This document summarizes an experimental investigation into the effect of corner angle on the strength and behavior of reinforced concrete corners under opening bending moments. Twelve specimens with corner angles ranging from 60 to 180 degrees were tested under two different reinforcement details. The results showed that corner efficiency, defined as the ratio of failure moment of the corner to the moment capacity of adjoining members, was significantly affected by the corner angle and was lowest at 120 degrees. Finite element analysis confirmed this variation in diagonal tensile stress concentration with angle. In general, specimens behaved elastically until first cracking, then stiffness was reduced as angle increased from 60 to 120 degrees but increased from 120 to 180 degrees.

1. ACI Structural Journal/January-February 1999 115
ACI Structural Journal, V. 96, No. 1, January-February 1999.
Received April 2, 1997, and reviewed under Institute publication policies. Copyright ©
1999, American Concrete Institute. All rights reserved, including the making of copies unless
permission is obtained from the copyright proprietors. Pertinent discussion including
author’s closure, if any, will be published in the November-December 1999 ACI Structural
Journal if the discussion is received by July 1, 1999.
ACI STRUCTURAL JOURNAL TECHNICAL PAPER
Results of an experimental investigation of the effect of the corner
angle on the strength and behavior of reinforced concrete corners
under opening bending moments are presented. Twelve specimens
divided into two groups with two reinforcement details and the
included angle varying from 60 to 180 deg were tested. From the
results obtained, and from those reported by others, it was found
that the efficiency of the joint is significantly affected by the angle
and is at its minimum when at 120 deg. Theoretical analysis using
finite element method (FEM) confirms the same variation of the
diagonal tensile stress concentration with the angle.
Keywords: corner joints; diagonal tension; efficiency; experimental study;
opening bending moment; reinforced concrete; ultimate strength.
INTRODUCTION
Reinforced concrete corners resisting positive bending
moment which tend to open the corner are known to have low
efficiency and special care is needed in their design. The effi-
ciency of corners is usually defined as the ratio of failure
moment of the corner to the moment capacity of the adjoining
members.1,2
Most of the experimental studies reported in the
literature, notably by Nilsson1,2 and others,3-9 were
concerned with the effect of reinforcement layout, steel
content, and bar diameter on the behavior and efficiency, and
of knee joints (or right-angled corners). Limited tests on
corner angles, other than 90 deg, were also reported by
Nilsson1
on 60 and 135-deg corners and Wahab and Ali8
on
145-deg corners. However, little attention has been given to
the study of the effect of the corner angle, as an independent
factor, on the efficiency of the joints.
From the available experimental data, there is a clear indi-
cation that corner efficiency is significantly reduced with an
increase in the steel ratio.1-9
From his test results, Nilsson1
concluded that, to avoid failure of the corners, upper limits
on the main reinforcement ratio p, as shown in Table 1,
should be observed for the 60, 90, and 135-deg angles.
Inclined reinforcement, or splays, should also be provided to
control the initial flexural cracking and should be half the
main reinforcement. For the 60-deg corners, the inclined
reinforcement should be laid in a haunch, the size of the
haunch being at least one-half of the adjoining member
thickness. The given limits of maximum reinforcement
percentages may be interpolated for intermediate corner
angles and interpolated or extrapolated with regard to the
yield strength for other steel qualities. This implies that a
linear relationship is assumed between the corner angle and
efficiency for the range of angles tested, and the given limits
suggest that the 90-deg corners are the weakest. Similar
limits to those suggested by Nilsson were also recommended
by Prakash10 and Holmes and Martin.11
The choice of the most appropriate layout of reinforce-
ment is derived from consideration of the flow of forces and
the stress distribution in the joint which indicates the need
for inclined bars (or splays) to resist the tensile force that
causes the initial crack at the inner angle of the corner. Also,
some form of confinement reinforcement is needed to resist
the secondary diagonal tension cracks that form in the upper
triangular portion. The occurrence of these diagonal cracks
often causes failure of the corner. Various reinforcement
details, with or without stirrups (ties) or inclined bars
(splays) have been tested, and there is sufficient evidence to
suggest that the most suitable detail for lightly reinforced
corners that results in the highest efficiency is the one that
combines the use of U-shaped bars with inclined bars.1,3-8
However, due to the scarcity of experimental results or
other guidance for the design of acute and obtuse angled
corners that occur in structures such as in folded plates, bridge
abutments, water channels, and staircases, their design
remains arbitrary. It has been suggested10,11 that the same
fundamental reinforcement detail may be used for such angles
in accordance with the same principles as applied to knee-
joints. The need for experimental data to clarify the effect of
corner angle on the behavior and efficiency of joints has
prompted the present study. In the test program conducted for
this purpose, a wide range of corner angles from 60 to 180 deg
was considered using two common types of reinforcement
details consisting of U-bars with or without inclined bars or
splays. Some additional data were also used from results of
tests on joints with similar reinforcement details and compa-
rable steel ratios reported by others.1,6-9
A theoretical analysis
of the stress distribution in the joints with various angles using
the finite element method (FEM) is also included.
