Section 3104F — California Building Code (Title 24, Part 2)

SEISMIC ANALYSIS AND STRUCTURAL PERFORMANCE

3104F.1 General.¶

3104F.1.1 Purpose. The purpose of this section is to establish minimum standards for seismic analysis and structural performance. Seismic performance is evaluated at two criteria levels. Level 1 requirements define a per- formance criterion to ensure MOT functionality. Level 2 requirements safeguard against major damage, collapse or major oil spill.

3104F.1.2 Applicability. Section 3104F applies to all new and existing MOTs. Structures supporting loading arms, pipelines, oil transfer and storage equipment, critical sys- tems and vessel mooring structures, such as mooring and breasting dolphins are included. Catwalks and similar components that are not part of the lateral load carrying system and do not support oil transfer equipment may be excluded.

3104F.1.3 Configuration classification of MOT struc- ture. Each MOT structure shall be designated as regular or irregular based on torsional irregularity criteria pre- sented in ASCE/SEI 7 [4.1]. An MOT structure is defined to be irregular when maximum displacement at one end of the MOT structure transverse to an axis is more than 1.2 times the average of the displacement at the two ends of the MOT structure, as described in Figure 31F-4-1. For MOTs with multiple segments separated by expansion joints, each segment shall be designated as regular or irregular using criteria in this section. Expansion joints in this context are defined as joints that separate each struc- tural segment in such a manner that each segment will

3104F.2 Existing MOTs¶

3104F.2.1 Seismic Performance Criteria. Two levels of seismic performance shall be considered, except for criti- cal systems (Section 3104F.5.1). These levels are defined as follows:

Level 1 Seismic Performance:

· Minor or no structural damage

· Temporary or no interruption in operations

Level 2 Seismic Performance:

· Controlled inelastic behavior with repairable

damage

· Prevention of collapse

· Temporary loss of operations, restorable within

months

· Prevention of major spill ( ≥ 1200 bbls)

The Level 1 and Level 2 seismic performance criteria are defined in Table 31F-4-1.

3104F.2.2 Basis for evaluation. Component capacities shall be based on existing conditions, calculated as “best estimates,” taking into account the mean material strengths, strain hardening and degradation overtime. The capacity of components with little or no ductility, which may lead to brittle failure scenarios, shall be calculated based on lower bound material strengths. Methods to establish component strength and deformation capacities for typical structural materials and components are pro- vided in Section 3107F. Geotechnical considerations are discussed in Section 3106F.

3104F.2.3 Analytical procedures. The objective of the seis- mic analysis is to verify that the displacement capacity of the structure is greater than the displacement demand, for each performance level defined in Table 31F-4-1. For this pur- pose, the displacement capacity of each element of the struc- ture shall be checked against its displacement demand including the orthogonal effects of Section 3104F.4.2. The required analytical procedures are summarized in Table 31F-4-2.

The displacement capacity of the structure shall be cal- culated using the nonlinear static (pushover) procedure. For the nonlinear static (pushover) procedure, the push- over load shall be applied at the target node defined as the center of mass (CM) of the MOT structure. It is also acceptable to use a nonlinear dynamic procedure for capacity evaluation, subject to peer review in accordance with Section 3101F.8.2.

Methods used to calculate the displacement demand are linear modal, nonlinear static and nonlinear dynamic.

Mass to be included in the displacement demand calcu- lation shall include mass from self-weight of the structure, weight of the permanent equipment, and portion of the live load that may contribute to inertial mass during earth- quake loading, such as a minimum of 25% of the floor live load in areas used for storage.

Any rational method, subject to the Division’s approval, can be used in lieu of the required analytical procedures shown in Table 31F-4-2.

3104F.2.3.1 Nonlinear static capacity procedure (push- over). To assess displacement capacity, two-dimensional nonlinear static (pushover) analyses shall be performed; three-dimensional analyses are optional. A model that incorporates the nonlinear load deformation character- istics of all components for the lateral force-resisting system shall be used in the pushover analysis.

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TABLE 31F-4-1 SEISMIC PERFORMANCE CRITERIA ^{1, 2}

SPILL CLASSIFICATION3	SEISMIC PERFORMANCE LEVEL	PROBABILITY OF EXCEEDANCE	RETURN PERIOD
High	Level 1	50% in 50 years	72 years
High	Level 2	10% in 50 years	475 years
Medium	Level 1	65% in 50 years	48 years
Medium	Level 2	15% in 50 years	308 years
Low	Level 1	75% in 50 years	36 years
Low	Level 2	20% in 50 years	224 years

1. For new MOTs, see Section 3104F.3. 2. For marine terminals transferring LNG, return periods of 72 and 475 years shall be used for Levels 1 and 2, respectively. 3. See Section 3101F.6 for spill classification.

