Civil Engineering: Building Structures Review
Filled with solved examples and problems, and key concepts and equations, this comprehensive review guide is for civil engineers who want to prepare for the building structures topics of the PE exam.
TABLE OF CONTENTS Civil Engineering: Building Structures Review
DESIGN OF WOOD STRUCTURES
Allowable Stresses
For swan lumber, the allowable stresses depend on the wood species, the size classification, the grade designation, and the method of grading. These items are defined in the NDS. 15 For visually graded sawn lumber, the basic design values are tabulated in the NDS SUPP 16 Table 4A. For machine-stress-rated lumber, the basic design values are tabulated in NDS SUPP Table 4C. For glued-laminated timber, the basic design values are tabulated in NDS SUPP Tables 5A-5C. These tabulated base values are applicable for normal conditions of use of duration of load and for dry conditions of service. NDS Sections 4.1.4 and 5.1.5 define dry conditions of service as moisture content not exceeding 19 percent for swan lumber and not exceeding 16 percent for glued-laminated timber. For other conditions of use, NDS Section 2.3 specifies the following adjustment factors:
Repetitive Member Factor, C r
When three or more sawn lumber elements not exceeding 4 inches in thickness and spaced not more than 24 inches apart are joined by a transverse load-distributing element, the bending stress may be increased. NDS Section 4.3.4 specifies that C r = 1.15.
Size Factor, C F
For visually graded sawn lumber joists exceeding 12 inches in depth and 5 inches in thickness the size factor, an adjustment for loss of tensile strength with increasing depth, is applied to the bending stress and is defined in NDS Section 4.3.2 as
The size factor for visually graded sawn...
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