Prepared for this example are seven files: 1_a.xsf, 1_b_max_rebar.xsf, 1_b_min_rebar.xsf, 1_c.xsf, 2_120.xsf, 2_220.xsf and 2_280.xsf. These are available only in inch pound units.
Download these files:
An article “Flexural Design of Reinforced Concrete Beam Sections” by Qian Wang and Shahriar Quayyum was published in Structure magazine in two parts; Part 1 April 2023 p36 – 39 and Part 2 June 2023 p28 – 31.
The online version of that article at STRUCTUREmag.org included numerical examples. Parts of those examples are reworked here using the application.
The examples determines strength reduction factors in accordance with ACI 318-19. The application does not compute or apply strength reduction factors.
Here the application computes the ultimate strength bending moment of the cross-sections described.
The application results also present information relevant to the strength reduction factor such as the strain in the extreme layer of tension steel.
The example in part 1 of the article has three parts labelled “a”, “b” and “c”.
The example in part 2 of the article also has three parts. These have headings “Bending Moment, Mu = 120 k – ft”, “Bending Moment, Mu = 220 k – ft” and “Bending Moment, Mu = 280 k – ft”. It is only the bending moment value in k – ft that is used here in the xsf file names.
Hence the file names: 1_a.xsf, 1_b_max_rebar.xsf, 1_b_min_rebar.xsf, 1_c.xsf, 2_120.xsf, 2_220.xsf and 2_280.xsf.
If any one of these files is loaded in to the application and the computations invoked the result should agree with the corresponding result in the article; both the ultimate strength bending moment and the strain in the extreme layer of tension steel.
The resulting bending moments displayed by the application are presented with units “k.in”. That is intended to mean “kips-inches”. So the number needs to be divided by twelve to present it in kips-feet for comparison with the kips-feet numbers presented in the article.
The strain values displayed with the result are presented with units “x10-3”. That is intended to mean that the number is to be multiplied by 10-3 .
On a desktop device
In the application result display on a desktop device the relevant bending moment value is on a line labeled “Moment – reference axis”. Note that it is the unfactored bending moment in kips-inches.
To see the various strain values close the “Compute” dialog to reveal the “Loadcase” dialog and on that click on the “Display result” button. Then scroll down to where the extreme strains in each component are displayed. This is a table intended for a fixed character width font. Unfortunately if such a font is not in use the column headings will not line up with the columns.
On a mobile device
In the application result display on a mobile device the relevant bending moment value is on a line labeled “Mom. ref. axis”. Note that it is the unfactored bending moment in kips-inches.
As regards the extreme strain values the mobile version of the application has a “Write result to a text file” button that produces the same report as the “Display result” button on the desktop version. However, there is no facility in the application to inspect that report. Instead the mobile version has facilities that display a lot more detail.
To use those facilities, click on the next button in the top right corner twice. The first click will cause a change from the trial and adjustment result to a fuller result description. The second click will reveal a display of the details of one corner of the concrete or of one rebar. (On an iPad click on the “Display result” button and then on the “Inspect result details” button.) At the top of this display is a selection box for the various components and below that the identification number of a particular corner or rebar and forward and backward buttons that allow any particular corner or rebar to be chosen.
In the body of the display is information about the strain at the particular corner or in the particular rebar. In this case the Stage strain and Other strain will be zeros and the Load case strain, Total strain and Stress strain will all have the same value. Also in this case it is a simple matter to find the rebar with the extreme tensile strain.