Based on a box girder bridge in an actual highway project, in-situ tests are carried out to understand the real stress state of vertical prestressed tendon. Researches of vertical prestressed losses during construction have been made in this paper. What is more, the regular pattern between the effective stress and time is proposed. Meanwhile, an efficient method which could control the prestressed losses is introduced. Eventually, it is aimed to conduct the construction of vertical prestressed tendons and improve the quality of tensioning. It also could provide a reference for design and quality control of vertical prestressed tendons in the similar type of bridges.
Structural concrete strength rapid detection methods were analyzed, which mainly include Rebound Method, Ultrasonic-rebound Combined Method, Dirlled Core Method, Pull-Out Method. Technical characteristics, advantages and disadvantages of each method were compared and analyzed. Application of each method was analyzed. Based on current detection technical specification, ultrasonic-rebound combined method for testing concrete strength was analyzed. Actual concrete bridge as a platform for a comparative test, ultrasonic-rebound combined method test was carried out. Problems were put forward and recommendation was made through discussion.
Since lamination parameters were found to represent the stiffness properties and the orientation of each ply, two major stages are defined to do the optimization. In the first stage which is called continuous optimization, the required lamination parameters will be obtained by VICONOPT but this has not been completed. This paper focuses on the second stage which is called discrete optimization. It consists of three programs and the major program is called OPBDP. Random values of required lamination parameters for 4, 8 and 16 plies lay-ups are chosen and assumed, then the results are computed and compared. What is more, a method called double up the plies is introduced and the results show that it could save a lot of solution time but is still only suitable for a small number of plies.
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