TABLE 31F-4-2 MINIMUM REQUIRED ANALYTICAL PROCEDURES

SPILL CLASSIFICATION1	CONFIGURATION	SUBSTRUCTURE MATERIAL	DISPLACEMENT DEMAND PROCEDURE	DISPLACEMENT CAPACITY PROCEDURE
High/Medium	Irregular	Concrete/Steel	Linear Modal	Nonlinear Static
High/Medium	Regular	Concrete/Steel	Nonlinear Static2	Nonlinear Static
Low	Regular/Irregular	Concrete/Steel	Nonlinear Static	Nonlinear Static
High/Medium/Low	Regular/Irregular	Timber	Nonlinear Static	Nonlinear Static

1. See Section 3101F.6 for spill classification. 2. Linear modal demand procedure may be required for cases where more than one mode is expected to contribute to the displacement demand.

Alternatively, displacement capacity of a pile in the MOT structure may be estimated from pushover analy- sis of an individual pile with appropriate axial load and pile-to-deck connection.

The displacement capacity of a pile from the push- over analysis shall be defined as the displacement that can occur at the top of the pile without exceeding plas- tic rotation (or material strain) limits, either at the pile- deck hinge or in-ground hinge, as defined in Section 3107F. If pile displacement has components along two axes, as may be the case for irregular MOTs, the pile displacement capacity shall be defined as the resultant of its displacement components along the two axes.

can occur at the top of the pile without exceeding plas- tic rotation (or material strain) limits, either at the pile- deck hinge or in-ground hinge, as defined in Section 3107F. If pile displacement has components along two axes, as may be the case for irregular MOTs, the pile displacement capacity shall be defined as the resultant of its displacement components along the two axes.

3104F.2.3.1.1 Modeling. A series of nonlinear pushover analyses may be required depending on the complexity of the MOT structure. At a minimum, pushover analysis of a two-dimensional model shall be conducted in both the longitudinal and transverse directions. The piles shall be represented by nonlin- ear elements that capture the moment-curvature/ rotation relationships for components with expected inelastic behavior in accordance with Section 3107F. The effects of connection flexibility shall be considered in pile-to-deck connection modeling. For prestressed concrete piles, Figure 31F-4-2 may be used. A nonlinear element is not required to repre- sent each pile location. Piles with similar lateral force-deflection behavior may be lumped in fewer larger springs, provided that the overall torsional effects are captured.

Linear material component behavior is accept- able where nonlinear response will not occur. All components shall be based on effective moment of

inertia calculated in accordance with Section 3107F. Specific requirements for timber pile struc- tures are discussed in the next section.

3104F.2.3.1.2 Timber pile supported structures. For all timber pile supported structures, linear elas- tic procedures may be used. Alternatively, the non- linear static procedure may be used to estimate the target displacement demand, Δ d.

A simplified single pile model for a typical tim- ber pile supported structure is shown in Figure 31F- 4-3. The pile-deck connections may be assumed to be “pinned.” The lateral bracing can often be

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ignored if it is in poor condition. These assumptions shall be used for the analysis, unless a detailed con- dition assessment and lateral analysis indicate that the existing bracing and connections may provide reliable lateral resistance.

A series of single pile analyses may be sufficient to establish the nonlinear springs required for the pushover analysis.

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The first step in the Coefficient Method requires idealization of the pushover curve to calculate the effective elastic lateral stiffness, ke, and effective yield strength, Fy, of the structure as shown in Fig- ure 31F-4-4.

3104F.2.3.2 Nonlinear static demand procedure. A nonlinear static procedure shall be used to determine the displacement demand for all concrete and steel structures, with the exception of irregular configura- tions with high or moderate spill classifications. A lin- ear modal procedure is required for irregular structures with high or moderate spill classifications, and may be used for all other classifications in lieu of the nonlinear static procedure.

In the nonlinear static demand procedure, deforma- tion demand in each element shall be computed at the target node displacement demand. The analysis shall be conducted in each of the two orthogonal directions and results combined as described in Section 3104F.4.2.

The target displacement demand of the structure, Δ d, shall be calculated from:

Δ d = SA(Te2/4 π 2) (4-1)

where:

Te = effective elastic structural period defined in

Equation (4-3) or Equation (4-9)

SA = spectral response acceleration corresponding

to Te If Te < T0, where T0 is the period corresponding to the peak of the acceleration response spectrum, a refined analysis (see Section 3104F.2.3.2.1 or 3104F.2.3.2.2) shall be used to calculate the displace- ment demand. In the refined analysis, the target node displacement demand may be computed from the Coef- ficient Method (Section 3104F.2.3.2.1) or the Substitute Structure Method (Section 3104F.2.3.2.2). Both of these methods utilize the pushover curve developed in Section 3104F.2.3.1.

3104F.2.3.2.1 Coefficient Method. The Coefficient Method is based on the procedures presented in ASCE/ SEI 41 [4.3] and FEMA 440 [4.4].

The first line segment of the idealized pushover curve shall begin at the origin and have a slope equal to the effective elastic lateral stiffness, ke. The effective elastic lateral stiffness, ke, shall be taken as the secant stiffness calculated at the lateral force equal to 60 percent of the effective yield strength, Fy, of the structure. The effective yield strength, Fy, shall not be taken as greater than the maximum lat- eral force at any point along the pushover curve.

