Space Prestressed Friction Loss And Parametric Studies

Prestress losses occur while prestress is applied with strand stretching in prestressed concrete structure, among which the frictional prestress loss between the perstress strand and strand duct takes large proportion. Although the calculation method for frictional loss is clearly presented in the state bridge specification, it is found that the calculation formulas recommended in the specification are deduced under the condition of plane curve alignment of prestress strands, without considering the alignment of strands in space curve. Therefore, it inevitably brings certain blindness to the calculation for attrition loss and lack of theoretical foundation. In addition, the friction factor μ and deviation factor for strand duct profile k in the formulas are to be valued with reference to the listed data in the specification that do not reflect the change of bridge structure and the layout of strands, which consequently brings errors to the result of calculation.In this paper, theoretical formulas of frictional loss for prestress strand in space curve are deduced with spacial differential equation and verified with real bridge test. And the test method of parameters μ, k is put forward. The calculation results show that the value of frictional loss with the method of space analysis is more accurate and closer to the test value than that with the method in the specification. Moreover, the experiment results indicate that the test values of parameters μ, k are higher than that recommended in the specification.