Taking gantry scaffolding as an example, the erection sequence of gantry scaffolding is as follows: place the base → install the first step frame on the base → install the shear brace → lay the foot pedal (or parallel frame) and insert the barge core → Install the gantry in the previous step → install the lock arm.

The connection of gantry scaffold at the corner of the building can be connected by short steel pipes and fasteners. The connecting short steel pipe shall be arranged at the top and away from the top of each step of the gantry to facilitate the laying of the foot plate and to add stiffness to the corner position.

The connection between the gantry scaffold and the corner of the building adopts a joint rod to ensure the overall volatility of the scaffold. The spacing of the joint rods shall not be greater than 4m per floor in the vertical direction, and a joint point shall be arranged for each 4m span in the degree direction. The pressure point of the inclined rod with the safety inclined baffle should be properly encrypted.

Regarding the entrance and exit of the building, the construction equipment attached to the wall and other holes that need to be left by scaffolding, the center of the vertical fracture can be handled by one-sided, partially dismantled after construction, and then reinforced with steel pipe, and the inclined steel pipe should be stopped and reinforced at the top two corners of the hole.

When the height of gantry scaffold is over 50m at a time, it is appropriate to set the scaffold on the steel beam, and specially formulate the corresponding construction plan.

The use of standard materials, according to the standard design, easy to site construction, there is considerable economy; The bearing capacity, stiffness and volatility of the scaffold are mainly considered. Under the above conditions, as much as possible to consider the flexibility of scaffolding, durability.

Before removing the scaffolding, the product maintenance measures on the exterior of the building should be done first, the debris and dregs on the scaffolding should be liquidated, and there is a careful scaffolding removal plan to stop the safety technology to the relevant personnel. Establish the alert area and relevant risk signs.

Scaffolding removal

The removal sequence of scaffold is just the opposite of the erection sequence, that is, top-down, post-installation first demolition, post-installation first demolition, and gradually stop.

Remove from the top of the scaffold, first remove the top handrail and railing post from one end of the scaffold, and then remove the foot pedal (or level frame) in succession to remove the escalator, insertion rod, door frame, and take out the barge core. When one scaffold is removed, the next scaffold is removed until the base.

When removing the connecting parts, the pin plate on the pin seat and the lock plate on the clamp should be opened first, and cannot be pulled hard. It is forbidden to damage the parts by knocking.

Material requirement

Ordinary overhang

1, the steel pipe foot floor stand, the outer diameter of 48mm, the wall thickness of 3.20mm, the steel strength grade Q235-A, the surface of the steel pipe should be straight and smooth, there should be no cracks, delamination, indentation, rowing and hard bending, the new steel pipe should have the factory certificate. Before the construction of the scaffold, the steel pipe must be sampled, sent to the relevant national qualification test unit, the steel pipe bending, tensile and other mechanical tests, the test results meet the design requirements, can be used in the construction.

2, the construction of steel pipe scaffolding using malleable cast fasteners, should meet the requirements of the Ministry of Construction "steel pipe foot hand fastener standard" JGJ22-85, provided by the fastener production license manufacturers, no cracks, porosity, shrinkage, sand holes and other forging defects, fastener specifications should match the steel pipe, paste surface should be dry, flexible parts, When clamping the steel pipe, the minimum opening distance is not less than 5mm. Do not damage steel pipe bolts when the tightening torque reaches 70N.m. If the old fastener is used, the fastener must be sampled and sent to the test unit with the relevant national qualification to carry out the sliding resistance test of the fastener, and the test results can be used in construction only after meeting the design requirements.

3, set up the shelf should be maintained, rust and uniform color, color strive to beautiful environment. The scaffolding poles, protective railings and kickers are painted yellow, and the shear brace is painted orange red. Bottom row pole and sweeping pole are painted red and white.

4. The use of foot plate and foot piece meets the relevant requirements.

5, the safety net adopts the mesh type safety net, the mesh should meet 2000 mesh /100cm2, do the penetration test does not penetrate, the weight of 1.6×1.8m single net is more than 3kg, the color should meet the environmental effect requirements, choose green. Requirements for flame retardant, the use of safety nets must have a product production license and quality certificate, as well as the Wenzhou construction safety supervision and management department issued a permit.

6, the wall parts are made of steel pipe, and its material should meet the requirements of Q235A steel in the current national standard "carbon steel structure" (GB/T 700).

7, the section steel horizontal suspension rod is made of No. 16a channel steel, and the inclined rod is made of 5.6 Angle steel 56 ×3 × 6.0mm steel pipe.

8, the diameter of the embedded bolt is 20.0 mm.

Setup process

Ordinary overhang

The process flow of overhanging scaffold erection is as follows: horizontal overhanging → longitudinal sweeping bar → vertical bar → horizontal sweeping bar → small cross bar → large cross bar (joist) → scissors brace → wall connecting parts → foot laying plate → protective railing → safety net.

Fixed distance positioning. According to the requirements of the structure, the distance between the inner and outer vertical rods and the wall should be measured with a ruler at the four corners of the building and marked; Straighten with a steel tape measure, separate the position of the vertical pole, and point out the vertical pole mark with a small bamboo piece; The backing plate and base should be accurately placed on the positioning line, and the backing plate must be laid flat and not suspended.

