GP 04-30 20 December 2006

Guidance on Practice for Design and Location of Occupied Permanent

Buildings Subject to Blast, Fire, and Gas Hazards on Onshore Facilities

GP 04-30

BP GROUP ENGINEERING TECHNICAL PRACTICES

Document No. GP 04-30

Applicability Group

Date 20 December 2006

20 December 2006 GP 04-30 Guidance on Practice for Design and Location of Occupied Permanent Buildings Subject to Blast, Fire, and Gas Hazards on Onshore Facilities

Downloaded Date: 6/17/2008 10:04:08 PM The latest update of this document is located in the BP ETP and Projects Library

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Foreword

This is the first issue of Engineering Technical Practice (ETP) BP GP 04-30.

This Guidance on Practice (GP) addresses building design and location requirements to mitigate blast overpressure, thermal radiation, and toxic/flammable gas infiltration risks from sources external to the building. There are limitations to risk reduction that can be afforded by building design and location. Residual risk is managed by engineering controls, administrative controls, and emergency response procedures.

Copyright 2006, BP Group. All rights reserved. The information contained in this document is subject to the terms and conditions of the agreement or contract under which the document was supplied to the recipient’s organisation. None of the information contained in this document shall be disclosed outside the recipient’s own organisation without the prior written permission of BP Group unless the terms of such agreement or contract expressly allow.



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Table of Contents

Page

1. Scope .................................................................................................................................... 5

2. Normative references............................................................................................................. 5

3. Terms and definitions............................................................................................................. 6

4. Symbols and abbreviations .................................................................................................... 7

5. Building location and protective design features .................................................................... 7 5.1. General....................................................................................................................... 7 5.2. Concept selection ....................................................................................................... 8

6. Determination of potential harmful physical effects at proposed locations.............................. 8 6.1. Accident scenarios...................................................................................................... 8 6.2. Blast overpressure ...................................................................................................... 8 6.3. Thermal radiation........................................................................................................ 8 6.4. Flammable gas ........................................................................................................... 9 6.5. Toxic gas .................................................................................................................... 9

7. Blast overpressure................................................................................................................. 9

8. Thermal radiation................................................................................................................... 9 8.1. Protection of building occupants ................................................................................. 9 8.2. Shelter in place designation ........................................................................................ 9 8.3. Location .................................................................................................................... 11

9. Flammable gas infiltration .................................................................................................... 11 9.1. Protection of building occupants ............................................................................... 11 9.2. Shelter in place designation ...................................................................................... 11 9.3. Pressurisation and gas detection .............................................................................. 12

10. Toxic gas infiltration ............................................................................................................. 12 10.1. Protection of building occupants ............................................................................... 12 10.2. Shelter in place designation ...................................................................................... 12 10.3. Pressurisation and gas detection .............................................................................. 13

11. Control procedures and accountabilities .............................................................................. 13 11.1. Control procedures ................................................................................................... 13 11.2. Accountabilities......................................................................................................... 13

12. Emergency procedures........................................................................................................ 13

Annex A (Normative) Additional requirements for buildings subject to explosion overpressure greater than 70 mbar (1 psi)................................................................................................. 15

A.1. Design objectives................................................................................................................. 15

A.2. Design process .................................................................................................................... 15 A.2.1. Methodology ............................................................................................................. 15 A.2.2. Building specification ................................................................................................ 15 A.2.3. Detailing requirements for structures......................................................................... 16



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Bibliography .................................................................................................................................. 19

List of Tables

Table 1 - Blast overpressure design requirements ........................................................................ 10

Table 2 - Thermal radiation design requirements .......................................................................... 11

Table 3 - Flammable gas design requirements ............................................................................. 11

Table 4 - Toxic gas design requirements ...................................................................................... 12



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1. Scope

a. This GP defines requirements for design and location of occupied permanent buildings on onshore facilities (referred to as “buildings”) subject to blast, fire, and gas hazards.

For guidance on management of risk to occupants of existing buildings, refer to GN 04-006.

For guidance on design and location of occupied portable buildings, refer to RM GP 04-30.

Certain buildings or portions of buildings may be excluded because they are not occupied. See �3 for definition of occupied.

b. This GP provides guidance on design features required to protect occupants from potentially harmful physical effects (blast overpressure, thermal radiation, flammable gas infiltration, and toxic gas infiltration) that may arise from accidental events external to a building.