The second line segment shall represent the posi- tive post-yield slope ( α 1ke) determined by a point (Fd, Δ d) and a point at the intersection with the first line segment such that the area above and below the actual curve area approximately balanced. (Fd, Δ d) shall be a point on the actual pushover curve at the calculated target displacement, or at the displace- ment corresponding to the maximum lateral force, whichever is smaller.

The third line segment shall represent the nega- tive post-yield slope ( α 2ke), determined by the point at the end of the positive post-yield slope (Fd, Δ d) and the point at which the lateral force degrades to 60 percent of the effective yield strength.

The target displacement shall be calculated from:

where:

SA = spectral acceleration of the linear-elastic

system at vibration period, which is computed from:

Δ d = C 1 C 2 SA ------ ^Te

= C 1 C 2 SA ------4 ^T π ^e - 2

(4-2)

(4-3)

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where:

m = seismic mass as defined in Section

3104F.2.3

ke = effective elastic lateral stiffness from

idealized pushover

C1 = modification factor to relate maximum

inelastic displacement to displacement calculated for linear elastic response. For period less than 0.2 s, C1 need not be taken greater than the value at Te = 0.2 s. For period greater than 1.0 s, C1 = 1.0. For all other periods:

μ strength - 1 C 1 = 1 + ----------------------- aTe 2 -

where:

a = Site class factor

= 130 for Site Class A or B,

= 90 for Site Class C, and

= 60 for Site Class D, E, or F.

(4-4)

h = 1 + 0.15lnTe (4-8) α e = effective negative post-yield slope ratio which

shall be computed from:

α e = α P- Δ + λ ( α2 - α P- Δ ) (4-9)

where:

α P- Δ , and the maximum negative post-elastic stiff- ness ratio, α2 , are estimated from the idealized force-deformation curve, and λ is a near-field effect factor equal to 0.8 for sites with 1 second spectral value, S 1 greater than or equal to 0.6g and equal to 0.2 for sites with 1 second spectral value, S 1 less than 0.6g.

3104F.2.3.2.2 Substitute Structure Method. The Substitute Structure Method is based on the proce- dure presented in Priestley et al. [4.5] and ASCE/ COPRI 61 [4.2]. This method is summarized below.

1. Idealize the pushover curve from nonlinear pushover analysis, as described in Section 3104F.2.3.2.1, and estimate the effective yield strength, Fy, and yield displacement, Δ y.

2. Compute the effective elastic lateral stiffness, ke, as the effective yield strength, Fy, divided by the yield displacement, Δ y.

3. Compute the structural period in the direction under consideration from:

μ strength = ratio of elastic strength demand to yield

strength coefficient calculated in accordance with Equation (4-6). The Coefficient Method is not applicable where μ strength exceeds μ max computed from Equation (4-7). μ strength shall not be taken as less than 1.0.

C2 = modification factor to represent the effects

of pinched hysteresis shape, cyclic stiffness degradation, and strength deterioration on the maximum displacement response. For periods greater than 0.7s, C2 = 1.0. For all other periods:

where:

(4-10)

C 2 = 1 + -------1 - ----------------------- ^μ ^strength - 1 - 2 800 Te

(4-5)

m =seismic mass as defined in Section

3104F.2.3

ke =effective elastic lateral stiffness in

direction under consideration

4. Determine target displacement, Δ d , of the effective linear elastic system from:

The strength ratio μ strength shall be computed from:

mSA μ strength = -------- Fy

where:

(4-6)

Δ d = SA ------ ^Te

= SA ------4 ^T π ^e - 2

(4-11)

Fy = effective yield strength of the structure in

the direction under consideration from the idealized pushover curve.

For structures with negative post-yield stiffness, the maximum strength ratio μ max shall be computed from:

Δ d α e - h

= --- - + ------ -

(4-7)

Δ d α e μ max = --- - + ------ - Δ y 4

α e

------ - 4

where:

SA =the 5 percent damped spectral displace-

ment corresponding to the linear elastic structural period, Te

Select the initial estimate of the displacement demand as Δ d, i = Δ d .

5. The ductility level, μΔ ,i, is found from Δ d,i / Δ y. Use the appropriate relationship between duc- tility and damping, for the component undergo- ing inelastic deformation, to estimate the effective structural damping, ξ eff,i. In lieu of more detailed analysis, Equation (4-12) may be used for concrete and steel piles connected to the deck through dowels embedded in the con- crete. Note that the idealized pushover curves in Figure 31F-4-4 shall be utilized in Figure 31F- 4-5, which illustrates the iterative procedure.

where:

Δ d = larger of target displacement or displacement corresponding to the maximum pushover force,

Δ y = displacement at effective yield strength

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(4-12)

where:

α1 =ratio of second slope over elastic slope

(see Figures 31F-4-4 and 31F-4-5)

Equation (4-12) for effective damping was developed by Kowalsky et al. [4.6] for the Takeda hysteresis model of system’s force-dis- placement relationship.

6. Compute the force, Fd,i, on the force-deforma- tion relationship associated with the estimated displacement, Δ d,i (see Figure 31F-4-5).

