Steel mesh rack construction method skills

Steel mesh rack construction method skills

Steel mesh frame construction method skills

In the steel mesh frame with high altitude assembly method for installation, is first set up in the design position at the assembly bracket, and then use the crane to the mesh frame components in parts (or sub-blocks) suspended to the air at the design position, in the bracket for assembly. So, here is my steel structure net frame construction method skills for you to organize, welcome to read and browse.

High-altitude assembly method

Steel mesh frame with high-altitude assembly method for installation, is the first in the design position to set up the assembly bracket, and then use the crane to the mesh frame component parts (or sub-blocks) hanging to the air to the design position in the bracket for assembly. This method sometimes do not need large lifting equipment, but assembling bracket dosage, more work at height. Therefore, the high-strength bolt connection, steel mesh frame made of steel profiles or bolted ball nodes of the steel pipe mesh frame is more appropriate, there are still some steel mesh frame with this method of construction.

Installation of the whole method

The whole installation method is the first net frame on the ground assembled into a whole, and then lifting equipment will be lifted to the design position to be fixed as a whole. This construction method does not require a tall assembly bracket, less overhead work, easy to ensure the quality of welding, but requires a large lifting capacity of lifting equipment, technology is more complex. Therefore, this method is more suitable for the ball nodes of the steel net frame (especially the three-way net frame and other rod more net frame). According to the different equipment used, the overall installation method is divided into multi-machine lifting method, pulling rod lifting method, jack lifting method and jacking method.

1, multi-machine lifting method

This method is used for the height and weight are not big in the small and medium-sized network structure. Before installation on the ground on the net frame staggered assembly operations (that is, assembly position and installation axis staggered a certain distance to avoid the position of the column). Then use multiple cranes (mostly crawler cranes or automotive cranes) will be assembled net frame overall lifting to the top of the column above, in the air after shifting fall in place fixed.

(1) net frame assembly

In order to prevent the net frame as a whole when lifting and columns touch, staggered distance depends on the net frame lifting process net frame and columns or columns between the legs of the net distance, generally shall not be less than 10 ~ l125px, and at the same time, to take into account the convenience of the net frame assembled and the air shifted when the crane to facilitate the work. When needed, can consult with the design unit, part of the edge of the net frame rod left to the net frame after lifting and then welding, or change part of the impact of the net frame lifting the columns cattle legs.

After the steel net frame is processed in the metal structure factory, the single piece will be assembled into a small unit of plane truss or three-dimensional truss and transported to the construction site, and the construction site is assembled that is, the small unit of truss will be assembled into the whole net frame in the assembling position. The key of assembling net frame is to control the size of the axial support of the net frame (to preload the welding shrinkage) and the arching requirements.

The mesh frame welding is mainly the ball and steel pipe welding. The general use of equal strength butt welding, for safety reasons, in the butt welding at the additional welding 6 ~ 8mm fillet weld. Pipe wall thickness greater than 4mm of the weldment, the interface should be made into a bevel. In order to make the butt weld uniform and the length of the steel pipe can be slightly adjusted, can be added with casing. When assembling, the upper and lower chords are installed first, then the diagonal web is installed, and after all the steel pipes between two joists are put in and corrected, then weld the steel pipes one by one.

2) Net frame lifting

This kind of small and medium-sized net frame is mostly lifted by four crawler cranes (or automobile and tire cranes), and there are also two crawler cranes or a toggle crane lifting.

If the weight of the frame is small, or four cranes lifting capacity to meet the requirements, it is desirable to four cranes arranged on both sides of the frame, so that as long as the four cranes at the same time rotary that is the completion of the requirements of the frame air shifting, multi-machine lifting is the key to lifting the crane lifting speed is the same, otherwise there will be overloading of cranes, frame torsion, cracking of weld seams. For this reason, before lifting to measure the most each crane lifting speed, in order to lift the master.

When the net frame lifting to the top of the column than the elevation of about 750px, air displacement, the net frame to the top of the column above. When the net frame fall position, in order to make the net frame production line accurately coincide with the column top line, beforehand in the net frame four corners of a steel wire rope, the use of inverted chain for the line in place.

2, pulling rod lifting method

The ball node of the large steel pipe net frame. Installation, our country is currently used to pull the rod lifting method. With this method of construction, the net frame first staggered on the ground assembly, and then with a number of one-legged rod will be lifted to the net frame as a whole above the top of the column, the air displacement, drop installation.

(1) Aerial displacement principle

Aerial displacement is the key to this method. Aerial displacement is the use of each drawbar on both sides of the lifting pulley group in the horizontal force is not equal to make the horizontal movement of the net frame.

The net frame in the air displacement, requires at least two or more rods hanging net frame, and the same side of the lifting pulley block does not move, so in the net frame in the air displacement only panning and not tilt. Due to the same side of the pulley group does not move, so the net frame in addition to translation, but also produces can control the circumferential movement, and make the net frame to produce a little down. The direction of the net frame air displacement, and the arrangement of the drawbar.

(2) lifting equipment selection and arrangement

The selection and arrangement of lifting equipment is an important issue in the construction of the net frame toggle lifting. The content includes: drawbar selection and lifting point arrangement, cable wind rope and ground anchor arrangement, lifting pulley block and lifting point rigging wearing method, winch arrangement and so on.

