| Bridge structure should be satisfying the safety and durability requirements. Structure safety depends on ultimate bearing capacity. In bridge structural design lifetime, the durability is declining gradually. Since the durability have close relationship with bearing capacity, therefore the bridge structural bearing capacity is declining with the time.When the bearing capacity is declining with the time under the design level, the bearing capacity is inadequate relatively. In order to make full use of the bridge with inadequate bearing capacity, the technical transformation should be carrying out. The technical transformation involves two major aspects: one is old bridge assessment; the other is bridge disease treatment.Old highway bridge assessment is to evaluate synthetically the usage condition and the bearing capacity of the existing bridge. Through the assessment, we can find whether the bridge tested maintains the working performance and the bearing capacity that has been designed, whether the bridge tested satisfies the requirement for present and future traffic, whether the bearing capacity of the bridge tested can be improved. This assessment can contribute effectively the support for the maintenance and strengthening decision of the old bridge.The treatment countermeasures of the bridge are the methods that can strengthen the existing bridge structure with effective and feasible technology measures. It includes the strengthen method for superstructure and the strengthen method for substructure. The radical purpose of bridge structure strengthen is to recovery and improve the bearing capacity of the existing bridge structure.This thesis systematically expounds theoretic foundation for bearing capacity of concrete bridges based on loading test,The thesis makes analysis and evaluation on advantages and disadvantages of systematic methods normally used for reinforcing superstructure of bridges. Also,combining practical works,and through joint method of quantitative analysis and qualitative analysis,and uses finite element analysis method , this thesis makes accurate analysis and calculation on bridges tested. It also forwards specific methods on how to treat defects of bridges tested.1.By loading test, we can test directly the designed bearing capacity of the bridge structure. We can also calculate the real bearing capacity of the structure with analysis the bridge mechanical behavior and property in loading test.2.Theoretic basis of bearing capacity assessment for bridge: The bearing capacity of structure includes two aspects, one is the bearing capacity for ultimate strength state of the bridge, and the other is the bearing capacity for ultimate state of the bridge's normal use. The ultimate state of the bridge normal use can be practiced or tested by loading test. Because the one ultimate state makes contact with the other, these two ultimate states have the same safety level in ordinary conditions. So, with loading test, we can test the stress and defluxion of ultimate state for bridge normal use, we can also assess the ultimate strength and stability of the bridge structure in ultimate strength state.3.The bearing capacity assessment requirements of the bridges tested are following.(1) Requirement for strength and stability assessment isSd ≤ Rd·Z2(2) Requirement for stress assessment isσ ≤ [σ]·Z24.In static loading test, the primary factors affected the bridge loading capacity analysis are loading test efficiency, testing coefficient, relative residual deformation, check coefficient, load transversal distribution coefficient and some parameter relative curves.5.Dynamical parameters reflect bridge structure dynamic properties and affect the evaluation of bridge structure bearing capacity are structure dynamical impact factor, frequency of freedom vibration, damping ratio, amplitude and dynamical stiffness, etc. 6.The usual methods for superstructure strengthens are changed mechanical system method and unchanged mechanical system method. Methods for subs...
|
PDF Full Text Request