Pile-supported Wharf Research Articles

Cascade earthquake and tsunami hazard assessment: A deterministic perspective for engineering purposes

Preventive management strategies are evolving towards multi-hazard risk estimates. Commonly, the multi-hazard characterization is pursued following a probabilistic approach. However, scenario-based evaluations can provide complementary key insights of relevance to design critical facilities.In this paper, an alternative deterministic analysis was explored to characterize the cascade seismic and tsunami actions of a 1755-alike Great Lisbon Earthquake and Tsunami event oriented to the container terminal of Sines deep-water seaport, Portugal, which is in expansion to increase the current 2.3 million TEU capacity to 7.1 million TEU.The analysis accounts source, propagation and site effects uncertainties influencing the multi-hazard estimates for different structural configurations representing the different stages of the extension plans for the infrastructure.The target-hazard assessment assumes ground motion acceleration and tsunami hydrostatic and hydrodynamic quantities as explanatory variables, respectively obtained from ground motion prediction equations and non-linear Shallow-Water equations. The intensity measures inherent to each of the inextricable candidate sources, Scandidate, were characterized over 864 seismic and 144 tsunami simulations and then compared to key-thresholds to identify the scenarios with damaging potential, Seligible. The quantities of each Seligible were assessed varying the earthquake and tsunami intensity measures as leading measures to define a set of combined worst-case scenarios for the infrastructure, Sworst. The cascading loading patterns for structural design purposes are then derived following the European and North American code provisions for earthquake and tsunami actions, respectively.The prediction of the cascading loading pattern at the terminal container of the Sines port quantifies PGA around 0.37 g for a seismic displacement-controlled behavior and peaks of hydrostatic and hydrodynamic components values around 1000 kNm−1 for tsunami force-controlled behavior during both the inflow and outflow cycles. A brief correlation between indicative action values and structural resistance of the current constructive solution raises awareness for the high probability of structural collapse of the pile-supported wharf due to an extreme 1755-alike Great Lisbon Earthquake and Tsunami threat, which would disrupt the port's operations and compromise its role as lifeline structure in case of emergency.

Effects of long duration earthquakes on the interaction of inertial and liquefaction-induced kinematic demands on pile-supported wharves

Nonlinear dynamic analyses were performed to evaluate the effects of ground motion duration on the dynamic response of a pile-supported wharf subjected to liquefaction-induced lateral ground deformations. The numerical model was first calibrated using recorded data from a well-instrumented centrifuge test, after which incremental dynamic analyses were conducted using a suite of spectrally matched motions with different durations. The nonlinear dynamic analyses were performed to evaluated three loading scenarios: combined effects of inertial loads from the wharf deck and kinematic loads from ground deformations, deck inertial loads only in the absence of liquefaction (with minimal kinematic loads), and kinematic loads only in the absence of deck mass inertia. The analysis results were evaluated to provide insights on the relative contribution of inertial and kinematic demands on the response of the wharf with respect to motion duration. It was found that the contribution of peak inertial and peak kinematic loads to the maximum total demand increases only slightly with motion duration and intensity. The response of the wharf was found to be primarily governed by kinematic demands when subjected to long-duration motions for the type of foundation analyzed in this study which is commonly used in the port industry.

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.

Liquefaction-induced lateral load on pile group of wharf system in a sloping stratum: A centrifuge shake-table investigation

In order to investigate the liquefied soil pressure inposed on an individual pile of pile group, a centrifugal shake table test on a pile-supported wharf on the sloping saturated sand stratum has been designed and implemented in this study. Final test results, including processing results of free-field soil responses as well as lateral displacements at the deck, are presented and discussed in detail. Analysis of pile bending moments of pile group shows that seaside pile bottom can come under more bending moment in contrast to landside piles, and the bending moment seems greater at pile top and bottom. A simplified finite element model has been constructed for an accurate analysis of liquefied soil pressure arising from lateral soil flow, where triangular soil pressure and uniform soil pressure need to be calibrated according to the measured monotonic bending moment of piles. Furthermore, comparisons with the current distribution law were made using the experimental outcomes. Finally, for investigating the effect of pile connection point rotational stiffness, parametric studies were carried out.

