damage assesement curves for rc framed structures …€¦ · rao, damage assesement curves for rc...

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International Journal of Civil Engineering and Technology (IJCIET)

Volume 9, Issue 8, August 2018, pp. 1769–1782, Article ID: IJCIET_09_08_178

Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=9&IType=8

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication Scopus Indexed

DAMAGE ASSESEMENT CURVES FOR RC

FRAMED STRUCTURES UNDER SEISMIC

LOADS

Bhavani Chowdary. T

Research Scholar @ koneru lakshmaiah education foundation,

Green Fields, Vaddeswaram, Guntur, Andhra Pradesh, India

Assistant Professor, Vardhaman College of Engineering, Shamshabad, Hyderabad

kishore Babu. D

Assistant Professor, Geethanjali College of Engineering& Technology, Hyderabad

Dr. Vummaneni Ranga Rao

Professor, @ Koneru Lakashamaiah Education Foundation,

Green Fields, Vaddeswaram, Guntur, Andhra Pradesh, India

ABSTRACT

The overall capacity of a structure depends on the strength and deformation

capacity of the isolated components of the structure. The present study is based on the

analytical investigation of global seismic performance and potential seismic damage

of a reinforced concrete framed structure. Displacement – based analysis techniques

widely Nonlinear static analysis is adopted in this study to assess the performance

factors such as base shear and roof displacement since the seismic damage is directly

correlated to the roof displacement of the structure. The yield displacement of the

structure is reviewed from the nonlinear static analysis, from which the peak values

exceeding yield displacement has been identified and dissipated energy is calculated

for each cycle to quantify the damage of the structure. To achieve these results,

moment resisting frames representing low, mid and high-rise RC structure designed as

per Indian standard codes. Using energy dissipation approach, displacement versus

damage curves are plotted as per the damage probability at every displacement level.

Keywords: Base Shear, Damage curve, Nonlinear Static Analysis, Roof

Displacement, probability of damage.

Cite this Article: Bhavani Chowdary. T, kishore Babu. D and Dr. Vummaneni Ranga

Rao, Damage Assesement Curves for RC Framed Structures under Seismic Loads,

International Journal of Civil Engineering and Technology, 9(8), 2018,

pp. 1769–1782.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=9&IType=8

Damage Assesement Curves for RC Framed Structures under Seismic Loads


1. INTRODUCTION

Earthquake risk assessment is a process of estimating the probability of damage to a given

structure due to an earthquake. A Vulnerability of a structure is an important consideration for

risk assessment methodology. The seismic vulnerability of a structure can be described as the

extent of its exposure to the intensity of ground shaking. It includes estimation of the

probability of a given level of damage to any structure for given level of earthquake. The level

of damage depends on the performance of structural and non-structural elements during the

earthquake.

The Bhuj earthquake (2001) caused a lot of damage to multi-story buildings in urban areas

of Gujarat. This has posed a serious threat to the many existing Indian RC buildings which are

designed mainly for gravity loads. Most of the Reinforced concrete buildings in India have the

open ground storey for parking facilities. This soft story mechanism of failure makes the most

of the RC Buildings vulnerable to earthquake shaking.

Severe earthquakes apply complex loading to the structure. So, the structure is shaken

well into the inelastic range. To analyze the structures which were suffered from these

earthquakes, we need an analysis tool which can provide deep insight into the structural

elements, which control performance during the earthquakes. Inelastic analysis procedures

only can give details about post- elastic deformation of structural members. But unfortunately,

Indian codes don‟t have such provisions for the nonlinear analysis of structures. Pushover

analysis is one such a tool which can give required information about the inelastic response of

the structure.

Though the evaluation of the vulnerability of existing RC MRF buildings is not new, the

application of the same techniques to non-ductile or gravity load designed buildings is not so

well developed in India. So, the analysis technique proposed in ATC-40 is being used for the

performance evolution of gravity load designed RC Moment resisting framed building in

India.

