May_1967 — Page 20

Aerial view: gymnasium left foreground

tral suspended gallery and in the central suspended roof. In addition special floodlights and spot lights are provided for the stage and the arena. master controls being housed in the central control room's mimic panels.

Below the podium are air condi- tioned dressing rooms, committee rooms, VIP rooms. Royal retiring suite, press room and three restaur- ants. The ground floor also houses three plant rooms and the main air tunnel. Behind the stadium, and connected to it, is a large air condi- tioned gymnasium.

Roof Structure

Most interesting feature of the stadium is its roof structure which embodies three roofing systems. The outer 55 ft. of its 360 ft. span is a ring of radial folded plates of pre- cast concrete; the intermediate 75 ft. has a two-layer cable system; and the inner 100 ft. diameter space is closed with a system combining a single layer of cables and structural tiedown trusses.

The ring of folded plates, a shell of 4 in. thick reinforced concrete, rises from a 300 ft. diameter circle of supporting columns cast monoli- thically with the shell. The shell roof cantilevers inward and outward from these columns.

ring

The inner edge of the ring of fold- ed plates, forming a circle, 250 ft. in diameter, supports a 16 in. sq. com- pression ring of steel and reinforced concrete. The compression anchors and supports the cable roof system and stabilizes the folded plate system against lateral forces. Torsion- al resistance of the compression ring prevents the frame from overturning.

In the cable roof portion, cables run from the 250 ft. diameter com- pression ring to a 100 ft. diameter ten- sion ring. A 15 ft. high circular truss surmounts the tension ring. The top chord of the truss, in turn, becomes

the compression ring of the smaller cable system that completes the clos- ing in of the arena roof.

By employing three systems, the roof's natural frequency is raised and the problem of damping flutter by making the roof span discontinuous is eased. The double catenary of the cable roof portion reduces the roof's sag, resulting in a flatter and higher ceiling. The ring truss acts also as a clerestory angled to pick up rays re- flected by the aluminum roof.

There are 48 pairs of the % in. suspension cables in the outer cable system. The stabilizing cables, which also number 48 pairs, are 1⁄2 in. dia- meter. Each kind has a different fre-

quency and damps vibration in the other.

Suspension cables, supporting the roof's weight, are anchored to the compression ring: the stabilizing cables, which have a 1 to 25 down- ward slope and carry no vertical load, anchor to the columns. The two sets of strands are tied together with 3 16 in. cables, set at 5 ft. centres, so that they form cable trusses.

Corrugated 20 gauge aluminum sheets form a roof deck over the cables. The suspension cables form peaks and the stabilizing cables create valleys, resulting in a shape like that of a radial folded-plate roof.

The tension ring is made up of

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Main entrance foyer

Far East Architect & Builder May, 1967

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