This paper provides a case study involving the waterfront redevelopment of a decommissioned US Navy facility with a 1940s wharf repurposed as a pedestrian promenade. The conversion to a publicly-accessible structure triggered special seismic performance criteria and the application of multiple seismic standards from different regulators. The seismic design had to address strong ground motions, weak marine soils and large ground deformations, aging infrastructure, deep soil mixing (DSM) ground improvements, and late major project changes requiring reconsideration of the kinematic inertial (K+I) load combinations on the pile-supported wharf. The design team changed from a conservative 100%/100% combination to an approach considering the time history analysis results from the DSM design analyses, using relative phasing of the kinematic and inertial responses to generate K+I combinations for the governing load cases. This paper describes the basis and details for the final approach.

The Port of Alaska in Anchorage (Port) has embarked on a multiphase modernization program that includes the development of a new petroleum and cement terminal (PCT) berth. The berth consists of a pile-supported trestle that connects to a platform located offshore in the Knik Arm waterway (Figure 1). The terminal is located in a dynamic marine environment with numerous design challenges, including tidal fluctuations of as much as 40 ft, design ground motions associated with a magnitude Mw 9.3 subduction zone earthquake, weak foundation soils, and shoreline conditions that are vulnerable to large-scale seismic displacements. Geotechnical input to the seismic design of the pile-supported terminal required synthesis of extensive in-situ and cyclic laboratory testing data, nonlinear deformation analysis (NDA), and layout of a deep soil mixing (DSM) ground improvement zone for mitigation of seismically induced slope displacements.

Damages to port facilities supported by anchored sheetpile walls are commonly observed at moderate to high seismic load levels. Predicting the extent of seismic deformations of anchored sheetpile walls is a necessary step in the performance-based design; however, the lack of straightforward and practical models poses great challenges for this prediction. In this study, a hybrid framework is proposed for developing practical empirical models for predicting seismic deformations of anchored sheetpile walls. First, a 2-D numerical model is calibrated with field case history data. Next, a series of numerical simulations are undertaken to characterize the relationship between the responses (i.e., seismic deformations of anchored sheetpile walls) and the inputs (i.e., variables that affect the responses). The model bias factor and coefficients (i.e., model parameters) in the derived coarse solution model are then characterized probabilistically, and further updated and refined with the collected database of field cases and/or experimental data. Finally, this hybrid framework is demonstrated through the development of data-driven empirical models for predicting seismic deformations of anchored sheetpile walls. The results show that the proposed framework is effective in developing a data-driven empirical model, and the obtained model can be easily updated with additional case history data, as needed, to improve the accuracy.

Nevada is a large western state in theUnited States with a seismic hazard that ranges from moderate to high, depending on location. This article identifies priorities to improve estimates of the seismic hazard in the most urbanized parts of the state, specifically the Reno-Carson City urban area of western Nevada and the Las Vegas urban region of southern Nevada. Collaborative task forces are needed to efficiently realize these priorities. For the Reno-Carson City region in western Nevada, the seismic hazard is high because of strain distributed across several active faults, including normal faults that dip beneath parts of the urban areas. The subsurface geometry and possible connections of these faults remain to be determined. The present large uncertainty in estimates of the slip rates can be reduced by future geological and geodetic studies, including trenching at more than one site per fault and increasing the density of geodetic stations to include multiple stations in the mountain ranges between faults to detect rotations. Adjustments to the ground-motion models for the regional properties of western and southern Nevada could reduce ground-motion uncertainties. Ground-motion simulation research needs an improved 3D velocity model. The seismic hazard in Las Vegas is lower than in Reno. An expanded geodetic network and continued geological studies of the active faults are needed. Uncertainties in the geometry and activity of the Frenchman Mountain and Eglington faults particularly introduce significant uncertainties into the seismic hazard in the Las Vegas basin. The more distant Garlock and Death Valley faults in eastern California impact the hazard in Las Vegas because the Las Vegas basin amplifies long-period ground motion and prolongs its duration, so reliable simulations from these sources are needed.

