Pile-supported Wharf Structures Research Articles

Interaction characteristics between the large ship-rubber fenders-wharf structure in deep-water considering the flexibility of the wharf structure

High pile-supported wharf structures in offshore deep water have significant flexibility due to long free ends and large slenderness ratios of the pile bodies, resulting in substantial deformation of the pile body under kinds of loads. In the design of this new type of wharves, it is expected to consider the characteristic of elastic deformation of pile body absorbing a portion of the ship impact energy reasonably. However, the existing calculation method still adopts the theoretical formulas of traditional wharf structures, failure to incorporate this advanced design concept fully. In order to solve this, firstly, a comprehensive three-dimensional numerical simulation model encompassing large ship, rubber fenders and wharf structure, was developed using Ansys/LS-Dyna, and the calculation model was validated against the existing research results. Subsequently, dynamic response characteristics of wharf structures during the normal berthing of ships were examined meticulously, and the variations in absorption energy and reaction forces of rubber fenders and wharf structures were analyzed systematically. And then the analysis results were compared with previous research, the limitations of the existing design code for wharf structures were discussed as well. Finally, the findings demonstrate that peak values of absorption energy and energy transfer times increase with the increase of ship loading capacities. And the elastic deformation of the wharf structure indeed absorbs considerable partial of the impact energy effectively, with about 30 % for conditions in this study, leading to lower impact forces acted on the wharf structure. Moreover, the maximum pile top displacement of the wharf structure is also smaller than that reported in the existing literature in the same load condition, indicating that considering the structural flexibility in the design of this new type of wharf structure is more in line with reality, and it is more reasonable and economical as well.

Seismic response analysis of pile-supported wharf under three types of near-fault ground motion

Near-fault pulse-like ground motions exhibit distinct properties, such as forward-directivity and fling-step effects. It is necessary to study the seismic response characteristics of the pile-supported wharf (PSW) under different near-fault ground motions. In this study, thirty near-fault ground motions were utilized as input motions, including forward-directivity, fling-step and non-pulse ground motions. A three-dimensional (3D) nonlinear finite element (FE) model was created to simulate the PSW structure. The seismic response (displacement, bending moment, and acceleration) of the PSW structure under 30 ground motions with peak ground acceleration (PGA), effective peak acceleration (EPA), improved effective peak acceleration (IEPA), peak ground velocity (PGV) and effective peak velocity (EPV) scaling were calculated and compared. The simulation results demonstrate that the PSW structure responds more significantly under two types of near-fault pulse-like ground motion. For near-fault pulse-like ground motions, PGV scaling is better for studying displacement/bending moment response of PSW structure than others. EPA scaling is suitable for studying the acceleration response of PSW structure.

Numerical modeling of a pile-supported wharf subjected to liquefaction-induced lateral ground deformations

Fully-coupled nonlinear dynamic analysis is increasingly used for assessing the seismic performance of pile-supported wharf structures subjected to liquefaction-induced lateral ground deformations. Several numerical challenges exist for analysis of this highly nonlinear soil-structure interaction, which require robust, yet practical, solutions that are validated with experimental data. This study presents a numerical model of a pile-supported wharf and evaluates the applicability of a soil constitutive model, and modeling assumptions and methods by using recorded data from a well-instrumented, large-scale centrifuge test. The objectives of this study include: (a) evaluating the performance of a recently developed pressure-dependent multi-yield surface constitutive soil model (PDMY03) to simulate the behavior of a liquefiable sand (b) assessing the effectiveness of a soil–pile interaction modeling approach in capturing the kinematic displacement demands on piles from a laterally spreading ground, and (c) evaluating the effectiveness and limitations of the 2D numerical model in approximating the 3D behavior of a wharf structure supported by multiple rows of piles, including the dynamic response of the centrifuge container. The implications of these assumptions and lessons learned from this study provide guidance for researcher modelers and practitioners for numerical modeling of similar soil–structure systems.

Seismic Vulnerability Assessment of Critical Port Infrastructure Components by Modelling the Soil-Wharf-Crane Interaction

This paper aims to investigate the seismic vulnerability of key port infrastructure components by using the outcomes of advanced numerical analysis. For the first time, to the best knowledge of the authors, a pile-supported wharf structure, the soil deposits where the wharf lies, and a crane typically operating on the wharf are numerically modelled as a combined system. The starting point for building the numerical model is the main components of strategic facilities at the port of Gioia Tauro (Italy), which is a strategic hub for container traffic located in one of the most seismically active regions of the Mediterranean Sea. Based on the results obtained from two-dimensional (2D) dynamic analyses, fragility curves were developed for single port components and the wharf-crane-soil system. A scenario-based seismic damage assessment was then exemplified to compare the predictions resulting from the fragility model presented in this work with the relevant data available in the literature. It turns out that, besides some inevitable variations, expected damage percentages were in general agreement. As the main contribution of this work, derived fragility curves might be adopted as an effective tool for rapid evaluation of the seismic performance of port components during the development of strategies for risk mitigation and also the emergency management in case of an earthquake.

