| Along with continuously rapid development of the national economy, the requirement is increasing to explore and apply large complex reinforced concrete structures in various fields of civil and hydraulic engineering. To ensure reinforced concrete structures reliability, serviceability and the efficiency, the technology of simulated model for reinforced concrete structures have been widely employed. Based on the tests of 28 reinforced concrete beams simply supported and the analysis of the reinforced concrete aqueduct with multi-longitudinal beams in the Central Route Project of Water Transfer from South to North, an in-depth research was conducted regarding the simulated theory in elastic-plastic stages and test key technology of simulated model for reinforced concrete structure. This research project was supported by the outstanding youth scientific fund of Henan Province (04120002300) and supported by program for innovation in university of Henan Province ([2004]294).(1) According to the appearing mechanism, the regularity of the elongation and the crack width variation of each crack, the statistical analysis principle for dividing crack patterns of reinforced concrete beams is elaborated and further defined. The statistical method was applied to analyze the number, average spacing, average width and maximum width of cracks according to the crack patterns. The crack feature corresponding to the checking of crack width in design procedure of concrete structures was determined, it can be expressed as that the crack continuously elongates to the neutral axis after cracking under the follow-up loading, because of the increase of tensile stress of reinforcement and tensile depth of concrete in cracked cross section.(2) Based on test data of reinforced concrete beams, methods for checking crack width of reinforced concrete beams in current codes were compared and analysis. The results show that the formulas in current codes are not all suitable for the reinforced concrete beams with large concrete cover or large size. The reason for the diversity of formulas lies in the different methods for calculating the effective influencing area of longitudinal tensile reinforcement. Therefore the factors of the thickness of concrete cover, the effective reinforcement ratio and the depth of normal section are needed to be considered in checking mode. The improvement suggestions are proposed for checking mode.(3) The effects of the thickness of concrete cover, the reinforcement and the depth of normal section on the crack spacing and crack width at the reinforcement level on the side surface of beam were analyzed. The method for calculating the effective tensile depth of cross section was proposed in which the diameter and the space of longitudinal tensile reinforcement are main variables. A model for calculating the average crack spacing to consider the coupling effects of cross sectional depth and effective reinforced coefficient is suggested. The improved model is proposed for calculating the maximum crack width. Comparing test and calculation results shows that calculation results of the formulas are better in accord with the test data and the formulas are suitable for the reinforced concrete beams with large concrete cover or large size.(4) The crack spacing and crack width at various heights in the tensile zone of reinforced concrete beams were measured systematically under several loading levels of serviceability state.The thickness of concrete cover, the reinforcement and the depth of normal section on the crack spacing and crack width at any position in the tensile zone of beam are analyzed. The relationships of crack widths at any position in the tensile zone and at the reinforcement level on the side surface of beam were studied. The method for calculating the ratios of crack widths between any position and the reinforcement level on the side surface was proposed.(5) The regularity of crack elongation of reinforced concrete beams was studied under every loading after cracking. The empirical formula is established by using statistical analysis of experimental data, which is about the relationship between cracking moment and the load level when main crack spacing stabilized. The variability of crack height is caused by the existing of the effective influencing area of longitudinal tensile reinforcement, according to analyzing the mechanism of crack elongation. The analytical solutions of the various periods for calculating the elongation heights of reinforced concrete beams are given out under the normal service stage, the theoretical predictions are better in accord with the experimental results. It can be used as reference to evaluate the working performance of reinforced concrete beam in service period.(6) Leading into the similitude principle of simulated model test of structure, the method was established for calculating the similitude ratio of flexural moment against cracking of the normal section of reinforced concrete flexural members. Based on the experimental results, the formula was proposed for calculating the plastic coefficient of sectional resist-moment in which the depth of normal section, the thickness of concrete cover and the ratio of reinforcement are main variables.(7) Combined with the similitude principle of simulated structural model test, according to the theory for calculating crack width and the statistical analysis of test data, the methods were established for calculating the similitude ratios of average crack spacing and maximum crack width of reinforced concrete beams respectively. The crack spacing and crack width of model test beams can be back analyzed to prototype beams. (8) The mechanical behaviors of prototype and simulated model of reinforced concrete aqueduct with multi-longitudinal beams were analyzed by 3D finite element method. The regularity of structural deformation and concrete stress of the aqueducts were studied, what influenced by the surface force instead of dead weight and the equivalent concentrate load or step uniform load instead of horizontal water pressure. The rationality of loading method for aqueduct model test was evaluated.(9) By the similarity ratios of simulated model to prototype in elastic and plastoelastic stages, the loading behaviors of simulated model are back analyzed to the prototype for the reinforced concrete aqueduct with multi-longitudinal beams. Utilizing the three dimension nonlinear finite element method, the bearing properties of the prototype reinforced concrete aqueduct under gravity load, water of design level and checking level are calculated. The calculation results are compared to the back analysis. The measurement reasonability of simulated model is proved on the cracking load and stresses of longitudinal-horizontal beams and side wall, the aqueduct vertical displacements and support counter-forces, which can be used to properly evaluate the normal service behaviors of prototype aqueduct after back analysis.(10) In view of the convenient for optimum design of large and complex structures, based on the calculation of the maximum crack width of reinforced concrete beam under serviceability, the theoretical formula is deduced for relating the nominal tensile stress to the maximum crack width of reinforced concrete beam. On the basis of statistical analysis of test data and reliability requirement, the simplified and practical formulas for calculating the nominal tensile stress are proposed.(11) Based on the three-dimensional solid finite element parametric model of reinforced concrete aqueduct with multi-longitudinal beams, controlling the stress of sidewall and floor according to the principle of sectional crack-resisting, adjusting the distance of horizontal and longitudinal beams according to the coordination of structural deformation, restraining the stress at mid-span bottom of horizontal and longitudinal beams with the nominal tensile stress, the optimization scheme with minimum self-weight are executed and the optimal section and arrangement of main forcing members are obtained. The reinforcements of the optimized aqueduct are arranged according to the internal force by three-dimensional beam-shell finite element numerical calculation. Compared with the design of prototype aqueduct, the optimized one shows the advantages of light weight, reasonable stiffness distribution, coordinated deformation and economical reinforcements.
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