Papers by Keyword: Stress Range

Abstract: The authors present the experience of applying their methodology for calculating the residual life of metal structures of reloading machines by the criterion of the development of fatigue cracks to a critical size. The methodology is based on the well-known calculated dependencies of fracture mechanics, refined and supplemented with elements that take into account the specifics of the operation of transshipment machines in difficult weather conditions. Particular attention was paid to the accuracy of determining the stresses in the metalwork element when performing working operations because of the ever changing of the load acting on the metalwork, depending on the weight of the lifted load and the position of the machine in space. To confirm the high sensitivity to the accuracy of the determination of stresses, the dependence of the influence of the resource element metal with a crack from the amplitude of stress is graphically presented. The methodology for assessing the residual resource has been successfully tested on a number of complex metal.

Abstract: For estimating the fatigue properties of orthotropic deck bridges, a finite element analysis method was provided. In the method, the models of orthotropic decks steel bridge were established by using Midas and Ansys finite element software respectively, the Midas software has tracked two kinds of live load positions that corresponding to maximum and minimum stress of the fatigue checking points, and the most unfavorable loads were loaded to the Ansys model, then the stress ranges of fatigue checking points were obtained and the fatigue properties of the bridge were estimated. The results show that, it is feasible that using the new finite element method to checking the fatigue performance of orthotropic deck steel bridge.

Abstract: Fatigue behaviors of prestressed concrete beams with different corrosion level are investigated in a series of bonded post-tensioned T-beams. The beams have the same designs and submitted to the same maximum and minimum load during the test. Accelerated corrosion method is used to make various corrosion rates of prestressed steel strands. With the corrosion level as main parameter, such as failure mode, fatigue life, mid-span deflection development, stiffness loss, stress expansion, are studied. The test results show that failure mode is changed fracture of non-prestressed steel bar into prestressed steel strand breaking with the increase of corrosion level. Corrosion reduces fatigue life and stiffness of beams, increase deflection and stress range of non-prestressed steel bar.

Abstract: In order to research the fatigue behaviors of the welded rib-to-deck connections in steel orthotropic bridge deck, 14 rib-to-deck connection specimens are designed considering the weld types, butt gap, welding method, and loading position as parameters. Fatigue test are carried out to obtain the fatigue loading cycle times of each specimen under different stress range. Based on the statistical regression analysis, the S-N curves and fatigue classification of the rib-to-deck connections welded with fillet weld and partial penetration weld are obtained respectively. The test results show that, the initial fatigue crack of the fillet weld is prone to appear at the weld root of the rib, while the initial fatigue crack of the penetration weld is prone to appear at the weld root of the deck.

Abstract: The effective stress range (ESR) and the number of stress cycles (NSC) are two key parameters in fatigue damage evaluation. The inaccuracies in predicting remaining fatigue life can be attributed to either one of these two parameters. A sensitivity analysis is described to address the effects of four cycle-counting methods on ESR and NSC for various fatigue details, which including rain-flow counting (RF), mean-crossing-peak counting (MCP), level-crossing counting (LC) and simple-range counting (SR). Using field monitoring data under normal traffic of Wei River Bridge, the comparative results of four methods showed that RF was more conservative than MCP and SR. The relationships between RF and other three counting methods were determined in the form of a correlation coefficient and a linear regression line. Therefore, values obtained for ESR and NSC by MCP, LC and SR can be converted to values for RF, which is used for comparison and transformation of fatigue life evaluation results using different cycle-counting methods.

Abstract: A typical rib-to-deck joint in orthotropic steel bridge deck in a suspension bridge is analyzed in this paper. A local finite element model of bridge deck is established by ANSYS, the vehicle load defined in current code is selected as live load, the stress distribution of the deck bottom in the rib-to-deck joint is analyzed. Let the wheel load move along the longitudinal direction of the deck, the maximum stress range at rib-to-deck joint is obtained under three loading conditions in transverse direction, which are riding-rib wall loading, over-rib loading, and in-between-ribs loading respectively. Using the principles of linear elastic fracture mechanics, the fatigue life of rib-to-deck joint in orthotropic steel decks is evaluated. The analysis results indicate that, the higher stress range under overweight wheel load is the basic reason which will induce fatigue crack at rib-to-deck joint. The Paris formula which is based on the linear elastic fracture mechanics can be used to estimate the residual life of weld joints in orthotropic steel bridge deck.