Shimizu Construction Co., Ltd. has recently established a design and construction method for "post-installed anchors" that connect steel beams to reinforced concrete and steel-reinforced concrete structures (concrete structures) with short construction periods and low costs, with the cooperation of Hilti Japan Ltd. . The first strength specification certifying the reliability of this design and construction method has been obtained from the Minister of Land, Infrastructure, Transport and Tourism. With this strength specification, the adoption of "post-installed anchors" is expected to increase at sites where the company designs or provides design support and conducts construction, enabling differentiation in construction time and costs.

The "post-installed anchors" for which strength specifications were obtained this time target the reinforcing bars that are inserted and fixed into holes drilled in the concrete structure, with adhesive injected. After the partial revision of the Ministry of Land, Infrastructure, Transport and Tourism's announcement No. 1024 in March 2022, the applications for "post-installed anchors" that have obtained strength specifications have expanded, allowing their use not only for connecting with the existing concrete structures and their seismic reinforcement components, but also for joining members such as steel beams that bear constant loads.

In line with the partial revision of the announcement, the company promptly worked on obtaining strength specifications, creating over 500 test specimens while varying parameters such as the strength of the base concrete structure, effective embedment length, bar diameter, and the orientation of construction to verify the performance of the anchors. Additionally, through experiments, appropriate drilling methods and adhesive filling methods were established for the construction method. As a result, regarding the design and construction of "post-installed anchors" with the base concrete strength of 18-36 N/mm2, anchor reinforcing bars of D10-25 (the numbers indicate bar diameters), and effective embedment lengths of 7-20 times the bar diameter, the company was able to obtain strength specifications certifying reliability from the Minister of Land, Infrastructure, Transport and Tourism.

Steel beams that bear constant loads are used as reinforcement materials to prevent deflection occurring at the opening edge of concrete floors and as supporting materials for inspection walkways or steel staircases that protrude from the structures. Conventionally, when adding steel beams, the base concrete structure needs to be deeply chiseled to accommodate the anchor bolts that fix the beams, the anchor bolts are then set, and concrete is re-poured. This construction method is labor-intensive and raises concerns over damage to existing reinforcing bars from chiseling work, noise and dust, anchor misalignment due to concrete pouring, and surrounding contamination, so a method of joining using easily-installed "post-installed anchors" has been sought.

When comparing the conventional construction method that involved chiseling large amounts of concrete to set anchor bolts, with a scale of 100 for construction period, costs, and waste generation, using the strength-approved "post-installed anchors" changes these values to approximately 30, 15, and 1 respectively. Given the significant advantages of "post-installed anchors", the company plans to widely implement this method for both new builds and renovations.