What are Functions of Main Structure of Movable Scaffolding System?

?Structures and main functions

General dimension in working condition length 70m, width 19m, height 12m, from upper to bottom part, ZZHZ movable scaffolding system is made up of support frame, support gearbox, front and rear guide beam, main girder and lateral connection part, bottom die, side die and rear anchoring beam, anti-typhoon device, hydraulic system and walkway (stairs, platform) and other parts. Realize functions of automatic jacking of hydraulic system, lateral moving and longitudinal moving to cross piers. The complete machine can meet two-way construction demands: moving forward and moving backward construction.

1. Support frame

Support frame can transmit the complete machine load and working load to the pier. Using piles cap supporting structure, support frame is made up of two parts connected by 8.8 grade high tension bolts. Guide sliding rail is set up on the upper surface of bracket, moving gearbox is supported on the sliding rail for the convenience of lateral movement of formwork, longitudinal, lateral and jacking cylinders are supported on moving gearbox, as the bridge making machine crosses piers, formwork jacking cylinder can be suspended at the bottom part of main girder and move forward with main girder. In the construction, jacking cylinder jacks the whole formwork up to make bottom rail surface of main girder 500-550mm far away from moving gearbox. As moving, jacking cylinder draws back to release mold, main girder seats on rail support wheels of moving gearbox so that lateral and longitudinal moving can be realized.

 

2. Moving gearbox

Moving gearbox is the carrier to realize mold release, formwork jacking, lateral and longitudinal moving of formwork. Moving gearbox is made up of gearbox frame, support beam, roller gearbox, lateral moving cylinder, longitudinal moving cylinder, vertical jacking cylinder and other parts. Gearbox frame is box type plank frame, lateral mobbing sliding seat at the bottom is supported on the sliding rail of bracket near to pier to make support gearbox slide laterally along the bridge and realize lateral moving of formwork. Support beam in the gearbox frame is made up of inside support beam and outside support beam used to support jacking jacks and roller gearbox. Inside and outside rolling gearboxes are set up on the outside support beam, and inside support beam is used to decentralize loads of jacking jacks.

 

Longitudinal, lateral and vertical moving of formwork is realized by different cylinders. One end of lateral moving cylinder is installed on support gearbox frame, the other end of piston rod is connected with flexible installation seat which can slide along bracket near to piers, by plugging locating pins, and lateral moving of support gearbox on the pier bracket can be realized by use of cylinder. One end of longitudinal moving cylinder is installed on support seat of support gearbox frame, the other end is connected with longitudinal moving flexible ear seat on the longitudinal moving rail at the bottom of main girder, install pins, and longitudinal moving of formwork can be realized by use of cylinder. Two longitudinal moving cylinders at front and back alternately stretch out and draw back, flexible ear seats at front and back change positions along the moving of cylinder to make formwork move forward alternately. Jacking cylinder is equipped with hydraulic lock and mechanical lock which can realize fine tuning lock by rotary nuts on the telescopic cylinder, matched with Harvard safety hoop, quite convenient, safe and reliable to ensure absolute safety of hydraulic system in the concrete construction.

 

3. Main girder and lateral connection part

Main girder is made up of 2 sets steel box girders, 17 pieces lateral connection truss girder and other main parts. Each set steel box girder has 3 sections steel box and 2 groups of adaptor connector. Steel box girder dimension: height 2.4m, width 1.4m, length 38m. cover plate thickness 18mm, web plate thickness 10mm, lower edge sets up two walkways: rail plate with width 80mm, thickness 30mm. longitudinal, lateral braces are equipped inside of box girder to meet demands of local stability. Box girder connector is connected and splice plate with M24 refined bolts 8.8 grades.

Cross girder and main girder are connected with steel structure high tension bolts 8.8 grades, each lateral connection is divided into two parts connected by high tension bolts, alignment taper pins and alignment pin holes are set up in the middle.

 

4. Front guide beam

Front guide beam is triangle truss girder whose upper chord is connected with steel box girder by high tension bolts for flange structure, and bottom chord is connected with main girder by pins, guide beams are connected by pins

5. Counterweight

To keep side horizontal stability of formwork after two groups of formworks are divided laterally, concrete sidewalk slab as counterweight should be added on outside walkway of steel box girder to add lateral stability of formwork in the starting crossing piers condition, at the mean time it demands an accurate layout position of sidewalk slab and firm connection between reinforced steel bars to meet workers passing needs.

 

6. Bottom die

Bottom die of formwork bears a majority of weight of concrete beams, transmit loads to cross girder by bottom die screw jacks, then to main girder. Bottom die plate is divided into 11 sections along the bridge. Screw jacks are installed between bottom die and lateral connection part, which can not only transmit bottom die loads to its lateral connection parts, but also can be used to adjust height of bottom die to meet arch demand of pouring concrete box girder. Adjustment scope for screw jack is 0-100mm. for the convenience of mold release and adjustment, 5mm intervals should be kept between each two adjacent formworks along the bridge, stuff the intervals with adhesive tapes, use quick-drying putty and atom ash to stuff the formwork surface to ensure a smooth surface and avoid leakage.

