Downstroke Movable Support System

MSS downstroke movable support system bridge making machine is bridge construction equipment using methods of cast-in-situ and span by span construction, designed to meet  continuous box girder construction.

The downstroke movable support system adopts support under the bridge deck, uses two groups of steel box girder to support pattern plate, and realizes the complete machine to move laterally and longitudinally to cross piers by main girder bringing with formwork and pattern plate. Equipped with 3 sets support legs, as starting pouring concrete beam, two sets legs as support, before crossing piers, the third set leg moves backward to be installed on pier at front of it, meeting the demand of crossing piers, span by span construction, moving backward repeatedly. The movable support system is equipped with 4 sets hydraulic systems to realize automatic jacking of formwork, lateral moving and longitudinal moving.

The machine is installed below the bridge floor, supporting the templates with two sets of steel box girder. The moving between the piers is carried through the transverse moving and longitudinal traveling of the main girder mould bases with the template. With three sets of support legs, two of them is used to supporting while casting the concrete girder. As the machine needs to move from one pier to next pier, the third support leg shifts to the front pier and fix on it in order to accomplish the task. The moving method of the machine is like this, one by one. Equip with four sets of hydraulic system, the machine can realize the jacking up, transverse and longitudinal traveling automatically.

The MSS650 is just a typical example.

Item/ Data /Model	MSS650
Span（m）	30
Girder-casting Weight(one time) (t)	650
Applicable Longitudinal/transverse Gradient	0.2-2.5％
Longitudinal Speed （m/min）	0.5
Self Weight（t）	300
Max Anti-force At Working （m/min）	316
Max Anti-force At moving(t)	103

MSS600 Downstroke Bridge Creating Machine is designed according to the <《Crane Design Standard》 (GB/T3811)
《Steel Structure Design Standard》 (GB50017)
《Code for Design of Highway Bridges and Culverts》 (JTJ021)
《The General Safety Technical Requirements for Engineering Machinery》 (JB/T6030)
《Code for Construction and Acceptance of Electrical Appliance Installation Engineering》 (GB50256)
《The General Technical Conditions for Hydraulic System》 (GB 3766)
《Code for Construction and Acceptance of Steel Structure》 (GB50205)
《Mechanical Properties of Fasteners—Bolts, Screws and Studs》 (GB 3098.1)

■ When the machine counters the conditions like: the continuous girder or transferring, it is equipped with the functions of counterweight mechanism and overall opening and closing.
■ The traveling method is walking hydraulic push-put, the support leg rearrangement needs the auxiliary facility.
■ The machine is double main girder, supporting with the corbel and piers.
■ The max. anti-force of the supporting beam is 316N at working.
■ The construction speed : 12 days for two piers ( later it will be 11 days for two piers).
■ The max. anti-support force of support roll while traveling: 103N.
■ Applicable longitudinal slope/lateral slope: 2%/2%.
■ The deflection of main girder: 1/700

■ Firstly the workmanship department evaluates the drawing.
■ Draw up the operation instruction then make the judgment.
■ According to the drawing, workmanship technology, manufacturing skill and assembly ability to further perfect the dimensions of the machine and meet kinds of requirements. Also do the detection for the mechanical parts.
■ Prepare the clamping apparatus according to the drawing.
■ Strictly control the quality in the process of production. 5.6，According to kinds of standards, strengthen the management and control in every part and production process.

Technology file drawing and project are handed to production department which assorts with related department and quality department to process, manufacture, control, check and accept of product.
The workshops do the following work according to drawing:
■ blanking splicing（technology and requirements of blanking splicing）
■ assembling welding（welding procedure card, welding technology qualification and welding record）
■ mechanical manufacture（mechanical manufacturing card）
■ finishing time of manufacture and patrolling card
■ Assembly（assembly technology）
■ checking descriptive chart（controlling the geometry size and key part）.

■ The tracing data of product is made up of contract, review file, drawing , calculation book of design, specification, installation project, raw material quality certificate, product quality inspection record, welding inspection report and purchased certificate.
■ leaving factory data is made up specification, installation project, certificate and receiving report etc.

■ Assemble the temporary supporting frame
■ Install the front and rear support legs, longitudinal traveling auxiliary support legs
■ Assemble the main girder
■ Assemble the hydraulic and electrical devices
■ Place the whole machine in the proper position
■ Install the cantilever beam
■ Assemble and hoist the base mould
■ Install the side mould frame
■ Adjust the base mould plate
■ Assemble the side mould plate and poles
■ Adjust the side mould plate
■ Install wing mould plate
■ Assemble the special-shape mould plate and pier top bulk mould
■ Carry the pressure and load test

Check the dimension, perpendicularity, pre-camber, deflection when the installation is done.
■ The overall dimension: 62.5m(L) ×20.6m(W) ×5.6m(H above the bridge)
■ The upper deflection of main girder: AF=(0.9/1000-1.4/1000)S
■ Adjust the pre-camber to approach the standard of the instructions
■ The main girder side curvature: AFP≤S/1200
■ Assemble and connect the high-strength bolt according to the standard

The operators must read the instructions carefully, and stick with the regulations to operate the machine. The specific requirements are as following:
■ Fasten the machine bottom with pier top and beam surface embedded parts while the support legs are working. The professional personnel must check it carefully before the next procedure.
■ After finishing the poles’ installation, the professional personnel must check it carefully before casting the beam.
■ No operations in the bad weather such as: strong wind, rain, heavy fog and icy snow.
■ No operation and working if the wind force has exceeded grade 7. Take some protection measures to guarantee the machine’s stability when the wind force exceeds grade 11.
■ Equip the lighting device when the machine operates at night in the working area and passageway to guarantee the construction safety.
■ Make sure that the traveling rail is smooth without the obstacles. g, The operators must accept the professional training and achieve the operations certificates of special equipment.

■ After construction are finished everyday, the workers must check the following content: if the level of main longitudinal girder meets the requirements or not; the connection of bolts and pins are firm or not; the electrical wires are broken and extruded; hydraulic system is regular or not; the track joints are plain and smooth or not; the connection of position limiter of crane and trolley are firm or not; the rail clamping device is in the working position or not; bed timber is plain and stable and the size of gauge is right or not etc.
■ The welding lines are checked every month :：upper and down chords of main girder , web plate, vertical welding lines of legs and the welding lines of connecting frame etc. The operators should stop working when the welding lines are broken or fatigue crack. When the users find the crack by eyes, but they can’t make sure the dangerous degree, so they should use the welding inspection instrument to test and then adopt reasonable steps to deal with.
■ About the painting of structure which should be painted again every two years. The users should clean the primary surface by steel brush and pay attention to the welding lines before the structure are painted.
The lifting mechanism, traveling mechanism of crane and trolley, reducer of motor and steel rope of winch are lubricated and maintained according the rules of specification.

The dismantling, transferring scheme is opposite with the installation scheme. The procedures are as following:
■ Choose the hoisting equipment according to the part weight
■ Disassemble the special shape mould plate and pier top bulk mould
■ Dismantle the wing mould plate
■ Disassemble the side mould plate and poles
■ Dismantle the base mould structure and plate
■ Disassemble the cantilever beam
■ Dismantle the main girder
■ Disassemble the front and rear support legs and auxiliary support legs
■ Loading and transferring