Scaffolding work

 

Development process and trend

In the early 1980s of last century, various types of scaffolding such as portal scaffold and bowl buckle scaffold were introduced from abroad。Portal scaffolding has been widely used in many projects in China and has achieved good results. Due to the product quality problems of portal scaffolding, this scaffold has not been widely promoted and applied。In the country has built a number of portal scaffolding production plants, most of its products are processed according to foreign companies。The bowl buckle scaffold is the most widely used scaffold in the new scaffold, but the use is not wide, and it is only used in some areas and some projects。

Since the 1990s, some domestic enterprises have introduced foreign advanced technology and developed a variety of new scaffolds, such as latch scaffolds, CRAB module scaffolds, disc scaffolds, square tower scaffolds, and various types of climbing frames。By 2013, there are more than 100 professional scaffolding manufacturers in China, mainly in Wuxi, Guangzhou, Qingdao and other places。Technically speaking, China's scaffolding enterprises have the ability to process and produce various new scaffolds。However, the domestic market has not yet formed, and the construction enterprise's understanding of the new scaffold is not enough。

With the emergence of a large number of modern large-scale building systems in our country, fastening steel pipe scaffolding can no longer meet the needs of construction development, and vigorously develop and promote the application of new scaffolding is a top priority。Practice has proved that the use of new scaffolding is not only safe and reliable construction, installation and disassembly speed is fast, and the amount of steel used in scaffolding can be reduced by 33%, the efficiency of installation and disassembly is increased by more than twice, the construction cost can be significantly reduced, and the construction site is civilized and clean。

 

特点

Different types of engineering construction choose different uses of scaffolding。Most of the bridge support frames use bowl buckle scaffolding, and there are also portal scaffolding。The main structure construction of the floor scaffold using fastener scaffold is mostly, the longitudinal distance of scaffolding pole is generally 1.2~1.8m;The horizontal distance is usually 0.9~1.5m。

Compared with the general structure, the working conditions of the scaffold have the following characteristics:

1, the load variability is large;

2, the fastener connection node is semi-rigid, and the stiffness of the node is related to the quality of the fastener and the installation quality, and the node performance has a large variation;

3. There are initial defects in the scaffold structure and components, such as the initial bending and corrosion of the rods, the erection size error and the load eccentricity are large;

4. The connection point with the wall has a large binding variation on the scaffold。 The research on the above issues lacks systematic accumulation and statistical data, and does not have the conditions for independent probability analysis. Therefore, the value of the adjustment factor of the structure resistance multiplied by less than 1 is determined by calibration with the safety factor used in the past。Therefore, the design method adopted in this specification belongs to semi-probability and semi-experience in essence。The basic condition of design calculation is that the scaffold meets the structural requirements specified in this code。

 

类型

Fastening type

1、优点

1) Large bearing capacity。When the geometric size and structure of the scaffold meet the relevant requirements of the code, under normal circumstances, the bearing capacity of the scaffold's single pipe column can reach 15kN ~ 35kN(1.5tf ~ 3.5tf, design value).。

2) Convenient installation and disassembly, flexible installation。Because the length of the steel pipe is easy to adjust and the fasteners are simple to connect, it can be adapted to various planes and facades of buildings and structures with scaffolding。

3) Relatively economic, simple processing, a low investment cost;If the geometry of the scaffold is carefully designed and the turnover rate of the steel pipe is improved, the amount of material can also achieve better economic results。Fastener steel pipe frame equivalent to about 15 kg of steel per square meter of construction。

2、缺点

1) Fastener (especially its screw) is easy to lose;

Bolt tightening torque should not be less than 40N·m, and should not be greater than 65N·m;

2) The bar at the node is eccentric connection, which transfers load and internal force by anti-sliding force, thus reducing its carrying capacity;

3) The connection quality of fastener nodes is significantly affected by the quality of fastener itself and the worker's operation。

3. Adaptability

1) Construct various forms of scaffolding, formwork and other support frames;

2) Assemble the derrick;

3) Erection of ramps, sheds, stands and other temporary structures,

4) As an aid to other kinds of scaffolding, strengthen the rods;

4. Set up requirements

In the erection of steel pipe fastening scaffold, attention should be paid to the formation of a solid foundation, the setting of a base and a backing plate, and reliable drainage measures to prevent water from soaking the foundation。

