Parametric study of orthotropic steel decks with open ribs using FEA

<p>For orthotropic steel deck (OSD) bridges, the open ribs are less used because of their relatively lower torsional stiffness. However, with the design focus of OSD shifts from strength design to fatigue design, the system of open ribs shows the potential to be more considered for future projects. In this paper, a newly built OSD bridge is investigated focusing on the rib-to-crossbeam joint. Based on the in-situ measurements of the existing bridge, the numerical modeling of the whole bridge is finished. Furthermore, a simplified local model is developed focusing on the rib-to-crossbeam joint. Then, the influences of design parameters i.e. the crossbeam span and the spacing between ribs are investigated. Research results reveal that the global behavior of the bridge can be modeled. However, calculation results of points close to the connecting weld and the cope hole do not fit well with the measurements. In this case, increasing the crossbeam span will decrease the stresses of points close to the weld toe of the connecting weld. Increasing the spacing between ribs is more effective to reduce the tangent stress around the cope hole. The most unfavorable load position does not change with these two parameters.</p>

Fatigue Life Assessment of Revised Cope-Hole Details in Steel Truss Bridges

In recent years, various welded details with complex local structure, ambiguous fatigue performance have appeared in fully welded steel truss bridges, however, they are not covered in the current design specifications. In order to study the fatigue performance of revised cope-hole details, fatigue performance experiments were designed and carried out on three specimens of revised detail with the same dimensions but subjected to different stress amplitude. Local finite element model of the revised cope-hole detail was established for further stress analysis. The results of finite element analysis were basically consistent with the static test results at majority of measurement points. Based on the existing fatigue test data and fatigue strength of cope-hole details defined in Eurocode and JSSC design code, the fatigue performance of revised cope-hole details was evaluated. The S-N fitting curve with the failure probability of 2.3% was obtained from the fatigue experiment results. The fatigue stress amplitude was 59.5 MPa when fatigue loading cycle was 2 × 106. It can be concluded that the fatigue performance of revised cope-hole detail was better than that of previous welded detail, which indicated that the revised detail had a significant improvement.

Fatigue Life Assessment and Reliability Analysis of Cope-Hole Details in Steel Bridges

Cope-hole details are widely applied to steel bridges. However, the safety of steel bridges is influenced by the fatigue performance of welded details. So, cope-hole details with flange and web subjected to axial loads were selected as the research object. Based on the basic theory of linear elastic fracture mechanics and the Finite Element Method, the stress intensity factors of cope-holes details were calculated. The influences of geometry size and crack size of the detail on the stress intensity factors were then investigated. The Paris model of fatigue crack propagation predicted the crack propagation life of cope-hole details. Besides, the fatigue limit-state equation was also established to analyse the effect of random variables (such as initial crack size, critical crack size, crack propagation parameter) on the fatigue reliability index. Finally, the recommended value of the detection period was present. The results show that the stress intensity factor gradually increases with the increase of the cope-hole radius, the weld size, the flange plate thickness, the crack length and the web thickness. However, it gradually decreases with the increase of the ratio of the long and short axle to the crack. The predicted number of fatigue cyclic loading required by the fatigue crack depth propagating from 0.5 mm to 16 mm under nominal stress amplitude of 63 MPa is 122.22 million times. The fatigue reliability index decreases with the fatigue growth parameter, the crack shape ratio and the mean of initial crack size increasing, which is relatively sensitive. However, the variation coefficient of the initial crack size has little effect on it. The detection period of cope-hole details is the service time corresponding to the fatigue accumulated cyclic loading of 198.3 million times.

Stress Characteristics Analysis of a Corrugated Web Composite Girder under Out-Plane Bending

The focus of this study is to analyse the stress distribution of corrugated web girder subjected to out-plane bending. Welded joining is considered in this study to connect the corrugated web and beam flange. As stress concentration is very critical for the prediction of fatigue life of the structure, this study provides preliminary results for further fatigue assessment of box-section girder bridge with such structural details. A finite element analysis based study has been conducted to trace the stress distribution along the corrugated web with varying thickness and cope hole details. The comparison with related simplified expression and typical stress concentration behaviours are outlined in this paper. Comments are given for the further consideration of presented stress characteristics in the fatigue design.

Numerical Analysis of the Effect of Cope Hole on the Fatigue Strength of Corrugated Web Girders

A common means of facilitating cross welding on the girder flange is to use cope hole on the girder web. This paper presents a study on the fatigue strength of the corrugated web girders with the cope hole using numerical analysis. Typical stress concentration behaviours are discussed relative to reported experimental results, and parameter variations are then used to study the stress gradient on the corrugated web as the influence of the cope hole. Based on the simplified cumulative fatigue summation implemented in fatigue post-processor, fatigue life predictions are presented with codified curves of AASHTO LRFD.