Seismic Restraint of Engineering Services. AIRAH July 2014

Transcription

1 Seismic Restraint of Engineering Services AIRAH July 2014

2 Engineering Services This presentation will cover: The Earthquake Hazard South Australia s Earthquake Hazard Engineering services damage Earthquake code background New DPTI Guidenote Design of Seismic Restraints Seismic Restraint examples Christchurch, Sept 2010

3 The Earthquake Hazard

4 Earthquakes The earth s outer shell is about kilometres thick and is broken up into nine major and several smaller plates. These plates are constantly moving away from, towards and past each other. As continents are part of these plates they also move. Subduction

5 Earthquakes Most earthquakes occur at plate boundaries where the plates meet and are forced against each other. Sometimes the movement in plates is gradual, at other times the plates are locked together, unable to release the accumulating energy as they bend or stretch. When forces grow large enough the plates break free suddenly causing the ground to shake.

6 Earthquakes

7 Earthquakes

8 Earthquakes Australia is situated within the Indian- Australian plate. The Indian-Australian plate is being pushed north at 7cm/year and is being squeezed between other plates. The stress from the squeezing builds up as compression within the Australian continent leading to earthquakes. Much less is known and understood about earthquakes occurring within plates rather than the more common plate boundary earthquakes.

9 Earthquakes Earthquakes occur without warning. Earthquakes occur over very short time frames, usually less than one minute, A series of smaller earthquakes or aftershocks will often occur following the main earthquake, Entire cities can be affected to some degree by even a moderate earthquake. Christchurch NZ 2010

10 South Australia s Earthquake Hazard Adelaide Newspaper Headline following 1954 Darlington Earthquake

11 Earthquake Hazard By world standards Australia s earthquake hazard is low to moderate, this does not mean however that our earthquake related risks are low.

12 Redbanks Fault M4.4 Gawler 1856 M4.1 Gumeracha 1866 M3.9 Adelaide 1914 Para Fault M3.1 Adelaide 1977 M2.7 Gawler 1982 M2.3 Modbury 1966 Geoscience Australia - all located earthquakes up to 2011.

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14 Earthquake Hazard Seismologists advise earthquakes up to M7.5 can occur in Australia. Australia has been subject to 17 earthquakes registering 6 or more on the Richter scale in the last 80 years. Adelaide has suffered damage from earthquakes on three occasions.

15 Earthquakes In Australia there are no major faults that stand out as having regular earthquakes.

16 Engineering services damage in earthquakes

17 Engineering services damage Northridge USA 1994 Failed Chiller Mounts

18 Engineering services damage Chile Failed Pump Plinth

19 Engineering services damage Northridge USA 1994 Failed Compressor Mounts

20 Engineering services damage Failed A/C Mounts

21 Engineering services damage Failed A/C Mounts

22 Engineering services damage Northridge USA 1994 Failed Tank Mounts

23 Engineering services damage Hot water system failures

24 Engineering services damage San Fernando M Pipe failure Chile 2010 Pipe failure

25 Engineering services damage Northridge USA 1994 Northridge USA 1994

26 Engineering services damage Northridge USA 1994 Failed lighting mounts

27 Engineering services damage Chile 2010 Boiler and pipe failure Northridge USA 1994 Failed air diffusers

28 Engineering services damage Mexico M Izmit, Turkey M

29 Engineering services damage PortauPrince, Haiti M

30 Engineering services damage Chile 2010, Concepcion Airport, metal ceiling panel strong enough to fail the sprinkler head

31 Engineering services damage

32 Engineering services damage Chile 2010, Santiago Airport Terminal, suspended HVAC equipment failure

33 Engineering services damage

34 Engineering services damage

35 Engineering services damage 2010 Haiti Earthquake

36 Engineering services damage

37 Engineering services damage Ducts and equipment shifted in earthquake

38 Engineering services damage Plinth broken up by earthquake, unreinforced and unconnected to floor slab

39 Engineering services damage Earthquake damage to communication and computer racks

40 Engineering services damage Movement of unbraced risers damaged ceiling and insulation M6.7 Northridge Earthquake FEMA E

41 Engineering services damage Wall damage at fire pipe penetration Peru Earthquake - FEMA E

42 Engineering services damage

43 Engineering services damage Chile 2010 Ceiling, lights and air diffuser failure

44 Engineering services damage Peru 2001 Control room ceiling, lights and air diffuser failure

45 Engineering services damage Christchurch M

46 Engineering services damage Northridge USA 1994 Northridge USA 1994

47 Other non-structural damage Christchurch M

48 Other non-structural damage Christchurch M

49 Earthquake code background

50 Earthquake Codes The first Earthquake Code AS2121 was published in 1979 and referenced in the South Australian Building Regulations in A Section on Minimum Earthquake Forces for Parts of Buildings was included. It required the design of fixings for tanks, storage racks, equipment or machinery to resist earthquake loads. The standard was a life-protection code equipment required for life safety systems or for continued operation of essential facilities must be able to withstand the design earthquake event.

