Beam force analysis loads input

[ptc-4260912]

Hello,

In the attached sheet, Part 1 "Data input...." you will see "Number of Point Loads" is 4. In part 2"Input of all Loads", you will see 4 point loads. if i canhe the number of point loads to 10, how could i make the input of point loads cells to match the number of point loads 10? i can change the number of point loads to 10, but i want to be able to input more than 4 pont loads as shown in part2"Input of all loads", Thanks!

[Fred_Kohlhepp · Accepted solution]

Man, that's quite a work of art.

Let me start with a small quibble or two:

1) You define kiop as 1000 lb. If it's force (which is usual), it should be 1000 lbf. [Mathcad recognizes lb as mass and lbf as force, (the weight of one lb mass under the acceleration of gravity at the earth's surface.)]

2) You define the ORIGIN as 0 (you don't have to!) then start all of your index variables (i, j, and k) from 1. This leaves the first element in any vector undefined. (Mathcad stuffs in a zero and moves on, but it's sloppy!)

Now, adding places to the table! I'd not seen this method of inputing values before. You can do it; select the last element in your input (4 kip) and type a comma--another space appears! But I'd like to suggest another way--define the vector of loads and count how many you have.

[ptc-4260912]

Thank you so much Fred!!

[ptc-4260912]

Thank you so much Fred!!

[ptc-4260912]

Hello Fred,

in the Mathcadsheet that i attached earlier, item 5"Calculation of shear Forces"

i would like to evaluate shear at particular locations in the beam. i have detrmined the locations in a table format.

how can i make the shear equation V(x) use the x values in the table and generate another table with the shear values coresponding to these x values? is it possible to display both the x values and the corsponding shear value in one table? Thank you so much for your assitance!

[Fred_Kohlhepp]

SAM FARES wrote:

Hello Fred,

in the Mathcadsheet that i attached earlier, item 5"Calculation of shear Forces"

i would like to evaluate shear at particular locations in the beam. i have detrmined the locations in a table format.

how can i make the shear equation V(x) use the x values in the table and generate another table with the shear values coresponding to these x values? is it possible to display both the x values and the corsponding shear value in one table? Thank you so much for your assitance!

See added Area in item 5.

[ptc-4260912]

Fred,

I am not sure how to attach the latest mathcad sheet after i made some changes that you suggested. In the attachment you sent me, in item 5, you are manually placing the locations in the vector. However, what i am doing is calulcating the locations and generating a table like this:

Start: some value>0

End: Beam Length

increment : some value which is the distance between interior locations

N: ceil [( end-start)/increment]

h:0..N

Opening_xh: (start+h*increment) this equation will generate the table for X values. i need to use these x values in the shear equation.

i dont see a way to attach this mathcadsheet when i am replying to you. Thanks a lot!

[Fred_Kohlhepp]

SAM FARES wrote:

Fred,

I am not sure how to attach the latest mathcad sheet after i made some changes that you suggested. In the attachment you sent me, in item 5, you are manually placing the locations in the vector. However, what i am doing is calulcating the locations and generating a table like this:

Start: some value>0

End: Beam Length

increment : some value which is the distance between interior locations

N: ceil [( end-start)/increment]

h:0..N

Opening_xh: (start+h*increment) this equation will generate the table for X values. i need to use these x values in the shear equation.

i dont see a way to attach this mathcadsheet when i am replying to you. Thanks a lot!

See modified sheet.

When you reply, a reply box opens. In the upper right corner a "use advanced editor" tag is visible. If you select that, the ability to attach files is at the bottom.

[ptc-4260912]

Thanks Fred!

i am still getting an error with the calculation of shear. would you tell me why? attached is the sheet. Thanks!

[Fred_Kohlhepp]

SAM FARES wrote:

Thanks Fred!

i am still getting an error with the calculation of shear. would you tell me why? attached is the sheet. Thanks!

You define b as a vector at the top. At the startt of section 5 you define b as single valued (6.925 in); this overwrites the vector definition. All of your vector summation functions now will fail because they're expecting b to be a vector.

[Fred_Kohlhepp]

SAM FARES wrote:

Thanks Fred!

i am still getting an error with the calculation of shear. would you tell me why? attached is the sheet. Thanks!

You define b as a vector at the top. At the startt of section 5 you define b as single valued (6.925 in); this overwrites the vector definition. All of your vector summation functions now will fail because they're expecting b to be a vector.

