D Area Of ​​reinforced Concrete Members Based STMs And Shear Behavior Of Disturbed Stress Field Theory

D-regions are those parts of a structure in which there is a complex distribution ofstress and strain. Nowadays, the design principle of the two-dimensional non-trusscomponent such as deep beams with openings was given in China code for Design ofConcrete Structure (GB50010-2010), but it still lacks definite mechanical concept ofcalculations models and design formulas, which make the deep beams with openingsunsafe in practical engineering. Therefore, it is necessary to establish a rational calculationmodel based on experiments. The European and American codes mostly use theStrut-and-Tie Model (STM) to calculate the reinforced concrete members in D-regions.The STM has been introduced into design specifications of many countries for its clearload path. However it has not been adopted by our country’s design specification.Considering shear-slip damage, nonlinear finite element numerical analysis results basedon Disturbed Stress Field Model (DSFM) can better reflect the reinforced concrete shearstress process. Based on the above two theories, the overall objective of this study is toimprove the current approach for the design and analysis of D-regions by proposing amore complete design and analysis framework. The main work done includes:(1) After the boundaries of the D-Region, support conditions and the applied loadingshave been determined, the next step is to select the general shape of the STM to use indesign. For the types of D-Regions selecting a suitable shape is often a trivial task. Thedesigner is free to select the shape of the Strut-and-Tie Model. This paper presents thedesign process of the shape of the STM based on the Solid Isotropic Material withPenalization (SIMP) topology optimization theory. Considering the numerical instabilitiessuch as number of grid, Volume fraction, Penalty function and Filter radius, a new methodis proposed in this chapter.(2) Based on the stress complexity, the D-Region can be distinguished into simpleand complex portions. Simple D-regions will be taken as those portions of structureswhose behavior can be “sufficiently” analyzed by using simple nonlinear STM. Thesetypes of D-regions include most simple deep beams, corbels, stocky shear walls, and beam-column connections. The structural behaviors of complex D-Regions are, in contrast,considered to be “insufficiently” or “impractically” analyzed by a simple nonlinear STM.(3) Analysis of Simple D-regions beam using STM based on SIMP TopologyOptimization Theory. A nonlinear STM is adopted to predict the nonlinear structuralresponses of simple D-regions. To confirm the validity of the method, many strut-and-tiemodels including one model based on SIMP topology optimization method have beenestablished for a simply supported dapped beam with openings. And the schemescomparison and selection is conducted according to carrying capacity and the effectivecoefficient. The results show that the SIMP is feasible in the STM design procedure orframework to generate STM shape for effective structural performance design ofD-regions with the least reinforced volume ratio, the minimization strain energy andhigher carrying capacity.(4) Analysis of complex D-regions using nonlinear FEA based on DSFM. SomeReinforced concrete deep beams with web reinforcement, with shear span ratio, stirrupreinforcement ratio and longitudinal reinforcement ratio varying, were analyzed usingnonlinear finite element analysis program,VT2,based on modified compression filed anddisturbed stress field theory. In the mean time, the effect of strength of concrete and theopening location was also discussed. Research result reveals that with the increment ofconcrete strength and stirrup ratio, the shear capacity of beams increased. The researchresults by deleting the elements with low sensiticity number show that the location ofholes basically have no effect on shear capacity of beams, further proving the optimalityand the rationality of the topology optimization model.The overall objective of this study is to improve the current approach for the designand analysis of simple and complex D-regions. An expanded design and analysisframework will be proposed that aims to ensure good structural performance under serviceloads and due to overloads.