2012 / 2013
FINAL YEAR PROJECT
Submitted in fulfillment of the requirements for the
ENGINEERING DEGREE FROM THE LEBANESE UNIVERSITY
FACULTY OF ENGINEERING- BRANCH III
Major : Civil Engineering
By:
Mortada Chamas
________________________________________________
Structural Design of Sky Tower
Supervised by: Dr. JAMIL DAMAJ
Defended on Monday 23 septembre 2013
the jury:
Dr. JAMIL DAMAJ
Dr. Hasan AL Haj
Dr. Nayef Atrisi
President
Member
Member
SKY TOWERS PROJECT
KHALDEH- LEBANON
STRUCTURAL REPORT
Design criteria-Structural Analysis-R.C Design
1.
Definition of the Intervention
The aim of the present report is to conduct the structural study of the project parts and to
assess the adequacy of the preliminary structural resisting systems for gravitational and
lateral loads, as specified by the design criteria and according to the specifications.
The assessment to the structural systems adequacy will be done considering the following
factors:
- The latest architectural drawings
- The specified super imposed dead loads and live loads.
- The structural response of the buildings to the lateral loads
In this Phase of study the basic design criteria (codes, loadings, materials…) and the
analysis methods are presented. The basic assumptions of the numerical analysis are also
stated. Based on the design criteria and assumptions data, a rigorous structural analysis is
conducted with three dimensional models of the buildings using the ETABS software.
The buildings response, obtained from the analysis results, led to the determination of:
- the maximum lateral sway of buildings which allows the adjustment of the expansion
joint gap.
- the internal forces in the different structural elements, which allowed the checking /
design of the vertical structural elements (columns, walls)
- the transfer of data to other software (Safe, S-concrete…) which allowed the checking of
the proposed foundations and slabs dimensions .
2. Preface
B
eing a civil engineer graduate, we are going to introduce the structural skills
acquired through our learning process in the faculty of engineering-Lebanese
University. Our project is one of the engineering articles concerning structural
detailing of a building. So we chose the SKY TOWER on KHALDEH-LEBANON to be
our case of study. Designers obviously need the full data related to the building in order to
be able to start his study, and he should determine the means that may help him creating
his model.
Architectural Details:
the SKY TOWER in Lebanon is located in khaldeh, Beirut, on a rock type soil. The
project consists of ten residential buildings of various heights and floor areas, summer
club, and winter club. The current block A consists of two Basement floors, one Ground
floor, 11 residential floors.
The project consists of ten residential buildings of various heights and floor areas,
summer club, and winter club. The current block A (my project) consists of two Basement
floors, one Ground floor, 11 residential floors.
BASEMENT PLAN
USUAL
FLOOR
PLAN
GF
3. Major Constraints
The structural analysis and concrete design of the project was governed by the following
constraints:
- the architectural requirements of the buildings which induced irregularities in the
buildings shapes and the distribution of the supporting elements.
- the relatively large spacing between supports.
4. Design Criteria
4.1 Codes of Practice , standards
The buildings straining forces (gravitational and lateral) and the capacity of the
structural resisting elements were determined in accordance to the following code of
practice:
- the Uniform Building Code “UBC 97” for the determination of lateral forces intensity
and distribution (Earthquake and Wind pressure).
- “ACI 318-02” for the determination of loads combinations, the design and detailing of
various concrete elements (slabs, beams, columns, walls and foundations).
- “ASCE-05” code: for wind loads and analysis
4.2 software :
In addition, the design is going to be done with the aid of the following software programs:
- Autodesk AutoCAD
Draw and plan and detail any needed figure, with 2D and 3D features.
- CSI- Etabs
ETABS is a sophisticated special purpose analysis and design program
developed specifically for building systems. It is mainly used for
modeling, and mainly the design of vertical elements.
- CSI- Safe
Design of slabs, beams and foundations, reinforced and post tensioned
concrete.
- S-CONCRETE
S-concrete is a stand-alone product that investigates, designs, and
graphically details reinforced concrete beam, column, and wall
sections.
- BEAMD
Design and draw any given beam. Get the loads and gives the resulting
forces and moments, and checks code capability with the results.
- TALREN
Design and draw the supporting system of any excavation, including
piles, anchorages. And gives detailed report of the results. Used
especially for sliding circles.
5. Design Assumptions
In order to be able to start our design, we must start from a definite point, where we
determine the main materials that is going to be used. Also we should recognize the
structural elements presented in the building, and give a predimension for each element to
be checked then. Finally we have to load each member by the code’s recommended load
related to its type.
5.1 Materials:
Two main materials are to be used in the construction phase of the building: Concrete and
Steel.
In our project we will use concrete with f’c= 20MPa, and another type of f’c= 32MPa. And
steel with tensile yield fy=420MPa for longitudinal reinforcement, and fy= 280 MPa for
transversal reinforcement.
5.2 Structural elements and Predimnesioning
As any alternative structure, our structure contains the following structural elements:
slabs, columns, walls, beams, and footings.
a) Slab: slabs assumptions are concerned about its type and thickness. Clearly
the designer prefers less thickness that offers him less cost. These
assumptions depend mainly on the spans found through the slab, and the type
of support used. Due to long spans found between supports (columns), we
decided to use a two way solid slab (flat plate).
