Numerical Analysis of Interaction Between Pile-Supported Pier and Bank Slope

Two and three-dimensional finite element analysis programs for pile-soil interaction are compiled. Duncan-Chang's Model is used. The construction sequence of the pier is modeled. The pile-soil interface element is used. The influence of the combination type of piles on the deformation of bank slope and pile behaviour is analyzed. Different designs of a pile-supported pier are compared thoroughly. Calculation results show that the stresses and displacements of the pile are directly related to the distance from the bank slope and the direction of inclination. An inclined prop pile set in the rear platform would remarkably reduce the stresses of piles and the displacement of the pier.

Interaction Between Pile-Supported Pier and Bank Slope

- Generally the toe of the bank slope in front of the pile- supported pier has to be dredged to meet the requirements of water depth for the berth of ships, while the top of the slope in rear of the pier must be backfilled and elevated to make connections with land transportation. Then the natural state of equilibrium of the slope is destroyed, and some deformation and displacement are unavoidably induced in the soil mass which will exert an undesirable influence on the pile foundation of the pier. This is a typical problem of the interaction between the so-called 'passive pile' and surrounding soil, and has been scarcely studied in the literature of geotechnical engineering. In this paper, field observation, model tests and numerical analysis conducted by the authors to study the interaction between pile-supported pier and bank slope are briefly described and some preliminary results are presented.

Seismic response and correlation analysis of a pile-supported wharf to near-fault pulse-like ground motions

Earthquake investigations have shown that near-fault pulse-like(NF-P)ground motions have unique characteristics compared to near-fault non-pulse-like(NF-NP)and far-field(FF)ground motions.It is necessary to study the seismic response of pile-supported wharf(PSW)structures under NF-P ground motions.In this study,a three-dimensional finite element numerical model is created to simulate a PSW.By imparting three types of ground motion,the engineering demand parameters(EDPs)of PSW under NF-P ground motions were analyzed and compared,in which EDPs are the maximum displacement and bending moment of the piles.Twenty intensity measures(IMs)were selected to characterize the properties of ground motions.The correlation between IMs and EDPs was explored.The results show that the piles present larger displacement and bending moment under NF-P ground motions compared to NF-NP and FF ground motions.None of the IMs have a high correlation with EDPs under NF-P ground motions,and these IMs are more applicable to FF ground motions.The correlation coefficients between EDPs and IMs under three types of ground motion were obtained,which will provide a valuable reference for the seismic design of PSWs.

Influence of pier height on the safety of trains running on high-speed railway bridges during earthquakes

Sudden earthquakes pose a threat to the running safety of trains on high-speed railway bridges,and the stiffness of piers is one of the factors affecting the dynamic response of train-track-bridge system.In this paper,a experiment of a train running on a high-speed railway bridge is performed based on a dynamic experiment system,and the corresponding numerical model is established.The reliability of the numerical model is verified by experiments.Then,the experiment and numerical data are analyzed to reveal the pier height effects on the running safety of trains on bridges.The results show that when the pier height changes,the frequency of the bridge below the 30 m pier height changes greater;the increase of pier height causes the transverse fundamental frequency of the bridge close to that of the train,and the shaking angle and lateral displacement of the train are the largest for bridge with 50 m pier,which increases the risk of derailment;with the pier height increases from 8 m to 50 m,the derailment coefficient obtained by numerical simulations increases by 75% on average,and the spectral intensity obtained by experiments increases by 120% on average,two indicators exhibit logarithmic variation.

