TABLE OF CONTENTS In this example, a large rough-sawn beam with a fairly short span is analyzed. The cross-sectional properties for dressed lumber (S4S) are smaller than those for rough-sawn lumber, and it would be conservative to use S4S section properties for this problem. However, the larger section properties obtained using the rough-sawn dimensions are used in this example. Refer to Sec. 4.11 for information on lumber sizes.
In this problem the basic shear adjustment of neglecting any loads within a distance d from the support is used. See Example 6.19.
The importance of understanding the size categories for sawn lumber is again emphasized. The member in this problem is a Beams and Stringers size, and tabulated design values are taken from NDS Supplement Table 4D.
EXAMPLE 6.19 Rough-Sawn Beam
Determine if the 6 14 rough-sawn beam in Fig. 6.19a is adequate to support the given loads. The member is Select Structural DF-L. The load is a combination of (D + L). Lateral buckling is prevented. The beam is used in dry-service conditions (MC
? 19 percent) and at normal temperatures. The beam is not incised. Allowable stresses are to be taken from the NDS Supplement Table 4D.
Section Properties
The dimensions of rough-sawn members are approximately 1/8 in. larger than standard dressed sizes.
Bending
The size factor for a sawn member in the Beams and Stringers category is given by the formula
The load duration...
