The Museum of HP Calculators

# Section Properties for Composite Body Cross-Sections for the HP-35s

This program is by Eric Lundgren and is used here by permission.

This program is supplied without representation or warranty of any kind. Eric Lundgren and The Museum of HP Calculators therefore assume no responsibility and shall have no liability, consequential or otherwise, of any kind arising from the use of this program material or any part thereof.

## Overview

This program computes the Ixx area moment of inertia and Xbar horizontal neutral axis for a composite body that is discretized with rectangles. There is no limit to the number of rectangles, as such you can approximate curvilinear edges with an appropriate number of rectangles.

You can also get the Iyy and Ybar by re-running it for the same body, while referencing left or right side as the base (ie, turn an I-beam on its side and enter the dimensions).

Slight modifications will also permit the extraction of final area.

## Listing

```I001 LBL I
I002 SF 10
I003 EQN IXX and Neutral Axis
I004 CF 10
I005 CLVARS
I006 INPUT N
I007 INPUT B
(note: I have omitted line numbers from here on)

INPUT H
RCL H
2
/
RCL +T
RCL B
RCL * H
*
RCL +Q
STO Q
RCL B
RCL H
*
RCL +R
STO R
1
RCL +V
STO V
RCL Q
RCL / R
RCL - C
X^2
RCL *A
RCL + I
STO I
RCL T
RCL H
2
/
+
RCL Q
RCL / R
-
X^2
RCL *B
RCL *H
RCL H
3
Y^X
RCL *B

12
/
+
RCL + I
STO I
RCL Q
RCL / R
STO C
RCL B
RCL * H
RCL + A
STO A
RCL T
RCL +H
STO T
RCL V
RCL N
X>Y?
GTO I007

I=  **This is the value of composite Ix for your cross-section**
C= **This is the location of Xbar, ie the X neutral axis**

RTN

LN=220
CK=704D

Here is an example for an I-beam:

XEQ I ENTER

screen will read: IXX AND NA (hit R/S to continue)

N=3 **number of sections**

R/S

B=5 **width of bottom flange**

R/S

H=0.25 **height of bottom flange**

R/S

B=0.5 **width of web**

R/S

H=8 **height of web**

R/S

B=3 **width of upper flange**

R/S

H=0.25 **height of upper flange**

R/S

(Program halts to VIEW the area moment of inertia, units length^4)

R/S

(Program halts to VIEW the location of the x centroidal axis)

R/S

The result should be

I = 54.6660 (units = length^4)

C = 3.9063 (units = length, measured from base)```