Example 01: Spacing of Screws in Box Beam

A concentrated load P is carried at midspan by a simply supported 4-m span beam. The beam is made of 40-mm by 150-mm timber screwed together, as shown. The maximum flexural stress developed is 8.3 MPa and each screw can resist 890 N of shear force.



  1. Determine the spacing of screws at A.
  2. Determine the spacing of screws at B.
  3. Determine the spacing of screws if screws at A and B are equally spaced.


Example 01: Maximum bending stress, shear stress, and deflection

A timber beam 4 m long is simply supported at both ends. It carries a uniform load of 10 kN/m including its own weight. The wooden section has a width of 200 mm and a depth of 260 mm and is made up of 80% grade Apitong. Use dressed dimension by reducing its dimensions by 10 mm.

Properties of Apitong
Bending and tension parallel to grain = 16.5 MPa
Shear parallel to grain = 1.73 MPa
Modulus of elasticity in bending = 7.31 GPa

1. What is the maximum flexural stress of the beam?
2. What is the maximum shearing stress of the beam?
3. What is the maximum deflection of the beam?




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