Scattered die and end die at pier top can use steel plate, wood formwork or bamboo glue formwork, available support parts of formwork can be supported at pier top, it demands a reliable connection between scattered die and formwork at pier top.

7. Side die and its support

Side die is designed according to concrete girder dimension. Middle side formwork is of standard formwork, 6m for one section. Welding installation quality of side die meets related requirement of road specification, convenient for transportation and removing. Support rod is adjustable rod, adjustment scope 0-300mm to ensure accurate alignment and convenient mold release of side die.

For the convenience of mold release and adjustment, 5mm intervals should be kept between each two adjacent formworks along the bridge, stuff the intervals with adhesive tapes, use quick-drying putty and atom ash to stuff the formwork surface to ensure a smooth surface and avoid leakage.

8. Rear anchoring beam

To have a smooth transition at junction place of new and old concrete, ZZHZ sets up a rear anchoring beam to tighten old concrete and rear part formwork, start to use rear anchoring beam device as constructing normal span and last span bridge, not for the first span

9. Safety device

Safety device includes bracket operating platform; longitudinal walkway between two steel box girders; up and down ladder; pier top guard rail of steel box girder (installation at worksite); front end operating platform for concrete girder (temporary construction); safety net should be prepared at the worksite with all lateral bracing system

10. Anti-typhoon device

The anti-typhoon device is only used for typhoon hit 12 grade under non-working condition. It is demanded to move back formwork onto installed girder before the typhoon is coming, jack compound die to contact with girder tightly, take safety measures for jacking jack, set up rear anchoring beam and tighten it, bind concrete girder with temporary binding steel wire rope group, respectively pull wind cables from front and rear guide beam to front and rear piers and tighten them.

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11. Hydraulic system

Hydraulic system includes: 1) support leg hydraulic system; 2) steel box girder lateral moving hydraulic system; 3) longitudinal moving hydraulic system;

11.1 support leg jacking hydraulic system

One set hydraulic system is respectively installed at front and back of steel box girder at one side, 4 sets in total, each set includes pump station 1 set, jacks 2 pieces, 4 sets pump stations and 8 jacks in total

Pump station is of high pressure plunger pump, max available pressure 31.5MPa, equipped with hand-operated direction valve to ensure single action and double acting of double jacks, flow speed control valve can adjust lifting and lowering speed and synchronism, unloading valve ensures needed pressure

Rated pulling force for each jack 180t, travel distance 55cm, equipped with two-way hydraulic locks and mechanical locks (hoop or screw jack) to ensure absolutely safe concreting condition

Flange of jacks is connected with piston rod by spherical hinge, can turn ?5?to ensure that jacks only bears axial force.

11.2 steel box girder lateral moving hydraulic system

Two sets hydraulic system are respectively installed at front and back of steel box girder at one side, each set has 1 set pump station, 2 pieces oil cylinders, 4 sets pump stations and 8 pieces cylinders in total.

Pump station is of middle and low pressure gear pump, available pressure 31.5MPa, equipped with hand-operated direction valve to ensure single action and double acting of double jacks, rated jacking force of one cylinder 30t, pulling force 15t, travel distance 30cm, double cylinders can ensure a smooth moving and an even bearing force of steel girder

 

11.3 longitudinal moving hydraulic system

2 longitudinal cylinders are set up at front and rear part of steel box girder at each side, 4 pieces in total, push force for each cylinder 30t, pulling force 15t, travel distance 100cm, longitudinal moving speed 0.5m/min, quick-change connector is installed at inlet and outlet of cylinder to not only work as stop valve and but also separate oil cylinder and oil pipe without leakage, convenient transportation.

One set hydraulic pump is used for longitudinal moving cylinder and lateral moving hydraulic system at front and rear end of steel box girder at the same side, max work pressure 31.5MPa

 

Configuration table for hydraulic system

 

Item	Specification	Quantity	Remark
Rated safe jacking force 180tHydraulic jack	Piston ?280/210?Travel distance 660mm	8 sets	Front legs 4 sets,rear legs, 4sets
30t double acting longitudinal movingHydraulic jack	?125/90?travel distance 1000mm	4 sets	2 sets for front support point at each side, used for longitudinal moving of ?MSS660
30t double acting lateral movingHydraulic jack	?125/90?travel distance 300mm	8 sets	4 sets for front, middle support point, used for lateral moving of MSS660 girder

 

12. Electrical control system

Electrical system uses AC, 3-phase, 4-wire, 380V, be connected into main power distribution cabinet, and then divided as two wires to send power to pump stations of steel box girder at two sides, total power about 75KW.