According to the setting of the wall pole and the size of the load, the transverse distance of the pole of the commonly used open double-row scaffold is generally 1.05~1.55m, masonry scaffolding step is generally 1.20~1.35m, decorative or masonry, decorative dual-purpose scaffolding is generally 1.80m, vertical distance 1.2~2.0m。Its allowable height is 34~50m。When it is set to a single row, the vertical bar transverse distance is 1.2~1.4 m, vertical distance 1.5~2.0m。The allowable height is 24m。

The longitudinal horizontal bar should be arranged on the inside of the vertical bar, and its length should not be less than 3 spans. The longitudinal horizontal bar can be butt fastener or lap joint。If the docking fastener method is used, the docking fastener should be staggered.If a lap connection is used, the length of the lap connection should not be less than 1 m, and three rotating fasteners should be fixed with equal spacing。

The main node of the scaffold (that is, the buckle point of the vertical rod, the longitudinal horizontal rod and the horizontal horizontal rod) must be provided with a horizontal horizontal rod connected with the right Angle fastener and is strictly prohibited to remove。The center distance between the two right-angle fasteners at the main node should not be greater than 150mm。In double-row scaffolding, the extension length of the transverse horizontal pole against the wall should not be greater than 0 of the transverse distance of the vertical pole.4 times, and should not be greater than 500mm;The horizontal bar at the non-main node on the working layer should be set at equal spacing according to the needs of the supporting foot and hand plate, and the maximum spacing should not be greater than 1/2 of the vertical distance。

The working layer should be fully covered and stable, leaving the wall 120~150mm;Narrow and long type handboards, such as stamped steel handboards, wooden handboards, bamboo string foot handboards, etc., should be set on three horizontal horizontal rods。When the length of the foot and hand plate is less than 2m, two horizontal horizontal rods can be used to support it, but both ends of the foot and hand plate should be reliably fixed to prevent tipping。The broad bamboo basketry foot board should be laid according to its main bamboo bar perpendicular to the direction of the longitudinal horizontal bar, and the use of butt tile, the four corners of the galvanized steel wire fixed on the longitudinal horizontal bar。

The bottom of each vertical pole shall be provided with a base or a backing plate。The scaffold must be equipped with vertical and horizontal sweeping rods。The longitudinal sweeping bar shall be fixed on the vertical bar at a distance of no more than 200mm from the base epithelium using right-angle fasteners。The horizontal sweeping bar shall also be fixed on the vertical bar immediately below the longitudinal sweeping bar by right-angle fasteners。When the vertical bar foundation is not at the same height, it is necessary to extend the longitudinal sweeping bar at the top to the lower part of the two spans and the vertical bar is fixed, and the height difference should not be greater than lm。The distance from the axis of the vertical pole above the slope to the slope should not be less than 500mm。

Portal steel pipe

1、优点

1) Standardized geometrical dimensions of portal steel scaffold。

2) Reasonable structure, good mechanical performance, make full use of steel strength, high bearing capacity。

3) Easy installation and disassembly during construction, high erection efficiency, labor saving and time saving, safe and reliable, economical and applicable。

2、缺点

1) There is no flexibility in the size of the frame, and any change in the size of the frame must be replaced with another type of gantry and its accessories

2) Cross support is easy to break at the middle hinge point;

3) The stereotyped foot plate is heavy,

4) The price is more expensive

3. Adaptability

1) Structural scaffolding

2) Support frame for beam and plate frame (bearing vertical load);

3) Structural activity table;

4. Set up requirements

1, the portal scaffold foundation must be rammed, and should do a good drainage slope to prevent water

2. The erection sequence of portal scaffold is as follows: foundation preparation → placement of cushion plate → placement of base → erection of two pieces of single portal frame → installation of cross rod → installation of foot plate → Repeat installation of portal frame, cross rod and foot plate on this basis。

3, the portal steel scaffold should be set up from one end to the other end, and the scaffolding should be set up after the scaffolding is set up。Set the direction opposite to the next step。

4, each step of scaffolding construction, should first insert two frames on the end base, and then install the cross rod fixed, lock the lock piece, and then set up the door frame, each take a pin, then install the cross rod and lock piece。

5, scaffolding must be set up with a reliable connection to the building。

6, the outside of the door buckle steel pipe scaffold should be set scissors, vertical and vertical should be set continuously。

Bowl snap

1、优点

1) Multi-function: According to the specific construction requirements, it can form single and double rows of scaffolding, support frame, support column, material lifting frame, climbing scaffold, suspension frame and other functional construction equipment。It can also be used to build facilities, sheds, lighthouses and other structures。Especially suitable for the erection of curved scaffolding and heavy support frame。

