SEISMIC PERFORMANCE OF HIGH-RISE BUILDING · maximum considered earthquake by response spectrum analyses using ETABS software ... stiffness in the building ... Fourth floor slab is

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International Journal of Civil Engineering and Technology (IJCIET)

Volume 9, Issue 3, March 2018, pp. 878–886, Article ID: IJCIET_09_03_087

Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=9&IType=3

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

© IAEME Publication Scopus Indexed

SEISMIC PERFORMANCE OF HIGH-RISE

BUILDING

Somil Khattar

Student, School of Mechanical and Building Sciences, VIT University,

Tamilnadu, Chennai, India

Muthumani K

Professor, School of Mechanical and Building Sciences, VIT University,

Tamilnadu, Chennai, India

ABSTRACT

This work is aimed to study the seismic behavior of high-rise residential building

(i.e. 72 m tall) located in Indore city of Madhya Pradesh, India. It is modelled in

accordance with Indian Standard Codes. For high rise building, wind load is

governing for most of the cases. The building is designed for design basis earthquake

in accordance with IS 1893:2016 and its seismic performance is evaluated with

maximum considered earthquake by response spectrum analyses using ETABS

software. Same building is then modelled in accordance with American Code ASCE 7-

16 and its structural stability parameters such as base shear, story drift and lateral

displacement are compared with original building. On comparing the two, it is found

that though both the code gives different time period value, base shear results with

both the code are same. Also it is checked whether the moment demand of frame

section is within the ultimate moment carrying capacity of frame at floors where

reduction in plan area occurs. It is found that due to sudden reduction in plan area

between two floors, stiffness in the building reduces suddenly. Hence stiffness has to

be increased at the floor where plan reduces suddenly in order to avoid torsion in the

building.

Keywords: High-rise building, seismic performance, IS 1893:2016, ASCE 7-16,

Forced Based Design, ETABS.

Cite this Article: Somil Khattar and Muthumani K, Seismic Performance of High-

Rise Building, International Journal of Civil Engineering and Technology, 9(3), 2018,

pp. 878–886.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=9&IType=3

1. INTRODUCTION

High rise structures are constructed in metropolitan cities of India for residential and

commercial building. Middle level cities like Ahmedabad, Pune, Indore, Bangalore,

Hyderabad and many other cities in India are also growing at faster rate due to

industrialization and modernization. Though, construction of high rise building in middle

Somil Khattar and Muthumani K


level cities will be same as that of metropolitan cities but to carry out as a mass scale; faster

construction technique, innovative design, economical construction material and some better

construction management technique needs to be evolved in view of environmental protection.

Compared to gravity loads, earthquake load effects (i.e. forces and moment in column) are

variable and it increases with increase in height. Earthquake resistant design of structure is a

function of height and location of the structure, total mass and soil characteristics. It has been

observed that structure can carry most of the earthquake load due to infill walls present in the

structure. As the height of structure increases, then the requirement for adequate stability (i.e.

resistance to overturning moment) and rigidity (i.e. resistance to lateral deflection) becomes

important. There are two ways to overcome these requirements in a structure. One is to

increase the size of the member beyond the strength requirement. However this approach is

not feasible, as it becomes impractical and uneconomical to increase the size of member

beyond its limit. Whereas, the second one is to change the form of the structure into more stiff

and stable to increase stability and to overcome the deflection. For safety purpose, the design

and analysis of buildings is very important. The forces and displacements are calculated for

various load combination conforming to Indian Standard Design Code and each structural

element will be designed for the critical one. Lateral forces due to earthquake loads increases

rapidly for high-rise buildings. Shear wall is one of the best lateral load resisting structural

systems, which is stiff as well as stable for building while designing for lateral loads.

2. BUILDING CONFIGURATION AND LOADING PARAMETERS

Residential building located in Indore district of Madhya Pradesh, India is considered for the

study. It consists of 3 basements, Ground Floor and 24 stories. It is located at Indore which lie

in seismic zone III according to IS 1893:2016 (Part 1). From geotechnical report, medium soil

is considered for designing purpose. Total height of the building (Ground floor plan to

Terrace slab) is 72 m. Plan dimension in X and Y direction is 34.17 and 26.80 m respectively.

Three basements are used for parking and service plant room. Ground Floor (GF), First

Floor (FF), Second Floor (SF) and Third Floor (TF) Slab Level are used for parking purpose.