This paper focuses on the seismic performance of a pile-supported pier structure considering the potential for large-scale, earthquake-induced, slope deformations controlled by a layer of soft clay. The assessment incorporates the strain-dependent shearing resistance of the soft clay from moderate strains associated with peak dynamic strength, to intermediate strains at residual strength, and ultimately large strains at fully-remolded strength. Primary challenges for the project included drilling through an existing rock fill to obtain high-quality samples of the underlying soft clay for laboratory characterization of the static, cyclic, and post-cyclic stress strain behavior of the clay. This paper underscores the importance of the laboratory testing for evaluation of the structural performance of a pile-supported pier structure impacted by permanent foundation movements during earthquakes. Structural aspects of the assessment are presented by Soderberg and Liu as part of the Proceedings of the Ports '19 Conference.

Results of a centrifuge test on a pile-supported wharf were used to investigate the time-, depth-, and row-dependent nature of kinematic and inertial loading on wharf piles in sloping rockfill. P-y models were calibrated against recorded bending moments in different piles and different depths. It was found that full kinematic demands and full superstructure inertia should be combined to estimate bending moments at pile head and shallow depths (less than 10 diameters below the ground surface). On the contrary, it was found that applying full kinematic demands alone was adequate to estimate pile bending moments at large depths (greater than 10 diameters deep).

A permitting-level design was conducted for a liquefied natural gas (LNG) facility, proposed on the northwest Oregon coast. The permitting-level design required the structure to operate safely during the design level ground shaking from an earthquake on the underlying Cascadia Subduction Zone interface fault. The site is underlain by 350 feet (107 meters) of predominantly soft non-plastic silt and medium-dense to dense sand layers. The design of the LNG facility, as well as the foundation system, required an estimation of the liquefaction potential and cyclic performance of the silt and sand soil layers, however, there is limited published information for evaluating the cyclic behavior of deep soil deposits. This paper summarizes the results of (a) an extensive site investigation and cyclic soil laboratory testing conducted to develop cyclic parameters and (b) nonlinear effective-stress site-response analyses using the computer program D-MOD2000. The analyses were conducted to evaluate the cyclic performance of the soil layers for use in designing the foundation system. The results of the cyclic testing and lessons learned during the numerical modeling are presented.

The long-term use of instrumentation and sensor technology for monitoring the condition and performance of waterfront structures has become a topic of increased focus in practice. This is due in part to the adoption within portions of the ports community of engineering concepts such as performance-based design and life-cycle management, which necessitate that the condition of the wharves and ancillary structures as well as foundation components are well characterized throughout their service life. Many of the integral components of waterfront structures are submerged and/or embedded in soil often making it difficult, if not impossible, to directly and frequently inspect. For this reason the use of geotechnical and structural instrumentation has been implemented on several recent port projects in order to monitor the performance of structures above and below grade. The specific objectives of these instrumentation programs have been to obtain field data for one or more of the following issues; (a) construction-induced ground deformations and pile alignment, (b) post-construction base line data on as-built conditions, (c) operational performance characteristics during routine loading conditions, (d) performance data in the event of extreme loading due to natural hazards (hurricane storm surge or flood, earthquake, tsunami), and (e) time-dependent issues such as corrosion impacts, ground deformations due to soil consolidation or creep near slopes, near shore scour or sedimentation, and the performance of aging infrastructure. This paper provides an overview of the needs, objectives, benefits, and impediments to the implementation of instrumentation programs at ports. This supplements the companion paper in these proceedings prepared by the ASCE-TCLEE Ports Lifelines Committee on the monograph Instrumentation for Monitoring the Performance of Port and Coastal Infrastructure that has been recently published by ASCE.

