The clearance between the core plate and the restraining part of the buckling-restrained brace using steel mortar planks (BRBSM) considerably affects the failure mode and hysteretic characteristics of the brace. A clearance adjustment construction is proposed for the BRBSM which can control the clearance through partially pasting clearance adjustment materials and polishing the mortar plank surface. First, the clearance adjustment construction workflow and quality control are demonstrated, and it is verified that the clearance can be assured by fabricating specimens. Further, the effects of the difference in clearance between the core plate and restraining part on the structural performance of the BRBSM in terms of failure behaviour, increase strength ratio, buckling mode and cumu lative plastic strain energy ratio are evaluated by conducting a cyclic axial loading test.

A structural soundness monitoring system for building steel structures is effective for a quick inspection just after large earthquakes. A damage‐controlled structure can be monitored effectively because damage is strictly concentrated in energy‐absorbed members, and that, in this case, the physical quantity suitable for monitoring is displacements of those energy absorbed members. Buckling‐restrained braces (also, the BRB using steel mortar planks, BRBSM), one of the energy‐absorption members, can be directly monitored by the monitoring sensor; it will be possible to quickly evaluate the extent of damage and make a prompt decision on the replacement. Focusing on functionality of a structural soundness monitoring system, a damage evaluation method of the BRB using steel mortar planks and its corresponding monitoring system are verified conducting by a cyclic loading test. It is demonstrated that the cumulative plastic strain energy can be estimated approximately using this system, and this system is adapted to a mid‐rise steel building.