RESEARCH SIGNIFICANCE
There is little information on the effect of the corner angle,
as an independent factor, on the behavior and efficiency of
reinforced concrete joints under opening bending moment. In
Title no. 96-S13
Table 1—Recommended reinforcement
percentages for different corner angles1
Corner angle,
deg
Steel yield strength fy
Inclined
reinforcement Remarks390 MPa 590 MPa
60 ρ ≤ 0.75 ρ ≤ 0.05 0.5ρ Corner should be
haunched
90 ρ ≤ 1.2 ρ ≤ 0.8 0.5ρ
135 ρ ≤ 1.0 ρ ≤ 0.65 0.5ρ
fcu = 29.4 MPa; 1 ksi = 6.895 MPa.
Effect of Corner Angle on Efficiency of Reinforced
Concrete Joints under Opening Bending Moment
by Hashim M. S. Abdul-Wahab and Shamil A. R. Salman

2. ACI Structural Journal/January-February 1999116
addition to the much-studied right angled or knee joint, a
wide range of obtuse and acute angled corner joints
frequently occurs in reinforced concrete structures such as
folded plates, bridge abutments, water tanks, staircases, and
pitched roof portal. In this experimental study, corner angles
were varied from 60 to 180 deg using two commonly used
reinforcement details. Theoretical analysis using FEM and
test results indicate that the efficiency of corners is signifi-
cantly affected by the corner angle, with corners of about 120
deg showing the least efficiency.
EXPERIMENTAL PROGRAM
Test specimen dimensions and reinforcement details are
given in Fig. 1 and Table 2. A total of 12 full-scale corner
specimens were tested to failure under symmetrically
applied loads. They were divided into two groups, A and B,
each consisting of six specimens with the corner angle
varying from 60 to 180 deg. In Group A, only U-shaped rein-
forcement was used at the joint, [Fig. 1(b)]. In Group B,
inclined reinforcing bars (splays) were added to the bent
reinforcement, as shown in Fig. 1(b). The 180-deg speci-
mens had the same reinforcement as the rest of the speci-
mens and were included to complete the range and to be used
as a reference for comparisons. All specimens were 300 mm
wide and 150 mm in total depth, with three-10 mm diameter
bars as the main reinforcement, the steel ratio being p =
0.68%. Nominal transverse reinforcement of 10 mm diam-
eter bars at 300 mm centers was provided to hold the main
reinforcement. For Group B, three 10-mm diameter inclined
bars were also provided near the inner angle of the corner.
All steel used was of the deformed surface type with a yield
strength fy = 467 MPa (67.7 ksi) and ultimate tensile strength
fu = 700 MPa (101.5 ksi).
The concrete was made with ordinary portland cement
(Type I), washed sand with a maximum size of 10 mm, and
coarse aggregate with a maximum size of 19 mm (0.75 in.)
The mix proportions by weight were 1:1(1/2):3 of
cement:sand:coarse aggregate. The water/cement ratio was
0.5. A horizontal pan mixer was used, and the specimens
were cast with their sides laid horizontally, using a steel form.
