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Int.J.Curr.Microbiol.App.Sci (2014) 3(12): 950-961
International Journal of Current Microbiology and Applied Sciences
ISSN: 2319-7706 Volume 3 Number 12 (2014) pp. 950-961
http://www.ijcmas.com
Original Research Article
Rehabilitation of Existing Foundation Building to Resist
Lateral and Vertical Loads
El-Samny M. Kassem1 and Abd El-Samee W. Nashaat2*
1
2
Civil Engineering Department, Al-Azhar University, Cairo, Egypt
Civil Engineering Dep. Beni- Suef University, Faculty of Engineering, Beni- Suef, Egypt
*Corresponding author
ABSTRACT
Keywords
Foundation,
Tilted,
Existing,
Strengthening,
Shear wall
Some of the important causes of damage and collapse in concrete building can be
classified under general causes to facilitate analysis. These causes are overstress,
bad design, faulty construction, foundation failure, unexpected failure modes and
combination of causes. In the present work, a case study of an existing building
under construction found around Cairo greater area is presented. Methods of
strengthening the existing foundation of the buildings to resist lateral and vertical
loads are presented. The building consists of a basement, ground floor, and 11
typical floors. The building has been tilted to one side more than 10%. However,
the inclination is due to the fact that the foundation design was incorrect. The
thickness of raft was 0.95 meters while the required one should be 1.30 meter. In
addition, there is a great eccentricity on the raft due to lake of raft design that
makes the stresses on soil reaches 5 kg/cm2 at some areas while the allowable is 1.5
kg/cm2. The increasing area and thickness as well as strengthening of the existing
raft foundation are presented. In addition, new reinforced concrete shear walls
inside the building connected to the foundations are chosen for strengthening the
existing structure to resist lateral forces.
Introduction
There are many reasons to evaluate the
structural safety and overall serviceability of
existing building. Evaluation and repair of
those buildings are also necessary because
those buildings must meet cases as
exceeding their design reference period,
change in occupancy and bad design.
outstanding
historic
buildings.
The
methodology for assessing the safety and
resistance of historic buildings was
proposed. The evaluation and repair of
several historic buildings in the Shanghai
Band area were introduced.
Wensheng and Xilin (1997), presented a
discussion of the important protecting
Naderzadeh and Moinfar (2004), presented
an analysis of earthquake resistance
diagnosis carried out for some 350 buildings
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in Tehran. Buildings were selected based on
their age, usage, structure and distribution.
The
investigation
covered
Disaster
Management
Buildings,
Emergency
Response Organizations, hospitals, schools
as well as residential buildings. Factors
affecting seismic resistance of buildings in
this investigation included age, construction
quality, and ductility condition. Diagnosis of
buildings took place in several steps: iPreparation, ii- Field survey, and iiiDiagnosis and judgment. The diagnosis
method used was Seismic Index Method.
The calculated value of Seismic Index
Method was compared with the 'Seismic
Index Requirement' and the result was used
to evaluate the level of building safety. The
details of the diagnosis method implemented
as well as the proposed strengthening
methods are presented.
incorporating tilt-up construction examined
from several perspectives using relevant
case studies. The behavior of these buildings
during the Canterbury Earthquakes was
reviewed, and methods used to repair
earthquake damage were then discussed.
Specific
aspects
including
grouted
connections, bolted connections and panel
reinforcing were examined in detail. Issues
related to the design and constructions of
new buildings which incorporate tilt-up
construction were discussed.
Experimental study
Soil investigation
The soil profile indicates that the soil
condition consists of a filling material up to
2.00 meter depth from the ground surface
followed by about 3.00 meter very hard
brown clay (qu=1.50 kg/cm2). The above is
followed by 1.00 meter of medium clay soil
(qu =0.80 kg/cm2), followed by soft brown
clay up to 10.00 depth. The above is
followed by fine to medium sand up to
20.00 meter depth (end of borings). The
water table appears to exist at 3.5 meter
depth.
Elsamny and El Samee (2013), presented
some methods of strengthening existing
foundation concrete buildings to resist
lateral and vertical loads. A study case of an
existing sweet factory in Cairo area was
presented. Deterioration of some concrete
elements due to old age has been found. The
said condition of the foundation was due to
washing floors with chemicals to remove
sticky sweets. However, no adequate
disposal system was found (wastewater
collection). The analyses of the structural
elements of that existing building showed
that it is seismically unsafe. Retrofitting of
existing damage and deteriorated foundation
was done by adding new raft foundation and
considering the old foundation as plain
concrete. The addition of new shear and
wing walls was undoubtedly the best method
of strengthening the existing structure to
improve seismic performance. The shear and
wing walls were connected to the
foundation.
Building under construction
Figure (1) shows the building under study
and Figure (2) presents the general layout of
the typical floor of the building found
around Cairo greater area. The building
consists of a basement, ground floor, and 11
typical floors. The following observations
have been found; i-The building has been
tilted to one side more than 10 % as shown
in Figure (3). However, the inclination is
due to the fact that the foundation design
was incorrect. The thickness of raft was 0.95
meters while the required one should be 1.30
meter.