1.1. Significance of Non Linear Analysis

The pushover is expected to provide information on many response characteristics that cannot

be obtained from an elastic static or dynamic analysis. The following are the examples of such

response characteristics:

The realistic force demands on potentially brittle elements, such as axial force

demands on columns, force demands on brace connections, moment demands on

beam to column connections, shear force demands in reinforced concrete beams,

etc.

Estimates of the deformations demands for elements that have to form inelastically

in order to dissipate the energy imparted to the structure.

Consequences of the strength deterioration of individual elements on the behavior

of the structural system.

Identification of the critical regions in which the deformation demands are

expected to be high and that have to become the focus through detailing.

Identification of the strength discontinuous in plan elevation that will lead to

changes in the dynamic characteristics in the elastic range.

Estimates of the inter story drift that account for strength or stiffness

discontinuities and that may be used to control the damages and to evaluate P-

Delta effects. Verification of the completeness and adequacy of load path,

considering all the elements of the structural systems, all the connections, and stiff

non-structural elements of significant strength, and the foundation system.

Bhavani Chowdary. T, kishore Babu. D and Dr. Vummaneni Ranga Rao


2. OBJECTIVE OF THE STUDY

The main objective of my study is to estimate the amount of damage through displacement

based on three different structures by using energy dissipation approach.

The damage assessment from pushover gives the damage of building with respect to

displacement.

To study the available analytical tools for seismic evaluation

Seismic performance evaluation of RC buildings.

To understand the structural behaviour\response to seismic forces.

Estimation of seismic inelastic displacement.

2.1. Research significance

Prathibha S and A Meher(2004) explained and considered a representative residential building

in Indian seismic zones. They stated that pushover analysis gives a quick estimate of the base

shear and the desired performance of the building in its existing condition. Also, this

methodology is efficient in determining the effective members and the performance of the

building as a whole. The performance of the building is finally checked for code compliance

and for the probable failure mechanisms. This evaluation is a prerequisite for the retrofit of

the existing RC MRF buildings in India.

A.Kadid and Boumarkik (2008) concluded that The pushover analysis is a relatively

simple way to explore the nonlinear behavior of the buildings. The behavior of properly

detailed reinforced frame building is adequate as indicated by the intersection of the demand

and capacity curves and the distribution of hinges in the beams and the columns. Most of the

hinges developed in the beams and few in the columns but with limited damage. The cause of

failure of reinforced concrete during the Boumerds earthquake may be attributed to the quality

of the material of the user and also to the fact that most of the buildings constructed in Algeria

are of strong beam and weak column type and not to the intrinsic behavior of framed

structures. The results obtained in terms of demand, capacity and plastic hinges gave an

insight into the real behavior of structures. It would be desirable to study more cases before

reaching the definite conclusion about the behavior of reinforced concrete frame buildings.

Chenna Rajaram and Pradeep KumarRamacharla(2014) studied about port building are

frequently exposed to failure under severe seismic loading, he considered three different ports

taken, ports are LomaPrieta(1989),Kobe(1995),Kocaeli (1999) earthquake. His study has been

carried out to find out the damage of port building based on the damage assessment using

energy dissipation approach. A damage curve has been developed to quantify the damage of

building with respect to different peak ground accelerations. Pushover analysis is done to get

the base shear Vs roof displacement of the building using displacement control method. Total

area under pushover curve is the total energy of the structure, they are used energy dissipation

approach calculated the elastic and inelastic energy of the structure at each displacement. The

damage parameter (D) is defined as the ratio of inelastic energy to the total energy of the

structure. Based on the damage assessment of port building given the recommendations are

the total damage of the structure like Kandla port building is at around 0.16, 0.25 and 0.34 for

Mandavi (0.218g), Jodiya(0.377g) Jhangi (0.396g) response spectra respectively.

