Study On Optimal Design For The Structure And Section Of The Bridge-type Shield

With China’s demand for the speed of the railway and the highway, the original crossing has seriously hindered the development of their. And it is very easy to bring safe hidden trouble. Changing the crossing roads into the overpass roads has become a trend. Underpasses bridge is a kind of structure under earth.It has provided a new road across roads and railways,in the case of the normal operation of the upper roads and railways. And relative to the upper structure, it covers an area of less, costs lower.The underpass bridge generally adopts jacking construction technology, and general jacking method requires the train running speed should not exceed30to40km/h. It obviously can’t satisfy people’s pursuit of high speed. However, the bridge type shield uses the basic principle of shield and gradually developes in recent years. It will not restrict the three-dimensional above the vehicle’s speed when jacking, and it have good construction safety, therefore it is widely used in road and rail three-dimensional engineering.The bridge type shield body is a kind of steel frame structure. Shield body includs girder, side columns, middle columns, and the transverse beam, the longitudinal beam structure and fittings, etc. Son of shield cuts soil and takes upper loads. Framework and shield shell form the overall enclosure system, supporting the upper lateral loads and lateral earth pressure; the hydraulic propulsion system provides the underpass bridge and shield motivation forward. The reverse system is used for balancing jacking force, preventing advance too quickly.Because the bridge type shield is only gradually developed in recent years, as a new construction technology, the study is not very thorough, and many problems need to be solved. For its design we generally adopt the method of experience, combined with similar engineering data, and simple calculation are used to get the working drawing. Therefore, the design tends to be conservative. For this kind of temporary bracing structure, the usage of steel is too big, and it is difficult to reuse, causing a big waste.This topic, systematically introduces the basic design method of shield,combined steel structure design principle, including load statistics, load condition, the design of the main girder and pillar design, etc. Through has completed a project example, check its safety. And I find the structure size is too conservative, not making component be used adequately. Finally, I put forward that the component of the structure and size should be optimizated, make the internal force of basic close to the allowed stress, and give full play to its effect. Buckling ai alysis was carried out on the component by use of ansys software to verify the structure size meet the requirements, and the structure stability is good.