IRJET - Evaluation of Response Reduction Factor on RC Building with Singly and Doubly Reinforced Beam

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 07 Issue: 04 | Apr 2020 www.irjet.net p-ISSN: 2395-0072
© 2020,IRJET | Impact Factorvalue:7.34 | ISO 9001:2008CertifiedJournal | Page 1537
EVALUATION OF RESPONSE REDUCTION FACTOR ON R C BUILDING
WITH SINGLY AND DOUBLY REINFORCED BEAM
T. P. Deshmukh1, S. P. Dongare2
1Student M-Tech Structures, Dept. of Civil Engineering, G. H. Raisoni University, Amravati 444701, India..
2Assistant Professor, Dept. of Civil Engineering, G. H. Raisoni University, Amravati 444701, India.
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Abstract - The Response reduction factor R reflects the
capacity of structure to dissipate energy through inelastic
behavior. Response reduction factors play a key, but
controversial role in the seismic design process. Seismic design
of structures is based on elastic force. The nonlinear response
of structure is not incorporated in design philosophy but its
effect is incorporated by using appropriate response reduction
factor (R). The concept of response reduction factor is to de-
amplify the seismic force and incorporate nonlinearity with
the help of over strength, redundancy and ductility.
High ductile designed frame will attract more damage
compared to structure designed for lower ductility, due to
large yield excursion [1]. Greater the assumed value of R,
grater will be the ductility in the structure. Use of higher
values of R is encouraged because of significant reduction in
base shear leading to more economic structure. But when
modulus of elasticity of reinforced concrete (ERCC) considered,
not only reduces value of R but also consumed percentage of
steel in RC members. In the paper, study is done to compute the
value of R, component wise of a G+15 storeys building
designed forconsidering E and ERCC design provisions andthe
same is compared with the R.
Key Words: Ductile design, Response reduction factor &
Modulus of Elasticity
1.INTRODUCTION
Seismic design of structures is based on elastic force. The
nonlinear response of structure is not incorporated indesign
philosophy but its effect is incorporated by using
appropriate response reduction factor (R). The concept of
response reduction factor is to de-amplify the seismic force
and incorporate nonlinearity with the help of over strength,
redundancy and ductility. Ductile detailing is done in
structure to increase the ductility and to reduce the amount
of damage compared to non- ductile detailed structure. High
ductile designed frame will attract more damage compared
to structure designed for lower ductility, due to large yield
excursion. The design seismic forces are reduced drastically
by using higher values of R and incorporating higher
ductility.
Response reduction factor (R) is defined differently in
different countries for different types of structural systems.
In Indian seismic code, IS1893:2002 [2], value of R for
reinforced concrete structure is specified based on, ordinary
moment resisting frame
(OMRF) and special moment resisting frame (SMRF), and in
the latest proposed draft [3] one additional R value
incorporated for reinforced concrete structure based on
Intermediate moment resisting frame (IMRF). The value of R
varies from 3-5 in IS code as per type of resisting frame, but
the existing literature does not provide information on what
basis R values are considered.
In the present study, response reduction factor is computed
for (G+15) storeys building, designed considering modulus
of Elasticity of Plain concrete & reinforced concrete and
compared. The computation of R is done component wise to
understand the effect of each parameter i.e. stiffness, over
strength and ductility. Computation of R is done from
pushover curve which is based on available literature.IS code
defines R as Response Reduction factor, ASCE Defines as
Response modification coefficient and EC Defines as
Behavior factor. IS-1893 provides R factor for reinforced
concrete structures with three ductility classes;OMRF, IMRF
and SMRF with R value as 3, 4 and 5 respectively Response
reduction factor consists of majorly four parameters;
strength, redundancy, ductility and damping.
R= Rs Rμ Rρ RR
Where RS, RR, Rμ, Rρ represents over strength, redundancy,
ductility and damping factors respectively.
1.1 Over strength Factor (RS):
Over-strength factor (RS) defined as the ratio of maximum
base shear to the design base shear (Vd). It is a measure of
over-strength that a structure has beyond the design elastic
force. The value of RS depends on the factor of safety