Reliability-based life-cycle cost seismic design optimization of coastal bridge piers with nonuniform corrosion using different materials

Reinforcement corrosion is the main cause of performance deterioration of reinforced concrete(RC)structures.Limited research has been performed to investigate the life-cycle cost(LCC)of coastal bridge piers with nonuniform corrosion using different materials.In this study,a reliability-based design optimization(RBDO)procedure is improved for the design of coastal bridge piers using six groups of commonly used materials,i.e.,normal performance concrete(NPC)with black steel(BS)rebar,high strength steel(HSS)rebar,epoxy coated(EC)rebar,and stainless steel(SS)rebar(named NPC-BS,NPC-HSS,NPC-EC,and NPC-SS,respectively),NPC with BS with silane soakage on the pier surface(named NPC-Silane),and high-performance concrete(HPC)with BS rebar(named HPC-BS).First,the RBDO procedure is improved for the design optimization of coastal bridge piers,and a bridge is selected to illustrate the procedure.Then,reliability analysis of the pier designed with each group of materials is carried out to obtain the time-dependent reliability in terms of the ultimate and serviceability performances.Next,the repair time of the pier is predicted based on the time-dependent reliability indices.Finally,the time-dependent LCCs for the pier are obtained for the selection of the optimal design.

Behaviors of pile-supported embankments in highway engineering

Based on the variational approach for pile groups embedded in soil modeled using a load-transfer curve method, a practical method was conducted to estimate the settlement of symmetric pile group supported embankments. The working mechanism of composite foundations improved by rigid or semi-rigid columns is analyzed by this method. Under equivalent strain conditions, the pile-soil stress ratio approaches the pile-soil modulus ratio up to a limited value of pile stiffness （Rm〈10）; in the subsequent stages of high pile stiffness （Rm〉10）, a further increase in the pile-soil modulus ratio cannot lead to a significant increase of stress transferred to the columns in composite foundations. The major influencing factor of the stress concentration from soil to pile in a high pile-soil modulus ratio is the padding stiffness. For the composite foundation improved by cement mixing columns, the effective column length is about 15 to 20 m and it is a more economical and effective design when the column length is less than 15 m.

Analysis of ground vibrations induced by high-speed train moving on pile-supported subgrade using three-dimensional FEM

The pile-supported subgrade has been widely used in high-speed railway construction in China.To investigate the ground vibrations of such composite foundation subjected to moving loads induced by high-speed trains(HSTs),three-dimensional(3D)finite element method(FEM)models involving the pile,pile cap and cushion are established.Validation of the proposed model is conducted through comparison of model predictions with the field measurements.On this basis,ground vibrations generated by HSTs under different train speeds as well as the ground vibration attenuation with the distance away from the track centerline are investigated.In addition,the effects of piles and pile elastic modulus on ground vibrations are well studied.Results show that the pile-reinforcement of the subgrade could significantly contribute to the reduction of ground vibrations.In particular,the increase of elastic modulus of pile could lead to consistent reduction of ground vibrations.However,when the pile elastic modulus is beyond 10 GPa,this benefit of pile-reinforcement on vibration isolation can hardly be increased further.

Experimental investigation and flow analysis of clear-water scour around pier and abutment in proximity

Local scour around bridge piers and abutments is one of the most significant causes of bridge failure.Despite a plethora of studies on scour around individual bridge piers or abutments,few studies have focused on the joint impact of a pier and an abutment in proximity to one another on scour.This study conducted laboratory experiments and flow analyses to examine the interaction of piers and abutments and their effect on clear-water scour.The experiments were conducted in a rectangular laboratory flume.They included 18 main tests(with a combination of different types of piers and abutments)and five control tests(with individual piers or abutments).Three pier types(a rectangular pier with a rounded edge,a group of three cylindrical piers,and a single cylindrical pier)and two abutment types(a wingewall abutment and a semicircular abutment)were used.An acoustic Doppler velocimeter was used to measure the three-dimensional flow velocity for analyses of streamline,velocity magnitude,vertical velocity,and bed shear stress.The results showed that the velocity near the pier and abutment increased by up to 80%.The maximum scour depth around the abutment increased by up to 19%.In contrast,the maximum scour depth around the pier increased significantly by up to l71%.The presence of the pier in the vicinity of the abutment led to an increase in the scour hole volume by up to 87%relative to the case with a solitary abutment.Empirical equations were also derived to accurately estimate the maximum scour depth at the pier adjacent to the abutment.

