Section 3103F — STRUCTURAL LOADING CRITERIA

Section 3103F establishes the environmental and operating loads acting on the marine oil terminal (MOT) structures and on moored vessel(s). The analysis procedures are presented in Sections 3104F – 3107F.

3103F.2.1 General. Dead loads shall include the weight of the entire structure, including permanent attachments such as loading arms, pipelines, deck crane, fire monitor tower, gangway structure, vapor control equipment and mooring hardware. Unit weights specified in Section 3103F.2.2 may be used for MOT structures if actual weights are not available.

3103F.2.2 Unit weights. The unit weights in Table 31F-3-1 may be used for both existing and new MOTs.

TABLE 31F-3-1—UNIT WEIGHTS

3103F.2.3 Equipment and piping area loads. The equipment and piping area loads in Table 31F-3-2 may be used, as a minimum, in lieu of detailed as-built data.

TABLE 31F-3-2—EQUIPMENT AND PIPING AREA LOADS

The following vertical live loading shall be considered, where appropriate: uniform loading, truck loading, crane loading and buoyancy. Additionally, MOT specific, nonpermanent equipment shall be identified and used in loading computations.

3103F.4.1 General. Earthquake loads are described in terms of Peak Ground Acceleration (PGA), spectral acceleration and earth- quake magnitude. The required seismic analysis procedures (Tables 31F-4-1 and 31F-4-2) are dependent on the spill classification obtained from Table 31F-1-1.

3103F.4.2 Design earthquake motion parameters. The earthquake ground motion parameters of peak ground acceleration, spec- tral acceleration and earthquake magnitude are modified for site amplification and near fault directivity effects. The resulting values are the Design Peak Ground Acceleration (DPGA), Design Spectral Acceleration (DSA) and Design Earthquake Magnitude (DEM).

For Site Classes A through E (Section 3103F.4.2.1), peak ground and design spectral accelerations shall be obtained from: 1. U.S. Geological Survey (USGS) published data as discussed in Section 3103F.4.2.2, or 2. A site-specific probabilistic seismic hazard analysis (PSHA) as discussed in Section 3103F.4.2.3.

Site-specific PSHA is required for Site Class F.

Unless stated otherwise, the DSA values are for 5 percent damping; values at other levels may be obtained as per Section 3103F.4.2.9.

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The appropriate probability levels associated with DPGA and DSA for different seismic performance levels are provided in Table 31F-4-1. Deterministic earthquake motions, which are used only for comparison to the probabilistic results, are addressed in Section 3103F.4.2.7.

The evaluation of Design Earthquake Magnitude (DEM), is discussed in Section 3103F.4.2.8. This parameter is required when accel- eration time histories (Section 3103F.4.2.10) are addressed or if liquefaction potential (Section 3106F.4) is being evaluated.

3103F.4.2.1 Site classes. The following Site Classes, defined in Section 3106F.2.1, shall be used in developing values of DSA and DPGA:

A, B, C, D, E and F

For Site Class F, a site-specific response analysis is required per Section 3103F.4.2.5.

3103F.4.2.2 Earthquake motions from USGS maps. Earthquake ground motion parameters can be obtained directly from the US Seismic Design Maps tool available at the USGS website) (http://earthquake.usgs.gov) for the site condition(s) appropriate for the MOT site and the selected probability of exceedance. For this purpose, select the ASCE/SEI 41 [3.1] as the design code reference document, and specify the appropriate custom parameters, including but not limited to, location, required Probability of Exceed- ance (in 50 years), and appropriate Site Soil Classification(s) for the MOT site. The USGS tool directly provides the peak ground and spectral accelerations for the selected hazard level and site condition(s).

ect the ASCE/SEI 41 [3.1] as the design code reference_ document, and specify the appropriate custom parameters, including but not limited to, location, required Probability of Exceed- ance (in 50 years), and appropriate Site Soil Classification(s) for the MOT site. The USGS tool directly provides the peak ground and spectral accelerations for the selected hazard level and site condition(s).

The alternative method of obtaining earthquake ground motion parameters, from the most current USGS data for selected hazard level and site condition(s), is permitted. If needed, the data for appropriate probability of exceedance may be obtained using the procedure described in Chapter 1 of FEMA 356 [3.2], and corrected for the MOT site as discussed in Section 3103F.4.2.4 or Section 3103F.4.2.5.

3103F.4.2.3 Earthquake motions from site-specific probabilistic seismic hazard analyses. Site-specific Probabilistic Seismic Hazard Analysis (PSHA) shall use appropriate seismic sources and their characterization, attenuation relationships, probability of exceedance and site soil conditions. Site-specific PSHA shall be conducted by a qualified California registered civil engineer with a California authorization as a geotechnical engineer per Section 3102F.3.4.8.

If site-specific PSHA is used for Site Classes A, B, C, D or E, results from the site-specific PSHA shall be compared with those from the USGS published data as described in Section 3103F.4.2.2. If the two sets of values differ significantly, a justification for using the characterization chosen shall be provided. If DPGA and DSA from site-specific PSHA are less than 80 percent of the values from USGS data, a peer review may be required.

3103F.4.2.4 Simplified evaluation of site amplification effects. When the MOT site class is different from the Site Classes B to C boundary, site amplification effects shall be incorporated in peak ground accelerations and spectral accelerations. This may be accomplished using a simplified method or a site-specific evaluation (Section 3103F.4.2.5).

