Dangerous foundation defect
During survey of industrial building structures a dangerous defect of slab foundation under the columns has been detected, described as follows: first, the main reinforcement was laid not at the bottom tension region of the basement, but at the top compressed zone, that is, instead of the reinforced concrete foundation the foundation was only concrete; second, the foundation was too shallow for heaving soils, third, the real strength of the foundation was not sufficient to absorb not only existing, but future loads after workshop modernization. The paper describes the activities to eliminate this defect. Detailed «manual» calculation of the concrete slab was performed on 2D circuit and with software package on 3D circuit with modeling of the underlying foundation layer in the form of combination of elastic half-space models and model proposed by Fuss and Winkler. Analysis of survey results allowed suggesting a technical solution to strengthen the foundations structures, which later was developed into a working project. The basis for strengthening was the buildup of foundation with concrete slab reinforced with rigid steel rods, installed in pre-loaded state, which allowed to disperse the load on four extra points. The project also contemplates the technology of reinforcement pre-loading with «bolt-nut» pair through controlled nut tightening with wrench.