# Civil lab Essay Example

Civil engineering lab report

Introduction

The lab report is comprised of a series of experiments which includes Equilibrium of forces test, deflection of beams, concrete mix and casting design, Hardened concrete testing and steel and timber testing (Roth 7).

Experiment 1: Equilibrium of forces test

The test aims at establishing the equilibrium position of a metal plate attached to a board using different loads.

Method used and results

One cord ring was attached to a board through the use of several strings hooked to four pulleys located at the corner of the plate. The weight was acting on the strings leading to tension. The resultant force and their vertical components were then determined using two cords attached to the ring.

i). Single string attached to 3 forces

 Angle with horizontal (x-axes)

To test the equilibrium, the following calculation was carried out.

1.5cos54º+0.5cos76º=1.5cos48º

1.003=1.003

ii). Single string attached to 6 forces

 Vertical forces component (y-axes) 1.5sin42º 1.5cos48º 1.5cos38º 1.5sin77º 1.5cos13º 1.5sin52

To test the equilibrium, the following calculation was carried out.

1.5sin42º+1.5sin52º+1.5sin77º=1.5cos48º+1.5cos38º+1.5cos13º

3.6N=3.6N

Conclusion

The errors were within the acceptable limits and the main sources included aspects of friction and apparatus imprecision.

Experiment 2: Deflection of beams

To measure beam materials deflect to determine Young’s Modulus using displacements from prescribed loads.

• The displacement gauges were zeroed while the micrometer was used to find the cross-section of the beams.

• 1) measured.A beam measuring 1 meter long was loaded on two symmetrical points with the vertical displacement at midspan (δ

• A gradual increase in the load was carried out with the bending of the beam noted.

• The position of the load was changed and Young’s Modulus (E) calculated through the greatest load scenario.

Results and calculations

 Thickness of Beam

Calculations

The weight of the hooks was calculated to Newtons using the following calculation:

### = 1.01 Nm-2

The second moment of area (I) was calculated using the following:

3I = (1/12) bh

b= Width of the beam

h= Height of the beam

I=

-101.57955962*10
=

Radius was calculated using the following

R =

Young’s Modulus was calculated using the following equation

E =

Young’s Modulus (E) =

GPa11= 1.48 x 10

Conclusion

The value of Young’s Module was found to be equal to 148 GPa. This value is high but expected of such type of materials. The use of old displacement gauges may have contributed to the errors. Tapping of the gauges was carried out to minimize the errors.

Experiment 3: Concrete mix and casting

To design a concrete mix to facilitate workability test on wet concrete and prepare samples that will be used in experiment 4.

• was prepared.A concrete mixture of volume

• 2 a 28 day cube strength used was 30 N/mm2To satisfy a strength of 24N/mm

• The ratio of water to cement was 0.6 and excess water was avoided.

Results and calculations

The following calculation was used for obtaining the values of mass concrete:

Mass of Concrete (M) = M (Cement) + M (Water) + M (Aggregate)

M= C + 0.6C + 5C

Where C is the mass of cement

Calculation

Mass= Density x Volume

3Density of mixed concrete = 2300 kg/m

Mass = 6.6C

Volume =0.035m3

6.6C =2300 X 0.035

C =

=12.197 Kg

Volume of materials

M (Cement) = 9kg

M (Water) = 5 kg

M (Aggregate) = 65 kg (Fine aggregate 22.7kg, Course aggregate 42.3kg)

Machine mixing was used and about 1.6 kg of water was not used in the mixture.

Slump test

• The concrete was placed on a cone shaped mould in three stages and it was hit for the count of 20 with a cylindrical shape object.

• The cone was removed slowly when the three layers were added and the height measured.

• A height of about 74 mm was achieved, in theory, the greater the slump, the more workable the concrete.

Compact factor test

• The sample is placed on the upper hopper of the brim and the trap door opened for the concrete to fall at the lower hopper.

• The trap door for the lower hopper is opened and concrete allowed to fall into the cylinder.

• Plane blade is used to cut off excess concrete at the top level of the cylinder.

• Concrete in the cylinder is weighed and this is recorder as partially compacted concrete.

• Weight of fully compacted concrete is obtained by filling the cylinder with fresh sample and compacting it (Bartos, 2013).

Calculations

CF =

Mass of partially compacted concrete (M1) =16.8 Kg

Mass of fully compacted concrete (M2) = 17.4 Kg

Mass of Cylinder (Mc) = 6.2 Kg

CF =

`=

Conclusion

. Systematic approach is also required to achieve even compaction. Bartos, 2013) In conclusion, the results indicate that the mix design was correctly undertaken as the concrete performed well in the workability tests. The values obtained in the slump test and compaction factor test was within the range. The result however indicates that too much water was added as the values were above the medium range which was required. The sources of error could be the use of incorrect amount of materials and poor compaction. The errors can be corrected by adding small amounts of water gradually during the mixing process (

Experiment 4: Hardened concrete testing

To determine tensile and compressive strength by testing cube, cylinder and beam samples. Stiffness will also be determined and 2 cubes 2 cylinders and 1 beam was placed and left to dry for 7 days.

Methods and results

Direct compression test

This test was for measuring the concrete strength. A 150 mm cube was loaded to failure and loads applied gradually with the use of compression testing machine. This was also done on a 150 mm diameter cylinder. The following results were obtained:

 (N) Force )2(m Area Stress(Pa) Stress(MPa) 33333333 Cylinder 30337087

Comparison of the data indicates that the compressive stress value is higher in the cube as compared to the cylinder which also leads to higher compressive strength. The ability to resist crushing is higher in the cube as compared to the cylinder.

Splitting test

• A steel packer with knife edge loads was used to split the cubes and the loads recorded.

The following data was used:

Load to cause splitting (P) = 10.1 KN

Side length of the cube (d) = 0.150 m

Width along the packer (w) = 0.0125 m

The results indicated that concrete has higher compressive strength than tensile strength.

Static stiffness measurement

• Metal studs and the cylinder were placed in four quadrants and loaded with compression testing machine.

The following results were obtained:

Bending test

• Concrete beam was loaded to two supports and load applied at the center with compression testing machine.

• Euler- Bernoulli beam theory was used to calculate tensile strength.

• Load obtained at failure equaled 12.7 KN.

The following calculations were used

Distance from applied load to support (a)

Dimensions of cross-sectional areas of the beam (b and h)

=

= 11.2 Mpa

Experiment 5: Steel and Timber testing

To determine the behavior of timber and steel under failure and also the tensile strength and ductility of steel

Steel testing method

• Dartec steel testing machine was used.

• Steel subjected to different heat treatment were used.

• Compression is done until the sample breaks.

Results and graphs

Normal steel Radius (R1) = 4.995 mm

Annealed steel Radius (R2) = 4.98 mm

Young’s Modulus =

The following results were obtained

 StrengthTensile ModulusYoung’s failureElongation at 0.881KNm 110.75GPa Annealed 0.629KNm 118.70GPa

Timber testing

.Virdi, Garas, Clarke, Clarke, and Armer 22). Two timber specimens were used with one being loaded axially with respect to timber fibers and the other loaded in traverse direction to the fibers (

The result were presented in the following graphs

Works Cited

NY: Elsevier, 2013.Fresh Concrete: Properties and tests.Bartos, P.

2007.. NY: Human Kinetics, Genetics Primer for Exercise Science and HealthRoth, M. S.

. London: CRC Press, 1998.Structural Assessment: The Role of Large and Full-Scale TestingVirdi, K.S., Garas, F.K., Clarke, Clarke, J.L., Armer, G.S.T.