Report - PEER - University of California, Berkeley

γ s =1.15. Values less than 1.0 mean that Eq.(7) may be unsafe. If µ θ is determined asthe ratio of the member ultimate drift not to the experimental yield drift, but to thevalue M y L s /3(0.5EI) corresponding to the effective elastic stiffness of 0.5EI assumedin Eurocode 8, the median ratio becomes 2.08 for γ c =1, γ s =1, or 2.26 for γ c =1.5,γ s =1.15 in the 626 column tests, and 2.69 for γ c =1, γ s =1 or 3.13 for γ c =1.5, γ s =1.15 inthe 49 wall tests (not far from the “theoretical” values of 2.25 and 2.65 quoted above).(5)Table 1. Compliance criteria for assessment or retrofitting of concrete membersMembers Limited Damage SignificantNear Collapse (NC)(LD) Damage (SD) Linear analysis Non-linear analysisDuctile(2)θ E ≤0.75θ u,m-σ(2)θ E ≤θ u,m-σprimary(1)θ E ≤θ yDuctile(3)θ E ≤0.75θ u,m(3)θ E ≤θ u,msecondaryBrittle Checked only if NC is not checked. V (4) E,CD ≤V (5) Rd,EC2 ,primary Then criteria of NC apply with V Rd,EC8 /1.15 (6) V E,max ≤V Rd,EC2 ,V Rd,EC8 /1.15 (6)Brittle V E,max from analysis, or with V E,CD V (4) E,CD ≤V (7) Rm,EC2 , V E,max ≤V (7) Rm,EC2 ,secondary for linear analysis in SD Limit State(8)V Rm,EC8(8)V Rm,EC8(1) θ E : chord-rotation demand from the analysis; θ y : chord-rotation at yielding, Eqs.(8)–(11).(2) θ u,m-σ : mean-minus-stand. deviation chord-rotation supply, equal to θ u,m /1.5 if θ u,m is computedvia Eq. (12), or to θ y +θ pl u,m/1.8, if Eq. (13) is used.(3) θ u,m : mean chord-rotation supply from Eq. (12), or θ u,m =θ y +θ pl u,m from Eq. (13).(4) V E,CD : shear force computed from equilibrium as in capacity-design.(5) V Rd,EC2 : shear resistance before flexural yielding, as given for monotonic loading in Eurocode2, using mean material strengths divided by partial factors of materials and by a “confidencefactor” that depends on the amount and reliability of available information.(6) V Rd,EC8 : shear resistance for shear failure in cyclic loading after flexural yielding, given by Eqs.(14)–(16) as applicable, with mean material strengths divided by partial factors for materialsand the “confidence factor” depending on the available information.(7) As in (5), (6) above, respectively, but using mean material strengths.3. THE FULLY PERFORMANCE-BASED PART 3 OF EUROCODE 8, FORTHE ASSESSMENT AND RETROFITTING OF OLDER BUILDINGS3.1 Performance Objectives for Assessment and RetrofittingPart 3 of Eurocode 8 (CEN 2004b) adopts a fully performance-based approach forexisting buildings. Three performance levels (termed “Limit States”) are defined:• “Near Collapse” (NC), similar to “Collapse prevention” in the U.S. In theverifications, a member may approach its ultimate force or deformationcapacity.• “Significant Damage” (SD), corresponding to “Life safety” in the US and tothe local-collapse prevention level for which new buildings are designed in8