For a given site class, the following procedure from Chapter 1 of FEMA 356 [3.2] presents a simplified method that may be used to incorporate the site amplification effects for peak ground acceleration and spectral acceleration computed for the Site Classes B and C boundary.

1. Calculate the spectral acceleration values at 0.20 and 1.0 second period:

Equation 3-1 S XS = F a S S

Equation 3-2 S X1 = F v S 1

where :

F a = site coefficient obtained from Table 31F-3-3

F v = site coefficient obtained from Table 31F-3-4

S S = short period (usually at 0.20 seconds) spectral acceleration value (for the boundary of Site Classes B and C) obtained using Section 3103F.4.2.2, or at the period corresponding to the peak in spectral acceleration values when obtained from Section 3103F.4.2.3

S 1 = spectral acceleration value (for the boundary of Site Classes B and C) at 1.0 second period

S XS = spectral acceleration value obtained using the short period S s and factored by Table 31F-3-3 for the site class under consideration.

S X1 = spectral acceleration value obtained using the 1.0 second period S 1 and factored by Table 31F-3-4 for the site class under consideration.

2. Set

Equation 3-3 PGA X = 0.4S XS

where:

PGA X = peak ground acceleration corresponding to the site class under consideration.

When the value of PGA X is less than the peak ground acceleration obtained following Section 3103F.4.2.2 or Section 3103F.4.2.3, an explanation of the results shall be provided.

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3. PGA X , S XS and S X1 constitute three spectral acceleration values for the site class under consideration corresponding to periods of 0, S S (usually 0.2 seconds), and 1.0 second, respectively. 4. The final response spectra, without consideration for near-fault directivity effects, values of S a for the site class under consideration may be obtained using the following equations (for 5 percent critical damping):

For 0 < T < 0.2T 0

Equation 3-4 S a = (S XS )(0.4 + 3T/T 0 )

where:

T = Period corresponding to calculated S a

T 0 = Period at which the constant acceleration and constant velocity regions of the design spectrum intersect

For 0.2T 0 < T < T 0

Equation 3-5 S a = S XS

For T > T 0

Equation 3-6 S a = S X1 /T

where:

Equation 3-7 T 0 = S X1 /S XS

The resulting PGA X is the DPGA. However, the S a shall be modified for near-fault directivity effects, per Section 3103F.4.2.6 to obtain the final DSAs.

TABLE 31F-3-3—VALUES OF F
a

TABLE 31F-3-4—VALUES OF F
v

3103F.4.2.5 Site-specific evaluation of amplification effects. As an alternative to the procedure presented in Section 3103F.4.2.4, a site-specific response analysis may be performed. For Site Class F a site-specific response analysis is required. The analysis shall be either an equivalent linear or nonlinear analysis. Appropriate acceleration time histories as discussed in Section 3103F.4.2.10 shall be used.

In general, an equivalent linear analysis using, for example, SHAKE91 [3.3] is acceptable when the strength and stiffness of soils are unlikely to change significantly during the seismic shaking and the level of shaking is not large. A nonlinear analysis should be used when the strength and/or stiffness of soils could significantly change during the seismic shaking or significant nonlinearity of soils is expected because of high seismic shaking levels.

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The choice of the method used in site response analysis shall be justified considering the expected stress-strain behavior of soils under the shaking level considered in the analysis.

Site-specific site response analysis may be performed using one-dimensional analysis. However, to the extent that MOTs often involve slopes or earth retaining structures, the one-dimensional analysis should be used judiciously. When one-dimensional analysis cannot be justified or is not adequate, two-dimensional equivalent linear or nonlinear response analysis shall be performed. Site- specific response analysis results shall be compared to those based on the simplified method of Section 3103F.4.2.4 for reasonableness.

The peak ground accelerations obtained from this site-specific evaluation are DPGAs and the spectral accelerations are DSAs as long as the near-fault directivity effects addressed in Section 3103F.4.2.6 are appropriately incorporated into the time histories (Section 3103F.4.2.10).

3103F.4.2.6 Directivity effects. When the site is 15 km (9.3 miles) or closer to a seismic source that can significantly affect the site, near-fault directivity effects shall be reflected in the spectral acceleration values and in the deterministic spectral acceleration values of Section 3103F.4.2.7.

Two methods are available for incorporating directivity effects: 1. Directivity effects may be reflected in the spectral acceleration values in a deterministic manner by using well estab- lished procedures such as that described in Somerville, et al. [3.4]. The critical seismic sources and their characterization developed as part of the deterministic ground motion parameters (Section 3103F.4.2.7) should be used to evaluate the directivity effects. The resulting adjustments in spectral acceleration values may be applied in the probabilistic spectral acceleration values developed per Section 3103F.4.2.4 or 3103F.4.2.5. Such adjustment can be independent of the proba- bility levels of spectral accelerations. 2. Directivity effects may be incorporated in the results of site specific PSHA per Section 3103F.4.2.3. In this case, the direc- tivity effects will also depend on the probability level of spectral accelerations.

If spectral accelerations are obtained in this manner, the effects of site amplification using either Section 3103F.4.2.4, 3103F.4.2.5 or an equivalent method (if justified) shall be incorporated.

