STRUCTURAL INTEGRITY ANALYSIS OF LARGE MATERIAL AIR LOCK FRAME - A FLEXIBILITY BASED DESIGN APPROACH

摘要

Airlocks in Nuclear Power Plants involve large steel door frames integrally connected to the civil structure. Generally these frames are designed with stiff steel plates, with large cross sectional dimensions, especially for sealing requirements. Assuring integrity of the frame with civil structure is a critical functional requirement as the doors form the boundary between two different zones of radio-activity. In this paper, structural integrity of the door frame-civil structure connection is verified under different load combinations, which include thermal and seismic loads (OBE and SSE). Anchor forces are evaluated by imposing deformations of civil structure under these loads, on to the frame. An iterative and evolutionary design procedure for the frame & connection design has been presented based on the concept "Design to be as flexible as possible, while being adequately rigid to cater functional requirements". Different elements of the frame, which add to unwanted stiffness in the system resulting in high anchorage forces, have been identified and removed iteratively so as to arrive at the final configuration of the frame and supporting arrangement. Certain other measures like coupled analysis of frame and building to evaluate realistic deformations of the frame have also been adopted to redvice the anchorage forces.