A01-Simply-Supported-Truss-LAB- Manual- Revised-JAN-2021 -blurred-out skyciv values for trial 1 PDF

Preview

Summary

efwrfffrgge ED8CTGUOQJWHDSA CQWDHSAC N WDSCYB;diebf bcqudisbdxcqwufdsahbmfasc...

Description

Faculty of Engineering

Physics 1 Laboratory

Group No: ____ Members: __________________ ___________________________ ___________________________ ___________________________ __________________________

Section:_____ Date:____________ Instructor:______________

ACTIVITY # 1 SIMPLY SUPPORTED TRUSS I. Objectives At the end of this activity, the students should be able to: 1. Identify parts and equipment on the Truss Set used in the laboratory 2. Measure axial forces acting on the beams on the Truss Set 3. Compute for axial forces acting on the members using the method of joints 4. Analyze the effect of a varying loads to the truss members of the bridge II. 1. 2. 3. 4. III.

Laboratory Equipment Structural Truss Set 3 Load Sensors with (Load Cell Amplifier and Airlink for wireless transfer of Data) Set of Hooked Masses (0.1kg, 0.1kg, 0.2 kg, 0.2 kg, 0.5 kg, 1kg ) 2 Beam Balances Concepts Involved A01 SS TRUSS Introduction Video is available at this link: https://ust.ap.panopto.com/Panopto/Pages/Viewer.aspx?id=b43c2e0c-4648-4607-8a2bacc100908f33

1. Different types of trusses 2. Solution to systems of concurrent member forces and parallel (externally applied) forces 3. Concept of tension and compression members IV.

Procedures / Diagrams 1. Assemble the Structural Truss set according to the schematic diagram and photo in Figure 1.1 Schematic Diagram of the Truss Assembly and Figure 1.2 Structural Truss Set (Actual) respectively.

1

Faculty of Engineering

Physics 1 Laboratory

Figure 1.1 Schematic Diagram of Structural Truss Set

Figure 1.2 Structural Truss Set (Actual) 2. Click on the link below to view the demonstration video of A01 SS Truss. (the following procedures are as demonstrated on the A01 SS Truss Video Demo1 Setup) https://ust.ap.panopto.com/Panopto/Pages/Viewer.aspx?id=885bff9d-8174-4f24-826eacc10090cef9 3. Connect load cells to the truss assembly, one at the bottom chord (BC), one at the top chord (TC), and another at the web (W). Label the load cells as BOTTOM. WEB and TOP. (refer to Figure 1.2) 4. Place the truss assembly on two beam balance. With points A and F centered on the beam balance surface.

Mode O/TARE ON

Figure 1.3 Structural Truss Set on Beam Balances 5. Connect load cells’ wire to the Load Cell Amplifier. (bottom load cell 1 to terminal 1, web load cell to terminal 2 and top load cell to terminal 3. 6. Connect the Load Cell Amplifier to an Airlink (take note of the Airlinks’ serial number). 7. Turn on the Airlink’s Bluetooth signal. Observe the battery charge indicator. Charge the airlink if needed. 2

Faculty of Engineering

Physics 1 Laboratory

8. Download the “Spark Vue” application from Google Play Store. And install the app on either on a cellphone or a tablet or a laptop. The readings from the load cells may be displayed through these devices 9. On your device, pick on the SparkVue Icon. Choose Sensor Data.

Figure 1.4 SparkVue Icon

Figure 1.5 SparkVue Initial Interface

10. Choose the corresponding airlink on the SparkVue interface

Figure 1.6 SparkVue Interface, connecting to Airlink

11. Uninstall the member BD (Top Chord) together with the installed load cell.

Figure 1.7 Top Chord member uninstalled from the assembly 12. On the SparkVue Interface, the “measurement templates” tab will appear. Place a check mark on Force 3 only for the mean time, and then choose digits display. 13. Start collecting Data 14. Take note of the reading. At “no load” condition, the reading should be “Zero”. 3

Faculty of Engineering

Physics 1 Laboratory

Figure 1.8 Top Chord reading not calibrated (incorrect reading) 15. Press the "tare button” at the right end of the Load Cell Amplifier to calibrate the load cell. If needed press the "tare button” a few more times until “almost Zero value” is displayed. An “almost zero value” indicates that the load cell giving the correct reading.

Figure 1.9 TARE Button at the Load Cell Amplifier

4

Faculty of Engineering

Physics 1 Laboratory

Figure 1.10 Top Load Cell giving the correct reading 16. Attach a half octagonal connector to the right end of the top chord. 17. Attach a label on top of the display device indicating the load cell’s convention. The label will serve as a reminder as to whether the joint is experiencing Tension or Compression

Figure 1.11 Tension and Compression Convention Label 18. Apply a force directed TOWARDS the joint as shown in Figure 1.12. Take note of the “sign” given out by the load cell. Check if it agrees with the convention label. (+) Positive-Compression

5

Faculty of Engineering

Physics 1 Laboratory

Joint

Figure 1.12 (+) Positive Reading displayed when the Joint on the Right experiences Compressive Force 19. Apply a force, this time, directed to the left by pulling at the left end of the beam as shown in Figure 1.13. Take note of the “sign” given out by the load cell. (-) Negative-Tension

Joint

Figure 1.13 (-) Negative Reading is displayed when the Joint on the Right experiences Tensile Force 20. The load cell test clearly established that the convention or meaning of a positive and a negative reading.