Seismic vulnerability analysis of vertical pile-supported wharf structure

In order to study the seismic vulnerability of pile-supported wharf structure, taking a vertical pile-supported wharf as the research object and considering the influence of the site, seismic spectrum characteristics and the uncertainty of ground motion intensity, we establish a dynamic nonlinear numerical model of structure-foundation soil coupling of vertical pile-supported wharf by using the geotechnical finite element software of Midas GTS NX. Selecting the maximum strain of pile foundation in soil as the damage index, we obtain the seismic vulnerability curves and the corresponding damage state probability based on the the incremental dynamic analysis method. The analysis results show that when peak ground acceleration is less than 0.80<italic>g</italic>, the wharf structure is mainly in mild damage state or moderate damage state, otherwise the probability of serious damage basically exceeds 50% and the structure will lose operational capacity. Based on the vulnerability analysis of pile foundation damage in foundation soil, the influence of earthquake on the vertical pile-supported wharf is described from macroscopic and quantitative point of view, which can provide reference for seismic design and disaster prevention prediction of vertical pile-supported wharf.

Dynamic behavior of pile-supported wharves by slope failure during earthquake via centrifuge tests

The effects of earthquakes on pile-supported wharves include damage to piles by inertial forces acting on the superstructure, and damage caused by horizontal displacement of retaining walls. Piles can also be damaged through kinematic forces generated by slope failure. Such forces are significant but it is difficult to clearly explain pile damage during slope failure since the inertial force of superstructure and the kinematic force by slope failure can occur simultaneously during an earthquake. In this study, dynamic centrifuge model tests were performed to evaluate the effect of the kinematic force of the ground due to slope failure during earthquake on the behavior of a pile-supported wharf structure. Experimental results indicate that the slope failure in the inclined-ground model caused the deck plate acceleration and pile moment to be up to 24% and 31% respectively greater than those in the horizontal-ground model due to the kinematic force of the ground.

Seismic Site Characterization and Dynamic Analysis of Pile-Supported Wharf Structure

India being a large subcontinent is prone to traumatic earthquakes causing remarkable destruction to property, life and hindering the development of urban areas. Since past few years, the issue of earthquakes has been mentioned by many researchers and agencies. Hence, dynamic site characterization is considered as a primary step in any seismic zonation process. In this research paper, an effort has been made to dynamic site characterization of the city of Vishakhapatnam (India) along with dynamic analysis of a pile-supported wharf structure located in the study area. Dynamic site characterization and response studies that are a subset of micro zoning process provide us with most important outcomes for the hazard estimation process of a particular region. Site characterization has been carried out for the city of Vishakhapatnam, Andhra Pradesh (India), using geotechnical, geological and seismotectonic data. Further, a pile-supported wharf structure is considered in Vishakhapatnam port to study the dynamic behavior and performance analysis of the structure under local site conditions. Wharfs are the structures that are constructed parallel to the shore for mooring of ships. Any damage due to an earthquake to wharfs and berths may lead to inefficiency in port operations. Seismic performance analysis of pile-supported wharf is the most neglected and unaddressed part in codal provisions of many of the countries. Seismic vulnerability analysis also provides a framework to assess the both the performance of the system and economic issues on a whole.

The influence of the soil constitutive models on the seismic analysis of pile-supported wharf structures with batter piles in cut-slope rock dike