considered in the materials and load combinations. The
value of over-strength factor varies in the range of 2-3 as
reported in many experimental studies [6].
Rs =
1.2 RedundancyFactor(RR):
Redundancy factor (RR) is defined as ratio of maximum base
shear (Vm) to yield base shear (Vy). Structure having more
number of vertical members comes in category of redundant
structural system. ASCE 07 suggest redundancy factor RR as
1 conservatively.
1.3 Ductility Factor (Rμ):
In the last decade extensive work has been done to
determine the ductility factor by Newmark and Hall, Nassar
and Newmark, Vidic et al. and Krawinkler and Nassr. In the
present study, a relationship developed by Pristley is used.
As the nonlinear response of RC structure do not have well
defined yield point, several methods had been proposed to
determine the yield displacement [7].
Fig.1 R–μ–T plot for an inelastic SDOF system.
1.4 Damping Factor (Rρ):
Damping factor Rρ is applicable for the structures installed
with additional energy dissipating devices, the damping
factor is assumed to be 1 for buildings without suchdevices.
2. LITERATURE REVIEW
Newmark, Hall [10] noted following observations based on
elastic and inelastic response spectra of the NS component of
the El Centro, California earthquake of May 18, 1940, as well
as on previous studies of the response on simple systems to
pulse-type excitations and two other recorded ground
motions, (i) in the low- frequency and medium frequency
spectral regions, an elastic and an inelastic system had
approximately the same maximum displacement; (ii) in the
extremely high- frequency region, an elastic and an inelastic
system had the same force; and (iii) in the
moderately high-frequency region, the principle of
conservation of energies could be used by which the
monotonic load- deformation diagram of the elastic system
up to the maximum deformation was the same as that of an
elastic- perfectly plastic system subjected to the same
excitation. These observations resulted in the
recommendation of a procedure to construct inelastic
spectra from the elastic spectra. The procedure consisted of
the reduction of the elastic spectra by different factors for
each spectral region.
Riddell, Newmark [11] improved set of deamplification
factors was based on a statistical analysis of inelastic
response spectra for elasto-plastic systems with 2%, 5%,and
10%damping, and for bilinear and stiffness degrading
systems with 5 % damping and for ductility values from 1 to
10. They concluded that peak responses of elasto-plastic,
bilinear and stiffness degrading systems are very similar,
and that the use of an elastic-plastic spectrum for inelastic
analysis was generally conservative. They studied first to
consider a statistical analysis of inelastic spectra of recorded
ground motions, considered ten earthquake ground motions
recorded on rock and alluvium sites.
Nassar. et al. [12] considered the response of SDOF
nonlinear systems when subjected to 15 ground motions
recorded in the Western United States. The records used
were obtained at alluvium and rock sites. The influence of
site conditions, however, was not explicitly considered. The
sensitivity of mean strength reduction factors to the
epicentral distance as well as structural system parameters
such as natural period, yield level, strain-hardening ratio
and the type of inelastic material behavior (i.e. bilinear
versus stiffness degrading) was examined. The study
concluded that epicentral distance and stiffness degradation
had a negligible influence on strength reduction factors.
3. OBJECTIVES AND METHODOLOGY
3.1 Finite Element Method: In this method finite element
model of 150mm x150mm x 700mm size of beam analyzed
and observed the load deflection pattern for various
percentages of compression steel models.

3.2 Graphs: Graphs are plotted for all above mention beam
combination for load vs. first crack deflection and by using
regression analysis find out the overall equation foe all
models with their curve equation to form generalize
equation for E value to M20 grade concrete with
compression zone steel.
3.3 Pushover analysis: Pushover analysis is Non Linear
Static Analysis done to determine the capacity of structure.
With the help of pushover curve nonlinear behavior of
structure lateral loads can be observed. Non-linear static
analysis knowledge of material property, stress-strain model
etc.
4. EXPERIMENTAL WORK
4.1 Stress Analysis:
4.2 Modulus of elasticity:
The modulus of elasticity, denoted as E, is defined as the
ratio between normal stress to strain below the proportional
limit of a material. The modulus of elasticity for plain
concrete as per IS 456-2000 [8] is
E= 5000
While performing analysis by any software for R C building,
cross area of plain concrete is taken into consideration
whereas effects of reinforcement bars and concrete confined
by stirrups is neglected. Two important stiffness properties
such as AE and EI play important role inanalysis of high rise
RCC building idealized as plane frame. Modulus of elasticity
for reinforced concrete [9] with considering compression
reinforcement is
ERCC= 4340.1pt2 +3208.12pt+5000
+1983.42(Asc/100)
IS: 456-2000 suggests formula for modulus of elasticity of
plain concrete as which does not consider the effect of
reinforcement. It was observed that modulus of elasticity of
reinforced concrete varies with percentage of reinforcement.
4.3 Building details:
For the current study G+15 story Residential building
located in Pune is considered. Fig.-2 shows center line
diagram, beam location, column orientation. Building
consists of four flats on each floor. Building have horizontal
& vertical irregularities & cantilever projections It is
unsymmetrical about X and Y axes. All the walls are
supported on beams and every beam is supported by a
column. Dog legged type staircase is 3considered with flight
and landing width is 1.5 m, riser and trade are 150 and 250
mm, respectively. Mid Landing of staircase is resting on
beam connected to the column.
Fig.2 Building Plan