Fourth floor slab is used for health club and swimming pool and above 20 stories are used for

residential purpose. Floor height for two lower basement and upper basement is 3.3 m and 3.8

m, respectively. All floor above Ground floor level are 3 m in height.

Conventional Flat slab with drop is provided at all the basement. At all typical level,

conventional beam-slab with core walls and shear wall is provided to resist lateral loads

imposed on the building. ETABS software is used for modelling of the building.

2.1. Materials Used

The concrete strength adopted varies depending on element and floor level. Grade of concrete

used for beams and slabs up to ground floor slab level is M35 and above ground floor slab, it

is M25. Grade of concrete used for columns and core wall varies as:

Up to 4th

floor roof slab level – M50

Above 4th

floor slab up to 8th


Above 8th



Above 13th



Above 17th


Seismic Performance of High-Rise Building


2.2. Loading Parameters

2.2.1. Dead Load and Live Load

Dead Load and Live Load are applied in the building as per IS 875(Part-1): (1987) and IS

875(Part-2) : 1987 [11]

, respectively.

2.2.2. Wind Load

Wind Load is applied as per IS 875(Part-3): 1987 [11]

. Basic wind speed (Vb) for Indore = 39

m/s. Design wind speed (Vz) = Vb x K1 x K2 x K3

Where,

K1 = Risk factor = 1

K2 = Terrain and height factor (Category 4 and Building Class B)

K3 = Topography factor = 1

Figure 1 Residential plan and 3D view of the building

3. ANALYSIS OF BUILDING AS PER IS 1893:2016 [9]

Building is designed as ductile shear wall with Ordinary moment resisting frame. As per IS

1893:2016 (Part 1), response reduction factor „R‟ is taken as 4.5. Time period is considered as

per IS 1893:2016, considering infill time period formula: Ta = 0.09 x h / √ d - (1)

Time period for x and y direction is found as 1.108 and 1.25 sec, respectively.

3.1. Linear Static Analysis

Static Analysis is carried out considering Infill Time period and only Earthquake force are

considered for this analysis. Result for Static Analysis are as shown below.



Table 1 Linear Static Analysis as per IS 1893:2016

Load Cases Base Shear (kN) Max Storey Drift Max Displacement

EQX 6017 0.0026 173.10 mm

EQY 5335 0.0021 141.03 mm

3.2. Dynamic Analysis

It is carried out with Response spectrum function and cases for spectrum are taken as SpecX

and SpecY with basic scale factor. Sa/g value is taken from response spectrum function

directly and hence scale factor for both the direction is taken as,

= (I g) / (2 R) = (1 x 9810) / (2 x 4.5) = 1090

Let wind forces along x and y direction be GustX and GustY and are calculated as per IS 875

- part 3. Results for dynamic analysis are as shown below.

Table 2 Response Spectrum Analysis as per IS 1893:2016

Load Cases Base Shear (kN) Max Storey Drift Max Displacement

SpecX 1760 0.0012 73.21 mm

SpecY 2238 0.0011 70.38 mm

Gust X 2880 0.0025 150.45 mm

Gust Y 1210 0.0006 43.75 mm

It is found from the results that base shear for GustX is higher than SpecX and SpecY.

Allowable storey drift in the building as per IS 1893:2016 - Cl 7.11.1.1 is 0.004. Maximum

Storey Drift for all the cases is found to be within the limits.

3.3. Modified Dynamic Analysis

As per IS 1893:2016 – Cl. 7.7.3; when the base shear computed with response spectrum (VB)

is less than base shear computed with equivalent static method (ṼB), than forces are to be

scaled with the ratio of (ṼB/VB). For Modified dynamic analysis, scale factor SpecX and

SpecY are to be modified as,

Scale factor for SpecX = 1090 x (6017/ 1760) = 3726.43

Scale factor for SpecY = 1090 x (5333/ 2238) = 2598.36

Results for Modified Dynamic Analysis are as shown below.

Table 3 Modified Dynamic Analysis as per IS 1893:2016

Load cases Base shear (kN) Max Storey drift Max displacement

SpecX 6020 0.0022 125.07 mm

SpecY 5336 0.0017 105.65 mm

Gust X 2880 0.0025 150.45 mm

Gust Y 1210 0.0006 43.75 mm



3.4. Modal Mass Participation

Modal mass participation of the building with design stiffness modifier is as shown below.

