Practice in WOOD BEAM DESIGN – due beginning of class November 14
Use WoodWorks Sizer to answer the questions in this assignment, unless noted otherwise.
NOTE: You are being graded on your ability to accurately assess the problem and properly interpret the results of the software. Please read each question carefully.
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1. Read the document US Sizer tutorial and complete the Beam Mode Tutorial (page 3). Change the Live Load from 200 plf to 110 plf. Now answer the following questions:
a) If a 5ply 2×10 D.Fir-L is used in this application, the grade needs to be:
(no abbreviations: spell it out!) ____________________________________
NOTE: You will need to select (in the top ~middle of the screen) the 5ply 2×10 D.Fir-L option to find this information from the DESIGN CHECK CALCULATION SHEET. *Print this page and submit it.
b) What are the bending “design ratios” for the 5ply option?
for positive curvature: ___________________________________
for negative curvature : __________________________________
c) What is the “allowable shear stress”? ___________ psi.
d) What is the maximum “total load deflection” on the interior spans? _____ inches.
e) What is the governing design criteria for this beam? ________________
f) Re-run the design as a 5ply D.Fir-L No.2 or better 2X12. Print the DESIGN CHECK CALCULATION SHEET. From this sheet, fill in the following blanks:
i) The maximum bending moment anywhere in the beam is ____________ lbs-ft. (Hint: look at the critical load combinations at the bottom of the sheet to find this number)
ii) In which span(s) does this occur?_________________________. (Hint: look at the MVR “Analysis Results” page OR the “Analysis Diagrams” page to find this answer)
iii) Under which load combinations and load patterns does this occur? ________________.
2. A No. 1 Hem-Fir beam spanning 24 ft supports a permanent concentrated load of 1600lb at midspan. There are lateral supports at the ends of the beam only. Moisture Content in use will be greater than 19% and the beam will be incised for pressure treatment. Choose a safe cross section whose width is 6 inches nominal.
a) Print the “DESIGN CHECK CALCULATION SHEET” and submit.
b) What is the governing design criterion for this beam? ______________
c) What is the value of the incising factor for shear for this beam? __________
d) Read Chapter 6.3 in your text. Then:
i) On a separate page and using your own words, define the term Beam Stability factor. You will be marked on accuracy, language, spelling, and grammar.
ii) What is the value of the Stability factor for this beam? ___________________
iii) By modifying the ‘top lateral support spacing’, determine how closely spaced bracing would need to be to ensure that the beam stability factor is at least 0.999.
3) Design commercial roof joists with loading below and a horizontal projected span of 18.5 ft. Joists are spaced at 24 in. o.c. and have a 3:12 pitch. Plywood roof sheathing prevents lateral bucking. The joists are Dense Select Structural Southern Pine 3×8’s. MC < 19% and normal temperature conditions apply.
Dead load = 6 psf
Roof live from construction = 15 psf
Snow load = 10 psf
Wind load = 8 psf
Allow. ?L = L/240
Allow. ?TL = L/180
i) Print the DESIGN CHECK CALCULATION SHEET page and submit.
ii) What is the governing load combination for total load deflection?
iii) To save money, the developer would like to increase the tributary width of one joist only to 32 inches.
– Does this work? – explain why or why not. If not, suggest a practical solution to the problem.
– Print the DESIGN CHECK CALCULATION SHEET page and submit.
4. A 10 ¾ inch x 21 inch Western Species Glulam (E’= 1.3 x 106 psi) is used as a floor beam on a 25 ft simple span. Live load = 480 plf and dead load (including beam weight) = 280 plf.
i) Calculate by hand the live load deflection and total load deflection of the beam. Pass in your calculations.
ii) Will the beam perform adequately in deflection given the deflection limits
Allow. ?L = L/600
Allow. ?TL = L/480
iii) Run the same problem on Woodworks to confirm your answer. It should be the same values! Print the DESIGN CHECK CALCULATION SHEET page and submit.