2) High efficiency: the longest common rod is 3130mm, weight 17.07kg。The disassembly speed of the whole frame is 3 to 5 times faster than the conventional, the disassembly is fast and labor-saving, and the workers can complete all the operations with a hammer, avoiding a lot of inconvenience caused by bolt operation。

3) Strong versatility: the main components are made of ordinary fastener steel pipe scaffolding, which can be connected with ordinary steel pipes with strong versatility。

4) Large bearing capacity: the vertical rod connection is the same axis socket, the transverse rod and the vertical rod are connected by the bowl buckle joint, and the joint has reliable bending resistance, shear resistance and torque resistance。Moreover, the axis line of each member is at one point, and the node is in the frame plane, so the structure is stable and reliable, and the bearing capacity is large。(The bearing capacity of the whole frame is improved, which is more than 15% higher than that of the fastener steel pipe scaffold with the same clear condition.)

5) Safe and reliable: When designing the joint, taking into account the spiral friction and self-gravity of the upper bowl buckle, the joint has a reliable self-locking ability。The load acting on the cross bar is transferred to the vertical bar through the lower bowl buckle, which has a strong shear resistance (up to 199kN).。Even if the upper bowl buckle is not pressed tight, the cross bar joint will not come out and cause an accident。At the same time, it is equipped with a safety net bracket, a cross bar, a foot board, a foot board, and a ladder。Pick a girder.Wall support and other rod accessories, safe and reliable use。6) Easy to process: the main component with Φ48×3.5, Q235B welded steel pipe, simple manufacturing process, moderate cost, can directly process and transform the existing fastening-type scaffolding.No complex processing equipment is required。

7) not easy to lose: the scaffold is not scattered and easy to lose fasteners, reducing the loss of components to a minimum。

8) Less maintenance: the scaffolding member eliminates the bolted connection.The structure is resistant to collision.General rust does not affect the disassembly operation, and does not require special maintenance and repair。

9) Easy to manage: the component series is standardized, and the exterior of the component is painted with orange。It is beautiful and generous, the components are stacked neatly, which is easy to manage the materials on site and meet the requirements of civilized construction。

10) Easy to transport: the longest component of the scaffold is 3130mtm, and the heaviest component is 40.53kg, easy to handle and transport。

2、缺点

1) The transverse rod is a stereotyped rod of several sizes, and the bowl buckle node on the vertical rod is pressed 0.6m spacing setting, so that the size of the frame is limited;

2) U-shaped connection pin is easy to lose;

3) The price is more expensive;

3. Adaptability

1) Construct various forms of scaffolding, formwork and other support frames;

2) Assemble the derrick;

3) Erection of ramps, sheds, stands and other temporary structures;

4) Structure strong combined support column;

5) Construct the support frame to withstand the transverse force;

disk-type

1) Easy and fast: easy and fast to build, and has strong mobility, can meet a wide range of operational requirements;

2) Flexible, safe and reliable: according to different actual needs, build a variety of specifications, multi-row of mobile scaffolding, a variety of perfect safety accessories, to provide firm and safe support in the operation;

3) Convenient storage and transportation: the disassembly storage occupies a small area, and can be promoted to facilitate transfer, and the parts can pass through various narrow channels。

Aluminium alloy

1. All parts of aluminum alloy scaffold are made of special aluminum alloy material, which is 75% lighter than traditional steel frame

2, high component connection strength: using the new cold work process of internal expansion and external pressure, the damage pulling force of the scaffold joint reaches 4100-4400Kg, which is much higher than the allowable pulling force of 2100Kg。

3. Easy and quick installation;Equipped with high-strength casters, movable。

4, the overall structure adopts the "building block" combination design, without any installation tools。

Aluminum alloy scaffolding to solve the problem of aerial work, it can be based on the actual need of the height of the lap, there are 2.32M/1.856M/1.392M Three height specifications。 There are two width specifications, wide and narrow。Narrow frame can be bonded on narrow ground, convenient and flexible。He can meet the requirements of high-altitude work in narrow Spaces such as wall corners and stairs, and is a good helper for enterprise high-altitude work。

 

Use requirement

 

安全

1, the construction of high-rise scaffolding, the various materials used must meet the quality requirements。

2. The foundation of high-rise scaffolding must be firm, calculated before construction, meet the load requirements, and set up according to construction specifications, and do a good job of drainage measures。

3, scaffolding construction technical requirements should comply with the relevant regulations。

