The dimensions of the system at the ground slab are 590 feet by 164 feet. Suspension cables and concrete ribs span 164 feet and are spaced every ten feet. On the street facade the piers are approximately 68 feet high; the tarmac facade piers are 50 feet
high. Piers are spaced forty feet apart.
The conncetion between the steel cable and the beam is an important one since it is the primary connection within the system. It consists of steel tension wires connected to a site cast concrete beam. The concrete beam is curved, resing in the plane of
the pillar capitals. It begins with the curvature of the suspended roof and terminates just short of being vertical.
The majority of the vertical loading in the airport is due to the self weight of the suspension roof. It consists of steel suspension cables spanning between the concrete piers which are given stability by concrete elements laid on top of the cables. th e lower ground level is simply slab on grade, with no supports running vertically to the roof. However, this slab is crucial in the structural system as it acts as a compression piece between the two concrete piers holding them apart from the inward acti ng forces at the base due to the nature of the system.
Standing in the center of the roof, your load would be transferred in tension to the ends of the cablis supported by the piers. Then it would transfer downward to the ground through the massive reinforced concrete objects, finally kept in equilibrium due to the slab between the piers keeping them from pulling inward.
This path of bringing the roof loads all the way to the outside and down and back towards the center may seem complicated in comparison to simply supporting the roof with vertical elements, but it allows for an extremely open and lengthy span, feeing up e normous amounts of space underneath. The strucutre of the roof, piers, and floor act as a complete system, allowing all the stuff in between to seemingly fload freely, not limited by the structure.
Lateral loads are taken care of in the transverse section by the contrasting cantilever of the concrete piers and the suspension cables acting in the other direction. This provides support in two directions with the dead load of the pillars causing a ben ding moment in one direction and the tension forces of the cables in the opposite direction.
In the other section longitudinally, the concrete piers are spaced apart by a horizontal concrete beam which runs along the tops of the piers spaced 12 meters apart. This beam not only helps resist lateral loads, but also provides a place for the roof to bear in between the piers. With them all anchored deep into the ground, along with a concrete roof structure providing added stability, the lateral loads are compensated for adequately in all four directions. Due to its low profile, and the afore menti oned forms of stability, wind loading is not significant in effect upon the stability of the structure.
The concrete piers are also tapered in all four directions, giving them each stability in all four directions from lateral loading. This individual stability contributes to the overall strength of the system. This is perhaps the primary resistance to la teral loads for the entire system. Each pier is independently supported in all four directions giving them each individual stability as in the case of a flagpole. Thus, they do not need much lateral bracing because of their structural independence. The foundations for these piers are also important because they are poured very deep into the ground for added lateral stability, and also are connected to the concrete slab which runs transversely between each pair of piers. This slab provides compression resisance for the whole system while also further stabilizing each individual support.
If you were to load the side of the structure laterally, visually, it would seem like the leaning piers could possibly tilt inward, especially since the cables are already acting in that direction. However, this is highly unlikely since the piers are of extremely high mass buried deep into the ground tapering to a much smaller cross-section towards the top. It would take an extreme force acting laterally to cause the massove foundations to rotate at the bottom.
Lateral loading in the longitudinal direction would be more likely to effect the building's stability, except that these two glass walls are structurally independent of the main system. The most that would happen would be the glass collapsing, but having no effect on the roof.
Scale is also a factor in the overall stability of the entire system. due to the massive size of the members, and the great spans created by them, it also would take sizeable loads to have a significant effect on the system, loads not present in the form of wind (unless a hurricane rolled through).
When looking at expansion and contraction of the concrete due to temperature change, this is compensated for by the nature of the suspension cables. When there is expansion or contraction, the caternary shape of the spanning cables will become flatter or
deeper to compensate. Also since steel and concrete have similar modulus's of elasticity, they tend to expand and contract at the same rate giving the system a continuity of deformation.
Scott Moreland and Rishi Ostrowski
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