Experimental and numerical study on cyclic behavior of a UHPC-RC composite pier

Conventional reinforced concrete piers are vulnerable to severe compressive damage under strong earthquake conditions and are difficult to quickly rehabilitate.This paper develops a new type of composite pier,consisting of ultra-high-performance concrete(UHPC)and reinforced concrete(RC).This UHPC-RC composite pier uses a UHPC cover outside of an RC core to achieve a high load-carrying capacity and mitigate compressive damage.An experiment is performed to evaluate the performance of the UHPC-RC composite pier under cyclic deformation.The crack development,ultimate failure modes,and load-carrying capacities of the pier are observed.Because of the extraordinary compressive strength of UHPC,the composite pier suffers little compressive damage under large lateral deformations.The composite pier fails as a result of fracturing of the reinforcement.A numerical model is developed to reproduce the cyclic behavior of the composite pier.On the basis of the verified numerical model,a parametric analysis is used to investigate the influence of the thickness of the UHPC cover and the axial load ratio.Finally,an approach is recommended for designing composite piers.

Comparative analysis of seismic response characteristics of pile-supported structure

In order to analyze the seismic response characteristics of pile-supported structure,a computational model considering pile-soil-structure interaction effect was established by finite element method.Then,numerical implementation was made in time domain.At the same time,a simplified approximation for seismic response analysis of pile-soil-structure system was briefly presented.Furthermore,comparative study was performed for an engineering example.Through comparative analysis,it is shown that the results obtained by the simplified method well agree with those achieved by the finite element method.These results show that spectrum characteristics and intensity of input earthquakes are two important factors that can notablely influence the seismic response characteristics of superstructure.When the input ground motion acceleration amplitude gradually increases from 1 to 4 m/s2,the acceleration of pier top will increase,but it will not be simply proportional to the increase of input acceleration amplitude.

Regularity classification and corresponding analysis method requirements of horizontally curved bridges with unequal pier heights

The seismic behavior of horizontally curved bridges,particularly with unequal height piers,is more complicated than that of straight bridges due to their geometric properties.In this study,the seismic responses of several horizontally curved single-column-bent viaducts with various degrees of curvature and different pier heights have been investigated,employing three different analysis approaches:namely,modal pushover analysis,uniform load method,and nonlinear time history analysis.Considering the investigated bridge configurations and utilizing the most common regularity indices,the results indicate that viaducts with 45-degree and 90-degree deck subtended angles can be categorized as regular and moderately irregular,respectively,while the bridges with 180-degree deck subtended angle are found to be highly irregular.Furthermore,the viaducts whose pier heights are asymmetric may be considered as irregular for almost all ranges of the deck subtended angles.The effects of higher transverse and longitudinal modes are discussed and the minimum analysis requirements are identified to assess the seismic response of such bridge configurations for design purposes.Although the Regularity Indices used here are useful tools to distinguish between regular and irregular bridges,further studies are needed to improve their reliability.

Study of beat phenomenon on a pile-supported pipeline system subjected to wave loading

Classical beat phenomenon has been observed in most combined systems. The focus of this paper is to provide a better understanding of this phenomenon in an offshore pile-supported pipeline system. The beat phenomeon is caused by the coupling movement of the pipeline and its vertical pile support under certain conditions. It can induce excessive vibration and cause fatigue failure at pipe elbow. However, in some circumstances it does not exist. Numerical results in both frequency and time domains are presented to elucidate this phenomenon in a combined pipeline system. The conclusions of this paper could give constructive guidance to future design of simply supported pipeline systems.

