Earth quake disaster mitigation (EQDM) through engineering design

Materials Today: Proceedings xxx (xxxx) xxx

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Earth quake disaster mitigation (EQDM) through engineering design K. Srividhya a, A. Mohan a, M. Tholkapiyan b, A. Arunraj a a b

SRM Easwari Engineering College, Department of Civil Engineering, 600089, Ramapuram, Chennai, India Saveetha School of Engineering, Saveetha Institute of Medical and Technical Sciences, Department of Civil Engineering, 602105, Tandalam, Chennai, India

a r t i c l e

i n f o

Article history: Received 3 October 2019 Received in revised form 28 November 2019 Accepted 29 November 2019 Available online xxxx Keywords: Soft soil Medium soil Hard soil Seismic weight Base shear Retrofit Public awareness

a b s t r a c t Frequent earthquake disasters in our country have clearly illustrated the need for immediate action in all aspects. Natural disasters are certain to happen, but it is certainly possible to mitigate the effects of disasters. Here we attempt to obtain best possible methods and measures for earth quake disaster mitigation through engineering approach at a micro level. Earthquake disaster mitigation and management are two different aspects when dealing with disaster preparedness. While mitigation efforts precede the disaster event, the management (post disaster event) can be done only by authorities with resources and control over various departments. Rather than spending money on relief after disaster, investments in pre-preparedness will always lead to reduced effects and yield sustainable development generating awareness and confidence among the people. In our present study, Chennai is considered from among the likely disaster zones in India. Possible mitigation measures are highlighted with particular reference to earthquake resistant foundation design for buildings and structures. Apart from the dedicated design and implementation, public cooperation and discipline are more important for reaping the full benefits during the times of crisis. The ideas developed in this paper will certainly go a long way to enhance capabilities of students of Engineering and Architecture to create awareness and help them consider mitigation measures at a micro level while planning and implementing any new project. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Materials Engineering and Characterization 2019.

1. Introduction On Friday, 26 January 2001, a massive earth quake measuring 7.6 magnitude in Richter scale, struck the western region of India resulting in a death toll of around 15,000 people. A thorough study made later indicated that Over 58.6 per cent of land in India is highly vulnerable to earthquakes and 38 cities fall under moderate to high risk seismic zones [1]. Monthly data are now available from Indian Meteorological Department, which can help us to predict disaster prone areas and the seasonality of disasters. All major cities in India such as Delhi, Chennai, Pune, Greater Mumbai, Kochi, Kolkata, Thiruvananthapuram, Patna, Ahmedabad, and Dehradun are the cities falling in the vulnerability zone to a varying extent. A large number of buildings constructed in these places in the past have not been made earthquake resistant [4]. While many of the large multistory and commercial buildings have adopted earthquake resistant design, the residential buildings (3 floors and less) are still being designed and constructed without considering additional measures for resisting earthquake forces.

It is therefore felt necessary to carry out EQDM through micro level design for such structures. A G+3 (50 m  30 m) residential building model is taken for study and foundation design worked out for the same at different sites with different soil type conditions. An attempt has been done to evaluate the best possible type of foundation for each soil type, which is also cost effective. A comparative study is done for economic analysis.

2. Soil profiles in Chennai For the purpose of this presentation, Chennai city has been chosen to evaluate the possible earthquake impact and the mitigation measures that will be required for the structures. After the Bhuj earthquake, Indian Standard IS: 1893 was revised and Chennai city was upgraded from zone II to zone III which leads to a substantial increase of the design ground motion parameters. Chennai is located at 12.75◦–13.25◦N and 80.0◦–80.5◦E latitude and longitude on the southeast part of India and in the northeast

https://doi.org/10.1016/j.matpr.2019.11.303 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Materials Engineering and Characterization 2019.

Please cite this article as: K. Srividhya, A. Mohan, M. Tholkapiyan et al., Earth quake disaster mitigation (EQDM) through engineering design, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.303

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part of Tamil Nadu. It is India’s largest fourth metropolitan city and it covers an area of 1238 km2. The sea bed is flat and sandy for about one km from the sea shore. The eastern and southern areas of the city consist of crystalline bedrock; whereas the western and northern areas have Gondwana deposits as a composition of alluvium deposits. The entire area is covered by alluvium deposits by the two main rivers, namely, Cooum and Adyar [3]. The marine sediments containing clay-silt sands and charnockite rocks are found in the eastern and northern parts. The western parts are composed of alluvium and sedimentary rocks. The laterites rocks are found in form of thin layers is also found at some other places in chennai. Rounded pebbles, irregular shaped Gravels and small boulders have been seen at more number of different locations at different depths. It has been seen in common, that the eastern coastal zone is extremely sandy, while the north-western parts of areas are mostly clayey in condition [2]. Fig. 2.1 shows the soil profiles in different areas of Chennai city map and Fig. 2.2 shows the different soil profiles in and around Chennai region.