The selection of the pulling rod depends on the load it bears and the arrangement of the lifting point. Net frame installation load calculation for:

Q=(K1 Q1+ Q2+ Q3)?K (kN)

where Q1?Net frame weight (kN);

K1?Load coefficient of 1.1 (such as the weight of the net frame can be calculated accurately as 1.0);

Q2?Additional equipment (including trusses, ventilation ducts, scaffolding, etc.) of the weight ( kN);

Q2?Additional equipment (including truss, ventilation ducts, scaffolding, etc.);

Q2?Additional equipment (including truss, ventilation ducts, scaffolding, etc.) of the weight ( kN);

K2?Additional equipment (including truss, ventilation ducts, scaffolding, etc.);

K2? kN);

Q3?Self-weight of spreader(kN);

K?Unevenness coefficient of force caused by lifting difference, such as the weight of the net frame is basically uniform, and the lifting difference of each point is controlled to be less than 250px, then this coefficient takes the value of 1.30.

Arrangement of lifting point of net frame is not only related to lifting program, but also related to the force performance of the net frame when lifting. During the lifting process, not only the internal force of some rods may exceed the calculated internal force, but also some rods may cause the sign of internal force to change and make the rods unstable. Therefore, the number and position of the lifting points should be determined by the calculation of the net frame lifting. However, under the premise of lifting capacity, lifting stress and rigidity of the net frame, the number of drawbars and lifting points should be minimized.

The arrangement of the wind rope, should make a number of rods connected to each other as a whole, in order to increase the overall stability. Each pulling rod should have at least 6 cable wind rope, cable wind rope according to the wind load, hanging weight, pulling rod deflection, cable wind rope initial stress and other loads, according to the most unfavorable combination of calculation after selection. The ground anchor also needs to be calculated to determine.

The force calculation of the lifting pulley set can be carried out in accordance with the actual force, and the specification of the pulley should be selected according to the calculation results.

The specifications of the winch, according to the size of the internal force of the lifting wire rope to determine. In order to reduce the difference between the catching lift, as far as possible to use the same specifications of the winch.

(3) Axis control

The position of the net frame assembly columns, should be based on the axis of the installed columns measured accurately, in order to eliminate the accumulation of axial error when the columns are installed.

(4) Removal of pull-out rods

After the suspension of the mesh frame, the pull-out rods are surrounded by the mesh frame, and it is desirable to dismantle them by inverted dismantling method. This method is to hang two sets of lifting pulley sets at the nodes of the upper chord of the mesh frame to hang the pulling rod, and then remove the toggle rod one section at a time from the bottom section.

3, electric screw lifting method

Electric screw lifting method is similar to the ascending board method, it is the use of ascending board construction of electric screw lifting machine, will be assembled on the ground steel mesh frame overall lift to the design elevation. The advantage of this method is that it does not require large lifting equipment, construction is simple. With electric screw elevator lifting steel frame, only vertical lift can not move horizontally. For this reason, the design should be considered in the two columns between the joist, the net frame of the pivot point falls on the joist.

As the net frame lifting does not move horizontally, so the net frame assembly does not need to be dislocated, can be assembled in place.

Aerial sliding method

Mesh roof in recent years, the use of high-altitude parallel sliding method of construction is gradually increasing, it is especially suitable for theaters, auditoriums and other projects. This construction method, the net frame more in the building on the roof of the hall set assembly platform for assembly (can also be set up in the audience hall stands assembly platform for assembly), to be the first assembly unit (or the first section) assembly is complete, it will be dropped to the slip track, with traction equipment to slip forward a certain distance. Next on the assembly platform assembly of the second unit (or the second section), assembled together with the first assembly unit (or the first section) together with the forward slip, so that section by section assembly constantly asked to slip forward until the entire frame assembled and slid to the position.

Splice the sliding of the net frame, can be set up under the net frame support roller, so that the roller in the sliding track sliding; can also be set up under the net frame support support base plate, so that the support base plate along the pre-embedded in the reinforced concrete frame beams embedded in the sliding steel plate.

The net frame sliding available winches or hand hoist traction. According to the size of the traction force and the bearing capacity of the rod between the net frame support, a point or multi-point traction can be used. When the net frame is sliding, the value of asynchrony at both ends should not be more than 50mm.

When the net frame is constructed by sliding method, the following calculations should be carried out in the process of sliding and assembling:

1) When there is no support in the middle of the span, the internal force of the rod and the deflection in the middle of the span;

2) When there is a support in the middle of the span, the internal force of the rod, the counterforce of the support and the deflection value.

When the mesh frame sliding unit due to the addition of intermediate slide caused by the internal force of the rod to change the number, temporary reinforcement measures should be taken to prevent instability.

The construction of net frame structure with overhead slip method, because the net frame assembly is carried out in the forecourt roof platform, reducing the danger of working at height; compared with the overhead assembly method, assembly platform is small, can save materials, and can ensure the quality of the net frame assembly; due to the net frame assembly with slip construction, can be constructed in parallel with the construction of the civil engineering and three-dimensional intersections, and thus can shorten the duration of the entire project; overhead slip method Construction equipment is simple, generally do not need large-scale lifting and installation equipment, so construction costs can also be reduced.

;