Combined stress conditions

Compression stress condition about the y-y axis (equation (5.35) (EC5, 6.3.2(3))) Compression stress condition about the z-z axis (equation (5.36) (EC5, 6.3.2(3)))

Combined stress condition (equation (5.38); EC5, equation (6.35))

As all relationships are less than unity, the glulam member will meet the ULS requirements of EC5.

Example 6.7.3 Single tapered glulam beams 150 mm wide, having a profile as shown Figure E6.7.3, and with an effective span of 9.0 m are to be used in the construction of the roof of an exhibition hall. The roof is braced laterally at 3.0 m centres along its top face to provide full lateral support at these positions and load sharing between glulam beams will not apply. The beams are glulam strength class GL 28h in accordance with BE EN 1194:1999 and will function in service class 1 conditions and is to be subjected to the characteristic loading given below. Confirm the beam will comply with the design rules in EC5.

Beam loading:

Characteristic permanent vertical load on each beam 1.65 kN/m

Characteristic short-term variable vertical load on each beam 2.25 kN/m

1. Glulam beam geometric properties

Breadth of each beam, b b = 150 mm

Minimum depth at the tapered end, hs hs = 320 mm

Maximum depth of each beam, he he = 750 mm

Effective span of each beam, l

Distance between bracing positions along the tapered face, lc

Bearing length at each end of the beam, lb

Angle of slope of the tapered face, tan a =

2. Glulam properties

Table 6.2, homogeneous grade GL 28h l = 9.0m lc = 3.0m lb = 150 mm hi - hs

Characteristic bending strength,

Characteristic shear strength, /v g k Characteristic bearing strength,

Mean modulus of elasticity parallel to the grain, £0 g mean

Characeristic modulus of elasticity parallel to the grain, £o.o5.g

Mean shear modulus, G0 g mean

Characteristic shear modulus,

Mean density of each beam (based on the ratio of pm/pk obtained from BS EN 338:2003)

0 0

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