51 Earthquake Codes AS : Earthquake loads was published in 1993 and referenced in the BCA in 1995 taking over from AS2121. It contained a section Requirements for Non- Structural Components The categories of architectural, mechanical and electrical components were specifically mentioned and detailed design criteria was provided with a requirement that components be attached so that earthquake forces are transferred to the structure.

52 Earthquake Codes In 2007 the code was revised and reissued as Earthquake Actions in Australia. This is the current code, effective 1 May Section 8 covers Design for Parts and Components. Where required by Section 8 architectural, mechanical, electrical and other similar components shall have their fastenings designed to resist earthquake forces.

53 New DPTI Guidenote Seismic Restraint of Engineering Services

54 Why a DPTI Guidenote? To assist and promote compliance with AS Section 8 as: It forms part of the National Construction Code. Our clients are increasingly aware of a gap in compliance. The Earthquake Code is a loading code, it provides information on calculating loads but provides no examples of how to comply.

55 Why a DPTI Guidenote? Engineering services make up a significant proportion of the cost of constructing a building. In some cases equipment within a building can be significantly more valuable than the building itself. The cost of repairing services after an earthquake can be significant. In future should a major earthquake occur there will be less persons injured by falling services, less obstructions to evacuation and less interruption to the use of buildings immediately afterwards. Christchurch 2011

56 What is in the DPTI Guidenote? Background to the earthquake hazard in South Australia Design responsibility recommendations A design methodology using AS Section 8 including: Advice on service clearances Advice on spacing of bracing Example calculation Force diagrams Safety wire requirements for components in T-bar ceiling systems Two drawing sheets with restraint examples

57 Design of Seismic Restraint of Engineering Services

58 Seismic Restraint Design 1 Establish the Building s Importance Level (1 4) as per NCC Importance Level Building Type 1 Buildings presenting a low degree of hazard to life and other property in the case of failure. 2 Buildings not included in IL 1, 3 and 4. Example building types Farm buildings Minor temporary facilities Low rise residential construction. Buildings and facilities below the limits set for IL3. Earthquake probability 1 in 250 years (kp = 0.75) 1 in 500 years (kp = 1.0)

59 Importance Level Building Type Example building types Earthquake probability 3 Buildings designed to contain a large number of people 4 Buildings essential to post disaster recovery or associated with hazardous facilities. Building where >300 people can congregate in one area. School facility for >250 students College or university for >500 students Health care for > 50 beds Jails and detention facilities Any occupancy of >5000 Buildings having post disaster functions. Designated emergency shelters. Buildings and facilities containing hazardous materials capable of causing hazardous conditions beyond the property boundary 1 in 1000 years (kp = 1.3) 1 in 1500 years (kp = 1.5)

60 Seismic Restraint Design to AS Description AS Section 8 Applies? Earthquake Force calculation Domestic dwellings with h < 8.5m No Feq = 0 Domestic dwellings with h > 8.5m (Class 1a or 1b) Yes Treat as for Importance Level 2 Importance Level 1 buildings No Feq = 0 Importance Level 2 and 3 buildings with h < 15m Importance Level 2 and 3 buildings with h > 15m Yes Yes Feq = 0.1 x Wc for non brittle parts and components Part of AS or as for h > 15m with some exceptions for ducting and piping. Feq = [kpzch(0)] ax [Icac/Rc] Wc but > 0.05 Wc With some exceptions for ducting and piping.

61 The Exceptions, IL2 & 3 Duct and piping distribution systems do not need to be braced where they are: Gas piping less than 25mm inside diameter Piping in boiler and mechanical rooms less than 32mm inside diameter Other piping less than 64mm inside diameter Electrical conduit less than 64mm diameter Rectangular air handling ducts less than 0.4m 2 in cross section Round air-handling ducts less than 0.7m diameter Ducts and piping suspended by individual hangers 300mm or less in length from the top of the pipe to the bottom of the support for the hanger.

