Experimental study and finite element analysis of energy dissipating outriggers Page: 4
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Specimen RBO was replaced with high strength steel. The specimen with high strength
steel chords was named as Specimen HRBO (Figure 1(c-3)). Test results showed that
Specimen HRBO had similar energy dissipation capacity to Specimen RBO, but higher
yield and ultimate strengths.
Experimental observation and results of Specimen CO
Design of Specimen CO
Specimen CO was designed directly following the drawing of the prototype outrigger in
the background building project. The pseudo-static test was carried out in this study.
The geometry of scaled model is one-third scale of the prototype model. (MOHURD,
2015) The upper and lower chords and the inclined braces were all constructed with
welded shaped steel members. The chords and braces sections were of H 270 x 200 x
10 x 10 and H 200 x 200 x 10 x 10, respectively. Chords were embedded in two
foundation beams with double-fillet welded. They were as also connected to the loading
beam by double-fillet welds. Three steel gusset plates with a 10mm thickness were used
to connect the diagonal braces to the chords. Square-groove welds and strengthening
plates were used to connect the gusset plates to braces. The dimensions and construction
details of Specimen CO are shown in Figure 2.
All specimens were made of Q345 steel. The actual material properties were
obtained from coupon tests: the yield stress f of 388 MPa, the tensile strengthf, of 479
MPa, and the ultimate elongation 5d of 34%. The shear walls and frame columns in the
building were simplified as the end constraints of the outriggers.
Test setup
The test setup is shown in Figure 3. In order to accommodate the size of test specimen
and the loading system in the laboratory, the outrigger specimens were tested in a
vertical fashion. The bottom of the specimen was fixed to the strong floor of the
laboratory. Because the outrigger is constrained by the shear walls and the frame
columns in the building (Figure 1(b)), the deformation of the outrigger can be assumed
to experience a pure shear mode. Consequently, a pantograph was installed at the top of
the specimen to ensure the pure shear deformation of the outrigger (Figure 3(a)). A
cyclic load was horizontally applied to the specimen with two parallel actuators. The
outrigger in actual buildings is restrained by the surrounding slabs, shear walls and
frame columns, global out-of-plane buckling is unlikely to occur. Thus, the out-of-plane
displacement of the "L" shaped loading beam above the outrigger was restrained. In
addition, because the upper and lower chords of outriggers are restrained by the floor
slabs in actual buildings, the global buckling of these components will not occur either.
Hence, special restraints were installed in the test setup to prevent the global buckling
of both the upper and lower chords.
A pseudo-static loading procedure with displacement control was applied to the
specimen. The displacement at the top of the outrigger specimen was monitored. The
loading procedure was divided into 16 levels. For each level, the same displacement
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Yang, Qingshun; Lu, Xinzheng; Yu, Cheng & Gu, Donglian. Experimental study and finite element analysis of energy dissipating outriggers, article, November 11, 2016; Thousand Oaks, California. (https://digital.library.unt.edu/ark:/67531/metadc1065436/m1/4/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT College of Engineering.