In an example, we calculated the available flexural strength to be $M_n=216$kip$-$ft for the

section shown below.

The beam was comprised of $f_c^{\text{'}}=4000$ psi concrete and $4$#$8$ Gr$.60$ bars. In an attempt to

increase the available strength of the beam, the following two changes are made:

Increase the concrete compressive strength to $f_c^{\text{'}}=5500$

Increase the bar sizes to $4$#$9$ Gr$.60$ bars

Perform the following calculations for the new section.

Compute the nominal flexural strength, $M_n,$ for the new section.

Draw a strain profile for the new section at the point where $M_n$ is reached. Report

and label $c,$ the depth to the neutral axis, on your drawing.

Compute the strain in the tension steel when the new section reaches $M_n.$

Determine the resistance factor, $,$ for the new section.

Determine the available flexural strength, $M_n,$ for the new section.

Does the new section have more or less available strength than the original section? Are

the new section details and material properties allowable according to Article $9\mathrm{.}3\mathrm{.}3\mathrm{.}1$

of ACI $318-19?$