3. Micro level design for EQDM 3.1. General data Fig. 3 shows the proposed structure for G+3 building (50 m  30 m) with each floor height 4 m. The seismic analysis of the structure has done using the ETAB’s software version 9.7. All the loads applied on the structure are based on IS875. Scale factors used are as per IS 456. Seismic design was done using IS1893. Different types of foundation considered for analysis and comparison are shallow foundation, combined footing, raft foundation and pile foundation. Soil properties used for different soil conditions in our design are given in Table 1 [4].

Fig. 2.2. Soil profiles in Chennai.

Unit weights considered for different materials used in our design are for concrete (M30) 25 kN/m3, cement mortar 24 kN/m3, brick 20 kN/m3, and water 10 kN/m3. Dead loads such as self weight and floor finish are considered for typical and terrace floor slab. Live loads considered are for living area 5 KN/m3 and terrace area 3 KN/m3. Wind loads are calculated as per standards for the given structure and given in Table 2. Wall loads considered are for 230 mm thick peripheral wall 15 KN/m2 and 100 mm thick interior wall 7.5 KN/m2. 3.2. Seismic design Determination of design earthquake forces is assigned by either (i) Static loading or (ii) Dynamic loading analysis [4]. In the above method, different types of safety factors are applied to various loads to arrive at the ultimate design load. Dynamic load analysis was involved rigorously in the analysis of the structural system using dynamic response of the structure. Seismic base shear values calculated for various types of soil conditions are given in Table 3. Shear force and moment diagrams are shown in Fig. 3.1 and Fig. 3.2 respectively. 3.3. Analysis and design (including seismic analysis)

Fig. 2.1. Chennai City map.

Analysis part is done by using ETABS Software. Analysis methods are set before the analysis to be carried out based on Codes and the analysis is done with a scale factor 1. The number of safety factor was initially set as 1.5. After analyzing the structure, if the participation factor for cumulative mass is supposed to be less than 95 percentages, then it is modified accordingly. If the base shears values are above the earth quake load case a new scale factor is

Please cite this article as: K. Srividhya, A. Mohan, M. Tholkapiyan et al., Earth quake disaster mitigation (EQDM) through engineering design, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.303

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K. Srividhya et al. / Materials Today: Proceedings xxx (xxxx) xxx Table 1 Soil properties. S. No.

Soil type

1

Normal dry soil a. Without undercut b. With undercut Wet soil due to presence of Sub soil water/Surface water Black cotton soil (a) In dry portion (b) In wet portion Sandy soil (a) With clay content 0–5% (b) With clay content 5–10% Fissured rock/Soft rock with undercut (a) In dry portion (b) In wet portion Hard rock Normal hard dry soil (Morrum) With undercut

2 3

4

5

6 7

AEF deg

Density kg/cum

LBC kN/sq.m

30 30

1440 1600

250 250

15

940

125

0 0

1440 940

125 125

10 20

1440 1440

250 250

20 10 –

1700 940 –

625 625 1250

30

1600

400

Table 2 Wind loads. STOREY

Height (m)

K2

Vz (km/s)

Pz = 0.6Vz2 (kN)

Load X in direction (kN)

Load in Y direction (kN)

First Second Third Terrace

4.0 8.0 12.0 16.0

0.930 0.930 0.950 0.972

46.50 46.50 47.50 48.60

1.297 1.297 1.353 1.417 Total

250.97 167.31 174.54 91.40 684.22

466.92 311.28 324.72 170.04 1272.96

k1 factor for the class of structure under consideration = 1, k2 is the terrain, Height and structure size factor = 1; k3 is the topography factor.

