Transcript Slide 1
PDG: Post Design Graph - tutorial
PDG is an Excel program to design and visualize
posts in wood, steel, concrete, and masonry
PDG requires some knowledge of post design
PDG requires a PC with MS Excel macros Enabled
Press > for next step, < for previous step
Press Esc to end PDG
wood
PDG: Post Design Graph
steel
concrete masonry
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Bending (k”)
PDG: Post Design Graph - tutorial
Stress output
C = concrete
M = masonry
S = steel
W = wood
fb = bending stress
fa = axial stress
Input data info
Visualization graph
PDG: Post Design Graph
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PDG: Post Design Graph - tutorial
Select post material (5 to clear screen)
Prior to running PDG
Enter design data or use pre-defined data
Optionally, copy default data from TU to AB
Press Ctr-Shift-R to run PDG
PDG: Post Design Graph
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PDG: Post Design Graph - tutorial
Wood buckling
Allowable buckling stress F’c
F’c = F*c (CP)
F*c = Fc (CD) (CM) (Ct) X ……
Fc = Allowable compressive stress parallel to grain
CD = Duration factor (1=normal, 1.6=wind & seismic load)
CM = Moisture factor (1 for dry lumber)
Ct = Temperature factor (1for normal temperature)
X = Other adjustment factors for size, etc. per NDS
CP = Buckling stability defined by Ylinen formula:
Wood buckling
Allowable buckling graph
Horizontal axis: slenderness L/d
Vertical axis: allowable stress F’c
Allowable buckling load:
P = A F’c
A = cross section area
PDG: Post Design Graph
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1+ FcE /Fc* 1+ FcE /Fc* FcE /Fc*
CP =
-
2c
c
2c
c = 0.80 for sawn lumber
0.85 for round timber
0.90 for glulam posts
FcE = KcE E/(L/d)2 (Euler buckling stress)
KcE = 0.300 for visually graded lumber
0.384 for MEL (Machine Evaluated Lumber)
0.418 for glulam & MSR (Machine Stress Rated)
E = Elastic modulus
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PDG: Post Design Graph - tutorial
Steel buckling
(KL / r)2
1 2C 2 Fy
c
Fa
F.S.
Fa
12 2E
23 (KL / r)2
For Fy = 50 ksi Cc = 107
For Fy = 36 ksi Cc = 126
Inelastic
Elastic
Based on empirical tests steel has 2 buckling modes:
Inelastic buckling
(KL/r < Cc)
Elastic buckling
(KL/r > Cc)
Cc at ~ Fy/2 is derived using Euler’s formula:
2E
Fa
(L / r)2
at
Fy
2E
2 (L / r)2
L
22E
Cc
r
Fy
Allowable buckling stress:
Inelastic buckling:
(KL / r)2
1 2C 2 Fy
c
Fa
F.S.
F.S. = factor of safety, computed as:
5 3(KL / r) (KL / r)2
F.S.
3
8Cc
8Cc 3
Elastic buckling:
Fa
1.2 - 1.5
PDG: Post Design Graph
12 2E
23 (KL / r)2
K-factors theoretical - defined by support types
K’-factors recommended
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PDG: Post Design Graph - tutorial
Concrete buckling
Note: PDG uses approximate masonry slenderness reduction
Fc = InputBox("Input concrete compressive strength (3-12 ksi)")
Cpercent = InputBox("Input percent reinforcing (1-8%)")
Fy = InputBox("Select steel rebar strength Fy (50 ksi, 60 ksi)")
Fsc = 0.4 * Fy
Cfx = Cpercent / 100
Cf = 0.7 * 0.8 * 0.85 * (1 - Cfx) + Fsc * (Cfx)
If post = round Then Cf = 0.75*0.85*0.85*(1-Cfx)+Fsc*(Cfx)
D = concreteYdepth
If Cshape = 1 Then D = concreteXdepth
r = Sqr(D ^ 2 / 12)
If post = round Then D = concrete diameter: r = D / 2
Lrratio = (k * 12 * concretelength) / r
Aconc = concreteXdepth * concreteYdepth
If post = round Then Aconc = Pi*(concretediameter / 2)^2
For I = 1 To concretelength
h = I * 12
HRratio = h / r
Fa = Cf * Fc * (1 - (h / (140 * r)) ^ 2)
If HRratio > 99 Then
Fa = Cf * Fc * (70 * r / h) ^ 2
P = Fa * Aconc
Next I
PDG: Post Design Graph
Masonry buckling
Mpercent = InputBox("Input percent reinforcing (0.5-4%)")
Fy = InputBox("Select rebar strength Fy (50, 60 ksi)")
Fsm = 0.4 * Fy
D = masonryYdepth
If Mbuckling = 1 Then D = masonryXdepth
r = Sqr(D ^ 2 / 12)
HRratio = (k * 12 * masonrylength) / r
Agm = masonryXdepth * masonryYdepth
Asm = Agm * Mpercent / 100
Anm = Agm - Asm
Fmt = (0.25 * Fm * Anm + 0.65 * Asm * Fsm) / Agm
For I = 1 To masonrylength
h = I * 12
HRratio = h / r
Fa = Fmt * (1 - (h / (140 * r)) ^ 2)
If HRratio > 99 Then
Fa = Fmt * (70 * r / h) ^ 2
P = Fa * Agm
Next I
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PDG: Post Design Graph - tutorial
Copy any or all columns to paste into a new Excel sheet
to make graphs, or make graphs on this Excel sheet
PDG: Post Design Graph
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PDG: Post Design Graph - tutorial
Select Insert mode
Paste (Ctrl V) selections to a new Excel sheet
PDG: Post Design Graph
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PDG: Post Design Graph - tutorial
Select graph type
Select a column
To make graphs
PDG: Post Design Graph
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PDG: Post Design Graph - tutorial
Load graphs: wood
X-axis
Y-axis
PDG: Post Design Graph
steel
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concrete
masonry
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PDG: Post Design Graph - tutorial
Optionally move chart to separate sheet
Optionally scale chart
Format axis numbers without decimals
Select number sequence for proper density
PDG: Post Design Graph
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PDG: Post Design Graph - tutorial
Capacity (kip)
Optional color chart
Length (feet)
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