Comparison and Selection of Bridge Type Schemes Based on AHP and Grey Correlation TOPSIS

Determination of the optimal bridge scheme is crucial in the preliminary design stage of bridge construction, and the scientific decision results directly affect the construction and implementation of the whole project. At present, the determination of bridge schemes in mountainous areas is mainly based on empirical judgment, and few theoretical methods can be adopted. Therefore, a comprehensive evaluation model was built for mountainous bridge type scheme by the basic AHP theory, grey relational analysis, and TOPSIS. The model comprehensively considered the various factors affecting the selection of bridge type from the aspects of economy, technology, and society, and 12 evaluation indexes were selected to build a comprehensive evaluation system for the bridge type scheme in mountainous areas. Weight vector of valuation indexes of bridge type was calculated by AHP to reduce the influence of human subjective factors. Then, a weighted grey correlation coefficient decision matrix was constructed by fuzzy mathematics theory and grey correlation analysis, and the relative closeness coefficient between the alternative schemes and the Grey correlation ideal solution was calculated by TOPSIS. Finally, the optimal bridge type scheme was determined based on the relative closeness coefficient. The evaluation model was used to judge three alternative bridge type schemes (A₁-A₃) of a highway in the mountainous area of Pu'an County, Guizhou Province. The relative closeness coefficients of continuous PC T beam bridge (A₁), PC continuous rigid frame bridge (A₂), and PC dwarf-tower cable-stayed bridge (A₃) were respectively 0.597 7, 0.315 6, and 0.400 3, indicating the first scheme is the best optimized bridge type. Thus, the first bridge scheme was applied to actual bridge construction and achieved good economic and social values. The results show that the evaluation model provides a feasible theoretical method for the decision-making of mountain bridge type.