We will use a two way solid slab with 25cm thickness (refer to slab design
section). As analysis results are derived, we are going to check the deflection
and reinforcement.
b) Columns: column sections will be taken as given by the architectural
engineer. These sections will be checked to support its loads and will be
reinforced by 1% steel of its gross section as a minimum reinforcement. If we
have a slender column in the project then we are going to consider the PDelta effect, these checks will be done in the column design paragraph.
c) Shear Walls: these sections are primarily determined by the architectural
engineer. Walls sections and position will be checked against loads and
mainly shear and torsion.
d) Beams: beams are presented in the huge span found in the theatre, there
sections will be detailed the frame design paragraph.
e) Footings: Thickness and dimensions are related to loads and bearing capacity
of supporting soil. Thus whole design is found in footing design paragraph.
5.3 Dead Loads
The dead loads of the buildings are:
- self weight of the structural elements based on preliminary dimensioning of the
structural sections and the materials specific unit weight
- super imposed dead loads including finishing and partition: as indicated in the drawings
Dead load is computed mainly for slabs:
D.L. =
= 25 x 0.25 = 6.25 kPa
S.D.L. = 1.5 kPa for basement floors.
= 4.0 kPa for GF and upper floors.
5.4 Live Loads
Table 1.2 ACI-08:
Type of use
Apartment buildings
Private units
Public rooms
Corridors
Office buildings
Offices
Lobbies
Corridors above first floor
Garages (cars only)
Stores
First floor
Upper floor
Ware house
Light storage
Heavy storage
Minimum uniformly distributed life loads
Lb/ft2
kPa=KN/m2
40
100
80
1.92
4.8
3.84
50
100
80
50
2.4
4.8
3.84
2.4
100
75
4.8
3.6
125
250
6.0
12.0
As our project is an residential building, in addition to car garages in the basement floors,
we can assume live loads as follows:



Basement floors: L.L. = 2.5 kPa.
Ground floor: L.L. =4.8 kPa.
Upper floors: L.L. = 2.5 kPa.
5.5 Seismic load
The UBC 97 recommends that the static lateral force procedure of Section 1630
may be used for the following structures:
1. All structures, regular or irregular, in Seismic Zone 1 and in Occupancy
Categories 4 and 5 in Seismic Zone 2.
2. Regular structures under 240 feet (73 152 mm) in height with lateral force
resistance provided by systems listed in Table 16-N, except where Section 1629.8.4,
Item 4, applies.
3. Irregular structures not more than five stories or 65 feet (19 812 mm) in height.
4. Structures having a flexible upper portion supported on a rigid lower portion
where both portions of the structure considered separately can be classified as being
regular, the average story stiffness of the lower portion is at least 10 times the
average story stiffness of the upper portion and the period of the entire structure is
not greater than 1.1 times the period of the upper portion considered as a separate
structure fixed at the base. [1--- 1629.8.3]
The “sky tower is in zone 1 so the static analysis is required.
Seismic load parameters are related to the zone of study, which is Beirut in our
case. Beirut is said to be of zone 2B, referring to UBC97-TABLE 16-1, we find
Seismic Zone Factor (Z) = 0.25
Soil investigations proved that the site is of dense sand type.
Soil Profile Type = SC
Referring to UBC97-TABLE 16-J, TABLE 16-Q, TABLE 16-R, we find
Seismic Coefficient
Seismic Coefficient
Referring
to
TABLE 16-N
Ca = 0.24
Cv = 0.32
UBC97
Over-strengthFactor,
R = 4.5 (BWS)
Referring to UBC97-TABLE 16-K
Importance Factor = 1.5
Eccentricity Ratio = 0.05
Time Period, Ct (ft) = 0.02 for
BWS
Four load cases will be formed QX1 and QX2
with X direction and opposite y-eccentricity,
and QY1 and QY2 with Y direction and
opposite x-eccentricity. Also two dynamic
loads are defined SPEC1 and SPEC2.
I - Combinations:
Combinations used in our analysis are in accordance with UBC97-1612.2 for
strength design, and UBC97-1612.3 for working stress design.
Each load case will be placed at its appropriate position so we will have about
50 combos.
II- Modifiers:
1- Slabs:
Membrane f11 modifier factor
Membrane f22 modifier factor
Membrane f12 modifier factor
Bending moment M11 modifier factor
Bending moment M22 modifier factor
Bending moment M12 modifier factor
Shear V1-3 modifier factor
Shear V2-3 modifier factor
Mass modifier factor
Weight modifier factor
1
1
1
0.25
0.25
0.25
1
1
1
1
2- Shear Walls:
Membrane f11 modifier factor
Membrane f22 modifier factor
Membrane f12 modifier factor
Bending moment M11 modifier factor
Bending moment M22 modifier factor
Bending moment M12 modifier factor
Shear V1-3 modifier factor
Shear V2-3 modifier factor
Mass modifier factor
Weight modifier factor
1
1
1
0.70
0.70
0.70
1
1
1
1
3- Columns:
Cross section (Axial Area) modifier factor
Shear area in 2 direction
1
1
Shear area in 3 direction
Torsional constant
Moment of inertia about 2 axis
Moment of inertia about 3 axis
Mass modifier factor
Weight modifier factor
1
1
0.70
0.70
1
1
4- Beams:
Cross section (Axial Area) modifier factor
Shear area in 2 direction
Shear area in 3 direction
Torsional constant
Moment of inertia about 2 axis
Moment of inertia about 3 axis
Mass modifier factor
Weight modifier factor
1
1
1
1
0.35
0.35
1
1
III- Base Shear Calculation
Base shear (V) is the total lateral force or the shear at the base for which a
building in a seismic zone is to be designed.
The total design base shear in a given direction shall be determined from the
following formula:
V = Cv .I .