7. Compute the effective stiffness, keff,i, as the secant stiffness from:

Fd, i keff, i = ------ - Δ d, i

(4-13)

8. Compute the effective period, Teff,i, from:

where:

(4-14)

m =seismic mass as defined in Section

3104F.2.3

9. For the effective structural period, Teff,i, and the effective structural damping, ξ eff,i, compute the spectral acceleration SA (Τ eff,i, ξ eff,i) from an appropriately damped design acceleration response spectrum.

10. Compute the new estimate of the displace- ment, Δ d, j, from:

T 2 eff, i Δ d, j = --------2 -

Teff, i

= --------4π2 - SA ( Teff, i, ξ eff, i )

(4-15)

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11. Repeat steps 5 to 10 with Δ d, i = Δ d, j until displacement, Δ d, j, computed in step 10 is sufficiently close to the starting displace- ment, Δ d, i, in step 5 (Figure 31F-4-5).

3104F.2.3.3 Linear modal demand procedure. For irregular concrete/steel structures with moderate or high spill classifications, a linear modal analysis is required to predict the global displacement demands. A 3-D linear elastic response analysis shall be used, with effective moment of inertia applied to components to establish lateral displacement demands, to compute displacement components of an element along each axis of the system.

Sufficient modes shall be included in the analysis such that 90 percent of the participating mass is cap- tured in each of the principal horizontal directions for the structure. For modal combinations, the Complete Quadratic Combination rule shall be used. Multidirec- tional excitation shall be accounted for in accordance with Section 3104F.4.2.

The lateral stiffness of the linear elastic response model shall be based on the initial stiffness of the non- linear pushover curve as shown in Figure 31F-4-6 (also see Section 3106F.9). The p-y springs shall be adjusted based on the secant method approach. Most of the p-y springs will typically be based on their initial stiffness; no iteration is required.

If the fundamental period is T < T0, where T0 is the period corresponding to the peak of the acceleration response spectrum, the displacement demand from the linear modal analysis shall be amplified to account for nonlinear system behavior by an amplification factor. The amplification factor shall be equal to either C1 × C2 per Section 3104F.2.3.2.1, or the ratio of the final target displacement and the initial elastic displacement of Equation (4-11) per Section 3104F.2.3.2.2.

SUBSTITUTE STRUCTURE METHOD STIFFNESS FOR LINEAR MODAL ANALYSIS

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3104F.2.3.4 Nonlinear dynamic analysis. Nonlinear dynamic time history analysis is optional, and if per- formed, a peer review is required (see Section 3101F.8.2). Multiple acceleration records shall be used, as explained in Section 3103F.4.2.10. The follow- ing assumptions may be made:

1. Equivalent “super piles” can represent groups of piles.

2. If the deck has sufficient rigidity (both in-plane and out-of plane) to justify its approximation as a rigid element, a 2-D plan simulation may be ade- quate.

A time-history analysis should always be compared with a simplified approach to ensure that results are reasonable. Displacements calculated from the nonlin- ear time history analyses may be used directly in design, but shall not be less than 80 percent of the val- ues obtained from Section 3104F.2.3.2.

3104F.2.3.5 Alternative procedures. Alternative lateral- force procedures using rational analyses based on well- established principles of mechanics may be used in lieu of those prescribed in these provisions. As per Section 3101F.8.2, peer review is required.

3104F.3 New MOTs.¶

The analysis and design requirements described in Section 3104F.2 shall also apply to new MOTs. However, new MOTs shall comply with the seismic perfor- mance criteria for high spill classification, as defined in Table 31F-4-1. Additional requirements are as follows:

1. Site-specific response spectra analysis (see Section 3103F.4.2.3).

2. Soil parameters based on site-specific and new borings (see Section 3106F.2.2).

3104F.4 General analysis and design requirements.¶

3104F.4.1 Load combinations. Earthquake loads shall be used in the load combinations described in Section 3103F.8.

3104F.4.2 Combination of orthogonal seismic effects. The design displacement demand at an element, δ d, shall be calculated by combining the longitudinal, δ x, and transverse, δ y, displacements in the horizontal plane (Figure 31F-4-7):

where:

δ x = δ xy + 0.3δ xx (4-17)

and δ y = 0.3δ yx + δ yy (4-18)

OR δ y = δ yx + 0.3δ yy (4-19)

and δ x = 0.3δ xy + δ xx (4-20)

whichever results in the greater design displacement demand. 3104F.4.3 P- Δ Effects. The P- Δ effect (i.e., the addi- tional moment induced by the total vertical load multi- plied by the lateral deck deflection) shall be considered unless the following relationship is satisfied (see Figure 31F-4-8):

V --- - ≥ 4--- ^Δ - ^d W H

where:

(4-21)

(4-16)

V = base shear strength of the structure obtained

from a plastic analysis

W = dead load of the frame Δ d = displacement demand H = distance from the location of maximum in-ground

moment to center of gravity of the deck

FIGURE 31F-4-8

P- Δ EFFECT

FIGURE 31F-4-7 PLAN VIEW OF WHARF SEGMENT UNDER X AND Y SEISMIC EXCITATIONS

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For wharf structures where the lateral displacement is limited by almost fully embedded piles, P- Δ effects may be ignored; however, the individual stability of the piles shall be checked in accordance with Section 3107F.2.5.2.