Anthugari Vimala and Pradeep Kumar Ramacharla (2014)study are based on the

analytical investigation of seismic performance and potential seismic damage of a reinforced

concrete framed building due to earthquakes, by using nonlinear modeling and displacement-

based analysis techniques, the seismic damage is directly correlated to the displacement

(deformation) of the structure. Her study is roughly divided into two parts first part includes

evaluation of the nonlinear seismic behavior of building subjected to the given ground



excitations. Second part includes evaluation of damage, the study is based on analytical

investigation of seismic performance and potential seismic damage of a reinforced concrete

framed building due to earthquakes by using nonlinear modeling and displacement-based

analysis techniques, the peak values which exceeding yield displacement of the structure have

been identified and the hysteresis energy is calculated, the area under this curve gives the total

energy dissipated until the collapse of the structure, to represent the damage state of the

structure at each displacement ,a damage scale is proposed. At ultimate displacement the

damage scale is normalized to1, The yield displacement of the structure from pushover

analysis is observed as 14 mm. It is observed that there is no damage up to the yield

displacement.

Swajit Singh Goud and Ramacharla Pradeep Kumar (2014) study are based on response

reduction factor and inter storey drift .Most seismic design codes allow the structure to be

designed for lesser force than elastic force, thus allowing a structure to damage at appropriate

locations. Indian seismic code IS 1893-2002 divides seismic design of structures into three

categories; Ordinary moment resisting frame, Intermediate moment resisting frame and

Special moment resisting frame. The classification differs based on reinforcement detailing

and response reduction factor. It is expected that the performance of ductile detailed building

would be better than non- ductile detailed building and the capacity shall be more and damage

is less compared to the non-ductile detailed building.

He concluded that the results obtained from POA and fragility analysis clearly shows that

earthquake resistant design will reduce the damage in the structure significantly. Assumed

load pattern in pushover analysis plays an important role in the non-linear response of the

structure. Design provisions for ductile detailing need to be modified as it has been observed

that with increased R values, the member size decreases and lead to structures having more

damage compared to normal detailed structures thus R need to be defined more clearly as in

other seismic codes.

2.3. Building Performance Levels and Ranges (Atc)

Performance Level: the intended post-earthquake condition of a building; a well-defined point on a

scale measuring how much loss is caused by earthquake damage. In addition to casualties, the loss

may be in terms of property and operational capability.

Performance Range and Levels: A range or band of performance, rather than a discrete

level.

Performance of building has been classified into 5 levels, viz.

Operational (OP)

Immediate Occupancy (IO)

Damage Control (DC)

Life Safety (LS) and

Collapse Prevention (CP)

2.3.1. Operational (Op)

Structural Performance Level S-1, Immediate Occupancy, means the post-earthquake damage

state in which only very limited structural damage has occurred. The basic vertical and lateral-

force-resisting systems of the building retain nearly all of their pre-earthquake strength and

stiffness. In the primary concrete frames, there will be hairline cracking. There may be a few

location where the rebar will yield, but the crushing of concrete is not expected. The transient

drift will be about 1%, with negligible permanent drift. In the brick infill walls, there will be

minor cracking and minor spalling of plaster. The risk of life threatening injury as a result of



structural damage is very low, and although some minor structural repairs may be appropriate,

these would generally not be required prior to re-occupancy.

2.3.2. Damage Control (Dc)

Damage Control Performance Range (S-2) means the continuous range of damage states that

entail less damage than that defined for the Life Safety level, but more than that defined for

the Immediate Occupancy level. Design for Damage Control performance may bedesirable to

minimize repair time and operation interruption; as a partial means of protecting valuable

equipment and contents; or to preserve important historic features when the cost of design for

Immediate Occupancy is excessive. Acceptance criteria for this range may be obtained by

interpolating between the values provided for the Immediate Occupancy (S-1) and Life Safety

(S-3) levels.

2.3.3. Life Safety Performance Level (Ls)

Life Safety Performance Level (S-3) means the post-earthquake damage state in which

significant damage to the structure has occurred, but some margin against either partial or

total structural collapse remains. Some structural elements and components are severely

damaged, but this has not resulted in large falling debris hazards, either within or outside the

building. In the primary concrete frames, there will be extensive damage in the beams. There

will be spalling of concrete cover and shear cracking in the ductile columns. The transient

drift will be around 2%, with 1% being permanent. In the brick infill walls, there will be

extensive cracking and some crushing. But the walls are expected to remain in place. The

transient drift will be about 0.5%, with 0.3% being permanent. Injuries may occur during the

earthquake; however, it is expected that the overall risk of life threatening injury as a result of

structural damage is low. It should be possible to repair the structure; however, for economic

reasons this may not be practical. While the damaged structure is not an imminent collapse

risk, it would be prudent to implement structural repairs or install temporary bracing prior to

re-occupancy.

