Scaffolding in the city isolates the interior and exterior of buildings, creating a protective space that belongs to the building.
They sometimes cover the exterior of the building like a layer of cicada clothing, both safe and spectacular, and sometimes become an eternal part of the building in a temporary posture. Sometimes it only exists in a small area under restoration, which is a flexible space in an architectural work.
How to avoid the risk of collapse hidden under the beautiful cicada coat? Let’s take a look together.
Key points for preparing construction plans
Vertical and horizontal bars
(1) The longitudinal horizontal pole should be set on the inner side of the upright pole, and the length of a single pole should not be less than 3 spans.
(2) The extension of longitudinal horizontal bars should be connected or overlapped using butt fasteners, and should comply with the following regulations: the joints of two adjacent longitudinal horizontal bars should not be set within the same synchronization or span; The distance between two adjacent joints that are not synchronized or span different distances in the horizontal direction should not be less than 500mm; the distance from the center of each joint to the nearest main node should not be greater than one-third of the longitudinal distance; The overlap length should not be less than 1m, and 3 rotating fasteners should be set at equal intervals for fixation; The distance from the edge of the end fastener cover plate to the end of the overlapped longitudinal horizontal rod should not be less than 100mm.
(3) The bottom step distance of double row scaffolding should not exceed 2m.
(4) Single row, double row, and full hall scaffolding poles must be connected with docking fasteners at all levels and steps except for the top step.
(5) The docking and overlapping of scaffolding poles should comply with the following regulations: when the poles are lengthened by docking, the docking fasteners of the poles should be arranged in a staggered manner, and the joints of two adjacent poles should not be set in synchronization. The distance between the two spaced joints of one pole in synchronization should not be less than 500mm in the height direction; the distance from the center of each joint to the main node should not be greater than 1/3 of the step distance; When the vertical pole is extended by overlapping, the overlapping length should not be less than 1m and should be fixed with no less than 2 rotating fasteners. The distance from the edge of the end fastener cover plate to the end of the rod should not be less than 100mm.
Sweeping rod
(1) Scaffolding must be equipped with vertical and horizontal sweeping rods. The vertical sweeping rod should be fixed to the upright pole at a distance of no more than 200mm from the bottom of the steel pipe using right angle fasteners. The horizontal sweeping rod should be fixed to the upright rod immediately below the vertical sweeping rod with right angle fasteners.
(2) When the foundation of the scaffold pole is not at the same height, the longitudinal sweeping rod at a higher height must be extended two spans downwards and fixed to the pole, with a height difference of no more than 1m. The distance from the axis of the pole above the slope to the slope should not be less than 500mm.
(3) The top railing of the scaffold pole should be 1m higher than the upper end of the parapet wall and 1.5m higher than the upper end of the eaves.
cross bracing
(1) The setting of diagonal braces for single and double row scaffolding should comply with the following regulations: the number of diagonal braces that cross the upright pole should be determined according to the specifications in the table. The width of each diagonal brace should not be less than 4 spans and should not be less than 6 meters. The inclination angle between the diagonal brace and the ground should be between 45 ° and 60 °; The diagonal brace should be fixed to the extended end or upright of the intersecting horizontal bar using a rotating fastener, and the distance from the centerline of the rotating fastener to the main node should not exceed 150mm.
(2) The docking and overlapping of scaffold uprights shall comply with the following regulations: when the uprights are extended by overlapping, the overlapping length shall not be less than 1m, and no less than 2 rotating fasteners shall be used for fixation. The distance from the edge of the end fastener cover plate to the rod end should not be less than 100mm. Three rotating fasteners are required to be used for fixation on site.
(3) The diagonal brace should be fixed to the extended end or upright of the intersecting horizontal bar using a rotating fastener, and the distance from the centerline of the rotating fastener to the main node should not exceed 150mm.
(4) Double row scaffolding with a height of 24m or more should have continuous diagonal braces installed on the entire outer facade; Single and double row scaffolding with a height of less than 24m must be equipped with a diagonal brace on the outer two ends, corners, and elevations with a spacing of no more than 15m in the middle, and should be continuously set from bottom to top.
(5) The horizontal slant support of double row scaffold shall be set in accordance with the following provisions: the horizontal slant support shall be placed in the same section in a zigzag continuous manner from the bottom to the top; The enclosed double row scaffold with a height of less than 24m may not be equipped with transverse slant support. For the enclosed scaffold with a height of more than 24m, except for the corner, a transverse slant support shall be set in the middle every 6 spans.