62 Not excepted from compliance, IL 2&3 Mechanical, electrical and similar components to the following always need to be braced/fixed to resist seismic loads: Smoke control systems, emergency electrical systems Fire and smoke detection systems Fire suppression systems including sprinklers Life safety system components Boilers, furnaces, water heaters, flues, pressure vessels Communication systems Reciprocating or rotating equipment, machinery (manufacturing) Utility and service interfaces, lift machinery, escalators Lighting fixtures, electrical panel boards, conveyor systems.

63 Seismic Restraint Design 2 Review the engineering services design to determine which services do and do not need seismic restraint. 3 Ensure that services are designed to have appropriate clearance between them, whether braced or not, to reduce the chance of damage in an earthquake. Recommended clearances are:

64 Seismic Restraint Design Earthquake damage to a cable tray

65 Seismic Restraint Design 4 Determine the location of bracing The recommended maximum spacing of seismic bracing for piping, conduit and ductwork is as follows: 9m for transverse bracing of ductile materials; 18m for longitudinal bracing of ductile materials;

66 Seismic Restraint Design 4 Determine the location of bracing The spacing of bracing may need to be reduced, for example: Brace both sides of piping, conduit or ductwork at flexible connections; Brace to avoid collisions between piping, conduit or ductwork and adjacent other non-structural components; Brace within 600mm of changes in direction, whether it be horizontal or vertical changes (note that offsets of less than 600mm along a run are not considered a change of direction); Brace where components penetrate floors or ceilings; Brace in both directions at the top of all risers where risers exceed 900mm.

67 Seismic Restraint Design The spacing and type of bracing along a run of piping, conduit or ductwork should not vary greatly in order to ensure uniform deflection and loading. Each unit of equipment connected to a run of piping, conduit or ductwork shall be individually and independently braced. Where the equipment is rigidly connected to the piping, conduit or ductwork it shall be designed for the tributary seismic forces. Suspended rectangular equipment shall be provided with a minimum of one sway brace per corner. Thermal expansion and contraction forces, where present, must be considered in the layout of transverse and longitudinal braces. Flexibility should be provided where pipes pass through seismic or expansion joints.

68 Seismic Restraint Design 5 Determine the design forces for the component or length of pipe or duct between brace locations. Description Importance Level 2 and 3 buildings with h < 15m Earthquake Force calculation Feq = 0.1 x Wcomp Importance Level 2 and 3 buildings with h > 15m Feq = [kp Z Ch(0)] ax [Ic ac / Rc] Wcomp but > 0.05 Wcomp (Simple Method, Section 8.3 of AS1170.4)

69 AS Simple Method IL2 & 3 and h > 15m - For the component or length of duct/pipe being considered calculate: Feq = [kp Z Ch(0)] ax [Icac/Rc] Wcomp Importance level of building (kp) Acceleration coefficient based in site location (Z) Factor for component based on Site sub-soil class (Ch(0)) Its fixing height within the structure (ax) Is it critical to life safety (Ic) can be the case even if not IL4 building Is the component fixed on a flexible spring type mounting system? (ac) Is it a rigid component with brittle materials or connections? (Rc) Its weight (Wcomp )

70 Importance Level Building Type Example building types Earthquake probability 3 Buildings designed to contain a large number of people 4 Buildings essential to post disaster recovery or associated with hazardous facilities. Building where >300 people can congregate in one area. School facility for >250 students College or university for >500 students Health care for > 50 beds Jails and detention facilities Any occupancy of >5000 Buildings having post disaster functions. Designated emergency shelters. Buildings and facilities containing hazardous materials capable of causing hazardous conditions beyond the property boundary 1 in 1000 years (kp = 1.3) 1 in 1500 years (kp = 1.5)

71 AS Simple Method IL2 & 3 and h > 15m - For the component being considered calculate: Feq = [kp Z Ch(0)] ax [Icac/Rc] Wcomp Importance level of building (kp) Acceleration coefficient based on site location (Z) Factor for component based on Site sub-soil class (Ch(0)) Its fixing height within the structure (ax) Is it critical to life safety (Ic) can be the case even if not IL4 building Is the component fixed on a flexible spring type mounting system? (ac) Is it a rigid component with brittle materials or connections? (Rc) Its weight (Wcomp ) Check that this is greater than 5% of the weight of the unit, if less adopt 5%.

