Steel Frame Design - ladbs

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D. ORDINARY & SPECIAL CONCENTRICALLY BRACED FRAMES (OCBF/SCBF)9 1. K-Type brace frames are not permitted, except as per AISC I-14.5 & C14.4b ~9 2. Bolted stitches in the built-up braces of SCBF shall not be located in the middle onefourthof the clear brace length. AISC I-13.2e ~9 3. In a V-type and inverted V-type brace frame, a beam that is intersected by braces shall becontinuous between columns. AISC I-13.4a/I-14.4a ~E. ECCENTRICALLY BRACED FRAME (EBF)9 1. Web shall be single thickness without doubler-plate reinforcement & without penetration.9 2. Provide full-depth web stiffeners on both sides of the link web at the diagonal brace endsand at intermediate locations of the link, as per AISC-15.3a & 15.3b.~9 3. The intersection of the centerlines of the diagonal brace and the beam outside the Linkshall be at the ends of the Link or in the Link. AISC-15.6c.~9 4. Beam-to-column connections away from Links are permitted to be designed as pinnedin the plane of the web. AISC-15.7 ~CALCULATIONSA. GENERAL9 1. The total static design base shear in a given direction shall be determined per 91.1630.2.~9 2. In addition to the load combinations listed in 91.1612, the amplified horizontalearthquake load shall also be used if required by 91.1630.3.1. In addition to the loadcombination specifies in 91.1612, load combinations using the amplified horizontalearthquake load shall be evaluated per AISC I-4.1 as follows:~9 a) 1.2D + 0.5L + 0.2S + S o Q E , where the load factor on L in this load combination shallequal to 1.0 for garages, areas occupied as places of public assembly and all areaswhere the live load is greater than 100 psf.~9 b) 0.9D - S o Q E ~9 3. The drift or horizontal displacements of the structure shall be computed as required in91.1630.9.1 and shall be amplified as required in 1630.9.2. Story drift limits shall bedetermined as specified in 91.1630.10.~9 4. Orthogonal earthquake effects shall be included in the analysis as required in 91.1633.1.~9 5. Required strength of a connection or related member by using LRFD shall be determinedfrom the Expected Yield Strength F ye of the connected member. AISC I-6.2 The designstrength of structural steel members and connections by using ASD shall be determinedper AISC III-4.3.~LADBS-Corr.Lst.44 (5/2001)2 of 9www.ladbs.org
9 6. When P u /f P n for columns is greater than 0.4, the requirements in AISC I-8.2 must besatisfied.~9 7. The R value used to determine the base shear shall not be greater than the least R value ofthe different structural systems as specified in 91.1630.4.4.~9 8. Foundation of the steel frame shall be designed to resist applicable sliding shear, upliftforce, and/or moment.~B. SPECIAL MOMENT- RESISTING FRAMES (SMRF)9 1. The specified minimum yield strength of steel to be used for members, excludingcolumns, in which inelastic behavior is expected under the load combinationsshall not exceed 50 ksi. AISC I-6.1~9 2. The design of all beam-to-column joints and connections shall be based on qualifyingcyclic test results in accordance with AISC Appendix S that demonstrate an inelasticrotation of at least 0.03 radians. Qualifying test results shall consist of at least two cyclictests meeting requirements per AISC I-9.2a~9 3. Beam-to-column connection testing shall demonstrate a flexural strength that is at leastequal to the nominal plastic moment of the beam, M p , at the required inelastic rotation.AISC I-9.2b~9 4. The required shear strength Vu of a beam-to-column connection shall be determinedusing the load combination 1.2D + 0.5L + 0.2S plus the shear resulting from theapplication of 1.1R y F y Z in the opposite sense on each end of the beam. AISC I-9.2c~9 5. The required shear strength R u of the panel-zone need not exceed the shear forcedetermined from 0.8 time SR y M p of the beams framing to the column flanges at theconnection. AISC I-9.3a~9 6. Columns with width-thickness ratios less than or equal to 1.25 and beams shall complywith ? p in Table I-9-1 in Seismic Provisions for Structural Steel Buildings. AISC I-9.4b~9 7. Column-beam moment ratio shall be greater than 1.0 as required in AISC I-9.6.~9 8. For restrained connections, the requirements shown in AISC I-9.7a(2) shall be followedfor columns which cannot be shown to remain elastic outside of the panel-zone.~9 9. For unrestrained connections, a column containing a beam-to-column connection with nolateral support transverse to the seismic frame at the connection shall be designed usingthe distance between adjacent lateral supports as the column height for bucklingtransverse to the seismic frame. AISC I-9.7b~9 10. Both flanges of beams shall be laterally supported directly or indirectly. The unbracedlength between lateral supports shall not exceed 2500r y /F y . AISC I-9.8~LADBS-Corr.Lst.44 (5/2001)3 of 9www.ladbs.org
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