Analysis of Reinforced Concrete D-Regions Using Strut-and-Tie Model

The developed Strut-and-Tie Model (STM) has no unique shape for each load case
of a given structural problem as long as the selected idealized internal load-resisting
truss is in equilibrium with boundary forces, and also stresses in its components
"struts, ties, and nodes" are within acceptable limits. However, the optimal shapes
are the well-designed with best ordinal weight number of conditional factors as the
rebar amount, the load factor, and the structural concrete ductility. The current
study investigates numerically based on FE method stress flow contours and micro
truss techniques many alternatives with different shapes of struts and ties that
transfer the flow of forces from top of the deep beam with opening to both right and
left supports. Then, these alternatives with different concrete characteristics are
analyzed by strut-and-tie computational tools using different code provisions for
verifying its results accuracy with the numerical nonlinear finite element analysis
results for studying the structure performance under applied service loads and over
loading till failure. The chosen alternative produce load factor to reach capacity
greater than 1, therefore the strut-and-tie method always give demand collapse load
lower than the true capacity collapse load. This implies that the solution obtained
from STM usually lies on the safe side with conservative sense for concrete
structures subjected to service loads. That’s why the STM is emerging as an
increasingly popular code-worthy methodology for the design and detailing of
concrete structures D-Regions.