The total design base shear need not exceed the following:
Vmax = 2.5 Ca .I .W/R
The total design base shear shall not be less than the following:
Vmin = 0.11 Ca .I .W
Numerical Calculation under the effect of EQX1 for instance:
V (Eqn 1) = 0.0215W
V (Eqn 2) = 0.0302W
V (Eqn 3) = 0.0060W
V (Eqn 4) = 0.0097W
V Used = 0.0474W = 1652.88
Then consider V = 0.0278W = 0.0278 x 177107.38 = 4923.6 T = 1652.88
(under EQx1) .
IV- Finding Period of the Building Structure
The Value of the structure period T shall be determined from one of the following methods:
Method A:
The value T may be approximated from the following formula:
TA = Ct (hn)3/4 = 0.0488 x (65.7)3/4 = 2.16s.
Where:
Ct = 0.0488 for all other buildings except the steel moment-resisting frames and the reinforced
concrete moment resisting-frames and eccentrically braced frames.
H n: height in (m) above the base to the top level
Method B:
The fundamental period T may be calculated using the structural properties and deformational
characteristics of the resisting elements in a properly substantiated analysis. The analysis shall be
in accordance with the requirements of Section 1630.1.2.
The value of T from Method B shall not exceed a value 40 percent greater than the value of T
obtained from Method A in zone 1. (max TB adopted ≤1.4TA =2.04s).
The fundamental period T may be computed by using the following formula:
The values of fi represent any lateral force distributed. The elastic deflections, δi, shall be
calculated using the applied lateral forces, fi.
Note: TB is calculated through the software: ETABS
V - Finding the Distribution of Lateral Forces
In Accordance with section 1630.5 in UBC97, the total force shall be distributed over the height of
the structure according to the general formula:
The concentrated force Ft at the top, which is in addition to Fn , shall be determined from the
formula: Ft = 0.07 T.V = 4952 KN < 0.25V = 13061.6 KN.
The remaining portion of the base shear shall be distributed over the height of the structure
according to the following formula:
MODAL LOAD PARTICIPATION RATIOS
(STATIC AND DYNAMIC RATIOS ARE IN PERCENT)
TYPE
NAME
STATIC
Load
DEAD
Load
SIDL
0.0374
0.0000
Load
LIVE
0.0146
0.0000
Load
EQX
99.9963
75.4668
Load
EQY
99.9994
91.8971
Load
WIND
Load
WIND-2
99.9999
98.7186
Load
WIND-3
99.9998
97.8448
Load
WIND-4
99.9998
97.8201
Load
WIND-5
99.9997
96.8875
Load
WIND-6
100.0000
99.0771
Load
WIND-7
99.9999
98.2314
0.0250
99.9998
DYNAMIC
0.0000
97.6071
Load
WIND-8
99.9999
98.1201
Load
WIND-9
99.9999
98.6219
Load
WIND-10
99.9998
97.2416
Load
WIND-11
99.9997
97.1819
Load
WIND-12
99.9999
98.5175
Accel
UX
99.9990
96.2777
Accel
UY
99.9999
99.5175
Accel
UZ
0.0000
0.0000
Accel
RX
100.0000
99.9991
Accel
RY
100.0000
99.9982
Accel
RZ
-802.9596
94.6961
5.6 Wind Pressure
The project is studied for wind pressure corresponding to 100 mph wind speed and
exposure type D, according to the ASCE7-02 specifications..
Wind speed
= 100 mph
Exposure type
=D
Importance Factor
=1.15 (occupancy IV, speed<100)
Topographical
=1
Factor
Gust Factor
= 0.85 ( rigid building )
Directionality
= 0.85 (Main Wind Force Resisting System)
Factor
Wind Coefficient
= 0.8
Leeward coefficient
= 0.5
ASCE code contributes to make 12 load case for wind loads W1 to W12 changing the
eccentricity of wind application to the building.
5.7 Thermal Effects
In general, spacing between expansion joints shall be made to match architectural
requirements and shall range between 45 and 70 m.
For spans exceeding the above mentioned range, special design considerations shall be
taken into account for the temperature effects.
The temperature, uniform daily/ seasonal variation and the thermal gradient, were
assumed as ± 20C.
5.8 Fire Resistance
The structure of the buildings shall be 2 hours rated (columns, bearing walls beams, etc..) .
6 . Structural Materials
Concrete Compressive Strength:
- 20 MPa, for Cyclopean & Blinding Concrete.
- 32 MPa, for all structural R.C. elements.
Yield Strength of reinforcing steel:
- High tensile steel
- Mild steel
: 420 MPa,.
: 280 MPa, for Mild steel
7- Modeling
Our model is going to be formed and analyzed on Etabs software. To achieve good results
and secure structure, accuracy is indeed. In this paragraph we will explain the algorithm
through modeling process.
i-
Material and Section Definition
Clearly, any structure is composed of its elementary members called structural elements.
Forming a structure means to form its elements first. In Etabs, we define the materials and
elements sections.

Materials used in our
structure are concrete and
steel. Steel is defined by its
yield stress, where it is 42000
t/m2
for
bending
reinforcement and 28000 t/m2
for shear reinforcement.
While concrete has several
i-
parameters:
 Mass= 0.25 t/m2
 Weight= 2.5 t/m3
 f 'c= 2500 t/m2
 modulus of elasticity:
Ec =57000 x sqrt( f 'c psi ) =57000 x sqrt(3626 psi ) = 343237.78 psi = 2413165 t/m2
 Poisson's ratio: ACI sec 19.2.1 recommends that poisson ratio is null for perfectly elastic
isotropic material, we take it 0.2 for mare safety. ( since there is no material perfectly
elastic)

Elements in used structure are grouped into types: frame sections containing beams
and columns, and wall and slab.
i-
Drawing
Drawings including slab layout and columns and walls positions, are going to be imported
from the AutoCAD software to Etabs. Thus we have a model exactly the same as the real
one.