Protection of occupants from potentially harmful effects of accidental events arising within a building (releases from equipment containing toxic/flammable fluids, dust explosion, electrical fires, etc.) is not covered in this GP. Refer to GP 24-10.

Guidance on design for environmental events (extreme temperatures, wind, flooding, landslide/subsidence, seismic, tsunami, ice and snow loading, volcanic activity, etc.) is not covered in this GP. Refer to GP 04-20.

For guidance on other layout requirements, refer to GP 44-10.

c. This GP defines minimum requirements for inclusion in site emergency procedures and control procedures.

2. Normative references

The following normative documents contain a variety of potentially relevant good practices that, though referenced in this text, constitute requirements of this technical practice where applicable. For dated references, subsequent amendments to or revisions of any of these publications do not apply. However, parties to agreements based on this technical practice are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies.

BP GN 04-001 WBE Project No. A100-301 - Upgrades to Mitigate Hazards from Non-

Structural Components in Blast Loaded Buildings. Part 1 of 3 Interior Components.

GN 04-002 WBE Project No. A100-301 - Upgrades to Mitigate Hazards from Non-Structural Components in Blast Loaded Buildings. Part 2 of 3 Windows.

GN 04-003 WBE Project No. A100-301 - Upgrades to Mitigate Hazards from Non-Structural Components in Blast Loaded Buildings. Part 3 of 3 Doors.

GN 04-004 WBE Petrochemical Industry Recommended Practice on Design of Blast Resistant Buildings, April 1998.

GN 04-005 Commentary on WBE Petrochemical Industry Recommended Practice on Design of Blast Resistant Buildings, April 1998.

GP 04-10 Drainage Systems. GP 04-20 Civil Engineering. GP 14-02 Heating Ventilation and Air Conditioning Design Onshore.



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GP 24-03 Concept Selection for Inherently Safer Design. GP 48-50 Major Accident Risk Process. GP 04-20 Civil Engineering.

American Concrete Institute (ACI) ACI 318 Building Code Requirements for Reinforced Concrete.

British Standards Institute (BS) BS 8110 Structural Use of Concrete.

3. Terms and definitions

For the purposes of this GP, the following terms and definitions apply:

ERPG Emergency response planning guideline (ERPG) values are intended to provide estimates of concentration ranges where adverse effects might reasonably occur (as described in definitions for ERPG 1, ERPG 2, and ERPG 3) as consequence of exposure to a specific substance. Emergency response planning committee of the American Industrial Hygiene Association sets ERPG values.

ERPG 1 ERPG 1 is maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hr without experiencing other than mild transient adverse health effects or perceiving a clearly defined, objectionable odour.

ERPG 2 ERPG 2 is maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 hr without experiencing or developing irreversible or other serious health effects or symptoms that could impair individual ability to take protective action.

ERPG 3 ERPG 3 is maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 hr without experiencing or developing life threatening health effects.

Occupancy Measure of amount of time personnel spend in a location. This is normally expressed as number of personnel hours per unit calendar time (e.g., personnel hr/d).

Occupied Building shall be considered occupied if its primary purpose is to provide workspace or accomodation for personnel, irrespective of occupancy. Typical examples include office buildings, control rooms, laboratories, and gate houses.

If the primary purpose of a building is to house equipment (turbine enclosure, compressor shelters, motor control center [MCC] rooms, analyser shelters, instrument outstation, process equipment enclosures in regions of severe weather, etc.), it shall not be considered occupied, unless occupancy under normal operational conditions averages 2 man-hr or more in any 24 hr period.

If a building has distinct sub buildings with different primary purposes (e.g., an enclosed office within a store building or an instrument room/MCC connected to a control room), occupancy of each part of the building may be considered separately.



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Permanent building Building intended to remain in a single location for its design life.

This includes all forms of construction and includes modular buildings (e.g., portacabins and trailers) partially or completely fabricated offsite.

Portable building Building designed to be easily moved from location to location (e.g., trailers, portacabins, tents) that may be brought onto site or constructed for defined period of use prior to removal (e.g., for discrete events, such as turnarounds and projects).

4. Symbols and abbreviations

For the purpose of this GP, the following symbols and abbreviations apply:

BLEVE Boiling liquid expanding vapour explosion.

EA Engineering authority.

ERPG Emergency response planning guidance.

HVAC Heating, ventilating, and air conditioning.

