Introduction to steel structure warehouse roof leakage

Steel structure is an increasingly widely used type of structure, due to its advantages of short construction period, large span, high strength, etc., it is more and more used in large-span plants, venues, public buildings and other buildings. The more common roof leakage and seepage problems in steel structure plants have seriously affected their utilization function.

In this paper, we try to start from the previous design stage, the construction stage, and the maintenance stage to explain the measures to prevent the occurrence of roof leakage in steel structure factory buildings. On the one hand, we should start from the source of design, and do a good job of steel structure roof design according to the structural characteristics of steel structure plant, on the one hand, we should strictly control the construction quality during the construction process, and design the node practice according to the good drawings. And also to do a good job of maintenance after the steel structure plant is put into use.

Design phase measures

1、Maximize the slope of the roof

The technical specification of steel structure of portal frame light house stipulates that the roof slope of portal frame light house should be 1/8~1/20, in the area with more rain water, it is preferable to take the larger value, and the roof slope of the southern area should not be less than 5%.

Design units in order to meet the construction unit to save money, reduce project investment requirements, usually take the smaller value. As the roof slope is small, resulting in slow roof drainage, rainwater can not be discharged in a timely manner, leaving hidden problems for the roof water.

Therefore, in terms of design, first of all, should be in strict accordance with the design specifications, not because of cost savings and arbitrarily reduce the design index, at the same time should be combined with the use of the actual situation of the region for the design of the site, the design should be taken to the larger rainfall reoccurrence period.

The design of roof purlin should be conservative, not blindly save steel and reduce the height of the bar. If the cross-section of roof purlin is designed too small and the spacing is too large, the deformation of the bar and compression plate under wind load will be too large. The height of the bar and the cross-section take a high value, which is good for preventing the roof from uneven downward deflection and avoiding the occurrence of water accumulation on the roof.

2、Maximize the use of external drainage systems

The roof rainwater drainage system of steel structure workshop can be divided into two kinds: external drainage system and internal drainage system.

The external drainage system is to use the roof gutter to discharge the rainwater directly through the outdoor standpipe to the outdoor rainwater pipe or drainage nullah.

The internal drainage system utilizes the indoor rainwater pipe to discharge the rainwater into the outdoor rainwater pipe.

Steel structure plant double slope roof and other forms of roof side span gutter that is against the outer wall of the gutter can be used to close the system of direct external drainage to eliminate rainwater, drainage effect is very good, as long as the calculation is reasonable, generally will not produce the phenomenon of water bubbling.

External drainage system is not limited by the capacity of the gutter and other conditions, drainage is smoother. Therefore, the external drainage system should be used as much as possible.

3、Maximize gutter depth

Compared with reinforced concrete roofs, the gutter depth of steel roofs is limited, and there is no continuous waterproofing structure between the gutter and the roof, so it is difficult to ensure that there is no water leakage when the gutter is waterlogged.

Occurs mostly in the gutter and roof panel overlap, commonly known as roof backwater, also occurs in the combination of rainwater risers and gutter.

Due to the external gutter's own characteristics, there is no such problem. The inner gutter is mostly made of 3mm~4mm thick steel plate bent, the depth of the gutter is usually between 160mm~250mm. Lap joints and bridging joints are two key areas. Bridging seam is mainly related to the construction quality, thin steel plate and steel gutter welding, control the quality of welded seams and do a good job at the welded seam waterproof rust construction.

Lap joint is not only a construction problem, and design is also closely related, where possible, should be appropriate to increase the depth of the gutter, so that the gutter rain does not exceed the lap joint.

4、Installation of roof overflow measures

The depth of the gutter is generally designed to be small, usually between 160mm and 250mm. In this way, in the rainstorm extreme weather conditions, a large amount of rainwater in a very short period of time into the gutter, rainstorm intensity exceeds the rainwater system design discharge capacity, resulting in “backwater” phenomenon, resulting in accidents.

And increase the depth of the gutter has certain limitations, so should consider setting the roof overflow measures, in the design of the building plans should be marked overflow port set method and location.

