Investigation About Principle On Friction Type Bolted Connection With Enlarged Holes

As the bolted connection is widely used in large steel structure system,higher requirements for the design and construction are put forward.In practical engineering,the safety of the structure is affected by the enlarged holes.The studies on bolted connection with enlarged holes focus on bearing type bolted connection and energy dissipation capacity of connection with enlarged holes.Basis on summarizing the existing norms and research results at here and abroad,this paper have made a calculated and analysis about friction type bolted in shear connection and the carrying capacity of connection enlarged holes.In this paper,an Ansys model is established to simulate the friction type bolted connection and compared with the experimental data to verified the accuracy of model.Then,use the model to find the influence of thickness,strength of steel,friction coefficient about shear connection.The results show except friction coefficient and bolts pretension,the thickness of the connecting plate has a great influence on the bearing capacity.For the M30 bolt,the plate thickness of the middle plate should be greater than 20 mm,and the plate thickness of the splice plate should be greater than 12 mm,while the steel strength has little effect on the bearing capacity of the plate.Explore the shear capacity when use concentric circle to reaming the bolt holes.The calculation results show that the larger the reaming area is,the smaller the bearing capacity is and the more the pre-tightening force is relaxed.When the area ratio of hole expansion is less than 1.4,standard holes are used for the splice plate,and enlarged holes are used for the middle plate.The bearing capacity is reduced to a minimum and the preload force is loosened.In this case,the reduction factor is taken as 0.9.Only when the splicing plate is broached,the reduction is the largest when all sizing holes are used.The reduction factor of these two working conditions can be taken as 0.85.At the same time,the influence of the distance between the new and old bolt hole and the position relationship between the hole and the original hole on the bearing capacity is also studied.Studies have shown that the larger the distance between holes,the smaller the bearing capacity.When the distance between the center of the hole for reaming is less than 0.2 times the diameter of the bolt,the reduction factor of the bearing capacity of the bolt can be uniformly taken as 0.9.When the distance between the centers of the bolts is greater than this value,the stress appears on the plate.Concentration leads to redistribution of stress and affects the safety of the structural system and is therefore not recommended.At the same time,this article defines the evaluation criteria of the stress distribution uniformity coefficient,and evaluates the influence of the positional relationship between the old and new bolt holes on the bearing capacity.The calculation results show that the bearing capacity is reduced greatly when the opening position is parallel to the load direction,when the opening position is perpendicular to the load direction,the bearing capacity is reduced less,and the rest is between the two.The study enlarges the existingstudies on bolted connection at home and abroad,giving reference to engineers,which helps the use of bolted connection with enlarged holes.