IM Integrity management.

LFL Lower flammability limit.

LPG Liquid petroleum gas.

MCC Motor control center.

MOC Management of change.

SPA Single point accountability.

SPA IM Single point of accountability for integrity management

TA Technical authority.

5. Building location and protective design features

5.1. General

a. Civil engineering aspects of building design shall comply with GP 04-20.

b. Buildings subject to blast, fire, and gas hazards shall incorporate additional design features and emergency response requirements in accordance with �6 through �12.

c. If specific features are required to protect occupants from blast ingress, fire, and gas hazards, design of these features shall be performed by a competent designer.

d. Selection of specialist Vendors and design of these measures shall be subject to approval by engineering authority (EA) or delegated technical authority (TA).

e. Building heating, ventilating, and air conditioning (HVAC) system shall be designed in accordance with GP 14-02.



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5.2. Concept selection

a. Concept selection for a new building location and protective feature design shall comply with GP 24-03 and GP 48-50. For buildings within the E&P Segment, the principles of design safety in Major Project Common Process shall also apply.

b. The following factors shall be considered:

1. Options to eliminate need to house personnel close to hazardous facilities shall be identified, evaluated, and documented.

2. Range of potential locations for building shall be identified.

3. Potentially harmful physical effects shall be evaluated at each potential building location in accordance with �6.

4. Potential building locations shall be evaluated as follows:

a) Preference shall be given to locations where no specific design features (as defined in �7 through �10) are required to protect occupants from potentially harmful physical effects, even if these locations are outside site boundary.

b) If a concept is selected that requires specific design features to protect occupants from potentially harmful physical effects, concept shall be subject to approval by single point accountability for integrity management (SPA IM).

5. An emergency escape and evacuation plan shall be developed for building that takes into account potential harmful physical effects which could arise at selected location.

6. Determination of potential harmful physical effects at proposed locations

6.1. Accident scenarios

a. Accident scenarios and distances to potentially harmful physical effects shall be determined using methodology in GP 48-50, Annex A.

b. Consistent with GP 48-50, requests to use alternative methodology shall be referred to BP major hazards and fire team.

At a facility with multiple process units, proposed location may be affected by a large number of scenarios.

c. Potentially harmful physical effects from neighbouring locations shall be identified using readily available information.

d. Design basis for proposed locations shall be established as described in �6.2 through �6.5.

6.2. Blast overpressure

a. Range of blast overpressures and positive phase durations from accidental scenarios in �6.1 shall be determined.

b. Building design basis shall comply with �7 under all scenarios in �6.1.

6.3. Thermal radiation

a. Range of thermal flux and fire durations for events in �6.1 shall be determined.


c. Potential flammable liquid spill scenarios (e.g., bund overtopping) from process and storage facilities shall be considered.

d. If spill scenarios could affect a proposed location, catchment/drainage system shall be designed in accordance with GP 04-10 to route liquids away from building.



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e. Range of thermal flux and fire duration in catchment/drainage system shall be included in building design basis.

6.4. Flammable gas

a. Range of time durations for flammable gas exposure (taken as lower flammability limit [LFL] for continuous releases and 3.3 LFL for instantaneous releases) for events in �6.1 shall be determined.


6.5. Toxic gas

a. Range of toxic gas concentration and time durations for scenarios in �6.1 shall be determined.


7. Blast overpressure

Requirements for building design to protect occupants from blast overpressure are in Table 1.

8. Thermal radiation

8.1. Protection of building occupants

Requirements to protect building occupants from thermal radiation are in Table 2. Values in Table 2 are inclusive of all sources of thermal radiation.

8.2. Shelter in place designation

a. Decision to designate building “shelter in place” or provide escape route shall be determined for each scenario identified in �6 in conjunction with emergency response plan.

For a particular building, choice of “shelter in place” or evacuate may vary depending on event duration and level of thermal flux at building location. Shelter in place may be selected for short duration high radiation flux event. Evacuation may be selected for longer duration events with lower thermal flux.

