Dapeng Town Industrial Park, Tongshan District, Xuzhou City, Jiangsu Province, China
In the steel structure building system, purlin seems to be a small insignificant component, but it is of great significance to the stability and function realisation of the building. It exists throughout the whole life cycle of steel structure building from erection to use.
1.Load transfer and dispersion
The roof of a steel structure building is subject to a variety of loads, including the self-weight of roofing materials, wind load, snow load and possible maintenance loads. Purlin, as the key force transmitting member between the roof and the main structure, receives the roof load directly, and disperses these loads evenly to the main load-bearing structures such as steel beams and columns through reasonable structural arrangement. For example, in the northern region, the thick snow in winter will produce huge pressure on the roof, purlin can rely on its own strength and stiffness, the snow load is safely transferred to the main structure, to avoid the roof deformation or even collapse due to excessive local load.
2.Structural Stability Strengthening
Purlins are interconnected with the main steel structure to form a solid spatial force system, which greatly enhances the stability and stiffness of the building as a whole. Under horizontal load (such as strong wind and earthquake effect), purlin can effectively restrain the displacement of roof structure, prevent excessive deformation of roof, and then protect the integrity of the whole building structure. It is like the ‘ribs’ of the building, which supports the stability of the whole roof despite its slenderness, and ensures that the steel structure building can also stand under the harsh environment.
3.Roofing system building foundation
(1) Waterproof and heat preservation assistance
Purlin provides a flat and reliable support surface for laying functional materials such as waterproofing and heat preservation on the roof. When laying waterproofing membrane, the flat purlin surface can ensure that the membrane is closely fitted to avoid gaps and effectively prevent rainwater leakage; when installing thermal insulation materials, the reasonable spacing of purlins can ensure that the thermal insulation boards are firmly installed and filled tightly, thus improving the thermal insulation performance of the roof, reducing building energy consumption and enhancing the comfort of the indoor environment.
(2) Roof modelling
In some unique steel structure buildings, the purlin arrangement can also assist in shaping the roof modelling. By adjusting the length, pitch and slope of purlins, diversified roof shapes can be realised, such as arc, folding line, etc., to meet the architect’s demand for creative design of the building appearance, so that the steel structure building has both aesthetic value and practical function.
4.Construction convenience and economy
(1) Construction assistance
During the construction of steel structure building, purlin is relatively light and easy to install, which can effectively accelerate the construction progress. The construction personnel can first install the purlin in place, and then install the other components of the roof, forming an orderly construction process and improving the construction efficiency.
(2) Cost control
Reasonable selection of purlin materials and specifications can effectively reduce the construction cost under the premise of meeting the structural safety and functional requirements. Compared with increasing the cross-section size of the main structure to bear the roof load, it is more economical and reasonable to use purlin for load transfer and dispersion, which can ensure the quality of the building and achieve the optimal control of the cost at the same time.
Purlins play multiple key roles in steel structure buildings, from load transfer, structural stability to roof system construction and construction cost control, each aspect has a profound impact on the performance and quality of steel structure buildings. With the continuous progress of construction technology, the research and application of purlins will continue to deepen, injecting new vitality into the development of steel building industry.
