How to install bottom formwork before producing concrete girder?

Here we referes pre-stressed reinforced concrete box girder production technology with post-tensioning method.

concrete girder production with post-tensioning method

(1) Assembly requirements on bottom formwork

1. Preset reversed deflection with a value 20mm as assembling bottom formwork; reversed deflection conditions are as below to meet different segments characteristics of formwork:

Set reversed deflection of bottom formwork according to the form of quadratic parabola y=ax2(y means vertical distance, x is horizontal distance), total length of bottom formwork 33430mm, centre of upper surface of bottom formwork is regarded as zero point of the coordinate.

   x=3985mm      y=1.53mm      x=-15mm        y=0mm­

x=7985mm      y=6.13mm      x=-4015mm      y=1.55mm­

x=12015mm    y=13.89mm      x=-8015mm      y=6.18mm­

x=14418mm    y=20mm        x=-12015mm    y=13.89mm­

                            x=-14418mm    y=20mm­

  2. Setting of above reversed deflection shall be in accordance with height at formwork segments, and assembly shall strictly follow above dimensions

  3. Because segments of bottom formwork have a larger length and straight-line segment is longer, height at two ends of bottom formwork shall be set firstly in the assembly of bottom formwork to produce a down deflection which makes bottom formwork changes be closer to the form of parabola;

  4. Welding for bottom formwork shall be firm, joint connecting of modular shall be smooth, others must follow the inspection standards of formwork installation;

  5. Reserved amount of compression is 30mm;

  6. After finishing assembling bottom formwork, make preformed holes for all built-in fittings in accordance with drawings.