Emergency response plans should not be based on personnel sheltering in place within buildings exposed to high level thermal radiation (i.e., greater than 6.3kW/m2 [2000 Btu/hr/ft2]) for long periods of time (e.g., greater than 1 hr). Long duration scenarios include blowouts on gas wells or free flowing oil wells and fires on pipeline reception facilities or storage areas.

b. For range of shelter in place scenarios:

1. Building envelope shall retain its integrity and environment within building shall remain habitable.

2. External equipment (HVAC equipment, standby generators, air supply, etc.) shall remain operable and efficient under design fire scenarios.

c. Buildings shall not be designated as “shelter in place” within boiling liquid expanding vapour explosion (BLEVE) fireball radius for scenarios that could escalate to BLEVE, unless building is specifically designed to protect occupants from BLEVE effects.

Scenarios that could escalate to BLEVE include fires on or close to liquid petroleum gas (LPG) storage facilities.



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Table 1 - Blast overpressure design requirements

Overpressure range mbar psig

Blast overpressure design requirements

0 to 30 0 to 0.4 No specific blast resisting requirements. 30 to 42 0.4 to 0.6 No restriction on structural type.

Glazing shall be specified to reduce injuries in blast (i.e., toughened glass, laminated glass, or polycarbonate). Float glass shall be coated with antishatter film. No brittle cladding materials (e.g., transite).

42 to 70 0.6 to 1.0 Framed structure in reinforced concrete or structural steelwork. Joints shall be designed to ensure ductile behaviour. Walls and roofs shall be ductile material, such as reinforced concrete or steel. Internal non-structural features shall be restrained (refer to GN 04-001). Windows shall comply with “low hazard” performance standard (refer to GN 04-002) for blast loading at building location. Windows facing overpressure sources shall comply with “low hazard” performance standard under reflected overpressure. Doors shall comply with “moderate damage” performance standard (refer to GN 04-003) Doors facing overpressure sources shall comply with “moderate damage performance standard” under reflected overpressure.

> 70 (1) > 1.0 (1) Building structure shall be designed to resist maximum blast loading at proposed location (refer to GN 04-004 and GN 04-005). Walls facing potential blast source(s) shall be designed to resist reflected overpressure (2). The suction phase of the blast shall be taken as 0.3 times the free field positive phase blast loading on each element. Walls facing sources of explosion shall be designed for 0.3 times the reflected overpressure. The duration of the negative phase shall be taken to be the same as the positive phase. The effects of rebound shall also be considered. Roof mounted equipment shall comply with Annex A, A.2.3.4. Internal non-structural features shall be restrained (refer to GN 04-001). Windows shall comply with “low hazard” performance standard (refer to GN 04-002). Windows facing potential blast sources shall comply with “low hazard” performance standard under reflected overpressure. Doors shall comply with “moderate damage” performance standard (refer to GN 04-003). Doors facing potential blast source(s) shall comply with “moderate damage performance standard” under reflected overpressure. Buildings required to protect against toxic vapours and/or smoke post blast shall have glazing that complies with “no break” performance standard (refer to GN 04-002). Seals in doors and windows shall be designed to maintain sufficiently accurate alignment to maintain the vapour barrier. Glazing and doors that face potential blast source(s) shall meet these criteria under reflected overpressure.

Notes: 1. Further guidance on design of buildings subject to blast overpressure of greater than 70 mbar (1 psig) may be found in Annex A. 2. Reflected overpressure may be calculated using the formula: Pr = 2Po × (7Pa + 4Po) / (7Pa + Po) Where: Pr = Reflected overpressure. Po = Peak incident overpressure (free field overpressure). Pa = Atmospheric pressure.



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Table 2 - Thermal radiation design requirements

Thermal radiation range kW/m2 Btu/hr/ft2

Thermal radiation design requirements

< 1,6 < 500 No specific fire resisting requirements. 1,6 to 6,3 500 to 2000 Building shall be designed as shelter in place for duration of events.

or Escape route shall be provided to alternative shelter in place facility or location with thermal flux radiation of 1,6 kW/m2 (500 Btu/hr/ft2) or less.

> 6,3 > 2000 Building shall be designed as shelter in place for duration of events. or Either of the following shall be provided: a. Protected escape route to alternative shelter in place facility or location with thermal flux radiation of 1,6 kW/m2 (500 Btu/hr/ft2) or less. b. Personnel protective equipment designed to allow safe escape.

8.3. Location

Buildings shall not be located in areas where a release of flammable liquid could engulf the building.

9. Flammable gas infiltration


Requirements to protect building occupants against flammable gas infiltration are in Table 3.

Table 3 - Flammable gas design requirements

Flammable gas range Flammable gas design requirements Outside LFL for continuous releases and outside 3.3 LFL for instantaneous releases.

