Rehabilitation of Existing Foundation Building to Resist Lateral and ...

Int.J.Curr.Microbiol.App.Sci (2014) 3(12): 950-961

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Original Research Article

Rehabilitation of Existing Foundation Building to Resist

Lateral and Vertical Loads

El-Samny M. Kassem

1 and Abd El-Samee W. Nashaat

2*

1Civil Engineering Department, Al-Azhar University, Cairo, Egypt

2Civil Engineering Dep. Beni- Suef University, Faculty of Engineering, Beni- Suef, Egypt

*Corresponding author

A B S T R A C T

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.

Wensheng and Xilin (1997), presented a

discussion of the important protecting

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.

Naderzadeh and Moinfar (2004), presented

an analysis of earthquake resistance

diagnosis carried out for some 350 buildings

International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 3 Number 12 (2014) pp. 950-961

http://www.ijcmas.com

K ey wo rd s

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.


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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: i-

Preparation, ii- Field survey, and iii-

Diagnosis 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.

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.

Urmson et al., (2013) presented buildings

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.

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.


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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. ii-

The 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.

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:

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


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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.

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

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.

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