05-05ChapGere.0004 - because the shear flow on the contact...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Problem 5.11-6 Two wood box beams (beams A and B ) have the same outside dimensions (200 mm 3 360 mm) and the same thickness ( t 5 20 mm) throughout, as shown in the figure on the next page. Both beams are formed by nailing, with each nail having an allowable shear load of 250 N. The beams are designed for a shear force V 5 3.2 kN. (a) What is the maximum longitudinal spacing s A for the nails in beam A ? (b) What is the maximum longitudinal spacing s B for the nails in beam B ? (c) Which beam is more efficient in resisting the shear force? Solution 5.11-6 Two wood box beams SECTION 5.11 Built-Up Beams 353 z y O z y O 200 mm 360 mm 360 mm t = 20 mm t = 20 mm A 200 mm B Cross-sectional dimensions are the same. All dimensions in millimeters. b 5 200 b 1 5 200 2 2(20) 5 160 h 5 360 h 1 5 360 2 2(20) 5 320 t 5 20 F 5 allowable load per nail 5 250 N V 5 shear force 5 3.2 kN s 5 longitudinal spacing of the nails f 5 shear flow between one flange and both webs s max 5 2 FI VQ f 5 2 F s 5 VQ I I 5 1 12 ( bh 3 2 b 1 h 1 3 ) 5 340.69 3 10 6 mm 4 (a) B EAM A 5 680 3 10 3 mm 3 5 78.3 mm (b) B EAM B 5 544 3 10 3 mm 3 5 97.9 mm (c) B EAM B IS MORE EFFICIENT
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: because the shear flow on the contact surfaces is smaller and therefore fewer nails are needed. s B 5 2 FI VQ 5 (2)(250 N)(340.7 3 10 6 mm 4 ) (3.2 kN)(544 3 10 3 mm 3 ) Q 5 A f d f 5 ( b 2 2 t )( t ) ¢ h 2 t 2 ≤ 5 (160)(20) 1 2 (340) s A 5 2 FI VQ 5 (2)(250 N)(340.7 3 10 6 mm 4 ) (3.2 kN)(680 3 10 3 mm 3 ) Q 5 A p d p 5 ( bt ) ¢ h 2 t 2 ≤ 5 (200)(20) ¢ 1 2 ≤ (340) Problem 5.11-7 A hollow wood beam with plywood webs has the cross-sectional dimensions shown in the figure. The plywood is attached to the flanges by means of small nails. Each nail has an allowable load in shear of 30 lb. Find the maximum allowable spacing s of the nails at cross sections where the shear force V is equal to (a) 200 lb and (b) 300 lb. z y O 3 in. — in. 3 16 — in. 3 16 8 in. in. 3 4 in. 3 4 A-PDF Split DEMO : Purchase from www.A-PDF.com to remove the watermark...
View Full Document

This note was uploaded on 09/20/2009 for the course COE 3001 taught by Professor Armanios during the Spring '08 term at Georgia Institute of Technology.

Ask a homework question - tutors are online