Transverse slant support
Both ends of open type double row scaffold must be provided with transverse slant support.
slanted ladder
(1) The type of pedestrian and material transportation ramp should be determined according to the following requirements: scaffolding with a height of no more than 6m should use a straight inclined ramp; Scaffolds with a height greater than 6m should use zigzag ramps.
(2) The construction of ramps should comply with the following regulations: ramps should be attached to external scaffolding or buildings; The width of the material transport ramp should not be less than 1.5m, and the slope should not exceed 1:6; The width of pedestrian ramps should not be less than 1m, and the slope should not exceed 1:3; A platform should be set up at the corner, and its width should not be less than the width of the ramp; Both sides of the ramp and the periphery of the platform should be equipped with railings and toe boards. The height of the railing should be 1.2m, and the height of the toe board should not be less than 180mm.
(3) The construction of ramp scaffold boards should comply with the following regulations: when laying the scaffold boards horizontally, longitudinal support rods should be added under the horizontal BIM learning horizontal bars, and the spacing between the longitudinal support rods should not exceed 500mm; when laying the scaffold boards smoothly, the joints should be overlapped, and the lower board head should press the upper board head, and the convex edges of the board head should be filled with triangular wood; A non slip wooden strip with a thickness of 20-30mm should be installed every 250-300mm on the scaffold boards of pedestrian ramps and material transport ramps.
Scaffold safety protection
Floor standing external scaffolding
1. Frame foundation
(1) Vertical and horizontal sweeping rods are installed 150mm below the upright pole, with the vertical sweeping rod above and the horizontal sweeping rod below, both connected to the upright pole. (2) When the foundation of the scaffold pole is not at the same height, the longitudinal sweeping rod at a higher height must be extended two spans downwards and fixed to the pole, with a height difference of no more than 1m. The distance from the axis of the pole above the slope to the slope should not be less than 500mm.
2. Rod arrangement
(1) The scaffold construction operation surface must be fully covered with scaffold boards, with a distance of no more than 20cm from the wall, and there must be no gaps, probe boards, or flying boards. (2) A protective railing and a 20cm high toe board should be installed on the outer side of the operating surface. (3) When the distance between the inner pole and the building is greater than 150mm, it must be enclosed. (4) When the clearance distance below the operating surface of the scaffolding construction layer exceeds 3.0m, a horizontal safety net must be set up. If the horizontal net between the double row scaffolding entrance and the external wall of the structure cannot be protected, scaffolding boards can be laid. (5) The frame must be enclosed along the inner side of the outer frame with a dense mesh safety net. The safety nets must be firmly connected, tightly sealed, and fixed to the frame. (6) Four upright poles should be installed at the corners of the frame, and the large horizontal bars should be connected and sealed. (7) The connection between the inner and outer uprights should be perpendicular to the structural boundary of the building, and small horizontal bars must be installed closely to each set of uprights. (8) The upright pole must be butt jointed except for the top layer, and the large horizontal bar can be overlapped outside the corner of the frame. Scissor braces must be overlapped. (9) Scissor braces and wall connecting components must be erected and dismantled simultaneously with the external scaffolding, and it is strictly prohibited to install or dismantle them later or first.
3. Wall connecting component setting
(1) The spacing between wall connecting components should not only meet the calculation requirements, but also not exceed the maximum spacing. (2) Wall connecting components should be placed close to the main node, and the distance from the main node should not exceed 300mm. (3) They should be set from the first vertical horizontal bar on the bottom layer, otherwise other reliable measures should be taken to fix them. (4) It is advisable to use diamond shaped layout, but square or rectangular layout can also be used; The two ends of the straight and open scaffolding must be equipped with wall connectors, and the vertical spacing between the wall connectors should not exceed the height of the building and should not be greater than 4m. (5) For single and double row scaffolding with a height of less than 24m, rigid wall connectors should be used to reliably connect with the building, or a wall attachment connection method that combines tension bars and top supports can be used. The use of flexible wall connectors with only tension bars is strictly prohibited. (6) Double row frames with a height of over 24m must be reliably connected to the building using rigid wall connectors. (7) The connecting rods or tie bars in the wall connecting components should be set horizontally. When they cannot be set horizontally, the end connected to the scaffold should be connected diagonally downwards instead of diagonally upwards.
4. Dense mesh safety net
(1) The dense mesh safety net should meet the requirement of 2000 mesh/100cm2. (2) The safety net must be tightly hung, with tight corners, reasonable support, and even force distribution; The overlap should be tight and secure, without any gaps. (3) The safety net must not be removed or damaged during construction, and must only be removed when there is no high-altitude operation.
