Research About Calculation Length Coefficient,Rational Dimensions And Reinforcement Ratio For Column Pier Of Mountain Bridges

With the development of our country highway construction pattern, there comes more and more BT and PPP project, the cost control becomes key question of the highway project. For the mountainous highway, prefabricated bridge becomes the popular preference because of short construction period and less investment. Accordingly, the application of column pier becomes popular. Therefore, the calculated length coefficient of column pier under conventional span, the reasonable size and reinforcement become the key issues for the mountainous area highway design.The thesis is conducted based on a mountain area highway prefabricated bridge construction, using the energy method and finite element method to carry out the research of calculated length coefficient and the cross section reasonable size and reinforcement of 25 m~40 m high piers, the main research results are listed as follows.Energy method was applied to deduce the calculation formula of first-order buckling critical load of column pier, the calculation length coefficient is obtained by Euler's formula. Its boundary conditions refer to one-side elastic restraint and elastic restraint on both ends. The formula results can satisfy the engineering requirement as comparing with the calculated length of ideal boundary constraints in 04 codes.Finite element method was applied to analysis the calculated length coefficient of 25 m~40 m high piers under the given geological conditions. The calculation results of naked pier stage, capping beam connection phase stage, construction stage of frame beam and finished stage of four kinds of working conditions are respectively put forward through massive calculation. From the distribution regularities we can draw the conclusion as below. Section stiffness modify is not necessary when analysis calculated length of bridge pier; The calculated length of each bridge pier is largest in construction state, smaller in finished stage when pier and girder are not consolidated, and minimum in finished stage when pier and girder are connected. It shows that the influence of boundary conditions on the high piers is significant. Considering the effects of calculated length coefficient, larger values were recommended in table 4-4-7 in practical application.Finite element method was applied to analyze reinforcement stress, crack width and safety for 25m~40m pier in construction stage and finished stage on a mountain area highway under the specific geological conditions. Under the given geological conditions, strength and crack calculation of each bridge pier in finished stage can meet the code requirements, and has safety stock. Construction stage is control stage, two kinds of construction condition were analysis. Recommended values are obtained and listed as below. For the 25 m pier, the pier diameter is 1.8m, reinforcement for 42?28; 35 m pier, the pier diameter is 2.0m, reinforcement for 42?32; 40 m pier, the pier diameter is 2.2m, reinforcement for 52?32.The research results in this thesis can provide reference for the pier design of the mountain area bridge.