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Comparison of UBC-1997 And IBC-2021 For Earthquake Resistant Design of
High Rise RCC Building
Conference Paper · February 2023
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2nd International Conference on Advances in Civil and Environmental
Engineering (ICACEE-2023)
University of Engineering & Technology Taxila, Pakistan
Conference date: 22nd and 23rd February, 2023
Comparison of UBC-1997 And IBC-2021 For Earthquake Resistant Design of High Rise
RCC Building
Asad Ullah Khan, Adil Khan
University of Engineering & Technology Peshawar, Pakistan
asadullahk636@gmail.com, 18pwciv5027@uetpeshawar.edu.pk
Warda Zulhaj, Salwa Shaheen, Muhammad Ali Raza, Mohid Irfan
wardazulhaj2000@gmail.com, civilianuet222@gmail.com, tkhcollege786@gmail.com
18pwciv5184@uetpeshawar.edu.pk
ABSTRACT
This manuscript covers a study on the comparison between different aspects of reinforced concrete
buildings designed according to two different codes in the specific seismic zone. The dimensions,
configurations, and material properties are selected according to the usual practice in the area. For
the purpose of this study, two to ten-story buildings were selected. The numerical models of
selected reinforced concrete buildings were prepared in the finite element method-based software
ETABS (Version 19). The seismic analysis and design of these structures were carried out for
seismic zone 2B of UBC-97 and risk category III of IBC-21. After this, the design optimization
study and cost comparison analysis has been done. The manuscript provides an idea about two
different building codes i-e UBC-97 and IBC-21.
KEYWORDS: ETABS, UBC-97, IBC-21
1
INTRODUCTION
Humans started to fight against natural disasters from their first day on earth till now like
earthquakes, floods, tsunamis, etc. To fulfill the needs of mankind, the development of the world
started in every field of life. With the development of mankind, structures were constructed rapidly
[1]. Now everyone can see hundreds of skyscrapers, bridges, and other fascinating structures
across the world. To cope with the disaster of earthquakes, people started considering the
earthquake-resistant structure in the design [2]. Earthquakes do not kill people but actually, people
are killed by the collapse of badly designed and constructed buildings. The Kashmir earthquake of
October, 2005 had devastating effects on the area with many buildings damaged or collapsed.
Many people lost their lives [3]. It is almost impossible to exactly predict the occurrence of an
earthquake but the histories of previous earthquakes make it possible to a great extent and with the
different types of new materials available in our inventory, it is possible to construct an earthquakeresistant building [4]. Many structural typologies shall be analyzed to provide a solution to a
problem that shall not only be efficient and cost-effective but also acceptable to the locality [5].
Page 1 of 8
2nd International Conference on Advances in Civil and Environmental
Engineering (ICACEE-2023)
University of Engineering & Technology Taxila, Pakistan
Conference date: 22nd and 23rd February, 2023
2
METHODOLOGY
1. Selection of Building
2. E-TABS modelling
3. Footing analysis and design in
2.1
SAFE
4. Detailing in REVIT
5. Comparison on different levels
Selection of Building
Our project is about the earthquake resistant design and comparison of reinforced concrete
buildings designed on UBC-97 and IBC-21 [6,7]. The hypothetical buildings of ten storeys having
uniform grid of 96’x96’ were selected and were designed in the software E-tabs and from there
suitable sizes of structural members were selected after analysis. The dimensions of both buildings
designed on UBC-97 and IBC-21 [6,7] having ten storeys, the beams are of size 15”x24”, the
columns provided are 30”x30” and slab thickness is 6.5”.
2.2
ETABS Modelling
Two types of finite elements are used in creating the ETABS model; frame elements to model
beams and columns and shell elements to model slabs and foundation.
The structure in ETABS is analysed and designed by performing the following steps.
1. First of all, we define the grid for the
structure. Grid size used is of 4’ x 4’. The
number of bays in both directions are 4.
software itself. Live load = 40 psf (as per
code) (on all floors except roof) Live load =
20 psf (as per code) (on roof only)
Superimposed dead load = 90 psf (from
floor finishes and wall loads) (on all floors
except roof)
Superimposed dead load = 40 psf (from
floor finishes and wall loads) (on roof only)
2. Number of stories = 10 and Height of each
story = 11’.
3. The materials used in the project are:
Concrete = 3000 psi (for beams and slab)
Concrete = 4500 psi (for columns and
foundation) Rebar = Grade 60 = 60000 psi
4. Various sections are defined for slabs,
beams and columns. After much trial and
error, we got the final sections as; Beams =
15” x 24”, Columns = 30” x 30’’, and
Slabs=6.5” (thick)
8. The seismic loading parameters are defined
as per the code. These values are specific to
Peshawar City.