5. Facade protection settings
(1) The steel pipes of the scaffold should be horizontal and vertical, and the steel pipes at the corner position should not exceed 200mm of the corner. The exposed part of the small horizontal bar should be uniform. (2) The upright poles of the scaffold should be evenly distributed, usually 1500mm, and the horizontal bars should be kept horizontal, usually 1800mm. Each step of the scaffold should be equipped with a waist guard, usually 600mm and 1200mm. (3) A dense mesh safety net should be hung on the outside of the scaffold, and the net body should be connected vertically using a mesh connection method. Each mesh should be fixed with 16 gauge iron wire and copper pipe; When connecting the net horizontally, the overlapping method should be adopted, and the overlapping length should not be less than 200mm. Wooden beams should be set as inner lining at the corner of the frame to ensure the safety of the net strip at the corner of the frame. (4) The surface of the outer row of scaffolding poles should be painted yellow, and a 200mm high kickboard should be set up every one or two sets of diagonal braces, fixed on the outside of the poles. The surface of the kickboard should be painted with red and white warning colors. (5) A horizontal bar must be installed at the main node, fastened with right angle fasteners, and must not be removed.
Elevator shaft operating frame
1. Segmented cantilever
(1) During the construction of the main structure, a 150 × 150mm square hole shall be reserved inside the wall, and 2 No. 16 I-beams shall be used as the operating frame support. Set up segmented overhangs, with a height of no more than 20m and a step distance of no more than 1.6m. (2) Hang a horizontal net on the construction layer, and set up a horizontal protection every two layers below the construction layer and no more than 10m.
2. Elevator shaft steel platform
(1) The size of the elevator shaft steel platform is determined based on the size of the elevator shaft. The main beam is made of four 14 gauge channel steel welded back-to-back in two groups, the secondary beam is made of 10 gauge channel steel, and the platform plate is welded with 4mm thick patterned steel plate. (2) Reserve 150 × 1500mm square holes in the wall and use 4 No. 14 I-beams to pass through the wall as frame supports. The I-beams should extend no less than 300mm from the inner well wall, and the ends should be fully welded with 300mm × 300mm × 4mm steel plates. (3) Weld 4 Φ 60 steel pipe sleeves on the upper part of the platform, and fix the upright pole of the operating frame inside the sleeves using screws for connection. (4) The distance between the elevator shaft platform and the shaft wall should be less than 100mm.
3. Automatic support steel platform
(1) The size of the elevator shaft steel platform is determined based on the size of the elevator shaft. The main beam is made of four 14 gauge channel steel welded back-to-back in two groups, the secondary beam is made of 10 gauge channel steel, and the platform plate is welded with 4mm thick patterned steel plate. (2) Reserve 150 × 150mm square holes in the wall. (3) The support legs are welded with 8mm steel plates and equipped with a Φ 40 circular hole. They are connected to the main beam of the platform through iron pins with a diameter of 38mm. The support legs can automatically rotate during the lifting process and reset under the action of counterweight after lifting is completed. (4) Weld 4 Φ 60 steel pipe sleeves on the upper part of the platform, and fix the upright pole of the operating frame inside the sleeves using screws for connection.
4. Elevator shaft protective frame
(1) Two Φ 48.3 × 3.6mm steel pipes are inserted into the reserved holes, and the outer ends of the steel pipes are connected and fixed with copper pipe fasteners to prevent slipping. (2) Lay 50 × 100mm wooden beams on the steel pipe platform, and cover them with hard materials for sealing or hanging safety nets for protection.
5. Elevator shaft with floor lifting platform
The lifting platform on the same floor is an integral tool type operating platform, with its size determined by the size of the elevator shaft. The platform steel beam is made of 18 gauge channel steel, and the upright pole is made of 14 gauge detachable I-beam. The main beam is welded with a 22mm diameter round steel as the lifting point.
Suspended scaffolding
(1) The floor is pre embedded with a Φ 20 U-shaped screw, and each steel beam is equipped with a Φ 16 steel wire rope as a safety rope.
(2) The specific specifications and models of I-beams, anchoring screws, and diagonal steel wire ropes shall be determined based on the scheme calculation sheet.
(3) The anchor ring is embedded in PVC pipe before pouring concrete, and the screw thread is protected with tape.
(4) The bottom of the scaffold should be equipped with sweeping rods along the longitudinal and transverse directions according to the specifications. Steel bars should be welded on the surface of the cantilever beam to fix the upright rods. Wooden beams should be laid along the length direction of the scaffold above the horizontal bars, and formwork should be fully laid for protection.