Seismic Vulnerability Assessment of Pile-Supported Wharves Using Fragility Surfaces

ABSTRACT The directional uncertainty of earthquakes significantly affects the results of seismic risk assessment and induces more critical responses by structures. This study assessed the seismic performance of a typical marine structure with high seismic vulnerability under the directional uncertainty of earthquakes. A concrete pile-supported wharf has been modeled in SAP2000 to implement damage analysis, and a number of incident angles were randomly selected for incremental dynamic analysis (IDA). IDA-based fragility analysis was carried out to develop the fragility surfaces. Comparison of the fragility surfaces revealed that the critical zones for the predefined damage states were not identical or unique.

Life-cycle cost analysis of pile-supported wharves under multi-hazard condition: aging and shaking

Investigating the economic consequences of the natural hazards on the infrastructures is a crucial task in any risk-based decision-making process. Life-cycle cost (LCC) analysis is an important tool in both design (to choose the most economic configuration) and analysis (to estimate the future cost of ownership) stages. The pile-supported wharves, as one of the main parts in a marine harbor system, may experience significant deterioration (i.e. strength reduction) and seismic shaking during their life time. In this paper, damage cost in multiple limit states of a deteriorated pile-supported wharf due to chloride corrosion is calculated. A precise finite element model is developed to account for structural aging and the simultaneous seismic shaking. Aging-dependent seismic fragility functions are first developed using incremental dynamic analysis. Next, the LCC analysis is conducted considering the crane damage, as well as, inspection and maintenance costs. The results are calculated for three seismic hazard levels. The findings confirm significance of corrosion on LCC of pile-supported wharf. It is observed that corrosion may increase the LCC of the structure and system (i.e. structure and cranes) by 15% and 8%, respectively. Finally, a set of analytical formulations are proposed for performance index as a function of age, damage state, and seismic hazard level.

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.

Time-dependent seismic fragility analysis of corroded pile-supported wharves with updating limit states

Pile-supported wharves, as one of the main components in marine harbor systems, are subjected to multiple hazards such as earthquakes and corrosion during their lifetime. In this paper, the corrosion initiation time due to chloride ion diffusion (using both the deterministic and probabilistic approaches), temperature and humidity variations are calculated for various steel materials in the typical pile-supported wharf of port Los Angeles. Various deterioration sources such as reduction in the ultimate strength and strain of prestressed strands and concrete compressive strength are simulated. The updating limit state functions are identified by nonlinear static analysis. Finally, the time-dependent fragility curves are developed using incremental dynamic analysis. Results show that corrosion considerably reduces the seismic performance due to both structural strength and ductility over the life cycle of the wharf. It also causes brittle fracture, a sudden and complete failure of the corroded piles towards the end of the structure’s life cycle. Finally, a set of analytical models is proposed to estimate the median of the aging fragility functions with a nearly constant dispersion.

Seismic performance evaluation of a pile-supported wharf system at two seismic hazard levels

This study presents a framework for assessing the seismic performance of a pile-supported wharf at different seismic hazard levels. A refined Three-Dimensional (3D) Finite Element (FE) model is conducted using the open-source computational platform OpenSees. The modeling strategies of the refined numerical model are given in detail, including refined modeling of free-field boundaries and soil-pile interaction. Two seismic hazard levels adopted by the design standard for seismic design of piers and wharves (ASCE 2014) are considered, namely, Contingency Level Earthquake (CLE) and Design Earthquake (DE). The seismic performance of the wharf-ground system is systematically explored in the following two aspects. First, the evaluation of seismic performance is based on the time history response for CLE (and DE) motion. Second, the seismic performance is assessed by averaging maximum response for all 28 DE and CLE motions. The results from this study reveal that (i) the seismic response of the wharf-ground system is larger under a DE motion than under a CLE motion; (ii) the pile foundation with a short free length is more vulnerable to damage for both seismic hazard levels; and (iii) the fiber strains of piles are significantly lower than the strain limits in the design standard (ASCE 2014).

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.

Lateral Bearing Performance of a Defective Pile-Supported Wharf with Batter Piles

Abstract The lateral bearing performance of a defective pile-supported wharf located on a slope was investigated through centrifuge modeling, and a numerical model was employed to back-analyze the ...

Experimental Study on Influence of Pile Wall on Flow Field Around Pile-Supported Wharf

Abstract Tidal flow has a significant influence on the mooring safety of vessels in deep-sea ports. In order to ensure the mooring safety of vessels, improving the structure form of the wharf can d...

