The support system is a secondary part of the steel structure system, but it is also an essential part. In portal rigid frame steel structure system has important functions, mainly displays in: ensure the stability of the overall structure and the individual component level role and delivered to the foundation and the auxiliary installation, etc., to layout the structure of the complex, the stiffness of the structural adjustment of support system has proved to be uniform structure, reasonable and improve its integrity.
Setting the principle of support system
In the gantry frame steel structure, the support system can be divided into roof horizontal support, column support and other auxiliary support systems.
① Clear, reasonable and simple transmission of longitudinal load, as far as possible to shorten the way of force transmission;
② To ensure the stability of the structural system outside the plane and provide lateral support points for the overall stability of the structure and components;
③ Convenient installation of structure;
④ To meet the necessary strength, stiffness requirements, with a reliable connection.
There are still some regulations and requirements for different types of bracing in gantry frame steel structure building.
a. The roof is supported horizontally
Roof horizontal support and inter-column support are a whole, together to maintain the stability of the structure, and the longitudinal horizontal load is transmitted to the foundation through the roof horizontal support and inter-column support.
In order to ensure that the transmission path of longitudinal load on the structural gable is short and quick, the horizontal support of the roof should be set in the opening at both ends of the temperature section of the building, in order to directly transfer the load on the gable. If the first room can not be set, it can be set in the second room, but it must be noted that the corresponding horizontal load transfer bar in the first room should be designed as a pressure bar. When the building or temperature expansion section is long, one or more horizontal supports should be added, and the spacing should not be greater than 60m. When the structure is simple, symmetrical and the height of each span is consistent, the roof horizontal support is relatively simple, that is, under the condition of meeting the temperature section length, it can only be set in the end opening.
In the building, when the column has different column distance, or when the building has high and low span change, longitudinal horizontal support should be set to improve the integrity of the structure, adjust the distribution of structural anti-lateral stiffness, in order to reduce the difference of lateral horizontal displacement of each rigid frame column, so that the structure of uniform and reasonable force. When the layout of the building is irregular, such as local convex and concave, pumping column and so on, in order to improve the overall lateral force resistance of the structure, it is necessary to set up longitudinal and transverse closed continuous horizontal support system in the above areas.
When setting the support system, the pressure bar must be set at the roof ridge and the top of the column and pay attention to the structure of the node to ensure the transfer of horizontal force.
b. Support between columns
The inter-column support is generally arranged in the middle of the column. For this reason, the horizontal tie bar at the top of the column should be designed as a rigid tie bar to transfer the load borne by the horizontal support of the roof to the inter-column support. If the building is longer, inter-column support can be added. The support between the two columns is respectively placed in the longitudinal 1/3 place. When the support between the columns cannot be set in the ideal position required by the structural design due to the requirements of the building, it can also deviate from the central column setting. The support between the columns can be designed in the form of a cross, can also be designed in the form of figure eight, a gate, or even a rigid frame.
In the same building, it is better to use one type of inter-column braces, and it is not suitable to mix several types of inter-column braces. If because of the functional requirements such as open doors, windows or other factors, rigid frame support or truss support can be used. When the support system must be mixed, the stiffness should be made as consistent as possible. If the stiffness consistency requirements cannot be met, the longitudinal horizontal force borne by each support should be specifically analyzed to ensure the stability and safety of the structure. At the same time, attention should also be paid to the symmetry of the support setting.
c. Angle support
Angle support is a special feature of light steel structure building with solid belly gantry frame. The angle support is arranged between the lower flange of the frame inclined beam and the purlin or between the inner flange of the frame side column and the wall beam. It supports the stability of the inclined beam and the side column of the rigid frame. Angle support is an auxiliary member that does not independently form a system. The function of the angle support of rigid frame is to prevent the lateral instability of the lower wing of the inclined beam from being compressed.