LDG: Lateral Design Graph - tutorial LDG: Lateral Design Graph Copyright Prof Schierle 2011 1 LDG is an Excel program to design and visualize design for

LDG: Lateral Design Graph - tutorial

LDG: Lateral Design Graph Copyright Prof Schierle 2011 1

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 - Tutorial Copyright Prof Schierle 2011 2


Lx LxLx 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%



Enter design factors prior to running LDG

Seismic data brown

Wind data green

Copy columns TU into AB as default if neededData position is critical for LDG to run properly



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 mass2 = tapered: changing from base to top3 = custom: unique floors or stacks of floors

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Lateral loads - acting primarily horizontally are:Wind loadSeismic loadEarth pressure on retaining walls (not in LDG)

IBC Table 1604.5. Importance factors Category Seismic

Use GroupNature of Occupancy Seismic

Importance Factors

SnowImportanceFactors

Wind Importance Factors

I I Low hazard structures:Agriculture, temporary, minor storage

1 0.8 0.87

II I Structures not in categories I, III, IV 1 1 1III II Facilities such as:

Occupancy > 300 people per area Elementary schools > 250 students Colleges > 500 studentsOccupancy > 5000

1.25 1.1 1.15

IV III Essential facilities, such as:Hospitals, polices and fire stations

1.5 1.2 1.15



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



Seismic DesignV = 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]CS = I Sd1 TL / (RT2) [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 & S1 [see USGS Table] R = R-factor [see IBC Table 1617.6.2]TL = Time Laps [range 4 -12, ASCE7 Fig 22-15]

Note: CS ~ 0.03 for high-rise moment framesCS ~ 0.15 for wood structuresCS ~ 0.30 for masonry structuresW = w A [A = floor area]w ~ 25 psf for wood structures w ~ 70 psf for steel structuresw ~ 150 psf for concrete structures



USC: SS = 1.85 (low-rise), S1 = 0.64 (high-rise)

USGS seismic factors





Wind DesignV = p A = wind base shear (lateral force @ building base) p = wind pressure (in psf = pounds / square foot) A = exposed tributary areap = 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 windwardCp = 0.2 to 0.5 leeward

G = Gust factorG = 0.85 for rigid structuresG = 1.3 - 1.5 for fabric structures

Kd = 0.85 for buildings [directionality factor] Kz = 2.01 (Z/Zg)2/

Z = height above groundExposure Zg B Inner city 1200 7.0C Open area 900 9.5D Near ocean or lake 700 11.5

Kzt = Velocity Factor = 1 for flat sites



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)

Graph see Structure and Design page 577



Optional select and copy (Ctrl C)data to make graphs at another sheetor make graphs on this Excel sheet



Paste selected data into another Excel sheet

Select a chart type

Select data



Fwx &Vwx (k) Fwy &Vwy (k)

Fs &Vs (k)



Select R

Select Ss &S1Select TL

Select wind speed, etc.



14-story seismic force Fs & shear Vs



14-story wind overturn moment

Read chapter 9

Documents

LDG: Lateral Design Graph - tutorial LDG: Lateral Design Graph Copyright Prof Schierle 2011 1 LDG is an Excel program to design and visualize design for