1. A reinforced concrete beam was tested under static two-point concentrated loading to study the effect of different web reinforcement arrangements on ultimate shear strength. 2. It was observed that diagonal cracks developed first in deeper beams while flexural cracks developed first in shallower beams with sufficient reinforcement. 3. The crack pattern and failure mode were similar across all test beams despite variations in web reinforcement, with diagonal cracks forming first in deeper beams.

1. GAZIANTEP UNIVERSITY
GRADUATE SCHOOL NATURAL AND APPLIED SCEINCE
DEPARTMENT OF CIVIL ENGINEERING
M.SC IN CONSTRUCTION ENGINEERING
CE545 : DEFORMATION AND FRACTURE THEORIES
STUDY No: 5
The Crack Pattern Of R.C Beams Under Loading
Submitted by
AHMED ASSIM ABDULLAH
STD No: 201444960

2. The loading conditions can be categorized with respect to the ratio of
load duration (to) to characteristic response time (T) as proposed in
Table
At high rates of loading the response of structures is affected by
propagation of stress waves and motion-generated inertia forces.
The dynamic response of a structure to impact loading can be
analysed in terms of a local (primary) response in the direct vicinity
of the applied load and of an overall (secondary) response of a
structural member or the entire structure .

3. The behaviour of a system consisting of the structure and an
impacting body depends on their masses and rigidities, sizes and
shapes of contact surfaces, initial velocities, stiffness of structural
members and supporting conditions , among other factors .

4. The local response of concrete structures involves crushing, punching
shear, spalling and scabbing of concrete. In the case of hard missile
impact significant penetration and even perforation of concrete
members may occur. These phenomena are governed by stress wave
propagation and behaviour of sound and cracked concrete under
multiaxial, high rate loading conditions. Due to the complex nature of
the local response of concrete structures reliable and economical
analysis, so that empirical formulae often have to be used in design
procedures. Several formulae and results of hard missile impact tests
are reviewed by Hughes , The following formulae for the penetration
depth x^ and for the barrier thicknesses h and h preventing scabbing
and perforation respectively :

5. Concrete Under Tension :
The beam was tested under two- points concentrated load by ? kips capacity
universal testing machine (hydraulic type). The load was applied on the top
surface. long steel plate and the reactions were supported. long steel plates
placed at the bottom of the beams. One of the reaction plate rested on a steel
block and itself placed on the anvil of the testing machine. The other reaction
plate was placed over a steel block supported by 5/8-in. diameter steel rollers.
I-joists with rollers and rubber pads were employed as load transfer devices for
two series of beams. The support lines were clearly marked on both sides of
the beams. The loading blocks were also marked on both sides at their centers.
A deflectometer graduated in 0.001 in . division was used to measure the mid
span deflections of test beams at each load increment. The beam was then
loaded and deflection readings were taken at regular interval of load
increment. Test beams were white washed to facilitate visual observation of
the propagation of cracks on the surface of beam . Cracks were deeply marked
with a soft pencil upon their formation on the beam surface and the load
intenSity at which it was formed was noted besides the crack. One of the
cylinders cast along with each of the test beam was tested under axial
compression to determine the ultimate compressive strength of concrete and
the other was tested under diametrical compression to find the split cylinder
tensile strength.

6. A reinforced concrete beam have been tested under static two point
concentrated loading system. The special interest of the investigation is to
study the effect of different web reinforcement arrangement on the ultimate
shear strength of brick aggregate concrete beams under two series and as a
whole the overall behavior of deep beams under two point concentrated
loading. The specific observation of interest during the test has been recorded
and is being presented in this chapter. The critical load at tension cracking , the
load at flexure cracking , the ultimate load and deflections under different load
intensities are noted in a systematic manner during the test. For an easy grasp
of the overall performance of the beams, the test results are presented here in
a tabular form. a general description of the contents of the different tables
containing various test data seems necessary and is furnished below. the
typical beam properties of all the beams have been provided. This includes the
actual overall depth , beam width, span to effective depth ratio, web steel ratio
(both for vertical and horizontal web steel), cylinder crushing strength and split
cylinder strength. The different steel ratios are computed on the basis of actual
area of steel provided and mean of the measured width and effective depth
after casting. Some of the basic properties of brick aggregate concrete like,
compressive strength , split cylinder strength and the relation between them is
given by Brazilian ratio and the unit weight of harden concrete is computed by
dividing the weight of standard cylinder by its volume.
Mode of Failure and Crack Pattern
The crack pattern and the mode of failure of all the test beams were almost
similar despite the variations in web reinforcement arrangement. From the
test it was observed that diagonal cracks develop first in relatively deeper
beams and flexural cracks develop first in shallower beams provided the beams
have sufficient reinforcement. The crack pattern of beam A2 is shown below:

7. Failure at Macro-Scale
Although the stress-displacement curves give an indication of the failure
mechanisms, to fully understand the rate dependency of the dynamic failure
behaviour of concrete it is necessary to study the crack patterns in detail.
Therefore, after the dynamic experiments are finished, the specimens are
impregnated with a fluorescent epoxy. After impregnation, the specimens
were sawn in half to be able to study the macro-crack patterns.
From Figures can be concluded that the macro-crack patterns of the static and
the SHB tests are not that different, although the static cracks seem to be a
little more whimsical. In both cases, almost no fractured aggregates were
detected and most of the aggregate particles were pulled out of the cement
paste. The particles that were fractured had a low density and probably had a
lower strength than the cement paste. The few fractured particles were
observed both in the static tests and the SHB tests.
ved both in the static tests and the SHB tests. The macro-crack patterns of the
MSHB tests differ per test. Sometimes the width of the zone with macro-cracks
seems to be very small and other times the width is larger and the cracks are
more whimsical (Figs. Above ) The characteristics of the macro-crack
correspond with the shape of the stressdisplacement curves; when the peaks
of the curves are wider, which indicates multiple fractures, the width of the

8. zone with macro-cracks seems to increase. A comparison between the macro-
crack patterns of the static and SHB tests and the crack patterns of the MSHB
tests is difficult, since the characteristics of the macro-crack in the MSHB tests
are not always the same. One major difference can be observed; the amount
of fractured aggregate particles. In the MSHB tests more aggregates are
fractured, than in the other two loading conditions. However, the cracks not
always run through the aggregate particles but also move around them,
searching for the weakest part of the cement paste close to the particles; the
interfacial transition zone (ITZ).