DEPARTMENT OF STRUCTURE AND MATERIALENGINEERINGFACULTY OF CIVIL & ENVIRONMENTAL ENGINEERING UTHM

HYDRAULIC AND MECHANIC OF MATERIAL LABBFC21201

NAME OF GROUP MEMBER:

MUHAMMAD ZARIF SYAZWAN BIN SUHAINICF140108MOHAMMAD HAMIZAN BIN MOHD AZMANCF140096MOHD SHAHIWAN BIN HALIMCF140100MOHAMAD IZZAT BIN MOHD RAMLICF140209BASHEER AL-NAJM AL-QARHAF130200

TITLE : BUCKLING OF STRUTS

LECTURER NAME :

DATE OF SUBMISSION : 15TH MARCH 2015

MARK ACHIEVE :

1.0 OBJECTIVE

1.1To examine how shear force varies with an increasing point load.1.2To examine how shear force varies at the cut position of the beam for various loading condition.

2.0 LEARNING OUTCOME

2.1The application the engineering knowledge in practical application.

2.2To enhance technical competency in structural engineering through laboratory application.

2.3To communicate effectively in group.

2.4To identify problem, solving and finding out appropriate solution through laboratory application.

3.0 INTRODUCTION

3.1A compressive member can fail in two ways. The first is via rupture due to the direct stress and the second is by an elastic mode of failure called buckling. Short wide compressive member tends to fail by material crushing.

3.2When buckling occurs the struts will no longer carry any more load and its will simply continue to buckle i.e its stiffness then becomes zero and it is useless as a structural member.

4.0 THEORY

4.1To predict the buckling load Euler buckling formula is used. The critical value in Euler Formula is the slenderness ration, which is the ratio of the length of the struts to its radius of gyration (L/K)

4.2The Euler formula become inaccurate for struts with L/K ratio of less than 1.125 and this should taken into account in any design work.

4.3Euler buckling formula pin struts :

5.0 APPARATUS

Figure 1 : Type of connection end

Figure 2: BucklingofStrutEquipment Figure 3: Pin End

Figure 4: Fixed End 6.0 PROCEDURE

Part 1

1). Fit the bottom chuck to the machine and remove the top chuck (to give two pinned ends).Select the shortest strut, number 1, and measured the cross section using the vernierprovided and calculated the second moment of area, I,for the strut ( bd3/12)

2). Adjust the position of the sliding crosshead to accept the strut using the thumbnut to lockoff the slider. Ensure that there is the maximum amount of travel available on the handwheel threat to compress the strut. Finally tighten the locking screw

3) Carefully back- off the handwheel so that the strut is resting in the notch but nottransmitting any load. Rezero the forcemeter using thefront panel control.

4) Carefully start to load the strut. If the strut begin to buckle tothe left,flick the strut t othe right and vice versa (this reduces any error associated wih the straightness of strut).Turn the hand wheel until there isno further increase in load (the load may peak and thendrop as it settles in the notches).

5). Record the final load in Table 1. Repeat with strut numbers 2, 3, 4 and 5 adjusting thecrosshead as required to fit the strut.

Part 2

1). To study the effect of end conditions, follow the same basic procedure as in part 1, butthis time remove the bottom chuck and clamp the specimen using the cap head screw andplate to make a pinned-fixed end condition.

2.) Record your result in Table 2 and calculate the values of 1/ L2for the struts.

3). Fit the top chuck with the two cap head screws and clamp both ends of the specimen tomake a pinnedpinned end condition. Calculate the new values of

