Section 3104F — SEISMIC ANALYSIS AND STRUCTURAL PERFORMANCE

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 performance criterion to ensure MOT function- ality. 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 trans- fer and storage equipment, critical systems 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 structure. Each MOT structure shall be designated as regular or irregular based on torsional irregularity criteria presented 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 structural segment in such a manner that each segment will move independently during an earthquake.

3104F.2.1 Seismic Performance Criteria. Two levels of seismic performance shall be considered, except for critical 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.

TABLE 31F-4-1—SEISMIC PERFORMANCE CRITERIA1, 2

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 estab- lish component strength and deformation capacities for typical structural materials and components are provided in Section 3107F. Geotechnical considerations are discussed in Section 3106F.

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3104F.2.3 Analytical procedures. The objective of the seismic 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 purpose, the displacement capacity of each element of the structure 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 calculated using the nonlinear static (pushover) procedure. For the nonlinear static (pushover) procedure, the pushover 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 calculation 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 earthquake loading, such as a mini- mum 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.

TABLE 31F-4-2—MINIMUM REQUIRED ANALYTICAL PROCEDURES

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

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

The displacement capacity of a pile from the pushover analysis shall be defined as the displacement that can occur at the top of the pile without exceeding plastic 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 displace- ment 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 trans- verse directions. The piles shall be represented by nonlinear elements that capture the moment-curvature/rotation relationships for components with expected inelastic behavior in accordance with Section 3107F. The effects of connection flex- ibility 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 represent 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 acceptable 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 structures are discussed in the next section.

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FIGURE 31F-4-2 — PILE-DECK CONNECTION MODELING FOR PRESTRESSED CONCRETE PILE (ADAPTED FROM [4.2]

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

A simplified single pile model for a typical timber pile supported structure is shown in Figure 31F-4-3. The pile-deck connec- tions may be assumed to be “pinned.” The lateral bracing can often be ignored if it is in poor condition. These assumptions shall be used for the analysis, unless a detailed condition assessment and lateral analysis indicate that the existing bracing and connections may provide reliable lateral resistance.

cal timber pile supported structure is shown in Figure 31F-4-3. The pile-deck connec-_ tions may be assumed to be “pinned.” The lateral bracing can often be ignored if it is in poor condition. These assumptions shall be used for the analysis, unless a detailed condition 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.

FIGURE 31F-4-3 — SIMPLIFIED SINGLE PILE MODEL OF A TIMBER PILE SUPPORTED STRUCTURE

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 configurations with high or moderate spill classifica- tions. A linear 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, deformation 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:

Equation 4-1 Δ d = S A (T e2 /4π 2 )

where:

T e = effective elastic structural period defined in Equation (4-3) or Equation (4-9)

S A = spectral response acceleration corresponding to T e If T e < T 0 , where T 0 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 displacement demand. In the refined analysis, the target node displacement demand may be computed from the Coefficient 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.

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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 step in the Coefficient Method requires idealization of the pushover curve to calculate the effective elastic lateral stiffness, k e , and effective yield strength, F y , of the structure as shown in Figure 31F-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, k e . The effective elastic lateral stiffness, k e , shall be taken as the secant stiffness calculated at the lateral force equal to 60 percent of the effective yield strength, F y , of the structure. The effective yield strength, F y , shall not be taken as greater than the maximum lateral force at any point along the pushover curve.

The second line segment shall represent the positive post-yield slope ( α 1 k e ) determined by a point (F d , 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. (F d , Δ d ) shall be a point on the actual pushover curve at the calculated target displacement, or at the displacement corresponding to the maximum lateral force, whichever is smaller.

The third line segment shall represent the negative post-yield slope ( α 2 k e ), determined by the point at the end of the positive post-yield slope (F d , 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:

Equation 4-2

where:

2 Δ d = C 1 C 2 S A ------4 [T] π [e] - 2

S A = spectral acceleration of the linear-elastic system at vibration period, which is computed from:

Equation 4-3

where:

T e = 2 π ---- [m] k e

m = seismic mass as defined in Section 3104F.2.3

k e = effective elastic lateral stiffness from idealized pushover

C 1 = modification factor to relate maximum inelastic displacement to displacement calculated for linear elastic response. For period less than 0.2 s, C 1 need not be taken greater than the value at T e = 0.2 s. For period greater than 1.0 s, C 1 = 1.0. For all other periods:

Equation 4-4

where:

C 1 = 1 + μ ------------------------- strength aT e2 – 1

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.

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.