Control specimens of 150 x 150 x 150 mm (5.91 x 5.91 x 5.91
in.) cubes, 150 mm (5.91 in.) diameter x 300 mm (11.82 in.)
cylinders, and 100 x 100 x 400 mm (3.94 x 3.94 x 15.76 in.)
prisms were also cast with each test specimen to determine
the compressive and tensile splitting strength, modulus of
rupture, and modulus of elasticity.
All specimens were tested at 28 days under pure positive
(opening) bending moments using the basic loading arrange-
ment shown in Fig. 1. The load was applied gradually by the
hydraulic ram system. Special concrete pedestals were incorpo-
rated in the specimens to facilitate the application of the loads
and care was taken to insure free horizontal movement at the
supports. Concrete surface strains at selected locations at the
corner were measured using mechanical strain gages 200 and
150 mm in length (7.9 and 5.9 in.), and dial gages were used to
measure the vertical and horizontal displacements of the spec-
imen, as shown in Fig. 1. The increase in corner angle under
bending was also measured in all specimens. For this purpose,
an inclinometer was used which was made up of a rigid steel
angle with two dial gages mounted 100 mm apart on one leg, the
second leg being fixed to the inside of one leg of the specimen
ACI member Hashim M. S. Abdul-Wahab is Honorary Research Fellow in the Civil
Engineering Department, University of Brighton, UK. He received his BSc in civil and
structural engineering from Birmingham University in 1962 and his MEng and PhD
degrees in concrete structures from Sheffield University in 1964 and 1967, respec-
tively. His research interests include joints and connections in concrete structures and
steel fiber reinforced concrete.
Shamil A. R. Salman is senior structural engineer at Al-Idrisi Center for Engineer-
ing, Baghdad, Iraq. He obtained his BSc in civil engineering from the University of
Baghdad in 1976 and his MEng in reinforced concrete structures from the University
of Technology, Baghdad, in 1988.
Fig. 1—Details of specimen and loading arrangement (1 in. =
25.4 mm).
Table 2—Summary of specimens, details, and
concrete properties
Specimen
Corner
angle, deg
Reinforcement
detail (Fig. 1b)
Concrete com-
pressive strength,
fc′ , MPa
Concrete ten-
sile strength,
ft, MPa
1 A1 60 U shaped,
detail (A) 33.40 4.00
2 A2 75 = 30.83 3.96
3 A3 90 = 30.83 4.10
4 A4 120 = 29.0 3.96
5 A5 150 = 32.75 3.54
6 A6 180 = 30.00 3.96
7 B1 60
U shaped +
splay, detail
(B)
30.00 4.03
8 B2 75 = 29.70 3.20
9 B3 90 = 30.85 4.10
10 B4 120 = 26.10 3.00
11 B5 150 = 30.60 3.40
12 B6 180 = 32.83 3.46
Average 30.83 3.72
1 ksi = 6.895 MPa.

3. ACI Structural Journal/January-February 1999 117
as close as possible to the corner. The dial gages used had a
minimum graduation of 0.002 mm.
As the test progressed, readings of the vertical and hori-
zontal displacements and strains were taken at each stage of
loading and the development and propagation of the cracks
were noted as well as the load at first crack and the mode of
failure. The control specimens were tested on the same day
as the corner specimens; only the results for the compressive
and tensile splitting strength are given in Table 2.
EXPERIMENTAL RESULTS
Behavior under load
Table 3 gives the observed initial cracking moment, failure
moment, and modes of failure as well as the calculated ultimate
moment capacity and efficiency of the specimen tested. The
ultimate moment of resistance of the adjoining members, and
hence the corner efficiency Mut/Muc were calculated using the
ACI 318-89 code12 method for reinforced concrete sections.
In general, at the early loading stages, the specimens
behaved in an elastic manner until the appearance of the first
crack. The crack usually started at the inner angle of the
corner and extended upwards, branching off around the bent
bars, then running in the diagonal direction parallel to the
inclined reinforcement towards the compression zones at the
upper surfaces of the members. Diagonal tension cracks
within the bent reinforcement zone also appeared in some
cases as well as some flexural cracks that appeared along the
members. One exception was Specimen B6, in which the
first crack appeared on one of the adjoining members and
spread upwards.