3103F.4.2.7 Deterministic earthquake motions. Deterministic ground motions from “scenario” earthquakes may be used for comparison purposes. Deterministic peak ground accelerations and spectral accelerations may be obtained using the “Critical Seismic Source” with maximum earthquake magnitude and its closest appropriate distance to the MOT. “Critical Seismic Source” is that which results in the largest computed median peak ground acceleration and spectral acceleration values when appropri- ate attenuation relationships are used. The values obtained from multiple attenuation relationships should be used to calculate the median peak ground acceleration and spectral acceleration values.

For comparison, the values of peak ground accelerations and spectral accelerations may be obtained from the USGS maps, corresponding to the Maximum Considered Earthquake (MCE). In this case, the median values of peak ground acceleration and spectral acceleration values shall be 2/3 (see Section 1.6 of FEMA 356 [3.2]) of the values shown on the USGS maps.

3103F.4.2.8 Design Earthquake Magnitude. The Design Earthquake Magnitude used in developing site-specific acceleration time histories (Section 3103F.4.2.10) or liquefaction assessment (Section 3106F.4) is obtained using either of the following two methods:

1. The design earthquake may be selected as the largest earthquake magnitude associated with the critical seismic source. The distance shall be taken as the closest distance from the source to the site. The resulting design earthquake shall be associated with all DPGA values for the site, irrespective of probability levels. 2. The design earthquake (DEQ) may be obtained for each DPGA or DSA value and associated probability level by determining the corresponding dominant distance and magnitude. These are the values of the distance and magnitude that contribute the most to the mean seismic hazards estimates for the probability of interest. They are usually determined by locating the summits of the 3-D surface of contribution of each small interval of magnitude and distance to the total mean hazards esti- mate. If this 3-D surface shows several modes with approximate weight of more than 20 percent of the total, several DEQs may be considered, and the DEQ leading to the most conservative design parameters shall be used.

3103F.4.2.9 Design Spectral Acceleration for various damping values. Design Spectral Acceleration (DSA) values at damping other than 5 percent shall be obtained by using a procedure given in Chapter 1 of FEMA 356 [3.2], and is denoted as DSA d . The following procedure does not include near-fault directivity effects.

For 0 < T < 0.2 T 0

Equation 3-8 DSA d = S XS [(5/B S -2) T/T 0 + 0.4]

For 0.2 T 0 < T < T 0

Equation 3-9 DSA d = DSA/B S

For T > T 0

Equation 3-10 DSA d = S 1 /(B 1 T)

where:

T = period

T 0 = S X1 /S XS

B S = Coefficient used to adjust the short period spectral response, for the effect of viscous damping.

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B 1 = Coefficient used to adjust one-second period spectral response, for the effect of viscous damping

Values of B S and B 1 are obtained from Table 31F-3-5.

Such a procedure shall incorporate the near-fault directivity effects when the MOT is 15 km (9.3 miles) or closer to a significant seismic source.

TABLE 31F-3-5—VALUES OF B AND B [3.2]
S 1

3103F.4.2.10 Development of acceleration time histories. When acceleration time histories are utilized, target spectral acceler- ation values shall be initially selected corresponding to the DSA values at appropriate probability levels. For each set of target spectral acceleration values corresponding to one probability level, at least three sets of horizontal time histories (one or two hori- zontal acceleration time histories per set) shall be developed.

Initial time histories shall consider magnitude, distance and the type of fault that are reasonably similar to those associated with the conditions contributing most to the probabilistic DSA values. Preferred initial time histories should have their earthquake magnitude and distance to the seismic source similar to the mode-magnitude and mode-distance derived from the PSHA or from appropriate maps. When an adequate number of recorded time histories are not available, acceleration time histories from simu- lations may be used as supplements.

Scaling or adjustments, either in the frequency domain or in the time domain (preferably), prior to generating acceleration time histories should be kept to a minimum. When the target spectral accelerations include near-fault directivity effects (Section 3103F.4.2.6), the initial time histories should exhibit directivity effects.

When three sets of time histories are used in the analysis, the envelope of the spectral acceleration values from each time history shall be equal to or higher than the target spectral accelerations. If the envelope values fall below the target values, adjustments shall be made to ensure that the spectral acceleration envelope is higher than target spectral accelerations. If the envelope is not higher, then a justification shall be provided.

When seven or more sets of time histories are used, the average of the spectral acceleration values from the set of time histories shall be equal or higher than the target spectral acceleration values. If the average values fall below the target values, adjust- ments shall be made to ensure that average values are higher than the target spectral accelerations. If this is not the case, then an explanation for the use of these particular spectral acceleration values shall be provided.

When three sets of time histories are used in the analysis, the maximum value of each response parameter shall be used in the design, evaluation and rehabilitation. When seven or more sets of time histories are used in the analysis, the average value of each response parameter may be used.

3103F.5.1 General. Forces acting on a moored vessel may be generated by wind, waves, current, tidal variations, tsunamis, seiches and hydrodynamic effects of passing vessels. Forces from wind and current acting directly on the MOT structure (not through the vessel in the form of mooring and/ or breasting loads) shall be determined in Section 3103F.7.

The vessel’s moorings shall be strong enough to hold during all expected environmental and passing vessel conditions (see Section 3105F), while adequately accommodating changes in draft, surge, sway, yaw and tide.

3103F.5.2 Wind loads. Wind loads on a vessel, moored at a MOT, shall be determined using procedures described in this section. Wind speed measured at an elevation of 33 feet (10 meters) above the water surface, with duration of 30 seconds shall be used to determine the design wind speed and wind limits for moored vessels. If these conditions are not met, adjustment factors shall be applied per Sections 3103F.5.2.2.