Table 4 Modal Mass Participation as per IS 1893:2016

Mode Time period(s) Ux Uy Rz

1 5.687 21.1 0.21 36.99

2 5.333 36.58 5.19 5.37

3 4.513 2.67 53.38 0.66

As per IS 1893:2016 Cl. 7.7.5.2, total modal mass participation should exceed 90%. As

far as this case is concerned, modal mass participation for 12 modes in x and y-direction is

91.55 and 89.32 respectively. It is found that modal mass participation along x-direction

exceeds 90% and it falls short in y-direction.

It is found from the results, that the first mode is governing in rotation. As per IS

1893:2016 Table 5 (i), fundamental torsional mode of oscillation shall not be governing in

first two modes. Hence first mode in rotation is not accepted by IS Code.

4. ANALYSIS OF BUILDING AS PER ASCE 7-16[13]

As per ASCE 7-16 Table 12.2- 1, building falls under category (F) i.e. Shear Wall–Frame

interactive system with Ordinary Reinforced Concrete Moment Frame and Ordinary

Reinforced Concrete Shear Wall. Following parameters are considered from ASCE 7-02,

Table 12.2-1 (F):

Response modification Co-efficient – 4.5

Over strength Factor – 2.5

Deflection Amplification Factor, Cd – 4

Design acceleration co-efficient (Sa/g) for medium type soil is, 1.36/T = 1.36/1.25 = 1.088

(as per IS 1893:2016)

Zonal spectral acceleration for Indore, (Z x Sa) = 0.174g

Seismic zonal map of United States is based on the ground acceleration. Zone 2A is

limited to 0.15g and Zone 2B is limited to 0.20g. As the zonal spectral acceleration for Indore

is 0.174g, it lies in Zone 2B. Hence, city named Bethel from Alaska is selected from United

States that lies in Zone 2B and that has similar Ground Acceleration as Indore. Spectral

Response acceleration parameters are considered in ETABS for zip-code 99559 (Bethel).

Time period of the building as per ASCE7-16 Cl. 12.8.2.1 is given as:

Ta = Ct hx - (2)

As per ASCE 7-16, Table 12.2-2, for building with concrete moment-resisting frame; Ct =

0.0466 and height of building from GF Level to Terrace Floor level, h = 72 m. Hence time

period of building, Ta = 2.187 sec. Time period of the building as per ASCE 7-16 is almost

double compared to time period as per IS 1893:2016.



4.1. Linear Static Analysis

Static Analysis is carried out considering Time period as per ASCE 7-16 and only Earthquake

force are considered for this analysis.

Table 5 Linear Static Analysis as per ASCE 7-16

Load Cases Base shear (kN) Max Storey Drift Max Displacement

EQX 6372 0.0053 356.37 mm

EQY 6357 0.0043 283.91 mm

It is found from the results that though the time period as per ASCE 7-16 is almost double

compared to IS 1893:2016; base shear value along x direction are found to be almost similar.

Along y direction, base shear as per ASCE 7-16 is slightly higher as compared to IS

1893:2016.

4.2. Dynamic Analysis

It is carried out with Response spectrum function similar to IS 1893:2016 and cases for

spectrum are taken as SpecX and SpecY with basic scale factor. Scale factor along both the

direction is similar to IS 1893:2016, i.e. 1090. Results for dynamic analysis are as shown

below.

Table 6 Response Spectrum Analysis as per ASCE 7-16

Load cases Base shear (kN) Max Storey drift Max Displacement

SpecX 4205 0.0025 141.24 mm

SpecY 5728 0.0027 168.15 mm

Gust X 2720 0.0015 92.85 mm

Gust Y 2720 0.0015 92.85 mm

As compared to IS 1893:2016, base shear for SpecX and SpecY are found to be doubled

with ASCE 7-16. Whereas, base shear value for GustX and GustY are almost similar in both

the case.

4.3. Modified Dynamic Analysis

For Modified dynamic analysis, base shear of SpecX and SpecY is matched with base shear

of EQX and EQY respectively. And hence, scale factor is again modified.

Scale factor for SpecX = 1090 x (6372/ 4205) = 1651.71

Scale factor for SpecY = 1090 x (6357/ 5728) = 1209.69

Results for modified dynamic analysis are as shown below.