C 2 = 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, C 2 = 1.0. For all other periods:

Equation 4-5

C 2 = 1 + --------8001 [μ] ------------------------- [strength] T e – 1 2

The strength ratio μ strength shall be computed from:

Equation 4-6

where:

μ strength = mS--------F y - A

F y = 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:

Equation 4-7

where:

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

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

Δ y = displacement at effective yield strength

Equation 4-8 h = 1 + 0.15lnT e

α e = effective negative post-yield slope ratio which shall be computed from:

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Equation 4-9 α e = α P-Δ + λ(α 2 - α P-Δ )

where:

α P- Δ , and the maximum negative post-elastic stiffness ratio, α 2 , 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.

FIGURE 31F-4-4 — IDEALIZATION OF PUSHOVER CURVE (ADAPTED FROM [4.3])

3104F.2.3.2.2 Substitute Structure Method. The Substitute Structure Method is based on the procedure 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, F y , and yield displacement, Δ y . 2. Compute the effective elastic lateral stiffness, k e , as the effective yield strength, F y , divided by the yield displacement, Δ y . 3. Compute the structural period in the direction under consideration from:

Equation 4-10

where:

T e = 2 π ---- [m] k e

m = seismic mass as defined in Section 3104F.2.3

k e = effective elastic lateral stiffness in direction under consideration 4. Determine target displacement, Δ d , of the effective linear elastic system from:

Equation 4-11

where:

2 Δ d = S A ------4 [T] π [e] - 2

S A = the 5 percent damped spectral displace-ment corresponding to the linear elastic structural period, T e Select the initial estimate of the displacement demand as Δ d, i = Δ d . 5. The ductility level, μ Δ ,i , is found from Δ d,i / Δ y . Use the appropriate relationship between ductility and damping, for the component undergoing 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 concrete. Note that the idealized pushover curves in Figure 31F-4-4 shall be utilized in Figure 31F-4-5, which illustrates the iterative procedure.

Equation 4-12

where:

ξ eff i, = 0.05 + 1 – 1------------ – α - 1 – α 1 μ Δ, i π [-] [-] [ 1]

α 1 = 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-displacement relationship. 6. Compute the force, F d,i , on the force-deformation relationship associated with the estimated displacement, Δ d,i (see Figure 31F-4-5).

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

Equation 4-13

k eff i, = ------ Δ F d id i,, -

8. Compute the effective period, T eff,i , from:

Equation 4-14

where:

T eff i, = 2 π -------km eff i, -

m = seismic mass as defined in Section 3104F.2.3

9. For the effective structural period, T eff,i , and the effective structural damping, ξ eff,i , compute the spectral acceleration S A (Τ eff,i, ξ eff,i ) from an appropriately damped design acceleration response spectrum. 10. Compute the new estimate of the displacement, Δ d, j , from:

Equation 4-15

Δ d j, = T---------4 2eff i π, 2 S A T ( eff i, ξ, eff i, )

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 displacement, Δ d, i , in step 5 (Figure 31F-4-5).

FIGURE 31F-4-5 — EFFECTIVE STIFFNESS FOR SUBSTITUTE STRUCTURE METHOD

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 displace- ment 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 captured in each of the prin- cipal horizontal directions for the structure. For modal combinations, the Complete Quadratic Combination rule shall be used. Multidirectional 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 nonlinear 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 < T 0 , where T 0 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 amplifica- tion factor. The amplification factor shall be equal to either C 1 × C 2 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.

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FIGURE 31F-4-6 — STIFFNESS FOR LINEAR MODAL ANALYSIS

3104F.2.3.4 Nonlinear dynamic analysis. Nonlinear dynamic time history analysis is optional, and if performed, 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 following 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 adequate.

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

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

The analysis and design requirements described in Section 3104F.2 shall also apply to new MOTs. However, new MOTs shall comply with the seismic performance 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.4.1 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):

Equation 4-16

where:

δ d = δ x + δ y

Equation 4-17 δ x = δ xy + 0.3 δ xx

and

Equation 4-18 δ y = 0.3 δ yx + δ yy

OR

Equation 4-19 δ y = δ yx + 0.3 δ yy

and

Equation 4-20 δ x = 0.3 δ xy + δ xx whichever results in the greater design displacement demand.

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

3104F.4.3 P- Δ Effects. The P- Δ effect (i.e., the additional moment induced by the total vertical load multiplied by the lateral deck deflection) shall be considered unless the following relationship is satisfied (see Figure 31F-4-8):

Equation 4-21

V ≥ 4 [Δ] [d] W [--] [-] [-----] H

where:

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

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, V sk , (approximate upper bound to the shear key force [4.7]) shall be calculated as follows:

Equation 4-22 V sk = 1.5(e/L l )V ΔT

where:

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

L l = segment length

e = eccentricity between the center of rigidity and the center of mass

3104F.4.6 Connections. For an existing wharf, the deteriorated 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 deter- mine 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 capacity (full or partial) of the joint in accordance with Section 3107F.2.7.

