… and prestressed concrete sections.
Today’s download installment covers spreadsheets for design of reinforced and prestressed concrete beams and columns at the Serviceability Limit State (SLS). The spreadsheets cover design of rectangular and circular sections, sections made up of any number of trapezoidal layers, and composite beams constructed in two stages. The spreadsheets for rectangular and circular sections also cover design at the Ultimate Limit State (ULS). Spreadsheets for ULS design of non-rectangular sections will be listed tomorrow.
The RC Design Functions spreadsheet provides functions for rectangular and circular sections It is described at:
Reinforced Concrete Moment-Curvature – 1 and
Tension Stiffening and
ULS design of reinforced concrete, AS, ACI and European codes
Download from: http://www.interactiveds.com.au/software/RC%20design%20functions6.zip
More details of using the included functions are given at:
Using RC Design Functions – 1, including examples: http://interactiveds.com.au/software/EStress%20Examples.xlsx
For non-rectangular sections use Beam Design Functions, described at:
Download from: http://www.interactiveds.com.au/software/Beam%20Design%20Functions.zip
Functions for design of composite sections are provided in two files, one using the Excel Goal-Seek function, and the other using a (much faster) VBA based solver:
Composite Beam Spreadsheet – 2 and
Composite Beam Spreadsheet 3
Download from: http://www.interactiveds.com.au/software/Composite%20Design%20Functions-GS.zip and
Example input and output from the spreadsheets is shown below, but download for a good look at all the functions available:
I have a question. Is there cracked concrete member check to deflection? Will be very useful.
The RC Design Functions spreadsheet has three options for checking the flexural stiffness of cracked sections, including the effect of tension stiffening:
– The EStress functions will return the section curvature according to Eurocode 2 (EC 2)
– The PLCurve function finds curvature including shrinkage effects by applying a fictitious compressive stress to the reinforcement.
– The TStiff function finds curvature of a cracked section using a concrete tensile stress-strain curve.
Have a play with the examples in the file and let me know if anytrhing is not clear.
At the moment the Beam Design Functions spreadsheet will give a curvature for a cracked section, but takes no account of tension stiffening. The results can be adjusted using the methods given in any of the design codes (EC 2 is recommended as the method in the US and Australian codes tends to be too stiff just after cracking).
For prestress force, there are two ways to do this in all the functions:
– Specify a prestress force in the strand. For pretensioned members this should be the stress in the strand before transfer because elastic losses are included in the analysis. For post-tensioned sections deduct the friction losses, losses due to wedge pull-in, and half the elastic loss.
– Alternatively add the prestress force and moment to the applied loads. In this case the force should have elastic losses deducted, as well as the other losses for post-tensioned members.
Note that in the EStress function the prestress is specified as a stress, but in the Beam Design Functions spreadsheet it is specified as a force per strand.
Thank you for reply, I will try to understand how it works 🙂
But, as I was asked earlier, I have problem with voided section. There no possible to define more than one void in section by width.
For example this: https://dl.dropbox.com/u/13038878/HCS.PNG
It is not possible to input my own section parameters? (Such as I,A,W etc…?)
Also I have question about prestressing force.
Is it calculate prestressing losses?
“But , as I was asked earlier, I have problem with voided section. There no possible to define more than one void in section by width.”
For multiple voids you can define the section by adding up all the concrete widths at each level, or probably easier find the external width and deduct the total width of void. That will give the correct results, but obviously the plot of the cross section will look nothing like the true cross section. Alternatively you could subdivide the section into beams with one void.
You can’t just specify the I and A values because the effective I and A depends on the depth of the Neutral Axis, so you have to specify the whole geometry.
Understand, but your spreadsheet, what find section properties from coordinates works very well. I was tried to put this section by coordinates and seems that all output properties is OK.
Maybe it is possible to combine them in future?
The problem is that the routine to find the depth of the NA uses a closed form solution that needs the concrete to be divided into trapezoidal layers, it just wouldn’t work with the section defined by coordinates.
For a section with several identical circular voids probably the easist thing to do is to calculate layer widths for one void then define a section with the overall concrete width and one large elliptical void, with the void layer widths being the dimension for one void times the number of voids.
Ok, thanks. Need to try.
There is a difference how to enter depth of reinforcement?
I mean it is possible to enter:
Or it need to be:
As I see there is a difference in output. Just want to be sure, thanks.
Here short example:
I see in description of Using Beam Design Functions that it must be entered from top to bottom 🙂 So no question any more.
Maybe it will be some of idea to make auto sort by depth.
Well I could, but I don’t think it will be a priority! 🙂
I have wrote you in email my question (with a lot pictures). I have one your in gmail history so I don’t know you use it still or not.
Please take a look if you will have some free minutes.
Reply sent by email.
Been playing around with your spread sheet, was not quite sure how you make it pick up more than the first 3 rows of reinforcement in the stage 1 section? I can see that the limits are set to those bar layers but is there an easy way to increase them?
Are you using the Composite Beam Design Spreadsheet?
If so, it assumes the section consists of a precast beam (of any shape) with a rectangular in-situ section on top. In the reinforcement listing the first two rows are the two layers in the in-situ concrete, then everything under that is in the precast, and you can have as many layers as you want. Note that for the reinforcement in the precast (row 3 onwards) the depth is measured from the top of the precast, not the top of the composite section.
If you were using a different spreadsheet, please let me know which one and the function name.