After we insured that walls are
acting as a unit, slabs should also
act as a unit. So we must assign a
diaphragm
to
the
slabs
that
catches the whole slab to its mass
center, so transmit lateral forces
to the vertical-resisting elements.
8- Model Check
Just after finishing the model creation, and running the analysis of the structure, results
are derived. These results must be checked to have a structure adequate to the code's
recommendations. Checks are mainly concern lateral forces and dynamic loads, and the
structure response to these load.
i-
Spectrum Response Analysis
The analysis is done, so we can get the results. When checking the story shears, we must
find that shears due to static load cases (QX and QY), should be equal to that of
dynamic loads (SPEC1 and SPEC2). Etabs results the following table:
Story Load
Loc
P
VX
VY
T
MX
MY
GF
QX1 Bottom
0
-861.8
0
28492.17
0
-37346
GF
QY1 Bottom
0
0
-901.3 -24955.8 38925.8
0
GF SPEC1 Bottom 836.72 553.51 68.26 21099.07 27045.57 27906.38
GF SPEC2 Bottom 838.03 61.55 769.74 23646.8 37418.91 21433.67
Note that VX of QX does not equal to that of SPEC1, also for VY of QY and SPEC2.
Solving this problem is to change the scale factor of the functions defined in the spectrum
case. The new scale factor is going to be modified as follows:

SPEC1:
X-function: scale factor = old scale factor (g/R)
=
3.397.
Z- function: scale factor= 2/3 x X-function scale factor = 2/3 x 3.397 = 2.265.

SPEC2:
Y-function: scale factor = old scale factor (g/R)
=
Z- function: scale factor= 2/3 x Y-function scale factor = 2/3 x 2.555 = 1.703
Running the analysis after changing the scale factors, Etabs gives:
Story Load
Loc
P
VX
VY
T
MX
MY
GF
QX1 Bottom
0
-861.8
0
28492.17
0
-37346
GF
QY1 Bottom
0
0
-901.3 -24955.8 38925.8
0
GF SPEC1 Bottom 1591.75 862.48 116.85 32914.53 51452.83 49341.96
GF SPEC2 Bottom 1198.06 77.05 902.06 27744.23 49127.37 30639.19
Note that VX of QX is equal to that of SPEC1, also for VY of QY and SPEC2.
The response spectrum analysis is in accordance with UBC97
ii-
Period and Convergance
The period is the elastic fundamental period of vibration, in seconds, of the structure in
the direction under consideration. UBC97-sec-1630.2.2 states that the period can be
determined by two methods:
 Method A: T = Ct (hn)3/4
(30-8)

√ ∑
Method B:
∑
(30-10)
In our project, we will consider method A:
Ct = 0.02 as per UBC97 states for bear wall systems
hn = is the distance between the base and the story level in feet. Considering maximum
period, we suppose it will be on the last level, floor 16.then:
hn = 3.15 x 16 x 12 = 604.8 ft
Now T = 0.02 (604.8)3/4 = 2.43 s
Etabs results gives the following table of period of each mode, note that the maximum
period is 2.33s which is approximately equal to the calculated period. Thus the model is
good.
Also ACI-code says that the participating mass in the model shall be at least 90% to
assure convergence, and this condition is assured using 30 modes as shown in the
following table.
Mode
Period
SumUX
SumUY
SumUZ
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
2.332414
1.637249
1.583653
0.659333
0.424169
0.413839
0.329521
0.267101
0.231288
0.219785
0.210394
0.205257
0.191917
0.187803
0.181941
53.8224
53.9477
55.4966
65.8319
65.8319
65.8376
70.3861
70.3861
70.3862
70.3862
71.9396
71.9396
72.0843
72.9041
72.9042
0.0042
0
49.576 0.0058
54.0382 0.0062
54.0382 0.0062
55.063 0.0095
68.4963 0.0486
68.5136 0.0487
68.5802 5.2236
68.6621 5.5975
68.6647 5.6346
68.6647 5.6346
68.8186 6.2408
73.7151 6.2715
74.5093 6.2953
74.5547 41.6235
Mode
Period
SumUX
SumUY
SumUZ
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
0.165011
0.153554
0.145773
0.138037
0.130703
0.115838
0.103682
0.09689
0.088349
0.073711
0.064931
0.060205
0.031684
0.027242
0.024377
72.9137
72.914
72.9668
74.6957
74.7511
74.7512
74.9873
76.7801
76.9062
77.0199
78.2223
82.6731
83.1421
95.8861
96.0941
74.5555
74.5804
74.6184
74.6186
74.6405
77.7486
77.9021
77.9023
79.1748
79.4012
82.086
83.0659
83.2651
83.3165
92.6502
42.139
44.29
47.7438
48.4442
63.3034
63.959
72.1298
73.7942
74.3971
82.5712
83.0557
83.0627
93.6872
94.1491
94.3351
The resulting period is in accordance with UBC97 code
iii-
Story Drift
By definition, UBC97 states that "STORY DRIFT is the lateral displacement of one
level relative to the level above or below. While STORY DRIFT RATIO is the story drift
divided by the story height". This drift results from the application of seismic loads to
the structure.