4, must attach great importance to various structural measures: scissors support, pull joints, etc., should be set according to requirements。

5, horizontal closure: from the first step, every other step or two, full spread of foot or foot hand, foot and hand board along the long laying, the joint should overlap on the small bar, is strictly prohibited。And lay a long safety basketry every four steps between the vertical bar and the wall。

6, vertical closure: from the second step to the fifth step, each step needs to be set on the inside side of the outer row pole.00m high protective railings and foot boards or set up a net, the protective rod (net) and the vertical rod fastens;The fifth step above, in addition to the protection bar, should all set up safety fences or safety nets;In the streets or densely populated areas, safety fences or safety nets should be set up outside all from the second step。

7, scaffolding should be higher than the top of the building or operating surface 1.More than 5m, and additional enclosure。

8, the steel pipe, fasteners, foot plates and connection points on the scaffolding that has been set up shall not be dismantled at will。When necessary in the construction, it must be agreed by the person in charge of the site, and effective measures must be taken, and immediately resume after the completion of the process。

9, scaffolding before use, should be organized by the site person in charge of inspection and acceptance, acceptance and fill in the inspection form before use。During the construction process, there should be professional management, inspection and warranty, and regular settlement observation, and reinforcement measures should be taken in time if anomalies are found。

10, scaffolding removal, should first check the connection with the building, and the remaining materials on the scaffolding, debris and other clean, top-down, according to the first installation and demolition, after installation and demolition of the order, the removal of materials should be unified down or lifted to the ground, step by step。It is not allowed to use the step dismantling method, and it is strictly prohibited to throw down or dismantle by pushing (pulling) down。

11, scaffolding, should set up a warning area, and send a special guard。In case of six or more strong winds and bad weather, scaffolding demolition work should be stopped。

12, the requirements for the foundation, the foundation is not usually, please use the adjustable base foot to achieve balance。The foundation must be able to withstand the pressure of scaffolding and work。

13. The staff must wear safety belts when building and working at height. Please install safety nets around the work area to prevent heavy objects from falling and injuring others。

14. The components and accessories of scaffolding are strictly prohibited from seriously falling and bumping during transportation and storage;When connecting and disassembling, it is strictly forbidden to drop from the height. When disassembling, it should be operated in order from top to bottom。

15, pay attention to safety during use, it is strictly prohibited to play on the shelf, to prevent accidents。

16, work is important, safety, life is more important, please be sure to keep in mind the above content。

搭设

1, support rod type suspension scaffold erection requirements

The use load should be controlled and the erection should be firm。When setting up, the inner frame should be set up first, so that the cross rod extends out of the wall, and then the inclined rod is supported and connected firmly with the pick out cross rod, and then the overhanging part is set up, and the foot board is laid, and the outer railing and the foot board are set up, and the safety net is set up below to ensure safety。

2. Setting of wall parts

According to the axis dimensions of the building, one is set every 3 spans (6m) in the horizontal direction。In the vertical direction, one should be set every 3 to 4 meters, and the points are required to stagger each other to form a plum layout, and the construction method of the wall parts is the same as that of the floor scaffold。

3. Vertical control

When setting up, it is necessary to strictly control the perpendicularity of the segmented scaffold, and the allowable deviation of perpendicularity:

4. Foot and hand board laying

The bottom layer of the foot plate should be covered with thick wooden foot plate, and the upper layers can be covered with perforated light foot plate made of thin steel plate。

5, safety protection facilities

Guardrail and foot board should be set up in each layer of scaffolding。

The outside and bottom of the scaffold are closed with a close-mesh safety net, and the shelf and the building should maintain the necessary passage。

The connection between the erection pole and the erection beam (or longitudinal beam) of the cantilever scaffold。

150-200mm long steel pipe should be welded on the beam (or longitudinal beam), and its outer diameter is 1 smaller than the inner diameter of the scaffolding pole.0~1.5mm, connected with fasteners, and 1 to 2 sweeping rods are set under the vertical rod to ensure the stability of the shelf。

6. Connection between cantilever beam and wall structure

Iron parts should be buried in advance or holes should be left to ensure that the connection is reliable, and holes should not be punched casually to damage the wall。

7. Inclined tie rod (rope)

The inclined tie rod (rope) should be equipped with a tightening device so that the tie rod can bear the load after tightening。

8. Steel support

Steel support welding should ensure that the weld height and quality meet the requirements。