3103F.5.2.1 Design wind speed. For new MOTs, the 25-year return period shall be used to establish the design wind speed for each direc- tion. The design wind speed is the maximum wind speed of 30-second duration used in the mooring analysis (see Section 3105F). The 30- second duration wind speed shall be determined from the annual maximum wind data. Average annual summaries cannot be used. Maximum wind speed data for a minimum of eight directions (45-degree increments) shall be obtained. If other duration wind data is available, it shall be adjusted to a 30-second duration, in accordance with Equation (3- 12).

3103F.5.2.2 Wind limits for moored vessels. Wind loads shall be calculated for each of the load cases identified in Section 3105F.2. Wind velocity limits for moored vessels shall be presented in the Terminal Operating Limits (see Section 3102F.3.6.1 and Figure 31F-2-1) for each of the conditions given below.

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3103F.5.2.2.1 Operational condition. The operational condition is defined as the wind envelope in which a vessel may conduct transfer operations, as determined from the mooring analysis (Section 3105F). Transfer operations shall cease when the wind exceeds the maximum velocity of the envelope.

3103F.5.2.2.2 Survival condition. The survival condition is defined as the state wherein a vessel can remain safely moored at the berth during severe winds; however, loading arms and hoses shall be disconnected (see Sections 3110F.2 and 3110F.3 regarding movement limits of loading arms and hoses, respectfully). The survival condition is the wind zone between the oper- ational condition and the departure condition (defined in Section 3103F.5.2.2). In this wind zone, the vessel must prepare to depart the berth.

at_ the berth during severe winds; however, loading arms and hoses shall be disconnected (see Sections 3110F.2 and 3110F.3 regarding movement limits of loading arms and hoses, respectfully). The survival condition is the wind zone between the oper- ational condition and the departure condition (defined in Section 3103F.5.2.2). In this wind zone, the vessel must prepare to depart the berth.

3103F.5.2.2.3 Departure condition. The departure condition is defined as the wind state above which a vessel can no longer remain safely moored at the berth during severe winds, as determined from the mooring analysis (Section 3105F). For a new MOT, the departure condition threshold is the maximum wind velocity, for a 30-second gust and a 25-year return period, obtained from historical data. If the wind rises above these levels, the vessel must depart the berth.

3103F.5.2.3 Wind speed corrections. Wind speed measured at an elevation of 33 feet (10 meters) above the water surface, with duration of 30 seconds shall be used to determine the design wind speed. If these conditions are not met, the following corrections shall be applied.

The correction for elevation is obtained from the equation:

Equation 3-11

where:

V w = V h [33] 1 7 / [-----] h

V w = wind speed at elevation 33 ft. (10 m.)

V h = wind speed at elevation h

h = elevation above water surface of wind data [feet]

The available wind duration shall be adjusted to a 30-second value, using the following formula:

Equation 3-12

where:

V t = 30 sec = V-- - t c t

V t = 30 sec = wind speed for a 30-second duration

V t = wind speed over a given duration

c t = conversion factor from Figure 31F-3-1

If wind data is available over land only, the following equation shall be used to convert the wind speed from over-land to over- water conditions [3.5]:

Equation 3-13 V w = 1.10 V L

where:

V w = over water wind speed

V L = over land wind speed

3103F.5.2.4 Static wind loads on vessels. The OCIMF MEG3 [3.6] shall be used to determine the wind loads for all tank vessels.

Alternatively, wind loads for any type of vessel may be calculated using the guidelines in Ferritto et al. [3.7].

3103F.5.3 Current loads.

3103F.5.3.1 Design current velocity. Maximum ebb and flood currents, annual river runoffs and controlled releases shall be considered when establishing the design current velocities for both existing and new MOTs.

Local current velocities may be obtained from NOAA [3.8] or other sources, but must be supplemented by site-specific data, if the current velocity is higher than 1.5 knots.

Site-specific data shall be obtained by real time measurements over a one-year period. If this information is not available, a safety factor of 1.25 shall be applied to the best available data until real time measurements are obtained.

If the facility is not in operation during annual river runoffs and controlled releases, the current loads may be adjusted.

Operational dates need to be clearly stated in the definition of the Terminal Operating Limits (see Section 3102F.3.6.1 and Figure 31F-2-1).

3103F.5.3.2 Current velocity adjustment factors. An average current velocity (V c ) shall be used to compute forces and moments. If the current velocity profile is known, the average current velocity can be obtained from the following equation:

Equation 3-14

where:

T

2 2 V c = ( 1 T ⁄ ) ( v c ) ds

o

V c = average current velocity (knots)

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T = draft of vessel

v c = current velocity as a function of depth (knots)

s = water depth measured from the surface

If the velocity profile is not known, the velocity at a known water depth shall be adjusted by the factors provided in Figure 31F- 3-2 to obtain the equivalent average velocity over the draft of the vessel.

FIGURE 31F-3-1 — WIND SPEED CONVERSION FACTOR [3.5]

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FIGURE 31F-3-2 — CURRENT VELOCITY CORRECTION FACTOR (p. 23 [3.6])

3103F.5.3.3 Static current loads. The OCIMF MEG3 [3.6] or the UFC 4-159-03 [3.9] procedures shall be used to determine current loads for moored tank vessels.