Figure 1.14 Load cell reading Convention 21. Re-install the top beam at its original position.

6

Faculty of Engineering

Physics 1 Laboratory

Figure 1.15 Top beam Re-installed 22. Press the icon on the upper left corner of the SparkVue interface with three bars to end the experiment. Then choose start a new experiment. No need to save previous experiment.

Figure 1.16 Icon to end an experiment and start a new one. 23. At the initial SparkVue interface, choose Sensor data. Choose on the Airlink that we are using (572-580 Airlink). Place a check mark on the Force 1, Force 2 and Force 3 boxes. Then choose digits display.

7

Faculty of Engineering

Physics 1 Laboratory

Figure 1.17 SparkVue set-up to use the three load cells. 24. Press start. Take note of the three readings displayed. Since there are no load yet is applied on the truss assembly, the reading should all be almost zero. If readings are not almost zero values, press the tare button on the Load Cell Amplifier until the readings are almost zero.

Figure 1.18 Readings at „almost zero” on the three load cells. 25. Press the tare button on both of the beam balance to set to zero once more before we start collecting data actually needed for the activity 1. Now we’re ready to do trials. 26. TAKE NOTE OF THE TRIALS ASSIGNED TO EACH GROUP. (see the following Tables on pages 9 and 10) 27. Data for each of the trials assigned to a particular group may be gathered from the A01 SS Truss - Demo Video 2 - Data Gathering. (pick on the link below) https://ust.ap.panopto.com/Panopto/Pages/Viewer.aspx?id=542e1d99-58c5-46ae-8c3bacc100a0011b 8

Faculty of Engineering

Physics 1 Laboratory

Trial 1, 1 kg at point C, is assigned to Groups 1 to 8. Trial 1 will serve as a SAMPLE Trial for groups 1 to 8.

Figure 1.19 Readings for Trial 1, 1kg at point C

Trials

Experimental, Values, N RA

Trial 1 1kg load at point C

0.6659 kg 0.3346 kg RF Bottom Chord Web Top Chord

6.5258 N 3.2791 N 2.99 N (T) 4.39 N (T) 6.17 N (C)

Computed Values, N

Percent Error

(TORC) (TORC) (TORC)

9

Faculty of Engineering

Physics 1 Laboratory

Table 1. (For Groups 1 and 2) Trials

Trial 1 1kg load at point C

Trial 2 0.6 kg load at point C Trial 3

RA

Experimental, Values, N

Bottom Chord Web Top Chord RA __________kg RF __________kg Bottom Chord Web Top Chord

Table 1. (For Groups 3 and 4) Trials

RA Trial 1 1kg load at point C

Trial 2 0.7 kg load at point C

Percent Error

__________kg

RF __________kg Bottom Chord Web Top Chord RA __________kg RF __________kg

0.6 1kg at C & 1kg load at E

Computed Values, N

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

Experimental, Values, N

Computed Values, N

Percent Error

__________kg

RF __________kg Bottom Chord Web Top Chord RA __________kg RF __________kg Bottom Chord Web Top Chord

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

__________kg

Trial 3

RA

0.7 kg at C & 1kg load at E

RF __________kg Bottom Chord Web Top Chord

10

Faculty of Engineering

Physics 1 Laboratory

Table 1. (For Groups 5 and 6) Trials

Trial 1 1kg load at point C

Trial 2 0.8 kg load at point C Trial 3

RA __________kg RF __________kg Bottom Chord Web Top Chord RA __________kg RF __________kg Bottom Chord Web Top Chord RA __________kg RF __________kg

0.8 kg at C & 1kg load at E

Bottom Chord Web Top Chord

Table 1. (For Groups 7 and 8) Trials

Trial 1 1kg load at point C

Trial 2 0.9 kg load at point C Trial 3 0.9 kg at C & 1kg load at E

RA

__________kg

RF

__________kg

Experimental, N (T or C)

Computational, N (T or C)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

Experimental, N (T or C)

Computational, N (T or C)

Bottom Chord Web Top Chord RA __________kg RF __________kg

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

Bottom Chord Web Top Chord RA __________kg RF __________kg

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

Bottom Chord Web Top Chord

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

(TORC)

