the effect of architect shape of building under seismic load
TRANSCRIPT
International Journal of Engineering & Technology IJET-IJENS Vol:20 No:02 14
202602-5353-IJET-IJENS © April 2020 IJENS I J E N S
The Effect of Architect Shape of Building under
Seismic Load Luma Ahmed Aday 1*, Mohammed Ghazi Abbas 1, Yasir W.Abduljaleel 1
1 Al-Iraqia University/ Collage of Engineering / Iraq
*Corresponding author E-mail: [email protected]
Abstract-- The main objective of the research is to identify the
least earthquake-affected architectural forms as well as the
desired building behaviour during earthquakes. To achieve
these goals, we must understand the behaviour of the materials
involved in construction. The ductile materials are more
resilient to earthquakes, while brittle materials are less
refractive and less resistant to earthquakes. The project
involves analysis and designs a multistoried building (3-
Dimensional frame) with architectural forms different for
buildings using the parameters for the design as per the UBC-
97 SAP2000 software and by adopting a Time History Analysis
Method. There are several factors which affect the behaviour
of building and Play a key role in understanding the behaviour
of structure including storey drift and displacement, which
have been studied in this research and results are expressed in
form of graphs.
Index Term-- Seismic Effect, Displacement, Storey Drift,
Analysis & Design by SAP2000.
1. INTRODUCTION
Earthquake experiments have shown that a lots traditional
buildings and building ways do not have the basic resistance
to seismic forces. Also follow Simple rules will not block
harm in mild or big earthquakes, but prevention of collapse
and repairable harm should be restricted ratio. Where some
general rules stand out resistant design for earthquake [1]:
Must be the building well connected to a good the earth
and foundation.
Commitment to provide in both directions as well as
from top to bottom, resistive components such as
bracing or shear walls equally across the construction.
All materials used must be of ideal quality and must be
shielded against insects, rain, sun and other weakening
measures so that they do not lose their power.
Not used Structures brittle or which collapse suddenly.
Rather, they should be strong. As categorized structural
components based on the form-efficiency connection. Its
aim is to assist in understanding the role of structural
components in determining full structure performance.
2. INERTIA FORCES IN BUILDINGS AND STRUCTURES
Ground vibration generates ground motion on the base of
buildings and installations. The movement of the base of the
building with the direction of the movement of the ground,
but the ceiling has a tendency to stay in its original position
(According to Newton's first law) [2].
This is very similar to the case of the passenger standing in
a moving device at its sudden start, as the legs move, but the
upper part of the body tends to stay in the back which leads
to fall back!! This phenomenon to continue to stay in the
previous situation known as the phenomenon of inertia,
although the walls and columns may behave ductile, the
behavior of the roof will differ from the behavior of those
elements affected by the ground motion as in Fig. 1.
According to Newton's Second Law of Motion , F = m × a )
Assuming that the mass of the ceiling is equal to m and is
subjected to a land acceleration equal to a ( [2] ,the inertial
force F1 is the mass of the ceiling m multiplied by the earth
acceleration time and its direction opposite the earth
acceleration, Here, it is clear that increasing the mass means
an increase in inertia force, which means that lightweight
buildings have the ability to withstand ground vibration
better than heavyweight buildings.
3. DUCTILITY AND DAMAGEABILITY
The buildings resistant to earthquakes, especially the main
elements, prefer to be built of ductile materials. Such buildings
have the ability to swing forward and backward during
earthquakes; Ductility and damageability are among the desired
earthquake-resistant design characteristics. Ductility is a notion
interrelated with the capacity of the structure to afford
significant deformations without collapse [1]. The parts must
be proportioned in order to achieve a ductile impact in the
component's behaviour so that they come into contact and are subjected to yield [3]. Therefore, adequate ductile materials at
points of tensile stress are a necessity for a good earthquake-
resistant design, Fig. 2 shows this Some materials are ductile,
such as forged iron, steel and wood, other materials are not
ductile (this is called brittle), such a simple masonry, cast iron
and concrete, that is, they suddenly break without warning [4].