UBC97 also declared limitations to the story drift. Section 1630.10.2 states that
"Calculated story drift shall not exceed 0.025 times the story height for structures
having a fundamental period of less than 0.7 second. For structures having a
fundamental period of 0.7 second or greater, the calculated story drift shall not exceed
0.020 times the story height."
As our structure has a period 2.3 > 0.7 s, then the limit will be:
Story Drift < 0.02 x story height
The following table shows the drifts resulting from the Etabs analysis:
Story
STORY9
STORY9
STORY9
STORY9
STORY8
STORY8
STORY8
STORY8
STORY7
STORY7
STORY7
STORY7
STORY6
STORY6
STORY6
STORY6
STORY5
STORY5
STORY5
STORY5
STORY4
STORY4
STORY4
STORY4
STORY3
Item
Max Drift X
Max Drift Y
Max Drift X
Max Drift Y
Max Drift X
Max Drift Y
Max Drift X
Max Drift Y
Max Drift X
Max Drift Y
Max Drift X
Max Drift Y
Max Drift X
Max Drift Y
Max Drift X
Max Drift Y
Max Drift X
Max Drift Y
Max Drift X
Max Drift Y
Max Drift X
Max Drift Y
Max Drift X
Max Drift Y
Max Drift X
Load
SPEC1
SPEC1
SPEC2
SPEC2
SPEC1
SPEC1
SPEC2
SPEC2
SPEC1
SPEC1
SPEC2
SPEC2
SPEC1
SPEC1
SPEC2
SPEC2
SPEC1
SPEC1
SPEC2
SPEC2
SPEC1
SPEC1
SPEC2
SPEC2
SPEC1
Point
1115
1151
1115
943
1115
1151
1115
943
1115
1151
1115
943
1115
1151
1115
943
1115
1151
1115
943
1115
1151
129
943
1115
DriftX
0.002385
DriftY
0.000942
0.000505
0.002048
0.00245
0.000961
0.000522
0.002052
0.002481
0.000966
0.000529
0.002026
0.002467
0.00095
0.000525
0.001959
0.002392
0.000914
0.000507
0.001839
0.002236
0.000851
0.000592
0.00165
0.001968
STORY3
STORY3
STORY3
STORY2
STORY2
STORY2
STORY2
STORY1
STORY1
STORY1
STORY1
GF
GF
GF
GF
BASE 1
BASE 1
BASE 1
BASE 1
BASE 2
BASE 2
BASE 2
BASE 2
Max Drift Y SPEC1
Max Drift X SPEC2
Max Drift Y SPEC2
Max Drift X SPEC1
Max Drift Y SPEC1
Max Drift X SPEC2
Max Drift Y SPEC2
Max Drift X SPEC1
Max Drift Y SPEC1
Max Drift X SPEC2
Max Drift Y SPEC2
Max Drift X SPEC1
Max Drift Y SPEC1
Max Drift X SPEC2
Max Drift Y SPEC2
Max Drift X SPEC1
Max Drift Y SPEC1
Max Drift X SPEC2
Max Drift Y SPEC2
Max Drift X SPEC1
Max Drift Y SPEC1
Max Drift X SPEC2
Max Drift Y SPEC2
Maximum drift
1151
163
943
1115
1151
1115
943
1115
1151
1115
1151
1438
1186
1438
200
1361
1186
15
200
1361
1186
15
200
0.000761
0.000436
0.001389
0.001511
0.000629
0.00034
0.000993
0.000738
0.00043
0.000244
0.000496
0.000128
0.000062
0.000042
0.000173
0.00001
0.000006
0.000007
0.000026
0.00001
0.000006
0.000007
0.002481
0.000026
0.002052
Now we will check
Story Drift < 0.02 x story height
We need to define: ΔS: elastic response displacement, etabs gives ΔS/h.
ΔM: inelastic response displacement which should be checked,
where ΔM= 0.7R ΔS
The check then is going to be as ΔM < 0.02 (since ΔM is already divided by story
height)
ΔS/h = 0.002481 m, then ΔM/h = 0.7 x 4.5 x 0.002481 = 0.0078
0.0078 < 0.02 ok
Then story drifts of our structure are allowed by UBC97 code.
iv-
Story Displacement
ASCE-code provide that story displacements due to wind load must not exceed the total
height of the structure divided by 500. Getting story displacement tables from Etabs, gives
us the maximum value of story displacement which is 0.0125 meters.
The height if the building is 64 meters, divided by 500 it becomes 0.128. Note that
0.0125<0.128, thus the structure is approved for wind loads.
v-
BWS-system Applicability
As we consider the Bearing Wall System (BWS) to resist lateral forces, then columns shall
not carry more than 10% of the total shear present at the level. Taking the least level
(basement), we calculate the percentage of the carried shear by columns to the total shear.
Results can be summarized by the following tables:
V2
V3
1.64
4.26
QX1
352.57 -149.96
BASE 1
PERCENTAGE 0.465156 2.84076
V2
V3
0.84
4.44
QX2
352.92
-164.29
BASE 1
PERCENTAGE 0.238014281 2.70254
V2
V3
-1.94
-55.5
QY1
-205.35 2517.21
BASE 1
PERCENTAGE 0.944729 2.20482
V2
V3
-0.44
-55.9
QY2
-205.91
2543.67
BASE 1
PERCENTAGE 0.213685591 2.19761
All percentages are less than 10% then the assumption of BWS is allowed.
vi-
Eccentricity Check
This check is done to know whether we are supposed to consider or ignore torsion
reinforcement. Let us define some terms:
ex = X-center of mass – X-center
of rigidity.