In the process of setting up the first layer of scaffolding, a diagonal support is set in each frame cell around the corner, and the corner can be added in both directions until the scaffold and the wall connecting parts of the main structure are reliably connected. When the scaffold operation layer is two steps higher than the wall piece, it is advisable to first set up the outer row and then set up the inner row. The rest click on the construction requirements to set up.

Main pole foundation

The foundation part of the scaffold in this project shall be rammed after backfilling, and concrete with strength grade not less than C15 shall be used for hardening, and the hardening thickness of concrete shall not be less than 10cm. The bearing capacity of the foundation can meet the requirements of the erection of the external scaffold (refer to the scaffold calculation book for specific calculation data).

Spacing of uprights

(1) The vertical distance of the scaffold pole is 1.5m, the transverse distance is 1.05m, and the step distance is 1.8m; The spacing between the wall rods is 3.6m vertical and 4.5m horizontal (that is, two steps and three spans) : the vertical rod is 0.3m from the building.

(2) The bottom pole of the scaffold is arranged with different lengths of steel pipes, so that the butt joints of the steel pipe pole are staggered, and the height direction is staggered more than 500mm, and the adjacent joints are required not to be synchronized within the same span to ensure the integrity of the scaffold.

(3) The vertical pole should be set up wood, and set the horizontal and horizontal direction sweeping rod, connected to the standing point pole, about 20cm from the base.

(4) The vertical deviation of the vertical pole should be controlled at no more than 1/400 of the height of the frame.

Cross bar setting

(1) The distance of the large cross bar in the height direction of the scaffold is 1.8m, so that the net can be hung. The large cross bar is placed inside the vertical pole, and the overhang length of each side is 150mm.

(2) The outer shelf is arranged at the intersection of the vertical bar and the large horizontal bar, and the two ends are fixed in the vertical bar to form the overall force of the spatial structure.

Scissor brace

Each end of the outer facade of the scaffold is provided with a scissor support, and should be continuously set from the bottom to the top; The net distance between the scissors in the middle should not be greater than 15m. The length of the diagonal bar should be splice, the splice length should not be less than 1m, and should be fixed by not less than 2 rotating fasteners. The scissors brace bar shall be fixed on the extended end or vertical bar of the transverse horizontal bar intersecting with the rotary fastener, and the distance between the center line of the rotary fastener and the main node shall not be greater than 150mm.

Laying requirement

(1) The scaffold should be laid between the vertical pole and the structural layer: the board width is 200mm, and the internal and external vertical poles should be covered with foot and hand boards, without probe boards.

(2) The full layer of foot pieces must be laid horizontally on the vertical wall, fully paved in place, leaving no vacancy, and effective protective measures must be taken where it cannot be fully paved.

(3) The foot and hand pieces must be tied in parallel with 18 lead wire double strands, not less than 4 points, requiring firm binding, smooth junction, laying to choose intact foot and hand pieces, found damaged to replace in time.

Protective railing

(1) The outer side of the scaffold is closed with a qualified green close-mesh safety net certified by the construction authority, and the safety net is fixed on the inner side of the scaffolding external pole.

(2) Choose 18 lead wire hanging safety net, requiring tight and smooth.

(3) The outside of the scaffold must be equipped with 1.2m high protective railings and 30cm high kicking rods, and the top row of protective railings must be no less than 2, with a height of 0.9m and 1.3m respectively.

(4) The inner side of the scaffold is formed (such as in the case of large open door and window holes, etc.), and 1.2m protective railings and 30cm high kicking rods are set on the inner side of the scaffold.

Walling piece

(1) The scaffold and the building are arranged in a horizontal direction of 4.5m and a vertical direction of 3.6m. If the floor height exceeds 4m, it is encrypted in the horizontal direction, such as when the floor height exceeds 6m, a cable-stayed wire rope is set every 6m in the horizontal direction.

(2) The pull node is encrypted within the Angle range and at the top, that is, within the Angle of l meters, a pull node is set every 3.6 meters in the vertical direction.

(3) The pull joint should be firmly secured to prevent its movement and deformation, and should be set at the contact point of the transverse rod size of the outer frame as far as possible.

(4) The pull joint of the exterior wall decoration stage must also meet the above requirements, and when the original pull joint is removed due to the construction needs, a reliable and effective temporary pull joint must be re-installed to ensure the safety and reliability of the outer frame.

Internal frame closure

(1) The net distance between the vertical rod and the wall of the scaffolding body is 200mm. If the limit of the structural design is greater than 200mm, the standing piece must be laid, and the standing piece is set flat and firm.

(2) The scaffold construction layer between the vertical pole and the building should be closed with foot pieces or wooden boards.

(3) The outer frame below the construction layer is closed every 3 steps and the bottom with a mesh or other measures.

The longitudinal spacing of the supporting structural steel is the same as that of the upper scaffold vertical rod, which is directly supported on the cantilever supporting structure. The upper scaffold pole and the supporting structure should have reliable positioning and connection measures to ensure the stability of the upper frame. Generally, 150-200mm steel pipe with an outer diameter of φ40mm is welded on the beam or longitudinal steel beam, and the sweeping bar is arranged at the lower part of the vertical bar.

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