Span Pc Box Girder Crack Analysis

Long span PC box girder bridges have been widely used in middling span bridges in highway engineering as they possess many merits, such as huge torsion stiffness, high section efficiency. Bridges of this kind are designed according to fully prestressed concrete theory, and tensile stress is allowed to exceed allowable stress during construction and service. Whereas, cracks as usually appear in concrete structures, were also found during service in bridges of this kind. For there are unpredicted complications during construction and service, cracks spontaneously come up.This thesis takes thin-walled box girder theory as basis, discusses many indexes generated by the external load in detail i.e. internal force and stress, and every factor leading to the concrete cracks. It speculates the reason why the Sanmenxia Yellow River Bridge cracks, by the comprehensive analysis from construction to current step.Through analyzing the surveying result and factors leading to cracks, it brings forth some details which should be taken care in future designing and constructing this type of bridges, such as computing theory of load transverse distribution factors, shear lag's affection on web normal stress and principal stress.