Simulation Approach To Middling And Small Span Bridge Based On Detected Effective Prestressed

In the days of great development of traffic construction, a mass of middling and small span PC bridges were constructed. The existing PC bridges, after several years of operation, presented many potential safety troubles such as cracks and bridge duck subsidence. There are many reasons which can be summed up in the heavy loss of prestressing. These factors have quite unfavorable effects on the durability and normal use function of bridges and will directly threaten the structure safety of bridges. It is urgent to detect and evaluate the effective prestressing of PC bridges.As an important sub-research topic of the Western Project on Communication Science and Technology entitled "Research on the Prestressing Force Detection Technology for Large and Medium Prestressed Concrete Bridges", this paper makes a study of the influence of increasing prestressing loss upon the structure performance, based on the finite points' tested data obtained from the prestressed concrete bridges in service.According to the test method, this paper divides steel tendons into two groups:complex tendon and simple tendon.Complex tendon simulation uses prestressing lossσl1 andσl2 to compensate the gap between the theoretical prestressing value and measured prestressing value. As a result, the relation formula is given, which describes the effective prestressing variation along the tendon. Simple tendon simulation proposes three distribution modes:equideviate mode, equal ratio mode and composite mode.Equideviate mode simulates the measured data of effective prestressing by adjusting the relaxation coefficient of tendons; equal ratio mode simulates the measured data of effective prestressing by discounting the controlling force of tendons; composite mode simulates the measured data of effective prestressing by adjusting controlling force, relaxation coefficient and friction coefficient. After the simulating measured data are collected, they can be used to evaluate the safety and working performance of structures. A simulation study of the effective prestressing loss of a prestressed concrete continuous T-beam bridge demonstrates that the prestressing loss increase is the most important factor that influences the structure safety of prestressed concrete beams.This paper provides references for evaluating the structure performance of short and medium span prestressed concrete bridges in service.