04-05 Stiffness and strength of timber beam

Problem 4
The stiffness of a rectangular beam is proportional to the breadth and the cube of the depth. Find the shape of the stiffest beam that can be cut from a log of a given size.
 

Problem 5
The strength of rectangular beam is proportional to the breadth and the square of the depth. Find the shape of the strongest beam that can be cut from a log of given size.
 

Problem 1005 | Maximum concentrated load at the midspan that the reinforced timber beam can carry

Problem 1005
A timber beam 6 in. by 10 in. is reinforced only at the bottom by a steel plate as shown in Fig. P-1005. Determine the concentrated load that can be applied at the center of a simply supported span 18 ft long if n = 20, fs ≤ 18 ksi and fw ≤ 1200 psi. Show that the neutral axis is 7.1 in. below the top and that INA = 1160 in.4.
 

1005-given-timber-and-steel.gif

 

Solution to Problem 581 | Design for Flexure and Shear

Problem 581
A laminated beam is composed of five planks, each 6 in. by 2 in., glued together to form a section 6 in. wide by 10 in. high. The allowable shear stress in the glue is 90 psi, the allowable shear stress in the wood is 120 psi, and the allowable flexural stress in the wood is 1200 psi. Determine the maximum uniformly distributed load that can be carried by the beam on a 6-ft simple span.