4. Shear Force Influence Lines.docx

LIGHT STRUCTURE LABORATORY

LABORATORY WORKSHEET

Course Code

BFC 31901

Department

Structure And Material Engineering

Tiltle

SHEAR FORCE INFLUENCE LINE

Faculty : Faculty of Civil and Environmental Engineering Page 1 Department : Structure And Material Engineering Edition

Checking No Title :Shear Force Influence Lines Effective Date

Amendment Date

1.0

OBJECTIVE 1.0 2.0

2.0

Part 1: To plot Shear force influence line. Part 2 : To verify the use of shear force influence on a simply support beam

LEARNING OUTCOME 1.0 Able to apply the engineering knowledge in practical application. 2.0 Able to enhance technical competency in structural engineering through laboratory application. 3.0 Able to communicate effectively in group. 4.0 Able to identify problem, solving finding out appropriate solution through laboratory.

3.0

INTRODUCTION 1.

Moving loads on beams are common features of design. Many road bridges are constructed from beam and as such have to be designed to carry a knife edge load or a string of wheel loads, or a uniformly distributed load, or perhaps the worst combination of all three. The method of solving the problem is to use influence lines.

4.0

THEORY Definition: shear influence line is defined as a line representing the changes in shear force at a section of a beam a unit load moves on the beam. Part1: This experiment examines how shear force varies at a cut section as a unit load moves from one end to another ( see figure 1). From the diagram, shear force influence line equation can be written.

For 0 ≤ x ≤ a shear line is given by : Sy = -x/ L…………………………….Eq(1) For a ≤ x ≤ b shear line is given by : Sy = 1-x/ L…… …………………….Eq(2)

Faculty : Faculty of Civil and Environmental Engineering Page 2 Department : Structure And Material Engineering Edition

Checking No Title : : Shear Force Influence Lines

Effective Date

Amendment Date

Figure 1

Faculty : Faculty of Civil and Environmental Engineering Page 3 Department : Structure And Material Engineering

Edition

Checking No Title : : Shear Force Influence Lines

Effective Date

Amendment Date

5.0

Part 2 : If the beam are loaded as shown figure 2, the shear force at the “ cut” can be calculated using the influence line. (See diagram 2). Shear force at ‘cut ’section = F 1Y1 + F2Y2 + F3Y3 ………………Eq(3) (Y1, Y2 and Y3 are ordinates derived from the influence line in term of X1, X2, X3, a,b and L)

6.0

APPARATUS Sketch the apparatus used in this experiment and named the essential components

Faculty : Faculty of Civil and Environmental Engineering Page 4 Department : Structure And Material Engineering Edition

Checking No

Title : Shear Force Influence Lines Effective Date

Amendment Date

7.0

PROCUDERS Part 1 1. Check the Digital Force Meter reads Zero with no load. 2. Place hanger with any mass range between 100g to 300g at the first grooved hanger support at the left support and record the Digital Force reading in Table 1. 3. Repeat the procedure to the next grooved hanger until to the last grooved hanger at the right hand support. 4. Complete the calculation in Table 1.

Part 2 1.

Place three load hangers with 100g, 200g and 300g mass respectively at any position between the supports. Record the positions and the Digital Force Display reading in Table 2. 2. Repeat the procedure with three other locations. 3. Complete the calculation in Table. 8.0

RESULT

Location of Load From left hand support(m)

Digital Force Display Reading( N)

Shear Force at cut section (N)

0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24 0.26 0.34 0.36

0.38 0.40

Faculty : Faculty of Civil and Environmental Engineering Page 5 Department : Structure And Material Engineering Edition

Checking No Title : : Shear Force Influence Lines

Experimental Influence line value

Theory Influence line value

Effective Date

Amendment Date

Notes: 1. Shear force at cut section is the same value given by Digital Force Reading. Add – ve sign to the value for positions 320mm to 380mm 2. Experimental Influence line values = Shear Force(N) Load (N) 3. Calculate the theory value using the equation 1 for load position 40 to 260mm and equation 2 for load position 320mm to 380mm Part 2: Location

Position of hanger from left hand support(m) 100g

200g

Shear force Digital Reading N

Theoretical Shear Nm

300g

1 2 3 4 5 Notes: Theoretical Shear Force is calculated using Equation. 9.0

DISCUSSIONS

1. Derive equation 1 and 2 2. On the same graph paper, plot the theoretical and experimental values against distance from left hand support 3. Comment on the shape of the graph. What does it tell about how shear force varies at the cut section as a load moved on the beam? 4. Comment on the experimental result and compared to the theoretical result. 5. Comment the experimental result and theoretical result in table 6. Conclusions: What can you prove from the experiment Part 1 and Part 2.