If the landside batter piles are allowed to fail in a Level 2 evaluation, the remaining portion of the wharf shall be checked for P- Δ effects.

3104F.4.4 Expansion joints. The effect of expansion joints shall be considered in the seismic analysis.

3104F.4.5 Shear key forces. Shear force across shear keys connecting adjacent wharf segments, Vsk, (approxi- mate upper bound to the shear key force [4.7]) shall be calculated as follows:

Vsk = 1.5( e/Ll ) V Δ T (4-22)

where:

V Δ T = total segment lateral force found from a push-

over analysis Ll = segment length e = eccentricity between the center of rigidity and the

center of mass

3104F.4.6 Connections. For an existing wharf, the deteri- orated conditions at the junction between the pile top and pile cap shall be considered in evaluating the moment capacity. Connection detail between the vertical pile and pile cap shall be evaluated to determine whether full or partial moment capacity can be developed under seismic action.

For new MOTs, the connection details shall develop the full moment capacities.

The modeling shall simulate the actual moment capac- ity (full or partial) of the joint in accordance with Section 3107F.2.7.

3104F.4.7 Batter piles. Batter piles primarily respond to earthquakes by developing large axial compression or ten- sion forces. Bending moments are generally of secondary importance. Failure in compression may be dictated by the deck-pile connection (most common type), material compression, buckling, or by excessive local shear in deck members adjacent to the batter pile. Failure in tension may be dictated by connection strength or by pile pull out (p. 3-83 of Ferritto et al. [4.7]).

When the controlling failure scenario is reached and the batter pile fails, the computer model shall be adjusted to consist of only the vertical pile acting either as a full or partial moment frame based on the connection details between the pile top and pile cap. The remaining displace- ment capacity, involving vertical piles, before the second- ary failure stage develops, shall then be established (see Section 3107F.2.8).

Axial p-z curves shall be modeled. In compression, dis- placement capacity should consider the effect of the reduc- tion in pile modulus of elasticity at high loads and the increase in effective length for friction piles. This procedure allows the pile to deform axially before reaching ultimate loads, thereby increasing the displacement ductility [4.7].

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Horizontal nonlinear p-y springs are only applied to batter piles with significant embedment, such as for land- side batter piles in a wharf structure. Moment fixity can be assumed for batter piles that extend well above the ground such as waterside batter piles in a wharf structure or bat- ter piles in a pier type structure.

3104F.5 Nonstructural components,¶

nonbuilding structures and building structures. Nonstructural components, non- building structures and building structures at MOTs shall be assessed for Level 2 seismic performance (see Section 3104F.2.1). Consideration shall be given to the adequacy and condition of supports and attachments (or anchorage), strength, flexibility, relative displacement, P-delta effects, and seismically-induced interaction with other components and structures.

3104F.5.1 General. Nonstructural components are mechanical, electrical and architectural components (such as piping/pipelines, loading arms, lifting equipment (winches and cranes), spill prevention equipment, pumps, instrumentation and storage cabinets, and lighting fix- tures) that may be required to resist the effects of earth- quake.

Nonbuilding structures (such as gangways, hose towers and racks) are self-supporting structures that carry grav- ity loads and may be required to resist the effects of earth- quake, but are not building structures (such as control rooms). For building structures, see Section 3104F.5.6.

Critical systems are nonstructural components, non- building structures or building structures that shall remain operational or those whose failure could impair emergency operations following an earthquake, to prevent major oil spills and to protect public health, safety and the environment. A seismic assessment of the survivability and continued operation (related to personnel safety, oil spill prevention or response) during a Level 2 earthquake (see Table 31F-4-1) shall be performed for critical systems, including but not limited to, fire protection, emergency shutdown and electrical power systems.

3104F.5.2 Seismic assessment. For existing (E) nonstruc- tural components, nonbuilding structures and building structures and their supports and attachments, seismic assessment shall be performed in accordance with CalARP [4.8] or ASCE Guidelines [4.9], except for pip- ing/pipelines which shall be evaluated per Section 3109F. If seismic evaluation and/or strengthening are required, it shall be performed in accordance with Section 3104F.5.2.1.

For new (N) nonstructural components, nonbuilding structures and building structures and their supports and attachments, seismic evaluation and design shall be per- formed in accordance with Section 3104F.5.2.1, except for piping/pipelines which shall be evaluated per Section 3109F.

3104F.5.2.1 Seismic evaluation, strengthening and design. For evaluation, strengthening and design of nonstructural components, nonbuilding structures and building structures, seismic forces (demands) shall be obtained from Section 3104F.5. The seismic adequacy

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of nonstructural components shall be demonstrated as specified in ASCE/SEI 7 [4.1]. Structures shall be ana- lyzed in accordance with Section 3107F.5. Supports and attachments shall be assessed in accordance with Sections 3107F.7.