Story
XCM
YCM
XCR
YCR
ex
ey
STORY9
25.54
32.667
25.752
28.732
-0.212
3.935
STORY8
25.54
32.667
25.722
28.415
-0.182
4.252
STORY7
25.54
32.667
25.684
27.971
-0.144
4.696
STORY6
25.54
32.667
25.636
27.326
-0.096
5.341
Lx = length of slab in X-direction.
STORY5
25.54
33.593
25.574
26.35
-0.034
7.243
STORY4
25.563
31.537
25.489
24.806
0.074
6.731
LY = length of slab in Y-direction.
STORY3
25.562
31.415
25.364
22.207
0.198
9.208
STORY2
25.54
32.457
25.161
17.233
0.379
15.224
STORY1
23.423
25.24
24.961
11.162
-1.538
14.078
GF
23.114
29.546
25.153
27.442
-2.039
2.104
BASE 1
23.685
29.685
25.461
27.217
-1.776
2.468
BASE 2
24.733
31.019
24.799
27.07
-0.066
3.949
0.379
15.224
eY = Y-center of mass – Y-center
of rigidity.
The condition is that if
and
then torsion
reinforcement is to be ignored,
and V.S. Etabs results the
adjacent table.
Maximum e
Taking maximum eccentricity:
X:
Y:
Torsion is considere
9- The Structural Analysis
3D View
Floor Slabs
Basement and Ground
Tipical
10- Summary of Reinforced Concrete Design of Vertical Elements
Columns
rebar
percentage
Walls rebar percentage at GF
Walls rebar percentage at First floor
Core rebar percentage
11- Slab Design
Slabs are first structural element that caries the direct load then transports it to beam (if
exist) then columns. Slabs mainly caries moment and shear forces, and its designed to resist
these forces, taking into consideration that slabs take no lateral forces thus it will only be
affected by gravity loads. Slabs design will pass in several steps to give its results: section
and reinforcement.
i.
Pre-dimensioning:
In our project we shall use two way flat plate slab since the span length ranges
between 6 and 7 m. So a flat plate of thickness 25 cm was our choice as the
minimum thickness for deflection control.
In case of no drop panels, 420 MPa, exterior panel,
h = 25 cm < l / 30 =27 cm – ACI_318M-05 table 9.5(c)
ii.
Loads:
 Self-weight: dead load computed by the program, with density of concrete
2.5 T/m3.
 Super imposed dead load: uniform load formed of partition (0.2T/m 2) and
finishing (0.2T/m2) on pedestrians floors while in parking floors 0.2T/m 2.
 Live load: (0.25T/m2)
iii.
Load combinations:
 Service combination: DL+LL
 Sustained load combination: DL+0.4 LL
 Ultimate combination: 1.2 DL+1.6 LL
iv.
Punching shear:
The punching shear is checked on a critical section at a distance of d/2 from the face
of the support (ACI_318M-05 11.12.1.2).
For rectangular columns and concentrated loads, the critical area is taken as a
rectangular area with the sides parallel to the sides of the columns or the point loads
(ACI_318M-05 11.12.1.3).
A design example will be done on basement 1
v.
Punching:
Punching ratios Vu/ϕVc are given by safe software. Notice that all ratios are less
than one, which is the condition for approval of punching for columns.
vi.
Deflection check :
Deflections appear in two manners: short term and long term deflections. Short term
deflections are due to the immediate application of live loads, while long term
deflections are due to effect of the sustained loads. The following diagram is a typical
example of deflections.

Taking basement 1 as an example, the maximum values of long term and short term
deflections are as follows:
1. DL deflection: 1.894 mm
2. Service load deflection: 2.234 mm
3. Sustained load deflection: 2.997 mm
Deflection limitations are provided by ACI_318M-05 table 9.5(b)
 Short term deflection = def. (ser.) – def. (dead)
< l/360 = 23.88mm
 Long term deflection = λDL.def (dead) + λsus. (def. (sus.) - def. (dead))
=5.34 mm < l/240 = 35mm
Where:
λDL=
, (t =2 for five years ACI_318M-05 9.5.2.5) (ACI_318M-05
9.11)
λsus=
vii.
,
(t=1.2 for 6 month ACI_318M-05 9.5.2.5) (ACI_318M-05
9.11)
While ρ’ = 0.002, minimum compressive reinforcement in slabs.
Reinforcement:
Minimum reinforcement in SLAB is shrinkage and temperature steel which is for
grade 60 (420MPa) = 0.0018bh = 4.5 cm2 (4T12/m) - ACI_318M-05 10.5.4 and
7.12.2.1.
Reinforcing the slab with minimum reinforcement, we now search for any needed
additional steel.

Additional top and bottom reinforcement to 5T12/m (5.65 cm2) at top and
5T14/m (7.7cm2)
No additional bottom reinforcement needed to (5T14/m)
Special structures
i.
Stair case
a) Stairs are common elements that are found almost in all
structures made of several floors. Stairs may differ due
to its span and assigned load. Being in a public
structure, the stairs are supposed to carry high loads,
0.25 t/m2 as super imposed dead loads and 0.48 t/m2 as
live loads. It sufficient to define only teo load
combinations, strength combination (1.2DL + 1.6LL)
and working stress combination (1.0DL + 1.0 LL).
The plan dimensions of the stairs are as shown in the
adjacent figure.
b) Design:
Stairs will be treated as one way slab supported on beams.
 Supporting beam: two identical beams support the stairs, then each one carry half the
load.
DL= 0.25 x 2.2 = 0.55 t/m
LL= 0.48 x 2.2 = 1.056 t/m.
The results are as follows:
.
