About Us
2022-08-24
1.Project Overview
The project steel structure auditorium covers an area of 20,000m². The steel auditorium project is a 6-story concrete frame structure. The auditorium is located on the right side of the office building of the Ministry of Foreign Affairs, which is one of the supporting projects of the project. The auditorium of the Ministry of Foreign Affairs is a circular building with a diameter of 52m, a cornice height of 14m, the highest point of the west facade is 17m, and a total construction area of 2000m2. The distance is 4m, the longitudinal spacing is 1m, and the inner bottom plate, rock wool, and 0.75mm thick profiled steel plate are laid on the steel purlin, and the roof surface area is 1500m2. The roof is divided into two parts, the inner ring and the outer ring, by the annular gutter, as shown in Figure 1. The width of the outer ring is 6m, the slope is 8%; the radius of the inner ring is 19.5m, the slope is 2%, and the width × height of the annular gutter is 1.2m × 0.8m. After the completion of the steel structure roof project of the auditorium of the Ministry of Foreign Affairs of the Congo (Brazzaville), many water leaks were found on the roof during the rainy season, which affected the progress of subsequent interior decoration projects. The construction unit used polyurethane waterproof material to stop leakage at all joints of the roof, but the effect was not good.
2 Reason analysis
•Design reasons
①Because Brazzaville, the capital of Congo (Brazzaville), has a tropical rainforest climate, the annual precipitation is 1000-1600mm, the instantaneous rainfall is very large, and the rainy season is abundant. The outer ring of the roof of the auditorium of the Ministry of Foreign Affairs has a slope of 8%, and the design is reasonable; the slope of the inner ring of the roof is only 2%, which is close to the drainage slope of a flat roof, and the design is unreasonable.
②The composite roof filled with rock wool double-layer metal profiled plate is circular, and the horizontal lap design is unreasonable, so it cannot achieve a waterproof effect in the case of heavy rain and water accumulation.
③ Rock wool is a soft base, and the roof steel plate is thin and rigid enough to withstand the construction load of the roof, resulting in deformation of the steel plate.
2) Due to the climate, the thermal deformation of the steel plate is too large, causing deformation at the interface and lap joint.
3) Construction reasons
① The gap between the metal plates is large on the horizontal lap joints of the roof panels, and the waterproof treatment is not done;
② The joints between the roof panels and the gutter, the ridge tiles, and the lap joints with the wall are not waterproof during construction Sealed.
3. Through technical consultation and on-site investigation, three metal roofing waterproof technologies are selected:
① Coiled material waterproofing technology;
②Spraying polyurea elastomer waterproofing technology (SPUA technology);
③Spraying polyurethane rigid foam waterproofing technology (PUR technology). Its characteristics, technical indicators, and applicability analysis and comparison are as follows:
1) The waterproofing membrane is easy to construct and has a fast construction speed; it has the elasticity of rubber, and the elongation is excellent, which can well adapt to the deformation and cracking of the base layer; it has self-healing properties, that is, when the membrane encounters puncture or hard object embedding, It will automatically bond with these objects; it has good acid, alkali, and chemical resistance. Soluble content (2 ~ 3mm) ≥ 2100g/m2; tensile strength ≥ 15.00MPa; elongation at break ≥ 250%; tear strength ≥ 250N/mm. Scope of application: sloping roof, roof garden, boarding and non-boarding roof, vaulted roof, metal structure roof, pool, and reservoir, etc.
2) The spraying polyurea elastomer waterproof SPUA technology has fast construction speed, fast curing, gelation within 10s, and walking strength within 1min; it is not sensitive to temperature and humidity, and construction is not affected by environmental conditions; all kinds of substrates (such as steel, concrete) has excellent adhesion; SPUA technology must use high temperature, high-pressure impact special mixing equipment. Tensile strength ≥ 16.0MPa; elongation at break ≥ 450%; tear strength ≥ 50N/mm; Low temperature bending ≤-40℃; Waterproof 0.4mpa, 2h waterproof; Bonding strength ≥2.5MPa. Scope of application: roof, pool, subway and tunnel waterproofing, etc.
3)Spray polyurethane rigid foam waterproof and thermal insulation material has stable dimensions, high strength, high elongation at break, good thermal insulation performance, waterproof performance and strong bonding performance; it can be sprayed on site, one-time molding, integrity well, it has the incomparable advantages of other thermal insulation materials, and at the same time becomes a powerful supplement to the waterproof layer; the PUR technology is easy to construct and the construction period is short. Obturator rate≥95%; water absorption rate≤1%; thermal conductivity≤0.022W∕(m·K); compressive strength≥300kPa; density≥55kg/m3; dimensional stability≤1%. It is suitable for gap waterproofing of exterior walls, non-transparent curtain walls, and roofs with complex shapes.
Based on the comparison of the technical indicators, the scope of application, and main characteristics of the above three metal roof waterproofing technologies, combined with the actual situation of the metal roof leaking in the auditorium of the Ministry of Foreign Affairs of the Congo (Brazzaville), it is considered that the best roof waterproofing technical solution is: PUR technology as the waterproof bottom layer, PUR has good adhesion to the metal roof, which can meet the strength requirements of the roof operation, and has good thermal insulation performance; SPUA technology is used as the surface layer, which makes up for the poor UV resistance of the polyurethane rigid foam. The surface color can meet the requirements of Party A. However, the equipment used for SPUA waterproof material has high cost, long round-trip transportation time, and high transportation cost; the special equipment for PUR waterproof material has low cost, and there is no round-trip transportation time and transportation cost. Through demonstration, it is finally determined that PUR technology is used as the waterproof bottom layer, and the surface is bonded with colored sand as the UV protection layer of the roof waterproof layer. This solution can meet the needs of this project in terms of technology, economy, and applicability.
4. Construction points
Process flow preparation for entering the site → reinforcement and cleaning of the grassroots → technical processing of nodes → acceptance of the grassroots → preparation of equipment and materials → spraying according to the process → inspection and correction → colored sand construction (ultraviolet protection) → quality inspection → engineering acceptance → data filing.
Scientific research and production practice have shown that submerged arc stud welding of embedded steel bars has effective protection for the molten pool and weld seam, with sufficient metallurgical reaction, large penetration depth, high weld strength, reliable joint quality, high production efficiency, and shortened construction period and cost reduction.
