V. Reactions in a 2D Truss Model 2

To find support reactions due to joint loads in a plane truss.

Reference

McCormack, J.C., Structural Analysis, Intext Educational Publishers, 3rd Edition, 1975.

Problem

Find the vertical and horizontal reactions at the supports of the truss.

E = 30,000.0 ksi

A = 100 in2

Loads as shown.

Comparison

Table 1. Comparison of results
Result Type Theory STAAD.Pro Difference
Horizontal, R1 (kips) 11.5 11.49 none
Vertical, R1 (kips) 34.3 34.29 none
Horizontal, R2 (kips) -31.7 -31.67 none
Vertical, R2 (kips) 36.0 36.0 none

STAAD Input

The file C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\ Verification Models\02 Trusses\Reactions in a 2D Truss Model 2.STD is typically installed with the program.

``````STAAD TRUSS :A PLANE TRUSS
START JOB INFORMATION
ENGINEER DATE 18-Sep-18
END JOB INFORMATION
*
* REFERENCE: MCCORMAC, J.C.,"STRUCTURAL ANALYSIS", INTEXT
*            EDUCATIONAL PUBLISHERS, NEW YORK, 3RD EDITION, 1975.
*
INPUT WIDTH 72
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 0 60 0; 3 12.5 60 0; 4 0 15 0; 5 0 30 0; 6 0 45 0;
7 9.375 45 0; 8 6.25 30 0; 9 3.125 15 0; 10 50 90 0; 11 100 90 0;
12 50 75 0; 13 25 75 0; 14 66.667 90 0; 15 83.333 90 0; 16 83.333 85 0;
17 66.667 80 0; 18 31.25 67.5 0; 19 200 0 0; 20 200 60 0; 21 187.5 60 0;
22 200 15 0; 23 200 30 0; 24 200 45 0; 25 190.625 45 0; 26 193.75 30 0;
27 196.875 15 0; 28 150 90 0; 29 150 75 0; 30 175 75 0; 31 133.333 90 0;
32 116.667 90 0; 33 116.667 85 0; 34 133.333 80 0; 35 168.75 67.5 0;
MEMBER INCIDENCES
1 1 4; 2 2 3; 3 3 7; 4 4 5; 5 5 6; 6 6 2; 7 7 8; 8 8 9; 9 9 1; 10 4 9;
11 9 5; 12 5 8; 13 8 6; 14 6 7; 15 7 2; 16 2 13; 17 10 14; 18 11 16;
19 12 18; 20 13 10; 21 14 15; 22 15 11; 23 16 17; 24 17 12; 25 18 3;
26 3 13; 27 13 18; 28 13 12; 29 12 10; 30 10 17; 31 17 14; 32 14 16;
33 16 15; 34 19 22; 35 20 21; 36 21 25; 37 22 23; 38 23 24; 39 24 20;
40 25 26; 41 26 27; 42 27 19; 43 22 27; 44 27 23; 45 23 26; 46 26 24;
47 24 25; 48 25 20; 49 20 30; 50 28 31; 51 11 33; 52 29 35; 53 30 28;
54 31 32; 55 32 11; 56 33 34; 57 34 29; 58 35 21; 59 21 30; 60 30 35;
61 30 29; 62 29 28; 63 28 34; 64 34 31; 65 31 33; 66 33 32;
UNIT INCHES KIP
MEMBER PROPERTY AMERICAN
1 TO 66 PRIS AX 100
UNIT FEET KIP
DEFINE MATERIAL START
ISOTROPIC MATERIAL1
E 4.32e+06
POISSON 0.290909
END DEFINE MATERIAL
UNIT INCHES KIP
CONSTANTS
MATERIAL MATERIAL1 ALL
SUPPORTS
1 19 PINNED
UNIT FEET KIP
LOAD 1 JOINT LOADS AT SPECIFIC NODES
JOINT LOAD
11 14 15 31 32 FY -10
10 28 FY -5
4 TO 6 FX 4
2 FX 2
2 10 FX 1.5435
13 FX 3.087
2 10 FY -2.5725
13 FY -5.145
PERFORM ANALYSIS
PRINT SUPPORT REACTION
FINISH
``````

STAAD Output

```   SUPPORT REACTIONS -UNIT KIP  FEET    STRUCTURE TYPE = TRUSS
-----------------
JOINT  LOAD   FORCE-X   FORCE-Y   FORCE-Z     MOM-X     MOM-Y     MOM Z
1    1     11.49     34.29      0.00      0.00      0.00      0.00
19    1    -31.67     36.00      0.00      0.00      0.00      0.00
```