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Title:

Blast Resistant Structures

COVER SHEET DOC. NO.:W0709

0 18.01.2009 For Implementation S.P. H.S. M.H.E

REV. DATE DESCRIPTION PREPARED CHECKED APPROVED

Page 1 of 10

Hampa Energy

Engineering & Design Company

DOCUMENT TITLE:

WORK INSTRUCTIONFOR

BLAST RESISTANT STRUCTURES

TOTAL PAGES : 10

Thisdocumentwith

allitsrightsisthepropertyofHEDCo.andmustbeheldin

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Title:

Work Instruction forBlast Resistant Structures

DOC. NO.:W0709 Rev. 0

Page 2 of 10Thisdocumentwitha

llitsrightsisthepropertyofHEDCo.andmustbehel

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sure,reproductionorotheruseofthedocumentinwholeor

artsistomadewitho

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Hampa Energy


REV.

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Index: Page

1 Purpose 4

2 Scope 4

3 Definitions 4

4 Reference 4

5 Responsibilities 4

6 Procedure 5

6.1 Type of Design 56.2 Input Parameters 5

6.2.2 Soil Data 56.2.3 Structural Design Capacity 5

6.3 Load 6

6.3.1 Dead Load 6

6.3.2 Live load 76.3.3 Blast load 7

6.4 Load Combinations 86.5 Structural Design Requirements 96.6 Foundation Design 10

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1 PURPOSEThis work instruction represents the method of design for blast resisting structures inpetrochemical facilities.

2 SCOPE

Blast resistant buildings are limited to rectangular box-shaped structures such as control roomand substation, one or two story that are specified to be blast resistant.

Note: This work instruction serves as a guide only. The skillful originator should have a clearunderstanding and complete knowledge of the job and the pertinent literature.

3 DEFINITIONS

4 REFERENCE

Document title Department

Architectural drawings structure

Reference codes

1) Army TM 5-1300 Structures To Resist The Effect Of Accidental Explosion, 1990

2) Design Of Structures To Resist Nuclear Weapons Effects ASCE Manual 42,1985.

3) Smith P.D., Hethering Ton.J.G. Blast And Ballistic Loading Of Structures, 1994

4) Project Specifications:

- Blast resistant structures

- Concrete design and materials

5 RESPONSIBILITIES

Responsibilities for preparation, checking & approval of this document are as follows:

Preparation : Structural Senior or Junior EngineerChecking : Structural Senior Lead EngineerApproval : Structural Lead Engineer

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6 Description

6.1 TYPE OF DESIGN

- Reinforced concrete to be used for blast resistant structures to provide better continuity andlateral performance.

- Blast resistant concrete structures should be designed by ultimate strength design method(U.S.D)

- 3 dimensional moment resisting frame should be modeled by computer analysis and designprogram.

6.2 INPUT PARAMETERS

6.2.1 Geometrical configuration clearly shows all dimensions, no. of stories. Location of doorsobtained from architectural drawings.

6.2.2 Soil Data

- The following requirements should be assigned from soil report and other projectspecification documents.

- Density of soil and allowable pressure

- Active, passive and rest coefficient of the soil

- Modulus of sub grade reaction

- Ultimate capacity of the soil

- Water level

Note: In the case of pile foundation the following additional parameters are required:

- Allowable vertical and horizontal loads of the pile- Vertical and horizontal stiffness of the piles- Ultimate capacity of the piles

6.2.3 Structural Design Capacity

Dynamic capacity of any structural element shall be determined according to the plastic designmethod for structural steel and the ultimate strength method for reinforced concrete orreinforced concrete masonry as provided by ASIC specification and ACI standard, respectively,except that :

a) Dynamic strengths of materials should be used as mentioned in tables 1&2.

b) Capacity reduction factor can be increased by percent.

c) The dynamic elastic modulus of concrete shall be 1.25 times the static value. For thestructural steel it shall be taken as the static value.