3103F.5.3.4 Sea level rise (SLR). All MOTs shall consider the predicted SLR over the remaining life of the terminal, due to subsid- ence or climate change combined with maximum high tide and storm surge. Consideration shall include but not be limited to variation in fender locations, additional berthing loads (deeper draft vessels) and any components near the splash zone.

3103F.5.4 Wave loads. When the significant wave period, T s , is greater than 4 seconds (see Section 3105F.3.1), the transverse wave induced vessel reactions shall be calculated using a simplified dynamic mooring analysis described below.

The horizontal water particle accelerations shall be calculated for the various wave conditions, taken at the mid-depth of the loaded vessel draft. The water particle accelerations shall then be used to calculate the wave excitation forces to determine the static displacement of the vessel. The Froude-Krylov method discussed in Chakrabarti’s Chapter 7 [3.10] may be used to calculate the wave excitation forces, by conservatively approximating the vessel as a rectangular box with dimensions similar to the actual dimensions of the vessel. The horizontal water particle accelerations shall be calculated for the various wave conditions, taken at the mid-depth of the loaded vessel draft. The computed excitation force assumes a 90-degree incidence angle with the longitudinal axis of the vessel, which will result in forces that are significantly greater than the forces that will actually act upon the vessel from quartering seas. A load reduction factor may be used to account for the design wave incidence angle from the longitudinal axis of the ship. The overall excursion of the vessel shall be determined for each of the wave conditions by calculating the dynamic response of the linear spring mass system.

3103F.5.5 Passing vessels. When required in Section 3105F.3, the sway and surge forces, as well as yaw moment, on a moored vessel, due to passing vessels, shall be established considering the following: 1. Ratio of length of moored vessel to length of passing vessel. 2. Distance from moored vessel to passing vessel. 3. Ratio of midship section areas of the moored and passing vessels. 4. Underkeel clearances of the moored and passing vessels. 5. Draft and trim of the moored vessel and draft of the passing vessel. 6. Mooring line tensions.

The passing vessel’s speed should take into consideration the ebb or flood current. Normal operating wind and current conditions can be assumed when calculating forces due to a passing vessel. Either method of Kriebel [3.11] or Wang [3.12] may be used to deter- mine forces on a moored vessel. Kriebel’s recent wave tank study improves on an earlier work of Seelig [3.13].

3103F.5.6 Seiche. The penetration of long period low amplitude waves into a harbor can result in resonant standing wave systems, when the wave forcing frequency coincides with a natural frequency of the harbor. The resonant standing waves can result in large

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surge motions if this frequency is close to the natural frequency of the mooring system. Section 3105F.3.3 prescribes the procedure for the evaluation of these effects.

3103F.5.7 Tsunamis. A tsunami may be generated by an earthquake or a subsea or coastal landslide, which may induce large wave heights and excessive currents. The large wave or surge and the excessive currents are potentially damaging, especially if there is a tank vessel moored alongside the MOT wharf.

Tsunamis can be generated either by a distant or near source. A tsunami generated by a distant source (far field event) may allow operators to have an adequate warning for mitigating the risk by allowing the vessels to depart the MOT and go into deep water. For near-field events, with sources less than 500 miles away, the vessel may not have adequate time to depart. Each MOT shall have a “tsunami plan” describing what actions will be performed, in the event of a distant tsunami.

Recent tsunami studies have been completed for both Southern and Northern California. For the Ports of Los Angeles and Long Beach, one of these recent studies focused on near field tsunamis with predicted return periods of 5,000 to 10,000 years [3.14]. These maximum water levels (run-up) would not normally be used for MOT design. However, because the study also provides actual tidal records from recent distant tsunamis, it should be used for design.

The run-up value for Port Hueneme was obtained from an earlier study by Synolakis et al. [3.15].

Run up-values: Port of Los Angeles and Long Beach = 8 ft.

Port Hueneme = 11 ft.

For the San Francisco Bay, a recent study provides the maximum credible tsunami water levels and current speeds. These results are deterministic and are based on the most severe seismic sources that could reasonably impact MOTs in the San Francisco Bay

[3.16]. Table 31F-3-6 provides values for the marine oil terminal locations within San Francisco Bay. Water levels could be positive or negative and current velocities may vary in direction. In order to determine the maximum run-up at a MOT, the largest values should be added to the mean high tide. Further details are available in [3.16].

Loads from tsunami-induced waves can be calculated for various structural configurations [3.17]. Tsunami wave heights in shal- low water and particle kinematics can also be obtained. Other structural considerations include uplift and debris impact.

TABLE 31F-3-6—TSUNAMI RUN-UP VALUES (ft) AND CURRENT SPEEDS (ft/sec) IN THE SAN FRANCISCO BAY AREA (AFTER [3.16])

3103F.6.1 General. Berthing loads are quantified in terms of transfer of kinetic energy of the vessel into potential energy dissipated by the fender(s). The terms and equations below are based on those in UFC 4-152-01 [3.18] and PIANC [3.19].