72 AS Simple Method Z = Acceleration coefficient with a 10% probability of exceedance in 50 years. Location Z Port Augusta 0.11 Adelaide, Port Pirie, Robe, Mt Gambier 0.10 Whyalla 0.09 Renmark 0.05 Ceduna 0.03

73 AS Simple Method IL2 / 3 and h > 15m - For the component being considered calculate: Feq = [kp Z Ch(0)] ax [Icac/Rc] Wcomp Importance level of building (kp) Acceleration coefficient based in site location (Z) Factor for component based on Site sub-soil class (Ch(0)) Its fixing height within the structure (ax) Is it critical to life safety (Ic) can be the case even if not IL4 building Is the component fixed on a flexible spring type mounting system? (ac) Is it a rigid component with brittle materials or connections? (Rc) Its weight (Wcomp ) Check that this is greater than 5% of the weight of the unit, if less adopt 5%.

74 AS Simple Method Identify the soil at the site (Geotechnical Engineering advice) Site sub-soil class Description Ch(0) Class A Strong rock 0.8 Class B Rock 1.0 Class C Shallow soil 1.3 Class D Deep soil 1.1 Class E Very soft soil 1.1

75 AS Simple Method IL2 / 3 and h > 15m - Calculate: Feq = [kp Z Ch(0)] ax [Icac/Rc] Wcomp Importance level of building (kp) Acceleration coefficient based in site location (Z) Factor for component based on Site sub-soil class (Ch(0)) Its fixing height within the structure (ax) Is it critical to life safety (Ic) can be the case even if not IL4 building Is the component fixed on a flexible spring type mounting system? (ac) Is it a rigid component with brittle materials or connections? (Rc) Its weight (Wcomp ) Check that this is greater than 5% of the weight of the unit, if less adopt 5%.

76 AS Simple Method IL2 / 3 and h>15m - For the component being considered calculate: Feq = [kp Z Ch(0)] ax [Icac/Rc] Wcomp Importance level of building (kp) Acceleration coefficient based in site location (Z) Factor for component based on Site sub-soil class (Ch(0)) Its fixing height within the structure (ax) Importance factor, is it critical to life safety (Ic) even if not IL4 building Is the component fixed on a flexible spring type mounting system? (ac) Is it a rigid component with brittle materials or connections? (Rc) Its weight (Wcomp ) Check that this is greater than 5% of the weight of the unit, if less adopt 5%.

77 AS Simple Method Importance Factor

78 AS Simple Method IL2 / 3 and h > 15m - For the component being considered calculate: Feq = [kp Z Ch(0)] ax [Icac/Rc] Wcomp Importance level of building (kp) Acceleration coefficient based in site location (Z) Factor for component based on Site sub-soil class (Ch(0)) Its fixing height within the structure (ax) Is it critical to life safety (Ic) can be the case even if not IL4 building Is the component fixed on a flexible spring type mounting system? (ac) Is it a rigid component with brittle materials or connections? (Rc) Its weight (Wcomp ) Check that this is greater than 5% of the weight of the unit, if less adopt 5%.

79 AS Simple Method Component amplification factor

80 AS Simple Method IL2 / 3 and h>15m - For the component being considered calculate: Feq = [kp Z Ch(0)] ax [Icac/Rc] Wcomp Importance level of building (kp) Acceleration coefficient based in site location (Z) Factor for component based on Site sub-soil class (Ch(0)) Its fixing height within the structure (ax) Is it critical to life safety (Ic) can be the case even if not IL4 building Is the component fixed on a flexible spring type mounting system? (ac) Is it a rigid component with brittle materials or connections? (Rc) Its weight (Wcomp ) Check that this is greater than 5% of the weight of the unit, if less adopt 5%.

81 AS Simple Method Component ductility factor

82 AS Simple Method IL2 / 3 and h>15m - For the component being considered calculate: Feq = [kp Z Ch(0)] ax [Icac/Rc] Wcomp Importance level of building (kp) Acceleration coefficient based in site location (Z) Factor for component based on Site sub-soil class (Ch(0)) Its fixing height within the structure (ax) Is it critical to life safety (Ic) can be the case even if not IL4 building Is the component fixed on a flexible spring type mounting system? (ac) Is it a rigid component with brittle materials or connections? (Rc) Its weight (Wcomp ) Check that Feq > 5% of the weight of the unit, if less adopt 5%.

83 Apply seismic forces and design bracing elements

84 AS Simple Method 6 - Design the seismic bracing elements This includes the bracing members, fixings, fasteners and anchors. Check also the structural adequacy of the supporting structure to carry the services and service induced seismic loads.

