Experimental Study on Buckling-Restrained Braces Using Steel Mortar Planks

Abstract

The authors have proposed the buckling-restrained braces (BRBs) using steel mortar planks, providing stable hysteretic behavior under the high axial-strain conditions. The compressive strength of BRBs generally tends to be higher than the tensile strength.The authors understood that it was because of friction force between the surface of core plate and the restraining part, and that the magnitude of friction force was related to the buckling mode number resulting in the increase of contact points. A set of prediction formulas for the buckling mode number has been proposed in the authors� previous study. In this paper, the validity of the proposed formulas for the buckling mode number of plastic region of core plate is examined by the test results of strain gauge measurement on the core plate from the cyclically axial-loading tests. Furthermore, the relationship between the strength ratio of the compressive to tensile strength and the buckling mode number is evaluated. As a result, 1) the buckling mode number is approximately proportional to the slenderness ratio of the plastic region of core plate, and 2) the proposed formulas, considering the location of fixed point between the core plate and restraining part, correspond quite well to the test results in the relationship between the compression-to-tension strength ratio and the axial strain amplitude.

Proposal and application of structural soundness monitoring system for the buckling‐restrained brace using steel mortar planks

“…According to previous studies [14][15][16][17][18][19], the failure modes of the BRBSM are classified as damage such as member buckling, local buckling, tensile fracture and local deformation, as indicated in Fig. 2.…”

“…Authors have been conducting research on BRBs (also, the BRB using steel mortar planks; BRBSM), which are widely used as earthquake-resistant members and seismic-response control members [14][15][16][17][18][19][20][21]. They are prepared by placing the clearance adjustment material on two steel mortar planks (grooved steel filled with mortar) that serve as the restraining part, as indicated in Fig.…”

Higher‐mode buckling and friction in long and large‐scale buckling‐restrained braces

“…Given that full‐length testing is often impractical for long BRBs, analytical means to estimate these length effects are essential. Previous equations [ 7,11–13 ] to estimate β have utilized a single average wavelength and assumed that the friction force ( F ) accumulated along the effective friction length L F is directly additive to the BRB compressive force (i.e., | P C | = β P P T + F ). Conversely, iterative numerical procedures, [ 14 ] finite element analyses, [ 7,14–16 ] and tests that directly monitored the local core demands [ 11,12,17 ] have observed significant variations in the wavelength, axial strain, and compressive force along the yield length.…”

“…Previous equations [ 7,11–13 ] to estimate β have utilized a single average wavelength and assumed that the friction force ( F ) accumulated along the effective friction length L F is directly additive to the BRB compressive force (i.e., | P C | = β P P T + F ). Conversely, iterative numerical procedures, [ 14 ] finite element analyses, [ 7,14–16 ] and tests that directly monitored the local core demands [ 11,12,17 ] have observed significant variations in the wavelength, axial strain, and compressive force along the yield length. This suggests a more complex relationship between the friction and compressive forces and implies that the local axial strain demands may significantly deviate from ± .…”

“…This suggests a more complex relationship between the friction and compressive forces and implies that the local axial strain demands may significantly deviate from ± . Furthermore, although these effects are likely sensitive to the shape of the stress–strain curve, previous investigations have been limited to a narrow range of mild steel grades similar to SN400B [ 11–13,15 ] and SN490B. [ 7,14,16,17 ] However, spatial structures and tall buildings regularly employ BRBs with significantly lower and higher steel grades to optimize the yield drift and/or core area.…”