(5) A 200mm high kickboard should be installed on the inner side of the bottom pole of the scaffold; The bottom should be fully enclosed with hard materials.
(6) The angle between the steel wire rope and the steel beam should be between 45 ° and 60 °.
(7) At a distance of 100mm from the end of the cantilever steel beam, a steel bar with a length of 80mm and a diameter of 25mm is welded horizontally below to fix the steel wire rope.
(8) The pre embedded lifting ring should use smooth round steel bars, with a diameter not less than 20mm (or determined by calculation).
(9) The specific type and length of steel beams to be selected will be determined based on the calculation results.
(10) After the installation of the cantilever steel beam, weld 200mm high steel bars as the positioning point for the upright pole.
(11) The fixed length of the cantilever steel beam should not be less than 1.25 times the cantilever length.
(12) The support points of cantilevered steel beams should be set on the structural beams and should not be set on the overhanging balconies or cantilevered slabs.
(13) In addition to using U-shaped screws, the following revolving anchor rings can also be used for pre embedded rings. The anchor ring is made of round steel with a diameter of 20mm, which is penetrated by large eyes on a 10mm thick base and fully welded to the base. The round steel is 35cm long, the base is 30cm long, and 8cm wide. The upper end of the round steel is 15cm for threading, and it is embedded in PVC pipes in the floor slab. After use, it is removed and reused.
Attachment type lifting scaffold
The construction of attached lifting scaffolding must strictly prevent the following phenomena from occurring.
(1) The height of the peripheral protection is lower than the operating surface. Due to the use of aluminum molds, the K-plate could not be removed after the concrete pouring was completed, resulting in the top support having nowhere to attach, which affected the lifting of the climbing frame and caused the operating surface to be higher than the protection. At this point, it is necessary to strengthen team coordination and optimize the K-plate at the support to avoid the problem from persisting.
(2) There is a serious accumulation of materials such as templates on the climbing frame. Steel bars, aluminum formwork components, screws and other materials are piled up everywhere on the climbing frame, posing a risk of falling objects from high altitude and overloading.
(3) Inadequate protection. The partition position, lateral steel plate protection of the cantilever section at the top of the frame, hard isolation at the bottom of the frame, and isolation at the operating layer are not in place.
(4) The anchoring of the attached support is not in place. The double nut of the support screw is not set in place, and there is concern about concrete contamination of the thread, intentionally failing to thread it; Part of the supports were cantilevered, and the diagonal braces were not set up in a timely manner; Unreasonable positioning of support bolt holes leads to cracking.
(5) The anti fall device has failed. The anti fall device is misaligned, the anti fall teeth are not tightened, and the anti fall device is heavily contaminated.
(6) Lift the support anchorage. Insufficient concrete strength at the anchorage point when increasing the bearing force, resulting in excessive deformation and cracking of structural components; When lifting the support, the load is relatively high, and the anchoring position such as the balcony edge beam is subjected to excessive force beyond the design, resulting in cracks in the structure.
(7) Climbing frame lifting. The lack of attachment support caused the upper cantilever to be too large, resulting in the main frame turning outward.
(8) Support fixation. There is only one bolt on the support, and the bottom of the support is not firmly attached to the structure, which poses a risk of instability of the support.
(9) The device is severely corroded. Electric hoists, attached supports, etc. lack maintenance and are severely corroded.
Suspended unloading platform
(1) The unloading platform shall not be directly or indirectly connected to the external scaffolding structure.
(2) Steel pipes are used to build protective railings around the platform, and the inner formwork of the protective railings is fully enclosed. The distance between the uprights is 1000mm.
(3) The bottom of the unloading platform should be welded and fixed with patterned steel plates, and the gap between it and the outer frame should also be closed.
(4) Fixed protective railings are installed on both sides of the unloading platform, and their uprights are welded and fixed to the main cantilever beam; The horizontal slant support of the unloading platform is welded to the connection position of the secondary beam channel steel.
(5) The inner side of the protective railing should be enclosed with steel mesh and hung with load limit signs.
(6) The horizontal bars at the outer platform should be overlapped to ensure smooth installation and use of the unloading platform after disassembly and modification.
(7) During the use of the unloading platform, both sides and the front should be vertically enclosed with templates to prevent debris from falling.
(8) Hang a unloading platform signboard on the right side of the platform enclosure.
(9) A movable protective door can be installed on the front side of the cantilever unloading platform. When lifting long steel pipes and square timber, the protective door can be opened and placed in the groove. It is more convenient to tie the steel wire rope to avoid stacking long materials on the protective baffle.
