Pages: 39-53

Abstract

In order to obtain a strong and integrated steel structure, it is necessary to connect the main parts, namely the beams and columns in an appropriate manner so as to be able to guarantee the intended productivity. The integrity and cohesion between the main parts can be made feasible via the connections implemented in two forms of welded and bolted but it is worth mentioning that the bolted connections are more widely applied because of the high assembly speed and low costs. The simplest loading type in bolted connections is the state where the connected sheet is subjected to direct tension. Force transferring method in bolted connections is in two forms of bearing and frictional and the present study tries to deal more with the bearing connections. After designing and constructing a small frame, sixteen connection sheets with a fixed thickness of 6 mm and a shield in the present study, clearance from the hole center was taken into consideration and each of the specimens was tested under strain in laboratory environment in such a manner that firstly each specimen was installed and the bolts were placed and tightened by making use of jacks, then the strain force was measured at certain times and recorded by the use of a data logger. The process continued from tension to failure. The result was that the maximum amounts of strength obtained in laboratory tests showed an error range of 15% to 62% in comparison to the theoretical calculation of maximum strength according to the Instruction Manual. Therefore, it can be concluded that the Instruction Manual has followed a very conservative trend so as to main a higher margin of assurance and it is not cost-effective because such an error percentage and the increase in the specimen strength rate acquired during laboratory tests in comparison to what is posited theoretically suffer a 25% reduction, for each of the specimens, in case that the coefficients are not applied in calculation relations. Comparing the specimens’ characteristics, it is concluded that with the increase in the specimens’ widths (W), both the maximum force obtained during the laboratory tests and the Td obtained through solving the relations mentioned in the Instruction Manual undergo an increase; in addition, with a comparison of the specifications regarding the specimens where the holes lie concentrically and with similar specimens where the holes do not exhibit clearance from the center, it was concluded that the hole’s clearance of the center brings about a reduction in the maximum force obtained in laboratory and the amount of Td obtained through solving the relations proposed in the Instruction Manual.