The Optimum Design Of Pile Foundation Beam Multi-lateral Wall Prestressed Aqueduct Based On System Reliability

The aqueduct is an overhead conveyance structures,used when channels leap valleys,rivers,roads(less than channels)or with another intersecting channels.It has a long history of development,domestic and foreign design and construction technology is more mature.With the construction of inter-basin water transfer project in China,large,extra large aqueduct to show the broad application prospects,structure type and the three dimensions of the aqueduct have undergone unprecedented changes.Compared with the past,conveyance Irrigation District’s aqueduct,the aqueduct in the South-to-North Water Diversion Project in China in recent years,in order to meet the large span large flow conveyance needs,showing Aqueduct width, height, cross-dimensional scale unprecedented,resulting in very different structural features:First,the structure type innovative and unique (such as the Aqueduct section have multi-side wall style, multi-stringer-style,rectangular fasting beam,etc.),The second is the lateral deflection of the great Aqueduct and lateral wind stability can not be neglected,design theory become lag and is not appropriate;Third,the great Aqueduct use of three-dimensional prestressed structure to improve its carrying capacity,to bear the load of the aqueduct huge water use of Pile Bearing on the soft base.The above changes make the new aqueduct is facing many new problems in terms of design, construction,operation and management.Engineering design mainly uses a single component of the safety factor method,the structural system is decomposed into many single-component,respectively,according to the uncertainty factor of safety guidelines designed to ensure the safety of a single component,which does not correspond to the design of the structure and its actual situation in the following areas:(1) Project runtime is actually the entire structure of the system to face the outside world to encounter the occasional role(especially such as floods, earthquakes, etc.),the safety of a single component can not guarantee the security of the entire structural system.To improve the bearing capacity of the component may not be able to improve the bearing capacity of the system as a whole.(2) Structure in the design,construction and operation will be influenced by many uncertainties(such as the variation of load,material properties variation,working conditions variation,etc.), especially in the aqueduct new type,new technologies and new method. We can not take into account the above uncertainties in the design of the safety factor method.In view of the above, in this paper,the South-to-North Water Diversion Project use of pile beam multi-the side wall prestressed concrete aqueduct to carry out the following aspects:(1) Through studying the vertical and horizontal offloading of large wide span ratio Aqueduct structure under deformation compatibility conditions,we get water load distribution ratio between vertical and horizontal beam;(2) Using the results and treating factors which affect the structural system safety as random variables at the same time to carry out the reliability of the aqueduct structural optimization study.the The optimize results obtained under the premise of reducing construction costs.improving system reliability and the reliability level of consistency between component(on behalf of the main failure mode);(3) The aqueduct structure system is divided into"Aqueduct+slot pier"and"the pile cap+pile"two modules, using ansys three-dimensional finite element to model. Analyzing structural static of Aqueduct structure system before and after optimization to confirm the rationality and practicality of the aqueduct optimization results.The proposed method can provide valuable reference for improving design theory and methods of such works, and operating practice of engineering practice.