Research For The Steel Highway Bridge Design Method Of Probability Limited Status Based On Reliability Theory

The current Specification of Steel Highway Bridge and Wooden StructureJTJ025-86 in China employed the allowable stress design methodology. Because ofthe rapid growth of the steel highway bridge construction inChina, it can not adapt theactual state well to some extent. It has been clarified in the Uniform Standard ofReliability Design in the Structure of Highway Projects GB/T50283-1999 (Hereafterrefers to as Highway Uniform Standard) which is the unique specification forhighway engineering projects design that the design method of probability limitedstatus based on the structure reliability theory is the general principle, thus it isimperative to establish a new specification for steel highway bridge. The probabilisticlimit state design method based on the reliability theory is researched by the datecollection and statistical analysis. The probabilistic distribution and statisticalparameters of the loads and resistances are analyzed and the reliability indexes andresistant factors are proposed. In details, the following aspects are investigated:1. The probabilistic distribution and statistical parameters of the steel members'gravity are derived from error estimation and investigation onsite. The steel membersare combined with the cement concrete pavement and asphalt concrete pavement withdifferent ratio respectively. The statistical parameters are calculated for eachcombination and the most unfavorable combination is determined. So the designvalue of the dead load can be calculated by these results.2. The date for materials properties uncertainty analysis is collected by threeaspects. In the first, the mechanical properties data of Q235q and Q345qDmanufactured by steel plants across the whole country is investigated. In the second,the 28652 date is collected from 2563 steel quality certificates which come fromZhouqu Bridge and Dongdai Bridge respectively. In the third, the mechanicalproperties date of welding joints is analyzed with consideration of the effect of thewelding. So the probabilistic distribution and statistical parameters of the materialsproperties uncertainty is obtained by all the data. 3. The statistical analysis of geometric parameters uncertainty of the structure, thesection's geometric characteristic uncertainty of steels and the section's geometriccharacteristic uncertainty of steel members are performed. The statistical parametersof the model's calculation uncertainty are collected from references. So theprobabilistic distribution and statistical parameters of the resistance is derived.4. According to the actual specification, the first-order secondary-moment method(JC method) is used to calibrate the reliability indexes of the components under 5stresses which are axial tensile, axial compressive, eccentric compressive, flexuraland shear stresses. Thus, 8 groups of reliability indexes are derived which are thereliability indexes of primary and adjunctive combination under normal and intensivecar operation status when mobile load effect belongs to extreme value typeâ… distribution and normal distribution respectively. Then the reliability indexes ofstrength limit state are proposed.5. The resistant factors of steel highway bridge's components are proposed byoptimal analyze according to the reliability indexes above.6. The proposed reliability indexes are analyzed by contrast with the values inHighway Uniform Standard and other specifications. It is indicated that the reliabilityindexes recommended by the Highway Uniform Standard are not adapted to the steelmembers because the resistance analyses is based on concrete members.7. In the finality, the problems requiring further studies are discussed.