Time-varying seismic fragility analysis of durability damage of high-tensile reinforcement ECC bridge pier

The deterioration of the performance of offshore bridges is particularly prominent due to the complex natural environment,including the coupling effects of earthquake and seawater erosion.In particular,bridge piers are the main energy-consuming and load-bearing components,so that excellent seismic capacity of bridge piers is the key to avoiding bridge damage.Although earthquake resistant behavior of ordinary reinforced concrete bridge piers(ordinary pier)can be improved by increasing the section size and reinforcement ratio of piers,the improvement of the earthquake resistant behavior is limited.To further improve the earthquake resistant behavior of bridge piers,high-tensile reinforcement engineered cementitious composite(ECC)bridge piers are utilized and time-varying seismic fragility analysis are conducted in this study.The refined model of a bridge pier is built by OpenSees.First,the influence of ECC replacement height on pier curvature is analyzed to determine the reasonable ECC height.Then,the time-varying fragility analysis of high-tensile reinforcement ECC piers(ECC composite piers)with durability damage are evaluated considering the time-varying law of materials.Four damage states,slight damage,moderate damage,extensive damage and complete collapse,are utilized in the study.These fragility curves indicate the durability damage can debase the earthquake resistant behavior of piers continually,the exceedance probability of the same state of destruction increases with the increase of peak ground acceleration(PGA)and service time of pier.The results also indicate that the corrosion level of chloride ion to pier is small during the early service period,and the bridge pier vulnerable curve is similar to that of the new bridge pier.As the level of chlorine ion corrosion deepens,transcendental probability is increased.Compared with the ordinary pier,the exceedance probability in each limit state of ECC composite piers is significantly reduced.The proposed ECC composite pies leads to better realistic time-varying earthquake resistant behavior.

ML and CFD Simulation of Flow Structure around Tandem Bridge Piers in Pressurized Flow

Various regions are becoming increasingly vulnerable to the increased frequency of floods due to the recent changes in climate and precipitation patterns throughout the world.As a result,specific infrastructures,notably bridges,would experience significant flooding for which they were not intended and would be submerged.The flow field and shear stress distribution around tandem bridge piers under pressurized flow conditions for various bridge deck widths are examined using a series of three-dimensional(3D)simulations.It is indicated that scenarios with a deck width to pier diameter(Ld/p)ratio of 3 experience the highest levels of turbulent disturbance.In addition,maximum velocity and shear stresses occur in cases with Ld/p equal to 6.Results indicate that increasing the number of piers from 1 to 2 and 3 results in the increase of bed shear stress by 24%and 20%respectively.Finally,five machine learning algorithms,including Decision Trees(DT),Feed Forward Neural Networks(FFNN),and three Ensemble models,are implemented to estimate the flow field and the turbulent structure.Results indicated that the highest accuracy for estimation of U,and W,were obtained using AdaBoost ensemble with R2=0.946 and 0.951,respectively.Besides,the Random Forest algorithm outperformed AdaBoost slightly in the estimation of V and turbulent kinetic energy(TKE)with R2=0.894 and 0.951,respectively.

Hysteretic behavior of post-tensioned precast segmental CFT double-column piers

Considering the desirable behavior of concrete filled steel tube(CFT)columns and the complicated behavior of segmental double-column piers under cyclic loads,three post-tensioned precast segmental CFT double-column pier specimens were tested to extend their application in moderate and high seismicity areas.The effects of the number of CFT segments and the steel endplates as energy dissipaters on the seismic behavior of the piers were evaluated.The experimental results show that the segmental piers exhibited stable hysteretic behavior with small residual displacements under cyclic loads.All the tested specimens achieved a drift ratio no less than 13%without significant damage and strength deterioration due to the desirable behavior of CFT columns.Since the deformation of segmental columns was mainly concentrated at the column-footing interfaces,the increase of the segment numbers for each column had no obvious effects on the loading capacity but reduced the initial stiffness of the specimens.The use of steel endplates improved the bearing capacity,stiffness and energy dissipation of segmental piers,but weakened their self-centering capacity.Fiber models were also proposed to simulate the hysteretic behavior of the tested specimens,and the influences of segment numbers and prestress levels on seismic behavior were further studied.

