Steel box girder push
Introduction to construction technology of steel box girder jacking
1. Construction process

The construction process of steel box girder top push is as follows: construction preparation (materials and equipment enter the site), laying of transverse track and longitudinal track, laying of wheel box longitudinal steel box girder, landing on self-locking crawling top push trolley, placing transverse steel box girder in place, connecting steel box girder and adjusting arch of steel box girder

2. Construction technology

2.1 construction technology of longitudinal movement of wheel box

Main equipment: wheel box longitudinal track is laid on the roadbed of the old bridge to lay tracks with a track gauge of 3.2m, P50 steel rail is used, 1.25m short sleepers are used under the track, the spacing is 80cm, and one track gauge tie rod is set for every 10m.
Gauge tie rod can be completed by 4m square wood.
After the wheel box is arranged according to the track gauge, the steel box girder is placed on the wheel box by a 50-ton truck crane, ready for longitudinal movement.
The steel box girder is longitudinally moved to start the wheel box and operate at a low speed. The steel box girder is longitudinally moved to the corresponding span.
In order to ensure the exact position of the steel box girder in transverse movement, the track of the transport girder shall be strictly straight and parallel to the axis of the new bridge, and the steel girder shall be directly opposite the bridge span position when it is transported to the old bridge.
Accurate measurement and positioning are required.
At the same time, in order to ensure the carrying capacity of the old bridge, the track must be set above the main arch of the old bridge.
After the beam is lowered to the transverse track and the longitudinal movement is in place, jacks shall be placed on the wheel box under the beam at both ends, the steel box girder shall be jacked up, the extended transverse track shall be placed on the longitudinal track, and the self-locking crawling trolley on the top of the steel box girder shall be placed on the transverse track below the two ends of the steel box girder.
In order to prevent the sliding of the steel box girder, a layer to two layers of sleepers are installed on the self-locking crawling jacking device. The jack drops the steel box girder onto the self-locking crawling jacking trolley and moves the steel box girder horizontally.
Remove the transverse track on the longitudinal track, exit the wheel box, and conduct the longitudinal movement of the lower steel box girder.
In order to ensure the accurate positioning of the steel beam, the transverse track at both ends should be strictly straight and the axis of the vertical bridge, and the two tracks should be strictly parallel.

2.2 construction technology of pushing the top horizontally

Main equipment: self-locking crawling steel box girder jacking trolley.
The transverse track is laid on the track beam of the temporary abutment with a spacing of 80cm, and a type 50 steel rail with a gauge of 55cm is laid on the sleeper.
The steel box girder is placed on the self-locking crawling top push trolley. The two devices synchronously and slowly push the whole steel beam horizontally to the beam position.
When pushing, the top of both ends of the steel beam is pushed slowly and synchronously to prevent longitudinal displacement of the steel beam.
After the steel box girder is in place, lift up a little steel box girder through the jack on the abutment pier and the built steel pillow (processed from I15 into 70cm and 110cm long steel pillow), draw out the next section of the beam transverse track and track beam, and then drop down to the design elevation alternately through the jack on the abutment pier and the steel pillow, and put the cushion in place.
The positioning order of the 3 sections of the steel box girder is to be erected from west to east successively. After the 3 sections of the 2# steel box girder in the south are placed, the 3# steel box girder in the middle are placed successively.
Fine tuning and connecting the south no. 2 steel box girder and the middle no. 3 steel box girder, and then placing the north three no. 2 steel box girder connection.
After the steel box girder is connected, the arch of the steel box girder is adjusted by the buttress.


3. Problems encountered in the construction process and solutions

For self-locking crawling jacking equipment, the link between active and passive should be added to limit the capsize of steel box girder on jacking equipment caused by insufficient friction.
In the process of pushing the top of the transverse steel box girder, due to the inconsistency between the active and the driven running speed, the driven bearing capsized, but fortunately there was no steel box girder capsized accident, resulting in losses.
According to the field situation, the technology was adopted
Measures proposed by the department: two I15 i-beams (field materials) are placed on the active and driven support to be connected as a whole to limit the relative displacement between the main and the slave, resulting in the capsize event.
After the beam is moved horizontally, it is necessary to correct the elevation and support position of the box girder to ensure accurate positioning.
After the steel box girder falls into the design position through four steel pillow supports, due to the deviation between the height of the box girder and the support position, the steel box girder needs to be corrected and placed in an accurate position.
During the construction, the longitudinal and transverse correction skateboards are processed. The screw jack is used to lie on the transverse and vertical correction skateboards. The contact surface between the skateboard and the box girder is coated with butter.
Influence of transport deformation of steel box girder and machining accuracy of steel box girder on construction connection.
After the steel box girder is processed in liaocheng processing plant and transported to the jinan construction site, the steel box girder will be deformed in the process of transportation, and there are errors in the processing of steel box girder, which will have an impact on the construction and joint of beam adjustment: beam adjustment is difficult to be accurate in place, and it is impossible to be connected under the condition of accurate in place.
During the construction, with the consent of the technical personnel of party a, the connection of the steel box girder shall be guaranteed before adjusting the position of the steel box girder when the steel box girder deforms.
For the steel box girder that cannot be adjusted in place according to the design, the deformation of the steel box girder is evenly distributed from the four corners to reduce the impact of the deformation of the box girder on the bridge.


Precautions for steel box girder top push:

The position of stroke switch should be adjusted carefully before the jacking system is used, and the quality of system power supply should be guaranteed.
Oil must be kept clean.
The oil must be filtered regularly to ensure that the filtration accuracy is not less than 20um, and the oil must be replaced regularly.
For each jacking, the elevation of the middle line of the jacking beam segment and the top of each slide must be measured and controlled within the allowed range:

The deviation of the middle line of the guide beam shall not be greater than 2.0mm;
The midline deviation of the beam body shall not be greater than 2.0mm;
The glide path surface should be smooth and smooth

Both sides of the teflon board should be kept clean, the top of the teflon board must face down, the top of the slide coated with lubrication with silicone grease to reduce friction, cleaning the teflon board can not use gasoline or diesel.
In the process of jacking, if sudden jacking thrust is found, it should be stopped in time and the reason should be checked, especially the teflon plate.
At the beginning of jacking in each section, push 5cm first, stop immediately, return oil, push 5cm again, stop again, return oil, for this purpose, repeat two or three times, to loosen each sliding surface and check each part of the facilities, and then formally push.
When jacking, a special person shall be sent to inspect the guide beam and box beam. If the guide beam member is deformed, the screw is loose, the guide beam is deformed at the junction with the steel box girder or the box girder is partially deformed, the jacking shall be stopped immediately for analysis and treatment.

Key words: steel box girder top push steel box girder top push construction