Experimental Study On Shear Performance Of Direct Shear Anchor Bolts Group

Post-installed anchor technique of chemical anchor bolt is currently one of the most widely used, effective and economic means in reinforcement and reconstruction industry, the technology exists some problems to be solved in the calculation of engineering practice and design. On the on hand, such as in order to use the anchor anti pull ability, strengthen the anchorage effect between the anchor, colloid and concrete, The regulations of our country point out that anchor bolt rod must use full thread form, but anchor bolts with thread must reduce the effective cross-sectional area, resulting in the drop of the load carrying capacity, is it reasonable in the shear performance of anchor bolts? On the other hand, on anchor group case, because of technical defects and construction errors, most of the bolt rods, at the beginning, could not directly exposed to the edge of the anchor hole, with the development of load, the anchor bolt slippage against the connecting piece, and some have not yet start or just contact the connecting piece, others would have yield or failure, while the former shear suddenly increased, until the overall failure, failure load of this must be less than ideally all anchor coordination of force at that time, And this is the harm which due to the common anchor bolt shear, great difficulty are brought in our designs and applications. At home and abroad, more in-depth researches were made, with some suggestions and methods of innovation, but the effect is always unsatisfactory. To this end, we should make more research on such issues with in-depth innovation, put forward solutions.This article aim at the two problems, to introduce the fantastic function of direct–shear-bolt, developed by our team, on cooperative work in group anchor by experiment, as well as some other nice function because of that, compared with the ordinary anchor bolt shear condition, and to discuss the effect of bolt thread form on the shear behavior of anchor bolts. Through to research and to summarize the domestic and foreign related literatures, standards, and corresponding calculation method, concrete, anchor bolt, four aspects include connection and anchor adhesive are discussed. Finally, it selects the C40 as the concrete strength of substrate, and all anchor bolts are made by 40 Cr materials, 16 mm in diameter, buried depth 8D, the shear test on a total of 12 groups of single anchor and 10 group anchor, study their relationship between load and displacement, to make intra-group analysis and analysis between groups.On the basis of the above analysis, this paper summarizes the common anchors of various types of single and group anchor failure phenomenon and shear-displacement relationship and characteristics, and then compared, found half thread anchor in a single anchor case, the initial stiffness is about 1.8 times of the full thread form, and anchor group is about 2 times, and has higher ultimate load and maximum displacement. Ordinary bolt group has load-platform on shear process, the group anchor failure patterns are different, but direct shear anchor are on the opposite, whole load-displacement curve are stable, the damage forms overall are relatively uniform. Group direct shear anchor bolt has high stiffness in a wide range of, but small changes, while the ordinary group anchor stiffness fluctuations, the overall stiffness value is about 3 times more than the same common anchor, and has significantly higher shear bearing capacity. Whether it is from anchor failure modes or from the load-displacement curve, the direct shear bolt anchor group exhibit excellent synergistic force characteristics, which is not possessed by ordinary anchor bolt. Finally, it is suggested that the thread form of anchor bolt should be optimized by the whole thread, and the direct shear anchor bolt has great potential for the development of the project.This paper innovation point:(1) Innovative use of independent research and development of shear loading device, for the first time directly to research the direct shear anchor bolt group of shear stiffness, load displacement curve;(2) For the first time to contrast the shear results between the direct shear anchor bolts in the group and the ordinary group of anchor directly, the effect is significant. The direct shear bolt can effectively solve the problem of non-cooperative, and can greatly improve the stiffness;(3) Comparative analysis the shear results of anchor bolt in different thread form, providing development ideas, in the future, for the development of chemical post-installed technique.