Table -1: Basic assumptions and structural details
5. RESULTS
A. Results considering E for plain concrete
Fig 3 Base shear (Vu) by linear static method
Fig 4 Base shear (Vd) by nonlinear static method
B. Results considering E for reinforced concrete
Fig 5 Base shear (Vu) by linear static method
Dimension in X direction 15.15 m
Dimension in Y direction 19.40 m
Storey height 2.9 m
Type of soil Medium
Importance factor 1
Seismic Zone III
Loads
1. Dead load 1.5 Kn/m2
2. Live load 2 Kn/m2
3. Other 4 Kn/m2
4. Wall load Siporex
Concrete grade M20 N/mm2
Steel grade 500 N/mm2

Fig 6 Base shear (Vd) by nonlinear static method
6. CONCLUSION
1. Response reduction factor:
Response reduction factor when compared with model
considering reinforced concrete elasticity (ERCC) gives less
value than plain concrete elasticity (E). Base shear slightly
increased.
2. Time period:
As per elasticity of plain concrete time period is 2.29 sec
whereas per elasticity of reinforced concrete it is slightly
decrease, Permissible time is,
T =
3. Economy:
Response reduction factor reduced & base shear increased, it
consumes less percentage of steel required in beam
members.
REFERENCES:
[1] Lu & Carydis, P. G. (2001). ”Seismic performance of RC
frames designed for three different ductility levels“
Engineering Structures, 23, 537-547.
[2] Indian Standard Criteria for Earthquake Resistant Design
of Structures Part I: General Provisions and Buildings, IS
1893:2002. New Delhi: Bureau of Indian Standards.
[3] Jain, S. K., & Murty, “C. R. Proposed Draft Provisions and
Commentary on Indian Seismic Code IS 1893 (Part-1).”
IIITK-GSDMA Project of Building Codes.
[4] ASCE 7-05,” Minimum design loads for buildings and
other structures.” Reston (USA): American Society of Civil
Engineers.
[5] CEN Eurocode 8, “Design provisions for earthquake
resistance of structures (European Prestandard ENV 1998).”
Brussels (Belgium).
[6] Charney, F. A., & Bertero, V. V. (1982). “An evaluation of
the design and analytical seismic response of a seven storey
reinforced concrete frame wall structure Berkeley:
“Earthquake Engineering Research Institute.
[7] Park, R. (1989). “Evaluation of ductility of structures and
structural assemblages from laboratory testing.” Bulletin of
the New Zealand National Society for Earthquake
Engineering, 22 (3), 155-166.
[8] Indian Standard Code of Practice for Plain and Reinforced
Concrete, IS 456: 2000. New Delhi: Bureau of Indian
Standards.
[9] S K Kulkarni, M R Shiyekar et al (2014). “Elastic
properties of RCC under flexural loading-experimental and
analytical approach‖ “
[10] Newmark N, Hall W. (1982).”Earthquake spectra and
design.” Engineering Monograph. Earthquake Engineering
Research Institute, Berkeley, California.
[11] Riddell R, Newmark N. (1979).”Statistical analysis ofthe
response of nonlinear systems subjected to earthquakes.”
Structural research series no. 468; Dept. of Civil Engineering,
University of Illinois; Urbana, USA.
[12] Krawinkler H, Nassar A. “Seismic design based on
ductility and cumulative damage demands and capacities. In
Nonlinear seismic analysis of reinforced concrete.”
Equation
ERCC= 4340.1pt2 +3208.12pt+5000
+1983.42(Asc/100) (1)

IRJET - Evaluation of Response Reduction Factor on RC Building with Singly and Doubly Reinforced Beam

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