1 Prof. Sarosh H Lodi Pakistan Building Code – Seismic Provisions 2007 September 9, 2013 Continuing Professional Development Short Course Series and Aga.

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Prof. Sarosh H Lodi

Pakistan Building Code – Seismic Provisions 2007September 9, 2013

Continuing Professional Development

Short Course Series

and

Aga Khan Planning and Building Services, Pakistan

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DEDICATEDTO

THOUSANDS OF CHILDREN, WOMEN AND MENWHO

LOST THEIR LIVESIN

THE 8th OCTOBER 2005 EARTHQUAKE

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CHAPTER 1: SCOPECHAPTER 2: SEISMIC HAZARDCHAPTER 3: SITE CONSIDERATIONSCHAPTER 4: SOILS AND FOUNDATIONSCHAPTER 5: STRUCTURAL DESIGN REQUIREMENTS

DIVISION-I General Design RequirementsDIVISION-II Snow LoadsDIVISION-III Wind DesignDIVISION-IV Earthquake DesignDIVISION-V Soil Profile Types

CHAPTER 6: STRUCTURAL TESTS AND INSPECTIONSCHAPTER 7: REINFORCED CONCRETECHAPTER 8: STRUCTURAL STEEL

PART I. Structural Steel BuildingsPART II. Composite Structural Steel and Reinforced Concrete Buildings

CHAPTER 9: MASONRYCHAPTER 10: TIMBERCHAPTER 11: ARCHITECTURAL ELEMENTSCHAPTER 12: MECHANICAL & ELECTRICAL SYSTEMS

APPENDIX-A BACKGROUND FOR SEISMIC ZONING MAP

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CHAPTER 1: SCOPE

Objective and General Principles

The objective of the criteria and earthquake provisions described in this code is to prescribe the minimum requirements for the earthquake design and construction of buildings and building-like structures and/or their components subjected to earthquake ground motions.

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Scope

• Requirements of these provisions shall be applicable to reinforced concrete buildings, steel buildings, building-like structures, masonry and timber buildings.

• In addition to the buildings and building-like structures, non-building structures permitted to be designed in accordance with the requirements of these provisions are limited to those specified in Chapter 5.

• In this context bridges, dams, harbour structures, tunnels, pipelines, power transmission lines, power generation plants including hydel, thermal and nuclear power plants, gas storage facilities, special defence installations, underground structures and other structures designed with analysis and safety requirements that are different than those for buildings are outside the scope of this code.

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• Requirements of these provisions shall not be applied to the buildings equipped with special system and equipment between foundation and soil for the purpose of isolation of building structural system from the earthquake motion, and to the buildings incorporating other active or passive control systems.

• Requirements to be applied to structures which are outside the scope of these provisions, shall be specifically determined by the Departments/Autonomous Organizations supervising the construction and such structures shall be designed to those provisions until their specifications are prepared by the Competent Authority.

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CHAPTER 2: SEISMIC HAZARD

This Chapter defines the minimum seismic hazard that has to be considered for the design of buildings

CHAPTER 3: SITE CONSIDERATIONS

The selection of suitable building sites shall be carried out based upon their geology/ stratigraphy, distance from the causative fault, the liquefaction potential of site, earthquake induced land sliding, and presence of sensitive clays any other relevant geotechnical aspects, as provided in this chapter.

CHAPTER 4: SOILS AND FOUNDATIONS

Determination of soil conditions of buildings to be constructed in seismic zones, design of reinforced concrete, structural steel, timber and masonry building foundations and soil retaining structures shall be performed, along with the applicable codes and standards in relevant areas, primarily in accordance with the rules and requirements of this section.

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CHAPTER 5: STRUCTURAL DESIGN REQUIREMENTS

This chapter prescribes general design requirements applicable to all structures regulated by this code.

DIVISION-I General Design RequirementsDIVISION-II Snow LoadsDIVISION-III Wind DesignDIVISION-IV Earthquake DesignDIVISION-V Soil Profile Types

CHAPTER 6: STRUCTURAL TESTS AND INSPECTIONS

The owner or the engineer or the architect incharge acting as the owner’s agent shall employ one or more special inspectors who shall provide inspections during construction on the types of work listed under Section 6.1.5.

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CHAPTER 7: REINFORCED CONCRETEThis Chapter contains special requirements for design and construction of cast-in-place reinforced concrete members of a structure for which the design forces, related to earthquake motions, have been determined on the basis of energy dissipation in the nonlinear range of response as specified in Chapter 5.