Abstract In coastal regions, earthquakes caused severe damage to marine structures. Many researchers have conducted numerical investigations in order to understand the dynamic behavior of these structures. The most frequently used model in numerical calculations of soil is the linear-elastic perfectly plastic model with a Mohr-Coulomb failure criterion (MC model). It is recommended to use this model to represent a first-order approximation of soil behavior. Therefore, it is necessary to accommodate soil constitutive models for the specific geotechnical problems. In this paper, three soil constitutive models with different accuracy were applied by using the two-dimensional finite element software PLAXIS to study the behavior of pile-supported wharf embedded in rock dike, under the 1989 Loma Prieta earthquake. These models are: a linear-elastic perfectly plastic model (MC model), an elastoplastic model with isotropic hardening (HS model), and the Hardening Soil model with an extension to the small-strain stiffness (HSS model). A typical pile-supported wharf structure with batter piles from the western United States ports was selected to perform the study. The wharf included cut-slope (sliver) rock dike configuration, which is constituted by a thin layer of rockfill overlaid by a slope of loose sand. The foundation soil and the backfill soil behind the wharf were all dense sand. The soil parameters used in the study were calibrated in numerical soil element tests (Oedometer and Triaxial tests). The wharf displacement and pore pressure results obtained using models with different accuracy were compared to the numerical results of Heidary-Torkamani et al.[28] It was found that the Hardening Soil model with small-strain stiffness (HSS model) gives clearly better results than the MC and HS models. Afterwards, the pile displacements in sloping rockfill were analyzed. The displacement time histories of the rock dike at the top and at the toe were also exposed. It can be noted that during the earthquake there was a significant lateral ground displacement at the upper part of the embankment due to the liquefaction of loose sand. This movement caused displacement at the dike top greater than its displacement at the toe. Consequently, the behavior of the wharf was affected and the pile displacements were important, specially the piles closest to the dike top.

Seismic fragility assessment of large-scale pile-supported wharf structures considering soil-pile interaction

Seismic fragility curves are recognized as a useful tool for seismic performance assessment of pile-supported wharf structure (PSWS) exposed to seismic hazards. These curves quantify the probability of structural vulnerability against given ground motion parameters. Soil-pile interaction (SPI) is found to have a significant impact on seismic performance of pile-supported structures. In this study, in order to better understand the SPI effect, the seismic fragility of a large-scale PSWS located at the Port of Los Angeles Berth 100, USA, is fully investigated with and without considering SPI. Herein, the pushover analysis scheme is used for inferring the bound limits of seismic demands of this large-scale PSWS. Specifically, the purpose of pushover analysis is twofold: to identify which pile of the PSWS most likely suffers from seismic failure; and to determine the bound limits of seismic demands for estimation of fragility curves using the identified pile. A collection of ground motions with low and high moment magnitudes as well as small and large fault distances are selected for nonlinear time history analysis. The seismic demand models can be readily estimated from the data set of the intensity measure-seismic demand pairs by classical regression fitting. A comparison of fragility curves with and without SPI shows that SPI significantly influences the seismic fragility of the PSWS. For distinct damage states, the effect of SPI on the seismic fragilities of different piles can be totally different.

Analysis of seismic damage mitigation for a pile-supported wharf structure

This paper evaluates earthquake-induced permanent ground deformations and the structural response of a typical pile-supported wharf structure built over loose granular fill. Using numerical simulations for a suite of 55 reference seismic ground motions, we investigate the effectiveness of an array of PV drains installed behind the pile-supported deck in mitigating structural damage associated with deformations of the fill. Numerical analyses use a sub-structuring approach in which the ‘free-field’ 2D coupled deformations, and seepage within the soil fill are simulated using the u-p formulation in the OpenSees finite element framework. The complex non-linear and inelastic stress-strain properties of the sand under cyclic loading are represented using the Dafalias-Manzari (DM2004) bounding surface plasticity model, while customized 1-D finite elements are used to describe flow in the PV drains. The resulting ground deformations and excess pore water pressures are treated as boundary conditions in modeling the response of the wharf structure, through macro-elements that represent local pile-soil interactions (after Varun and Assimaki, 2012 [1]). We discuss the associated soil behavior and show how lateral spreading is mitigated by the proposed PV drain array. This mitigation system limits the potential damage to the pile-deck connections enabling much simpler structural retrofit for the wharf.

Efficient Uncertainty Quantification of Wharf Structures under Seismic Scenarios Using Gaussian Process Surrogate Model

ABSTRACT The scenario-based seismic assessment approach is illustrated within a large-scale pile-supported wharf structure (PSWS). As nonlinear seismic response analysis is computationally expensive, a novel and efficient method is developed to improve and update the traditional simulation methods. Herein, the Gaussian Process (GP) surrogate model is proposed to replace the time-consuming FE model of PSWS, which makes the quantification of uncertainty in seismic response of a large-scale PSWS resulting from structural parameter uncertainty more computationally-efficient. The feasibility of the proposed approach in seismic assessment of a large-scale PSWS under a given seismic scenario is verified by using Monte Carlo simulation.

