Long - Span Rigid Frame Bridge Design And Construction Monitoring Study

The background of this paper is a prestressed concrete continuous rigid-frame bridge ,which maximum span of is 160m and maximum pier height of is 100m. In the process of design checking and the construction control 1 ing, the author makes a research of bridge global design, internal force calculation, bearing capacity checking computation, stability checking computation and construction controlling methods etc. . The author focus on main factors that should be taken into account in design, basic theories of structural analysis,calculation content, calculation procgram, calculation methods ,etc.. The relevant program has been worked out and put into practice in the background project. The main results of this Paper are included below:Pier structural configuration in high-pier and long-span rigid-frame bridge could be choiced with double-limb thin-wall pier or hollow single pier; It is more suitable that hollow single pier is adopted when the pier height is beyond 80m, because the stability factor of hollow single pier will be over 3~4 times more safety than the one of double-limb thin-wall pier; If double-limb thin-wall pier is adopted when the pier height is beyond 80m, lateral brace must to be added to decrease the unsupported height of piers; The appropriate stiffness ratio of pier beams is the value that the bridge piers have higher flexural rigidity and the lower compressive stiffness under the premise of satisfying stability and safety; When the box girder is transversely calculated, the effective distributed width of the loading along longitudinal bridge should be modified. The modified stress value is 20-60 percent higher than the one by normative calculation.As far as innovation is concerned, experimental parameters of prestressed vacuum grouting technique and design methods of compound foundation of bridge piers are presented. The results, which have beenverified in field experiment and have achieved admission of experts, areutilized in Xiaoguan Bridge. By eliminating air bubbles in the prestressed passage and paste at certain degree of vacuum (>80%), the vacuum grouting technique can make grouting satiable and compact.So it can make equipped corrugated-plastic-tubes airtight, corrosion-resistant , high strength and small frictional coefficient, reducing the frictional loss of prestress and increasing prestress effect about 10 percent. Bearing capacity of pile foundation is calculated by compound foundation design method, given that foundation pile and base slab bear force collectively and that compatibility of deformation condition is satisfied. Compound foundation is devised by means of strengthening groundsill at the bottom of base slab , tectonic treatment of reinforcing pile butt in the base slab, and accounting for non-uniform settlement of the upper configuration. The rock under the No. 4 pier in Xiaoguan Bridge is a little soft and is dissatisfied with bearing capacity of bracing pile. Good results have been obtained by adopting the method of compound foundation design.Structural analysis of this paper is based on the finite element method (FEM) and calculation theory of long span bridge. At first, structure units and construction phases are divided into. Mechanical model, stiffness matrix, load matrix and displacement matrix of the structure are built stage by stage. Then, unit stiffness equations and integrated stiffness equations are established respectively according to geometric conditions and equilibrium conditions among the units. Internal force and displacement in any construction (service) phase are resolved. By means of influence line loading of dynamic planning, the internal force of the service phase produced by automobile load are computed, maximum load effect and final stress state of the service phase are calculated under the worst loading combination. In the end, reinforcement design, bearing capacity checking computation and stability checking computation are carried out according to the normative formulas.