Influence Analysis on Prestressed Reinforcement Tensioning Modes of Cast-in-place Box Beam

Transcription

1 0 1 Journal of Highway and Transportation Research and Development Vol. 0 No. Mar. 1 doi /j. issn m MIDAS /CIVIL m m MPa 1 2 U A Influence Analysis on Prestressed Reinforcement Tensioning Modes of Cast-in-place Box Beam LIU Shiming 1 2 LIU Yongjian 1 GENG Dongsheng 1 SONG Yao 1 1. Key Laboratory for Bridge and Tunnel of Shaanxi Province Chang'an University Xi'an Shaanxi China 2. North China Institute of Water Conservancy and Hydroelectric Power Zhengzhou Henan China Abstract In order to study the influence of prestressed reinforcement tensioning modes on deformation stress and effective prestress of bridge beam and to ensure the safety during construction process and the reasonable structure stress at completion status according to the construction of the first span m of the ramp bridge located in Dongguan section of Conghua-Dongguan expressway project which is a cast-in-place concrete continuous box beam using the finite element analysis software MIDAS /CIVIL considering plane curve longitudinal slope of the bridge shrinkage creep and strength development of concrete and the 5 kinds of prestress loss of prestressed reinforcement keeping the prestressed curve and the controlling stress tensioning modes including single end tensioning span by span scheme 1 single end tensioning on single span at first and then 2 spans simultaneously scheme 2 and 2-end tensioning on spans scheme are simulated. The stresses of the beam during construction the stresses and deformations of the beam and the effective prestresses of the prestressed reinforcement in completion stage are analysed and compared. The results show that 1 the concrete tensile stresses at top surface of box beam at a distance of m from the beam end nearby abutment are both greater than the design value in the construction stage of scheme sokd_ 0@ 16. com

2 84 0 and scheme 2 2 in completion stage the beam deformation of scheme 1 is the maximum the beam deformation of scheme is the least while there is the maximum tensile stress whose value is MPa at top surface of box beam at a distance of m from the beam end nearby abutment tensioning mode has the direct influence on the value and layout of the effective prestress compared with scheme 1 the effective prestresses near the middle section of the second span are smaller which should be paid attention to in design checking calculation. Key words bridge engineering cast-in-place box beam finite element analysis prestressed reinforcement tensioning mode loss of prestress effective prestress m m m 1. 4 m C f pk = MPa 0. 72f pk = MPa m. 594% % ~ N1-1 ~ N2-1 ~ N - 0% 40% ~ 50% 1 ~ N2 N1 N Barr # 0 # # 5 m m m 2 1 m

3 85 Fig. Computation model of bridge mm ~ 1 1 Tab. 1 Simulation of construction stage of scheme 1 /d N2 N1 N N2 N1 N 1. 2 Midas Civil CEB - 2 FIP 1 N2 N1 N 0 2 Tab. 2 Simulation of construction stage of scheme 2 /d 1 1 N2 N1 N N2 N1 N 6 0

4 86 0 Tab. Simulation of construction stage of scheme /d 1 N2 76% 6. 6 mm Tab. 5 MPa Extreme beam stress values under different construction schemes unit MPa 2 N1 40 N / / / / / / / / / / / / / mm 1 2 Tab. 4 Extreme beam deformation values in completion stage under different construction schemes unit mm MPa C MPa /% / / m % 0. 6 mm N1-2 N2-2 N / m MPa MPa C MPa Fig. 4 4 Effective prestresses of prestressed reinforcement

5 87 4 N1 N2 N % ~ 9. 61% % ~ 8. 56% m 2. 5% ~ 7. 88% m 1 2 N1 N2 N N1 N2 N N1 2 N2 N m 15 m % 6. 6 mm m MPa m Tab. 6 1 Percentage extreme change of sectional effective 1 2 prestress compared with scheme 1 2 /% /% N / / /9. 59 /2 N / / / /2 N / / / /2 N / / / /2 N / / / /2 N / / / /2 N / / / /2 N / /2 -. / / N / / / / % ~ 9. 4% % ~ 5. 99% 10% 0. 6 mm 2 4 References 1 JTGD S. JTGD Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts S J m / LI Shuangyi WANG Yanqin ZHANG Yiyu. Analysis and 6 1 Control of Stress Loss in the Process of Presstressed Contruction by Post-tensioning Method J. Liaoning 2 N1 N2 N Communication Science and Technology % ~ 9. 26% 56..

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