Five pile-supported wharf models were dynamically tested in a large-scale geotechnical centrifuge at UC Davis, California. Models representing pile-supported wharf configurations common in the United States were subjected to recorded acceleration time histories. Model variations included single-lift, multi-lift, and cut-slope rock dike configurations with foundation layers of loose liquefiable sand, marine clay, or dense sand, or a combination thereof. In addition, zones of soil were placed to model soil improvement. Structural elements representing pile-supported wharf geometries were placed within the models; some models included all vertical piles, while two of the models included batter piles. In addition, single piles were placed in two of the models and subjected to static cyclic lateral load tests. All models were extensively instrumented with nearly 100 instruments recording accelerations, pore pressures, linear deformations, and pile strains. This paper summarizes the design, construction, and testing of these complex models, and includes a brief summary of the results and recommendations for future modeling.

In light of the inherent variability and soft nature of soil deposits in the marine environment, it is common geotechnical engineering practice to use conservative soil property values for analysis and design recommendations. The shear strength and modulus values often recommended are generally smaller than best estimate or mean values. The connotation that lower bound values are conservative can be related to the use of limit-equilibrium analyses for stability applications involving foundations, earth retention systems, and slopes. Current use of numerical models for performance-based design at ports has demonstrated, however, that the assumption that lower bound soil properties yield conservative results is not always accurate. This paper presents two examples in which lower values of strength and/or modulus resulted in unconservative estimates of performance for the design of port waterfront structures.

The widespread application of sensors and instrumentation systems at port facilities has substantially lagged behind that of other sectors of civil infrastructure due to a combination of factors that include; lack of external funding sources for geotechnical and structural instrumentation, difficulties in coordinating the installation with construction schedules, instrument longevity and maintenance concerns in the marine environment, location and access considerations in active terminals, and resources for data acquisition and archiving efforts. Most of these issues have been overcome for buildings, bridges and dams where the application of advanced sensors with real-time data processing and visualization software yield direct benefits to engineering evaluation of system performance under operating loads and extreme natural hazards, maintenance, and life-cycle management. Given the tremendous benefits of performance monitoring progress is being made at ports and marine oil terminals in California where instrumentation has recently been deployed to obtain data on near shore currents, vessel impact and mooring loads, ground and wharf foundation deformations, and the seismic response of waterfront structures. The lessons learned during these recent projects will benefit current planning and installation efforts at other ports. This paper summarizes field applications for instrumentation at ports and related civil infrastructure, and demonstrates the advances made in seismic performance evaluation of port facilities that have been facilitated by field monitoring. This paper supplements the companion paper in these proceedings prepared by the ASCE-TCLEE Ports Lifelines Committee on the monograph Instrumentation for Monitoring the Performance of Port and Coastal Infrastructure. The monograph was prepared to highlight recent experience with instrumentation programs for major port projects in the United States.

The utilization of performance-based seismic design concepts at major ports often necessitates a reliance on numerical models for simulating the dynamic soil-foundation-structure interaction of piers and wharves. Construction and siting of pile supported wharves, which comprise the most common type of waterfront structure in cargo handling portions of major U.S. ports, includes pile embedment in submarine slopes routinely comprised of rock-fill underlain by weak marine soils. Field observations at ports around the world lead to the general conclusion that incipient, permanent slope deformations can be expected at ground motion levels as low as 0.15g, well below design levels in many regions. In light of the resources required to prevent slope deformation small permanent slope deformations are considered acceptable for most waterfront projects. The allowance in seismic performance criteria of limited, yet permanent, deformations of the slope and piles makes the design of pile foundations for port waterfront structures rather unique. Seismic analysis requires that both the kinematic and inertial aspects of the seismic loading of pile foundations are evaluated in a coupled manner. This paper addresses the seismic analysis of pile supported wharves; however, aspects of this work can be readily applied to other coastal infrastructure. In order to identify the strengths and limitations of practice-oriented methods for evaluating the seismic performance of pile supported wharves centrifuge modeling was employed to supplement field case history data for validation of two deformation-based analysis methods; a numerical 2D nonlinear, effective stress model, and a simple, straightforward procedure based on the rigid, sliding block concept. Modeling results demonstrate that the practice-oriented, sliding block model can yield suitably accurate deformation estimates, provided that the analysis method accounts for excess pore pressure generation and the stabilizing effect of the piles in the slope. The numerical procedure, which utilized a simplified stress-based pore pressure generation constitutive model, resulted in reliable deformation patterns and acceleration estimates, and pore pressures were somewhat well reproduced; however the maximum dynamic and residual moments in the piles were not well replicated. Shortcomings of the numerical geomechanical modeling are addressed. The limitations notwithstanding, the numerical procedure is advantageous compared to the sliding block method, as the pattern of soil deformation and pile curvature are more accurately simulated, a more complete picture of soil-foundation-structure interaction is provided, and the coupled performance of the waterfront slope and wharf is more clearly demonstrated.