The strain variation in the joint parallel and perpendicular
to the corner diagonal followed the expected pattern
obtained from theoretical analysis and those reported by
earlier studies.1,8 Figure 2 shows typical strain variation with
applied moment for Specimen B4, and Fig. 3 shows the
variation of the strain profile with moment along the corner
diagonal for the same specimen.
The influence of corner angle on corner deformation is
illustrated by its effect on the vertical and horizontal
displacements as well as the angular alteration of the corner.
Figure 4 shows the variation of the vertical displacement at
the joint with the applied moment for all specimens tested
while Fig. 5 shows the variation in the average horizontal
displacement. The vertical displacement measurements give
the total deflection of the specimen at the joint contributed
by the bending of the two members, the increase in angle,
and the effect of the horizontal movement at the supports. It
is evident that the general stiffness of the corner specimens
after the appearance of the first crack is significantly reduced
as the corner angle is increased from 60 to 120 deg (A4, B4),
but the stiffness then increases as the angle increases up to
180 deg. On the other hand, horizontal displacements within
Table 3—Test results
Specimen
Corner angle,
deg
Cracking
moment, kNm
Failure moment
Mut, kNm
Calculated ultimate
moment Muc, kNm
Corner efficiency
Mut/Muc Type of failure
1 A1 60 2.00 9.24 11.94 77.4
Diagonal cracking and flexural yielding of bars
at joint
2 A2 75 2.00 7.53 11.88 63.4 Same as above
3 A3 90 2.24 7.47 11.88 62.8 Same as above
4 A4 120 3.00 5.80 11.83 49.0 Same as above
5 A5 150 3.30 7.60 11.92 63.7 Same as above
6 A6 180 0.54 10.04 11.86 84.6 Flexural yielding of bars at joint
7 B1 60 2.87 18.16 11.86 153.1 Diagonal cracking at joint
8 B2 75 2.13 12.93 11.85 109.1 Same as above
9 B3 90 2.30 11.58 11.88 97.5 Same as above
10 B4 120 3.15 9.00 11.74 76.6 Same as above
11 B5 150 3.30 15.90 11.87 134.0 Diagonal cracking at joint and flexural yielding
of bars outside joint
12 B6 180 3.78 19.79 11.93 165.9 Flexural yielding of bars outside joint
1 kip-in. = 0.113 kNm.
Fig. 2—Variation of strain with bending moment for
Specimen B4 (1 kip-in. = 0.113 kNm).
Fig. 3—Typical variation of strain profile along corner
diagonal (6-6) for Specimen B4 (1 kip-in. = 0.113 kNm).

4. 118 ACI Structural Journal/January-February 1999
the elastic range were generally similar for all specimens, but
at the postcracking stage, the displacements were consis-
tently reduced with the increase in angle from its highest
value for 60 deg (A1, B1) to its lowest value for 150 deg (A5,
B5), the value for 180 deg being assumed to be zero. The
effect of the corner angle on vertical and horizontal displace-
ment is further illustrated in Fig. 6 for an applied bending
moment of 5 kNm (44.2 kip-in.).
Figure 7 shows the measured increase in corner angle in
radians with the applied bending moment. The increase in
angle was also significantly affected by the corner angle at the
post-cracking stage, the 120-deg corner specimens exhibiting
the highest increase. Figure 8 shows the variation in the
increase in the corner angle for an applied bending moment
of 5 kNm (44.2 kip-in.) for the full range of angles tested. The
results further confirm that the corner stiffness is least when
the angle is about 120 deg.
With the exception of Specimen A6 and B6 (180 deg), all
specimens failed after the formation of diagonal tension
Fig. 4—Variation of central deflection with applied bending
moment for Groups A and B (1 in. = 25.4 mm; 1 kip-in. =
0.113 kNm).
Fig. 5—Variation of average horizontal displacement with
applied bending moment for Groups A and B (1 in. = 25.4 mm;
1 kip-in. = 0.113 kNm).