Table 7 Modified Dynamic Analysis as per ASCE 7-16

Load cases Base shear (kN) Max Storey drift Max Displacement

SpecX 6372 0.0038 214.03 mm

SpecY 6356 0.003 186.61 mm

Gust X 2720 0.0015 92.85 mm

Gust Y 2720 0.0015 92.85 mm



5. RESULTS AND DISCUSSION

5.1. Comparison of Results between IS 1893:2016 AND ASCE 7-16

Allowable displacement of the building as per IS 1893:2016 Cl. 7.11.1.1 is 0.004 times height

of building which is 288 mm and allowable displacement of the building as per ASCE 7-16

Table 12.12-1 is 0.007 times height of building which is 504 mm.

Figure 2 Displacement Comparison between IS 1893:2016 and ASCE 7-16 along a) X direction and

b) Y direction

From Fig 2, it is found that as per IS 1893:2016, displacement is within the limits along

both the direction. Maximum displacement as per ASCE 7-16 is found to be exceeding the

allowable limit of IS 1893:2016 along x direction but as per ASCE 7-16 guidelines, it is

within the limits. Hence displacements along both the directions are within the limits of their

respective codal provision.

As per IS 1893:2016 Cl. 7.11.1.1., storey drift in any storey is limited to 0.004 and as per

ASCE 7-16 Table 12.12-1, allowable storey drift in any storey is limited to 0.007.

Figure 3 Storey drift Comparison between IS 1893:2016 and ASCE 7-16 along a) X direction and b)

Y direction

Allowable drift as per ASCE 7-16 is 0.007, but the results indicate that it is even within

the limits of IS 1893:2016 guidelines. Hence storey drift results are found to be safe with both

the codal provision.



5.2. Force Based Design (FBD)

Moment and Shear Force comparison for one exterior column and one interior column as

shown in fig below is carried out. Comparison is carried out between two floors; i.e. at fourth

floor and fifth floor plan level, where sudden change in plan occurs.

Figure 4 Interior and Exterior Column considered for comparison at (a) Fourth Floor Slab and (b)

Fifth Floor Slab

The size of interior and exterior column at 4th

floor slab level is 375 x 900 mm and 375 x

1050 mm, which gets reduced to 300 x 900 mm and 300 x 1050 mm, respectively. M3 and M2

are bending moment along major and minor direction, respectively. Results for two critical

load combinations is as shown below.

5.2.1. Moment Demand for Exterior Column

Moment demand for governing load combination is as shown below.

Table 8 BM and SF values for exterior column with load combination 1.5 (DL+EQX)

Load Combination - 1.5 (DL+EQX)

STOREY M3 (kN.m) M2 (kN.m) V2 (kN) V2 (kN)

5th Floor Slab 170.57 -137.66 -22.16 -30.27

4th Floor Slab 205.34 -154.71 -61.58 -84.26

Moment capacity of the exterior column is found to be 598.0 kN.m and 318.93 kN.m at 4th

floor slab and 5th

floor slab level, respectively with Pu-Mu curve from SP 16(1980). It is found

that moment capacity of the column at 4th

floor slab level i.e. 598.0 kN.m is greater than

moment demand i.e. 205.34 kN.m. Also it is found that moment capacity of the column at 5th

floor slab level i.e. 318.93 kN.m is greater than moment demand i.e. 170.57 kN.m. Hence the

column is safe at both the floors.



5.2.2. Moment Demand for Interior Column

Moment demand for governing load combination is as shown below:

Table 9 BM and SF values for interior column with load combination 1.5 (DL+EQX)

Load Combination - 1.5 (DL+EQX)

STOREY M3 (kN.m) M2 (kN.m) V2 (kN) V2 (kN)

5th Floor Slab -194.67 48.80 -98.27 -17.94

4th Floor Slab -260.17 126.18 -142.88 -83.32

Moment capacity of the exterior column is found to be 569.53 kN.m and 236.93 kN.m at

4th

floor slab and 5th

floor slab level, respectively with Pu-Mu curve from SP 16(1980) [10]

.

It is found that moment capacity of the column at 4th floor slab level. i.e. 569.53 kN.m is

greater than moment demand i.e. 260.17 kN.m. Also it is found that moment capacity of the

column at 5th floor slab level i.e. 236.93 kN.m is greater than moment demand i.e. 194.67

kN.m. Hence interior column is safe at both the floors.

5.3. Displacement Limits

As per IS 1893:2016 Table 5 (i), building is said to be irregular in torsion if the maximum

deflection at one end of the floor is more than 1.5 times the minimum deflection at the far end

of the same floor. There is sudden reduction in plan area from 4th

floor to 5th

floor slab level.

