bending moment-deformation curve of composite beam is obtained,with coinciding results of theoretical analysis and finite element numerical simulation.As can be seen from the curve,when making structural design,the safety factor is considered:ultimate bearing capacity of the structure is higher than the design value by 23%.In addition,when making ’balanced-reinforced failure’ structure design ’over-reinforced failure ’ occurs in the actual structure.Before the damage of the structure,there is a certain warning stage,which meets the requirements of ductile failure.