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Report - PEER - University of California, Berkeley

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olts. The two BRBs installed in the third story are double-cored constructed usingcement mortar infilled in two rectangular tubes (Tsai et al. 2002) while the BRBs inthe first story are also double-cored but fabricated with all-metal detachable features(Tsai and Lin 2003). Each end <strong>of</strong> the double-cored BRB is connected to a gusset plateusing 6- and 10-24mmφ F10T bolts at the third and first floor, respectively. Nostiffener was installed at the free edges <strong>of</strong> any gusset before the testing.3@2.33m2@ 3.5m3@2.33m2.15 m3@4mTube400-9H400x200x8x13H450x200x9x14H456x201x10x17Pipe400-9BRB CoreArea=15cm 2BRB CoreArea=25cm 2BRB CoreArea=30cm 2Pipe400-9H400x200x8x13H450x200x9x14Tube400-9H456x201x10x173@7m(a)(b)Figure 1. (a) Plan and elevation <strong>of</strong> the full-scale CFT/BRB composite frame (b)Photo <strong>of</strong> the CFT/BRB test frame.3. DESIGN PROCEDURE FOR A CFT/BRB FRAMEThe design procedures (Tsai et al. 2004) adopted for the CFT/BRBF consist <strong>of</strong> thefollowing steps: (1) Select an initial desired displaced shape for the structure, (2)Determine the effective displacement by translating the actual MDOF structure to thesubstituted SDOF structure, (3) Estimate system ductility from the properties <strong>of</strong> BRBmembers, (4) Determine the effective period <strong>of</strong> the substituted SDOF structure froman inelastic design displacement spectrum, (5) Compute the effective mass, effectivestiffness, and design base shear, (6) Distribute the design base shear over the frameheight, (7) Design the members for the CFT/BRB frame. There are some key points inthese steps described above. First, the story drift θ yi corresponds to the brace yieldingcan be estimated as:θyi= 2 ⋅εcyγ ⋅sin 2φ(1)where ε cy is the yielding strain <strong>of</strong> the brace center cross section, γ is the ratiobetween a specific elastic axial strain <strong>of</strong> the brace center segment and thecorresponding elastic averaged strain <strong>of</strong> the entire brace (computed from the brace247

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