1Lateral force design Copyright Prof Schierle 2011 1Lateral force design Copyright Prof Schierle 2011 2Portions of this document reproduce sections from the 2003 International Building Code, International Code Council, Falls Church, Virginia. All rights reserved.Copy data from LDG screenSeismic data brownWind data greenRead chapter 9Design for WindLDG: Lateral Design Graph - TutorialLateral force design Copyright Prof Schierle 2011 3Design for WindLateral force design Copyright Prof Schierle 2011 3Paste data to a new Excel sheet to visualize data with charts2Lateral force design Copyright Prof Schierle 2011 4Click Arch 499 then click LDG & LDG tutorial, etcLateral force design Copyright Prof Schierle 2011 5Lateral load resisting elements1 Shear wall / gravity load2 Shear wall / lateral load3 Cantilever / gravity load4 Cantilever / lateral load5 Moment frame /gravity load6 Moment frame / lateral load7 Braced frame / gravity load8 Braced frame / lateral loadLateral force design Copyright Prof Schierle 2011 6Lateral load resisting systems1 Shear wall2 Cantilever3 Moment frameA Moment resistant reinforced concrete jointB Moment resistant steel joint4 Braced framebracing is usually around corebut façade bracing is strongerExample: Ten-story shear wall / post building 100’ x 50’ x 10’ story heightYX3Lateral force design Copyright Prof Schierle 2011 7X-wind - design wall lengths LAssume Fv= 75 psiq = 75 (8”x12”) / 1000 q = 7.2 klfLevel 10 L = 12 k / 7.2 klf L = 2’Use code min 2 walls @ L = 4’ eachLevel 5 L = 71 k / 7.2 klf L = 10’Use code min 2 walls @ L = 5’ eachLevel 1L = 112 k / 7.2 klf L = 16’Use min 2 walls @ L = 8’ eachFrames @ 25’ resist overturn MPost load P = M / B (B = frame width)Level 10M = 123 k’ (25/100) M = 31 k’P = 31 / 50’ P = 0.6 kLevel 5M = 2524 k’ (25/100) M = 631 k’P = 631 / 50’ P = 12.6 kLevel 1M = 6423 k’ (25/100) M = 1606 k’P = 1605 / 50’ P = 32.1 kLateral force design Copyright Prof Schierle 2011 8Y-wind - design wall lengths LAssume Fv= 75 psiq = 75 (8”x12”) / 1000 q = 7.2 klfLevel 10 L = 25 k / 7.2 klf L = 4’Use code min 2 walls @ L = 4’ eachLevel 5 L = 142 k / 7.2 klf L = 20’Use min 2 walls @ L = 10’ eachLevel 1L = 225 k / 7,2 klf L = 31’Use min 2 walls @ L = 16’ eachFrames @ 25’ resist overturn MPost load P = M / B (B = frame width)Level 10M = 247 k’(25’/100’) M = 62 k’P = 62 / 50’ P = 1.2 kLevel 5M = 5048 k’(25’/100’) M = 1262 k’P = 1262 / 50’ P = 25 kLevel 1M = 12845 k’(25’/100’) M = 3211 k’P = 3211 / 50’ P = 64 kLateral force design Copyright Prof Schierle 2011 9Wind loadSteady wind is static Gusty wind is dynamic4Lateral force design Copyright Prof Schierle 2011 10Wind load• Pressure on wind side• Suction on lee side• Uplift on roof leeside1 Wind load on gabled building2 Wind load on dome or vault3 Protected city buildings4 Exposed tall building5 Exposed wide façade6 Forms can increase wind speedLateral force design Copyright Prof Schierle 2011 11Kzfactor graphWind pressure (IBC/ASCE 7 Method 2, Analytical Procedure)p = qG Cp–qi(GCpi) [minimum p = 10 psf (480 Pa)]q velocity pressure (defined below)qz for windward wall (evaluated at height z above ground)qh for leeward wall (constant, per mean roof height h)G gust factor (G = 0.85 for rigid structure ≥ 1 Hz)GCpi Internal pressure (± 0.18 for enclosed structures)Cp pressure coefficient (from ASCE 7 figures and tables)Cp= 0.8 (windward walls)Cp= - 0.2 to - 0.5 (leeward walls)Cp= - 0.3 to + 0.4 (for roofs)q= 0.00256 I KzKztKdV2(q = velocity pressure in psf)V = wind speed, mph (IBC Fig. 1609, or local speed) I = Importance factor (IBC table 1604.5)I = 1 (all structures not listed below)I = 1.15 (hospitals, police and fire stations, etc)I = 0.87 (agricultural and temporary facilities)KZtTopography factor (KZt= 1 for regular sites)Kd Directionality factor (Kd = 0.85 for most structures)KZ Exposure factor (graph at left, min. 0.7 for gladding)B = Exposure B (inner city, protected)C = Exposure C (open area, unprotected)D = Exposure D (near ocean or large lakes)Lateral force design Copyright Prof Schierle 2011 12IBC Fig. 1609. Basic wind speed Values are nominal design 3-second gust wind speeds in mph (m/s), 33 ft (10 m) above ground for Exposure C. Special wind regions shall be examined for special wind conditions5Lateral force design Copyright Prof Schierle 2011 13HurricaneLateral force design Copyright Prof Schierle 2011 14Photos courtesy Applied Research Associates, Raleigh. North CarolinaLateral force design Copyright Prof Schierle 2011