Shear and deflections (Note that deflection is L/544 < L/360) are ok, the required steel area is 4.09
cm2 then we can use 3T14@ 10 cm

Stairs
Also stairs defined on BeamD as beam of 125 cm width and 17 cm depth.
DL= 0.25 x 1.25 = 0.3125 t/m
LL= 0.48 x 1.25 = 0.6 t/m
The results are as follows:
Shear and deflections (L/1209 < L/360) are ok, the required steel area is 6.15 cm2 then we can use
6T12@ 20 cm
ii.
Ramp:
Ramp is considered as a one way 25 cm thick slab supported on its adjacent shear walls.
Main reinforcement will be as joining the walls. In the second way minimum
reinforcement will be added.
Live load is to be considered 0.24 t/m2, while super imposed dead loads are null.
It is defined as one meter width, 25 cm thick slab pinned on the walls. The span equals to
6.6m.
DL= (2.5 x 0.25) x 1 = 0.825 t/m
LL= 0.24 x 1 = 0.24 t/m.
The next figure shows that shear is ok for this section (25 x 100 cm), then use T8@20
cm as stirrups. Steel area is 8.33 cm2, then we use 5T16 @20cm per meter.
Reinforcement in the second direction is going to have area as temperature steel
requirements:
As2= 0.0018 x b x h = 0.0018 x 100 x 25 = 4.5 cm2, then use 5T14 @ 20cm per meter.
12- Footings Design
Any structure is going to be supported by structural elements that carries gravity loads to
the ground, it is footings. The depth of footings depends on the supported load and column
(or wall) size, while its dimensions are related to soil strength. (Actually soil strength is
related to foundation dimensions)
After several iterations, depth and dimension of footings are determined and shown in the
following report. Three types of footings is used in our project: isolated footings, combined
footings, and mat foundation.
I - Supporting Soil
The soil present in the project location is of sand nature, where it is of 30 t/m2 bearing
capacity. Excavating for 14 meters, we can say that the soil at this level is compacted. Thus
the new bearing capacity can be considered as:
B.C. = 30 + 14 x 1.8 (density) = 54 t/m2.
Designing on "safe" software, we have to define the soil subgrade modulus instead of
bearing capacity. A simple relation can transform the bearing capacity to subgrade
modulus:
Subgrade Modulus= Bearing Capacity x 120 = 54 x 120 = 6480 t/m3.
II- Mat Footing
As seen in the adjacent figure, since we have a lot of walls and columns locate near to each
other, and due to the large loads it carry, a mat footing is made to carry these loads.
This mat, and due to different loads will not be of uniform thickness. Columns and walls
carrying much loads need more thickness of foundation, to comply with punching limits
determined by ACI-code. The dominant thickness is 1 meter, while some regions need more
depth. The next figure will show the differences in raft thickness.
Loads applied on Raft foundation
Reaction of Soil pressure
X-Top Reinforcement
X-Bottom Reinforcement
Y-Top Reinforcement
Y-BOTTOM Reinforcement
III- Isolated Footings
The dimensions of such type of footings is determined such that its soil reaction is smaller
than soil capacity to avoid settlement. On the other hand, footing depth is determined to
support punching shear up to ACI-code section 11.11.2.1:
Eq (11-31)
(
) √
Where β = long side / short side
λ= 1 for normal weight concrete
b0= perimeter of the projection of the offset of the column by d/2.
Applying Vu < ψ Vc we can determine the depth "d".
Defining the footings on "safe", and assigning the loads and supports, then running the
analysis, we get the following results. Footings are named up to their depth in cm.
df
13- The Microsilica in Concrete
In our project, the demanded high strength structure necessitates the usage of durable concrete. In
order to attain durability, concrete is mixed with microsilica. The later particles is very smaller in
size than those of concrete, thus allowing it to react with the cement particles to strengthen the
bond within each other, and thus prohibiting the passage of water particles through the voids that
may generate in concrete. The induced strength in concrete provide additional ability of it to resist
sulfate attacks subsequently after the voids are filled with microsilica.
Therefore we found that microsilica is an eligible subject to be discussed in the following section.
Microsilica is a mineral admixture composed of very fine solid glassy spheres of silicon
dioxide (SiO2). Most microsilica particles are less than 1 micron (0.00004 inch) in diameter,
generally 50 to 100 times finer than average cement or fly ash particles.
Frequently called condensed silica fume, microsilica is a by- product of the industrial manufacture
of ferrosilicon and metallic silicon in high-temperature electric arc furnaces. The ferrosilicon or
silicon product is drawn off as a liquid from the bottom of the furnace. Vapor rising from the 2000degree-C furnace bed is oxidized, and as it cools condenses into particles which are trapped in huge
cloth bags. Processing the condensed fume to remove impurities and control particle size yields
microsilica.
A- Work of microsilica in concrete
Microsilica in concrete contributes to strength and durability two ways:
-As a pozzolan, microsilica provides a more uniform distribution and a greater volume of hydration
products.
-As a filler, microsilica decreases the average size of pores in the cement paste.
Microsilca’s effectiveness as a pozzolan and a filler depends largely on its composition and
particle siz which in turn depend on the design of the furnace and the composition of the raw
materials with which the furnace is charged. At present there are no U.S. standard specifications
for the material or its applications.
Dosages of microsilica used in concrete have typically been in the range of 5 to 20 percent by
weight of cement, but percentages as high as 40 have been reported.
Used as an admixture, microsilica can improve the properties of both fresh and hardened concrete.
Used as a partial replacement for cement, microsilica can substitute for energy-consuming cement
without sacrifice of quality.