9. Mass source is defined as per code for the
application of seismic forces to the model.
The dead loads are used in mass source.
5. After defining all the sections, the structure
is drawn using drawing commands.
10. A rigid diaphragm is assigned to the model.
6. The load patterns and load combinations are
defined as per the code.
12. The soil subgrade modulus is defined for
the value of spring constant for the design
of foundation.
7. The loads applied to the structure are; Dead
load = Weight of the structure taken by the
11. The Mat footing is modelled in SAFE.
Page 2 of 8
2nd International Conference on Advances in Civil and Environmental
Engineering (ICACEE-2023)
University of Engineering & Technology Taxila, Pakistan
Conference date: 22nd and 23rd February, 2023
13. The soil subgrade modulus for the design of
footing is calculated as:
b) The “run” button is now pressed to run the
analysis.
a) K = 12 x S.F x Bearing Capacity = 12 x 3 x
2.5 = 90 k/ft3 = 90000 lb/ft3
3
ANALYSIS
After carrying out the analysis the major outputs of structural analysis are the:
(1) Shear force diagrams, (2) Bending moment diagrams, and (3) Axial force diagrams
3.1
Shear Force Diagram
The SFD of the models using both the codes are given below in Figure 1 and 2. The values below
are in the units of “kip”.
3.1.1 UBC-97:
3.1.2
IBC-21
Figure 2: Shear force diagram (UBC-2021)
Figure 1: Shear force diagram (UBC-1997)
Page 3 of 8
2nd International Conference on Advances in Civil and Environmental
Engineering (ICACEE-2023)
University of Engineering & Technology Taxila, Pakistan
Conference date: 22nd and 23rd February, 2023
3.2
Bending Moment Diagram
The SFD of the models using both the codes are given below in Figure 3 and 4. The values below are in
the units of “kip-in”.
3.2.1 UBC-1997:
3.2.2
Figure 3: Bending moment diagram (UBC-97)
3.3
IBC-2021:
Figure 4: Bending moment diagram (UBC-21)
Axial Force Diagram
The Axial force diagrams of the models using both codes are given below in Figure 5 and 6. The values
below are in the units of “kip”.
3.3.1 UBC-97:
Figure 5: Axial force diagram (UBC-97)
3.3.2
IBC-21:
Figure 6: Axial force diagram (UBC-21)
Page 4 of 8
2nd International Conference on Advances in Civil and Environmental
Engineering (ICACEE-2023)
University of Engineering & Technology Taxila, Pakistan
Conference date: 22nd and 23rd February, 2023
4
RESULTS AND DISCUSSION
4.1 Base Shear Comparison
Base Shears are computed according to both the codes i.e. UBC-1997 and IBC-2021.
4.1.1 UBC-1997:
Base Shear computed from the Static lateral force procedure according to UBC-1997 is given by:
𝐶𝑣𝐼
𝑊
𝑅𝑇
Cv = Coefficient of velocity I =
iv.
Importance factor
v.
𝑉=
i.
W = Seismic weight of the structure
ii.
R = Response modification coefficient
The total design base shear shall not be less
than the following:
iii.
T = Time period
𝑉 = 0.11𝐶𝑎𝐼𝑊
Now:
𝑉=
2.5𝐶𝑎𝐼
𝑅
𝑊
and
𝑇 = 𝐶𝑡(ℎ𝑛)3/4
Finally, by putting all the values in these equations the Base Shear, V = 968.66 kip
4.1.2 IBC-2021:
Base Shear computed from the Static lateral force procedure according to IBC-2021 is given by:
𝑆𝐷𝑆𝐼
𝑊
𝑅
SDS = Two-thirds of the maximum
ii.
considered earthquake spectral response
iii.
accelerations for short period (0.2s)
iv.
𝑉=
i.
2
I = Importance factor
R = Response modification coefficient
W = Seismic weight of the structure
2
𝑆𝐷𝑆 = 3 𝑆𝑀𝑆, and 𝑆𝐷1 = 3 𝑆𝑀1
But,
𝑆𝑀𝑆 = 𝐹𝑎𝑆𝑆 and 𝑆𝑀1 = 𝐹𝑣𝑆𝑆
For Peshawar City, Ss=0.6 to 0.8 and S1=0.25 to 0.3
i.
ii.
SMS = maximum considered earthquake
spectral response accelerations for shortperiod
SM1 = maximum considered earthquake
spectral response accelerations for 1
second period
iii.
iv.
