A grid of four hundred forty epoxy painted steel columns, tapering from eight feet in diameter at the base to just over three feet at the top, 150 feet high, are used to support the tension cable of the 210 fabric roofs. The semi-conical roofs are made f
rom 4.6 million square yards of Teflon coated fiberglass; they are self cleaning and expected to last thirty to fifty years. The base of the fabric is suspended 66 feet above the floor while 32 radial steel cables rise another 40 feet to attach to a tens
ion ring thirteen feet in diameter. These are the pieces which make the large roof units possible. Warm light is admitted through this translucent material, but because it is made for low transmission of heat, only seven percent of the available light i
s admitted. So, even though the exterior temperature may be well over one hundred twenty degrees Fahrenheight, the temperature under the tents seldom exceeds eighty degrees.
The Haj Terminal takes a downward verticl load by transferring the load as tension in the fiberglass fabric to verious cables and finally to the masts. Under a downward load, tension in the thirty-two radial cables of each tent module transmits the load to the central tension ring. From there, the primary cables transmit the load through pin connections to each of the four masts which surround the individual tent. Since these cables run at an angle, the force in them has both a vertical and a horizonta l component. At the mast, the vertical component of this tension is transmitted directly to the ground through the compression. The remaining horizontal component of the load is resisted by a moment developed at the foundation of the mast and by tension in the primary cable opposite from the one initially in tension. The remaining load is thus directed down to the next tension ring where it is taken up in part by some of the thirty-two secondary cables in the fabric membrane, and in part by the primary cables of that tent module. The portion of the tension taken by the primary cables is transmitted to the next mast just as in the first case. The secondary cables transfer their load down to the boundary or ridge cables where again the load is brought at the mast, at a much lower position. A portion of either load is transmitted to the earth by the compression of the mast and the rest is distributed to the other cables which connet to the mast at that point. This cycle of transferring loads to the ma sts continues until the boundary of the structure is reached. At the boundary of the module there is a double mast which resists any remaining horizontal components of tension through a moment developed deep within its concrete footing.
If the vertical load were upward rather than down, the ridge cables, or boundary cables, and the stability cables would be the members to transfer the tension load to the adjacent masts. Again, the vertical portion of the tension would be passed to the e arth through tension in the mast. The horizontal component of thetension would be passed on to the next cable in a continuous cycle toward the edge of the module. At the edge, the double masts resist the remaining horizontal tension by a moment at the f oundation.
Horizontal Loading
The fabric portion of the structure is the main element subject to lateral loading, although the masts will resist some loading directly. Essential stability of the fabric is provided by the double curvature of the semi-conical form. This allows every p
ortion of the membrane to exist in tension at all times. On the membrane, a horizontal load would be passed from the fabric to the ring of thirty-two secondary cables and then transfered to either the primary cables at the tension ring, or to the ridge c
ables. These in turn would transmit the load to the masts. In order to resist the transferred load the masts would develop a moment at the foundations. Internally the masts would have a bending stress as they transfer the horizontal loading down to the
earth. If the mast were in the middle of a module then the load would be resisted by the cable opposite the one applying the load in addition to the bending in the mast and the resistance of the foundation. Then, as in the vertical case, the load would
be transferred to the adjacent masts where a portion would be transferred to the ground and the rest redistributed to the next masts. This process would continue until the edge of the module was reached where the double mamsts take any remaining load on
their own, resisting through a developed moment and by bending. The masts themselves resist a horizontal load through a moment at the foundation and by imparting a tension in the connected cables as the mast tries to bend. The tension developed in the
cables is transferred across the module as before and taken in part by the other masts in the system.
Linda Babetski and Erich Karp
ARCH 461/561 Spring 1995
Do you have questions about adding a case? or a building to suggest??????? send a message to me....... chrisl@aaa.uoregon.edu