Application of modified fuzzy ahp method to analyze bolting sequence of structural joints

Abstract

Bolt-tightening procedures are investigated in this research. The random behavior of bolts in loosening torque is analyzed through a multiple criteria environment. The multiple criteria decision making (MCDM) method incorporates many factors which may affect the performance of jointed connections in loosening torque. The factorial design method is used to examine all the judging criteria with bolt-tightening procedures. The data collected includes the percentage of bolts loosened and the magnitude of torque loss from the preset level. From the analysis of all judging factors, some sources of variation may have conflicts with each other. Multiple criteria are considered in the whole analysis to determine a goal instead of judging from a single criteria in order to resolve the conflict. Butt splice connections are utilized for the bolt-tightening procedures. The effects of four different tightening patterns (row, column, off-center, random), 2 physical plate setups (rectangular, staggered), and 2 torque levels (80 ft-lb, 100 ft-lb) are studied. With each different combination, the number of bolts relaxed and the magnitude of torque loss are measured using the calibrated torque method. A series of pulling tests is carried out in order to find the maximum frictional force in each combination. The frictional force is directly related to the factors described above. This test criteria is combined with other criteria which may affect the performance of jointed connections. In the MCDM environment, different units of information are generated for the multi-level, multi-criteria goal. The modified fuzzy Analytic Hierarchy Process (AHP) method provides a useful analysis in dealing with vagueness in comparison within and between criteria. The analysis for bolt-tightening procedures with the modified fuzzy AHP method proves to be effective in choosing from many sources of tightening techniques. This model can also help examine structures which are composed of many similar jointed connections.