Numerical Simulation of the Influence of Water Flow on the Piers of a Bridge for Different Incidence Angles

A two-dimensional mathematical model is used to simulate the influence of water flow on the piers of a bridge for different incidence angles.In particular,a finite volume method is used to discretize the Navier-Stokes control equations and calculate the circumferential pressure coefficient distribution on the bridge piers’surface.The results show that the deflection of the flow is non-monotonic.It first increases and then decreases with an increase in the skew angle.

河道斜交桥梁壅水及流场特性分析

圆端桥墩是平原河道内一种常见的桥墩型式,为探究斜交圆端桥墩不同布置方式引起的壅水特性和水流流态变化,建立三维数值模型,采用SIMPLE算法耦合k-ε紊流模型求解N-S方程组,应用VOF法追踪自由液面,分析了单个桥墩壅水特性、绕流流场和升阻力系数随斜交角度变化的规律。研究结果表明:下游墩前壅水高度最大,壅水长度最长,上游墩前冲高值最大;水流绕流经过上游桥墩后偏向下游桥墩侧,桥墩垂直桥轴线布置方式绕流形成的壅水叠加效应更明显;斜交桥梁布置采取圆端桥墩时,桥墩顺水流布置,可有效减小阻水宽度与壅水高度,弱化流场结构变化。

Ultra-High Performance Concrete: An Advanced Solution for Accelerated Bridge Pier Cap Rehabilitation and Bearing Replacement

The objective of this paper is to propose and illustrate feasibility, approach, validation as per prevailing codes and design standards, specification to rehabilitate bridge pier cap by using Ultra-High Performance Concrete (UHPC). The evaluation of existing pier caps and bearings indicates that the complete removal of existing bearing is undesirable due to 1) massive size of bearing 2) difficulty in cutting through the thick components of existing bearing 3) deeply anchored lower shoe of existing bearings 4) huge cost and time required to erect temporary support system for superstructure to facilitate the construction of new piers. To overcome these difficulties, UHPC could be cast around the lower shoe up to the existing bearing pin. This UHPC cast could be used to support jacks and temporary bearings. The new low height permanent bearing could then be installed after removing the upper shoe of the existing bearing. In the present research, first properties of UHPC are summarized followed by evaluation of case studies to check feasibility of the solution to rehabilitate pier cap by using UHPC. The complex load paths in pier cap are idealized by using validated strut and tie model as per prevailing AASHTO LRFD Bridge Design Specification.

An Important Film: Polychromy in the Pier Luigi Nervi Halls at the Turin Exhibition Center

Hidden by several layers of white paint,the almost forgotten polychromy of Nervi’s exhibition halls emerges from historical images,not necessarily intended to document the complex,but rather as a setting for exhibitions,fairs or film and advertising sets.Historical documentation reveals Nervi’s presence on the building site and his desire to supervise the finishing phases.The first stratigraphic investigations also testify to his attention color,as well as the subsequent transformations of use.Specific theoretical and technical issues regarding the conservation of the pictorial layers in relation to the conservation of the reinforced concrete elements are outlined.Furthermore,the use of polychromy in combination with the original employment of natural and artificial light sources introduces new facets into the analysis of Nervi’s work,offering the opportunity for original reflection.This is particularly true if we consider the impact of the interventions carried out so far,even those considered non-invasive,such as routine maintenance operations and some technological upgrades.

PIER模式在落实大学英语视听说教学课程思政中的应用研究——以《新视野大学英语视听说教程(思政智慧版)》为例

大学英语视听说教学是大学英语教学至关重要的一部分,但对其课程思政的研究还有待完善,本研究以《新视野大学英语视听说教程(思政智慧版)》为抓手,通过深挖教材寻找大学英语视听说教学课程思政的切入点,讨论了PIER模式在视听说课程思政育人中的应用。大学英语视听说课程思政应当以教材为切入点,PIER模式实现了大学英语视听说教学过程与育人过程浑然天成,使学生在习得语言技能的同时收获德育教育。