Quality issues stemming from design flaws have significantly reduced the investment efficiency of equipment, becoming a critical concern for its basic quality. This problem demands serious attention from designers. The concept of the "islanding effect" and its definition were introduced by the author to describe localized defects in concrete structures. Specifically, it refers to problems such as damaged bolt holes in equipment foundations or poor-quality concrete around these holes. For instance, concrete may be cracked or broken at the hole walls, or the poured concrete may lack sufficient strength. These defects, although minor in scale compared to the whole structure, resemble isolated islands in the sea. The term "island-shaped bolt hole defects" is increasingly being recognized within the engineering community.
The danger of such defects lies in their ability to weaken the connection between the equipment and the foundation, especially due to their island-like shape. These defects can render equipment inoperable, requiring costly reinforcement and leading to significant financial loss. Although the defects themselves are small, they can represent major issues for the equipment, making it essential to take them seriously. However, not all equipment with such defects will immediately show problems. The severity of the issue depends on the location and extent of the damage, which limits early detection. As a result, these defects might only become apparent during operation or may go unnoticed for a long time. Therefore, it's reasonable to use the term "island effect" to describe this phenomenon.
The islanding effect can be defined as follows: when reserved bolt holes are misplaced or missing, or when the bolt-injecting material lacks sufficient pull-out resistance due to improper drilling; when the filling material has no strength or insufficient strength, or shrinks, failing to form a reliable bond with the surrounding concrete; when voids or imperfections develop inside the bolt hole; when shear damage occurs to the hole walls; or when improper pouring methods cause misalignment of the bolts—these conditions weaken the connection between the equipment base and the equipment, compromising operational reliability. The hazard of the islanding effect can be either immediate or hidden. Once the anchor hole is in place, the static load of the equipment is redistributed internally, and the remaining bolts must bear the full power, which is highly disadvantageous.
Although the islanding effect is broad and includes issues like uneven concrete or crack development, this article focuses specifically on defects caused by improper design of bolt holes. To prevent such issues, the design of reserved bolt holes must align with the equipment’s specifications and match the processing holes of the equipment base. With the rapid advancement of modern technology, the functions and materials of various equipment are constantly improving, especially for imported, large, and specialized equipment. Each type of equipment often undergoes design modifications, frequently involving changes in dimensions and base structures. As a result, the information provided by manufacturers to users at the time of signing contracts may not always be up-to-date. A common solution is for manufacturers to provide the latest production-ready equipment data after the contract is signed, or to obtain approval following the completion of the equipment’s basic design. However, before installation, it is often discovered that the reserved bolt holes do not match the equipment base, and there are typically three main reasons for this discrepancy.
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