2.3.4. Collapse Prevention Performance Level (Cp)

Collapse Prevention Performance Level (S-5) means the building is on the verge of

experiencing partial or total collapse. Substantial damage to the structure has occurred,

potentially including significant degradation in the stiffness and strength of the lateral-force

resisting system, large permanent lateral deformation of the structure and to more limited

extent degradation in vertical-load-carrying capacity. However, all significant components of

the gravity load-resisting system must continue to carry their gravity load demands. In the

primary concrete frames, there will be extensive cracking and formation of hinges in the

ductile elements. There will be about 4% inelastic drift, transient or permanent. There will be

extensive cracking and crushing in the brick infill walls. Walls may dislodge due to out of -

plane bending. There will be 0.6% inelastic drift, transient or permanent. Significant risk of

injury due to falling hazards from structural debris may exist. The structure may not be

technically practical to repair and is not safe for re-occupancy, as aftershock activity could

induce collapse. Figure 3.6 depicts various performance levels and damage functions.



Figure 1 Performance levels and damage Function

Damage parameter (D) is the ratio of inelastic energy at a point to the total energy under

the pushover curve.

E𝛥= Inelastic energy at a point

ET= Total energy under the curve

D=E𝛥/ET

2.4. Modelling of structures

One of the major objectives of this work was to test a real- life structure under pushover

loads. In order to keep the structure as close to reality as possible, no special design for the

structure as such was performed and instead a portion of a real life existing office building

was selected. For the current study a low, mid, high-rise (G+3, G+6, G+9) storey buildings is

considered. Horizontal or vertical irregularities, cantilever projections or heavy overhangs are

avoided in the building as per the principals of earthquake resistant design. It is also

symmetric about X and Y axes to avoid torsion. The building is assumed to be located in

seismic zone V. External, internal wall thickness and slab thickness are considered as 230

mm, 150 mm and 120 mm, respectively. Floor finish of 1 kN/m2 is considered. Design live

loads are assumed as 3 kN/m2, 1 kN/m

2 and 1.5kN/m

2 on floors, roof. For analysis, dead load,

imposed load and seismic load were considered as per IS 875 (1987) and IS 1893 (2002),

respectively

Table 1 representing the details of the structures

Type of structure G+3 G+6 G+9

Grade of concrete M25 M25 M25

Grade of steel FE 415 FE 415 FE 415

Live load 3KN/m2 3 KN/m

2 3KN/m

2

Beam dimensions 230X300 mm 300x450 mm 450x500 mm

Column dimensions 230X300 mm 300x450 mm 450x500 mm

Density of concrete 25 KN/m3 25 KN/m

3 25 KN/m

3

Density of masonry wall 20 KN/m3 20 KN/m

3 20 KN/m

3

Type of zone Zone V Zone V Zone V

Importance factor 1 1 1

Type of frames Special Moment

Resisting Frames (R=5)

Special Moment Resisting Frames

(R=5)

Special Moment Resisting Frames (R=5)



2.5. Model Geometry

The structure geometry is four bay along X-direction and three bay along Y-direction

moment-resisting frame of reinforced concrete with properties as specified above.

The plane of building is same for all.

Bay width along X-direction = 5.0 meters

Bay width along Y-direction = 3.0 meters

Figure 2 Plan for all the models

Figure 3 Elevation for all the three models

2.6. Results and Discussions

2.6.1. General

This chapter presents the results of Analysis of RCC frame. Analysis of RCC frame under the

static loads has been performed using SAP2000v15.1software. The results are obtained from

this analytical procedure and Analysis of low-rise, mid-rise, high-rise Reinforced Concrete

Structure under Monotonic Push-over Loads. This is followed by load deflection curve.