Overflow port is the most important content of the roof rainwater system, the specification provides that the building roof rainwater project should be set up overflow facilities, the total rainwater drainage capacity of ordinary buildings is not less than 10a reproduction period, the important building for 50a. Therefore, set up the overflow port in the two ends of the wall, for the longer gutter length of the gutter, it should also be considered in the daughter wall every 6m ~ 12m to set up an overflow port.

5、Minimize roof openings

Due to the need of piping installation and equipment installation, it is often necessary to make holes in the roof of a steel structure plant. The practice of opening holes in the roof destroys the overall structure of the roof of the plant, and the opening part of the roof is one of the larger leakage hazards of the roof of the steel structure plant.

Therefore, it is necessary to save for a rainy day in the design, and the openings should be waterproofed according to the node design. Should minimize the number of roof openings, such as exhaust pipe can be considered to replace the roof openings with wall openings.

When a large number of holes need to be opened due to the use and design requirements, consider setting up a concrete cast-in-place structure on the side of the steel plant roof independent unit, the need to access the roof of the pipeline equipment centralized arrangements in this unit, thus effectively avoiding the risk of leakage!

6、Appropriately increase the number and diameter of rainwater pipes

The number and diameter of rainwater pipes are one of the conditions that limit the capacity of the rainwater drainage system.

The number of rainwater pipe is small, the rainwater along the gutter flow distance, long time, resulting in “congestion”; rainwater pipe diameter design is too small, but also easy to cause rainwater discharge is not smooth, resulting in “backwater”.

Therefore, attention should be paid to appropriately increase the number of rainwater pipes and pipe diameter, at least one for each column moment. And we should pay attention to the reasonable selection of rainwater pipe material, such as the use of plastic pipe, poor strength, easy to be damaged, so we should try to avoid.

Measures during the construction phase

1、The human factor

Select an excellent and experienced construction team. The construction team and personnel qualifications should meet the requirements, and special operators such as welders should have relevant qualifications. The on-board operators should do a good job of technical briefing and training, and do a good job of checking each construction process, without letting go of any hidden trouble that may cause roof leakage problems. The installation of steel roofing system is a construction link with high technical content and high safety risk, which must be completed by high-quality construction personnel with rich construction experience.

2、Factors of materials

Steel structure houses are directly composed of construction materials, the important role of which is unquestionable.

The materials should be accepted on the spot, check the certificate of conformity and test report of the incoming materials, and the important materials should be sent for sample retesting. In the construction process of steel roofing, the quality of pressure steel plate, gutter plate, welding material, sealing material and even rivets should be strictly guaranteed in order to eliminate the leakage hidden danger. For some important building materials can be stipulated in the contract procurement brand, and put the material into the field, only the building materials with complete quality certification materials can be used in the project.

3、Construction method

The construction unit should establish and improve the process control system, the key nodes for the risk of leakage should be prepared for the operation guide, strengthen the construction process management, and seriously implement the process standards and operating procedures to improve the quality of installation.

Operating instructions should be based on the node design drawings, should include the production stage of each process, the quality of each sub-standard, technical requirements, as well as to ensure product quality and the development of specific measures, such as the key components of the processing methods, components of the installation process, process measures. To ensure that the node structure is reasonable, reliable, no leakage, good appearance. For easy to occur leakage risk of light board parts, roof openings parts, gable parts, flooding parts, gutter, bucket, high and low span connection parts and other key nodes, to do each process strict quality acceptance, the implementation of on-site construction quality responsibility system.

Use of maintenance phase measures

During the use of steel structure plant, the components are deformed and the sealing materials are aging due to sunshine, rain and temperature change. Therefore, after entering the use stage, it should also carry out necessary maintenance and avoid some improper practices.

1, waterproof glue, sealant aging, the use of the process should be necessary to check the maintenance.

2, the roof strip can not be increased at will on the load, people step on, easy to lead to the deformation of the roof panel.

3、Rainwater castor accumulates more dirt, there is water blocking. At the same time, we should pay attention to the gutter in the drainage pipe cap should use the ball type pipe cap, should not use the flat castor pipe cap, reduce the blockage phenomenon.

4, the roof leakage location for key inspection, especially before the annual flood season, strengthen the inspection and inspection, reduce the roof leakage on the production and life of the adverse impact.