Urmson et al., (2013) presented buildings
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Figure.1 Building under study
Figure.2 The general layout of the typical floor
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Figure.3 Building inclination
Figure.4 Building model
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Figure.5 B.M.D. (m11) for old foundation
Figure.6 B.M.D. (m22) for old foundation
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Figure.7 Raft foundation strengthening by increasing area (plan)
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Figure.8 Raft foundation strengthening by increasing thickness (section 1-1)
Figure.9 Location of anchors
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Figure.10 Detail (1) implanting dowels in concrete
Figure.11 Raft foundation strengthening increasing thickness (section b-b)
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Figure.12 B.M.D (m11) for the strengthened foundation
Figure.13 B.M.D. (m11) for the strengthened foundation
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Figure.14 Proposed added shear walls
Figure.15 Details (II-II) connection between shear walls and columns
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Figure.16 Anchorage of added shear wall
In addition, there is a great eccentricity on
the raft due to lake of raft design that makes
the stresses on soil reaches 5 kg/cm2 at some
areas while the allowable is 1.5 kg/cm2. iiThe building has no structural system to
resist any lateral load (no shear and/or wing
walls). The foundation is found to be of raft
type at 2.50 meter depth.
I- Increasing the foundation area by 1.2 m
from three sides according to design as
shown in Figure (7). Increase
foundation area is done to ensure that
the vertical stress on soil doesn't
exceed the allowable stress 1.5 kg
/cm2 with any eccentricity on the raft.
II- Implant shear connectors (dowels) in
old foundation concrete
sides.
Calculation has been done to
determinate the number and the length
of shear connectors.
III- Shear connectors are placed to ensure
almost complete connection between
the old foundation and added
reinforced concrete foundation.
IV - Shear connectors are placed as
follows:A. holes are carried out in the old
foundation with diameter 18 mm. The
minimum horizontal and vertical
distances between holes are 0.25m and
Raft foundation strengthening technique
Strengthening of the existing foundation was
done by increasing the foundation thickness
as well as area. By using SAP2000 version
17 (linear and nonlinear static and dynamic
analysis and design of three dimensional
structures) the analysis and design of the
foundation has been done. Figure (4) shows
the building model. Figures (5 & 6) show
the bending moments for the old foundation.
Increasing area as well as thickness of the
new raft foundation is presented as follows:
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0.30 m respectively as shown in
Figure (8). The holes have been
cleaned by compression of air
B. Grouting is carried out by epoxy. Steel
reinforcement bars with diameter of 16
mm by the required length leaving at
least 1.0 m are placed as shown in
Figures (9 & 10).
V- Concrete cover has been removed from
the three sides and upper surface of the
old foundation reinforced concrete.
VI- Increasing thickness of foundation by
0.35 m is done. Implant additional
reinforcement mesh Ø16mm @ 15 cm
top and bottom as shown in Figures (8
- 11). Figures (12 & 13) show the
bending moments for the strengthened
foundation.
concluded the followings; Strengthening the
existing raft foundation is done by
increasing area as well as thickness. And
also new reinforced concrete shear walls
were added to strengthening the existing
structure to improved seismic performance.
References
Elsamny, M.K. and El Samee, W.N. 2013.
Retrofitting and strengthening of
Existing Building Foundation. Int. J.
Engineering Stud., 5(1), 111-128.
Kevadkar, M.D. and kodag, P.B. 2013.
Lateral Load Analysis of R.C.C.
Building. Int. J. Modern Engineering
Res. 3(3), 1428-1434.
Naderzadeh, A. and Moinfar, A.A. 2004.
Earthquake resistance diagnosis and
strengthening Techniques for existing
buildings in Tehran"13th World
Conference
on
Earthquake
Engineering Vancouver, B.C., Canada
August 1-6, 2004 Paper No. 912.
Urmson, C.R., Reay, A.M. and Toulmin,
S.H. 2013. Lessons learnt from the
performance
of
buildings
incorporating tilt-up construction in
the Canterbury Earthquakes. Alan
Reay Consultants Ltd., Christchurch,
New
Zealand.
2013
NZSEE
Conference.
Weng, Y.K, Stefano, P., Rajesh, D., Henri,
P.G. and Charles, R. 2010. Seismic
Performance of Reinforced Concrete
Buildings in the September 2010
Darfield (Canterbury) Earthquake.
Bullet. New Zealand Soci. Earthquake
Engineering, 43(4), 340-350.
Wensheng, L. and Xilin, L. 1997.
Evaluation and repair of historic
building structures in the Shanghi
Band area". First international Civil
Engineering (Egypt - China - Canada)
Dec 18 - 20 Cairo -Egypt, pp 227 237.
Adding a new shear wall to resist lateral
forces
Shear walls provide the most significant part
of the earthquake resistance of the building.
However, a severely damaged or poorly
designed building must be repaired or
strengthened by added shear walls in order
that the structure's strength for seismic force
and lateral force can be significantly
improved. The new structural elements in an
existing building change the dynamic
behavior of the whole space structure
considerably during an earthquake. Figure
(14) shows the added shear wall that
connected with foundation. The added shear
walls were monolithic to the existing
columns as shown in Figures (15 & 16). The
web thickness of the shear wall was 30 cm
and the vertical reinforcement were Ø16 @
15 cm and the horizontal reinforcement were
Ø12 @ 15 as shown in Figures (15 & 16).
The dowels with diameter of 16 mm by the
required length leaving at least 0.60 m were
20 cm deep in columns.
In Conclusion, from previous experimental
study and obtained results, it can be
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