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TABLE - 1

DYNAMIC STRENGTH OF STRUCTURAL AND REINFORCING STEEL( RELATIVE TO NORMAL SPECIFIED MINIMUM YIELD STRENGTHS, Fy)

FOR STEELS WITH Fy 412 Mpa

- Direct Tension Or Flexure (Fdy): 1.2 Fy- Direct Compression : 2 Fa* but Fdy- Shear (Fdv) : 0.6 Fy

FOR STEELS WITH Fy> 412 Mpa

- Direct tension or flexure (Fdy) : 1.1 Fy- Direct compression : 1.8 Fa but Fdy- Shear : 0.55 Fy

* Fa is the allowable stress per part 1 of AISC specification.

TABLE - 2

DYNAMIC STRENGTH OF CONCRETE (Mpa)( RELATIVE TO 28 DAY STANDARD CYLINDER COMPRESSIVE STRENGTH, fC IN Mpa)

Axial or flexural compression (fdc) : 1.25 fcShear, direct (Vd) : 0.2 fc

Shear, diagonal tension (Vdc) : 0.189 cf'

Bond on deformed bars (Ud) : 0.15 fc

Direct tension (fdt) : 0.628 cf'

Bearing (fdc) : 0.85 fc

* In no case shall fc be less than 21 Mpa

6.3 LOAD

6.3.1 Dead Load

- The dead load is the vertical load due to the actual weight of all permanent structural andnon-structural components of building such as floors, roofs, walls, partitions and stairwaysand also the weight of fixed service equipment supported by structural elements.

- The specific gravity of materials shall be assumed accruing to commentary tables C1, C2ANSI/ASCE and ISIRI. 519 code where applicable.

- The following values shall be assumedDensity of soil 1850 kg/m

3(soil report value will override)

Density of reinforced concrete 2500 kg/m3

Density of structural steel 7850 kg/m3

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6.3.2 Live load

The following imposed live load shall be taken into account:

- Stairs, ramps, access platforms and walkways: uniformly distributed load of 250kg/m2

ora concentrated load of 450kgf whicheveris critical.

- Roof: uniformly distributed load of 175kgf/m2

or a concentrated load of 100kgf at anypoint whichever is critical.

- Switch gear room, control room and battery room: uniformly distributed load of 1000kgf/m2

or as recommended by vendor.

6.3.3 Blast load

- Explosion load are horizontal or vertical, uniformly distributed, static over pressuresequivalent in their design effect to dynamic over pressures created by explosions.

- Elements of building specified as blast proof building shall be designed to withstand thefollowing equivalent static over pressures.

a) Each external wall for an external over pressure of 10000 kg/m2

acting fromoutside of the building and separately, for an internal over pressure of 3350 kg/m

2

acting from inside of the building.

b) Roof slab and beams for external and internal over pressures from outside andinside of the building respectively, as follows.

Span (m) Over pressure (kg/m2)

External InternalUp to 3.00 5000 2500

4.00 4500 2250

5.00 4000 2000

6.00 3500 1750

7.00 3000 1500

8.00 and over 2500 1250

c) Main structural frames for the worst combination of the above over pressure asapplied to external walls and also of the roof tributary to that frame.

- Explosion over pressures shall not be assumed to act simultaneously with wind or earthquake forces.

- Average roof blast loading for main structure framing with span between the values listedmay be determined by linear interpolation.

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6.4 LOAD COMBINATIONS

Abbreviations used for load combinations are as follows:

D Dead Load

L Live Load

EBW1 External Blast Over Pressure from Outside on Wall 1



EBW4 External Blast Over Pressure from Outside on Wall4

IBW1 Internal Blast Over Pressure from Inside on the Wall 1




EBR External Blast Over Pressure from Outside on the Roof

IBR Internal Blast Over Pressure from Inside on the Roof

Load combinations for design of blast resistant structures are as follows:

