Balcony, amphitheater and grandstand structures
To ensure the necessary conditions of visibility and visual perception in sports buildings, facilities and entertainment enterprises are arranged balconies, amphitheaters and grandstands with a sequential rise in rows of seats for spectators.
Balconies with a large number of rows of seats are usually located at the ends of auditoriums against the scenes or screens, but can be arranged along the side walls of halls. By the terms of the visual perception of scenes and screens side balconies can not have a great depth, and their design decision is made in the form of cantilever beams or slabs embedded in the side walls of the hall or in the supporting frame. More complex are the designs of the end balconies with a significant number of rows of seats.
The height of the end balconies is limited to twice the height from the floor of the amphitheatre or parterre to the bottom of the balcony (under its barrier), i.e. about 6 m, in more rare cases 9 m. Balcony load-bearing structures are arranged in the form of frame-console, beam and beam-console systems.
Cantilever structures are used, as a rule, in case of balcony overhangs – 6 m, rarely – 9 m. Cantilevers in the form of beams or trusses are rigidly fixed at one end in the end wall or serve as a cantilever element of the frame frame walls of the hall. In cantilevered structures, the momentum increases towards the support, and so the height of the cantilever to the support may increase, which is usually consistent with the elevation profile of the rows of seats on the balcony.
If the rise of steps “comb” is made variable value, use reinforced concrete slabs, serving as the basis for the device of wooden steps with different values of elevation. To the bottom chord of the cantilever is attached suspended acoustic ceiling, which is also used to place lighting devices.
Balconies located above the foyer or other rooms adjacent to the hall and partially projecting into the hall are widely used.
Sloping transoms in the foyer are usually open and are an architectural element of the interior. In large halls, a tiered arrangement of balconies is used, the overall spatial construction of which meets the requirements of the rows of seats.
Supporting structures are reinforced concrete or steel beams-walls or trusses with parallel belts, resting on the side walls of the hall.
The height of wall-beams can be 1.5-3.5 m. The front wall-beam or truss is usually combined with the balcony barrier and lined with decorative materials. The wall girders are connected to each other by ties. Along the main load-bearing beams or trusses, secondary beams are laid in a transverse direction every 3-6 m, with a slope determined by calculating the elevation of the rows of seats on the balcony. Secondary beams serve as the basis for the staggered surface of the balcony. It is possible to place the first girder-wall or truss at some distance from the edge of the balcony. In this case, the secondary beams are made with cantilevers that form the edge of the balcony.
Amphitheater halls are widely used in entertainment buildings. Amphitheatres, like balconies, have an elevation profile of rows of seats, determined on the basis of calculation of visibility conditions, but located above the auxiliary premises of the basement and ground floor, where the placement of vertical supports (columns or walls) is possible.
The construction of amphitheaters is simpler than that of balconies. The supporting structures of amphitheaters are made of beams or frames.
When using precast reinforced concrete structures, the spacing of the columns is taken in accordance with the unified modular grid 6×6 or enlarged.
A feature of amphitheaters in some halls is the curvilinear outline of rows of seats in the plan with a relatively small radius of curvature. This causes the necessity of placing rows of columns under the amphitheater along radii, curves or broken lines inscribed in these curves. As you know, the elevation profile of amphitheater seat rows should be curved or broken with increasing distances between breaks as you move away from the object of observation. In accordance with this, the transom should also have a broken outline (see Fig. a) and elements of different sizes. Columns in this case it is advisable to place in the places of fractures, i.e. at different distances one from another, which violates the modular system.
The arrangement of “comb” in curved amphitheaters causes the need for different-sized slabs or prefabricated elements laid on the transoms. In the design solutions of amphitheaters it is also possible to use the horizontal arrangement of the ledgers perpendicular to the slope of the amphitheater (see Fig. b). In this case, if the columns are evenly arranged, the ledgers can be of the same type only in each row of columns. It is not very difficult to make a multi-span rib with different span sizes (in accordance with the calculated profile of the rows of seats elevation) from monolithic reinforced concrete. The comb in this case can be carried out from prefabricated L-shaped elements or from plates, as well as in the form of a monolithic reinforced concrete slab, on which wooden steps are arranged.