Research On Static Characteristics Of Cooperative Cable-stayed And Rigid Frame System Bridge

At present, cooperative system bridges of cable-stayed bridges are greatly appreciated for excellent mechanical characteristics and performances, high adaptabilities, low costs and aesthetic appearances, many bridges of this type have been constructed or are being in construction now. Cooperative system bridges have two basic types, different-load cooperation and same-load cooperation. Cooperative cable-stayed and rigid frame system is a high efficient bridge system. The different-load cooperation type of this unique system was adopted in the application of Jimma Bridge in Guangdong, China, which ranked it the longest concrete bridge structure of sigle tower for having two spans of each 283m long. The successful construction of Jimma Bridge with extreme low costs compared to other variations, along with the high efficient inner structural characteristics and satifying performance in service, has greatly prompted the professional study of this system. The doctoral paper is focused on the examination on how the system perfomence so excellently with the cooperation of two structures, moreover, the static mechanical charatersistics of this system under all kinds of important actions are thoroughly discussed. The main research involves the following:Cosidering the difference in the location of the (dead) loads impacted on the structures, there are two basic types of cooperation system, which may simply identify the inner difference of mechanical performance, and reasearch on two systems has indirectly proved this classification is reasonable.The simplifing of cooperative cable-stayed and rigid frame bridge is proposed by suggesting a simulating structure approxmately has equal stiffeness, and the method of beam on elastic foundation is applied to investigate the mechanical performances.Two models both suggesting cable-stayed beams as beams on elastic foundation are studied with the energy principle approach, the first model takes the rigid frame structure as the restraints of cable-stayed structure while the second model calculate the main beam along with the associated rigid frame.Then the two models are throughly analized by FEM to obtain the mechanical performances. By introducing the index length-a defined length of cable-stayed bridge or cooperation system bridges invoving a cable-stayed main structure, then the bridge structure stayed by cables might be simplified as a multi-span continous beam bridge, in which the no cable-stayed zones (or unsupported beams) are considered as the middle or side spans by considering the connections. From the comparision the reasonable variables of no cable-stayed zones might be suggested.As for single tower symmetrical bridges of cooperation system of Jimma type, the characteristics of displacements and inner forces affected by the variables of cooperative cable-stayed and rigid frame bridge are examined, the results show that the rigid frame could improve the performances of slender cable-stayed structure enormously; the experiment design method is used in mathmatical experiments to select and decrease the models to applicable amount from the whole combination of all factors and all major parameters. The interaction of parameters is studied by the stastistics regression process, as several charateristcs then may be attained as how the effects caused by the interaction of the stiffness of beam, tower and cables. Relative high efficient structures may then be determinated by introducing the uniform design method and statistics process.The parametric analysis of the asymmetrical cooperation cable-stayed and rigid frame system is thoroughly carried out along with the comparision between the asymmetrical and symmetrical structure. The above structures of two types are considerably different and the asymmetrical arrangement introduces many advantages as well as certain shortcomings.Study proved that the span ratio is the critical factor in different-load cooperation systems as well as the relative stiffness in same-load cooperation systems. The connection parts are of global great importance in the combination of structures in different-load cooperation system and the reasearch has laid emphasis on the design and calculation of them. Several applications are given and discussed at the end of the paper to expand the range and to demonstrate the efficient of adpotion of cooperation system bridges.