Steel Orthotropic Deck Systems – Ideal Solution for 200 Year Bridges

<p>Time dependent deterioration of bridge decks, directly subjected to: repeated abrasive loading from passing vehicles; the elements of weather; and winter maintenance agents, is the key challenge to achieving a 200 Year Bridge Design. In-service performance and laboratory tests over the past several decades have demonstrated that the steel orthotropic deck is the only system likely to accomplish this goal. Nevertheless, implementation of this deck system has been mostly limited to long span signature bridges, movable bridges, and temporary structures. The primary impediments to more wider application of orthotropic decks are lack of robust standards, increased efforts required for advanced analysis and design, relatively high initial cost owing to intensive fabrication, and most importantly due to concerns regarding higher possibility of in-service fatigue cracking from a large number of welded connections. This manuscript presents a standard deck design, developed based on the lessons learnt from a number of orthotropic bridge decks implemented in the greater New York region and the knowledgebase accumulated over the years from research and service performance of this deck around the world, which can be widely implemented as a prefabricated modular system towards durable, sustainable and life-cycle cost-effective design of the 200 Year Bridge.</p>

Full-Scale Fatigue Test of Trough-to-Deck Plate Joints in Steel Orthotropic Deck

Trough-to-deck plate joints in steel orthotropic deck are very sensitive to fatigue. A full-scale fatigue test of steel orthotropic deck was conducted to study the fatigue performance of trough-to-deck plate joints between two diaphragms. The test panel has three spans of 1.0m+3.5m+1.0m in the longitudinal direction and five troughs with the width of 3.0m in the transverse direction. At the end of the fatigue test, the cycles of the fatigue load reached to six million and no fatigue cracks were found by naked eye at the trough-to-deck plate joints. Based on the failure criteria of the measured stresses with a sudden change, it is confirmed that the fatigue strength of trough-to-deck plate welded joints with deck plate failure is similar to design category 71 in the Eurocode using the measured stresses at a distance of ten millimeters from the weld toe.

Research on Static and Dynamic Tests of Steel Orthotropic Decks

The static and crawl tests on the steel orthotropic deck of Xihoumen bridge were performed, which is to study the mechanical behavior and stress history curve of the construction details under traffic loading. The results of the tests reveal that, under the three-axle-weighted 30 t truck, the biggest value of longitudinal stress for the bottom of rib is 51.7MPa，the value of principal stress for the hole upper of diaphragm is 30.8MPa and transversal stress for the deck is 16.7MPa. the length of longitudinal influence line of transversal stress for the deck and vertical stress for the web of rib is about 7.2m. The influences of the principal stress for the opening upper of diaphragm and longitudinal stress for the bottom of rib are 5.4m and10.8m, respectively. Furthermore, the stress range and cycle times were analyzed by sluicing method. Under the condition of the craw tests, cycles of the key details that the stress range is larger than 5MPa for steel orthotropic deck are as follows: the longitudinal stress for the bottom of rib is three times and the biggest value of range is 60.1MPa: the transversal stress for the deck is three times and the biggest value of range is 26.8MPa: the vertical stress for the web of rib is four times and the biggest value of range is 16.1MPa: the principal stress for the hole upper of diaphragm is two times. Finally, Based on the results of dynamic test, and considering the specifications on impact coefficient by various countries, we suggest that impact coefficient shall be adopted in the calculation of fatigue of steel bridge deck; the joints on bridge deck 1+=1.75; for other parts, the calculation of each structure details of longitudinal ribs and deck, 1+=1.0; for calculating lateral girder (diaphragm) details, 1+=1.15.