BEHAVIOUR OF PILE SUPPORTED WHARF IN LIQUEFIED SOILS

A parametric study is carried out to study the performance of pile supported wharf structure underliquefying and lateral spreading soil conditions using nonlinear static pushover analysis. Displacement-basedapproach is adopted to study the soil pile interaction. Piles are modelled as beam elements and the parts of the pilesembedded in soil are modelled as beams on Winkler foundation. The structure is modelled and analyzed usingSAP2000. Pile yielding and hinge formation patterns in the piles during soil liquefaction and lateral spreading statesare observed and compared with field observations. It is observed that when soil liquefied the base shear resistancedropped drastically and hence effected the performance of structure. Piles yielded at the interface of liquefied andnon-liquefied layers when soil liquefied. It is also observed that the structure performed poorly when liquefied depthfactor and slenderness ratio are increased. The method of analysis is simple and gives results confirming to the fieldobservations and hence is an easy tool for assessment of existing port structures and preventing future disasters.

Practical method and application study for predicting cyclic accumulative deformations of the saturated soft clay

The distribution of saturated soft clay is greatly wide in China. The current main measures adopted to deal with soft soil foundations may lead to environmental pollution, even some engineering accidents may happen on soft soil foundations. In order to solve engineering problems of saturated soft soil foundations well, researches of mechanical properties of them are necessary. One of the most important mechanical characteristics of saturated soft clay is its cyclic accumulative deformation under cyclic loadings. For saturated soft clay, the cyclic accumulative deformation is similar to the creep behavior under static loadings. Therefore, the cyclic accumulative deformation is equivalent to the creep, the number of loading cycles is seen as the time, and this study develops a practical method for predicting the cyclic accumulative deformation of saturated soft clay with the creep theory. The method is a pseudostatic elasto-plastic finite element method implemented by ABAQUS software. A fitted equation between cyclic accumulative strain and number of loading cycles and the empirical relationship of parameters of fitted equation were established with a series of cyclic triaxial compression tests. Then with this empirical relationship of parameters, the method developed by this study was employed to predict the cyclic accumulative deformation under cyclic triaxial tension tests. Predicted results were in good agreement with test results, and the effectiveness of this method was thus validated for different stress states. The method was then applied in analyzing the cyclic accumulative deformation for soft soil foundation of a pile-supported wharf structure.

FRAGILITY CURVES: A POWERFUL TOOL FOR SEISMIC VULNERABILITY ASSESSMENT OF PILE-SUPPORTED WHARVES

Seismic vulnerability assessment of structures is usually illustrated in the form of fragility curves. These curves show the probability that a component, element or system will be damaged to a given or more severe damage state as a function of a single predictive demand parameter. In addition, these curves are useful for seismic risk assessment and performance based design engineering, as well as prioritization of retrofitting programs. This paper reviews recent works on the seismic vulnerability analysis of pile-supported wharf structures. Different aspects for each paper are reviewed in terms of characteristic of the selected pile-supported wharf structure, institution and procedure of numerical modeling, capabilities of numerical models, analysis method for seismic response evaluation, ground motion records, damage states, intensity measure and obtained results. This paper shows that very limited studies have been performed on the seismic vulnerability of pile-supported wharves indicating a clear need to the development and application of fragility analysis of pile-supported wharf structures.

Seismic performance assessment of pile-supported wharves retrofitted by carbon fibre–reinforced polymer composite considering ageing effect

This study aims to assess seismic vulnerability of a typical pile-supported wharf considering ageing effects due to chloride-induced corrosion of the reinforced concrete piles. In order to improve the seismic performance of corroded wharves, carbon fibre–reinforced polymers is used as a retrofit technique. Three-dimensional model of the wharf is constructed using SAP2000, and pushover analysis is conducted to deduce the capacity curve of the wharf and establish quantitative criteria for bound of damage states. Then, using eight ground motion records, nonlinear static analysis called capacity spectrum method is used to evaluate the response of initial ( t = 0 years), corroded ( t = 25, 50, 75 years) and carbon fibre–reinforced polymer-retrofitted-corroded ( t = 50, 50, 75 years) pile-supported wharf structures. In order to assess the seismic vulnerability of wharves quantitatively, fragility curves are developed using two different engineering demand parameters, including displacement ductility factor ( µd) and state of plastic hinges. These fragility curves demonstrate the evolving damage potential under different levels of intensities taking into account time-dependent corrosion-induced deterioration. In addition, these curves reveal the effectiveness of carbon fibre–reinforced polymer method on the fragility reduction. Results indicate an increment in seismic vulnerability throughout the lifetime of the structure due to corrosion denoting the considerable impact of deterioration due to ageing effects on structural response. Moreover, using carbon fibre–reinforced polymer jacketing as a retrofit and repair method for corrosion-induced damaged structures can remarkably enhance their seismic performance.

