General Information

Figure 1 shows the construction side of a covered sports tribune.

Covered sports tribune.
Covered sports tribune made of steel trusses

The roof structure consists of frames, roof bracing, purlins, and metal roofing sheets. The braced cantilever arm is about 30 meters, and the frame spacing is about 10 meters.

Structural Concept

Figure 2 shows a schematic partial lateral view of the structure.

Lateral view.
Lateral view of a covered sports tribune

A frame is made of a reinforced concrete unit (hatched background) and a steel unit; the latter consists of a truss column (red background) and a braced cantilever truss with a back span (yellow background). The two units are connected at six points: point 1 is located at the cantilever base, points 2 to 5 along the truss column, and point 6 at the truss column base. Figure 3 shows the cantilever base connection.

Cantilever base connection (point 1).
Cantilever base to RC unit connection

The bottom node of the cantilever base is connected to the RC unit by a short circular hollow profile, a base plate with stiffeners, and anchor bolts. The support positions are marked by axes A, B, and C. The distance between A and B is shorter than the distance between B and C. Figure 4 shows the truss column base.

Truss column base.
Connection between the truss column and the RC unit

The truss column base is connected to the RC unit by two base plates with stiffeners and anchor bolts. The connections along the truss column (e.g. point 5) consist of short circular hollow profiles, base plates with stiffeners, and anchor bolts.

  • What are some possible reasons for connection 1 (support axis A)?
    Is the truss column required for efficiency reasons?
    What are some possible reasons for the connections along the truss column (points 2 to 5)?
  • Figure 5 shows an external braced cantilever truss.

    Braced cantilever truss.
    Braced cantilever truss

    The truss is tapered and connected to two suspenders (S1 and S2). The axes of the verticals and diagonals are marked by the yellow and yellow dashed lines, respectively. Figure 6 shows a truss sector.

    Braced cantilever truss.
    Enlarged view of the braced cantilever truss

    The distance between the verticals is not constant (a > b), and the purlins are placed away from the truss nodes. Transverse units, consisting of knee-braced cantilevers, are placed regularly along the external trusses. The upper chords and verticals are the support members of the transverse units.

  • Is the truss geometry the result of structural optimization?
    What are some possible reasons for placing transverse units instead of, for example, overhanging purlins?
    How do the transverse units affect the structural behavior of the external trusses?
  • Figure 7 shows the top end region of a brace unit.

    Brace unit (top end region).
    Top end region of a brace unit

    Suspenders S1 and S2 are connected to vertical V1 by a plate and bolts and nuts. Diagonals D1 and D2 have the same inclination angle α.

  • Is there a big difference between the tensions of diagonals D1 and D2?
  • Figure 8 shows a schematic layout of the roof bracing.

    Cantilever roof bracing layout

    The roof bracing consists of two longitudinal trusses, cross bracing, and corner bracing. There are 3 transverse and 15 longitudinal fields, giving a total of 45 fields. The cross bracing is placed on 24 fields (staircase-like arrangement). Figure 9 shows a roof sector viewed from below.

    Bottom view of the cantilever roof

    The corner bracing is placed on two elevation levels (upper and bottom chords), as shown in figure 10.

    Corner bracing.
    Corner bracing of the cantilever roof
  • Are the longitudinal trusses, the cross bracing placed on 24 fields, and the corner bracing required for structural reasons?
  • Alternative Variant

    A schematic partial lateral view of the applied variant and a tower crane-like variant are shown in figure 11.

    Applied and tower crane-like variants.
    Lateral views of the applied variant and a tower crane-like variants

    The tower crane-like variant is made of a RC unit and a steel unit; the former consists of a column (hatched background), while the latter consists of a truss-less steel structure (blue background).

  • What are the main pros and cons of the two variants?
    How does the wind uplift affect the structures?
    What is a possible roof bracing layout for the tower crane-like variant?