D + EBW1 + EBR

D + EBW2 + EBR

D + EBW3 + EBR

D + EBW4 + EBR

D + IBW1 + IBR

D + IBW2 + IBR

D + IBW3 + IBR

D + IBW4 + IBR

D + EBW1 + EBR + L

D + EBW2 + EBR + L

D + EBW3 + EBR + L

D + EBW4 + EBR + L

D + IBW1 + IBR + L

D + IBW2 + IBR + L

D + IBW3 + IBR + L

D + IBW4 + IBR + L

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FINISHED

ROOF

WALL"1"

OPEN

ING

BLAST LOAD DISTRIBUTION FOR THE FIRST CASE

IN ADDITION TO ABOVE LOADING, EQUIVALENT LINEAR LOADS

DUE TO AREA OF EACH OPENING SHOULD BE CONSIDERED.

OPEN

ING

-Horizontal blast load does not act on underground parts of the walls.

-Applicable dead & live load , over pressure acting on one wall & roof

GROUND LEVEL

should be considered in each case.

6.5 STRUCTURAL DESIGN REQUIREMENTS

6.5.1 Design and construction of blast resistant buildings shall comply with the following generalrequirements.

6.5.2

a) Blast resisting components of buildings shall be reinforced concrete.

b) Lateral load carrying system shall be shear walls, rigid frames with ductile connections.

c) Beam or girder spans between supports shall not exceed 10m.

d) Materials of limited ductility, such as non-reinforced concrete, non-reinforced masonryconcrete blocks, bricks, stones, etc. are not permitted for blast resisting structural elements.When such materials are used for non-structural function in a blast-resistant building,

Consideration shall be given to their collateral damage due to the blast-induced motion ofthe building.

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6.5.3 Reinforced concrete structures shall satisfy the following additional requirements.a) Roof slabs and external walls shall be double reinforced the amount of reinforcement on

each face shall be between 0.25 percent and 2 percent of the effective cross-sectional area.Slabs and walls shall be a minimum of 125mm and 220mm in average thickness,respectively.

b) Frames and shear walls shall be designed in accordance with special provisions for seismicdesign, ACI318M chapter 21, except as modified herein.

c) The structure must be firmly embedded in the ground i.e. the vertical walls must extend toat least 1.5 meters below ground level with equal strength as walls above ground.

6.6 FOUNDATION DESIGN

6.6.1 foundation shall be designed for the maximum values of the dynamic reactions resulting fromthe following taken simultaneously in combination :

a) Over pressure acting on any one wall

b) Roof over pressure

c) Applicable dead and live loads

The blast surcharge around structure has a beneficial effect and can be conservatively ignored.

In no case shall the capacity of any foundation be less than the ultimate static capacity of thestructural system it supports or 1.2 times the transmitted loads, whichever is less.

6.6.2 Allowable dynamic soil bearing pressures shall be 0.8 times of the ultimate resistance value

(qa=0.8 qu).

6.6.3 The foundation shall be designed so that the safety factor against overturning due to theunbalanced lateral dynamic reactions is not less than 1.2

6.6.4 Passive resistance of the foundation, where required in addition to friction to resist sliding shallbe at least 1.5 times the unbalanced lateral load.

The unbalanced lateral load is defined as the total horizontal dynamic reaction force less thefrictional resistance.

6.6.5 For piled foundations the allowable vertical load under blast conditions shall be 0.8 times theultimate static capacity divided by 1.2, or 2.5 times the conventional allowable load, which overis less. The ultimate static capacity shall be based on the results of a soils investigation and pileload test.

6.6.6 Where piles are required to resist lateral movements of the structure, They shall be designed asfollows :

a) If only vertical piles are used, the combined ultimate lateral capacity of the piles and thepassive resistance on the foundation walls and footing shall be equal to or greater than 1.2times the full lateral resistance required.

b) Where batter piles are used, the allowable lateral resistance of the foundation shall betaken as 0.8 times the ultimate lateral load capacity of the batter piles plus 0.5 times thepassive resistance.

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