2. Prof. Dr. Mustafa B. Dawood and Reem Abd-Alraheem Nabbat
http://www.iaeme.com/IJCIET/index.asp 94 editor@iaeme.com
Cite this Article: Prof. Dr. Dawood, M. B. and Nabbat, R. A.-A. Flexural and
Shear Strength of Non-Prismatic Reinforced High Strength Concrete Beams
with Openings and Strengthened with NSM-CFPR Bars. International Journal
of Civil Engineering and Technology, 6(9), 2015, pp. 93-103.
http://www.iaeme.com/IJCIET/issues.asp?JTypeIJCIET&VType=6&IType=9
1. INTRODUCTION
Non prismatic beams have been used in various structures including buildings and
bridges since the first decades of the previous century, with an increasing application
as the structural engineering techniques were improved. With the beams being
tapered, the architects would be able to create and implement novel aesthetic
architectural designations, as well as the structural engineers who could seek for
optimum low weight - high strength systems through a redistribution of materials
along the structural members [1].
There is a large need for strengthening of concrete structures all around the world
and there can be many reasons for found strengthening, increased loads, design and
construction faults, change of structural system, and so on. The need exists for
strengthening in flexure as well as in shear. Epoxy plate bonding with Carbon Fiber
Reinforced Polymers, CFRP has been shown to be a competitive method for
strengthening of existing structures and increasing the load carrying capacity
The presence of web openings in such beam is frequently required reduce the
element shear capacity to provide accessibility such as doors and windows, or to
accommodate essential services such as ventilating, pipes and air conditioning ducts.
Enlargement of such openings due to architectural, mechanical requirements or
change in the building functions would reduce the element shear capacity [2].
2. EXPERIMENTAL PROGRAM
The experimental study consisted of two test groups. First group was designed to fail
in flexural and the second group designed to fail in shear.
The first group included six beams with and without openings. The beams has total
length (L) of 1500 mm ,the clear span (Ln) is 1350 mm ,the height at the mid span (H1) is
155 mm ,while the height at support (H2) is 220 mm and the width (b) is 150 mm. The
flexure reinforcement of beams consisted of 2Ф12 mm tension bars at bottom, and 2Ф10
mm at top. To avoid shear failure, the beams were reinforced for shear with Ф6 mm
closed stirrups spaced at 70 mm C/C as shown in Figure 1 show control beam F1.
Figure 1 Details of Tested Beams
3. Flexural and Shear Strength of Non-Prismatic Reinforced High Strength Concrete Beams
with Openings and Strengthened with NSM-CFPR Bars
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The second beam is (F2) same to F1 but strengthen with carbon bar in tension
zone grooved at bottom face as shown in Figure 2.
Figure 2 Section and Bottom view of (F2)
The third beam (F3-O1) has two openings in the shear zone with dimension
(150*70) mm. The location of its openings were (275) mm from the edge of the beam
to the center of the openings as shown in Figure 3.
Figure 3 Section of Beam (F3-O1)
The fourth beam (F4-O1-S) is same to (F3-O1) but strengthen with carbon sheet
in bottom face as shown in Figure 4.
Figure 4 Bottom view of (F4-O1-S)
The fifth beam (F5-O2) has two openings in shear zone with dimension (150*70)
mm. The location of openings were (350) mm from the edge of beam to the center of
opening as shown in Figure 5.
Figure 5 Section of Beam (F5-O2)
The sixth beam (F6-O2-S) is same to (F5-O2) but strengthen with carbon sheet in
the tension zone at bottom face; also the openings were strengthened with CFRP as
shown in Figure 6.
Carbon Sheet
4. Prof. Dr. Mustafa B. Dawood and Reem Abd-Alraheem Nabbat
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Figure 6 Section of Beam (F6-O2-S)
The second group included six beams with and without openings. The beam has a
total length (L) of 1500 mm, the clear span (Ln) is 1350 mm, the height at the mid
span (H1) is 240 mm, the height at the supports (H2) is 140 mm and the width (b) is
150 mm. The flexure reinforcement of beams consisted of 3Ф12 mm bars at bottom,
and 2Ф10 mm at top, the beams were reinforced for shear resistance with Ф4 mm
closed stirrups spaced at 55 mm C/C as shown in Figure 7.
Figure 7 Section of Control beam (S1)
The second beam (S2) is same to (S1) but strengthen in shear zone with inclined
carbon bar with angle (45°) and space between bars are (55)mm as shown in Figure 8.
Figure 8 Section of beam (S2)
The third beam (S3-O1) has one opening in flexure zone with dimensions
(150*80) mm. The location of opening is at the center of the beam as shown in Figure
9.
