Force Analysis Of Web Plate And Research On Prestressing Loss Of The Prestressed Concrete Box Girder Bridge

The prestressed concrete box-beam bridge is widely used with its special advantages of the good comprehensive performance, high structure stiffness, little deformation and good earthquake resistant performance.At present, the triaxial prestressing structure is used for prestressed concrete continuous box-beam bridge in most cases, which leads to loaded force of box-beam web more complicated. If the principal tension stress of box-beam web is controlled improperly, the principal tension stress will exceed allowable value and cause the inclined crack of the web. The inclined crack of web is the main cause of middle and down deflection of box-beam bridge span. If there is more cracks, the rigidness becomes less and the middle and down deflection of span is more serious; and if the middle and down deflection of span becomes more, the crack degree is more serious. Moreover, the inclined cracks affect the appearance, bearing capacity, service life and traffic safety to a large extent. The cause of prestress loss is analyzed and investigated during a long time. The prestress loss directly influences the crack resisting property and the deflection of the structure, especially the vertical prestress loss can directly influence the appearance of inclined cracks of the web. Therefore, the calculation analysis of principal tension stress of box-beam web and the investigation of prestress loss has an important engineering meaning.This paper makes comprehensive analysis on prestress loss, especially for vertical prestress loss in theory. The theoretical calculation formula of principal tension stress of the web is discussed and the specific engineering examples are used for the theoretical calculation and analysis of principal tension stress of box-beam web. Based on the south bank bridge of Hubei Suiyuezhong Hanjiang Grand Bridge, the MIDAS/Civil finite element software is used for detailed stress calculation of box-beam web in each construction stage and operation stage of the south bank bridge and investigation of stress changing principal in each working condition to get the useful conclusion. This paper also analyzes the unfavorable influence on loaded force of web from consortion, creepage and prestress as well as provides relative measures and design suggestions. Finally, the temperature field simulation model of bridge is founded according to the actual surrounding temperature field distribution condition of bridge. The finite element software is used for calculating the loaded force state of box-beam web in different temperature modes and investigating the influence on prestress loss from temperature load. The result provides reliable data to ensure the construction quality for bridge construction control. Meanwhile, it has guiding significance on design and construction of prestressed concrete box-beam bridge.