2.6.2. Analysis results of R.C.C frame

In the present study, non-linear response of RCC frame modeled as per details, using

modeling under the loading has been carried out. The objective of this study is to see the

variation of load- displacement graph and check the maximum base shear and displacement of

the frame.



After running the analysis, Reinforcement details as shown in Fig.5.4. Resultant pushover

curve is obtained as shown below. and damage variation with respect to displacement as

shown in Fig 5.3. Type of building Base Shear(Vb) KN Modal participation Factor

Low-rise 865.0998 27.3

Midrise 1944.17 39.066

High-rise 3548.0 50.44

From the above table it is identified that base shear is proportional to the modal

participation factor.

2.6.3. Mode Shapes of Reinforced concrete structures

Figure 5.3 (a): First mode shape for Low-rise: Time period-1.376, Frequency-0.7264

Figure 5.3 (b): Second mode shape for Low-rise: Time period-1.291, Frequency-0.7740

Figure 5.3 (c): First mode shape for Midrise: Time period-1.3549, Frequency-0.7380.

Figure 5.3 (d): Second mode shape for Midrise: Time period-1.1887, Frequency-0.8412.



Figure 5.3 (e): First mode shape for High-rise: Time period-1.313, Frequency-0.7612.

Figure 5.3 (f): Second mode shape for High-rise: Time period-1.309, Frequency-0.7637.

From the above figures it is observed that first mode takes the significant response of the

structure, from the second mode onwards the displacements are observed.

2.7. REINFORCEMENT DETAILS

Figure 5.4 (a): Reinforcement Details for Low-rise Structure



Figure 5.4 (b): Reinforcement Details for Midrise Structure.

Figure 5.1 (C): Reinforcement Details for High-rise Structure.

Reinforcement plays a vital role in the Structures response to the impact loadings and the

reinforcement provide for every structure in this paper is within the permissible limits and the

code followed for that was IS 13920:1993 and IS 456:2000.

2.8. Push Over Curves

Figure 4 Pushover Curve for Low-rise Structure

Push over curve represents the total base shear to the corresponding displacement. It gives

the value for the maximum seismic demand that a structure can hold for a low rise structure

like this the maximum load that structure can hold is 865 KN for a maximum displacement of

143 mm.

0

500

1000

1500

0 50 100 150

Ba

se S

hea

r (K

N)

Displacement (mm)



Figure 5 Pushover Curve for Mid-rise Structure


the value for the maximum seismic demand that a structure can hold for a low mid rise

structure like this the maximum load that structure can hold is 3339.9 KN for a maximum

displacement of 333.3 mm.

Figure 6 Pushover Curve for High-rise Structure


the value for the maximum seismic demand that a structure can hold for a low mid rise

structure like this the maximum load that structure can hold is 7380 KN for a maximum

displacement of 488.2 mm.

2.9. Fragility Curves

Using energy dissipation approach the fragility curves are drawn for the structures and the

main principle involved is the inelastic displacement at any point on the curve to the curve

under area gives the damage quantification at each displacement level. Damage curves are

drawn for all the structures and are represented below

0

2000

4000

6000

8000

0 200 400 600Ba

se S

hea

r (K

N)

Displacement (mm)

0

2000

4000

6000

8000

0 200 400 600

Ba

se S

hea

r (K

N)

Displacement (mm)



Figure 7 Damage Curve for Low-rise Structure

Figure 8 Damage Curve for Mid-rise Structure

Figure 9 Damage Curve for High-rise Structure

3. CONCLUSIONS AND RECOMMENDATIONS

3.1. General

In the present study, the non-linear response of RCC frame using SAP2000 under the loading

has been carried out with the intention to study the relative importance of several factors in

the non-linear analysis of RC frames.

