PDG: Post Design Graph Copyright Prof Schierle 2012 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 steel concrete masonry
PDG: Post Design Graph Copyright Prof Schierle 2012 2
PDG: Post Design Graph - tutorial
Stress outputC = concreteM = masonryS = steelW = woodfb = bending stress fa = axial stress
Input data info
Visualization graph
PDG: Post Design Graph Copyright Prof Schierle 2012 3
PDG: Post Design Graph - tutorial
Select post material (5 to clear screen)
Prior to running PDGEnter 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 Copyright Prof Schierle 2012 4
PDG: Post Design Graph - tutorialWood bucklingAllowable buckling stress F’c
F’c = F*c (CP)
F*c = Fc (CD) (CM) (Ct) X ……
Fc = Allowable compressive stress parallel to grainCD = 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 NDSCP = Buckling stability defined by Ylinen formula:
2* * *cE c cE c cE c
P
1+ F /F 1+ F /F F /FC = - -
2c 2c c
c = 0.80 for sawn lumber 0.85 for round timber 0.90 for glulam postsFcE = 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
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 Copyright Prof Schierle 2012 5
PDG: Post Design Graph - tutorial
2
a 2
12 EF
23 (KL / r)
Elastic buckling:
Allowable buckling stress:Inelastic buckling:
K-factors theoretical - defined by support typesK’-factors recommended
2
a 2
EF
(L / r)
2
y2
F E2 (L / r)
at
2
cy
L 2 EC
r F
Steel bucklingBased 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:
For Fy = 50 ksi Cc = 107 For Fy = 36 ksi Cc = 126
2
y2c
a
(KL / r)1 F
2CF
F.S.
2
a 2
12 EF
23 (KL / r)
2
y2c
a
(KL / r)1 F
2CF
F.S.
2
3c c
5 3(KL / r) (KL / r)F.S.
3 8C 8C
F.S. = factor of safety, computed as:
1.2 - 1.5
Inelastic Elastic
PDG: Post Design Graph Copyright Prof Schierle 2012 6
PDG: Post Design Graph - tutorialConcrete bucklingNote: PDG uses approximate masonry slenderness reductionFc = 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 * FyCfx = Cpercent / 100Cf = 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 = concreteXdepthr = Sqr(D ^ 2 / 12) If post = round Then D = concrete diameter: r = D / 2Lrratio = (k * 12 * concretelength) / rAconc = concreteXdepth * concreteYdepth If post = round Then Aconc = Pi*(concretediameter / 2)^2For 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 * AconcNext I
Masonry bucklingMpercent = InputBox("Input percent reinforcing (0.5-4%)")
Fy = InputBox("Select rebar strength Fy (50, 60 ksi)")Fsm = 0.4 * FyD = masonryYdepth If Mbuckling = 1 Then D = masonryXdepthr = Sqr(D ^ 2 / 12)HRratio = (k * 12 * masonrylength) / rAgm = masonryXdepth * masonryYdepthAsm = Agm * Mpercent / 100Anm = Agm - AsmFmt = (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 * AgmNext I
PDG: Post Design Graph Copyright Prof Schierle 2012 7
PDG: Post Design Graph - tutorial
Copy any or all columns to paste into a new Excel sheetto make graphs, or make graphs on this Excel sheet
PDG: Post Design Graph Copyright Prof Schierle 2012 8
PDG: Post Design Graph - tutorial
Paste (Ctrl V) selections to a new Excel sheet
Select Insert mode
PDG: Post Design Graph Copyright Prof Schierle 2012 9
PDG: Post Design Graph - tutorialSelect graph type
Select a column
To make graphs
PDG: Post Design Graph Copyright Prof Schierle 2012 10
PDG: Post Design Graph - tutorial
Load graphs: wood steel concrete masonry X-axis
Y-axis
PDG: Post Design Graph Copyright Prof Schierle 2012 11
PDG: Post Design Graph - tutorial
Select number sequence for proper density
Optionally move chart to separate sheetOptionally scale chart
Format axis numbers without decimals
PDG: Post Design Graph Copyright Prof Schierle 2012 12
PDG: Post Design Graph - tutorial
Optional color chart
Length (feet)