Simplified Method of Seismic Performance Analysis for Pile-Supported Wharf Structures

The structural characteristics of a wharf segment may be modeled by using the simplified model due to unacceptable matrix sizes. The concept of simplified model is introduced at first. The locations of simplified model that represent original structure are determined by the locations of pile groups in defined areas. Force-displacement curve is calculated for wharf structure by pushover analysis, and simplified model is constituted applying estimated secant stiffness and effective damping according to force-displacement curve. Peak value of seismic response is estimated using elastic modal response spectra analysis and compared with simulated results from nonlinear time history analysis. It is proved that peak value of seismic response can be calculated using simplified model rapidly, and close to time history analysis result.

Simplified Method of Seismic Performance Analysis for Pile-Supported Wharf Structures

The structural characteristics of a wharf segment may be modeled by using the simplified model due to unacceptable matrix sizes. The concept of simplified model is introduced at first. The locations of simplified model that represent original structure are determined by the locations of pile groups in defined areas. Force-displacement curve is calculated for wharf structure by pushover analysis, and simplified model is constituted applying estimated secant stiffness and effective damping according to force-displacement curve. Peak value of seismic response is estimated using elastic modal response spectra analysis and compared with simulated results from nonlinear time history analysis. It is proved that peak value of seismic response can be calculated using simplified model rapidly, and close to time history analysis result.

Determination of optimal probabilistic seismic demand models for pile-supported wharves

One of the basic components of the Performance-Based Earthquake Engineering (PBEE) framework of Pacific Earthquake Engineering Research (PEER) Center is the probabilistic seismic demand model (PSDM). PSDM is based upon a representative relation between ground motion intensity measures (IMs) and engineering demand parameters (EDPs). This research aims to develop an optimal PSDM for typical pile-supported wharf structures in western US ports by using probabilistic seismic demand analysis (PSDA). In this study, 4 bins with 20 non-near-field ground motions and 7 typical pile-supported wharf structures are used to determine an optimal PSDM by PSDA. The model geometry used in this study has a hybrid configuration incorporating many common field conditions. The optimal PSDM should be practical, sufficient, effective and efficient – all tested through several IM–EDP pairs derived by PSDA. The ground motion IMs used in this study include characteristics such as spectral quantities, duration, energy-related quantities and frequency content. Different EDPs are considered for local, intermediate and global response quantities. The considered optimal PSDM comprises a spectral IM, such as spectral acceleration and one of several EDPs. The EDPs of moment curvature ductility factor, displacement ductility factor and horizontal displacement of embankment and differential settlement between deck and behind land are considered for local, intermediate and global response quantities, respectively. Optimal PSDMs are used within PEER–PBEE framework, where they are coupled with both ground motion intensity and structural element fragility models to yield probabilities of exceeding structural performance levels under certain seismic hazard.

Probabilistic Assessment for Seismic Performance of Pile-Supported Wharves

The main objective of this study is to investigate the influence of uncertainties associated with the material properties on the seismic performance of pile-supported wharves. For this purpose a two-dimensional finite difference model, representing typical pile-supported wharf structures from western United States has been constructed using software FLAC2D. Incremental dynamic analysis has been applied to evaluate the response of wharf structure under different levels of seismic loading. The uncertainties at both structural and geotechnical parameters have been investigated using a tornado diagram and a Wrst-Order Second-Moment (FOSM) analysis. It has been found that the uncertainties at the dead load of structure, friction angle of rock fill and the porosity of rock fill contribute most to the variability of the displacement ductility factor of the pile- supported wharf structures. Based on the results, design considerations have been provided.

Seismic Performance of Pile-Supported Wharf Structures considering Soil-Structure Interaction in Liquefied Soil

Many existing pile-supported marginal wharves within ports along the West Coast of the United States were designed in the late 1960s and early 1970s using the seismic design criteria available then, which were much less robust than the current criteria. As a result, structures designed using these criteria have often been severely damaged during the past earthquakes. This paper investigates the modal properties and vulnerability of such structures by using advanced structural and soil modeling procedures to perform two-dimensional nonlinear plane-strain seismic analyses using time histories of ground displacement and excess pore water pressures within the underlying soil embankment. Results show that the wharf structure experiences large permanent deformations and undergoes failure of the piles and pile-deck connections and pullout of batter piles in tension under large seismic events. Such failures were observed at the Port of Oakland during the 1989 Loma Prieta earthquake and also during other earthquakes throughout the world.