Graduation date: 2007
Light-frame construction practices and materials have changed greatly
over the past 100 years. Contemporary research has focused on modern
construction; thus, we know a great deal about the behavior of modern lightframe
buildings under lateral forces. However, there are many light-frame
buildings that were built prior to the introduction of modern building codes and
material standards, and these buildings are still in service. The material and
performance databases for these older structures are limited, so risk assessment
and condition assessment are challenged for seismic or wind events. The
project objective is to establish a basis for probabilistic assessment of the
seismic performance of older construction by examining the performance of
shearwalls, connections, and wood materials from older light-frame buildings
Nineteen structures built between 1900 and 1970, scheduled for
demolition, were sampled for material and connection tests as well as full-size
shearwall tests. The scope of tests for each source structure was based on the
availability of full-size shearwalls and the type of sheathing material used in the
structure. Two exterior sheathing types were found in the source structures,
horizontal plank sheathing and plywood. Wood lath-and-plaster was the
characteristic interior wall covering in buildings of this era. Specific gravity was
determined, and embedment tests were performed on the wood framing and
sheathing materials. Bending-yield tests were performed on the sheathing nails
(typically 0.113 by 2.5- in.), and lateral single-nail connection tests were
performed on extracted connections. Full-scale shearwall racking tests were
done both monotonically and cyclically using the basic CUREE loading protocol.
The average specific gravity of the wood materials was 0.46. The material
extracted from the source structures had an embedment strength that was
statistically similar to the National Design Specifications (NDS) table value for a
specific gravity of 0.46 (4.0 ksi). The results of the nail bending-yield test showed
no significant change over time. Nails had average bending-yield strength of
97.3 ksi, which is similar to the NDS stated value of 100 ksi. In general, the
connection tests showed agreement with the European Yield Model (EYM)
equations for connection strength. The full-size shearwall capacities were in
agreement with known values for walls with each type of sheathing.
Based on the limited testing done in this study, no adverse effects due to
age and service life were observed. The materials and assemblies performed
according to modern standards for new construction. Insect damage and fungi
deterioration were present in many of the structures, and because these
conditions were avoided as much as possible, no inferences are made regarding
the effects of insect and fungi damage on lateral shear strength. These tests
show that a structure built in the early 1900’s will meet modern design
expectations as long as the material has been kept dry and free of damage due
to insects.
The principal threats to hazard performance observed during this study
were the construction practices in the early twentieth century. Most of the source
structures had no anchorage to the foundation, shearwalls were connected to
roof diaphragms with limited toe nail connections, most structures were sheathed
with horizontal planks, and many of the source structures had few walls that met
the modern prescribed aspect ratio for structural shearwalls of 2:1 for full table
design capacity. The results of this research can be integrated with the Federal
Emergency Management Administration (FEMA) document on seismic
rehabilitation for buildings.