Study On Flexural Behavior Of Composite Reinforced Concrete Beams With TRC Permanent Formwork

The traditional building formwork has the disadvantages of cumbersome supporting,dismantling of molds,low turnover and large occupation of labor.Therefore,the overall cost is high.In order to avoid the shortcomings above,using new materials as a permanent formwork is an alternative.Textile Reinforced Concrete(TRC)is a composite material that lays fiber woven mesh in fine concrete.The fiber woven mesh is light and corrosion-resistant.The fine concrete has high fluidity and self-compacting resistance to segregation,impermeability,carbonation resistance,freeze-thaw resistance.Therefore,TRC structure has high strength,crack resistance,good durability and strong designability.Using it as a permanent formwork has broad development and engineering application prospects.This paper mainly studies the interface performance between TRC formwork and post-cast concrete,the flexural behavior of different forms of composite reinforced concrete beams with TRC permanent formwork under static load and the bending size effect of different sizes composite beams withr the same formwork form.In the interface performance study,a total of 14 groups TRC formwork prefabricated cracked trabecular beams with size of 80×100×400mm were cast,mainly to study the impact of different interface treatment methods,interface agent types,TRC formwork thickness,chopped fiber dosage and distribution ratio on interface performance.In the bending test of composite beams,a total of 9 test beams with three different geometric sizes were cast.The bending properties of composite beams with the same size and different formwork forms,the same form and different size formwork are compared and studied.The results of the interface test found that different interface treatment methods can improve the ultimate bearing capacity of the specimen,but regardless of whether the interface has been treated,the interface bonding strength is sufficient relative to the strength of the TRC formwork.The interface is well bonded.The results of the four-point bending test show that under the condition of good interface bonding,the use of TRC permanent formwork can improve the cracking load,yield load and ultimate load of composite beams,inhibit the development of cracks in members and improve the bending stiffness of specimens.The ultimate displacement of the specimen is reduced,but the ductility of the composite beam is reduced.Composite beams with U-shaped formwork are superior to composite beamswith single-plate formwork in terms of convenience in casting and overall mechanical properties.Through the analysis of the four-point bending test results of the same formwork and different sizes of the test beams,it is found that in the size range of this experimental study,whether it is the composite beam specimen or the contrast beam specimen,there is no obvious size effect in the nominal bending moment,including nominal cracking moment,nominal yield moment,nominal limit moment,bending strength,equivalent deflection and ductility coefficient,but there is a size effect in the bending strength of composite beams with single-plate formwork.Finally,the theoretical analysis of the static load test of the composite RC beam with U-type TRC permanent formwork is carried out,and the calculation formula of the normal section flexural bearing capacity of the U-type formwork composite beam under static load is deduced.