3104F.5.3 Contribution to global response of MOT structures. Nonstructural components, nonbuilding struc- tures and building structures permanently attached to MOT structures, including, but not limited to, pipelines, loading arms, hose towers/racks, raised platforms, control rooms and vapor control equipment, may affect the global structural response. In such cases, the seismic character- istics (mass and/or stiffness) of the nonstructural compo- nents, nonbuilding structures and building structures shall be considered in computing global seismic response of the MOT structures. If the seismic response of nonstructural components is determined to be out of phase (e.g. pipe- lines) with the global structural response, then the mass contribution can be neglected in the seismic structural analysis.

3104F.5.4 Nonstructural components and nonbuilding structures permanently attached to MOT structures. This section covers nonstructural components and nonbuilding structures having a significant mass and/or importance to the operability and safety of the MOT, and that are perma- nently attached to MOT structures (e.g., wharves, trestles, dolphins). The weight of nonstructural components and nonbuilding structures shall be included in the dead load of the structure per Section 3103F.2.

Computation of seismic effects shall consider:

1. Amplification of acceleration from ground to loca- tion of attachment of the nonstructural component or nonbuilding structure to the deck due to flexibility of the MOT structure, and

2. Amplification of acceleration due to flexibility of the nonstructural component or nonbuilding structure.

The following are not covered in this section and shall be assessed using rational approach that includes consid- eration of strength, stiffness, ductility, and seismic interac- tion with all other connected components and with the supporting structures or systems, subject to Division approval:

1. Nonstructural component supported by other non- structural system permanently attached to MOT structure;

2. Nonstructural component or nonbuilding structure supported by other structure permanently attached to MOT structure;

3. Nonstructural component or nonbuilding structure attached to multiple MOT structures;

4. Nonstructural component or nonbuilding structure attached to structure and ground.

3104F.5.4.1 Seismic loads. This section specifies the procedure to compute seismic loads on nonstructural components and nonbuilding structures permanently attached to a MOT structure.

The following nonstructural components are exempt from the requirements of this section:

1. Temporary or movable equipment unless part of a critical system (Section 3104F.5.1);

2. Mechanical and electrical components that are attached to the MOT structure and have flexible connections to associated piping and conduit; and either:

(a) The component weighs 400 lb or less, the

center of mass is located 4 ft or less above the MOT deck, and the component Impor- tance Factor, Ip is equal to 1.0; or

(b) The component weighs 20 lb or less, or in

the case of a distributed system, 5 lb/ft or less.

3104F.5.4.1.1 Simplified Procedure. The Simplified Procedure may be used to estimate seismic loads on nonstructural components and nonbuilding struc- tures permanently attached to a MOT structure. The Simplified Procedure shall not be used if any of the following apply:

1. Mass of the nonstructural component or non- building structure exceeds 25 percent of the combined mass of the MOT structure plus nonstructural component or nonbuilding structure;

2. Multiple nonstructural components or non- building structures of similar type (or natural period) when their combined mass exceeds 25 percent of the total mass of the MOT structure plus nonstructural components or nonbuilding structures;

3. Concrete/Steel MOT structure with irregular configuration (Section 3104F.1.3 and Table 31F-4-2) and high or medium spill exposure classification.

The horizontal seismic force, Fp, shall be com- puted as follows [4.10]:

Sxs = spectral acceleration in Section 3103F.4.2.4

or Section 3103F.4.2.5

ap = amplification factor for nonstructural

component or nonbuilding structure (Table 31F-4-3)

Ip = importance factor for nonstructural component or nonbuilding structure (Table 31F-4-4)

Wp = weight of the nonstructural component or

nonbuilding structure

1.2 SxsapIpWp Fp = -----------------------------Rp

0.3SxsIpWp ≤ Fp ≤ 1.6SxsIpWp

where:

(4-23)

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Rp = response modification factor for nonstructural

component or nonbuilding structure (Table 31F-4-5)

Alternatively, when dynamic properties of the MOT structure are available, the horizontal seismic force, Fp, may be computed from [4.10]:

AND NONBUILDING	STRUCTURES
*COMPONENT OR STRUCTURE*	lp
Critical1, 2	1.5
Other	1.0

apSAIpAxWp Fp = -------------------------- Rp

0.3SxsIpWp ≤ Fp ≤ 1.6SxsIpWp

where:

(4-24)

SA = spectral acceleration in Section 3103F.4.2.4

or Section 3103F.4.2.5, at the period equal to the elastic fundamental period of the MOT structure, T, in direction under consideration

Ax = torsional amplification factor given by:

Ax = ---------------Δ m - 2 1.2Δ avg

1 ≤ Ax ≤ 3

where:

(4-25)

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TABLE 31F-4-4 IMPORTANCE FACTORS FOR NONSTRUCTURAL COMPONENTS

1. See Section 3104F.5.1 for definition of critical system. 2. A lower value may be utilized, subject to Division approval.

