Application of high strength plate bolts in friction grip joints

Abstract

High Tension Bolts (HTB) are known to exert a significant influence on the strength characteristics of connections and have a significant influence on the ductility and behaviour of the joint. Normally HTB failure occurs in the shape resultant high stress concentration neck and thread areas resulting in relatively low ductility characteristics. Creep and relaxation occur after HTB tightening causing shaft tension loss and further stress redistribution in the connected components. Past research has shown that waisting the HTB shaft diameter reduces stress concentrations, shaft tension loss and increases ductility. With the further modification of making the HTB head plate shape counter sunk, a plate HTB with an aesthetically pleasing flat surface less susceptible to rain corrosion results. In this research, tensile, relaxation and friction grip joint slip experiments were done on waisted shank, counter sunk plate head HTB to ascertain the ductility improvement, the resulting decrease in shaft tension loss and its magnitude, as well as their applicability in friction grip steel connections. Apart from significant shaft tension loss reduction, no detrimental effects are induced in the slip coefficient results when these HTBs are applied in friction grip joints. Within these experimental parameters, the closest to ideal HTB shape is proposed.


(Journal of Civil Engineering, JKUAT: 2002 7: 67-80)