3.4. Cost estimation Table 3 Seismic loads. Soil type

Rocky

Medium

Clay

Zone factor Importance factor Response reduction factor Seismic weight [MN] Ta [X and Y direction] with infill Ta [X and Y direction] without infill Sa/g with infill Sa/g without infill Ah [X and Y direction] with infill Ah [X and Y direction] without infill Average Base shear [MN]

0.16 1.5 5 235.98 0.263 0.6 2.5 1.667 0.06 0.04 11.74

0.16 1.5 5 235.98 0.263 0.6 2.5 2.267 0.06 0.05 12.92

0.16 1.5 5 235.98 0.6 0.6 2.5 2.5 0.06 0.06 14.06

The estimate for the different materials used for the construction of multi-storied building have been approximately calculated and the total estimate for the cost of foundation for the structure under study (50 M  30 M) is done at the prevailing rates in Chennai and shown in Table 4.  The approximate increase in cost of foundation due to seismic consideration is of the order of 1.3 to 2 lakhs, which is very minimal compared to the overall cost of the structure.  Recommended foundations for different soil conditions and seismic considerations are given in Table 5. Apart from the foundations, other structural elements also need to be designed and detailed to achieve EQDM.

calculated and again assign the model, which is to be analyzed. The analyzed base shear value c from the code and by the software calculated with the new scale factor must be same.

i. Columns and beams at corners, ii. Columns and beams at peripheral stages,

Fig. 3.1. Shear force diagram.

Please cite this article as: K. Srividhya, A. Mohan, M. Tholkapiyan et al., Earth quake disaster mitigation (EQDM) through engineering design, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.303

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Fig. 3.2. Moment diagram.

4. Conclusion

Table 4 Comparison of foundation costs. Type of soil

Hard soil

Medium soil

Soft soil

Type of footing

Isolated footing Rs. In Lakhs 3.61

Isolated footing

Pile foundation

3.44

4.50

4.93

4.96

6.34

1.32

1.52

1.84

Foundation Without seismic load consideration With seismic load consideration Increase due to seismic considerations

Table 5 Recommended foundations.

An engineering analysis for residential buildings at Chennai confirms that special attention needs to be taken by the owners at the initial construction stage itself. It is worth spending an extra cost of Rs.1.3 lakhs to 2.0 lakhs on constructions by adopting seismic considerations voluntarily. Investments in preparedness and prevention will always yield sustainable results rather than spending money on relief after disaster. The best possible way of EQDM is to ensure your building has desired seismic resistance to the extent possible. People need to be aware of measures to be taken for structural safety. Public cooperation with authorities is essential in tackling the earthquake effects. Together we progress and together we are safe. Declaration of Competing Interest

Type of soil

Hard soil

Medium soil

Soft soil

Recommended type of footing with seismic load consideration

Isolated footing with tie beams

Isolated footing with tie beams/ Raft foundations

Raft foundations / Pile foundation

iii. Cantilevered beams for balcony situated at covered framed buildings, iv. Stair case parapet walls and lift walls, v. Columns at high levels, vi. Over Head Water tanks, vii. Infill & interior walls and partition walls, viii. Beams and Columns and their junctions at all levels as a precautionary measure. In the case of existing buildings in sensitive zones, suggested measures to strengthen/retrofit the building structures with seismic belts [5]. i. Horizontal Seismic Belts considered just above the lintel level of Door and Window opening. ii. Horizontal belts just below the roof. iii. Vertical seismic load consideration at belts of wall junctions. iv. Seismic belt around doors and windows containing galvanized welded steel wire mesh as reinforcement. v. Seismic belts around the gable wall.

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgement We acknowledge Government of India, Ministry of Home affairs, Disaster management, National disaster management framework, national programme for capacity building of architects in earthquake risk management; all of them have been very useful for initiating and preparing this project and very useful in completion of research work. References [1] IS 1893 Part 1:2002.Map of Seismic Zones of India. [2] G.P. Ganapathy, First level seismic microzonation map of Chennai city a GIS approach, Centre Disaster Mitigation Manag. 11 (2011) 549–555. [3] A. Boominathan, G.R. Dodagoudar, A. Suganthi, R. Uma Maheswari, Seismic hazard assessment of Chennai city considering local site effects, J. Earth Sys. Sci. 117 (2008) 853–863. [4] A. Mohan, M. Tholkapiyan, Behaviour of shear wall in earth quake resistant structures, Int. J. Adv. Res. Trends Eng. Technol. 5 (2018) 320–330. [5] Satish Kumar, S.R., Santha Kumar, A.R., Design of Steel Structures, Indian Institute of Technology Madras, Chennai 600 036, India.

Further reading [6] An Earthquake Preparedness Guide, National Diasaster Management Division, Ministry of Home Affairs, New Delhi, India.

Please cite this article as: K. Srividhya, A. Mohan, M. Tholkapiyan et al., Earth quake disaster mitigation (EQDM) through engineering design, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.303