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Fig. 1. The effect of inertia on buildings when exposed to vibration at their base.
Damageability: indicate to the ability of a structure afford large
damage, without partial or total collapse [2]. This is good
because those structures can ingest more damage, and also it permits the deformations to be observed and repaired, prior to
collapse [5].
Fig. 2. Ductility buildings are designed and detailed to develop favourable
failure mechanisms.
4. BASIC IDEA TO ACHIEVE RESISTANT EARTHQUAKE
PERFORMANCE
The basic idea is to make the building shape as regular and to
ensure its structural frame, where the construction is
unbalanced in terms of height or plan, is prone to the
earthquake damage, The RC frame take part in resisting the
earthquake and gravity forces as illustrated in Fig. 3 [1, 3].
Whereas load due to contents and self-weight on buildings cause RC frames to curvature, also the buildings with
symmetrical Shape such as the rectangle, cross and Z-shaped
structures shown in Fig. 4 are structures that do not generate
torsion owing to eccentricity, since the middle of gravity and
the center of stiffness correspond, while structures with forms
T, L, U and arc-shaped structures are unbalanced structures that
generate high torsion owing to eccentricity between the middle
of gravity and the center of stiffness [6].
Fig. 3. Earthquake vibration reverses tension and compression in members
– reinforcement [3].
On the other hand observed the shorter columns in Reinforced
concrete frame structures with columns of varying heights on
one floor suffer harm compared to larger columns on the same
floor, where the short column is stiffer than the long column.
Stiffness of the column is its resistance to deformation the result of exposure to large Strength needed to deform it. If the
brief column is not intended for such a big force, during an
earthquake it may suffer eloquent damage [3]. This conduct is
called the "short effect of the column" as in Fig. 5.
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Fig. 4. Construction form and center of gravity and center of rigidity.
Fig. 5. Short columns are stiffer during earthquakes and attract bigger forces.
5. BUILDING DRIFT CAUSED BY LATERAL FORCE
The horizontal displacement that happens for building is
called drift. Because of resulting stress in structural and
non-structural seismic elements which it renders them in
distorted shapes, where Maximum drift commonly occurs at
the top of a building, but each story level is subjected to
story drift as shown in Fig. 6 [7].
The building codes specify maximum drift boundaries and
story drift limits to regulate a building's displacement during
an earthquake. Due to the rise in drift and acceleration to the
top of a construction, drift is considered important for the
columns and connections of heavy prefabricated cladding parts whose failure could result in harm. So all structural
seismic elements must be designed to avoid failure and to
containment the expected drift.
Fig. 6. Drift in a building subjected to lateral earthquake forces.
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6. LITERATURE REVIEW
Sazzad M. and Azad [8] Studied the impacts of building
shape on drift and displacement owing to wind and
earthquake loads by the Bangladesh National Building Code
(BNBC), It found that, Maximum displacement and
maximum floor drift owing to earthquake in construction
shape type C, and Rectangular Building with hollow room,
is the safest model taking into account all circumstances.
Pawade et.al. [9], presented a paper to study the structural
behavior of multistory RC Structure for different plan
configuration such as rectangular building along with L- shape and C- shape and H-shape in accordance with the
seismic provisions suggested in IS: 1893-2002 using
STAAD Pro V8i. They found Maximum storey drift is
occurring on top storey of L-shape building while the
minimum storey drift occur on Rectangular shape of
building. Maximum bending moment in H-shape of
building. Result has been proved that C-Shape building is
more vulnerable compare to all other different shapes of
building.
Ravi V.S. and Lekshmi S. [10], Through their studies on a
building with a single regular plan and an irregular plan (C,
E, H, L, T, PLUS shapes), the Building with a regular square plan has the same maximum base shear value
compared to other plan shapes and the lowest base shear
value for the ' L ' shaped plan, static and dynamic analysis
performed on a computer with the help of the STAAD-Pro
software using the parameters. For the design as per IS-
1893-2002-Part-1, as well as for the Regular Square
Building, there is a minimum displacement and a maximum
displacement "L" shape compared to other shapes.