0

0.4

0.8

1.2

0.00 50.00 100.00 150.00

Dam

age

(D

)

Displacement (mm)

0

0.4

0.8

1.2

0.00 200.00 400.00

Da

ma

ge

(D)

Displacement (mm)

0

0.4

0.8

1.2

0 150 300 450 600

Da

ma

ge

(D)

Displacement (mm)



4. CONCLUSIONS

The main observations and conclusions drawn are summarized below:

The damage of the structure like low, mid, high rise buildings is easily identified

from damage curve is drawn for different displacement.

Pushover analysis is done to get base shear vs roof displacement of building using

displacement control method.

For low rise structure the base shear is about 865 KN and corresponding

displacement is 143 mm.

For mid-rise structure the base shear is about 3339.9KN and corresponding

displacement is 334.3mm.

Similarly for high-rise structure base shear is about 7380 KN and displacement is

488.2 mm.

Using energy dissipation approach, damage is quantified at every displacement

level.

A damage curve has been developed to quantify the damage of building easily

with respect to displacement.

As the height of the story increases the displacement increase.

Probability of damage for low rise structure is at a displacement of 139mm.

Probability of damage for mid rise structure is at a displacement of 350 mm.

Probability of damage for mid rise structure is at a displacement of 498 mm.

It found that the yield displacement of the structure from the pushover curve is observed

like low rise 13mm, 50mm& 30mm for mid and high rise buildings.

RECOMMENDATIONS

The literature review and analysis procedure utilized in this thesis has provided useful insight

for future application of SAP2000 for analysis. Modeling the RCC frame in SAP2000

software gives good results which can be included in future research.

FUTURE SCOPE

In the present study frame has been studied under monotonic loads. The frame can be studied

under cyclic-loading to monitor the variation in load-deflection curves given time history.

REFERENCES

[1] K. Poljansek and P.Fajfar, A new damage model for the seismic damage assessment of

reinforced concrete frame structures.

[2] Dakshes and J.pambhar “Performance Based Pushover Analysis of R.C.C. Frames”,

International journal of advanced engineering research and studies. E-ISSN2249-8974.

[3] Chopra, A. K. (1995). Dynamics of structures: theory and applications to earthquake

engineering, Chaps. 3, 6, 7, and 19. Englewood Cliffs, N.J.: Prentice Hall.

[4] ATC 40, 1996, “Seismic Evaluation and Retrofit of Concrete Buildings: vol. 1”, Applied

Technology Council, USA.

[5] IS 456 (2000) Indian Standard for Plain and Reinforced Concrete - Code of Practice,

Bureau of Indian Standards, New Delhi. 2000.

[6] FEMA 356, 2000, “Pre-standard and Commentary on the Guidelines for the Seismic

Rehabilitation of Buildings”, American Society of Civil Engineers, USA.



[7] IS 1893(Part 1):2002, “Indian Standard Criteria for Earthquake Resistant Design of

Structures”, Bureau of Indian Standards, New Delhi.

[8] Prathibha S and A Meher Prasad (2004),‟Seismic vulnerability of existing RC buildings in

India‟, 13th World conference on earthquake engineering, paper no.1207.

[9] Kadid, A., & Boumrkik, A. (2008), „Pushover analysis of reinforced concrete frame

structures‟, Asian Journal of Civil Engineering (Building and Housing), 9, pp. 75-83.

[10] Anthugari Vimala and Ramancharla Pradeep Kumar (2012), “Displacement Based

Damage Estimation of RC Bare Frame Subjected to Earthquake Loads: A case Study on 4

Storey Building”, 15th world conference on Earthquake Engineering.

[11] Chenna Rajaram and Ramancharla Pradeep Kumar (2014), “Seismic Damage Estimation

for Port Building: An Energy based Approach”, ISSE JOURNAL – Volume 16-4. Oct –

Nov-Dec 2014.

[12] Swajit sing Goud and Ramancharla Pradeep Kumar (2014), „Seismic design provisions for

ductile detailed reinforced concrete structures‟, 15th Symposium on earthquake

engineering, (15th SEE 2014).

[13] Vahid Vahedian (2014), „Evaluation of Nonlinear Static Analysis for Special Moment

Resisting Frames‟, Journal of Civil Engineering and Urbanism-Volume:529-533(2014).

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