Kinetic energy shall be calculated from the following equation:

Equation 3-15

where:

E vessel = 12 [--][ W] ⋅ [--] g [-] [ V] ⋅ [n] 2

E vessel = Berthing energy of vessel [ft-lbs]

W = Total weight of vessel and cargo in pounds [long tons × 2240]

g = Acceleration due to gravity [32.2 ft/sec [2] ]

V n = Berthing velocity normal to the berth [ft/sec]

The following correction factors shall be used to modify the actual energy to be absorbed by the fender system for berthing operations:

Equation 3-16 E fender = F A · C b · C m · E vessel

where:

E fender = Energy to be absorbed by the fender system

F A = Accidental factor accounting for abnormal conditions such as human error, malfunction, adverse environmental conditions or a combination of these factors. For existing berthing systems, F A may be taken as 1.0. For new berthing systems, F A shall be determined in accordance with Section 5-1.5.3 of UFC 4-152-01 [3.18] or PIANC Section 4.2.8 [3.19].

C b = Berthing Coefficient

C m = Effective mass or virtual mass coefficient (see Section 3103F.6.6)

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The berthing coefficient, C b, is given by:

Equation 3-17 C b = C e · C g · C d · C c

where:

C e = Eccentricity Coefficient

C c = Configuration Coefficient

C = Geometric Coefficient g

C d = Deformation Coefficient

These coefficients are defined in Sections 3103F.6.2 through 3103F.6.5.

The approximate displacement of the vessel (when only partially loaded) at impact, DT, can be determined from an extension of an equation from Gaythwaite [3.20]:

Equation 3-18 DT = 1.25 DWT(d actual /d max )

where:

DWT = Dead Weight Tonnage (in long tons)

d actual = Actual arrival draft of the vessel

d max = Maximum loaded vessel draft

The berthing load shall be based on the fender reaction due to the kinetic berthing energy. The structural capacity shall be estab- lished based on allowable concrete, steel or timber properties in the structural components, as defined in Section 3107F.

For fender system selection, Section 3105F.4.5 shall be followed.

3103F.6.2 Eccentricity coefficient (C e ). During the berthing maneuver, when the vessel is not parallel to the berthing line (usually the wharf face), not all the kinetic energy of the vessel will be transmitted to the fenders. Due to the reaction from the fender(s), the vessel will start to rotate around the contact point, thus dissipating part of its energy. Treating the vessel as a rigid rod of negligible width in the analysis of the energy impact on the fenders leads to the equation:

llel to the berthing line (usually the_ wharf face), not all the kinetic energy of the vessel will be transmitted to the fenders. Due to the reaction from the fender(s), the vessel will start to rotate around the contact point, thus dissipating part of its energy. Treating the vessel as a rigid rod of negligible width in the analysis of the energy impact on the fenders leads to the equation:

Equation 3-19

where:

C e = ----------------a 2 k+ 2 k 2

k = Longitudinal radius of gyration of the vessel [ft]

a = Distance between the vessel’s center of gravity and the point of contact on the vessel’s side, projected onto the vessel’s longitudinal axis [ft] 3103F.6.3 Geometric coefficient (C g ). The geometric coefficient, C g , depends upon the geometric configuration of the ship at the point of impact. It varies from 0.85 for an increasing convex curvature to 1.25 for concave curvature. Generally, 0.95 is recommended for the impact point at or beyond the quarter points of the ship, and 1.0 for broadside berthing in which contact is made along the straight side [3.18]. 3103F.6.4 Deformation coefficient (C d ). This accounts for the energy reduction effects due to local deformation of the ships hull and deflection of the whole ship along its longitudinal axis. The energy absorbed by the ship depends on the relative stiffness of the ship and the obstruction. The deformation coefficient varies from 0.9 for a nonresilient fender to nearly 1.0 for a flexible fender. For larger ships on energy-absorbing fender systems, little or no deformation of the ship takes place; therefore, a coefficient of 1.0 is recommended. 3103F.6.5 Configuration coefficient (C c ). This factor accounts for the difference between an open pier or wharf and a solid pier or wharf. In the first case, the movements of the water surrounding the berthing vessel is not (or is hardly) affected by the berth. In the second case, the water between the berthing vessel and the structure introduces a cushion effect that represents an extra force on the vessel away from the berth and reduces the energy to be absorbed by the fender system. For open berth and corners of solid piers, C c = 1.0 For solid piers with parallel approach, C c = 0.8 For berths with different conditions, C c may be interpolated between these values [3.18]. 3103F.6.6 Effective mass or virtual mass coefficient (C m ). In determining the kinetic energy of a berthing vessel, the effective or the virtual mass is the sum of vessel mass and hydrodynamic mass. The hydrodynamic mass does not necessarily vary with the mass of the vessel, but is closely related to the projected area of the vessel at right angles to the direction of motion. Other factors, such as the form of vessel, water depth, berthing velocity and acceleration or deceleration of the vessel, will have some effect on the hydrodynamic mass. Taking into account both model and prototype experiments, the effective or virtual mass coefficient can be estimated as:

Equation 3-20

where:

C m = 1 + 2 ⋅ ----------- [d] [actual] B -

d actual = Actual arrival draft of the vessel

B = Beam of vessel

The value of C m for use in design should be a minimum of 1.5 and need not exceed 2.0 [3.18].

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3103F.6.7 Berthing velocity and angle. The berthing velocity, V n , is influenced by a large number of factors such as environmental conditions of the site (wind, current and wave), method of berthing (with or without tugboat assistance), condition of the vessel during berthing (ballast or fully laden) and human factors (experience of the tugboat captain).

The berthing velocity, normal to berth, shall be in accordance with Table 31F-3-7. Site condition is determined from Table 31F-3-8.