7. TIME HISTORY ANALYSIS
Dynamic analysis using the time history method calculates
the response of the building at discrete times using discrete recorded time history as the basis movement, Time History
analysis has been carried out using the Elcentro earthquake
record of May 18, 1940; it is a detailed analysis in which
response is calculated for each time step. It requires more
time but gives a good result.
Steps for using Time History method of analysis in SAP
2000: Step 1: Defining the time history function by adding a
function from file, the Elcentro earthquake record as shown
in Fig. 7. Step 2. Defining the target response spectrum.
Step 3. Assigning time history as a load case. Step 4. Next
run the analysis and get the result.
Fig. 7. Defining time history function (Elcentro, 1940).
8. DETAILS OF THE MODELS AND ANALYSES
To study the effect of shape configure ration we have
developed 4 models in SAP2000 software. Various types of
input data to model the all the 4 models were kept same to
obtain the predicted behavior, total numbers of storeys are 7
for all types of buildings frames. The elevations are same for all the 4 models as shown in Fig. 7. The specifications of
models are shown in Table 1, The buildings consist of 400
mm x 400 mm square columns, all 450 mm x 250 mm size
beams. The elasticity module and concrete compression
strength were taken as E = 3.05 ×107 kN/m2 and fc =
41Mpa. The SAP2000 finite element analysis software is
used to create a 3D model and perform all analyzes. The
software can predict the geometric conduct of space frames
under static or dynamic loads, accepting static loads (either
forces or displacements) and has the ability to perform
eigenvalues, The self-weight of beams and columns (frame members) are calculated automatically, by the program.
And the seismic load values were calculated as per UBC-97
[11, 12].
Table I
Details of buildings components.
Buildings Components Details
Beam 450×250mm
Column 400×400mm
Floor Height 3m
Total Height 21m
-0.4
-0.2
0
0.2
0.4
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Acc
ele
rati
on
(m
/s)2
Time (s)
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(a) 3D Elevation and plan of Rectangular Building.
(b) 3D Elevation and plan of Z- Shape Building.
(c) 3D Elevation and plan of U-Shape Building.
(d) 3D Elevation and plan of Cylinder Building.
Fig. 8. Types of buildings frame.
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9. ANALYSIS RESULTS
In this research we done compared analysis results Storey Drift
and Displacement for models .whereas can easily observe the
performance of building and we can predict the good building
frame which performs well against earthquake forces. The
analysis results showed the displacement for 4 buildings as
shown Figs. 9-12 , where Peak roof displacement of rectangle
building which obtained from time history analysis in SAP2000 is 9.2 mm, while Peak roof displacement of z-
building reached 9.1 mm and Peak roof displacement recorded
for u-building and cylinder building were 10.2 mm, 9.6 mm
Respectively.
Fig. 9. Displacement time history of top rectangle shaped.
Fig. 10. Displacement time history of top floor– floor–Z shape.
Fig. 11. Displacement time history of top floor –U shape.
Fig. 12. Displacement time history of top floor –Cylinder.
Fig. 13 and Table 2 are showing that for the rectangle building
the base shear is bigger than for other buildings. As higher
stiffness of building results in substantially higher base
shear[12] ; while Z-building have less base shear .
Table II
The result of the SAP2000 analysis of the shear base (KN).
-10
-5
0
5
10
0 5 10
Dis
pla
cem
en
t (m
m)
Time (s)
-10
-5
0
5
10
0 5 10
Dis
pla
cem
en
t (m
m)
Time (s) Rectangle
Shape Z-Shape U-Shape
Cylinder
Shape
327 237 252 283
-10
-5
0
5
10
0 5 10
Dis
pla
cem
en
t (m
m)
Time (s)
-10
-5
0
5
10
0 5 10
Dis
pla
cem
en
t (m
m)
Time (s)
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Fig. 13. Base shear time history; 4 models building.
Drift story is a very complicated point in structural engineering.
