Space frame engineering design

The use of space frame structure in engineering, because of its ability to large span, low steel consumption, high bearing capacity, according to the requirements of building juice to achieve different shapes and other characteristics.

The space frame structure has been used for several decades in our country, its design level and construction has become quite mature. In the design and construction of spatial space frame structure, the national technical and economic policy should be implemented to achieve advanced technology, safe application, economic reasonability and quality assurance.

When designing the spatial space frame structure, we should start from the actual situation of the project, rationally choose the structure scheme, space frame arrangement and construction measures, and comprehensively consider the processing and on-site construction and installation methods, so as to achieve good technical and economic results.

Suspension crane is not suitable for single mesh shell structure. The space frame frame and double reticle shell structure directly bear the load of suspension crane with working level A3 or above. When the cycle number of stress change is equal to or greater than 105 times, the fatigue calculation should be carried out, and the allowable stress range and structure should be determined by special tests.

When the spatial space frame structure is designed and constructed according to the regulations, it should not only conform to the relevant provisions of the regulations, but also conform to the provisions of the current mandatory standards of the family.

1.Basic design provisions of space frame

1) The plane shape is rectangular surrounding support space frame, when the side length ratio (long side/short side) is not more than 15, it is appropriate to choose quadrangle cone space frame, oblique quadrangle cone space frame, checker board quadrangle cone space frame, quadrangle cone space frame, two oblique quadrangle cone space frame, two check intersection quadrangle cone space frame. When the side length ratio is greater than 1.5, it is appropriate to choose the two – way cross-put space frame, put quadrangle cone space frame or evacuated quadrangle cone space frame. When the plane is narrow and long, one-way folding line space frame can be used.

2) The plane shape is rectangular, and the space frame with three sides supporting and one opening can be selected according to one. The opening edge must have sufficient rigidity, and the methods such as increasing the height of the space frame, increasing the number of space frame layers or forming a complete side truss can be adopted.

3) The plane shape is rectangular, multi-point support space frame, according to the specific situation can choose the quad-cone space frame, quad-cone space frame, two orthogonal quad-cone space frame

4) The plane shape is round, regular hexagon and close to regular hexagon and the surrounding support of the space frame, according to the specific situation can choose three way space frame, triangular cone space frame or evacuated triangular cone space frame. For small and medium span, honeycomb triangular cone space frame can also be selected.

5) The space frame height and space frame size of the space frame should be determined according to the span size, column network size, space frame form, roofing materials, structural requirements and building functions, etc. The height ratio of the space frame should be 1/10-1/18. The number of space frames in the short span of the space frame should not be less than 5. When determining the mesh size, the Angle between adjacent members should not be less than 30 degrees.

6) The space frame can be supported by upper or lower chord, such as when the lower chord support is used, vertical or inclined side truss should be formed at the side of the support. The space frame with multi-point support should be equipped with column caps. The cap should be set under the lower chord plane (Figure 1a) or above the upper chord plane (Figure 1b).

7) For the floor of a multi-storey building with a span of no more than 40m and the roof with a span of no more than 60m, the combined space frame structure with reinforced concrete plate instead of winding can be adopted. The combination space frame should choose the quadrangle cone space frame, quadrangle cone space frame, two orthogonal quadrangle cone space frame, oblique quadrangle cone space frame and honeycomb triangular cone space frame.

8) space frame roof drainage slope can be used under and outside

A、add a small column on the upper chord node to find the slope (when the small column is higher, we must pay attention to the stability of the small column itself);

B、space frame height change;

C、Ramp of space frame structure

2.Basic provisions for the design of reticle shell structure

1) The vector span ratio of spherical mesh shell should not be less than 1/7

The thickness of the double layer spherical mesh shell can be 1/30~1/60 of the span (plane diameter)

The span (plane diameter) of a single spherical mesh shell should not be greater than 80m

2) The height of the cylindrical mesh shell supported on four sides or along the longitudinal edge can be 1/2~15 of the span B. The ratio of the wave width B to the span L of the cylindrical mesh shell supported at both ends should be less than 1.0. The vector height of the complete body should be 1/3~16 of the wave width

The thickness of the double cylindrical shell can be 1/20-1/50 of the width

The span L of the single-layer cylindrical mesh shell supported at both ends should not be greater than 40m. The span B of the single-layer cylindrical mesh shell supported along the longitudinal edge should not be greater than 30m.

3) The ratio of the diagonal length of the bottom of hyperbolic parabolic mesh shell should not be greater than 2; The vector height of a single hyperbolic parabolic shell can span 1/2~14(the span is the distance between the diagonal support points), and the vector height of each direction of four combined double parabolic shells can span 14~1/8

The thickness of double-layer hyperbolic ground cover can be 1/20~1/50 of the short-direction span

The span of single-layer hyperbolic parabolic reticulated shell should not be more than 60m.

4) The side length ratio of the bottom side of the elliptical parabolic mesh shell should not be greater than 1.5, and the vector height of each direction of the shell can be 1/6~1/9 of the short span

The thickness of the elliptical parabolic blood shell can be 1/20~1/50 of the short span.

The span of single-layer elliptical parabolic reticulated shell should not be more than 50 m.

5) The supporting structure of the reticle shell should not only ensure the reliable transmission of vertical reaction force, but also meet the necessary marginal constraints of different reticle shell structural forms.

The supporting point of the spherical mesh shell should ensure the constraint condition of resisting horizontal displacement

Cylindrical mesh shell can be supported in the following ways: both ends support, along the two longitudinal side support, along the four sides support. The end support shall have sufficient in-plane stiffness. The support points supported along the two longitudinal edges shall ensure the constraints of resistance to lateral horizontal displacement.

The hyperbolic parabolic mesh shell should transfer the load to the support or the substructure through the edge members. The edge members should have sufficient stiffness and be calculated together as part of the overall mesh shell.

The elliptic parabolic mesh shell and the four combined hyperbolic parabolic mesh shells should be supported along the periphery through the edge members. The edge member shall have sufficient stiffness.