Analysis And Calculation Of The Whole Process Of Reinforced Concrete Beam Strengthened By Increasing Section Method

The enlarged section reinforcement method has the advantages of simple process,rich experience and reliable stress,and is widely used in reinforced concrete reinforcement engineering.Reinforced concrete beams,as one of the most basic load-bearing members in building structures,adopting the reinforcement method with increased cross-section has the characteristics of safety,reliability,good durability,and high acceptance by the owner.Therefore,it is often a priority reinforcement method,which is widely used in engineering practice.The enlarged section reinforcement method is widely adopted by various design and construction units,but there are still many problems in design theory and engineering practice:①The corresponding provisions of the reinforcement design code The content and content are not exhaustive.There are no clear rules for the analysis and calculation formulas of different enlarged cross-section reinforcement forms and different reinforcement yield states,which restricts the reinforcement forms and design calculation formulas that can be adopted in engineering practice;② Reinforced concrete beams before reinforcement In the non-limit state,the reinforced concrete beam after reinforcement is in the state of secondary stress.It is necessary to consider the initial strain in the non-limit state,the strain lag in the secondary stress state,and the stress lead.The research on analysis is not systematic and comprehensive;③When the reinforcement situation and the stress state are complicated,the theoretical analysis and manual calculation are difficult to perform,and there is no simple and convenient numerical simulation method.This paper intends to conduct a comprehensive and systematic analysis and research on the whole process of the reinforced concrete beam strengthened by the increased cross-section of the normal section bending,thus forming a more systematic and more complete calculation theory,providing a comprehensive numerical analysis program to ensure reinforcement The quality of design and construction solves the practical difficulties of reinforcement analysis and provides a better theoretical basis and reference for reinforcement design.The main research contents are as follows:(1)Through Study and analyze the mechanical performance of reinforced concrete beams with rectangular section under non-limit state.Compile a numerical program to simulate and analyze the stress distribution of the concrete in the compression zone under the non-limit state,study the change trend of the equivalent coefficient and the concrete of the compression zone,and give the fitting formula;The calculation formula of the flexural bearing capacity of the beam under different steel bar yield states;two typical non-limit calculation methods are given and verified by calculation examples.(2)Study and analyze the mechanical performance of T-shaped reinforced concrete beams under non-limit state.The compression of the T-shaped reinforced concrete beam is divided into two parts:the beam rib part and the flange part,and the beam rib part is calculated according to the rectangular beam method;the numerical simulation program suitable for the T-shaped beam compression flange is compiled and studied The changing trend of the equivalent coefficient and the concrete of the flange compression area is given,and the fitting formula is given;referring to the calculation method of the rectangular beam,the calculation formula of the bending capacity of the T-shaped reinforced concrete beam is given.When the T-shaped beam undergoes bending deformation,due to the shear lag effect,the stress and strain on the wing plate are no longer evenly distributed within its width.Using ABAQUS to carry out numerical simulation analysis of T-shaped reinforced concrete beams,to study the influence of shear lag effect on T-shaped beams under bending moment.(3)The whole process of the reinforced concrete beam strengthened with an enlarged section is theoretically analyzed,and a hand-calculated calculation formula is derived.The initial stress state of the original reinforced concrete beam before the reinforcement is analyzed,and the calculation formulas of the steel bar strain of the original beam,the concrete strain at the top of the compression zone,the strain at any point in the section,the relative limit of the original section and the height of the compression zone;Analysis of stress leading and strain lag under the condition of secondary stress;theoretical analysis of the stress state of the reinforced beam with increased cross-section at the bottom,increased cross-section at the top,increased cross-section at the bottom and top;According to the different steel bar yield conditions,the calculation formulas of the bending capacity of the normal section of the reinforced beam with increased section under the condition of the second load are derived respectively.(4)Compile a numerical simulation program to perform a numerical analysis on the whole process of the reinforcement beam.Summarize the basic principles,calculation process,numerical analysis process,and different analysis conditions of the numerical simulation program,and give the analysis flow chart;introduce the visual interface and basic operation process of the preparation program.The compiled program can provide a more convenient and quicker analysis method for the calculation of the stressed state and bearing capacity,and can solve more complex problems that are difficult to be solved by theoretical analysis and calculation formulas.