Due to design-related quality issues, the investment efficiency of the equipment is significantly reduced, making it a critical concern for the fundamental quality of the system. This problem should be given serious attention by designers. The concept of the "islanding effect" and its definition were introduced by the author to describe localized defects in concrete structures. Specifically, this refers to problems such as damaged concrete around bolt holes, insufficient or absent strength in poured concrete, and similar issues. These defects, though small in scale relative to the entire structure, resemble isolated islands in the sea. As a result, the term "island-shaped bolt hole defects" has gradually gained recognition within the engineering community. The risk associated with these defects lies in their ability to weaken the connection between the equipment and its foundation, leading to operational failures that require costly reinforcement. Although these defects may appear minor, they can represent major issues for the equipment, and thus their potential hazards must not be overlooked. However, not all equipment with island-shaped bolt hole defects will immediately experience performance problems, which limits the understanding of their long-term risks. This is because the location and severity of the defect can vary, meaning the defect might only become apparent during operation or remain undetected for a long time. Therefore, it is reasonable to apply the concept of the islanding effect to better understand and address these issues.
The islanding effect can be defined as follows: when certain conditions occur—such as misplaced or missing reserved bolt holes, inadequate pull-out resistance of the bolt-injecting body due to improper drilling, or the absence or insufficient strength of the filling material—these issues can lead to unreliable connections between the equipment base and the foundation. Other contributing factors include shrinkage of the filling material, which prevents it from forming a solid bond with the surrounding concrete; voids or imperfections within the hole; shear damage to the bolt hole walls; and improper pouring methods that cause misalignment of the bolts. All of these conditions compromise the structural integrity and reliability of the equipment. The hazards posed by the islanding effect can be either immediate or latent. Once the anchor holes are in place, the static load of the equipment is redistributed through internal forces, placing excessive stress on the remaining bolts, which is highly detrimental. The concept of the islanding effect is broad and also includes issues like uneven concrete materials and crack propagation, which degrade the overall quality of the structure. However, this article specifically focuses on the islanding effect caused by improper design of the bolt holes.
Proper design of reserved bolt holes requires obtaining accurate equipment information and cross-checking it with the dimensions of the equipment base. With the rapid advancement of modern technology, the functions and materials of various types of equipment have improved significantly, especially in the case of imported, large, or specialized equipment. Each type of equipment often undergoes design improvements, which may involve changes in its outline or base dimensions. As a result, the information provided by the manufacturer at the time of signing a contract may not reflect the latest version of the equipment. Typically, manufacturers provide updated equipment details after the contract is signed or seek approval following the completion of the basic design. Nevertheless, before the installation of the equipment foundation, it was discovered that the reserved bolt holes did not match the equipment base. There are three main reasons for this discrepancy.
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