Uplift Load-Displacement Behavior of Grillage Foundations

Full-scale field tests were conducted on steel grillage foundations for lattice transmission line towers that had been in place since 1929, 1947, and 1958. A total of eight tests were conducted at the three tower locations, and all were in granular soils. Both the site conditions and the load tests were documented extensively, allowing for a thorough evaluation of the load-displacement behavior. Data analyses showed that the load-displacement behavior could be normalized effectively and that a simple equation could be used to express this behavior. Incorporation of data from nineteen other tests in the literature demonstrated the overall generality of the developed relationship, which applies to grillage foundations in granular soils loaded in axial uplift.