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3104F.4.7 Batter piles. Batter piles primarily respond to earthquakes by developing large axial compression or tension forces. Bend- ing 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 displacement capacity, involving vertical piles, before the secondary failure stage develops, shall then be established (see Section 3107F.2.8).

Axial p-z curves shall be modeled. In compression, displacement capacity should consider the effect of the reduction in pile modu- lus 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].

Horizontal nonlinear p-y springs are only applied to batter piles with significant embedment, such as for landside 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 batter piles in a pier type structure.

Nonstructural components, nonbuilding struc- tures 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 fixtures) that may be required to resist the effects of earthquake.

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

Critical systems are nonstructural components, nonbuilding 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) nonstructural 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 piping/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, seis- mic evaluation and design shall be performed 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 compo- nents, nonbuilding structures and building structures, seismic forces (demands) shall be obtained from Section 3104F.5. The seismic adequacy of nonstructural components shall be demonstrated as specified in ASCE/SEI 7 [4.1]. Structures shall be analyzed in accordance with Section 3107F.5. Supports and attachments shall be assessed in accordance with Sections 3107F.7.

of nonstructural compo-_ nents, nonbuilding structures and building structures, seismic forces (demands) shall be obtained from Section 3104F.5. The seismic adequacy of nonstructural components shall be demonstrated as specified in ASCE/SEI 7 [4.1]. Structures shall be analyzed 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 structures 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 charac- teristics (mass and/or stiffness) of the nonstructural components, 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. pipelines) 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 permanently attached to MOT structures (e.g., wharves, trestles, dolphins). The weight of nonstructural compo- nents 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 location of attachment of the nonstructural component or nonbuilding struc- ture 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 consideration of strength, stiffness, ductility and seismic interaction with all other connected components and with the supporting structures or systems, subject to Division approval: 1. Nonstructural component supported by other nonstructural system permanently attached to MOT structure;

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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 associ- ated 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 compo- nent Importance Factor, I p 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 compo- nents and nonbuilding structures 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 nonbuilding structure exceeds 25 percent of the combined mass of the MOT structure plus nonstructural component or nonbuilding structure; 2. Multiple nonstructural components or nonbuilding 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, F p , shall be computed as follows [4.10]:

Equation 4-23

F p = 1.2S---------------------------- xs Ra pp I p W - p

0.3S xs I p W p ≤ F p ≤ 1.6S xs I p W p

where:

S xs = spectral acceleration in Section 3103F.4.2.4 or Section 3103F.4.2.5 a p = amplification factor for nonstructural component or nonbuilding structure (Table 31F-4-3) I p = importance factor for nonstructural component or nonbuilding structure (Table 31F-4-4) W p = weight of the nonstructural component or nonbuilding structure R p = 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, F p , may be computed from [4.10]:

Equation 4-24

F p = a------------------------ p S A RI pp A x W - p

0.3S xs I p W p ≤ F p ≤ 1.6S xs I p W p

where:

S A = spectral acceleration in Section 3103F.4.2.4 or Section 3103F.4.2.5, at the period equal to the elastic funda- mental period of the MOT structure, T, in direction under consideration

A x = torsional amplification factor given by:

Equation 4-25 A x =

---------------1.2ΔΔ mavg - 2

1 ≤ A x ≤ 3

where:

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) The horizontal seismic force, F p , in the direction under consideration shall be applied at the center of gravity and distributed relative to the mass distribution of the nonstructural component or nonbuilding structure.

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MARINE OIL TERMINALS

The horizontal seismic force, F p , shall be applied independently in at least two orthogonal horizontal directions in combina- tion with service or operating loads associated with the nonstructural component or nonbuilding structure, as appropriate. For vertically cantilevered systems, however, F p shall be assumed to act in any horizontal direction. The concurrent vertical seismic force, F v , shall be applied at the center of gravity and distributed relative to the mass distri- bution of the nonstructural component or nonbuilding structure, as follows:

Equation 4-26 F v = ±0.2S xs W p

TABLE 31F-4-3—AMPLIFICATION FACTORS FOR NONSTRUCTURAL COMPONENTS AND NONBUILDING STRUCTURES

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

TABLE 31F-4-4—IMPORTANCE FACTORS FOR NONSTRUCTURAL COMPONENTS AND NONBUILDING STRUCTURES

TABLE 31F-4-5—RESPONSE MODIFICATION FACTORS FOR NONSTRUCTURAL COMPONENTS AND NONBUILDING STRUCTURES

31F-44 2025 CALIFORNIA BUILDING CODE

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

MARINE OIL TERMINALS

TABLE 31F-4-5—RESPONSE MODIFICATION FACTORS FOR NONSTRUCTURAL COMPONENTS AND NONBUILDING STRUCTURES—continued

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 Procedure (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 modifi- cation 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 seismic load shall be computed using the procedures in ASCE/SEI 7 [4.1], except that Level 2 design earthquake motion parameters defined in Section