Fig. 6—Effect of corner angle on vertical and average hori-
zontal displacement under 5 kNm bending moment (1 in. =
25.4 mm; 1 kip-in. = 0.113 kNm).
Fig. 7—Increase in angle with applied bending moment for
Groups A and B (1 kip-in. = 0.113 kNm).
Fig. 8—Effect of corner angle on increase in angle under
5 kNm bending moment (1 kip-in. = 0.113 kNm).

5. ACI Structural Journal/January-February 1999 119
cracks that caused the upper portion to be pushed out,
coupled with the flexural yielding of the bars at the joint. In
the 180-deg specimens, A6 and B6, as would be expected,
failure was caused by flexural yielding of the bars either at
the joint or just outside the joint region, as indicated in
Table 3. It should also be noted that the inclusion of the
inclined bars in Group B helped to control and delay the
initial cracks on the inside of the corner and resist the sepa-
ration of the two members. Figure 9 shows typical crack and
failure patterns for the specimens of Group B.
Efficiency and ultimate strength
Table 3 gives the ultimate strength and efficiency of the
tested specimens. The results obtained for the efficiency of
corners with different angles are shown in Fig. 10. Also
shown on the same figure are some experimental results
obtained from tests reported by other investigators1,6-9 on
joints of 60, 90, 135, and 145 deg with similar reinforcement
details and the nearest comparable steel ratios, which are
summarized in Table 4. However, allowance should be made
for the variation in concrete strength, steel yield strength, and
geometry of the specimens tested by others researchers,
which have an important effect on the ultimate strength. For
example, the higher efficiency values for the 90-deg corners
reported by Nilsson are due to the fact that the adjacent
members had different dimensions, the thickness being 250
and 300 mm (9.8 and 11.8 in.). Tests have shown that the effi-
ciency is greatly improved when the thicknesses of the
adjoining members were not the same.8 Also, diagonal
tension failure, which was the common cause reported,
depends mainly on the quality and strength of the concrete.
As shown in Fig. 10, experimental results show that the
efficiency of the corner joint decreased with the increase of
the angle starting from 60 up to 120 deg, after which the effi-
ciency increased with the angle up to 180 deg. The efficiency
of specimens with inclined bars, Group B, was much higher
than that without the inclined bars, Group A, the ratio
varying from 1.55 for B3/A3 to 1.97 for B1/A1. However,
despite the significant improvement in efficiency due to the
added inclined bars in Group B, the variation in efficiency
followed the same pattern as for Group A and was below
100% when the angle was between 90 and 130 deg, the
lowest efficiency recorded being for the 120-deg corners. It
should be noted that the lower efficiency exhibited by the
120-deg corners may be due, in part, to the lower concrete
tensile splitting strength, as shown in Table 2, which precip-
itates the diagonal tension failure. The adjusted efficiency
values relative to the average concrete strength for each
group are also shown in Fig. 10.
While further tests may be necessary for corner angles in
the range of 90 to 140 deg to determine precisely the most
critical angle, it is evident that the design of such corners
should be made with special care, with attention being given
to the expected reduction in efficiency. The results also indi-
cate that interpolation for the reinforcement quantity
between 60, 90, and 135-deg corners as suggested by
Nilsson would lead to overestimating the strength of the
joints. There is no evidence of a linear relationship between
strength and corner angle to justify linear interpolation or
extrapolation.
THEORETICAL CONSIDERATION
To study the effect of varying the corner angle on the stress
distribution in the joint, a plane stress analysis by FEM was
used.13
The six cases considered in this study were analyzed
assuming the material to be linearly elastic with Poisson’s ratio
= 0.2 and the concrete strength values taken as measured. It
should be noted that the state of stress in corners calculated by
the theory of elasticity is valid only before cracking occurs.
Nevertheless, the results obtained help to indicate the likely
locations for the tensile stress and clarify the variation of the
stress concentration with the change in angle. Figure 11 shows
a typical example of the loading method and FEM mesh used
for 60-deg corners.
