ABSTRACT
These are the basic assumptions and in the actual design to find the amount of reinforcement required we can use: (a) design charts: (b) design formulae; or (c) strain compatibility.
These are in Part 3 of the Code and have been prepared using the rectangular-parabolic stress block for the concrete and the bilinear stress-strain curve for the reinforcement. The charts are for rectangular sections reinforced in tension only (singly reinforced), or in tension and compression (doubly reinforced). Appendix A of Part 3 gives notes on the derivation of the charts and in the equation for the concrete compressive force at failure it can be seen that 0.45/cu has been used rather than 0.67/cu/1.5. As in the previous charts, the full area of concrete in compression has been assumed even where compression reinforcement is present. The singly reinforced charts are for reinforce ment Grade 250 and Grade 460 with different concrete grades.