Experimental modeling of wave load on a pile-supported wharf with pile breakwater

A hybrid structure of pile-supported wharf connecting with pile breakwater is tested in a flume with a scale factor of 1:30. Based on generating regular and irregular waves and accurately reproducing bed profile by using pulverized coal, both wave, scour and load characteristic of this structure are investigated. When structure under wave impact, violent wave reflection is observed and wave transmission is small. With the large wave height and water depth, wave overtopping is significant and induces bigger green water height. Compared with bed without covering layer, rubble covering layer obviously decreases the scour range of bed profile. Pressures of the structure have distinct spatial distribution characteristics. The existing plates between piles of breakwater can easily trap the air during wave attack and induce significant impact pressure. Besides, superstructure of pile-supported wharf is mainly suffered from uplift pressure and attains the maximum pressure when air gap becomes zero. Due to dynamic response of structure, measured forces have smaller values and larger periods than integrated forces, and both horizontal and vertical measured forces decrease with increasing relative wave height. The findings and data presented here may be used by oceanic numerical modelers and engineers, for future research as well as predesign.

Upgrading the Seismic Capacity of Pile-Supported Wharfs Using Semi-Active Liquid Column Gas Damper

One of the most important structures in the ports is the wharf. The most common one is the pile-supported wharf. This type of wharf is consisted of a number of piles and one deck which placed on the piles. In addition to the conventional loads that this structure should withstand, in seismic areas, pile-supported wharfs should have the necessary capacity and strength against seismic excitations. There are some approaches to increase the seismic capacity of the berth. One of these methods is to control the vibrations of the pile-supported wharf against earthquake loads using a damper. In this research, for the first time, a new semi-active damper called the semi active liquid column gas damper (SALCGD), was used to reduce the response of pile supported wharf under seismic loads. In the first step by applying different records of the earthquake, the most important parameter of this damper - the optimal opening ratio of the horizontal column- was obtained for this particular structure. In the following, the performances of this damper and its comparison with the tuned liquid column gas damper (TLCGD) were discussed. This study showed that the use of this semi-active damper (SALCGD) reduces the displacement of the pile-supported wharf by 35% and reduces the acceleration of the structure by 50% on average. In contrast, the passive damper (TLCGD) reduces the displacement of about 20 percent and the acceleration of about 30 percent. Therefore, it was observed that the semi-activation of the damper (SALCGD) had a significant improvement in its performance in controlling the vibrations of pile-supported wharf.

Technical Evaluation of Results of Field Demonstration Test Using Replaceable Slabs on Pile-Supported Wharf

今後建設から50年を迎える港湾施設が急増していく中で，施設の建設や維持管理に要するライフサイクルコストを低減させていくことは喫緊の課題である。また，港湾構造物の中でも桟橋の上部工は塩害による劣化が最も生じやすく，定期点検診断において容易に点検作業が行えないため，点検の作業性向上が課題であった。そこで，あらかじめ取り外しが容易な上部工として検討されたのがリプレイサブル構造の桟橋である。本稿は，リプレイサブル構造の床版を用いた現地実証試験結果とその技術的評価について報告する。

Wind driven natural ventilation through multiple gridirons of a pile-supported wharf to prevent atmospheric corrosion in the marine environment

Salt fog originating from the offshore zone can easily accumulate in the semi-enclosed space (called the gridiron space) formed by the beams and slabs of a pile-supported wharf. Such accumulation can lead to the premature failure of the durability of the wharf’s substructure. Previous works have mainly focused on material-level measures to eliminate the adverse effects of salt fog accumulation, such as the use of anti-corrosion concrete and anti-corrosion coatings, which could result in increased construction costs. In fact, salt fog can be extracted from a gridiron by natural ventilation in some cases, so it is important to examine the flow characteristics of the gridiron space. In this work, a numerical simulation was conducted with natural ventilation and auxiliary ventilation groups. The critical value of the shield ratio (defined as the height ratio of edge stringer to air inlet) that led to the weakest turbulence of airflow inside the gridiron was studied in the natural ventilation group. In addition, the effect of various configurations of vents was discussed; in accordance with the results, design recommendations were proposed to enhance the durability of a pile-supported wharf.

