of structural components in the powerhouse occurred as a result of failure of the No. 2 generating set (GS-2) at the Sayano-Shushenskaya HPP (Fig. 1). Figure 2 shows the cross section of the powerhouse.The monolithic reinforced-concrete covers of GS-2, GS-7, and GS-9 at elevation 327.0 m, and the columns supporting the monolithic covers of these sets and the walls of the annular shafts of the generators at elevations from 319.8 to 327.0 m were destroyed as a result of the failure (Fig. 3). The enclosing MARKhI structures of the machine room above GS-2, GS-3, and GS-4 were totally destroyed. Many of the cantilevered slabs along the walls of the lower pool had been completely demolished or deflected, and a large number of the second stage structures had failed; and, stairways were damaged by rubble-laden water flows.Coworkers of the JSC VNIIG im. B. E. Vedeneeva participated in a study conducted by special commissions to evaluate the situation at the HPP as early as several days after the failure, while a diagnostic-monitoring group from the VNIIG in conjunction with representatives of the SayanoShushenskaya HPP, the publicly owned joint-stock company Lengidroproekt, and the Siberian Scientific-Research Institute of Hydraulic Engineering has been conducting a techni-

The paper provides the results of the investigation into transformer-oiled reinforced concrete structures that has been carried out alongside with using an elastic recoil method, ultrasonic testing, and a breaking-off and chipping method. To ensure correct results, testing was applied to the adjacent oiled and dry areas of each structure. The results of all testing methods were found close to each other with regard to all data information obtained in the oiled and dry areas, i.e. no significant tendency in changing the concrete strength was noted when concrete was oiled with transformer oil. The investigation showed that traditional belief in the negative effect of oiling the concrete on physical and mechanical properties of the material is not true, at least for the transformer oil. One can assume that the oil effect on the concrete depends on the type of oil, composition (type of cement and fillers, water-to-cement content, etc) and cement structure (number of pores and microcracks), structure application environment condition, and the structure age prior to oiling, etc. Respectively, it requires a more detailed study into oiled structures in each specified case.

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