No specific measures to resist flammable gas infiltration required.

Within LFL for continuous releases and/or within 3.3 LFL for instantaneous releases.

Building shall be designed as shelter in place facility for duration of events. or Warning system shall be provided and escape route shall be provided to alternative shelter in place facility or location outside flammable range. Skirts that prevent build up of gas concentrations underneath building shall be provided. Means of detecting wind direction at exit doors shall be provided (e.g., direct view of windsock).


a. Decision to designate building “shelter in place” or provide escape route shall be determined for each scenario identified in �6 in conjunction with emergency response plan.

For a particular building, choice of “shelter in place” or evacuate may vary depending on duration of event and predicted time for a flammable cloud to reach the building.

Emergency response plans should not be based on personnel “sheltering in place” within buildings engulfed in flammable clouds if design scenario has long duration (e.g., greater than 1 hr). Long duration scenarios include blowouts on gas wells or free flowing oil wells and fires on pipeline reception facilities or storage areas.




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1. Building envelope shall retain its integrity against gas infiltration (i.e., maintain positive pressurisation) and environment within building shall remain habitable.

2. External equipment required to maintain building environment (HVAC equipment, standby generators, air supply, etc.), shall be suitable for operation in a flammable atmosphere.

Refer to CIA RC21/03, Appendix 4, for guidance on air supply requirements, volume of space required per person for various shelter in place durations, and detailing to minimise gas ingress.

9.3. Pressurisation and gas detection

Building pressurisation and gas detection systems shall be subjected to testing and maintenance program to ensure that they are effective in mitigating gas infiltration.

Operation procedures are also required (for example, to normally keep doors shut to maintain pressurisation within building).

10. Toxic gas infiltration


Requirements to protect building occupants against toxic gas infiltration are in Table 4.

Table 4 - Toxic gas design requirements

Toxic gas range Toxic gas protection requirements Outside ERPG 2 No specific measures to resist toxic gas infiltration required. Within ERPG 2 Building shall be designed as shelter in place facility for duration of event.

or All of the following shall be provided: Warning system. Escape equipment. Escape route to location outside EPRG 1 or to alternative shelter in place facility. Means of detecting wind direction at exit doors (e.g., direct view of windsock).


a. Decision to designate building shelter in place or provide escape route shall be determined for each scenario identified in �6 in conjunction with emergency response plan.

For a particular building, choice of shelter in place or evacuate may vary depending on duration of event and predicted time for toxic cloud to reach the building.

Emergency response plans should not be based on personnel “sheltering in place” within buildings engulfed in toxic clouds with concentration greater than ERPG 2 if design scenario has long duration (e.g., greater than 1 hr). Long duration scenarios include blowouts on gas wells or free flowing oil wells and fires on pipeline reception facilities or storage areas.


1. Building envelope shall retain its integrity against gas infiltration (i.e., maintain positive pressurisation), and the environment within building shall remain habitable. Note that toxic cloud may also be flammable.

2. External equipment required to maintain building environment (HVAC equipment, standby generators, air supply, etc.), shall be suitable for operation in toxic/flammable atmosphere.



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Refer to CIA RC21/03, Appendix 4, for guidance on air supply requirements, volume of space required per person for various shelter in place durations, and detailing to minimise gas ingress.

10.3. Pressurisation and gas detection

Building pressurisation and gas detection systems shall be subjected to testing and maintenance program to demonstrate that they are effective in mitigating gas infiltration.

Operation procedures are also required (for example, to normally keep doors shut to maintain pressurisation within building).

11. Control procedures and accountabilities

11.1. Control procedures

Sites shall develop and maintain procedures for control of occupied buildings. Procedures shall include:

a. Reference to applicable legislation and this GP.

b. Procedures to identify SPA and associated accountabilities.

c. Requirement that siting of a new building or changes to an existing building or changes to hazards affecting an existing building are subject to management of change (MOC) approval process.

11.2. Accountabilities

a. SPA IM shall be accountable for:

1. Confirming that proposed new buildings are appropriately designed and located to protect occupants from blast overpressure, thermal radiation, flammable gas infiltration, and toxic gas infiltration hazards.

2. Maintaining documentation and permits, including retention of all relevant documentation that approved location, design, and occupancy of buildings.