Seismic performance assessment of a pile-supported wharf retrofitted with different slope strengthening strategies

Pile-supported wharves may be subjected to severe damage during major earthquakes. As such, efficient strategies for retrofitting wharf systems are needed. In this study, we investigate the seismic performance of a pile-supported wharf retrofitted by the following three conventional slope strengthening strategies: i) improving the ground with a soil-cement mixture, ii) driving pin piles near dike toe, and iii) creating an underwater bulkhead system using sheet piles. Effectiveness of the three retrofit schemes is assessed comprehensively. First, seismic response of the as-built and retrofitted pile-supported wharf is investigated. Subsequently, performance of the retrofit strategies in mitigating the seismic vulnerability is thoroughly investigated by comparing component- and system-level fragility curves. It was found that: (1) overall, the strategies are effective in mitigating the seismic response and in reducing the seismic fragilities of the wharf system; (2) the performance of the retrofit measures varies at the structural component level, as a retrofit measure may have an isolated local negative effect for a certain structural component. In this regard, an appropriate retrofit strategy should be identified based on specifically defined retrofit purposes; and (3) as implemented, the soil-cement mixture performed best (in lowering the system seismic fragility), followed by the pin pile, and lastly the sheet pile.

A simplified reliability estimation method for pile-supported wharf on the residual displacement by earthquake

Pile-supported wharves undergo lateral displacement as well as structural damage due to earthquakes. Therefore, residual displacement and structural safety assessment are necessary for earthquake-resistant design of pile-supported wharves. This study introduces a simplified reliability estimation method for pile-supported wharves, involving the residual displacement caused by earthquakes and the variation of earthquake ground motions. As the residual displacement of wharves is strongly affected by the deformation of subsoil caused by earthquakes, a soil-structure system finite element earthquake response analysis was performed. To reduce the computational load for the evaluation of a probability distribution of residual displacement, a first-order second-moment method estimating the probabilistic response of structures with a small number of trials was applied. Thefinite element analyses demonstrate that the summed squared Fourier amplitudes (SSFAs) of the input seismic motion for a cumulative probability frequency band better estimated the residual displacement. A simplified reliability estimation method utilizing three results of finite element analyses is proposed following the demonstration of its applicability.

Nonlinear static analysis of a pile-supported wharf

Abstract The aim of this paper is to carry out a nonlinear static analysis using a case study of a pile-supported wharf in a new oil tankers port. The seismic activity in this area is very intense with the peak ground acceleration of 0.55 g; for this reason, it is very important to analyse the structural behaviour of the nonlinear situation. The analysis of the wharf, modelled in 3D by finite element method, serves to calculate the structure vibration periods (the structure’s first period is 1.68 s) and the capacity curve. The design of the structure follows traditional criteria by international guidelines, and its procedure is in accordance to classic theoretical methods and codes. For the selection of adequate characteristic earthquake input for the pushover analysis European and Venezuelan codes have been used. Besides being important to study the seismic influence on the body of the wharf and on critical elements, as well as and the interaction fluid-structure-soil, it is also important to analyse the consequences of structure failure and to estimate the maximum allowed displacement. The results show that the ultimate displacement is 18,81 cm. A port is an extremely strategic work, which needs to be carefully designed to avoid environmental damage and maintain human safety.

Study on Natural Ventilation in Gridiron of High-pile Wharf to Enhance The Durability Performance

The salt which origins from offshore zone is easy to gather in the semi-closed space formed by beams and slabs of pile-supported wharf called gridiron space, and that could induce the premature failure of durability of the wharf’s substructure. Previous work commonly focused on material-level measures which will lead to increased costs such as anti-corrosion concrete and anti-corrosion coatings to eliminate the adverse effects of that gathering of salt fog. In fact, the salt fog could be extracted from the gridiron by natural ventilation in some cases, so it is necessary to examine the flow characteristics in the gridiron space. In this work, the numerical simulation has been conducted with natural ventilation and auxiliary ventilation group. Critical value of the blocking ratio (defined as height ratio of edge stringer to air inlet) that makes the airflow inside the gridiron reach the strongest turbulence is found in natural ventilation group. In addition, the effect of different auxiliary ventilation schemes is compared in auxiliary ventilation group. Some recommendations for designing were proposed to enhancing pile-supported wharf’s durability.