Structural Steel Design - c.ymcdn.com

1 6 Structural Steel Design Rafael Sabelli, and Brian Dean, Originally developed by James R. Harris, , PhD, Frederick R. Rutz, , PhD and Teymour Manouri, , PhD Contents INDUSTRIAL HIGH-CLEARANCE BUILDING, ASTORIA, OREGON .. 3 Building Description .. 3 Design Parameters .. 6 Structural Design Criteria .. 7 Analysis .. 10 Proportioning and Details .. 16 SEVEN-STORY OFFICE BUILDING, LOS ANGELES, CALIFORNIA .. 40 Building Description .. 40 Basic Requirements .. 42 Structural Design Criteria .. 44 Analysis and Design of Alternative A: SMF .. 46 Analysis and Design of Alternative B: SCBF .. 60 Cost Comparison .. 72 TEN-STORY HOSPITAL, SEATTLE, WASHINGTON.

2 72 Building Description .. 72 Basic Requirements .. 76 Structural Design Criteria .. 78 Elastic Analysis .. 80 Initial Proportioning and Details .. 86 Nonlinear Response History Analysis .. 93 FEMA P-751, NEHRP Recommended Provisions: Design Examples 6-2 This chapter illustrates how the 2009 NEHRP Recommended Provisions (the Provisions) is applied to the Design of Steel framed buildings. The following three examples are presented: 1. An industrial warehouse structure in Astoria, Oregon 2. A multistory office building in Los Angeles, California 3. A mid-rise hospital in Seattle, Washington The discussion examines the following types of Structural framing for resisting horizontal forces.

3 Ordinary concentrically braced frames (OCBF) Special concentrically braced frames Intermediate moment frames Special moment frames Buckling-restrained braced frames, with moment-resisting beam-column connections The examples cover Design for seismic forces in combination with gravity they are presented to illustrate only specific aspects of seismic analysis and Design such as lateral force analysis, Design of concentric and eccentric bracing, Design of moment resisting frames, drift calculations, member proportioning detailing. All structures are analyzed using three-dimensional static or dynamic methods. ETABS (Computers & Structures, Inc., Berkeley, California, , 2008) is used in Examples and In addition to the 2009 NEHRP Recommended Provisions, the following documents are referenced: AISC 341 American Institute of Steel Construction.

4 2005. Seismic Provisions for Structural Steel Buildings, including Supplement No. 1. AISC 358 American Institute of Steel Construction. 2005. Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications. AISC 360 American Institute of Steel Construction. 2005. Specification for Structural Steel Buildings. AISC Manual American Institute of Steel Construction. 2005. Manual of Steel Construction, 13th Edition. AISC SDM American Institute of Steel Construction. 2006. Seismic Design Manual. IBC International Code Council, Inc. 2006. 2006 International Building Code. AISC SDGS-4 AISC Steel Design Guide Series 4. Second Edition.

5 2003. Extended End-Plate Moment Connections, 2003. chapter 6: Structural Steel Design 6-3 SDI Luttrell, Larry D. 1981. Steel Deck Institute Diaphragm Design Manual. Steel Deck Institute. The symbols used in this chapter are from chapter 11 of the Standard, the above referenced documents, or are as defined in the text. Customary units are used. INDUSTRIAL HIGH- CLEARANCE BUILDING, ASTORIA, OREGON This example utilizes a transverse intermediate Steel moment frame and a longitudinal ordinary concentric Steel braced frame. The following features of seismic Design of Steel buildings are illustrated: Seismic Design parameters Equivalent lateral force analysis Three-dimensional analysis Drift check Check of compactness and spacing for moment frame bracing Moment frame connection Design Proportioning of concentric diagonal bracing Building Description This building has plan dimensions of 180 feet by 90 feet and a clear height of approximately 30 feet.

6 It includes a 12-foot-high, 40-foot-wide mezzanine area at the east end of the building. The structure consists of 10 gable frames spanning 90 feet in the transverse (north-south) direction. Spaced at 20 feet on center, these frames are braced in the longitudinal (east-west) direction in two bays at the east end. The building is enclosed by nonstructural insulated concrete wall panels and is roofed with Steel decking covered with insulation and roofing. Columns are supported on spread footings. The elevation and transverse sections of the structure are shown in Figure Longitudinal struts at the eaves and at the mezzanine level run the full length of the building and therefore act as collectors for the distribution of forces resisted by the diagonally braced bays and as weak-axis stability bracing for the moment frame columns.

7 The roof and mezzanine framing plans are shown in Figure The framing consists of a Steel roof deck supported by joists between transverse gable frames. The mezzanine represents both an additional load and additional strength and stiffness. Because all the frames resist lateral loading, the Steel deck functions as a diaphragm for distribution of the effects of eccentric loading caused by the mezzanine floor when the building is subjected to loads acting in the transverse direction. The mezzanine floor at the east end of the building is designed to accommodate a live load of 125 psf. Its Structural system is composed of a concrete slab over Steel decking supported by floor beams spaced at 10 feet on center.

8 The floor beams are supported on girders continuous over two intermediate columns spaced approximately 30 feet apart and are attached to the gable frames at each end. FEMA P-751, NEHRP Recommended Provisions: Design Examples 6-4 The member sizes in the main frame are controlled by serviceability considerations. Vertical deflections due to snow were limited to inches and lateral sway due to wind was limited to 2 inches. Figure Framing elevation and sections ( ft = m; in. = mm) Earthquake rather than wind governs the lateral Design due to the mass of the insulated concrete panels. The panels are attached with long pins perpendicular to the concrete surface. These slender, flexible pins isolate the panels from acting as shear walls.

9 The building is supported on spread footings based on moderately deep alluvial deposits ( , medium dense sands). The foundation plan is shown in Figure Transverse ties are placed between the footings of the two columns of each moment frame to provide restraint against horizontal thrust from the moment frames. Grade beams carrying the enclosing panels serve as ties in the longitudinal direction as well as across the end walls. The Design of footings and columns in the braced bays requires consideration of combined seismic loadings. The Design of foundations is not included here. (c)East30'-6"3'-9"9'-0"32'-0"WestSiding: 6" concreteinsulated slabon gradeRoof moment-resistingsteel '-0"CeilingMezzaninemoment-resistingstee l frame34'-3"35'-0"(a)(b) chapter 6: Structural Steel Design 6-5 Figure Roof framing and mezzanine framing plan ( ft = m; in.)

10 = mm) 182'-0"Mezzanine90'-0"1200 MJ12C-joistW21x62W14x43112" type "B"22 gagemetal deck3" embossed20 gage deckNFEMA P-751, NEHRP Recommended Provisions: Design Examples 6-6 Figure Foundation plan ( ft = m; in. = mm) Design Parameters Ground motion and system parameters. See Section for an example illustrating the determination of Design ground motion parameters. For this example the parameters are as follows. SDS = SD1 = Occupancy Category II Seismic Design Category D Note that Standard Section permits an ordinary Steel moment frame for buildings that do not exceed one story and 65 feet tall with a roof dead load not exceeding 20 psf.