Bridges, Tunnels and other Transportation Structures
Full Session with Abstracts
High cycle fatigue is a major cause of cracking in steel structures that can result in substantial financial losses and structural failures compromising the safety of users. Textbook uniaxial methods are in many cases not sufficient for large in-service structures with complex geometry and connections subjected to multiaxial non-proportional loadings.
A new method for fatigue life prognosis and fatigue life prediction for roller coasters is presented using the critical plane method. Strain rosettes were installed on a support bracket near weld lines to measure responses for four different loading conditions representing typical loadings of roller coaster riders. This data was used for estimation of the number of stress reversals in high-cycle fatigue induced by live loads and the number of associated cycles using the rain-flow method.
A sub-structure model is defined and used to estimate response prediction in the weld of a target support bracket of a large and complex finite element model. Dynamic sub-structuring allows for fast analysis of stresses of a substructure without the need of re-analyzing the entire structure. The estimation of the input and the state estimation is performed using a Bayesian filtering method, based on a limited number of response measurements and the sub-structured model. This new methodology is anticipated to be used for real-time fatigue prognosis aiming to address critical needs in maintenance and evaluation of infrastructure networks. Results of remaining fatigue life using time-domain and frequency-domain data are compared.
This approach offers great promise at a time of aging infrastructure and limited funds for objective and fast decision making for structural maintenance and repair. In addition, the proposed method is applicable to any steel structure subjected to cyclic multiaxial non-proportional loading in structures such as bridges, trains, aircraft, offshore oil platforms, wind turbines, and rotating machinery.
The applicability of the methodology proposed is demonstrated and evaluated in a roller coaster support structure with the goal of applying it to a three-span continuous steel girder bridge and a long-span steel lift truss bridge.