STUDY ON L-TYPE CRACKS OF HOLLOW SLABS INDUCED BY STRESS CONCENTRATION

Normally small and medium span bridges are designed using standard drawings. In particular, the mid-span parting-line of concrete safety barrier on hollow slabs is a common design in standard drawings. However, large-scale L-type cracks appeared in the mid-span of side girder of Yangsi viaduct on Taijin Expressway because of the mid-span concrete safety barrier parting-line on hollow slabs, suggesting that the mid-span concrete safety barrier parting-line is related to the cracks. Site investigation was carried out and information on the bridge's drawings, construction, materials and cracking was collected. Elastic and plastic damage finite element models were established by using ABAQUS to analyze the cause of L-type cracks. The results demonstrated that:1) When the safety barrier and hollow slabs were consolidated, the safety barrier parting-line caused a sudden change in stiffness, resulting in stress concentration and subsequently L-type cracks through the traditional neutral axis; 2) With the decrease in the parting-line's width and the increase in the parting-line's depth, the stress at the mid-span bottom of the side girder gradually increased; 3) Regardless of the elastic model or the plastic damage model, the trend of stress concentration induced by improper mid-span concrete safety barrier was consistent. The findings of this study are expected to modify the traditional scheme of concrete safety barrier parting-line and improve the performance of hollow slabs.