[Fred_Kohlhepp]

SAM FARES wrote:

Thanks Fred!

i am still getting an error with the calculation of shear. would you tell me why? attached is the sheet. Thanks!

You define b as a vector at the top. At the startt of section 5 you define b as single valued (6.925 in); this overwrites the vector definition. All of your vector summation functions now will fail because they're expecting b to be a vector.

[ptc-4260912]

Fred,

I am not sure how to attach the latest mathcad sheet after i made some changes that you suggested. In the attachment you sent me, in item 5, you are manually placing the locations in the vector. However, what i am doing is calulcating the locations and generating a table like this:

Start: some value>0

End: Beam Length

increment : some value which is the distance between interior locations

N: ceil [( end-start)/increment]

h:0..N

Opening_xh: (start+h*increment) this equation will generate the table for X values. i need to use these x values in the shear equation.

i dont see a way to attach this mathcadsheet when i am replying to you. Thanks a lot!

[ptc-4260912]

In part 11 in the attached mathcadsheet, why is the unit for the deflection is messed up(lb/ft2 .mm). i boxed up these values. Thanks Fred!

[Fred_Kohlhepp]

SAM FARES wrote:

In part 11 in the attached mathcadsheet, why is the unit for the deflection is messed up(lb/ft2 .mm). i boxed up these values. Thanks Fred!

You started confusuing units when you defined kip as a mass. (Go read my first post closely!)

Attached is a sheet that calculates a square section cantilever beam with an end load, moment, and tension force (CF.) Units are correct throughout. You can use this as a template to develop your general solver if you like; develop moment as a function of position along the beam and input it as M(x) in the solver.

If you start wrong (using lb instead of lbf) you can't finish right; I don't have the time or patience to unravel this thread.

[ptc-4260912]

Thanks Fred for all your help!

Earlier today i changed the unit for Kip=1000lbf, hoping it will fix the units, but it did not. i thought Mathcad will take care of the units, but not this time. i thought the solution would be a quick one by much more experienced user such as you. This is the reason why i posted the question.

Thanks alot Fred you have been big help!

[Fred_Kohlhepp]

As a good rule, if the units don't balance out then there are equations wrong. I would start looking at your integrals of polynomials.

Note that if you can define the equation for moment along the beam (M(x)), then the solution of the differential equation will give you the deflected position. Derivative of that (once) is slope, second derivative is moment. Approximating deflection (y(x)) with a high-order polynomial (regress) yields well-behaved functions for derivatives. So if you can get to moment as inch-pounds of force (in * lbf) units should fall out.

[Fred_Kohlhepp]

As a good rule, if the units don't balance out then there are equations wrong. I would start looking at your integrals of polynomials.

Note that if you can define the equation for moment along the beam (M(x)), then the solution of the differential equation will give you the deflected position. Derivative of that (once) is slope, second derivative is moment. Approximating deflection (y(x)) with a high-order polynomial (regress) yields well-behaved functions for derivatives. So if you can get to moment as inch-pounds of force (in * lbf) units should fall out.

[wayne]

After the correction of kip=1000lbf,

In the first collapsed area after the beam diagram, you re-defined E, without units. Delete this and units work out.

FYI, if you change to singularity functions, the math is a lot easier, and is a classical solution, no numerical approximation or integration or solvers, so is a lot faster. Anyway, good job keeping it all straight.

(if interested and need a reference, see Advanced Strength and Applied Stress Analysis, Richard G. Budynas)

[ptc-4260912]

yes that fixed the problem. Thanks Wayne!

[ptc-2377935]

I'm having trouble with this *.xmcd file format in Mathcad Prime.

What am I missing on getting it to read?

Is there some confusion here between *.xmcd and *.mcdx ?

Any hints for someone, and old time (*.mcd) user trying to manipulate archane champion's PTC's making the "simple" complex?

Thanks!

Max H.

[VladimirN]

Mathcad Prime 1.0 can only open the file in the format ".mcdx". But you can use the converter "XMCD, MCD Converter" to convert files from earlier versions of Mathcad (formats ".mcd", ".xmcd"). However, when converted into the format ".mcdx" it should be noted that this will not be converted: 3D-plots, symbolical calculation, mathematical formulas in text fields, instead of them in the new converted file will be inserted images.