4.) Enter the result into Table 3

Figure 5 : PIN-PIN END

Figure 6 : PIN-FIXED END

Figure 7: FIXED-FIXED END7.0 RESULT

STRUT NUMBERLENGTH (mm)BUCKLING LOAD (N)EXPERIMENTBUCKLING LOAD (N)THEORY

1320-19888.4505

2370-13966.1600

3420-11651.3454

4470-8141.0020

5520-3633.4961

TABLE 1 : RESULT FOR STRUT PIN TO PIN

STRUT NUMBERLENGTH(mm)BUCKLING LOAD (N)EXPERIMENTBUCKLING LOAD (N)THEORY1/

1300-166201.274111.11

2350-132144.53938.16

3400-100113.2176.25

4450-07884.25524.94

5500-05672.45874.00

TABLE 2 : RESULT FOR STRUT PIN TO FIX

STRUT NUMBERLENGTH(mm)BUCKLING LOAD(N)EXPERIMENTBUCKLING LOAD(N)THEORY1/

1280-400462.109012.76

2330-270332.68459.18

3380-181250.89576.93

4430-164195.94025.41

5480-143157.24544.34

TABLE 3 : RESULT FOR FIX TO FIX

8.0 CALCULATION

I = b/12

b = 0.02md = 0.002mI = 0.02 X /12 = 1.33 X

E = 69 GN @ 69 X

Pin to Pin

STRUT 1

L = 320 mm 0.32 m

Pe = (69 X ) (1.33 X ) / ( = 88.4505 N

STRUT 2

L = 370 mm 0.37 m

Pe = (69 X ) (1.33 X ) / ( = 66.16 N

STRUT 3

L = 420 mm 0.42 m

Pe = (69 X ) (1.33 X ) / ( = 51.3454 N

STRUT 4

L = 470 mm 0.47 m

Pe = (69 X ) (1.33 X ) / ( = 41.002 N

STRUT 5

L = 520 mm 0.52 m

Pe = (69 X ) (1.33 X ) / ( = 33.6961 N

Fix to pin

STRUT 1

L = 300 mm 0.30 mPe = (69 X ) (1.33 X ) / ( = 201.2741 N

STRUT 2

L = 350 mm 0.35 m

Pe = (69 X ) (1.33 X ) / ( = 144.5393 N

STRUT 3

L = 400 mm 0.40 m

Pe = (69 X ) (1.33 X ) / ( = 113.217 N

STRUT 4

L = 450 mm 0.45 m

Pe = (69 X ) (1.33 X ) / ( = 89.4552 N

STRUT 5

L = 500 mm 0.50 m

Pe = (69 X ) (1.33 X ) / ( = 72.4587 N

Fixed to Fixed

STRUT 1

L = 280 mm 0.28 m

Pe = (69 X ) (1.33 X ) / ( = 462.109 N

STRUT 2

L = 330 mm 0.33 m

Pe = (69 X ) (1.33 X ) / ( = 332.6845 N

STRUT 3

L = 380 mm 0.38 m

Pe = (69 X ) (1.33 X ) / ( = 250.8957 N

STRUT 4

L = 430 mm 0.43 m

Pe = (69 X ) (1.33 X ) / ( = 195.9402 N

STRUT 5

L = 480 mm 0.48 m

Pe = (69 X ) (1.33 X ) / ( = 157.9402 N

9.0 DISCUSSIONPart 1:

1) Examine the Euler buckling equation and select an appropriate parameter to establish a linear relationship between the buckling load and the length of the strut. Write the relationship below.

Based Eular formula and Table 1, 2 and 3,Pe =Eulerbucklingload(N), L=length

We can consider that when L is bigger, Pe will be small, relation between bucklingload and the length of the strutis inversely proportionalin linear condition.

2) Calculate the value and enter them in Table 1 with an appropriate title. Show on Table 1 using formula:

3) Plot a graph to prove therelationship is linear. Compare your experimental value to those calculated from Euler formula by entering a theoretical lineonto the graph. Comment on the result.

Graph plotted = In the graph paper

Based on the graft that we plotted, for pin-pin -end , the gradient for experiment value is 0.58N and the gradient of the theoretical value is 0.25N . For pin-fixed- end the the gradient for experiment value is 0.54N and the gradient for theoretical value is 0.55N . And for the fixed-fixed end , the gradient of experiment value is 1.06N and the gradient of theoretical value is 1.367N. This experiment result shows that for pin-pin-end, the gradient of experiment value is greater than the theoretical value. Meanwhile ,the result for fixed-pin-end, the gradient of theoretical value is greater than experiment value and for fixed-fixed-end the result shows that the theoretical value is greater than experiment value. So in practice, The buckling of the theoretical value is higher than experiment value for pin-fixed-end and fixed-fixed-end except for pin-pin-end, which the buckling of experiment value is higher than theoretical value

Part 2:

1) Plot separate graphs of buckling load versus 1/ L and calculate the gradient of each line.

Graph Plotted = In Graph Paper.Gradient in the graph plotted

2) Fill the table below showing the comparison between experimental and theoretical ratioby end condition

Pinned - PinnedPinned - FixedFixed Fixed

Experiment gradient0.580.541.06

Experiment ratio0.58/0.58=10.54/0.58=0.9311.06/0.58= 1.828

Theoretical ratio0.25/0.25=10.85/0.25=3.41,367/0.25=5.468

Notes:1. *Use the experimental gradient fomPart 12. Experimental ratio = Exp. Gradient / gradient of pinned-pinned.3. Theoretical ratio can be obtained from Euler Formula for pinned-fixed and fixed-fixed.

3. Comment on the experimental and theoretical ratio.

Fromthetable,experimentalratioisnotconsistencewiththeusageofendofconnection,we basically know that the fixed end is much stronger than the pins end referred to theoretical ratio value. This shows the more force shouldbe imposed on themembers of the joint fixed-fixed end compared to the pin-pin connection. When one of the end is changed from pin end to fix end, the ratio is two times larger than the pinned-pinned, itthe same case happed when both of the end changed to Fixed-fixed end. The experimentalratio is not consistence with theoretical ratio because there was several errors when conduct the experiment, such as the screw is not tightens carefully, the sliding crossheadare not tighten to the experiment apparatus.

4. What conclusion can you made from the experiments.

Based from the experiment of Buckling of Strut, we can concludethat Fixed end is much stronger than the Pinned end and more force should be imposed on the member ofthe joint fixed-fixed end connection, but in other criteria the usage in fixed endconnection usually apply for concrete beam or column connection, The Pinned end issued for Steel connection because, usually fixed end connection is for permanentconnection, steel always use bolt and nut rather than weld fabricating connection.

10.0 CONCLUSION

Based from the experiment of Buckling of Strut, we can conclude that Fixed end were much strongerthan thePinned endandmore force shouldbe imposedon themember ofthejointfixed-fixedendconnection,butinothercriteria theusageinfixedendconnectionusually apply for concrete beam or column connection. The Pinned end is used for Steel connectionbecause, it isusually fixed end connection is for permanent connection..