3. Confirming that maintenance and testing program is in place for any systems required to protect building occupants.

b. SPA for each building shall be responsible for maintaining ongoing process to promote safety of occupants, including training and practice for occupants on building operational requirements (e.g., confirming that doors required to maintain building pressurisation are kept closed) and emergency procedures.

c. EA or delegated TA shall be accountable for:

1. Development of building design concept, including location selection.

2. Specification of requirements for design features required to protect building occupants.

3. Selection of specialist Vendor involved in design of features required to protect building occupants.

12. Emergency procedures

a. Buildings subject to fire, blast, and gas hazards shall be included in site emergency response plan.

b. Emergency response procedures for potential accident scenarios identified in �6 shall be in place for buildings.



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c. Procedures shall be communicated to occupants via signage and briefings.

d. The following shall be considered in developing emergency procedures:

1. Raising alarm.

2. Distinguishing between when to evacuate and when to remain in occupied building (shelter in place).

3. Means of escape routes.

4. Potential provision of escape equipment. Personnel shall be trained in use of escape equipment.

5. Location of evacuation safe locations, whether shelter in place/toxic refuge buildings or outside evacuation/muster points.



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Annex A (Normative)

Additional requirements for buildings subject to explosion overpressure greater than 70 mbar (1 psi)

A.1. Design objectives

a. Before proceeding with this Annex, recommendations of �5 on location of buildings shall be implemented.

b. Buildings that are located in an area subject to explosion overpressure greater than 70 mbar (1 psi) shall comply with this Annex.

c. Buildings located in areas subject to explosion overpressure shall be designed to prevent harm to people. The following parts of the building shall particularly be considered:

1. Foundations.

2. Structure.

3. Architecture.

4. Services.

5. HVAC.

d. Scope of this annex is limited to foundations and structure.

e. Buildings may suffer nonstructural damage or structural damage, provided that this does not result in collapse, harm to personnel, or render control equipment inoperable.

A.2. Design process

A.2.1. Methodology

a. Structural design for buildings subjected to blast loading in excess of 70 mbar (1 psi) shall be performed in accordance with GN 04-004.

b. Alternative design methodologies may be used, subject to EA approval with support from appropriate TA.

c. Design of structural elements and foundations shall comply with relevant requirements of GP 04-20 and additional requirements in this Annex.

GN 04-004 refers to specific U.S. codes. For other project locations, alternative structural design codes may also be followed as described in GP 04-20.

Preference should be given to single story structures as these tend to be more economical to design to resist blast loading.

A.2.2. Building specification

a. Blast design requirements data sheet (such as data sheet included in GN 04-004) shall be prepared for each building subject to explosion.

b. Blast data sheet defines pressure and duration of explosion to be designed for, based on the following:

1. Location and source of explosion.

2. Location and use of building.



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c. From data in a. and b., the following parameters shall be selected to match required protection level for occupants and equipment (refer to GN 04-005 for guidance):

1. Building performance requirement (low, medium, or high).

2. Performance category for blast doors (I through IV).

d. Rationale behind selection of performance requirements shall be subject to EA approval with support from appropriate TA before design commences.

A.2.3. Detailing requirements for structures

A.2.3.1. Concrete structures

a. Prestressed concrete shall not be used, unless justification is presented to and approved by appropriate EA.

Prestressing strands have limited ductility and may result in catastrophic collapse under application of blast loads at ultimate strength. In addition, prestressed components are typically designed for load application in a single direction and do not have adequate rebound resistance.

b. Reinforced concrete members principally resisting bending shall be reinforced such that area of main tension reinforcement expressed as percentage of gross cross sectional area is not less than 0.45%.

c. Member shall be equally reinforced on both internal and external face.

d. Concrete cube strength shall be at least 30 MPa (4400 psi) or comply with national codes, whichever is higher.

e. Reinforcing spices

1. Reinforcing bars should be as long as practical to reduce numbers of splices.

2. Splices shall be staggered, if possible, and located away from highly stressed areas.

3. Lap lengths shall be at least 70 x bar diameter.

f. During construction, each distinct concrete element shall be constructed using single pour without construction joints.

g. Construction joints may be used in the following instances:

1. Between distinct elements (e.g., slab to wall, wall to roof, beam to column).

2. If construction site constraints (e.g., batch plant capacity) would produce a lower quality structure if single pour method is followed.

h. Construction joints, if used, shall be prepared in accordance with BS 8110 or ACI 318.

i. Contraction/expansion joints shall be permitted only if it can be demonstrated that structural blast resistance is maintained.