CHAPTER 8: STRUCTURAL STEEL

The Seismic Provisions for Structural Steel Buildings, hereinafter referred to as these Provisions, shall govern the design, fabrication and erection of structural steel members and connections in the seismic load resisting systems (SLRS) and splices in columns that are not part of the SLRS, in buildings and other structures, where other structures are defined as those structures designed, fabricated and erected in a manner similar to buildings, with building-like vertical and lateral load-resisting-elements. These Provisions shall apply when the seismic response modification coefficient, R, (as specified in the Chapter 5, Table 5-N) is taken greater than 3, regardless of the seismic design category. When the seismic response modification coefficient, R, is taken as 3 or less, the structure is not required to satisfy these Provisions, unless specifically required by the applicable building code.

PART I. Structural Steel BuildingsPART II. Composite Structural Steel and Reinforced Concrete Buildings

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CHAPTER 9: MASONRY

This chapter covers the structural design of un-reinforced, reinforced and confined load bearing and non-load bearing walls, constructed with masonry units permitted in accordance with this chapter. The provisions of this section do not apply to walls constructed in mud mortars.

CHAPTER 10: TIMBER

Design of timber buildings or building-like structures constructed in seismic areas with load-bearing walls carrying both vertical and lateral loads as well as floors made of timber skeleton shall be performed primarily in accordance with the requirements of this Chapter.

CHAPTER 11: ARCHITECTURAL ELEMENTS

CHAPTER 12: MECHANICAL & ELECTRICAL SYSTEMS

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APPENDIX – A

BACKGROUND FOR SEISMIC ZONING MAP

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Being located close to the collision boundary of the Indian and Eurasian plates, Pakistan lies in a seismically active zone. Owing to high population density near seismically active areas, it is imperative that buildings should withstand the seismic hazard to which these may be exposed during their life time.

OVERVIEW

Seismic Zoning map is prepared on a rigorous exercise based on compilation of geological, tectonic and seismicity data from Pakistan and its immediate surroundings. Only a brief account of salient seismotectonic features, seismicity and methodology adopted for seismic hazard zonation are mentioned here.

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Pakistan is characterized by extensive zones of moderate to high seismicity, induced by the regional collisional tectonics associated with Indian and Eurasian plates and resulting in manifestation of great Himalayan and associated mountain ranges.

The geographic domain of Pakistan comprises a network of active seismotectonic defined five broad seismotectonic zones

1) Himalayan seismotectonic zone in the north,

2) Suleman-Kirthar thurst-fold belt,

3) Chaman-Ornach Nal Trasform Fault Zone,

4) Makran Subduction Zone in the west, and

5) Run of Kutch Seismotectonic Zone in the southeast.

The Pamir-Hinukush Seismic Zone straddles across Afghanistan and Tajikistan outside Pakistan but in close vicinity of the NW Pakistan comprising District Chitral.

Major Faults of Pakistan

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1. Main Karakoram Thrust

2. Raikot Fault

3. Panjal-Khairabad Thrust

4. Riasi Thrust

5. Salt Range Thrust

6. Bannu Fault

7. Chaman Transform Fault

8. Quetta-Chiltan Fault

9. Pab Fault

10.Allah Bund Fault

11.Hoshab Fault

12.Makran Coastal Fault

Major Faults of Pakistan

Major active faults of Pakistan and surrounding areas that strongly influence the seismic hazard are listed below:

13.Main Mantle Thrust

14.Main Boundary Thrust

15.Himalayan Frontal Thrust

16.Jhelum Fault

17.Kalabagh Fault

18.Kurram Fault

19.Ornach-Nal Transform Fault

20.Kirthar Fault

21.Kutch Mainland Fault

22.Nagar Parkar Fault

23.Nai Rud Fault

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SEMINAR ACI CODE

After NESPAK 2006

Tirich Mir-Misgar F.MKT

MMT

Panjal T.

MBT

Raisi T.Jhelum F.

Kalabagh F.

SRT

Indus-Kohistan F

Muzafarabad T.

Kurram T.

Waziristan T.

Sulaiman Frontal T.

Kirthar F.

Pab F.

OrnachNal F.MakranSubduction Zone

Chaman F.

Ghazaband T.

Hoshab F.

Hoshab F.

Rann of Kuchh F.

Fault Map of Pakistan

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The information about earthquakes in this region have been used based upon earthquake data from regional data catalogues compiled by

• International Seismological Centre (ISC)

• National Earthquake Information Centre (NEIC) of USGS, and

• from earthquakes recorded by local networks of Pakistan

Meteorological Department, Pakistan Atomic Energy

Commission (PAEC) and Water & Power Development

Authority.

