At the stage of NPP civil structure design for determination of stress-strain state (SSS) at static and dynamic loading ABAQUS is widely used. Hereto the floor response spectra are determined for calculation of loadings on the equipment at special dynamic impacts (seismic, air shock wave, aircraft crash). In case if the obtained characteristics of SSS or spectral accelerations exceed maximum permissible values, designers take actions on strengthening the corresponding structural components.

Technology of optimization of the NPP civil structures has been applied, developed on the basis of ABAQUS and technologies of IOSO NM.

Use of such system approach to a choice of optimum parameters for calculation of response spectra has allowed twice as much to decrease the values of spectral accelerations at elevation of a transport crane in the portal of the NPP reactor compartment with VVER-1500 at seismic impact.

The model of the reactor compartment with a transport portal is given in Fig. 1. In Fig. 2 the detailed model of a portal with indication of the applied masses, simulating a transport crane with a cargo and a cart is given. The model is developed on the basis of the following structural finite elements:

• beam element of type B31, simulating reinforced-concrete columns and a crossbar, as well as metal beams;
• element of the lumped mass of type MASS, simulating a crane, a cart and cargo;
• element of plate (S4R type), simulating a foundation slab;
• elements of springs (SPRING2 type) and dampers (DASHPOT type), simulating soil (springs were also used to connect cargo and a crane).

As an external impact, a three-component accelerogram of SSE level (safe shutdown earthquake) with magnitude quake-range of 7 according to MSK-64 scale was applied to a portal foot, see Fig. 3.

Preliminary investigations showed inefficiency of the non-system design of portal structure. It has suggested using technology of optimization IOSO NM for the case in question. Dimension of optimization problem numbers 8 varying variables. To achieve the specified accuracy 0.01 it was required to make 60 calculations with use of the ABAQUS during optimization.

The response spectra in the locations of the crane and the cart are given in Fig.5 and 6. Fig. 5 and 6 show that as a result of application of optimization procedure an essential drop in the spectral accelerations can be observed.

Conclusions

For designing of NPP civil structures ABAQUS and technology of multiparameter optimization IOSO have been applied.
Use of such system approach for choice of optimum parameters with the purpose to make calculation of response spectra has allowed decreasing twice as much the spectral acceleration values at elevation of a transport crane in the portal of the reactor compartment of NPP with VVER-1500 at seismic impact.

Link to the full paper: http://www.iosotech.com/files/application/Paper-AUC2007.pdf