Abstract
Preloaded bolted connections are one of the most used approaches for anchoring steel structures and equipment. Preload is induced by a mechanical tightening of the nut with the required torque. In the case of anchor bolts embedded in a concrete base, the prescribed tightening procedure has to be followed for safe and reliable operation. The present paper addresses the problem of anchoring a new casting pedestal using the original anchor bolts. The aim was to verify the original anchoring system’s reliable and safe operation, taking into account the current condition of the bolts. The analysed anchoring bolts are subjected to cyclic (disappearing) stress during the rotation of the casting pedestal. If the interplays between the anchor bolt and the concrete foundation were damaged, production would shut down, resulting in high economic losses. For this reason, the authors used a modified nut with a lightened first thread when investigating the actual state of the anchoring and setting the required preload. The shape and dimensions of the nut were determined based on the results of numerical modelling. The experimental measurements consisted of two phases. In the first phase, the values of axial forces in the anchor bolts at the required preload were set using the designed dynamometers. The second phase was focused on the operational measurements. The methodology of measuring the axial forces and the interpretation of the results obtained, including a comprehensive view of the anchoring safety, provides relevant evidence of the functionality and effectiveness of the proposed solution. Based on the results of the operational measurement and the prescribed handling of the casting pedestal, the lifespan of the anchoring was determined to be 3650 days under the loading cycles to date.
Highlights
The anchoring between a metallic component and a concrete foundation is an essential point in the stability and durability of the structure
Nuts with notches were designed and impossible tofabricated perform the testnumerical tighteningmodelling of nuts exceeding allowable values of axial subsequently using based on the the finite element method to forces in the bolts, as they could not be released from the concrete foundation
The operational measurements of the time changes of the axial forcesAs were carried out withthe an operational empty ladlemeasurements weight of 70,300 a full ladleof weight of mentioned above, of kg theand time changes the axial forces were carried out with an empty ladle weight of 70,300 kg and a full ladle weight of
Summary
The anchoring between a metallic component and a concrete foundation is an essential point in the stability and durability of the structure. Studied the shear behaviour of the fully grounded bolts through experimental testing, during which the direct shear tests were carried out on three groups of specimens with different bolting angles or grout strengths, measuring shear loads, shear displacements, and strains in bolts They observed that the bolts failed near the concrete foundation. The anchor bolts are embedded in concrete, part of the technological chain For this reason, it is not possible to make laboratory measurements or to test “other” bolts. It is not possible to make laboratory measurements or to test “other” bolts This issue was solved with a modified nut with a groove to relieve the first thread, which is the most stressed and is the primary cause of failure of the bolted joint. The modification of the nut with the groove is primarily associated with an increase in the dimensions of the nut, i.e., it increased its height and outer dimensions
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