Large span curved steel space frame installation

With the continuous improvement of the science and technology of the construction industry, the installation technology of the super large roof system has also developed rapidly. Most of the commonly used construction methods adopt a full frame bulk and ground assembly method of high altitude hoisting method. However, the two methods have their own advantages and disadvantages. For example, it is equipped with a full frame and medium sized bulk method. The scaffolding materials are many, the process is cumbersome, the construction cycle is long and the turnover efficiency is low; Although the construction speed of the ground assembly high altitude lifting method is fast, but the lifting is difficult, the risk coefficient is high, and the large machinery is needed, and the use cost is high. The installation system of super span arc steel space frame is a mobile platform, which can be installed by sliding, which can save turnover materials, flexible and convenient installation, short construction period and low cost. The super span arc steel space frame can be applied to all kinds of exhibition halls, industrial plants and large warehouses with large span, high arch and long longitudinal. Therefore, more and more attention has been paid to the arc super span steel space frame structure in domestic roof system.

1.Process principle

According to the steel space frame design and construction drawings, the movable operation platform unit and track system are designed by computer. The operation platform structure is designed according to the “construction fastener type steel tube scaffold safety technical Specification” JGJ130 (2011). The roller is designed according to the mechanical principle. After installing the first cross zone steel space frame and passing the acceptance, the operation platform will be pushed along the longitudinal direction, and the steel space frame will be installed in the next cross zone until the entire steel space frame structure is completed. After passing the final acceptance, the movable operation platform will be removed.

2.Construction process

Construction preparation→site leveling and compacting→laying track→set up a mobile operating platform (to do the tire frame of the first truss construction)→install the first section of steel space frame→ mobile operation platform→install the second section of steel space frame→repeat the above above -mentioned above→repeat the above above-mentioned above→repeat the above steps until the frame is installed→remove the mobile operation platform.

3.Key points of operation

Design operation platform structure according to relevant specifications, formulate construction plan and review and approve.

(1)Site leveling and tamping will clean up all facilities and sundry objects in the construction site to facilitate the laying of tracks and avoid slippage that hinders the operation platform. Take manual or mechanical leveling and tamping, control the flatness of the ground with level, the allowable deviation is ±50mm, and must be dense, the foundation soil compaction coefficient is greater than 0.94, to ensure the level of the track laying and prevent the track from sinking. The foundation can be constructed according to the elevation of the foundation soil of the designed indoor ground, and the ground layer can be directly constructed after the installation of the space frame. If the indoor floor is designed for concrete and in the case of time permitting, the ground construction can be completed according to the design.

(2)In order to reduce costs and facilitate procurement, the I-beam steel in the engineering design is generally selected as the track, which can still be used for the project after the slip is over, and the material is not wasted. The specifications and models often selected are I16 to I20. According to the plane design of the track, the track position line is released on the ground that has been leveled and tamped, and the marking pile is set. The lateral spacing of the track is twice the spacing of the vertical bar of the operating platform frame, which is generally 2.4 ~ 3.6m. The sleepers must be laid smoothly before the track is laid. The sleepers are laid perpendicular to the track, and the sleeper specifications are 150mm×200mm×800mm, and the spacing is 800 ~ 1200mm. When laying, the flatness of the sleeper surface must be strictly controlled, and the deviation of its flatness is not greater than ±10mm, and the sleeper must be stable. The track is laid on the top surface of the sleeper, and its position, spacing and surface level are corrected respectively. To ensure the level of the track, the thin wood pad is adjusted under the rail. The levelness of each track is controlled at 2/1000mm, and the track parallelism error is controlled within a range of 2mm. After the correction is accurate, the track is fixed firmly laterally with a clip under the track to control the track spacing, so that all the tracks are connected as a whole to prevent the track from moving laterally and dumping when slipping. The track clips are fixed under the track using quasi-48 ×3.5mm scaffolding rods plus double fasteners, and the spacing of the track clips is 4 to 6m. The longitudinal connection of the track must be fixed with splints and bolts, and the longitudinal connection points of the adjacent track must be staggered.

(3)Set up a movable operating platform The operating platform must be designed through theoretical calculation of the unit form. The movable operating platform is a fastener type scaffold, and the vertical rod is fixed on the shaped roller support, and the I-beam rail is under the roller support. In order to ensure the rigidity of the operating platform frame and easy sliding operation, the volume of each unit should be as small as possible. Generally, each unit is longitudinally between two axis spans (or three axis spans), and the transverse size is not greater than 25m. Movable operation platform design steps are: assume that the frame of the vertical bar spacing and horizontal bar step, and then calculate the load (the first pin of steel frame construction play the role of tire frame, constant load, construction load, wind load), and finally the overall stability of the operation platform framework (frame pole bearing capacity) check, in order to determine the feasibility of the operation platform. The frame adopts quasi-48 ×3.5mm scaffolding pipe, the horizontal spacing of the vertical pole is 1.5m, the vertical spacing is 1.0m, and the step distance is 1.8m. The fasteners are right-angle fasteners, butt fasteners and corner fasteners respectively. The top of the platform is covered with wooden boards of δ=50mm and fastened with iron wire. The platform is surrounded by a fence and hangs a vertical safety net. In order to facilitate the personnel up and down, in the frame of the steel pipe set up a ramp.

3.Quality Control

In order to ensure the smooth progress of the construction, the quality of the material is strictly required. After strict inspection and acceptance, the components can be used after passing. Steel pipes must have product quality qualification certificates, and the deduction must have production licenses, test reports of legal testing units, and product quality qualification certificates. The surface of the steel pipe should be straight and smooth, and there should be no cracks, scars, layers, dislocation, hard bending, burrs, indentation and tracting; the deviation of the outer diameter, wall thickness, end surface, etc. should meet the regulations.

The structure of the large span arch steel space frame can save the rotary materials, it is flexible and convenient during installation, the construction period is short and the cost is low. It can be applied to various exhibition halls, industrial factories and large warehouses with large bands, high vaults, and long vertical. The curved oversized steel space frame structure is increasingly valued in the domestic roof system. It is of great significance to study the design and construction process of super span steel space frame structure. The design of movable operation platform unit and track system, laying track and setting up operation platform of movable operation platform are very important to the success of construction. Inspection and acceptance should be strengthened in the construction process. In order to ensure that the construction quality meets the requirements, the material quality should also be strictly required. Only by ensuring the construction safety of the super span steel space frame structure can it be widely used in engineering.