Comprehensive Evaluation of Metal Roof Health Based on Extension Theory and Entropy Weight Model

This paper proposes a comprehensive evaluation model with three layers including external layer, constituent layer and index layer. The metal roof is divided into slope region, spherical region, saddle region and etc. Each region is divided into common part, windward part and roof eaves according to geometric shape. Moreover, four evaluation indexes namely relative displacement, plastic deformation, fatigue damage, and historical failure rate are proposed to evaluate the state level of metal roof. The extension theory is applied to grade the health index, transforming qualitative evaluation into quantitative evaluation for clearer results. The index layer adopts entropy weight legal weight for more objectivity, while subjective weight is determined using the scale method for the external and constituent layers, taking expert experience and prior knowledge into account.