Obtaining the section modulus.( for a beginner)

[paulina.styrczula]

Hello, i was searching all day a way to determinig the section modulus of the hollow core slab statical moment. I'm now angry and devastated cause i spent the whole day for founding the solution. Now i've found your autocalisp on the forum -> but dont understand how to use it in reality.i'm attaching my file in the autocad in case you would like to help me. my the whole group of students dunno how to manage so i will help them to ..if you do

hollow Lina.dwg

Edited March 12, 2019 by paulina.styrczula

[paulina.styrczula]

hollow Lina.dwg

[BIGAL]

Is this usefull been a long time since I did section modulus.

 

Massprop

 ----------------   REGIONS   ----------------

Area:                    31415.9265
Perimeter:               628.3185
Bounding box:         X: 5545.0335  --  5745.0335
                      Y: -517.6017  --  -317.6017
Centroid:             X: 5645.0335
                      Y: -417.6017
Moments of inertia:   X: 5557199768.3917
                      Y: 1.0012E+12
Product of inertia:  XY: 74059135048.1632
Radii of gyration:    X: 420.5843
                      Y: 5645.2550
Principal moments and X-Y directions about centroid:
                      I: 78539816.3397 along [0.9991 0.0421]
                      J: 78539816.3394 along [-0.0421 0.9991]

[paulina.styrczula]

but there isnt any reference to the section of modulus (first moment of inertia or statical moment). i am attaching the file without any structural complications ( just the section of which i want to obtain the section of modulus)

hollowslabLina.dwg

[Tharwat]

Hi,

Something like this?

(defun c:Test (/ sel)
  (princ "\nSelect Region object to get Moment of Inertia :")
  (if (setq sel (ssget "_+.:S:E" '((0 . "REGION"))))
    (princ
      (strcat "Moment of Inertia is : "
              (vl-princ-to-string
                (vlax-get (vlax-ename->vla-object (ssname sel 0))
                          'momentofInertia
                )
              )
      )
    )
    (alert "Invlaid object. Please select Region object.")
  )
  (princ)
) (vl-load-com)

 

[paulina.styrczula]

but what should i do with this? i assumed taht to paste this in the command line and to mark previously my object but nothing shows...

 

[Tharwat]

2 minutes ago, paulina.styrczula said:

but what should i do with this? i assumed taht to paste this in the command line and to mark previously my object but nothing shows...

 

Copy the codes to a notepad file then save it with the extension of .lsp the open AutoCAD then call the command APPLOAD or AP then select the previously created lisp file.

Finally type the command Test to start.

[paulina.styrczula]

Everything seems to be clear. but i have an error, just after clicking on the 'load' and  then on 'close'

[Tharwat]

How come the file itself does have a name?

[Tharwat]

It seems that you could not create the file correctly so please use the one in the attachments down here.

Test.LSP

[paulina.styrczula]

alright, ive used your file.But still nothing shows up.But there's a development-no errors. 

[Tharwat]

Now you need to call the command TEST then select the region object.

[paulina.styrczula]

omg i have it !!! Does this moment of inertia show up in tghe cpommand line?

Edited March 14, 2019 by paulina.styrczula

[Tharwat]

3 minutes ago, paulina.styrczula said:

omg i have it !!! Does this moment of inertia show up in tghe cpommand line?

It should do.  take a look at the command line after selecting the object.

[paulina.styrczula]

Thank you one more time. But are you sure it is modulus of section? usually second moment of inertia is mentioned in the autocad as moemnt of inertia. but after thorougly look on the units i can say that this is section modulus.. Second question: can i use this lsp file to all of the sections?i have also TT section to determine

[paulina.styrczula]

Thank you one more time. But are you sure it is modulus of section? usually second moment of inertia is mentioned in the autocad as moemnt of inertia. but after thorougly look on the units i can say that this is section modulus.. Second question: can i use this lsp file to all of the sections?i have also TT section to determine

 

EDIT: unfortunately it isnt sectoin modulus. Ive compared 'your' scores with my .It the same. whta i need is'section modulus..'

[paulina.styrczula]

the results are very similar. it is not what i wanted :((

[lrm]

Tharwart's program outputs the Moment of Inertia about the x and y axis through the centroid.  This yields the same value as provided by the massprop command.

 

I think you want the Principal Moment which is also provided by the massprop command.  I did a hand calculation assuming a rectangle (b*h^2)/6 and five round holes (pi *d^3)/32   and got a similar result to the massprop Principal Moment value.  Try it out yourself.

 

[paulina.styrczula]

its once again me. i know now how to paste file without error:) it was my fault. so now ive found ths like this on thje forum , but sth like in the screen appears.So now ive stucked in one place again

 

[paulina.styrczula]

also ive tried the second method as presented here. but the message  appears as below..