The steel structure of portal frame light-weight building has the characteristics of simple force bearing, clear path of force transmission, fast component making, easy factory processing and short construction period, so it is widely used in industrial, commercial, cultural and entertainment public facilities and other industrial and civil buildings. Portal frame light-weight building steel structure originated in the United States, after nearly a hundred years of development, has become a relatively perfect design, production and construction standards of a structural system.
When the span of portal frame is greater than 40 m and less than 60 m, or the height is greater than 13 m and less than 18 m, the following measures should be taken:
(1) Longitudinal horizontal support and lateral horizontal support should be added to the roof to form a closed support system to enhance the overall stiffness of the house.
(2) When calculating the support design, it is advisable to consider that the wind force on the gable wall is supported by the end pillar support and the lateral horizontal support of the roof.
(3) Rigid tie bars must be used to ensure lateral stability of rigid frame columns and inclined beams, and it is not appropriate to rely on corner braces to ensure lateral stability.
(4) Purlins should not be used as tie rods at the same time. The tie rods must be set up separately with section steel.
(5) Round steel is not suitable for support, section steel is suitable for support.
(6) Skin has little effect and should not be considered.
(7) The limit value of lateral displacement of the top of rigid frame column should be controlled at h/100.
(8) The ratio of height to thickness of Inclined Beams and webs of columns should be controlled less than 120.
2. When there is a bridge crane in the portal frame and the tonnage of the A1-A5 medium and light crane is larger than 20T and less than 50T, the following measures should be taken:
(1) The technical regulations for light-weight buildings with portal frames permit the installation of sedan-chair cranes less than 20T. The large tonnage of cranes shall be carried out in accordance with the permissible values of column top displacement, deflection, component deformation and support seat displacement stipulated in the Code for Design of Steel Structures GB50017.
(2) The ratio of web height to thickness should be controlled below 80.
(3) Longitudinal horizontal support and lateral horizontal support should be installed on the roof to form a closed support system to enhance the overall stiffness of the building.
(4) Rigid tie bars must be used to ensure lateral stability of rigid frame columns and inclined beams.
(5) Round steel is not suitable for support, section steel is suitable for support.
(6) The swing column is not suitable for the middle column.
(7) Rigid joints should be adopted at the foot of the column and ladder-shaped columns should be adopted.
3. When portal frame is used in 8 degree earthquake area, the following measures should be taken:
(1) Under earthquake action, when the portal rigid frame components adopt variable cross-section, any cross-section should be limited to the elastic working stage.
(2) When the masonry enclosure wall between columns is attached and tied to the column, its total dead weight should be taken into account, but only 40% of its stiffness can be included in the calculation of seismic action along the longitudinal direction of the wall.
(3) The portal frame should be installed at the end of the house, and the gable column or gable should not be used to bear the load.
(4) Shape steel should be used for bracing, strength reduction should be considered for single angle steel bracing, single-sided eccentric connection should not be used for 8-degree seismic fortification, and when one member of cross bracing is interrupted, the cross-joint plate should be strengthened, its thickness should not be less than 10 mm, and its bearing capacity should not be less than 1.1 times the full plastic bearing capacity of the member.