Recent experience has demonstrated that waterfront structures are highly susceptible to earthquake-induced damage. In the western United States, port waterfront structures are commonly constructed using pile-supported wharves in combination with rock dike structures retaining hydraulically placed fills. Many ports use batter piles to limit deflections from lateral loads, such as ship berthing and seismic loads. Extensive earthquake-induced damage to batter piles has been observed at several ports worldwide. Consequently, batter piles are now used cautiously in the design of new wharves in seismically active regions even though many wharves with batter piles have performed adequately. They have also been used as part of the unique “structural fuse” concept that has been adopted on major projects in the western United States. The continued use of batter piles combined with the significant number of existing wharves supported with batter piles creates the need for a better understanding of their seismic performance. In order to augment the limited number of instrumented earthquake case studies for modern wharves and evaluate the performance of the soil-foundation-structure system, a series of large-scale centrifuge models have been constructed and tested with typical pile-supported wharf configurations. This paper presents the results of the final two models where batter piles were incorporated. Tests were carried out with and without the batter piles attached for each model at identical input accelerations. To the authors’ knowledge, the tests provide the first recording and quantification of seismic force distribution for pile-supported wharf structures with batter piles. This paper summarizes 1) quantification of seismic lateral loads on vertical and batter piles, 2) pile shear and moment data with emphasis on the wharf deck connection, 3) embankment displacements with comments regarding their influence on pile loading.

In engineering practice there is ongoing debate concerning the limitations of 3D structural modeling of wharves and piers for seismic analysis. This paper presents the results of an investigation of the seismic response of Berth 24/25 at the Port of Oakland, California. The primary objectives of this project were to evaluate strong motion data from an instrumentation array at Berth 24/25 and to identify the limitations inherent in capturing the complete dynamic character, including soil structure interaction, of a pier or wharf with a structural model. The numerical model was validated using ground motions recorded during the 1989 Loma Prieta earthquake with a twelve channel array placed on and adjacent to the structure. Through a series of simulations, the effect of variation of selected model parameters has been evaluated by comparison to recorded wharf motions. Analyses using design level input motions were performed to evaluate applicability of the full 3D model. The project is expected to serve the professional engineering community by providing guidance in selecting appropriate techniques for seismic analysis and subsequent upgrade of existing port facilities.

Piles are often installed in sloping rock fill for the construction of marginal wharves. Though much information is available on the lateral performance of piles in sloping sand, silt, and clay profiles, only limited information is available on the lateral performance of piles in sloping or horizontal rock fill. This paper summarizes the results of a recent research effort using centrifuge and numerical models, as well as field data, to better understand the performance of piles at marginal wharves. The results indicate that modifications to current analysis methods are required to accurately model the lateral behavior of piles in sloping rock fill. Modifications are required to account for the sloping profile, resulting in reduced p-y curve ultimate strength in the downslope direction. In addition, if the diameter of the rock fill is approximately the same as the pile diameter, the ultimate strength of the p-y curve in both the upslope and downslope directions needs to be increased to account for the discrete particle interaction between the piles and rock fill.

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