Fa = Site coefficient for short-period
accelerations
Fv = Site coefficient for 1-second period
accelerations
𝑆𝐷1𝐼
Maximum Base Shear = 𝑉 = 0.01𝑊 and Maximum Base shear = 𝑉 = 𝑅𝑇 𝑊
Finally, by putting all the values in the equations the Base Shear, V = 954.35 kip
4.1.3 Comparison
On comparing the Base Shears calculated from both codes there is not any significant difference between
the two. Base Shear from IBC-2021 is slightly less than the Base Shear calculated from UBC-1997.
Page 5 of 8
2nd International Conference on Advances in Civil and Environmental
Engineering (ICACEE-2023)
University of Engineering & Technology Taxila, Pakistan
Conference date: 22nd and 23rd February, 2023
4.2
Shear Force and Bending Moment Comparison
The shear forces and bending moments in a particular beam designed for both codes are given
below in Figure 7 and 8.
4.2.1 UBC-1997
4.2.2
Figure 7: Shear force and bending moment
diagram (UBC-1997)
Figure 8: Shear force and bending moment
diagram (IBC-2021)
Let’s take a beam at level 5 of the building i.e.
Beam B22 and analyzed it for the maximum
load combination according to UBC-1997. Its
shear force and bending moment diagram is
given below:
Beam B22 is analyzed for the maximum load
combination according to IBC-2021. Its shear
force and bending moment diagram is given
below:
So from the figure it is shown that the
maximum shear force and bending moment in
this beam are:
Maximum shear force V = 34.328 kip
Maximum bending moment M=2422.81 kip-in
IBC-2021
So from the figure it is shown that the
maximum shear force and bending moments in
this beam are:
Maximum shear force V = 30.197 kip
Maximum bending moment M=2103.71 kip-in
Page 6 of 8
2nd International Conference on Advances in Civil and Environmental
Engineering (ICACEE-2023)
University of Engineering & Technology Taxila, Pakistan
Conference date: 22nd and 23rd February, 2023
4.2.3 Comparison
On comparing the maximum shear force and maximum bending moment developed in the beam,
we can observe that the shear force and bending moment in the beam designed according to the
IBC-2021 is slightly less than the shear force and bending moment in the beam designed according
to the UBC-1997.
4.3
Axial Force Comparison
4.3.1 UBC-1997
Let’s take the middle column at level 1 of the
building i.e. Column C11 and analyze it for the
maximum load combination according to UBC1997. Its axial force diagram is given below in
Figure 9:
4.3.2 IBC-2021
Column C11 is analyzed for the maximum load
combination according to IBC-2021. Its axial
force diagram is given below in Figure 10:
Figure 9: Axial force diagram (UBC-1997)
Figure 10: Axial force diagram (IBC-2021)
So from the figure it is shown that the
maximum axial force P = 1110.285 kip
So from the figure it is shown that the
maximum axial force P = 995.115 kip
4.3.3 Comparison
On comparing the maximum axial force developed in the column, we can observe that the axial
force in the column designed according to the IBC-2021 is slightly less than the axial force in the
column designed according to the UBC-1997.
Page 7 of 8
2nd International Conference on Advances in Civil and Environmental
Engineering (ICACEE-2023)
University of Engineering & Technology Taxila, Pakistan
Conference date: 22nd and 23rd February, 2023
5
1.
2.
3.
4.
CONCLUSION
UBC-97 estimates 1.5 % more base shear than IBC-21
UBC-97 estimates 13.68% more maximum shear force than IBC-21
UBC-97 estimates 15.16% more maximum bending moment than IBC-21
UBC-97 estimates 11.57% more maximum axial force than IBC-21.
REFERENCES
1
Swenson, Alfred; Chang, Pao-Chi. History of Building (PDF). Archived from the original (PDF) on 2016-0304.
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Emerging techniques to simulate strong ground motion. Sandeep, ... A. Joshi, in Basics of Computational
Geophysics, 2021
3
"Pakistan: A summary report on Muzaffarabad earthquake" ReliefWeb, 7 November 2005. Retrieved 23
February 2006.
4
O. Gunes, Turkey's grand challenge: Disaster-proof building inventory within 20 years, Case Studies in
Construction
Materials,
Volume
2,
2015,
Pages
18-34,
ISSN
2214-5095,
https://doi.org/10.1016/j.cscm.2014.12.003.
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Wenjun Gao, Xilin Lu, Shanshan Wang, Seismic topology optimization based on spectral approaches,
Journal of Building Engineering, Volume 47, 2022, 103781, ISSN 2352-7102,
https://doi.org/10.1016/j.jobe.2021.103781.
6
7
8
9
UBC-1997
IBC-2021
ASCE 7-10
Design of Concrete Structures by Darwin
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