Research On The Flexural Performance Of Composite Concretebeam Partially Reinforced By Steel Fiber With High Fiber Volume

Because the ordinary steel fiber is of high slender ratio, its volume content whenmixing with concrete is often less than2%. By this time, the enhancement of steel fiberto the concrete is not obvious. When such volume content exceeds2%, the steel fibercan hardly evenly distribute in the concrete and the steel fiber reinforced concrete is ofpoor workability, which leads to the reduction of the strength of such concrete. Thepaper proposes a fracture mechanics based research method on a fiber-modifiedcement-based composite, and achieves the high volume content of steel fiber inconventional steel fiber reinforced concrete which is difficult to be achieved in the past.The paper also obtains a new material, namely extra-fine steel wire fiber reinforcedconcrete, which is of both high toughness and strength, and further proposes a newstructure, namely composite concrete beam partially reinforced by extra-fine steel wirefiber with high fiber volume according to the characteristics of the tensile/compressivestress field in beam structures through the method of material structuring. Such aproposed structure fully employs the properties of all materials and improves suchmechanical properties as crack resistance, bearing capacity and ductility of thestructure, which can promote the development of beam structure in its light weight andlong span.The paper develops the new extra-fine steel wire fiber reinforced concrete,designs the new composite concrete beam partially reinforced by extra-fine steel wirefiber with high fiber volume and then conducts an experimental research and finiteelemental analysis on the flexural performance of the composite beam.①Based on the mechanisms in fracture mechanics, the paper achieves the highvolume content of steel fiber in steel fiber reinforced concrete and develops the newextra-fine steel wire fiber reinforced concrete by normal concrete preparation technics.The volume content of steel fiber can reach6%in the steel fiber reinforced concretewhich is of better workability and mechanical properties.②When the said volumecontent is no more than6%, the strength (bending strength and flexural-tensilestrength), Young’s modulus and the roughness of the steel fiber reinforced concreteincrease as the volume content of the steel fiber increases. When the volume contentreaches6%, comparing with ordinary concrete, the compressive strength of the steelfiber reinforced concrete is improved by33.3%, its flexural-tensile strength by114.6%,elastic modulus by11.8%, first crack strength by41.2%, equivalent bending strengthby293.6%and bending toughness by184.6%. Thus, extra-fine steel wire fiberreinforced concrete is a high-performance cement-based composite material.③Basedon fracture mechanics and material structuring design method, the paper proposes thenew structure of composite concrete beam partially reinforced by extra-fine steel wirefiber with high fiber volume.④the research on the flexural performance of thecomposite concrete beam partially reinforced by extra-fine steel wire fiber with highfiber volume shows that the crack resistance, bearing capacity, stiffness and thedevelopment of cracks of the new structure are significantly improved: its crackingload improved by107.1%(which equal to the working load of ordinary reinforced concrete with the same design), yield load by44.9%and ultimate load by42.0%; thesteel fiber reinforced concrete layer can jointly work with reinforcing steel in a greaterdeformation range, and the stress of the steel distributes more homogeneous. When ina loading process, the emergence of cracks in the structure is delayed in comparisonwith that in an ordinary reinforced concrete beam with low speed of development inheight and width. And the flexuralrigidity, deformation performance and ductility ofthe new composite structure are significantly improved. When the deformation of thetest beams is taken as control condition (L/300of middlespan deflection), the bearingcapacity is improved by47.6%.⑤By measuring the stress-strain relationship of theextra-fine steel wire fiber concrete with high fiber volume, a numericalsimulationwasconducted by using the finiteelementsoftwareANSYS to analyze the new compositebeam. The results obtained are consistent with the above experimental results, whichproves the superior mechanical properties of the composite beam.The paper, based on the combined design theory of fracture mechanics andmaterial-structuring method, proposes a new structure of composite beam which isdesignable and worth exploring.