Transcript Slide 1
LDG: Lateral Design Graph - tutorial LDG is an Excel program to design and visualize design for lateral wind and seismic forces LDG requires some knowledge of lateral force design LDG requires a PC with MS Excel macros Enabled Press > for next step, < for previous step Press Esc to end LDG: Lateral Design Graph Copyright Prof Schierle 2009 1 Lx Ly Ly Ly Ly Ly Lx Lx Lx Lx LDG computes floor area A = (Lx Ly) assuming rectangular plans. to get correct seismic values, prorate dead load to represent the actual floor area. For example, if the floor area of a plan is 30% smaller, reduce the dead load 30% LDG: Lateral Design Graph Copyright Prof Schierle 2009 2 LDG: Lateral Design Graph - tutorial Enter design factors prior to running LDG Seismic data brown Wind data green Velocity Pressure Coefficient Kz = Exposure factor Copy columns TU into AB as default if needed Data position is critical for LDG to run properly LDG: Lateral Design Graph Copyright Prof Schierle 2009 3 LDG: Lateral Design Graph - tutorial 20 Press Ctrl-Shift-R to start LDG (Excel macro) Select input type: 0, 1, 2, or 3 0 = as is, run current structure displayed or as modified 1 = uniform: floors, story height, and mass 2 = tapered: changing from base to top 3 = custom: unique floors or stacks of floors Then input (for 1, 2, 3 only): Number of levels Level length (ft) Level width (ft) Story height (ft) Mass (Dead Load in psf = pounds / ft2) LDG: Lateral Design Graph Copyright Prof Schierle 2009 Input Importance factors 4 LDG: Lateral Design Graph - tutorial IBC Table 1604.5. Importance factors Category Seismic Use Group I I II III I II IV III Nature of Occupancy Low hazard structures: Agriculture, temporary, minor storage Structures not in categories I, III, IV Facilities such as: Occupancy > 300 people per area Elementary schools > 250 students Colleges > 500 students Occupancy > 5000 Essential facilities, such as: Hospitals, polices and fire stations Seismic Importance Factors 1 Snow Importance Factors 0.8 Wind Importance Factors 0.87 1 1.25 1 1.1 1 1.15 1.5 1.2 1.15 Lateral loads - acting primarily horizontally are: Wind load Seismic load Earth pressure on retaining walls (not in LDG) LDG: Lateral Design Graph Copyright Prof Schierle 2009 5 LDG: Lateral Design Graph - tutorial Fa factors, IBC Table 1615.1.2 [1] (low-rise) Sds = (2/3)(Fa SS) [Ss = top line] Fv factors, IBC Table 1615.1.2 [2] (high-rise) Sd1 = (2/3)(Fv S1) [S1 = top line] Importance factors Press Ctrl-Shift-R to run LDG US wind velocity map LDG: Lateral Design Graph Copyright Prof Schierle 2009 6 LDG: Lateral Design Graph - tutorial Seismic Design V = Cs W = seismic base shear (lateral force @ building base) W = mass = (DL + 25% storage LL) CS = I Sds / R [seismic equation for T<TS] CS = I Sd1/(RT) [for T>TS<TL] 2 CS = I Sd1 TL / (RT ) [for T>TL] I= Importance Factor [see slide 1] Sds = (2/3)(Fa SS) [see Fa table - low-rise] Sd1 = (2/3)(Fv S1) [see Fv table - high-rise) TS = Sd1/Sds [see Spectrum @ left] T ~ 0.1(# stories) [building period = cycles/second] SS & S 1 [see USGS Table] R = R-factor [see IBC Table 1617.6.2] TL = Time Laps [range 4 -12, ASCE7 Fig 22-15] Note: LDG: Lateral Design Graph CS ~ 0.03 for high-rise moment frames CS ~ 0.15 for wood structures CS ~ 0.30 for masonry structures W = w A [A = floor area] w ~ 25 psf for wood structures w ~ 70 psf for steel structures w ~ 150 psf for concrete structures Copyright Prof Schierle 2009 7 LDG: Lateral Design Graph - tutorial USGS seismic factors USC: SS = 1.85 (low-rise), S1 = 0.64 (high-rise) LDG: Lateral Design Graph Copyright Prof Schierle 2009 8 LDG: Lateral Design Graph - tutorial LDG: Lateral Design Graph Copyright Prof Schierle 2009 9 LDG: Lateral Design Graph - tutorial Wind Design V = p A = wind base shear (lateral force @ building base) p = wind pressure (in psf = pounds / square foot) A = exposed tributary area p = wind pressure (psf) p = 0.00256 V2 I Cp G Kd Kz Kzt V = velocity (mph) I = Importance Factor (see slide 1) Cp = external pressure coefficient Cp = 0.8 windward Cp = 0.2 to 0.5 leeward G = Gust factor G = 0.85 for rigid structures G = 1.3 - 1.5 for fabric structures Kd = 0.85 for buildings [directionality factor] Kz = 2.01 (Z/Zg)2/ Z = height above ground Exposure Zg B Inner city 1200 7.0 C Open area 900 9.5 D Near ocean or lake 700 11.5 Kzt = Velocity Factor = 1 for flat sites LDG: Lateral Design Graph Copyright Prof Schierle 2009 10 LDG: Lateral Design Graph - tutorial Graph see Structure and Design page 577 LDG: Lateral Design Graph Wind pressure (IBC/ASCE 7 Method 2, Analytical Procedure) p = qGCp–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 (Rigid G=0.85, fabric structure G=> 1.2) 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) KZt Topography 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) Copyright Prof Schierle 2009 11 LDG: Lateral Design Graph - tutorial Optional select and copy (Ctrl C) data to make graphs at another sheet or make graphs on this Excel sheet LDG: Lateral Design Graph Copyright Prof Schierle 2009 12 LDG: Lateral Design Graph - tutorial Select a chart type Paste selected data into another Excel sheet Select data LDG: Lateral Design Graph Copyright Prof Schierle 2009 13 LDG: Lateral Design Graph - tutorial Fwx &Vwx (k) LDG: Lateral Design Graph Fwy &Vwy (k) Copyright Prof Schierle 2009 14 LDG: Lateral Design Graph - tutorial LDG: Lateral Design Graph Copyright Prof Schierle 2009 15 LDG: Lateral Design Graph - tutorial 14-story seismic force Fs & shear Vs 14 13 12 11 10 9 8 Vs (k) 7 Fs (k) 6 5 4 3 2 1 0 LDG: Lateral Design Graph 50 100 150 200 250 300 Copyright Prof Schierle 2009 350 400 450 500 16 LDG: Lateral Design Graph - tutorial Mwy (k ') 14-story wind overturn moment 14 13 12 11 10 9 8 Mwy (k ') 7 6 5 4 3 2 1 0 LDG: Lateral Design Graph 5000 10000 15000 20000 Copyright Prof Schierle 2009 25000 30000 17