Experimental testing of joints for seismic design of lightweight structures. Part 1. Screwed joints in straps

Abstract

Connections in x -braced shear walls play a crucial role in the seismic performance of lightweight structures: they should be strong enough to allow energy dissipation via plastification of the diagonal straps. An extensive experimental research on tensile screwed joints between straps is reported here. Two dominant failure modes are identified: (1) tilting and net section failure (T+NSF) and (2) tilting, bearing and pull out (T+B+PO). The analysis in terms of strength and ductility shows that T+NSF joints are suitable for seismic design, because the straps yield before the connections fail. T+B+PO joints, on the contrary, are not suited because the connection fails before the straps can yield. The influence of various design parameters (strap thickness, number and diameter of screws, steel grade) in the failure mode is studied, and design criteria to induce a T+NSF response are given.

Experimental testing of joints for seismic design of lightweight structures. Part 3: Gussets, corner joints, x-braced frames

“…The results of the strap-strap tests carried out in the present investigation are reported in two previous papers [7,8]. These results allowed for the determination of a set of basic recommendations for joint design.…”

“…From the seismic point of view, the distinction between these two groups is very important because, as it was demonstrated in [7], only T+NSF joints are suitable for dissipative x-bracings of lightweight structures. The main problem with the T+B+PO type of joints is that their failure occurs before the yielding of the diagonal straps and, as a consequence, no dissipation can be developed (see in Fig.…”

“…In view of the results obtained, it was recommended in [7] to design x-braced shear walls with screw connections failing in the NSF mode.…”

“…9). Both modes are ductile, their ductility ratios range between medium to high values (see [8]), but the ductility of the joints that undergo the net-section failure (T+B+NSF) is higher than the ductility of the joints that fail bearing (T+B+TS). Therefore, regarding the ductility of the joint itself, the NSF type of joint is again preferred.…”

Earthquake Resistance of Modular Building Units Using Load-Bearing Steel Stud Panels

“…여기서,    = 스트랩브레이스의 지압파괴강도,   = 스 트랩브레이스의 두께,  = 강판 두께의 영향을 고려하는 강 도보정계수 [11], [12] ,    = 스트랩브레이스의 극한강도,  …”