TABLE 31F-4-5 RESPONSE MODIFICATION FACTORS FOR NONSTRUCTURAL

COMPONENTS AND NONBUILDING STRUCTURES

Δ m = maximum displacement at one end of the

MOT structure transverse to an axis

Δ avg = average of the displacements at the

extreme points of the MOT structure (see Figure 31F-4-1)

TABLE 31F-4-3 AMPLIFICATION FACTORS FOR NONSTRUCTURAL

COMPONENTS AND NONBUILDING STRUCTURES

*COMPONENT OR STRUCTURE*	ap *1, 2*
Rigid components or structures (period less than 0.06 seconds)	1.0
Rigidly attached components or structures	1.0
Flexible components or structures (period longer than 0.06 seconds)	2.5
Flexibly attached components or structures	2.5

1. A lower value shall not be used unless justified by detailed dynamic analysis, and shall in no case be less than 1.0. 2. If the fundamental period of the MOT structure, T, and the period of the flexible nonstructural component or nonbuilding structure, Tp, is known, ap may be estimated from Figure 31F-4-9.

FIGURE 31F-4-9 AMPLIFICATION FACTOR, a p [4.10]

COMPONENT OR STRUCTURE	R1 p
Loading arms	3.0
Piping/pipelines (welded)	12.0
Pining/pipelines (threaded or flanged)	6.0
Pumps	2.5
Skids	2.5
Tanks and totes	2.5
Light fixtures (or luminaries)	1.5
Electrical conduits and cable trays	6.0
Mooring hardware	2.5
Velocity monitoring equipment	2.5
Instrumentation or storage cabinets	6.0
Cranes	2.5
Gangway (column systems)	3.0
Gangways (truss systems)	Use Rp from frame systems
Hose towers and racks	Use Rp from frame systems
*Frame systems:* Steel special concentrically braced frames Steel ordinary concentrically braced frames Steel special moment frames Steel intermediate moment frames Steel ordinary moment frames Lightframe wood sheathed with wood structural panels Lightframe cold-formed steel sheathed with wood structural panels Lightframe walls with shear panels of other materials	6.0 3.5 8.0 4.5 3.5 6.5 6.5 2.0
Other	Subject to Division approval

1. A higher value may be utilized, subject to Division approval.

The horizontal seismic force, Fp, in the direction under consideration shall be applied at the center of gravity and distributed relative to the mass distribu- tion of the nonstructural component or nonbuilding structure.

The horizontal seismic force, Fp, shall be applied independently in at least two orthogonal horizontal directions in combination with service or operating loads associated with the nonstructural component or nonbuilding structure, as appropriate. For verti- cally cantilevered systems, however, Fp shall be assumed to act in any horizontal direction.

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The concurrent vertical seismic force, Fv, shall be applied at the center of gravity and distributed relative to the mass distribution of the nonstructural component or nonbuilding structure, as follows:

Fv = ±0.2SxsWp (4-26)

3104F.5.4.1.2 Linear modal demand procedure. The linear modal demand procedure (Section 3104F.2.3.3) may always be used and shall be used to estimate seismic forces when the Simplified Proce- dure (Section 3104F.5.4.1.1) is not permitted. The MOT structure and nonstructural components and/or nonbuilding structures shall be modeled explicitly. The seismic forces obtained from the linear modal demand procedure shall be adjusted for appropriate importance factors and response modification factors as specified in Table 31F-4-4 and Table 31F-4-5.

es when the Simplified Proce-_ dure (Section 3104F.5.4.1.1) is not permitted. The MOT structure and nonstructural components and/or nonbuilding structures shall be modeled explicitly. The seismic forces obtained from the linear modal demand procedure shall be adjusted for appropriate importance factors and response modification factors as specified in Table 31F-4-4 and Table 31F-4-5.

3104F.5.5 Nonstructural components and nonbuilding structures permanently attached to the ground. The seis- mic load shall be computed using the procedures in ASCE/ SEI 7 [4.1], except that Level 2 design earthquake motion parameters defined in Section 3103F.4 shall be used in lieu of those specified in ASCE/SEI 7 [4.1].

3104F.5.6 Building structures. For buildings perma- nently attached to MOT structure, Section 3104F.5.4.1 shall be used to compute seismic loads. Computation of seismic effects shall consider:

1. Amplification of acceleration from ground to loca- tion of attachment of the building to the deck due to flexibility of the MOT structure, and

2. Amplification of acceleration due to flexibility of the building.

For buildings permanently attached to the ground, seis- mic loads shall be computed using the procedures in ASCE/SEI 7 [4.1], as amended by the local enforcing agency requirements, subject to Division approval.