技术

1, no matter what type of scaffolding is set up, the material and processing quality of the scaffold used must meet the specified requirements, and the use of unqualified materials to set up scaffolding is absolutely prohibited to prevent accidents。

2, the general scaffold must be set up according to the scaffold safety technical operating procedures, for the height of more than 15m high-rise scaffolding, there must be design, calculation, detailed drawing, there is a construction plan, there is the approval of the technical person in charge of the next level, there is a written safety technology disclosure, and then can be set up。

3, for dangerous and special hanging, picking, hanging, jack, pile and other shelves must also be designed and approved.Only when separate safety technical measures are prepared can they be set up。

4, the construction team after accepting the task, must organize all personnel, carefully understand the scaffolding special safety construction organization design and safety technical measures, discuss the installation method, and send good technology, experienced technical personnel responsible for the installation of technical guidance and monitoring。

验收

After erection and assembly of the scaffold, it shall be checked and accepted before operation。The supervisor, the shelf team leader and the full-time safety and technical personnel should organize the acceptance and fill in the acceptance form layer by layer and step by step。Acceptance requirements are as follows:

1, the basic treatment of scaffolding, method, buried depth must be correct and reliable。

2, the layout of the shelf, the vertical rod, the size of the bar spacing should meet the requirements。

3, the erection and assembly of the shelf, including the choice of tool rack and focus should meet the requirements。

4, the wall point or the fixed part of the structure should be safe and reliable;Scissor brace and diagonal brace should meet the requirements。

5, the safety protection of scaffolding, safety device to be effective;Fastening and binding should be tightened in accordance with regulations。

6, the hoisting equipment of scaffolding, steel wire rope, derrick installation, etc., should be safe and reliable, and the laying of feet and hands should comply with the regulations。

 

Q&A

设计

(1) Heavy scaffolding should have a clear understanding, generally if the floor thickness is more than 300mm, it should be considered in accordance with the heavy scaffold design, scaffold load more than 15KN/㎡, then the design should be organized expert demonstration。It is necessary to distinguish those parts of the steel pipe length change has a greater impact on the bearing capacity，For the template bracket, it should be considered that the center line of the top horizontal bar should not be too long from the length a of the template support point，Generally less than 400mm is appropriate (may need to be revised in the new specification)，In general, the uppermost step and the bottom step have the greatest force when the vertical rod is calculated，Should be the main calculation point。When the bearing capacity is not satisfied with the requirements of the group, the vertical rod should be increased to reduce the vertical and horizontal spacing, or the horizontal rod should be increased to reduce the step distance。

(2) Domestic scaffolding generally exists steel pipe, fasteners, top support and bottom support material quality unqualified, the actual construction of the theoretical calculation did not take into account these, it is best to take a certain safety factor in the design calculation process。

施工

Bar missing，The vertical and horizontal joints are not connected, and the distance between the sweeping bar and the ground is too large or too small;The foot plate is cracked, the thickness is not enough, and the lap joint does not meet the standard requirements;After the large formwork is removed, there is no anti-fall net between the inner vertical pole and the wall;The scissors are not continuous in the plane;Open scaffold is not provided with diagonal brace;The distance between small cross bars under the foot and hand plate is too large;The wall parts are not rigidly connected inside and outside;The distance between protective railings is greater than 600mm;Fastener connection is not tight，Fastener slip, etc。

Deformation accident

(1) Local deformation of scaffolding caused by foundation settlement。Set up an eight-word hip or scissors brace on the cross section of the double frame, and set up a group of vertical poles in a row until the deformation area is arranged outside。The hip or scissors leg must be placed on a solid, reliable foundation。

(2) The deflection deformation of the cantilever steel beam on which the scaffold is rooted exceeds the specified value, and the anchorage point of the cantilever steel beam should be strengthened, and the steel support and U-shaped brackets above the steel beam should be tightened to withstand the roof。There is a gap between the embedded steel ring and the steel beam, and it must be tightened with a horse wedge。The outer end of the hanging steel beam is checked one by one and all tightened to ensure uniform force。

(3) If the unloading and pulling system of the scaffold is damaged locally, it should be restored immediately according to the unloading and pulling method formulated in the original plan, and the deformed parts and rods should be corrected。Such as correcting the deformation of the scaffold outward tension, first set a 5t chain according to each opening, tighten with the structure, loosen the rigid pull contact, and tighten the chain inward at the same time, until the deformation is corrected, do a good job of rigid pull, and tighten the steel wire rope at each unloading point, so that the force is uniform, and finally let go of the chain。