Large story drifts affect the structural elements, Design For the
moment frame structures have requirements to confirm the
ability of the structure to maintain inelasticity resulting from
deformation and drift. If the deflections of any structure
become too large, (P-Δ) effects may cause instability of the
structure and cause collapse of the structure. [12,
13].According to UBC97 story drifts shall be computed using
the maximum inelastic response displacement, Story Drift
Limitation was calculated the following equation and which
illustrated by the Fig. 14.
∆𝑀= .7 𝑅 ∆𝑆 (1)
Where; ∆S:: Design Level Response Displacement, R: is the
structural system coefficient (8.5) from (table K-16) [11].
Of the conditions for structure with a period less than 0.7
seconds, the maximum story drift is limited to;
∆𝑚 ≤ 0.025ℎ (2)
While for structure with a period greater than 0.7 seconds;
∆𝑚 ≤ 0.02ℎ (3)
Where, h is the story height; the structure period was calculated
using formula 4, was the result T = 0.29, this formula may be
used for all framing systems.
𝑇 = 𝐶𝑡(ℎ𝑛)3
4⁄ (4)
Defined Ct= 0.030 for concrete moment frames, hn = the height of the building [11].
Fig. 15 show that the buildings shapes does corresponds to the
seismic code requirement; the inter storey drifts don't exceed
the inter storey limitation provided by the seismic code and
shown the convergence of results among the four buildings, the
maximum design inter-story drift are reached 1.7 mm , 1.19
mm at third storey for Z building and U- building, respectively
for design story drift ratio can calculation from relative
difference of displacement between the top and bottom of a
story, divided by the story height, the Fig.14 shows story drift
ratio for all buildings.
-400
-300
-200
-100
0
100
200
300
400
0 1 2 3 4 5 6 7 8 9 10 11
Bas
e S
he
ar (
KN
)
Time (s)
rectangle shape
U-Shape
Cylinder Shape
Z-Shape
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Fig. 14. Drift Limitation (mm) vs. Storey level.
Fig. 15. Drift ratio vs. Storey level.
10. CONCLUSION
The objective of this study has been to analyse seismic
effects between various shape buildings and to watch the
structural behaviour:
The maximum displacement due to the earthquake is observed in the U-shaped building whereas building
Z, rectangle and cylinder shapes buildings were record
the results of converging displacement.
The disparate story drift results are observed for the Z
and U buildings at the first, second and third storey
and become converging at the storey levels last
whereas the rectangle and cylinder shapes buildings
analysis result were regular for all storey levels.
Base shear is calculated by using time history analysis for all four buildings in the Fig.13 illustrate
the comparison of base shear. The lower base is
getting in Z-shape building and the higher base shear
is getting in rectangle shape building.
Result has been proved that rectangle and cylinder
shapes buildings better behave during earthquakes
compared to Z and U shapes of building.
1, 0.35
2, 0.83
3, 1.19
4, 1.19 5, 1.19
6, 0.59 7, 0.59
1, 0.83
2, 0.95
3, 1.78
4, 0.59 5, 0.59
6, 0.237, 0.23
1, 0.83
2, 0.95
3, 1.19
4, 0.59 5, 0.596, 0.29
7, 0.17
1, 0.89
2, 0.893, 1.07 4, 0.83 5, 0.83
6, 0.597, 0.23
0 1 2 3 4 5 6 7
Rectangle shape Z-shape U-shape Cylinder shape
1, 0.002
2, 0.004
3, 0.006
4, 0.0065, 0.006
6, 0.003 7, 0.003
1, 0.004
2, 0.005
3, 0.001
4, 0.0035, 0.003
6, 0.00137, 0.0013
1, 0.004
2, 0.005
3, 0.006
4, 0.0035, 0.003
6, 0.0016
7, 0.001
1, 0.005 2, 0.005
3, 0.006
4, 0.004
5, 0.003
6, 0.002
7, 0.0013
0 1 2 3 4 5 6 7
Rectangle Shape Z-Shape U-Shape Cylinder Shape
International Journal of Engineering & Technology IJET-IJENS Vol:20 No:02 22
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ACKNOWLEDGEMENTS We would like to present many thanks of gratitude to
colleagues who helped to complete this project within the
limited time. The authors declare that they have no
conflict of interest.
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