Carbon bar
Carbon Sheet
5. Flexural and Shear Strength of Non-Prismatic Reinforced High Strength Concrete Beams
with Openings and Strengthened with NSM-CFPR Bars
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Figure 9 Section of beam (S3-O1)
The fourth beam (S4-O1-S) is same to (S3-O1) but strengthen with carbon bar in
the shear zone and the opening was strengthened with CFRP as shown in Figure 10.
Figure 10 Section of beam (S4-O1-S)
The fifth beam (S5-O2) has one opening in flexure zone with a dimension
(150*80) mm. The location of the opening is (100) mm from the top of beam to the
center of opening as shown in Figure 11.
Figure 11 Section of beam (S5-O2)
The sixth beam (S6-O2-S) is same to (S5-O2) but strengthen with carbon bar as
shown in Figure 12.
Figure 12 Section of beam (S6-O2-S)
Carbon Sheet
Carbon Bar
Carbon Sheet Carbon Bar
6. Prof. Dr. Mustafa B. Dawood and Reem Abd-Alraheem Nabbat
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3. MATERIALS
In the experimental program, (ф4, 6, 10, 12 mm) hot-rolled, deformed, mild steel bars
are employed as tension reinforcement for both, flexure and shear beams. Modified
Portland cement (Type I) from Iraq plant named Kubaise. Crushed gravel from Al-
Nibaey region with maximum size of (14 mm). Natural sand from Al-Akhaidher
region in Iraq with maximum size of (4.75 mm) and fineness modulus of (2.501).
High-range water-reducer superplasticizer (Viscocrete) [3].
Table 1 Concrete Mix
High strength concreteParameter
0.28Water/cement ratio
140Water (kg/ )
500Cement (kg/ )
625Fine aggregate(kg/ )
1065Coarse aggregate(kg/ )
5*Superplasticizer (L / )
50Silica fume (kg/ )
1 litter /100 kg cement
4. TEST MEASUREMENT AND INSTRUMENTATION
A hydraulic universal test machine (MFL system) was used to test the beam
specimens. The deflections were measured by means of (0.01 mm) accuracy dial
gauge (ELE type) and (50 mm) capacity. Strain of concrete measured used demic
point and dial gauge (ELE type) with accuracy of (0.002 mm) and (10 mm) capacity.
5. TEST PROCEDURE
Tests were carried out by using universal testing machine with capacity of 2000 kN.
The universal testing machine is a closed loop servo hydraulic testing system
controlled manually, the heart of the universal testing machine is a custom installed 4
m high frame, this frame has a high degree of stiffness and can be modified to
accommodate different configurations of beams as well as other structural elements.
The experiments were executed in load control with manually data monitoring. All of
the non-prismatic beams were statically tested to fail in one loading cycle. The
supports, as well as the loading point measured 100 mm in width. The load was
slowly applied, in a load-control manner at a rate of 0.5 kN/s, in successive
increments up to failure. The applied load increment was initially 5 kN which was
then increased to 10 kN intervals until specimen failure. At each increment, the load
was held constant so that deflection and mechanical strain gauge reading could be
taken. After the readings were taken, the test beam was inspected for any new or
extended cracks. These observations were recorded on the beam using felt tipped
markers. Once the readings and observations were taken, the loading was then
increased by the next increment and the procedure was repeated. Test was terminated
at the onset of one of the following;
Substantial drop in the value of the total applied load.
Excessive deformations and cracks widening under the same load level.
Concrete crushing.
7. Flexural and Shear Strength of Non-Prismatic Reinforced High Strength Concrete Beams
with Openings and Strengthened with NSM-CFPR Bars
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6. EXPERIMENTAL RESULTS
6.1. Flexural Beams Results
The test results of this group including (ultimate and cracking loads) are given in
Table 2.
Table 2 Ultimate and Cracking Loads of flexural behavior of Tested Beams
6.1.1. Deflections of flexure beam
Load-deflection curves of the tested beams at mid span at all stages of loading up to
failure were constructed and shown in Figures (13).
Figure 13 Load-deflection curves of the tested beams at mid span
8. Prof. Dr. Mustafa B. Dawood and Reem Abd-Alraheem Nabbat
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Figure 14 Crack Pattern of Flexural Beams
6.2. Shear Beams Results
All beams of this group were designed to fail in shear. Photographs of the tested
beams are shown in Figure (15). The test results of this group including (ultimate and
cracking loads) are given in Table 3.
9. Flexural and Shear Strength of Non-Prismatic Reinforced High Strength Concrete Beams
with Openings and Strengthened with NSM-CFPR Bars
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Table 3 Ultimate and Cracking Loads of shear behavior of Tested Beams
6.2.1. Deflections of shearbeam
Load-deflection curves of the tested beams at mid span at all stages of loading up to
failure were constructed and shown in Figures (16).
