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Design Fit Method

The Design Fit Method is an efficient seismic retrofit technique that still allows design and construction to be carried out in a conventional way. Seismic retrofit work using steel structural braces takes a lot of time and effort, and anchor installation generates noise and dust. By significantly reducing this installation work, Design Fit shortens the construction period, improves the construction environment, and reduces costs. In addition, by adding a reinforced concrete frame to the structure of the building being retrofitted and by installing braces in the added frame, the work can be done completely externally. This allows the occupants to continue using the building while the retrofit is being carried out (retrofit with occupants in place).

Simple Retrofit

No special techniques are required for a Design Fit retrofit; all that is needed is the capability to perform a conventional seismic retrofit. The construction procedure is generally the same as that for a conventional retrofit. This simple method involves putting in post-installed anchors, erecting steel structural braces, and filling with mortar. (In the case of an exterior retrofit, an extension frame needs to be added using onsite RC casting before installing the steel structural braces.)


(1) Anchor bar installation Confirmation of thread-cutting position by temporary setting of anchor bars Fixing and curing of anchor bars Important point: Relationship between anchor and steel rebar positions		(2) Steel structural brace installation Adjustment of center, entry/exit, and vertical installation positions Important point: Relationship between anchor and steel frame stiffener positions Ensuring the lap length between the anchors and the web Ensuring an average Fill-grip clearance of 80 mm


(3) Installation of the front anchor bars Ensuring the specified lengths by connecting the front anchor bars with coupling nuts		(4) Filling with mortar Carefully applying the specified mortar between the existing structure and steel structural braces, ensuring that there are no gaps. In principle, the tamping should be done from the bottom to the top in one go.

Joint Details

(1) Anchor bar installation (staggered arrangement)

(2) Installation of coupling nuts

(3) Installation of joint anchors (completion of anchor bar installation)

(4) Completion of mortar filling