Ozaki et al. 2013
A damage-controlled system consists of energy dissipating devices, controlled rocking, and self-centering capabilities for advanced seismic performance. These systems minimize damage to both structural members and interior/exterior finished. The proposed system contains small-size hold-downs, with a built-in fuse function (HDFs), which are to be placed in the foundation of a multistory shear wall. Through analytical analysis the HDFs were shown to have excellent seismic resistance when compared to ordinary shear walls. This paper presents the experimental testing of full scale specimens and the resulting conclusions.
System Concept
The HDF is designed for multistory shear walls for cold-formed steel frames. The fuse element dissipates energy through a yielding steel plate. The butterfly pattern of the steel plate allows maximum energy dissipation capacity through simultaneous yielding over the full cross section of the fuse. Advantages of the steel fuse over the viscoelastic fuse is the hysteresis curve of steel is less dependent on strain velocity during earthquake motion and the yield strength and elastic stiffness of the fuse can easily be controlled by changings its geometry. The HDF assembly consists of a pair of fuse steel plates slot-welded to a U-shaped steel channel which is placed between the rocking frame and the foundation. The self-centering force is provided by the vertical gravity load.
Experimental Study, Results and Discussion
A 1-story single span full scale steel sheet shear wall specimen was subjected to shaking table test. Four type of connection details were examined: a specimen with HDFs and a yield strength of 5kN, one with HDFs and a yield strength of 10kN, one with elastic fasteners tightly connection column base to the foundation, and one without hold-downs allowing free column uplift. Input motions from the El Centro NS and the Japan Meteorological Agency Kobe-NS data records were simulated.
Shake table test showed that the HDFs provided good energy-dissipation capacity which reduced the base-shear and subdued the uplift deformation of the specimen. Residual deformations of around 0.5 mm were found when the HDFs were implemented. The free rocking condition specimens exhibited large uplift deformations and it is noted that this motions is very difficult to control when no overturning resistance is provided.
Reference
Ozaki, F., Kawai, Y., Kanno, R., and Hanya, K. (2013). ”Damage-Control Systems Using Replaceable Energy-Dissipating Steel Fuses for Cold-Formed Steel Structures: Seismic Behavior by Shake Table Tests.” Journal of Structural Engineering, 139, SPECIAL ISSUE: Cold-Formed Steel Structures, pp. 787–795.