Editing Reinforced concrete (section)

===Mechanism of composite action of reinforcement and concrete===
The reinforcement in a RC structure, such as a steel bar, has to undergo the same strain or deformation as the surrounding concrete in order to prevent discontinuity, slip or separation of the two materials under load. Maintaining composite action requires transfer of load between the concrete and steel. The direct stress is transferred from the concrete to the bar interface so as to change the tensile stress in the reinforcing bar along its length. This load transfer is achieved by means of bond (anchorage) and is idealized as a continuous stress field that develops in the vicinity of the steel-concrete interface.
The reasons that the two different material components concrete and steel can work together are as follows:
(1) Reinforcement can be well bonded to the concrete, thus they can jointly resist external loads and deform.
(2) The thermal expansion coefficients of concrete and steel are so close
({{val|1.0|e=-5}} to {{val|1.5|e=-5}} for concrete and {{val|1.2|e=-5}} for steel) that the thermal stress-induced damage to the bond between the two components can be prevented.
(3) Concrete can protect the embedded steel from corrosion and high-temperature induced softening.