Special Bearings for Johannesburg Freeway


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Title: Special Bearings for Johannesburg Freeway

Author(s): M. L. Roseblade

Publication: Special Publication

Volume: 70


Appears on pages(s): 135-144

Keywords: bearing capacity; bearings; elevated roadways; field tests; hiqhways; jacking; maintenance; manufacturing; mines (excavations); moving loads; performance; structuraf analysis; structural design; viaducts.

Date: 1/1/1981

Sections of the Johannesburg East West elevated freeway are constructed over areas extensively undermined from early gold rush days. Due to this and the inherent instability of the strata, long sections of the structures were designed to accommodate substantial and sudden vertical and horizontal ground movement. A major design consideration was that compensating adjustments and realignments of the structures would be made without halting traffic flow. Various unusual bearing configurations were employed and special bearings catering for vertical and horizontal adjustment were designed. Special "High Friction" bearings were required as well as Temporarily Fixed and Uplift types incorporating unusual sliding surface materials. Initial horizontal jacking of one structure was carried out to confirm friction data. All structures are continually monitored for movements from remote points to warn of dangerous earth movements and need for remedial action.