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)