Mechanical behavior of PPC member with a vertical joint and the influence of PC grout quality assessment

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In this study, in order to experimentally investigate the flexural and shear behaviors of the Partially Prestressed Concrete(PPC) structure with vertical construction joints, the bending strength tests are carried out for 45 beam specimens of size of 30cm×60cm×360cm. The parameters for the experimental work have been classified by the following factors ; 2 quality classes of the vertical joints, 35 and 70 N/mm^2 of compressive strength of concrete, the amounts of applied prestressing forces are 60% and 80% of the 0.2% offset yield strength of φ 13mm prestressing steel bar, the compressive strength of the grout cement mortar are 20,40,60 N/mm^2. However, the layouts of the ordinary reinforcing steel bar and that of the PC steel bar are also considered as the experimental parameters. In addition, the positions of a vertical joint in the beam specimens are classified into 3 places of followings ; constant bending moment area, or the center point of shear span, or the mid point between sup … More port and the center point of shear span.From the experimental results of bending strength tests, it is obvious that the results are greatly influenced by the testing parameters. The flexural crack stress and the flexural crack width are significant in the position of vertical joint. These experimental results are also remarkably influenced by the amount of applied prestressing force, and the quality of the vertical joint. Moreover, the flexural crack width exhibited larger value for a case of low compressive strength of PC grout cement despite the amount of applied prestressing force.The flexural crack tends to occur initially in the position of vertical joint located in the shear span. This flexural crack results in the reduction of the shear resistance of the joint concrete. The slippage at the joint can occur due to a mutual effect of the flexural crack and reduction of shear resistance. This phenomenon of slippage can become very remarkable in the case of low amount of applied prestressing force accompanied by the poor quality of vertical joint. The slippage eventually causes to the diagonal shear crack which will be further significantly developed in such case.As a result, a new design equation is proposed to analytically clarify the shear crack width which based on the fiber model concerning to the flexural crack, and the FEM of the compression field theory concerning to the shear crack width. Less