Variation of stress with corner angle
From experimental evidence, the most common cause of
failure in joints is due to diagonal tension cracks caused by the
tensile stress parallel to the corner diagonal. For this reason the
stress distribution obtained from the FEM analysis along
Fig. 9—Failure patterns for Group B.
Fig. 10—Efficiency versus corner angle.

6. 120 ACI Structural Journal/January-February 1999
various axes perpendicular to the corner diagonal and parallel
to the inclined reinforcement were considered. Fig. 12 shows
typical stress distribution for a 150-deg corner along two prin-
cipal axes. The top axis, a-a, is at the apex of the bent reinforce-
ment where the secondary diagonal tension cracks usually
appear and tend to cause the upper portion of the corner to be
pushed off. Axis b-b is taken at middepth of the corner diagonal
where most of the specimens exhibited primary diagonal
tension cracks leading to failure, as was shown in Fig. 9.
Figure 13 shows the variation in the maximum diagonal
tensile stresses along the two selected axes, a-a and b-b, with
the corner angle. The diagonal tensile stress increased with
the corner angle between 60 and 120 deg, after which the
stress gradually decreased down to zero at 180 deg. On the
same figure, the reduction in efficiency for the specimens
tested, taken relative to Specimens A6 and B6, as well as
some of those reported by others, is shown. The reduction in
efficiency appears to follow the same pattern as the increase
in the diagonal tensile stress with the corner angle.
It is recognized1,2
that the confining effect of the bent rein-
forcement tends to close the diagonal crack that may appear
inside the loop, thus contributing to the effective resistance of
the diagonal tensile stress. However, at a point just outside the
bent reinforcement along axis b-b, Fig. 12, the splitting
tensile stress is not affected by the confining action of the
bent bars and may be the point of a possible early formation
of diagonal cracks that may extend and hasten the final failure
of the joint. There may be no simple way to reinforce against
all tensile stresses that occur, and the ultimate strength of the
corner would, therefore, depend on the tensile strength of the
Table 4—Results of tests reported by other investigators
Source
Specimen
reference
Corner angle,
deg
Steel ratio r,
percent fcu, MPa fy, MPa
Efficiency,
percent Inclined bars provided
Nilsson1
V53 60 0.5 32.4 662.2 102 Yes with haunch
V54 60 0.48 30.7 684.2 103 Yes with haunch
UV5 90 0.75 32.9 422.3 114 Yes
UV6 90 0.75 28.6 412.5 115 Yes
UV7 90 0.75 33.25 415 123 Yes
U24 90 0.75 39 432.1 87 —
U51 90 0.76 34.5 656.8 104 Yes
U59 90 0.76 26.4 696.5 72 —
V2 135 1.0 32.7 402.2 88 —
V11 135 0.66 30.8 662.2 99 Yes
V13 135 0.7 39.2 665.1 110 Yes
Noor6
BD1 90 0.52 38 498 94 Yes
B1 90 0.59 53 433 91 —
Skettrup7
7702 90 0.66 17.4 573 77 Yes
7704 90 0.58 22.1 564 100 Yes
Wahab & Ali8
A3 145 0.65 36.6 470 102 —
A4 145 0.65 37.9 470 139 Yes
Jackson9
A10-6 90 0.62 32 487 92 —
A12-4 90 0.61 46 543 65 —
1 ksi = 6.895 MPa.
Fig. 11—Finite element mesh for 60-deg corner. Fig. 12—Distribution of calculated diagonal stresses along
Axes (a-a) and (b-b) for 150-deg corner under bending
moment of 2 kNm (1 in. = 25.4 mm; 1 ksi = 6.895 MPa).

7. ACI Structural Journal/January-February 1999 121
concrete. One possible solution that needs investigating is the
use of steel fiber reinforcement in the joint to enhance the
tensile resistance of concrete. The variation of the tensile
stress at this location with the corner angle and the reduction
in efficiency followed the same pattern as the maximum
stress shown in Fig. 13.