85 Design considerations Type of bracing Type of anchors Compression in suspension rods Interaction with ceilings Transmission of vibration to structure Thermal movements Services crossing structural separations. Service plinth reinforcement and dowels to structural slab.

86 Type of bracing Wire cable tension only so required both sides, cable must be strength rated. Steel angle compression and tension, check length for buckling, consider vibration transmission. Unistrut - compression and tension, check length for buckling, consider vibration transmission. Threaded rod limited compression strength.

87 Anchors Some fixing types are vulnerable to the dynamic nature of seismic forces such that they might shift, slip or jump out of place. Use only anchors rated for seismic loads by their manufacturer.

88 Compression in suspension rods Where horizontal forces are large enough the typical tension force in hanger rods can change to compression. In that case loads might exceed the compression strength of the rod depending on its size and length. Stiffening may be required Or replace with steel angle Uni-strut rod stiffening examples.

89 Services and Ceilings Overhead light fixtures in T-bar ceiling grids have often been damaged in past earthquakes with fixtures becoming dislodged and falling. Damage to light fixtures in flush plasterboard ceilings has been less common. The attachment of safety wires to light fixtures and cushion head boxes ensures that while they may fall from the ceiling grid and dangle from the safety wire after an earthquake they will not threaten occupants. The splaying of the safety wires from the fixtures or box provides some lateral restraint.

90 Services and Ceilings Safety wires are not required where: Light fittings or cushion head boxes are in flush plasterboard ceilings. Light fixtures and cushion boxes are supported and braced independently of the ceiling. The ceiling grid has been specifically designed to provide vertical and lateral restraint to the light fixtures and cushion head boxes and fixings are provided to transmit the seismic force from the lights and boxes to the ceiling grid. Source: FEMA 454, December 2006, Designing for Earthquakes.

91 Services in T-bar ceilings??

92 Services and Ceilings Photo: Example of a poorly installed safety wire, note two wires should be installed for this fixture and wire twists are not tight enough at ends. Source: FEMA E-74, January 2011, Reducing the Risks of Nonstructural Earthquake Damage A Practical Guide.

93 Seismic Restraint Examples

94 Seismic Restraint examples There are many techniques available to comply with Section 8 of AS and prevent damage to services in an earthquake: Using anchor bolts to provide rigid anchorage to a structural floor or wall Bracing components to a structural floor or wall Providing a tether or safety cable to limit the range of movement if the component falls or swings Providing stops or bumpers to limit the range of movement if the component is on vibration isolators or can slide or swing, Providing flexible connections for piping and conduit where they cross seismic joints or connect to rigidly mounted equipment.

95 Seismic Restraint examples Pipework restraint

96 Seismic Restraint examples Pipework restraint

97 Seismic Restraint examples Pipework restraint

98 Seismic Restraint examples Pipework restraint

99 Seismic Restraint examples On concrete floor Under concrete floor

100 Seismic Restraint examples Equipment restraint

101 Seismic Restraint examples Cable tray restraint

102 Seismic Restraint examples Ductwork restraint

103 Restraint examples Vibration mount with seismic stops Seismic restraints Equipment anchorage

104 Seismic Restraint examples Stud wall restraint

105 Seismic Restraint examples

106 Seismic Restraint examples Stud wall restraint

107 Seismic Restraint examples Stud wall restraint

108 Seismic Restraint examples

109 Seismic Restraint examples

110 Seismic Restraint examples

111 Seismic Restraint examples

112 Seismic Restraint examples Gas bottle restraint

113 Flexible connection examples Services crossing structural separations - offsets, loops and bends are best.

114 Summary For most DPTI projects the services and components need to be braced and/or fixed to resist 10% of their dead weight horizontally. The bracing, brackets, anchors etc used to brace the services and components against seismic loads need to be suitably rated. Small piping, small to medium size ducting and services hung by individual hangers 300mm or less from a support are not required to be braced unless part of a life safety system. Clearances are required between different services and between services and ceiling supports/hangers or ceiling members Support of services in ceilings, particularly T-bar, needs closer attention.

115 Conclusion Our intent is that in the near future the restraint of services to comply with Section 8 of AS is documented in detail on DPTI projects prior to tender such that: Proper allowance is made in tenders for seismic bracing. Seismic bracing of services is correctly installed. Consultants and DPTI Inspectors know what to expect on site. AS and thereby the National Construction Code is complied with.

116 Further Information

117 Questions? During an Earthquake