Hence, results are found for Earthquake forces along both the direction at 4th

floor slab level

and 5th

floor slab level.

Figure 5 Nodes considered to find displacement for EQX at (a) Fourth Floor Slab and (b) Fifth Floor

Slab Level



Figure 6 Nodes considered to find displacement for EQY at (a) Fourth Floor Slab and (b) Fifth Floor

Slab Level

Let us consider the ratio of maximum horizontal displacement to minimum horizontal

displacement at the far end of the same floor be ‘m’. Displacement result for 4th Floor Slab Level are

as shown below.

Table 10 Displacement results at 4th Floor Slab Level

DISPLACEMENT (in mm)

CASE PARAMETERS At Node 1 At Node 2 m

Static EQX 86.16 32.25 2.67

Dynamic SpecX 18.21 11.75 1.54

Static EQY 32.91 44.99 1.36

Dynamic SpecY 10.27 10.97 1.06

At 4th

floor slab level, M value exceeds 1.5 for EQX and SpecX. Moreover, it is also

found that m value for EQX is very high compared to the allowable limit. Hence this value

has to be reduced. Displacement results for 5th

Floor Slab Level are as shown below.

Table 11 Displacement results at 4th Floor Slab Level



Static EQX 102.07 63.58 1.61


Static EQY 40.15 54.73 1.36


Similar to 4th

floor slab level, m value exceeds 1.5 for all EQX and SpecX at 5th

floor slab

level. It is found that m value is slightly exceeding the allowable limit. Hence this value has to

be reduced.



6. CONCLUSIONS

It can be concluded that though the time period value as per ASCE 7-16 is almost double

compared to IS 1893:2016, forces are found to be almost similar for both the cases. The

building was found safe as per Forced Based Design but due to irregularity in the plan and

sudden reduction of plan area between two floors, ratio of maximum displacement at one end

to the minimum displacement at the farther end exceeded the ratio of 1.5 which violates the

codal provision as per IS 1893(Part-1):2016 – Table 5 (i). Also torsion was found to be

prevalent in the first mode.

There is sudden reduction in plan area from 4th Floor slab to 5th Floor slab which results

in sudden reduction of stiffness from 4th Floor slab to 5th Floor slab. To overcome this

problem, cross-bracings must be provided in the periphery of the building along x direction as

shown in Fig. 7 starting from 5th

Floor Slab to 9th

Floor slab level.

Figure 7 Provision of bracing

By providing bracings from 5th

Floor slab to 9th

Floor slab level, it is found that torsional

mode of oscillation in third mode is greater than first two modes. Results for modal mass

participation of the building after provision of bracings are as mentioned in Table 12.

Table 12 Modal mass participation of building after addition of bracing

Mode Time period(s) Ux Uy Rz

1 5.09 31.83 7.4 7.77

2 4.391 12.57 48.14 0.86

3 4.00 18.02 4.71 35.38

Hence torsional irregularity in the building is overcome by providing bracings above

certain storey where sudden reduction in plan area is found.

Displacement result for 4th

Floor Slab Level and 5th

Floor slab level after provision of

bracings from 5th

Floor slab level to 9th

Floor slab level are as shown in Table 13 and Table

14, respectively.

Table 13 Displacement results at 4th Floor Slab Level after provision of bracings



Static EQX 61.47 40.92 1.50


Static EQY 32.23 43.42 1.35




Table 14 Displacement results at 5th Floor Slab Level after provision of bracings



Static EQX 64.51 61.19 1.05


Static EQY 39.27 52.60 1.34


As per IS 1893:2016, Fig. 3A, m value should not exceed 1.5. From results, it is observed

that m value at both the floor is found to be within the limits. „m‟ value for EQX at 4th Floor

slab level is 1.5, but still it is within the limits.

Stiffness reduces gradually between two floors where plan reduces. Hence by providing

cross-bracings up to few floors above the level where plan reduces suddenly, torsion was

brought to third mode as recommended by IS 1893(Part-1):2016 and also the ratio of

maximum displacement at one end to minimum displacement at far end was brought within

the limit of 1.5.

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Documents

SEISMIC PERFORMANCE OF HIGH-RISE BUILDING · maximum considered earthquake by response spectrum analyses using ETABS software ... stiffness in the building ... Fourth floor slab is