Bolted structural anchor bolts are 1920mm in length and manufactured in two sections, with the lower portion embedded in reinforced concrete. When evaluating the stiffness of the bolt (c1), it is assumed that the section buried in concrete experiences minimal deformation, so only the deformation of the upper section is considered in calculations. The bolt’s performance grade is 1219 (GB3098.1-82), with a nominal yield strength R0.2 of 1080MPa and a guaranteed stress Sp of 970MPa (permissible stress). Since the actual working stress and installation stress are both below Sp, the anchor bolt meets the required strength criteria.
During production and maintenance, gap bolts are used to check for looseness by applying tension via tensioning cylinders. During maintenance, the residual preload force is denoted as Pvc, and the residual deformation is calculated as vLc = Pvc(1/C1 + 1/C2 + 1/C3). When the applied tensile force P equals Pvc, the bolt reaches a critical state: if P ≤ Pvc, the deformation remains zero; if P ≥ Pvc, the deformation increases sharply. This sudden change helps determine the residual preload. A small increase in pulling force results in a proportional increase in displacement. However, if the displacement rises significantly, it indicates that the actual residual preload has been reached, and at this point, the bolt should be replaced.
The theoretical preload required for the anchor bolt is 158.3kN, which is less than the original design value of 220kN, making the design sufficient for practical use. During installation, the tensioning cylinder is used to pre-tension the bolt through an extension method, with the applied force serving as the control parameter. This construction process based on displacement measurements is reasonable and effective.
However, the safety factor for the ground screw inspection is only 1.188, indicating that the strength margin is low. Therefore, during operation, it is essential to regularly check the pre-tightening force to prevent potential equipment failures. Regular maintenance and monitoring are crucial to ensuring long-term reliability and safety.
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