Percent Error

Percent Error

11

Faculty of Engineering

Physics 1 Laboratory

28. For Trial 1, apply a 1kg load at point C. (Weight) . Record the kg readings displayed on beam balance under point A and point F on Table1. 29. Solve for the R A (Reaction Force at point A) in Newtons (N). Multiply the kg reading by 9.8 m/s2. The resulting value is the Reaction Force at point A in Newtons. Do the same for the Reaction Force at point F, R F. Record the values in Table 1, under Experimental, N. 30. Record the force readings, from the display of the SparkVue app interface as experimental values for the bottom chord (member EF), web (member CD) and top chord (member BD). Take note of the “signs” of the readings. If the reading is positive indicate it by placing a (C) after the value and if the value is negative, indicate it as (T). 31. Repeat step 27, 28 and 29 for Trial 2 and Trial 3 assigned to your group. Note: Data entry and computations for trial one is included on the link below, choose “A01 SS Truss Demo Video2 – Data Gathering” https://ust.ap.panopto.com/Panopto/Pages/Viewer.aspx?id=542e1d99-58c5-46ae-8c3bacc100a0011b 32. Use theory, “method of joints” to solve for the forces acting on the selected members of the truss assembly. “A01 SS Truss – Method of Joints Lecture Videos 1 and 2 are video lectures available on how to compute for axial forces acting on the joints. Pick on the following links: https://ust.ap.panopto.com/Panopto/Pages/Viewer.aspx?id=a34ee6cc-74c1-41c6-831cacc10091e85e https://ust.ap.panopto.com/Panopto/Pages/Viewer.aspx?id=32a128a1-18be-4c95-88beacc10091ec74 33. Show all computations for Trials 1, 2 and 3 in your report. Illustrate the computations with FBD, force vectors, labels etc. 34. Record the computed values under the designated column. 35. Use the SKYCIV TRUSS SIMULATION SOFTWARE to CHECK THE ACCURACY of your computations. If computation values are different from the the SkyCiv values, do a re-computation until equivalent values are attained. Follow the procedure for the SkyCiv Software. a. Click the link: https://skyciv.com/free-truss-calculator/ b. Open the settings menu (upper right) and set the Unit System to Metric, then the length to meter and for the force to Newtons (N) for the force. Save. c. Click the Nodes button on the left side. Type 0 on the X-position box and 0 on the Y-position box then press Apply. A blue dot will be displayed on your work area screen indicating the first joint of the truss. d. For the second node, enter 0.17 on the X box and 0 on the Y box. Press Apply. e. Third node enter 0.34 on the X box and 0 on the Y box. Press Apply. f. Fourth node, 0.51 for the X and 0 for the Y. Press Apply. g. Fifth node: 0.17 for X and 0.17 for Y. Press Apply. 12

Faculty of Engineering

Physics 1 Laboratory

h. Sixth node: 0.34 for X, 0.17 for Y. Press Apply. By this time, you'd already noticed that you'd plotted the points using the Cartesian plane.

i.

Click the Back button on the upper left. Then click members. Now let's connect the dots. j. For Member 1: Node A, type 1; Node B, type 2. Press Apply. k. Member 2: Node A, enter 2; Node B, enter 3. Apply. l. Now connect all the joints this way until you have come up with the given truss.

m. Press Back. Now we're going to place supports on both ends of the truss. Press Supports. Node ID: enter 1; Code: select Pin Support. Apply. n. Node ID: enter 4; Code: select Horizontal Roller. Press Apply. Press Back.

13

Faculty of Engineering

Physics 1 Laboratory

o. You're almost done. Pick Point Loads button. You are working on the first trial and that is to hang the first load at joint 2. On Node ID box enter the name of the joint, which is, 2. The load is hanging; therefore, it has no x-component but with downward force. Enter 0 for x and for Y, the negative value of the hanging weight in N. Press Apply. Now, you have the diagram of your truss with an external force.

p. Now to solve for the internal forces, forces acting on the members, click Back. q. Press the Solve tab at the lower left. Click OK. Press the Reactions button first to see the two upward forces reacting at the supports of the truss. Compare them to your answers using hand computation.

r.

Click on Axial tab to get all the internal forces. Compare these results to your answers using hand computation.

Results are blurred-out

14

Faculty of Engineering

s. t.

Physics 1 Laboratory

For the other trials press the Undo or New buttons at the upper right of the screen and follow the same procedures. Paste the pictures of the final diagrams (with all internal forces and support reactions included) of the three trials. Indicate the percent difference of the values of TC, BC, and WC between the simulated and hand computed activities below the pictures.

*Note: the Skyciv diagram considers the forces acting on the “member” (not the joints) in determining the type of internal forces. Arrowheads PRESSING against each other is compression. Arrowheads PULLING away from each other means tension. Considering Newton's 3rd law of motion (Action-Reaction), take note of the actionreaction pairs between member and joint to get the corresponding effect on the joints (refer to the figures below).

36. Compute for the percent error between the experimental values (measured values) and computed values. % Error = / EV – CV/ x 100 CV V. Supplementary Questions 1.

Discuss the difference in the experimental and computational member forces for all simulations.

2.

How can the location / placement of the external load influence the value and the nature of the member forces?

3.

Differentiate the nature of the member forces of the bottom chord, top chord, and web member. Is there a pattern?

15

Faculty of Engineering

Physics 1 Laboratory

Section____ Group No.____ Proof of Participation Photos. (indicate who’s included in the photo) Place photo showing your participation in your group

Place photo showing your participation in your group

Surname, Name

Surname, Name

Place photo showing your participation in your group

Place photo showing your participation in your group

Surname, Name

Surname, Name

Place photo showing your participation in your group

Surname, Name 16...