Study On Bending Performance Of Micro-Steel Fiber High-Strength And Light-Weight Aggregate Concrete Beams

In recent years,with the rapid development of the construction industry,building structures have gradually developed into large span,super high-rise and alternative forms.In this trend,the industry has increasingly strong requirements for the performance of building materials.As a representative of lightweight and extreme toughness building materials,fiber lightweight aggregate concrete has a broad application space.Due to the mature preparation technology of steel fiber and its wide range of applications,this article intends to incorporate micro steel fiber into lightweight aggregate concrete to prepare micro steel fiber high-strength light aggregate concrete(hereinafter referred to as MFHC).At present,scholars’ research on MFHC is mostly focused on the basic mechanical properties of materials,with minor research on structural components.Therefore,based on the study of the basic mechanical properties of MFHC with different proportions,this paper seeks out a better mix ratio and studies the bending resistance of beam members.The cracking load,ultimate load,midspan deflection,short-term stiffness,and stress-strain relationship between tensile reinforcement and compressive concrete during the failure process of the test beam were recorded and analyzed.Based on these data,the impact of different fiber content,reinforcement ratio,and concrete matrix strength on the flexural performance of the MFHC beam in the test beam was analyzed and verified using Abaqus finite element software.The main research content and results of this article are as follows:(1)The optimal content of steel fibers in MFHC was obtained through the basic mechanical properties tests(compressive performance,splitting tensile performance,and elastic modulus tests)of MFHC specimens.The research shows that the compressive strength is the highest when the fiber volume fraction is 1.0%,and the splitting tensile strength is the highest when the fiber volume fraction is 1.5%.The experimental results were fitted to obtain a formula for calculating the compressive strength and splitting tensile strength of MFHC with respect to the fiber volume fraction.(2)Through the flexural performance test of MFHC beams,the failure process of the test beam was analyzed,and the cracking load and ultimate load data of the test beam were obtained.The strain changes of tensile reinforcement and compressive concrete,the development of midspan deflection,and the change of crack size of the test beam were summarized.The effects of different steel fiber volume fraction,reinforcement ratio,and concrete matrix strength on the flexural failure of MFHC beams were analyzed.The results show that only increasing the volume fraction of steel fiber increases the ultimate bearing capacity of the test beam significantly;when only changing the strength of the concrete matrix,the increase in the ultimate bearing capacity of the test beam is tiny.By comprehensive comparison,it is more reasonable to use 1.0% volume admixture for concrete flexural members.Adding steel fiber can increase the cracking load of components and reduce the crack width,but the number of cracks is greater than that of ordinary lightweight aggregate concrete beams.Adding steel fiber can reduce the deflection of components,and the maximum deflection can be reduced by 62.5% under the same load condition.Therefore,adding steel fiber has a significant effect on limiting the deformation of beams.(3)Based on the basic mechanical analysis principles and the research results of existing scholars,the short-term stiffness,failure strength,and crack width of MFHC test beams are analyzed theoretically.According to the specifications,the short-term stiffness calculation formula and the crack width calculation formula are modified,and the corrected theoretical calculation formula is given.(4)Using Abaqus finite element software,numerical modeling and analysis of MFHC beams were carried out,and the simulated values were consistent with the experimental values,which could provide a reference for additional research on the flexural performance of MFHC beams in the future.