The Demolition And Control Of Long Span Steel Arch Bridge

Arch bridge is widely used in highway and railroad for it has beautiful shape large pass-over capacity and can fully make use of material strength. Some highway arch bridges built in the past decades in our country, because of its small design load and low traffic capacity, now can not satisfy the demand of the modern transportation development and face the reality of being demolished and reconstructed. There are two ways used to demolish an old bridge: one is just exploding it; the other is tearing it down with a contrary sequence of building it . If the latter is chosen, the key to success lies in reasonable organization of design and construction scheme, control of construction course.Because an old bridge is in service for many years, its whole rigidity strength and stability all decrease in different degree and fatigue damage plastic deformation and local breakage and so on are included in single parts and connections .There are so many uncertain factors that make it more complicate in the structural analysis of whole bridge and make it hard to compute the bridge's internal forces and deformation precisely.Furthermore, demolishing an old bridge with a contrary sequence of building it lacks the specialized specification and papers as instructions, especially for large span bridges. These account for the necessity to do some specialized researches and quest in this field.We take the demolishment of Panzhihua 3002 Bridge (Old Ferry Bridge), an old steel arch bridge having a span of 180 meters built in 1966 as research object,which is operate without supporting frames. Combining with the experience of construction and theoretical analysis, draw up reasonable construction scheme , take rigorous measures in supervision and monitor to keep all kinds of index in the permitted range during the demolishment of the bridge, guaranteeing the steadiness and safety in the whole process of construction , and finally demolish the bridge in the control of perception successfully. All of these are included in this paper.On the base of theoretical analysis and summary of experience in demolishing the bridge, we think the suggestions, such as the main point of control in demolishing an old bridge the principle of system transformation , the standard and adjustment steps of load control and so on , will set an example for the demolishment of the same type of structure and provide references for relevant code enactment .