Scipediacontent: Scipediacontent moved page Draft Content 867051146 to Friedman 2021a

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Scipediacontent moved page Draft Content 867051146 to Friedman 2021a

Scipediacontent: Created page with "== Abstract == The introduction of reinforced concrete as a structural material in American practice circa 1900 created unique challenges in design and analysis. E..."

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Created page with "== Abstract == The introduction of reinforced concrete as a structural material in American practice circa 1900 created unique challenges in design and analysis. E..."

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== Abstract ==

The introduction of reinforced concrete as a structural material in American
practice circa 1900 created unique challenges in design and analysis. Engineers and builders
had to simultaneously determine proper constituent materials for the concrete, the relation
between materials proportions and strength, and formulas for sharing load between steel and
concrete. Early on there were only local building codes, which often treated concrete as
masonry. This was followed, starting in 1909, by the reports of the “Joint Committee” which
served as a de facto national code for concrete; the American Concrete Institute code was
first independently published in 1941 and has been updated regularly since.
All of the early codes, specifically including the Joint Committee report and the ACI code,
used allowable-stress design with a linear-elastic model of flexure. Load-and-resistance
factor design using an ultimate-strength model was first introduced in the US as an alternate
method in the 1956 ACI code, was elevated to equal status with the 1963 code, and was made
the standard in the 1971 code with the linear-elastic allowable-stress model as an alternate.
Since the ultimate-strength model is generally accepted to more accurately represent flexure
in reinforced concrete, the allowable-stress alternate was little used after the transition.
Many details have changed minimally since the 1910s, including provisions for T beams
that take advantage of the slab for additional compression flange area. The calculation of
shear capacity in both concrete and web reinforcing changed minimally except for the
transition from allowable-stress to load-and-resistance-factor design.
Re-analysis of extant concrete structures designed before the 1956 code generally shows a
pattern of significant excess capacity in flexure and limited excess capacity in shear. For
members that are generally not controlled by one-way (beam) shear (two-way slabs and one-
way slabs) the increase in flexure capacity governs; for members where one-way shear is a
controlling factor, the small increase, no change, or decrease in shear capacity governs.
Much of the current literature on evaluating the capacity of extant concrete structures
focusses on strength degradation from material changes such as rusting rebar and from
overall material changes such as carbonation. The presence of excess capacity should also be
considered, and it is possible based on review of the governing codes and design methods to
determine general patterns as to how much excess capacity may be expected.

== Full document ==
<pdf>Media:Draft_Content_867051146p704.pdf</pdf>

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Scipediacontent: Scipediacontent moved page Draft Content 867051146 to Friedman 2021a

Scipediacontent: Created page with "== Abstract == The introduction of reinforced concrete as a structural material in American practice circa 1900 created unique challenges in design and analysis. E..."