New Development of High Strength Bolt Connections in Steel Structures

As an effective structural connection between steel components, high strength bolt connection has been widely used in the construction filed nowadays. With the development of high strength bolt connection technology, new objects have shown up including new types of bolt, new technology, new equipment and so on. Investigation and conclusion of these new technologies have been conducted, which can provide the technical reference to the revision of the related specificitions as well as providing more choices for design and construction. The new types of high strength bolt consist of 12.9 and upper grade high strength bolt, blind bolt and ring groove rivet. Nowadays, there are research work and engineering practices of these new bolts in China, but engineering applications develop poor due to the absence of related specificitions. Investigation of new high strength bolt technology is mainly about bolt pretension indicator and bolt corrosion protection. Referring to their characteristics, comparison of these two technologies have been conducted among the research work worldwide. The new pretension indicator can eliminate the human error caused by using the traditional one, and therefore it can improve the accuracy of constructing bolt pretension. High strength bolt corrosion protection can effectively retard bolt corrosion, and therefore reduce the maintenance.
There are differences between domestic and foreign specificitions and comparison among these specificitions can provide references to the revision of current ones. Comparisons of calculation of bolt prying force and bolt pretension force as well as bearing capacity of friction-type and bearing-type high strength bolt connection among different specificitions have been conducted and show that: 1) Calculation results of bolt frying force from Chinese specificitions are more conservative. 2) The required bolt-pretension force in Chinese code is 15% smaller than that of American code and 10% smaller than that of European code. 3) The shear resistance formulas among different specificitions are consistent but the definition of contact surface and mean slip coefficient are different. 4) Bearing strength of bearing-type high strength bolt connection calculated from American code is the highest one and the higher one is from European code while the poorest one is from Chinese code. For tension strength and shear resistance, European code provides the highest values and European code shows the higher values while Chinese code provides with the poorest values. In general, Chinese code is conservative than foreign codes.