Roof Framing Connections in Conventional Residential
Construction (February 2002, 63 p.)
The NAHB Research Center has been engaged in a multifaceted
research program for the National Association of Home Builders
(NAHB) and the U.S. Department of Housing and Urban Development
(HUD) to quantify the structural performance of homes and
to develop or refine engineering methods that accurately model
conventional wood construction. The focus of this project
was on connections used with conventional light-frame wood
roof construction. A literature review was conducted and supplemented
with new research on the performance of conventional roof
systems and components including ceiling joist-to-rafter connections
and roof framing-to-wall connections. Individual connections
and connections within full-scale roof systems were tested
to quantify potential system effects. Hand-driven and pneumatic
fasteners were included in the test program. Test results
were compared to the provisions of the National Design Specification
for Wood Construction [1] and to predictions of the yield
theory using the general dowel equations for shear connections
[2]. Finally, the results were analyzed with respect to an
interest in establishing a consistent capacity basis for design
of wood-frame connections.
This report is organized in seven sections and an appendix.
Section 1 formulates the problem statement, summarizes the
major tasks completed under the project, and presents the
project objectives. In Section 2, background information is
provided on the design of nailed connections in light-frame
wood construction. A summary of relevant research is included
with the focus on key roof framing connections. Properties
of materials used in the testing program are reported in Section
3. Section 4 includes three subsections that present the corresponding
tasks of the research program on the performance of various
conventional roof framing connections. Each subsection is
organized as a self-contained document that presents objectives,
experimental methods, results and discussion, conclusions,
and a design application example (Tasks 1 and 2). The research
program addresses specific loading conditions and aspects
of system performance not documented in the reviewed literature.
Observed performance is compared to current engineering methods
for nailed wood connections. Project summary and conclusions
are provided in Section 5. Section 6 provides recommendations
and Section 7 includes references. Calculations of lateral
load resistance of nailed connections investigated in this
project are summarized in Appendix A.
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