Slender concrete walls incorporated into tilt-up construction
over the past 60 years have performed remarkably well under
out-of-plane wind and seismic loads. While issues associated
with seismic wall anchorage gave this form of construction a
black-eye in the early days, the concrete walls themselves
have always performed very well even as far back as their
first use in the early 1900s. Yet the height-to-thickness
limitations in 1985 and earlier model building codes were
proved irrational and were removed. We as engineers expect
building codes to evolve and advance the state of the art with
each successive edition. The latest edition of ACI 318-08 has
significantly revised the slender walls design procedures, yet
not necessarily advancing the state of the art. The latest ACI
318 edition is largely revising slender wall design back to
match equations found in the old 1997 UBC.
This paper revisits the historical effort SEAOSC played in the
development of the original slender wall provisions in the late
1970s, and why ACI is now revising their slender wall design
provisions to agree with concepts developed over 30 years
ago by SEAOSC. While these original concepts were based
on empirical data from full-scale tests conducted in the early
1980s, only within the last five years have we really begun to
fully understand the behavior of these thin concrete members
when subjected to combined axial load and large horizontal


Architectural Engineering


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