- Determine whether the joint complies with the Specification
Assume 'fA-in (23.8-mm) diameter bolt holes. The gross area of the dressed lumber is
63.25 in^2 (408.089 cm^2 ). The net area = gross area - area of the bolt holes = 63.25 -
3(0.94)(5.5) = 47.74 in^2 (308.018 cm^2 ). The bearing area under the bolts = number of
bolts [bolt diameter, in (mm)] [width, in (mm)] = 12(0.875)(5.5) = 57.75 in^2 (372.603
cm^2 ). The ratio of the net to bearing area is 47.74/57.75 = 0.83 > 0.80. This is acceptable,
according to the Specification. The joint is therefore satisfactory, and the assumptions are
usable in the design. - Establish the longitudinal bolt spacing
Using the Specification, we find a = 4(^7 / 8 ) = 3.5 in (88.90 mm); Z>min = 7(%) = 6% in
(155.58mm). - Establish the transverse bolt spacing
Using the Specification gives LID = 5.5(%) = 6.3 > 6. Make c = 2 in (50.8 mm) and d =
3% in (95.25 mm).
INVESTIGATION OF A
TIMBER-CONNECTOR JOINT
The members in Fig. 8a have the following sizes: A 9 4 x 8 in (101.6 x 203.2 mm); B, 3 x
8 in (76.2 x 203.2 mm). They are connected by six 4-in (101.6-mm) split-ring connectors,
in the manner shown. The lumber is dense structural redwood. Investigate the adequacy
of this joint, and establish the spacing of the connectors.
Calculation Procedure:
- Determine the allowable stress
The National Design Specification shows that the allowable stress is 1700 lb/in^2
(11,721.5 kPa). - Find the lumber group
The Specification shows this species is classified in group C. - Compute the capacity of the connectors
The Specification shows that the capacity of a connector in parallel-to-grain loading for
group C lumber is 4380 Ib (19,482.2 N). With six connectors, the total capacity is 6(4380)
= 26,280 Ib (116,890 N). This is acceptable.
FIG. 7