The Research On Calculation Method And Damage Evalution Of Bridges Based On The Charateristic Of Cracks Distribution

Reinforced concrete bridge is currently the most widely used material. But with the passage of operating time, under the influence of various factors, existing reinforced concrete bridges often occur a variety of injuries, among which fracture is one of the main manifestation. To ensure the safety of the structure, to research the features of crack major disease. Then to evaluate the damage situation and the carrying capacity of the structure has extremely important theoretical and practical significance.This paper summarizes the classification and causes of concrete cracks and introduces X-FEM crack damage extended finite element theory and its application in ABAQUS software, then regards simply supported beam and continuous beam as object of study, based on the previous two-dimensional model, establish a more realistic three-dimensional model of physical damage. According to this to study a variety of damage condition and carrying capacity conditions of structure in vertical crack flexural, shear inclined cracks, as well as the number of cracks in the concrete reinforcement amount, steel shapes, whether with initial microcracks. The main conclusions obtained as follows:(1) Reinforced stress have no big difference, crack produced under the same load late more similar in height and width whether initial microcracks exist on simply supported beam, indicates that it has little effect on structural damage whether the initial microcracks exist. Also found that, in the three-dimensional model of local bars on both sides of the crack crack than a position reinforced damage to a large, two-dimensional model that can not be reflected.(2) The same as in the case of simply supported beam single initial crack, as fracture height as an indicator, the damage of unreinforced beam, less reinforcement beam, suitable reinforcement beam and superfluous reinforcement beam show a decreasing trend, and concrete damage is more serious when configures no steel or less reinforced, superfluous reinforcement beam has potential risk of sudden destruction. The calculation results of multiple fractures is consistent with a single crack.(3) In oblique cracks, compared with the previous bent steel bars bent, its stress reduction nearly doubled, while also significantly reduced the fracture length, indicating the holder near the rebar bent a lower structural damage, inhibition oblique effective way to extend the cracks.(4) For continuous beam under the same load, compared with the case only positive cracks exist, oblique crack and at the same time being cracks appear, due to redistribute beam internal stress, and conducted cracks but relatively slow, fracture height lowered by bending area the damage is also reduced.