Subject to Division approval, if an existing MOT can demonstrate lower velocities by utilizing velocity monitoring equipment, then such a velocity may be used temporarily until the berthing system is compliant with this Code.

In order to obtain the normal berthing velocity, V n , an approach angle, defined as the angle formed by the fender line and the longitudinal axis of the vessel must be determined. The berthing angles, used to compute the normal berthing velocity, for various vessel sizes are shown in Table 31F-3-9.

TABLE 31F-3-7—BERTHING VELOCITY V (NORMAL TO BERTH)1
n

TABLE 31F-3-8—SITE CONDITIONS

TABLE 31F-3-9—BERTHING ANGLE

3103F.7.1 General. This section provides methods to determine the wind and current loads acting on the structure directly, as opposed to wind and current forces acting on the structure from a moored vessel.

3103F.7.2 Wind loads. Chapter 29 of ASCE/SEI 7 [3.21] shall be used to establish minimum wind loads on the structure. Additional information about wind loads may be obtained from Simiu and Scanlan [3.22].

3103F.7.3 Current loads. The current forces acting on the structure may be established using the current velocities, per Section 3103F.5.3.

As a minimum, each component of the structure shall be analyzed for all applicable load combinations given in Table 31F-3-10 or Table 31F-3-11, depending on component type. For additional load combinations, see UFC 4-152-01 [3.18].

The “vacant condition” is the case wherein there is no vessel at the berth. The “mooring and breasting condition” exists after the vessel is securely tied to the wharf. The “berthing condition” occurs as the vessel impacts the wharf, and the “earthquake condition” assumes no vessel is at the berth, and there is no wind or current forces on the structure.

The use of various load types is discussed below:

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3103F.8.1 Dead load (D). Upper and lower bound values of dead load are applied for the vacant condition to check the maximum moment and shear with minimum axial load.

3103F.8.2 Live load (L). Typically, the live load on MOTs is small and may be neglected for combinations including earthquake loads. However, in some cases, a higher value of live load may be warranted depending on MOT use, and an appropriate value of live load shall be considered for combinations including earthquake loads.

3103F.8.3 Buoyancy load (B). Buoyancy forces shall be considered for any submerged or immersed substructures (including pipe- lines, sumps and structural components).

3103F.8.4 Wind (W) and current (C) on the structure. Wind and currents on the vessel are included in the mooring and breasting condition. The wind and current loads acting on the structure are therefore additional loads that can act simultaneously with the mooring, breasting and/or berthing loads.

3103F.8.5 Earth pressure on the structure (H). The soil pressure on end walls, typically concrete cut-off walls, steel sheet pile walls on wharf type structures and/or piles shall be considered.

3103F.8.6 Mooring line/breasting loads (M). Mooring line and breasting loads can occur simultaneously or individually, depending on the combination of wind and current. Multiple load cases for operating and survival conditions may be required (see Sections 3103F.5.2 and 3105F.2). In addition, loads caused by passing vessels shall be considered for the “mooring and breasting condition.” Refer to Sections 3105F.2 and 3105F.3 for the determination of mooring line and breasting loads.

3103F.8.7 Berthing load (B e ). Berthing is a frequent occurrence, and shall be considered as a normal operating load. No increase in allowable stresses shall be applied for ASD.

3103F.8.8 Earthquake loads (E). Performance based seismic analysis methodology requires that the actual displacement demand be limited to defined strains in concrete, steel and timber. For the deck and pile evaluation, two cases of dead load (upper and lower bound) shall be considered in combination with the seismic load.

TABLE 31F-3-10—LRFD LOAD FACTORS FOR LOAD COMBINATIONS [3.18]

TABLE 31F-3-11—SERVICE OR ASD LOAD FACTORS FOR LOAD COMBINATIONS [3.18]

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Handrails and guardrails shall be designed for 25 plf with a 200-pound minimum concentrated load in any location or direction.

a = Distance between the vessel’s center of gravity and the point of contact on the vessel’s side, projected onto the vessel’s longitudi- nal axis [ft]

A = Site Class A as defined in Table 31F-6-1

B = Beam of vessel

B = Site Class B as defined in Table 31F-6-1

B 1 = Coefficient used to adjust one-second period spectral response, for the effect of viscous damping

B s = Coefficient used to adjust the short period spectral response, for the effect of visous damping.

C = Site Class C as defined in Table 31F-6-1

C b = Berthing Coefficient C c = Configuration Coefficient

C = Geometric Coefficient g C d = Deformation Coefficient C e = Eccentricity Coefficient

C m = Effective mass or virtual mass coefficient

C t = Windspeed conversion factor

D = Site Class D as defined in Table 31F-6-1

DSA = Design Spectral Acceleration

DSA d = DSA values at damping other than 5 percent

DT = Displacement of vessel

DWT = Dead weight tons

d actual = Arrival maximum draft of vessel at berth d max = Maximum vessel draft (in open seas)

E = Site Class E as defined in Table 31F-6-1

E fender = Energy to be absorbed by the fender system

E vessel = Berthing energy of vessel [ft-lbs]

F = Site Class F as defined in Table 31F-6-1

F a , F v = Site coefficients from Tables 31F-3-3 and 31F-3-4, respectively

F A = Accidental factor accounting for abnormal conditions g = Acceleration due to gravity [32.2 ft/sec [2] ]

h = Elevation above water surface [feet]

k = Radius of longitudinal gyration of the vessel [ft]

