The spiral case of TGP hydroelectric power plant is a steel-plate lined reinforced concrete structure, with big diameter, high internal water pressure, and thinly pevipheral concrete. To investigate the feasibility of spiral case embedded directly, both the structure model experiment and nonl inear analysis have been carried out. To guide the model experiment and validate the rationality of nonlinear computing method, the three-di mensional nonlinear finite-element analysis is conducted to compute the concrete cracking in physical model. In the analysis, distributed cracking model is used, tension softe ning of concrete is considered and discretely reinforced bars are embedded in concrete elements. The computed results accord with model experimental data.