A.2.3.1. Foundations

a. Building displacement under dynamic loading shall be calculated. Acceptability criterion shall be developed depending on sensitivity of building to displacement.

b. Acceptability criteria shall be communicated to designer of services and designer of HVAC.

A.2.3.2. External doors and windows

a. External doors shall comply with GN 04-003.

b. Doors in external blast resistant walls shall:



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1. Be kept to minimum consistent with escape requirements.

2. Open outwards and butt on all four edges against steel frames fixed to concrete.

3. Have design and detailing of door and frame that shall take account of dynamic rebound.

4. Be designed with closing and locking mechanisms to operate easily under normal conditions.

c. Power assistance may be used for opening and closing blast resistant external doors.

d. Window specifications

1. Windows shall be specified to protect occupants under design blast loading.

2. Windows facing sources of blast shall be specified to resist reflected overpressure.

3. Guidance on glazing performance under blast loading is in GN 04-002.

e. Window performance criteria

1. Window performance criteria shall be selected based on emergency response plan.

2. For buildings that are not required to remain operable or act as shelter in place post blast events, “low hazard” performance criterion may be adopted.

3. If building is intended to remain operable or act as shelter in place facility post blast, “no break” performance criteria should be adopted.

A.2.3.3. Other openings

a. Openings (e.g., for ventilating systems) should be designed by location, provision of attenuators, or other means to prevent entry of debris into personnel or equipment areas.

b. Blast valves

1. Entry of blast overpressure surges through openings may be limited by means of blast valves or by attenuation through plenums.

2. Need for blast valves shall be determined based on blast overpressure and nature of building.

3. In general, blast valves should be fitted to buildings that are designed to resist overpressures of 300 mbar (4.3 psi) or greater.

4. There are a variety of blast valves available for different duties (e.g., wall or roof entry, time of closure, and leakage rate). Performance and testing specification should be developed to confirm that appropriate type of valve is selected.

A.2.3.4. Roof, wall, and ceiling mounted equipment

a. Equipment, if sited on the roof, shall have performance under blast loading considered in structural analysis to mitigate potential effects on integrity of building structure.

b. Fastening arrangement and equipment itself shall be checked to confirm that it is robust under blast loading in order to reduce potential missile hazard to personnel.

c. Nonstructural equipment

1. Distortion/movement of external walls/roof may occur during blast events that could cause direct damage to equipment and/or cause equipment to break free from mountings and injure occupants.

2. Items, such as cabinets containing electrical/control equipment or storage racks containing fragile, heavy, or hazardous materials, shall be floor mounted and have separation distance from the wall greater than maximum predicted deflection from structural calculations.



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3. Guidance on details to restrain nonstructural building components (lights, HVAC ductwork, etc.) is in GN 04-002.

A.2.3.5. Internal partitions and finishes

a. Internal partitions shall be designed and installed to allow for possible movement of main structure during explosion.

b. If alternative materials are available, failure mechanisms shall be considered. Material least likely to cause injury in event of failure shall be selected.

c. Internal finishes, particularly to interior face of external walls, shall be selected and installed to avoid injury to personnel and damage to equipment in building in event of external explosion.

A.2.3.6. External features

a. External features, such as canopies, should not be incorporated in building exposed to blast hazard unless safety based justification for use is presented to EA.

b. Such external features, if provided, shall be designed to resist design blast loading.

c. Metal cladding panels, if used, shall be supported by building frame with fixing system capable of resisting design blast.

A.2.3.7. Service connections

Connections of building services shall be designed flexibly to avoid damage during displacement under design blast load.



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Bibliography

BP [1] GN 04-006, Management of Risk to Occupants of Existing Permanent Buildings.

[2] GP 24-10, Fire Protection Onshore.

[3] GP 44-10, Plant Layout.

[4] RM GP 04-30, Design and Location of Occupied Portable buildings within Refineries and Chemical Plants.

Chemical Industries Association (CIA) [5] RC21/03, Guidance for the location and design of occupied buildings on chemical manufacturing

sites, 2003, www.cia.org.uk, ISBN 1 85897 114 4.

GP 04-30 20 December 2006

Documents

bp etp

practice gp addresses

onshore facilities gp

location requirements

gas hazards

blast overpressure

protective design features

applicability group