Design Aid for High Strength Reinforced Concrete Members: Beam Design Aids and Column Interaction Charts
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Date
2013-09
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Publisher
AAU
Abstract
Applicability of high-strength concrete (HSC) in reinforced concrete structures has
gained acceptability in the world as it allows efficient utilization of space and enhanced
structural performance. The Ethiopian Building Code Standards provides thorough
coverage for the design of reinforced concrete structures made of normal strength
concrete (NSC) and also provides design aids for NSC. The design considerations and
aids provided in the current code cannot be simply extrapolated for use in reinforced
HSC. This is because the mechanical properties of HSC under compression, shear and
tension are different from that of NSC. Thus a separate design consideration and aids
are required for reinforced HSC structural members. The current building code which
is under revision will include design consideration for reinforced HSC, however design
aids for HSC are missing. This study focuses on constructing design charts and tables
for solid rectangular beams and interaction charts for solid rectangular columns sections
made of HSC by using an iterative numerical based approaches. Stress-strain
relationship for concrete and reinforcing steel is adapted from Euro Code. The effect of
strain hardening for reinforcement steel is incorporated in the design aids. Exact method
of cross section analysis is used to estimate the ultimate capacity of structural members
when developing the design aids. Multiple application of Simpsons 1/3 rule is used to
estimate the total compressive force in the concrete when developing design table and
charts for beams. The design tables and charts can be used for any class of work as there
are no built-in safety factors. Uniaxial and biaxial interaction charts are constructed by
applying Green’s Theorem to transform double integrals to line integrals along the
compressive perimeter of the concrete section. The line integral itself is evaluated by
using Third Order Gauss integration to yield accurate results. Double counting of
concrete area that is displaced by the steel bars are taken into account. The algorithms
developed for preparation of these design aids are exact and computational efficient.
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Keywords
Concrete Members, Beam Design Aids, Column Interaction