Figure 15 Crack Pattern of Shear Beams
10. Prof. Dr. Mustafa B. Dawood and Reem Abd-Alraheem Nabbat
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Figure 16 Load-deflection curve
7. CONCLUSIONS
The presence of openings in the non-prismatic beams near interior support decreases
the ultimate load by about (12.56%), while the beams have openings near interior
point load decreases the ultimate load about (59.44%) when compared with beam
without openings.
The CFRP sheet technique gives a better performance in comparison with near
surface mounted (NSM) in Flexure beams
The presence of opening in the non-prismatic beam located at mid span over
neutral axis decreases the ultimate load about (10.75%) and (2.84%) for beam with
opening in neutral axis, when compared with beam without openings.
The strengthening by CFRP, decreases the crack width and increases number of
cracks, this is one of the several advantages of using the CFRP.
The first cracking load obtained from numerical data show results lower than the
experimental data recorded with a difference about (10.78%) as an average of Flexure
beams and (4.86%) as an average of Shear beams
11. Flexural and Shear Strength of Non-Prismatic Reinforced High Strength Concrete Beams
with Openings and Strengthened with NSM-CFPR Bars
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The cracking patterns at the final loads of the finite element models compared
well with the observed failure modes of the experimental tested beams.
REFERENCES
[1] ACI Committee-363. State of the Art Report on High Strength Concrete (ACI
363R-92). American Concrete Institute, Detroit, 1997.
[2] Al-Dolaimy, A. Structural Behavior of Continuous Reinforced Concrete Beams
with Openings and Strengthened by CFRP Laminates. M. Sc. Thesis, College of
Engineering, University of Babylon, IRAQ, 2011.
[3] Iraqi Specification, No.5. Portland cement, Baghdad, 1984.
[4] Said, M. and Elrakib, T. M. Enhancement of Shear Strength and Ductility for
Reinforced Concrete Wide Beams due to Web Reinforcement. International
Journal of Civil Engineering and Technology, 4(5), 2013, pp. 168–180.
[5] Hans I. A., Arturo, T. and Alejandro, G. Behavior of reinforced concrete
haunched beams subjected to cyclic shear loading. Elsevier Ltd., 2013.
![Prof. Dr. Mustafa B. Dawood and Reem Abd-Alraheem Nabbat
http://www.iaeme.com/IJCIET/index.asp 94 editor@iaeme.com
Cite this Article: Prof. Dr. Dawood, M. B. and Nabbat, R. A.-A. Flexural and
Shear Strength of Non-Prismatic Reinforced High Strength Concrete Beams
with Openings and Strengthened with NSM-CFPR Bars. International Journal
of Civil Engineering and Technology, 6(9), 2015, pp. 93-103.
http://www.iaeme.com/IJCIET/issues.asp?JTypeIJCIET&VType=6&IType=9
1. INTRODUCTION
Non prismatic beams have been used in various structures including buildings and
bridges since the first decades of the previous century, with an increasing application
as the structural engineering techniques were improved. With the beams being
tapered, the architects would be able to create and implement novel aesthetic
architectural designations, as well as the structural engineers who could seek for
optimum low weight - high strength systems through a redistribution of materials
along the structural members [1].
There is a large need for strengthening of concrete structures all around the world
and there can be many reasons for found strengthening, increased loads, design and
construction faults, change of structural system, and so on. The need exists for
strengthening in flexure as well as in shear. Epoxy plate bonding with Carbon Fiber
Reinforced Polymers, CFRP has been shown to be a competitive method for
strengthening of existing structures and increasing the load carrying capacity
The presence of web openings in such beam is frequently required reduce the
element shear capacity to provide accessibility such as doors and windows, or to
accommodate essential services such as ventilating, pipes and air conditioning ducts.
Enlargement of such openings due to architectural, mechanical requirements or
change in the building functions would reduce the element shear capacity [2].
2. EXPERIMENTAL PROGRAM
The experimental study consisted of two test groups. First group was designed to fail
in flexural and the second group designed to fail in shear.
The first group included six beams with and without openings. The beams has total
length (L) of 1500 mm ,the clear span (Ln) is 1350 mm ,the height at the mid span (H1) is
155 mm ,while the height at support (H2) is 220 mm and the width (b) is 150 mm. The
flexure reinforcement of beams consisted of 2Ф12 mm tension bars at bottom, and 2Ф10
mm at top. To avoid shear failure, the beams were reinforced for shear with Ф6 mm
closed stirrups spaced at 70 mm C/C as shown in Figure 1 show control beam F1.
Figure 1 Details of Tested Beams](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)