Earthquake demand

The first step is to determine the earthquake demand on all of the components that make up the engineering systems within the building. This is the procedure to determine earthquake demand:

Classify the building importance level and component categories.
Determine the earthquake load demand (static forces).

Calculating earthquake load demand

The earthquake load demand (F) on a component for each design criterion should be calculated by multiplying the lateral force coefficient (C) by the operating weight of the component (W) in the equation:

F = C x W

The lateral force coefficient can be found using the component’s height (C_H), the building’s earthquake zone factor (Z), the component performance factor (C_p) and the component risk factor (R_C) in the equation:

C = 2.7 x C_Hx Z x C_px R_C

where C_H is 3.0 for components that are above the ground floor or 1.0 for components that are on or below the ground floor. C need not be greater than 3.6.

Earthquake zones

The earthquake zone factor (Z) represents the relative level of seismicity for the building’s location in New Zealand. It can be determined from NZS 4219:2009 or NZS 1170.5:2004 or derived from the following map. These must all be modified in accordance with Amendment 10 of the Building Code citation of NZS 1170.5:2004. This states that, for buildings in the Canterbury Earthquake Region with a building structure period less than 1.5 seconds, the zone factor should not be less than 0.3.

Relative seismicity for the design of seismic restraints for engineering systems. (From NZS 4219:2009 Figure 2, provided by Standards New Zealand under licence 001149)

Performance factor

NZS 4219:2009 Table 4 provides for a performance factor (C_p), which can be used to determine the load on each part of the restraint system.

Component	Importance level	Component category	Performance factor (C_p)
Anchors, fixings and fasteners	1, 2, 3, 4	All	0.85
Braces and supports	1, 2, 3, 4	P1, P2, P3, P4 (ULS)	Lower of 0.85 or from the table below
Braces and supports	1, 2, 3	P6, P7 (SLS1)	0.85
Braces and supports	4	P5 (SLS2)	0.85

(From NZS 4219:2009, provided by Standards New Zealand under licence 001149)

NZS 4219:2009 Appendix C shows normative performance factors for specific components and their specific type of installation.

Component	Type	Restraint	Performance factor (C_p)
Horizontal or vertical piping	Steel, flanged joints Steel, welded or grooved joints		0.45
	Steel, screwed joints		0.65
	Copper, brazed joints		0.55
	Polypropylene		0.25
Horizontal or vertical rigid ducting (including in-line components)		Suspended and braced to the structure	0.45
Rigid metal exhaust flue		Braced to the structure	0.45
Rigid metal exhaust flue		Cantilevered from its base	0.55
Cable tray		Suspended and braced to the structure	0.45
Tank (non-pressure)	Floor mounted	Ductile base fixing	0.55
		Limited ductile base fixing	0.85
		Braced to the structure	0.55
		Directly attached to a timber or steel wall (such as hot water cylinder)	0.55
		Directly attached to concrete or masonry wall	0.85
	On a stand	Two-way moment-resisting stand	0.45
	On a stand	Braced to the structure	0.55
Pressure tank (for example, LPG tank)		Floor-mounted cradle	0.85
Compact component (boiler, pump, solid-fuel burner)	Floor mounted	Ductile base fixing	0.55
		Limited ductile base fixing	0.85
		Vibration isolation	0.75
		Braced to the structure	0.55
	Suspended	Suspended and braced to the structure	0.55
Non-compact component (such as chiller or cooling tower)		Floor mounted	0.45
Metal cabinet (such as electrical, communication, rack-mounted computer equipment)		Floor mounted	0.45
		Braced to the structure	0.55
Light fitting (excluding lights mounted on suspended ceilings)		Directly fixed to the structure	0.85
		Suspended and braced to the structure	0.55

(From NZS 4219:2009, provided by Standards New Zealand under licence 001149)

Risk factor

The component risk factor (R_C) can be determined from NZS 4219:2009 Table 5 using a known importance level and component category. Note that, following the 2010–11 earthquakes, the component risk factor for buildings in the Canterbury Earthquake Region should not be less than 0.33.

Component category	Risk factor (R_C)
	Importance level
	1 and 2	3	4
P1, P2, P4	1.00	1.30	1.80
P3	0.90	1.20	1.60
P5	NA	NA	1.00
P6	0.50	0.50	0.50
P7	0.25	0.25	0.25

(From NZS 4219:2009, provided by Standards New Zealand under licence 001149)