In steel structure projects, portal frames first appeared during World War II, and then gradually developed slowly to become popular. In the construction of modern buildings, they are commonly used in the construction of large-span structural engineering, such as steel warehouses, agricultural buildings, steel storage facilities, entertainment and sports stadiums, steel structures, large supermarkets, etc., because these places need to meet very large space spans without intermediate column partitions.
Portal Frame
Portal frames were initially used due to their high structural efficiency, allowing large spaces to be constructed with minimal materials and low cost. Today, the majority of construction steel is used in the construction of portal frames.
A portal frame consists of a series of transverse frames supported longitudinally. The main steel structure is composed of columns and rafters, while the columns and rafters form the portal frame and supports. The frames at the ends can be portal frames or supporting structures for columns and rafters.
In simple terms, a portal frame is a structural framework that takes a very simple form, characterized by a beam (or rafter) supported by columns at both ends. However, because the connection between the beam and column is rigid, the bending moment in the beam is transferred to the column. This allows the beam to achieve greater distances while reducing cross-sectional dimensions. Typically, the connection between the beam and column is rigid, requiring the addition of haunches and brackets.
Steel Portal Frame
When spacing is required, portal frames can have single span or double span configurations, with rigid connections at the apex. Other forms include: tied portal frames, braced portal frames, and multi-span portal frames covering very large areas. Generally, when portal frames include spacing, the wider the span of the portal frame, the higher the apex.
If the overall height needs to be reduced, curved lines or folded forms can be used. This can also help reduce water runoff and water loads, which is important on large steel roofs. Curved or folded forms increase the slope of the roof toward the eaves.
Typically, steel structures can consist of a series of parallel portal frames, usually extending with frames spaced 6 to 8 meters apart. Good portal frame structures are typically covered with prefabricated composite metal panels with insulation materials. Masonry cladding can be placed at lower positions to ensure greater flexibility and safety.
Portal Frame
Although portal frame structures are seemingly simple structural forms, extra care must be taken, especially in joint design, to ensure that appropriate restraints are provided to prevent buckling. Bracing also needs to ensure the lateral stability of parallel frames, and more attention can usually be paid to the design of the end or intermediate sections between frames.
Simply because portal frames can be erected in a simple, fast structural manner and can achieve large spans, durability, low cost, and less material usage. They are typically lightweight and can be fabricated on-site, then bolted to the foundation. The portal frame itself can be exposed to the interior space, and if carefully designed, it can be very beautiful. After this detailed introduction, you can better understand the reasons for its popularity.