Seismicity

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Probabilistic Seismic Hazard Assessment (PSHA) procedure was used for seismic hazard analysis of Pakistan - as per international practice and guidelines for seismic hazard evaluation and seismic hazard mapping for Building Codes.

Seismic Hazard Evaluation Procedure

Seismic activity of seismic source is specified by a recurrence relationship, defining the cumulative number of events per year versus the magnitude.

Principle developed by Cornell (1968) is used to evaluate probability of peak ground acceleration due to an earthquake.

This approach combines the probability of exceedance of the earthquake size and probability on the distance from the epicenter to the site.

1. PSHA Methodology

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For seismic sources entire area of Pakistan was divided into seventeen area source zones based on their homogeneous tectonic and seismic characteristics, keeping in view the geology, tectonics and seismicity of each area source zone.

Eight area seismic source zones in the northern part of Pakistan

Hindukush, Pamir, Kohistan, Hazara, Himalayas, Salt Range-Potwar, Bannu and Punjab.

Nine area source zones in southern part

Suleiman, Sibbi, Kirthar, Kurram-Chaman, Indus plateform, Rann of Kutch, Cholistan-Thar desert, Chagai and Makran

2. Source Modeling

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Equations likeN (m) = f (m, t) (1)Log N(m) = a – b m (2)

were used with a composite list of earthquakes for areas in and around Pakistan which provided the necessary database for the computation of values for each area source zone.

For data to be used in seismic hazard analysis, all the magnitudes were converted to moment magnitude (MW) by the following equations.

MW = 0.67 MS + 2.07 for 3.0< MS < 6.1MW = 0.99 MS + 0.08 for 6.2< MS < 8.2MW = 0.85 mb + 1.03 for 3.5< mb < 6.2

3. Earthquake Recurrence Model

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To each area source zone, a maximum magnitude potential was assigned based on the maximum observed seismicity in the historical seismic record or enhancing by 0.5 magnitude the maximum observed magnitude in the instrumental seismic record for that area seismic source zone.

4. Maximum Magnitude

Due to lack of sufficient strong–motion data covering a larger range of magnitudes and distances, attenuation relationships for the South Asian Region could not be developed so far.

For probabilistic hazard analysis, the attenuation equation of Boore et al. (1997) along with three other equations developed during 1996 to 2004 have been used with equal weightage (25%) to each equation.

5. Attenuation Equations

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The probabilistic hazard analysis was carried out by using EZ-FRISK software developed by Risk Engineering Inc. of Colorado, USA.

As the purpose of the PSHA was to develop seismic hazard contour map, Gridded- Multisite module of EZ-FRISK software was used.

The required parameters for all the fourteen area seismic source zones and twenty eight fault seismic sources were fed to the software. The results of the hazard analysis obtained at each grid point are presented in the form of total hazard from all the seismic sources modeled The ground motion associated with 10% probability of exceedance in 50 years (475 years return period) was calculated at each grid point. From the results obtained at 0.1 degree interval, contours of Peak Ground Acceleration (PGA) values were plotted through GIS software.

5. Results of PSHA

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RESULTS OF PSHA - PEAK GROUND ACCELERATION

VALUES

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On the basis of PGA values obtained through PSHA, Pakistan was divided into five seismic zones in line with UBC97. The boundaries of these zones are defined on the following basis:

Zone 1 0.05 to 0.08g

Zone 2A 0.08 to 0.16g

Zone 2B 0.16 to 0.24g

Zone 3 0.24 to 0.32g

Zone 4 > 0.32g

The seismic zoning map of Pakistan developed on this basis is shown in Fig. 2.1. Each structure shall be assigned a seismic zone factor Z in accordance with this map or Table 5-I given in Chapter 5 of the Code.

6. Seismic Zoning

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SEISMIC ZONING MAP OF PAKISTAN

Zone 1 0.05 to 0.08g

Zone 2A 0.08 to 0.16g

Zone 2B 0.16 to 0.24g

Zone 3 0.24 to 0.32g

Zone 4 > 0.32g

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SEMINAR ACI CODE

HYDERABAD BUILDING AND

TOWN PLANNING REGULATIONS-

2007

???

KBCADHAFCCCKPT

RC Buildings

Brick Masonry

Block Masonry

Adobe Masonry

Stone Masonry

Wood Reinforced Structures

Others

Building Typology

RC reinforced concrete moment resisting frame buildings

M1 Brick MasonryM2 Block MasonryM3 Stone MasonryM4 Adobe MasonryM5 Wood Reinforced MasonryOO Others

Summary of Building Typology

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Percentage of Building Types In Pakistan

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