Flexible Structures

Flexible systems without stiff connection elements to their foundation, such as snow-supporting nets (Phillips et al., 2003), or structures on point bearings, are designed to adapt to non-uniform ground movements. The crucial foundation geometry is not fixed and can therefore be corrected as creep and thaw settlements occur over time. One example of this type of structure is the chairlift midway station in Grachen, Switzerland Two concrete supports are carried by a T-shaped girder, which has three point bearings (two upslope and one downslope), all of which can slide horizontally to enable the entire midway station to find its optimal equilibrium position (Fig. 21). The two upslope bearings are fixed when not being repositioned, whereas the downslope bearing can move freely, allowing the downslope foundation to move independently. If settlements or displacements occur beyond a previously specified threshold, the T-girder is displaced or uplifted hydraulically and steel plates can be inserted. The point bearings can therefore be relieved and repositioned (Phillips et al., 2007). A similar type of system, also using three point bearings, was adopted in 2005 for the new 'Pardorama' restaurant above Ischgl in the Austrian Alps. Flexible systems need to be monitored at regular intervals to allow for timely geometrical corrections to be made.

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