3104F.6 Symbols.¶

a = Site class factor

ap = Amplification factor for nonstructural component or nonbuilding structure

Ax = Torsional amplification factor

C1 = Modification factor to relate expected maximum

inelastic displacement to displacement calculated for linear elastic response

C2 = Modification factor to represent the effects of

pinched hysteresis shape, cyclic stiffness degradation and strength deterioration on the maximum displacement response

e = Eccentricity between center of mass and center

of rigidity

Fd, i = Force at step i of iteration

Fd, j = Force at step j of iteration

Fp = Horizontal seismic force on nonstructural

component, nonbuilding structure or building structure supported on MOT

Fv = Vertical seismic force on nonstructural component, nonbuilding structure or building structure supported on MOT

Fy = Effective yield strength

H = Distance from maximum in-ground moment to

center of gravity of the deck

Ip = Importance factor for nonstructural component

or nonbuilding structure

ke = Effective elastic lateral stiffness

keff, i = Effective secant lateral stiffness at step i of

iteration

keff, j = Effective secant lateral stiffness at step j of

iteration

Ll = Longitudinal length between wharf expansion

joints

m = Seismic mass

Rp = Response modification factor for nonstructural

component or nonbuilding structure

SA = Spectral response acceleration at T

Sxs = Spectral acceleration in Section 3103F.4.2.4 or

Section 3103F.4.2.5

S1 = 1-second spectral response acceleration

T = Fundamental period of the elastic structure

Te = Effective elastic structural period

Teff, i = Effective structural period at step i of iteration

Tp = Period of flexible nonstructural component or

nonbuilding structure

T0 = Period at peak of the acceleration response

spectrum

V = Base shear strength of the structure obtained

from a plastic analysis

Vsk = Shear force across shear keys

V Δ T = Total segment lateral force

W = Dead load of the frame

Wp = Weight of the nonstructural component or

nonbuilding structure

Δ d = Target displacement demand

Δ d, i = Target displacement demand at step i of

iteration

Δ d, j = Target displacement demand at step j of iteration

α 1 = Positive post-yield slope ratio equal to positive

post-yield stiffness divided by the effective stiffness

534 2019 CALIFORNIA BUILDING CODE

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No. SSRP – 94/16, University of California, San Diego.

[4.7] Ferritto, J., Dickenson, S., Priestley N., Werner, S., Taylor, C., Burke, D., Seelig, W., and Kelly, S., 1999, “Seismic Criteria for California Marine Oil Terminals,” Vol. 1 and Vol. 2, Technical Report TR-2103-SHR, Naval Facilities Engineering Ser- vice Center, Port Hueneme, CA.

[4.8] CalARP Program Seismic Guidance Committee, December 2013, “Guidance for California Acci- dental Release Prevention (CalARP) Program Seismic Assessments,” Sacramento, CA.

[4.9] American Society of Civil Engineers, 2011, “Guidelines for Seismic Evaluation and Design of Petrochemical Facilities,” 2nd ed., New York.

[4.10] Goel, R. K., 2017, “Estimating Seismic Forces

in Ancillary Components and Nonbuilding Structures Supported on Piers, Wharves, and Marine Oil Terminals,” Earthquake Spectra, https://doi.org/10.1193/041017EQS068M. Authority: Sections 8750 through 8760, Public Resources Code. Reference: Sections 8750, 8751, 8755 and 8757, Public Resources Code.

α 2 = Negative post-yield slope ratio equal to

negative post-yield stiffness divided by the effective stiffness

α e = Effective negative post-yield slope ratio equal to

effective post-yield negative stiffness divided by the effective stiffness

α P- Δ = Negative slope ratio caused by P- Δ effects

Δ avg = Average of displacements, Δ 1 and Δ 2, at ends of

the MOT transverse to an axis

Δ d = Target displacement

Δ m = Maximum of displacements, Δ 1 and Δ 2, at ends

of the MOT transverse to an axis

Δ y = Displacement at yield strength

Δ 1, Δ 2 = Displacement at ends of the MOT transverse to

an axis

δ d = Design displacement demand at an element

δ x = Displacement of an element in X direction

δ y = Displacement of an element in Y direction

δ xx = X displacement under X direction excitation

δ xy = X displacement under Y direction excitation

δ yx = Y displacement under X direction excitation

δ yy = Y displacement under Y direction excitation

λ = Near-field effect factor

μ max = Maximum strength ratio

μ strength = Ratio of elastic strength demand to yield strength

μΔ,ι = Initial ductility level

ξ eff,i = Effective structural damping at step i of iteration

3104F.7 References.¶

[4.1] American Society of Civil Engineers (ASCE), 2016, ASCE/SEI 7-16 (ASCE/SEI 7), “Minimum Design Loads and Associates Criteria for Buildings and Other Structures,” Reston, VA.

[4.2] American Society of Civil Engineers (ASCE), 2014, ASCE/COPRI 61-14 (ASCE/COPRI 61), “Seismic Design of Piers and Wharves,” Reston, VA.

[4.3] American Society of Civil Engineers (ASCE), 2017, ASCE/SEI 41-17 (ASCE/SEI 41), “Seismic Evalua- tion and Retrofit of Existing Buildings,” Reston, VA.

[4.4] Federal Emergency Management Agency (FEMA), June 2005, FEMA 440, “Improvement of Nonlin- ear Static Seismic Analysis Procedures,” Redwood City, CA.

[4.5] Priestley, M.J.N., Seible, F., Calvi, G.M., 1996, “Seismic Design and Retrofit of Bridges,” John Wiley & Sons, Inc., New York.

[4.6] Kowalsky, M.J., Priestley, M.J.N, MacRae, G.A., 1994, “Displacement-Based Design – A Methodol- ogy for Seismic Design Applied to Single Degree of Freedom Reinforced Concrete Structures,” Report

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Division 5