Construction Materials American University of Ras Al Khaimah

1. Construction of Materials
Eng. Madiha Alammari
Tensile Strength of Steel Rods
Batool Alshamali/2013001217/#10

2. 1) Introduction:
The chief characteristics that determine the character of bar reinforcement are its yield
point and its modulus of elasticity. The latter is the same for all reinforcing steels.
The shape of the stress-strain curve, particularly its initial portion, has significant influence on the
performance of reinforced concrete members.
Low carbon steel generally exhibits a very linear stress-strain relationship up to a well-defined
yield point. The linear portion of the curve is the elastic region and the slope is the modulus of
elasticity or young’s Modulus. After the yield point. The curve typically decreases slightly . As
deformation continues, the stress increases on account of strain hardening until it reaches the
ultimate tensile stress. Until this point, the cross-sectional area decreases uniformly and randomly
because of Poisson contractions.
However, beyond this point a neck forms where the local cross-sectional area becomes
significantly smaller than the original. The ratio of the tensile force to the true cross-sectional area
at the narrowest region of the neck is called the true stress. The ratio of the tensile force to the
original cross-sectional area is called the engineering stress. If the stress-strain curve is plotted in
terms of true stress and true strain the stress will continue to rise until failure. Eventually the neck
becomes unstable and the specimen fractures.
2) Standard:

3. ASTM A615/A615M
3) Apparatus:
1. Universal testing machine (UTM).
2. Steel bar with length 800 mm.
4) Procedure:
1. Specify the diameter of the testing reinforcing steelrod.
2. Measure the weight of the bar.
3. The tension test specimen shall be gage marked with a center punch of 40cm gage length near
the middle of the specimen .This gage is then divided into 5 equal segments. The purpose of the
gage mark is to provide reference points for determinations of the percent of elongation. Punch
marks shall be light, sharp, and accurately spaced.
4. Select the proper jaw inserts and complete the upper and lower chuck assemblies.
5. Apply some graphite grease to the tapered surface of the grip for the smooth motion. Then ,
operate the upper cross-head grip operation handle and grip fully the upper end of the test piece.
6. The left valve is kept in fully closed position and the right valve in normal open position. Open
the right valve and close it after the lower table is slightly lifted. Now adjust the load to zero by
TARE push button. (this is necessary to remove the dead weight of the lower table, upper cross
head and other connecting parts from the load.)
7. Operate the lower grip operation handle and lift the lower cross head up and grip fully the
lower part of the specimen. Then lock the jaws in this position by operating the jaws locking hand
wheel. Then turn the right control valve slowly to open the position (i.e. anticlock wise) until you
get a desired loading rate.
8. After this you will find that the specimen is under load and then unclamp the locking handle.
Now the jaws will not slide down due to their own weight. Then go on increasing the load. When
the test piece is broken, close the right control valve, and take out the broken test piece. Then
open the left control valve to task the piston down.
9. Elongation- To determine the percentage of elongation fit the ends of the fractured specimen
together carefully and measure the distance between the gage marks to the nearest 1/8’’ (0.32cm).
The elongation is the increase in length of the gage length, expressed as a percentage of the
original gage length. In reporting elongation values, give both the percentage increase and the
original gage length.

4. Conclusion
The difference between the steel and the concrete is that the concrete is a brittle
material which gives us no indication that it will fail, but steel gives us indications and
that what we saw in this experiment.