K = Current velocity correction factor (Fig 31F-3-2)

PGA X = Peak ground acceleration corresponding to the site class under consideration.

s = Water depth measured from the surface

S a = Spectral acceleration S 1 = Spectral acceleration value (for the boundary of Site Classes B and C) at 1.0 second

S S = Spectral acceleration value (for the boundary of Site Classes B and C) at 0.2 seconds

S X1 = Spectral acceleration value at 1.0 second corresponding to the period of S 1 and the site class under consideration

S XS = Spectral acceleration value at 0.2 seconds corresponding to the period of S S and the site class under consideration

T = Draft of vessel (see Figure 31F-3-2)

T = Period [sec]

T 0 = Period at which the constant acceleration and constant velocity regions of the design spectrum intersect

V c = Average current velocity [knots]

v c = Current velocity as a function of depth [knots] V h = Wind speed (knots) at elevation h

V L = Over land wind speed

V n = Berthing velocity normal to the berth [ft/sec]

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v t = Velocity over a given time period

V t = 30sec = Wind speed for a 30 second interval V w = Wind speed at 33-foot (10 m) elevation [knots]

W = Total weight of vessel and cargo inpounds [displacement tonnage × 2240]

WD = Water Depth (Figure 31F-3-2)

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

[3.2] Federal Emergency Management Agency (FEMA), Nov. 2000, FEMA 356, “Prestandard and Commentary for the Seismic Rehabil- itation of Buildings,” Washington, D.C.

[3.3] Idriss, I.M. and Sun, J.I., 1992, “User’s Manual for SHAKE91, A Computer Program for Conducting Equivalent Linear Seismic Response Analyses of Horizontally Layered Soil Deposits,” Center for Geotechnical Modeling, Department of Civil and Environ- mental Engineering, University of California, Davis, CA.

[3.4] Somerville, Paul G., Smith, Nancy F., Graves, Robert W., and Abrahamson, Norman A., 1997, “Modification of Empirical Strong Ground Motion Attenuation Relations to Include the Amplitude and Duration Effects of Rupture Directivity,” Seismological Research Letters, Volume 68, Number 1, pp.199-222.

[3.5] Pile Buck Inc., 1992, “Mooring Systems, A Pile Buck Production,” Jupiter, FL.

[3.6] Oil Companies International Marine Forum (OCIMF), 2008, “Mooring Equipment Guidelines (MEG3),” 3rd ed., London, England.

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

[3.8] National Oceanic and Atmospheric Administration, Contact: National PORTS Program Manager, Center for Operational Ocean- ographic Products and Services, 1305 EW Highway, Silver Spring, MD 20910.

[3.9] Department of Defense, 3 October 2005 (Change 2, 23 June 2016), Unified Facilities Criteria (UFC) 4-159-03, “Design: Moorings,” Washington, D.C.

[3.10] Chakrabarti, S. K., 1987, “Hydrodynamics of Offshore Structures,” Computational Mechanics.

[3.11] Kriebel, David, “Mooring Loads Due to Parallel Passing Ships,” Technical Report TR-6056-OCN, US Naval Academy, 30 Septem- ber 2005.

[3.12] Wang, Shen, August 1975, “Dynamic Effects of Ship Passage on Moored Vessels,” Journal of the Waterways, Harbors and Coastal Engineering Division, Proceedings of the American Society of Civil Engineers, Vol. 101, WW3, Reston, VA.

[3.13] Seelig, William N., 20 November 2001, “Passing Ship Effects on Moored Ships,” Technical Report TR-6027-OCN, Naval Facilities Engineering Service Center, Washington, D.C.

[3.14] Moffatt & Nichol, April 2007, “Tsunami Hazard Assessment for the Ports of Long Beach and Los Angeles – FINAL REPORT,” prepared for the Ports of Long Beach and Los Angeles.

[3.15] Synolakis, C., “Tsunami and Seiche,” Chapter 9 in Earthquake Engineering Handbook, Chen, W., Scawthorn, C. S. and Arros, J. K., editors, 2002, CRC Press, Boca Raton, FL.

[3.16] Borrero, Jose, Dengler, Lori, Uslu, Burak and Synolakis, Costas, June 2006, “Numerical Modeling of Tsunami Effects at Marine Oil Terminals in San Francisco Bay,” Report for the Marine Facilities Division of the California State Lands Commission.

[3.17] Camfield, Frederick E., February 1980, “Tsunami Engineering,” U.S. Army, Corps of Engineers, Coastal Research Center, Special Report No. 6.

[3.18] Department of Defense, 24 January 2017, Unified Facilities Criteria (UFC) 4-152-01, “Design: Piers and Wharves,” Washington, D.C

[3.19] Permanent International Association of Navigation Congresses (PIANC), 2002, “Guidelines for the Design of Fender Systems: 2002,” Brussels.

[3.20] Gaythwaite, John, 2004, “Design of Marine Facilities for the Berthing, Mooring and Repair of Vessels,” American Society of Civil Engineers, Reston, VA.

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

[3.22] Simiu, E. and Scanlan, R., 1978, “Wind Effects on Structures: An Introduction to Wind Engineering,” Wiley-Interscience Publica- tions, New York.

Authority: Sections 8750 through 8760, Public Resources Code.

Reference: Sections 8750, 8751, 8755 and 8757, Public Resources Code.

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Division 4