A.1-Pozzolanic action
Addition of microsilica to a concrete mix alters the cement paste structure. The resulting paste
contains more of the strong calcium-silicate hydrates and less of the weak and easily soluble
calcium hydroxides than do ordinary cement pastes. Because the microsilica particles are so
small—their average diameter is about 1⁄100 that of cement particles—they disperse among and
separate the cement particles. The resulting fine, uniform matrix can give markedly higher
compressive, flexural, and bond strength. Compressive strengths as high as 15,000 psi with
ordinary aggregates and 30,000 psi or more with special aggregates have been reported.
Relation ship between strength and water-cement ratio for
two microsilica concretes and a reference concrete. Curves
are similar in shape, but microsilica concretes reach
significantly higher levels, up to nearly 14,000 psi .
A.2-Freeze-thaw durability
The small microsilica particles are very good at infiltrating and plugging capillary pores in
concrete— making pores smaller and fewer and concrete more dense. This gives the concrete good
resistance to freezing and thawing. Air entrainment improves the resistance of microsilica
concrete in the same way it does ordinary concrete. However, microsilica concrete even with
relatively low cement content can reportedly be compounded to be frost resistant without airentraining agents.
Comparison of compressive strengths of a proprietary microsilica concrete and a low-slump dense
concrete without microsilica, both compounded for bridge deck overlays. Early strength of the
microsilica concrete is lower. But after two days, values are about equal. After 28 days, microsilica
concrete is about 40 percent stronger and after 56 days, 50 percent stronger.
A.3-Protection of reinforcement
Concrete’s ability to protect embedded steel against corrosion depends mainly on the alkalinity of
the pore water. As long as the water is highly alkaline, a passive oxide film on the steel protects it.
If the passivity is destroyed by aggressive ions, either carbonates or chloride ions, the steel will
corrode at a rate depending on the concrete’s electrical resistivity and rate of oxygen transport
through water- saturated concrete.
Fortunately, microsilica thanks to its pore-filling capabilities reduces (in some if not all cases) the
rate of carbonation, decreases permeability to chloride ions, imparts high electrical resistivity, and
has little effect on oxygen transport. Therefore, microsilica concrete can be expected to be strongly
protective of reinforcement and embedments.
A.4-Sulfate resistance, reduced aggregate reactivity
Probably because it has a finer pore structure and less calcium hydroxide, microsilica concrete
has improved resistance to sulfate attack . In addition, microsilica binds the potassium and sodium
oxide alkalies present in cement, thus reducing detrimental effects with alkali-reactive aggregates.
A.5-Aids strength gain of fly ash concretes
Preliminary indications suggest that microsilica may be useful in controlling heat generation in
mass concrete. It has also been found useful in combination with fly ash. Early-age strength
development of concrete in which fly ash replaces cement tends to be slow because fly ash is
relatively inert during this period of hydration. Adding microsilica, which is more reactive in early
hydration, can speed the strength development.
B-Mixing and placing considerations
B.1-Handling the microsilica
Because of its extreme fineness, microsilica presents handling problems. A cement tanker that
could ordinarily haul 35 metric tons of cement accommodates only 7 to 9 tons of dry microsilica
and requires 20 to 50 percent more time for discharging. Some producers mix microsilica with
water on a pound-for-pound basis to form a slurry that is transportable in tank trailers designed to
handle liquids. The water of the slurry replaces part of that ordinarily added to the mix.
One supplier prepares a slurry which, used at the rate of 1 gallon per 100 pounds of cement, will
provide about 5 percent microsilica by weight of cement. In 1984, that supplier was quoting a price
of $1.70 per gallon at a plant in West Virginia. In Canada, patented methods have been used to
densify the microsilica for shipment to ready mix producers. Some concrete producers also use the
loose microsilica just as it is collected.
B.2-Water requirements of the mix
When no water reducing agent is used, the addition of microsilica to a concrete mix calls for
more water to maintain a given slump. Water content can be held the same by using a water
reducer or superplasticizer along with the microsilica. Water reducing agents appear to have a
greater effect on microsilica concrete than on normal concrete. Thus water demand for a given
microsilica concrete can be controlled to be either greater or smaller than for the reference
concrete.
B.3-Placing and finishing, curing
The gel that forms during the first minutes of mixing microsilica concrete takes up water and
stiffens the mixture, necessitating adjustment of the timing of charging and placing. Scandinavian
researchers have concluded that microsilica concretes often require 1 to 2 inches more slump than
conventional concrete for equal workability. When cement content and microsilica dosage are
relatively high, the mixture is so cohesive that there is virtually no segregation of aggregates and
little bleeding. This may cause problems for floors or slabs cast in hot, windy weather because there
is no water film at the surface to compensate for evaporation.
Plastic shrinkage cracking can readily develop unless precautions are taken. It is important to
finish the concrete promptly and apply a curing compound or cover immediately. With lean
concrete mixes or mixes containing fly ash replacement of cement, different effects
have been reported. For example, Reference 4 reports that mixes with less than 380 pounds of
cement per cubic yard plus 10 percent microsilica are both more cohesive and more plastic so no
extra water is needed to maintain slump.
B.4-Concrete color effects
Freshly mixed concrete containing microsilica can be almost black, dark gray, or practically
unchanged, depending on the dosage of microsilica and its carbon content. The more carbon and
iron in the admixture, the darker the resulting concrete. Hardened concretes are not much darker
than normal concretes when dry. Sometimes there is a faint bluish tinge, but when the microsilica
concrete is wet, it looks darker than normal.