Study On Fatigue Performance Of Light-weighted Composite Bridge Deck With Closed Ribs

Attributed to its light self weight, high bearing capacity, rapid erecting speed, and superior integrity, orthotropic steel deck has been widely applied to long-span bridges all around the world. However, two major technical challenges exists in orthotropic steel bridge deck:fatigue cracking and conventional asphalt pavement failure.Taking Second Dongting Lake Bridge (a suspension bridge with a light-weighted composite bridge deck) as an example,hot spot stress approach is used to calculate the stress ranges of weld fatigue-cracking details. In order to optimize the mechanical behavior of fatigue details, parameter analyses are performed to investigate the typical shapes of cutouts of closed ribs on diaphragms which are adopted in domestic and foreign codes and thickness of diaphragms based on finite element analysis.Based on Second Dongting Lake Bridge, this paper has conducted a pilot investigation on the fatigue performance of this innovative composite deck system. In this study,the author finished the following work:Firstly, this paper summarizes the process of the development and the current use-situation of traditional steel bridge deck. Then, after giving the material properties of UHPC, it introduces the concept of light-weighted composite bridge deck.Secondly, based on the hot spot stress approach, this paper carries out finite element analysis. The results reveal that, the traditional steel bridge deck is difficult to meet the engineering requirement of Second Dongting Lake Bridge. Compared with traditional steel bridge deck, the stress ranges trough rib and transverse ribs of light-weighted composite bridge deck with closed ribs are reduced by 51.8% to 86.1% what is no risk of cracking. It is necessary to pay special attention to the fatigue details around diaphragms because their stress ranges are still high. Changing the thickness and cutout shapes of diaphragms can significantly decrease the stress level of fatigue details around diaphragms.Thirdly, assessing the fatigue life of this innovative composite deck system based on the fatigue design specifications of steel bridge of China. According the analysis results, after passing 1862961 standard fatigue vehicles in total, fatigue cracks will appear at the rib of rib-to-diaphragm connections in middle lane.At last, the full-scale model fatigue test indicates that, the fatigue performance of circular arc transition on diaphragms of Second Dongting Lake Bridge can meet the design requirements; the research of 3 different bonding modes between the layer of STC and steel top plate implies that, strengthening the interface bond can improve the mechanical behavior of light-weighted composite structure.