Project Overview:
Skeleton membrane structure is self-closed, stable framework system (usually steel truss system, grid structure, cable net structure or tensioning system) and membrane material together to form a structural stress system. After the skeleton-type membrane structure is made of a steel-structured roof frame, the structure of the membrane material is stretched above it. The lower support structure has high stability, because the roof shape is relatively simple, the openings are not easily constrained, and the economic benefits are high. It is widely applicable to any large and small-scale space.
Because the construction of the system is similar to the conventional structure (in addition to its own construction such as the cable net or the tension system), it is easier for the engineering community to understand and accept it. However, in order to allow the membrane to have a certain rigidity, the skeleton system provides a support system for the membrane. Generally have a certain degree of curvature, and should be set to impose pre-stressed mechanism.
Construction process:
1, the principle of the process:
(1) The installation of the membrane structure should be installed according to the design and assembly diagram of the membrane unit provided by the design to ensure that the membrane surface and the steel structure are accurately matched.
(2) The membrane material shall not be contaminated and damaged during the tensioning of the membrane, so as to ensure that the membrane surface is tensioned without wrinkles.
2, membrane surface construction process
Pre-construction preparations - Take the operator's operating platform - Set up a membrane-side shelving platform - Install the rope net - Membrane surface in place - Membrane surface deployment - Install anti-rope network - Fixed short edge, Temporary fixed edge - ―Installation across the membrane surface - Long-edge connection - Membrane surface tension - Stress test - Installation of waterproof membrane - Endo-film installation - Wrapping - Installation of protective dust cloth
3, preparatory work
(1) The support structure of the membrane structure prior to installation should have been completed and meet the requirements of the relevant structural construction and acceptance specifications. It is mainly to measure the geometry of the support structure and the connection node and compare it with the design value to make necessary corrections to the form-finding results; to cut the design according to the corrected shape and process the film surface; if the film surface is completed before the support structure is completed, production has begun. The deviation should be corrected through other schemes such as replacement of connectors and other specifications;
(2) Before the membrane is installed, the supporting framework shall have completed the construction work of anti-rust and fire-proof coating so as not to pollute the membrane surface. Before the construction of antirust paint and fireproof coating, the joints between the support skeleton and the film material must be polished smooth and rounded to ensure that there are no burrs, edges and corners on the joints, and the welding surface is convex.
(3) The position of the connection between the support structure and the membrane structure should be retested and recorded before installing the membrane structure. If the deviation between the re-measured value and the design value will affect the installation of the membrane structure or change the stress state of the membrane structure, the designer, the support structure and the membrane structure construction party and related parties shall jointly negotiate solutions.
(4) Before the installation of the membrane structure engineering, the drawings shall be reviewed and the structure and relevant technical requirements in the design drawings shall be mastered. The installation plan and technical assurance measures shall be prepared and installed in accordance with the requirements of the plan.
(5) After the material enters the site, it is necessary to check the product quality certificate or test report. It is forbidden to use unqualified materials in the project.
(6) The type, size, color, performance, and quantity of the materials, components, and parts of the membrane should be inspected prior to installation. Installation can only be performed if the requirements of the design specification are met.
(7) At the project site, the membrane material shall be placed on an erected auxiliary shelf and protective measures shall be taken when it is stacked outdoors. A temporary grid cable should be erected on the main structure before installation to support the unfolded membrane material.
4, construction methods
(1) Construction scaffolding erection
A. Shelving platform for membranes: A shelving platform shall be erected prior to construction of each transmembrane surface. The main materials for erecting the platform are the foot pipe fittings and the eleven-ply plate. Shelving platform erection position at the forefront of each membrane unit.
Shelving platform plane dimensions: The length shall be such that the length of a membrane is spread out laterally and the width is greater than the diameter of the membrane tube. The top of the platform is covered with eleven plywood. After the erection, the exposed scaffold pipes, fasteners and sharp parts are wrapped with cotton cloth. The eleven plywood panels used for shelving platforms should be clean, free from dirt, and ensure no sharp burrs, so as to avoid damage or contamination of the membrane surface.
B. The ascending scaffold shall be erected prior to installation of the membrane surface of the climber. When the ascending scaffold is erected, it shall be firmly connected with the main structure. During construction, adjustments can be made according to the actual situation on site.
C Construction Operating Platform
1) Operation Scaffolding platform for membrane surface installation at the periphery of arched erection of the structure. This platform is directly set up under the steel truss on the membrane surface and is tightly connected with the truss.
2) The operating platform when the membrane surface is deployed, this platform also serves as the operating platform when the membrane surface is connected with the membrane surface.
3) When the film is pulled and the film surface is connected, the operator needs to perform the construction under the pipe arch, install the hanging scaffolding full house scaffolding according to the characteristics of the project, and require the top surface of the rack to be flat and full of bamboo rafts or scaffolding. After all the platforms have been erected, safety barriers should be set up on the perimeter.
4) When erecting the scaffolding platform and erecting the safety net, any objects that come in contact with the main steel structure shall be covered with a cotton cloth to minimize damage to the paint on the surface of the structure.
5) After the erection of each scaffolding platform is completed, safety inspections shall be conducted by full-time security personnel, and only after qualified acceptance is available for use. The erection and acceptance of all scaffolding platforms shall be conducted in accordance with Technical Specifications for Operational Safety at High Altitudes of Building Construction and Safety Technical Specifications for Fastener-style Steel Pipe Scaffolding.
(2) Rope Net Installation: Before laying the membrane surface, a rope net must be installed as a support for the deployment of the membrane. The rope net material uses φ14 acrylic rope. When the rope net is installed, it spreads out through the scaffolding platform. A rope is pulled every 3m in the longitudinal direction, and both ends of the rope are tightly connected to the steel structure on the truss by a rope tensioner. After the installation of the rope net, a sufficient force is applied to the rope by the rope tight rope machine to avoid excessive contact with the steel structure during the pulling of the membrane surface, resulting in damage or contamination of the membrane surface. Tight rope exposed parts are wrapped with cotton cloth.
(3) Tension on the membrane surface:
1) After the membrane surface is installed, the membrane surface can be stretched. To prevent damage to permanent bolts, temporary tension bolts can be used to tension the membrane surface. First tighten the membrane surface with a wire rope tighter. After the adjustment bolt is loosened, tighten the bolt. Repeat in order. If the tension of the tight rope cannot be satisfied, adjust the temporary tension bolt directly with a wrench.
In general, the procedure for film stretching must be repetitive, with local tensioning of the area where the corners are folded until the stress on the film surface meets the design requirements. Replace temporary bolts with permanent bolts and tighten double nuts with spanners to meet design requirements.
2) The tension period for each membrane surface is approximately 6 days. On the first day, it was pulled up to 80% of the design requirement and on the second day it was pulled up to 90% of the design requirement. After the third day of continuous stretching of the film surface, due to the film surface will lose some of the stress during use, it is generally appropriate to stretch the film surface to the design requirements of about 110%. In the process of use, the film surface stress will gradually decrease and meet the design requirements.
3) Tensile stress control of the film surface is controlled numerically by tension stroke and tension. Experienced installation instructions through the slap film fabric, according to the sound produced by the film fabric, combined with the stretching process and tensile force values ​​to determine whether the tension reached the design requirements. Measure the warp and weft stress values ​​of the film surface with a dedicated film stress tester.
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