It is worth noting that in a recent study, Jackson9
suggested
that the primary cause of failure at a bending moment less than
that associated with yielding of the main reinforcement (i.e.,
reduced efficiency) is bond failure. For some reinforcement
layouts where anchorage is insufficient, this may be the case,
but in all the specimens tested in this study, as well as most of
those reported by others, the failure pattern was due to diagonal
tension cracking as previously discussed.
CONCLUSIONS
From the experimental investigation and the limited theoret-
ical analysis reported herein, the following conclusions can be
drawn for effect of the corner angle on the behavior of
reinforced concrete joints under opening bending moment.
1. The efficiency of corners is significantly affected by
the corner angle, with corners of 120 deg showing the least
efficiency.
2. The use of inclined bars greatly improves the corner effi-
ciency. For the steel content (p = 0.68%) and depth of members
(150 mm) used in this study, an increase in the range between 55
and 100% was observed, depending on the angle.
3. The variation in strength with the corner angle is not
linear, and interpolation for the amount of steel, as suggested
by Nilsson,1
is not applicable.
4. The results obtained using FEM analysis for diagonal
tension forces and stresses at critical sections and locations
in the corner zone give a plausible explanation for the varia-
tion in efficiency of joints with the corner angle as observed
in the experimental results.
ACKNOWLEDGMENTS
The experimental work reported in this paper was conducted at the
Building and Construction Engineering Department, University of Tech-
nology, Baghdad. The authors gratefully acknowledge the facilities made
available and the valuable help and assistance of the technical staff of the
department.
REFERENCES
1. Nilsson, I. H. E., “Reinforced Concrete Corners and Joints Subjected
to Bending Moment—Design of Corners and Joints in Frame Structures,”
Document No. D7-1973, National Swedish Institute for Building Research,
Stockholm, 1973, 249 pp.
2. Nilsson, I. H. E., and Losberg, A., “Reinforced Concrete Corners and
Joints Subjected to Bending Moment,” Proceedings, ASCE, V. 102, ST 6,
June 1976, pp. 1229-1253.
3. Mayfield, B.; Kong, F. K.; Bennison, A.; and Davis, J. C. D., “Corner
Joint Detail in Structural Lightweight Concrete,” ACI JOURNAL, Proceed-
ings V. 68, No. 5, May 1971, pp. 366-372.
4. Mayfield, B.; Kong, F. K.; and Bennison, A., “Strength and Stiffness
of Lightweight Concrete Corners,” ACI JOURNAL, Proceedings V. 69, No.
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5. Somerville, G., and Taylor, H. P. J., “Influence of Reinforcement
Detailing on the Strength of Concrete Structures,” The Structural Engineer
(London), V. 50, No. 1, Jan. 1972, pp. 7-19.
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“Concrete Frame Corners,” ACI JOURNAL, Proceedings V. 81, No. 6, Nov.-
Dec. 1984, pp. 587-593.
8. Abdul-Wahab, H. M. S., and Ali, W. M., “Strength and Behavior of
Reinforced Concrete Obtuse Corners under Opening Bending Moments,”
ACI Structural Journal, V. 86, No. 6, Nov.-Dec. 1989, pp. 679-685.
9. Jackson, N., “Design of Reinforced Concrete Opening Corners,” The
Structural Engineer, V. 73, No. 13, July, 1995, pp. 209-213.
10. Prakash Rao, D. S., “Detailing of Reinforcement in Concrete Struc-
tures,” Indian Concrete Journal (Bombay), V. 59, No. 1, Jan. 1985, pp. 22-25.
11. Holmes, M., and Martin, L. H., Analysis and Design of Structural
Connections—Reinforced Concrete and Steel, Ellis Harwood, Chichester,
England, 1983, pp. 45-85.
12. ACI Committee 318, “Building Code Requirements for Reinforced
Concrete (ACI 318M-89),” American Concrete Institute, Farmington Hills,
Mich., 1992, 347 pp.
13. Hinton, E., and Owen, D. R. S., Finite Element Programming,
Academic Press, London, 1977.
Fig. 13—Variation of calculated maximum diagonal tensile stress with corner angle under
bending moment of 2 kNm in comparison with observed reduction in efficiency (1 ksi =
6.895 MPa).