Cross-section
To provide for contraction and ex- pansion, twin frames are located at two intermediate points, resulting in a total of 28 frames.
Roof girder
The 55ft. cantilevered roof girder has a cross-section of 18in. x 50in. at the face of the supporting column, gradually tapering in both vertical and lateral directions to 10in. x 16in. at the tip. It is post-tensioned using the Freyssinet system with 11 cables, each consisting of 12 of 0.276in. diameter wires. Cables are successively terminat- ed towards the cantilevered end as they are no longer needed.
Reactions at the point of support are a vertical force and a bending moment induced by the roof loads. With such reactions a rigid connection was necessary and this was achieved by pressing the roof girder against the column by means of post-tensioning.
There are 28 main columns, each weighing 26 tons. Each is subjected to a large bending moment along the upper portion, decreasing uniformly to zero at its socketed leg. Column dimensions are therefore correspon- dingly proportioned with a section of 26in. x 56in. at the top, tapering to 26in. x 18in. at the bottom.
Columns were post-tensioned on site with eight Freyssinet cables which
MEZZANINE FL. LEV.
are anchored at the top and along the column faces near the bottom end. Post-tensioning was carried out by anchoring the tendons at the bottom and stressing from the top.
The bleacher girder, of which there are also 28 units each weighing 26 tons, is a one-piece reinforced concrete member integrated with a short column leg. The member is pin-connected to the column and at the footing socket. Moment reaction from the roof girder develops a horizontal reaction at the socket and loads on the bleacher girder are transmitted to the pin-connections as vertical reactions.
In the design of the basic frame of the grandstand, the footing sockets were planned to act as hinges. As such, the sockets were calculated to carry a horizontal thrust of the order of 62 kips, which in turn is transmitted to the footing tie beams. With the footing tie beam acting in structural unison with the column and the bleacher girder, the framework is thus basically a three-hinged frame con- figuration.
Unit production
The contractors for the concrete elements, Philippine Prestressed Con- crete Co., were faced with a very tight construction schedule, requiring the casting of 1,500 cu. metres of con- crete over a period of four months.
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Twelve types of structural elements were involved columns, bleacher girders, roof girders, mezzanine co- lumns, beams, tie beams, 6in. U-beams, bleacher seats, stair slabs, wall panels, railing panels and fascia panels — and production work was programmed so that sets of units were completed bay by bay to correspond with the de- livery schedule and the construction scheme of erecting the structure in three phases.
Production of roof girders and co- lumns included provisions for post- tensioning. After the concrete had at- tained the required strength, nine out of 11 cables were fully stressed in the plant to resist stresses resulting from handling, transporting and erection.
SCALE
+
2 FT.
Far East BUILDER, August 1969
GROUND PL. LEV.
冠
H
PRECAST BLEACHER
GRADER MIT
PIC BLEICHER
-R.C. MALA, ETAPU
Details at "A"
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