Table of Contents
Homework #3 ( Due September 24)
— David Wagner 2007/09/23 12:53
Solve problems 4.3, 4.4, 4.8, 4.12, 4.14, 4.16, 4.17, 4.20, and 4.23 in your textbook.
Problem 4.3
- a. Moisture Content: The percentage of water to oven-dry weight,
- b. Fiber Saturation Point: This is the moisture content with all of the free water removed and all of the bound water remaining.
- c. Equilibrium Moisture Content: the average moisture content the lumber has in service.
Problem 4.4
Moisture Content Ranges
- a. Dry Lumber: 19% or less,
- b. Green Lumber: over 19%
Problem 4.8
| Short Axis X-X | Long Axis Y-Y | |||||
|---|---|---|---|---|---|---|
| Dimension (inxin) | Dressed | Area (in²) | Section Modulus (in³) | I | Section Modulus (in4) | I |
| a. 2×4 | 1½x3½ | 5.25 | 3.063 | 5.359 | 1.313 | 0.984 |
| b. 8×8 | 7½x7½ | 56.25 | 70.31 | 263.7 | 70.31 | 263.7 |
| c. 4×10 | 3½x9¼ | 32.38 | 49.91 | 230.8 | 18.89 | 33.05 |
| d. 6×16 | 5½x15½ | 85.25 | 220.2 | 1707 | 78.15 | 214.9 |
Design Values for Wood Construction, 2005 Table 1B
Problem 4.12
| Dimension | Class | NDS Supplement Table |
|---|---|---|
| a. 10×12 | P&T | 4D |
| b. 14×14 | P&T | 4D |
| c. 4×8 | Dimension Lumber | 4A |
| d. 4×4 | Dimension Lumber | 4A |
| e. 2×12 | Dimension Lumber | 4A |
| f. 6×12 | B&S | 4D |
| g. 8×12 | B&S | 4D |
| h. 8×10 | P&T | 4D |
Problem 4.14
Grades for Visually Graded Hem-Fir
- a. Dimension Lumber: Select Structural, No.1 & Better, No.1, No.2, No.3, Stud, Construction, Standard, Utility;Table 4A
- b. Beams and Strings (B&S): Select Structural, No.1, No.2; NDS Supplement Table 4D
- c. Posts and Timbers (P&T): Select Structural, No.1, No.2; NDS Supplement Table 4D
Problem 4.16
Reference design values for No.1 DF-L (psi)
| Size | Fb | Ft | Fv | Fc⊥ | Fc | E | Emin | Rules | Table |
|---|---|---|---|---|---|---|---|---|---|
| a. 10×10 | 1,200 | 825 | 170 | 625 | 1,000 | 1,600,000 | 580,000 | WCLIB,WWPA | 4D |
| b. 12×14 | 1,200 | 825 | 170 | 625 | 1,000 | 1,600,000 | 580,000 | WCLIB,WWPA | 4D |
| c. 4×16 | 1,000 | 675 | 180 | 625 | 1,500 | 1,700,000 | 620,000 | WCLIB,WWPA | 4A |
| d. 4×4 | 1,000 | 675 | 180 | 625 | 1,500 | 1,700,000 | 620,000 | WCLIB,WWPA | 4A |
| e. 2×10 | 1,000 | 675 | 180 | 625 | 1,500 | 1,700,000 | 620,000 | WCLIB,WWPA | 4A |
| f. 6×12 | 1,350 | 675 | 170 | 625 | 925 | 1.600,000 | 580,000 | WCLIB,WWPA | 4D |
| g. 6×8 | 1,350 | 675 | 170 | 625 | 925 | 1.600,000 | 580,000 | WCLIB,WWPA | 4D |
| h. 10×14 | 1,350 | 675 | 170 | 625 | 925 | 1.600,000 | 580,000 | WCLIB,WWPA | 4D |
Problem 4.17
| Size | Fbn | Ftn | Fvn | Fc⊥n | Fcn | En | Emin-n |
|---|---|---|---|---|---|---|---|
| KF | 2.16/φ | 2.16/φ | 2.16/φ | 1.875/φ | 2.16/φ | – | 1.5/φ |
| φ | 0.85 | 0.80 | 0.75 | 0.90 | 0.90 | – | 0.85 |
| a. 10×10 | 2203 | 1426 | 275 | 1055 | 1944 | 1600000 | 739500 |
| b. 12×14 | 2203 | 1426 | 275 | 1055 | 1944 | 1600000 | 739500 |
| c. 4×16 | 1836 | 1166 | 292 | 1055 | 2916 | 1700000 | 790500 |
| d. 4×4 | 1836 | 1166 | 292 | 1055 | 2916 | 1700000 | 790500 |
| e. 2×10 | 1836 | 1166 | 292 | 1055 | 2916 | 1700000 | 790500 |
| f. 6×12 | 2479 | 1166 | 275 | 1055 | 1798 | 1600 | 739500 |
| g. 6×8 | 2479 | 1166 | 275 | 1055 | 1798 | 1600 | 739500 |
| h. 10×14 | 2479 | 1166 | 275 | 1055 | 1798 | 1600 | 739500 |
Problem 4.20
The load duration factor CD is the ASD factor used to account for the effects of load durations differing from those used to find the NDS table values.
while the time effect factor λ is used much as φ is used, to adjust the LRFD design resistance.
Problem 4.23
The reference design values Fc⊥ and E are not subject to adjustment for duration of loading by ASD.
The LRFD time effect Factor λ applies to load combinations and not to reference design values.
Discussion