抄録
Hot dip galvanized bridges have become popular for prevening corrosion due to exposure and reducing maintenance costs during the life time of steel bridges. The reliability of galvanizd friction type joints with high strength bolts may differ from that of ordinary joints of uncoated members. This difference is caused primarily by the iron-zinc alloy and pure zinc layers of the surface of the member. The present paper reports the results of investigation on the behavior of hot dip galvanized friction type joints with high strength bolts under short-duration static load and the secular change of bolt tension. The results are then applied to evaluate the reliability of galvanized joints having bolt tension lower than the specified value as well as of slip-load occurrence.
The main conclusions derived from this study can be summarized as follows: After a month, the loss in bolt tension was 10-13% for the hot dip galvanized surface as compared to the initial bolt tension. The secular change of bolt tension and the slip coefficient calculated by using the residual bolt tension could be expressed by use of the regression method based upon the exponential creep law. The probability of slip occurence decreased with increasing duration after the bolt clamping of he joint. The maximum value of the probability calculated was rather small, ranging from 4.8×10-7 to 6.6×10-7.
