Research On The Deck Fatigue Performance Of The Half-throughcfst Arch Bridge

Most of half-through CFST arch bridges constructed earlier are made up of cabel-hung cross beams which are connected by bridge decks, without corresponding longitudinal beams. This results in the bad entirety, low rigidity, bad dynamic performance, large vibration range, long length of time and slow energy dissipation,which are harmful for the performance of use, durability and safety of the bridge. In this case, bridges of this style appear many kinds of damage such as the loose, crack, worn or even holes on the surface. And as the bridges are already constructed, it is very difficult either of design or of construction to add corresponding longitudinal beams to these bridges. Therefore, it is necessary to analyze the performances of the bridges comprehensively in order to find out the measures to improve the performance of the bridge decks from other aspects. This paper analyze the dynamic response of the bridge decks from the aspect of the bridge fatigue performance, use the separation-type-measure to compute the dynamic response of the bridge and analyze the impacts of many factors on the fatigue performance of bridge decks.First, the finite element model based on the real Changqing Bridge in Shenyang is built, and corresponding vehicle model and bridge roughness model are sellected to analyze the vehicle-bridge coupled vibration carefully. The dynamic response of the bridge under vehicle force is analyzed such as dynamic displacements, impact factors and dynamic moments. It is found that the decks on cross beams are under the situation of positive-negative alternate stress, which could result in larger damage to the deck than the single positive stress in the deck in the middle of two cross beams. And then the impacts of the roughness and vehicle speed on the bridge dynamic performance are analyzed, from which it is found that the worse the roughness is, the worse of the bridge dynamic performance is; and the vehicle speed has no apparent impact law on the bridge dynamic performance.And then, the bridge deck is studied especially from the aspect of the fatigue performance. The impact of the cross beam width, the deck thickness, the roughness and the speed of the vehicle is calculated and analyzed. It is found that the wider the cross beam is, the longer of the fatigue life is; the thicker the deck is, the longer of the fatigue life is, and which has a lower growth rate after 30 cm of the deck thickness; the rougher the surface of the bridge is,the lower of the deck dynamic performance, and it is suggested that it should be grade B at least for the roughness; and the vehicle speed has no apparent impact law on the fatigue life of the deck.At last, the static and dynamic test results of Changqing Bridge are listed, and some reinforcement measures such as the addition of steel longitudinal beams are provided, which are evaluated at the same time. Then the new type of damping device and its improvement plan are introducted in detail, and the reinforcement effects are analyzed. It is found that the improvement plan has more reinforcement effect then the earlier one.