(10) A lifting net is installed under the suspended unloading platform to prevent falling objects from injuring people.
Key points of acceptance
Scaffold foundation and foundation acceptance
(1) The construction of scaffolding foundations and foundations must be calculated according to relevant regulations based on the height of scaffolding installation and the soil conditions of the installation site; (2) Whether the scaffold foundation and foundation are compacted; (3) Whether the foundation and foundation of the scaffold are flat; (4) Whether there is water accumulation in the foundation of the scaffold.
Acceptance of scaffold frame drainage ditch
(1) Remove debris from the scaffolding construction site, level it, and ensure smooth drainage; (2) The setting of drainage ditches should be between 500-680mm outside the outermost column of the scaffold; (3) The width of the drainage ditch is between 200-350mm; Depth: between 150-300mm; A collection well (600mm × 600mm × 1200mm) should be installed at the end of the ditch to ensure timely drainage of water from the ditch; (4) The upper width of the drainage ditch is 300mm; the lower width is 180mm; (5) the slope of the drainage ditch is 0.5.
Acceptance of scaffold pads and bottom supports
(1) The acceptance of scaffold pads and bottom supports is determined based on the height and load-bearing capacity of the scaffold; (2) The specifications for the base plate of scaffolding below 24m are (width greater than 200mm, thickness greater than 50mm), ensuring that each pole must be placed in the middle of the base plate, and the area of the base plate must not be less than 0.15m ²; (3) The thickness of the bottom pad for scaffolding with a load-bearing capacity of over 24m must be strictly calculated; (4) The bottom support of the scaffold must be placed at the center of the cushion plate; (5) The width of the scaffold bottom support shall be greater than 100mm and the thickness shall not be less than 50mm.
Acceptance of scaffold sweeping rods
(1) The sweeping rod must be connected to the upright pole and must not be connected between sweeping rods; (2) The horizontal height difference of the sweeping pole shall not exceed 1m, and the distance from the slope shall not be less than 0.5m; (3) The longitudinal sweeping pole shall be fixed on the upright pole at a distance of not more than 200mm from the base surface with right angle fasteners; (4) The horizontal sweeping rod should be fixed on the upright rod immediately below the vertical sweeping rod with right angle fasteners.
Acceptance criteria for scaffold boards
(1) The scaffolding on the construction site must be fully laid and the scaffold boards must be aligned correctly. At the corners of the scaffolding, the scaffold boards should be staggered and overlapped, and must be tied firmly. Uneven areas should be leveled and nailed with wooden blocks; (2) The scaffold boards on the working level should be flat, tightly packed, and securely tied to the prefabricated house. The length of the scaffold board probe at the end, which is 12-15cm away from the wall, should not exceed 20cm. The spacing between horizontal bars should be set according to the usage of the scaffold. The scaffold boards can be laid flat or overlapped.
Acceptance of scaffolding scissor braces
(1) Scaffolds over 24m in height must have a diagonal brace installed at each end of the outer facade, and should be continuously installed from bottom to top. Multiple continuous scissor braces are installed inside the load-bearing and special shelves from bottom to top. The inclination angle between the diagonal rods of the scissor braces and the ground should be between 45 ° and 60 °. The width of each scissor brace should not be less than 4 spans and should not be less than 6m. (2) When the frame height is higher than 24m, scissor braces must be continuously installed from low to high.
Acceptance of scaffolding up and down measures
(1) There are two types of measures for scaffolding: hanging ladders and setting up shaped or inclined walkways. (2) The ladder hanging must be continuously and vertically arranged from low to high, and must be fixed every 3m vertically. The top hook should be securely tied with No. 8 lead wire. (3) The up and down walkways must be erected at the same height as the scaffolding. The width of the pedestrian walkway must not be less than 1m, with a slope of 1:6. The width of the material transport walkway must not be less than 1.2m, with a slope of 1:3. The spacing between anti slip strips is 0.3m, and the height of the anti slip strips is about 3-5cm.
Acceptance of anti fall measures for scaffolding
(1) If safety nets need to be hung on construction scaffolding, the safety nets must be flat, firm, and complete. (2) The outer side of the construction scaffold must be equipped with a dense mesh, which must be flat and complete. (3) Anti fall measures should be taken every 10-15 meters at the vertical height of the scaffold, and a dense mesh should be set up on the outside of the scaffold in a timely manner. When laying the inner safety net, it must be tightened, and the safety net fixing rope must be wrapped around the securely fastened point.
Article source: Architectural Technology Magazine
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