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.

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.

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.

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.

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.

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.

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.

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。

SMA限位对铁路自复位桥墩地震反应的影响

为研究形状记忆合金(SMA)对铁路自复位桥墩地震反应的影响,在已验证的两弹簧模型上增加SMA限位单元,以某铁路桥墩为工程背景,基于OpenSees平台建立数值分析模型,通过输入3条强震记录,采用非线性时程分析方法进行SMA限位的桥墩影响分析。讨论SMA限位装置关键参数初始间隙、初始预加力变化对墩顶位移和墩底弯矩的影响规律,并与预应力钢筋限位进行比较。研究结果表明:在普通地震动El-Centro与Taft波下,自复位桥墩的墩顶位移随限位装置初始间隙δ减小而减小,墩底弯矩随初始间隙δ减小而增大;随SMA限位装置初始预加力增大,自复位桥墩的墩顶位移减小,墩底弯矩增大。在近断层地震动Northridge下,SMA限位对自复位桥墩地震反应的影响复杂。在3条强震记录下,与预应力筋限位相比,SMA限位会减小墩底弯矩,增大墩顶水平位移。

从’91PIERS看电磁学研究发展趋势

本文从“电磁学研究进展会议(’91 PIERS)”的角度阐述了电磁学研究的现状和发展趋势,对一些新兴的分支也作了简短的描述。

Design and Engineering of Urban Interchange Ramp Bridge Structure

This paper analyzes the structural design of an urban interchange ramp bridge from four aspects,which are the superstructure,pier structure,foundation structure,and deck structure design to summarize the structural design ideas of this urban interchange ramp bridge,which can be used as a reference for future construction of the same bridge.

空心墩转体桥墩底应力分析

以某2×85 m预应力混凝土T构桥为例,建立了该桥的空间有限元模型,计算分析了桥梁转体阶段墩底的应力分布。分析表明:由于转体桥下部结构的构造特点使得空心墩墩底实心段顶部会产生较大的拉应力,设计中应采取有效的措施减小其产生。与球铰相对应的空心墩内宜设置中间隔板;在桥墩墩底实心段或在上承台设置预应力。结合工程实践,推荐在上承台设置预应力的方式,且应侧重横桥向预应力筋的配置。

底部填芯预制节段拼装桥墩抗震性能数值仿真分析

为促进预制节段拼装桥墩在山区复杂环境及强震地区的应用,提出了一种底部填芯的预制节段拼装桥墩,采用ABAQUS有限元模型讨论了填芯段高度、初始张拉力和耗能钢筋配筋率等关键参数对底部填芯预制节段拼装桥墩抗震性能的影响规律。研究结果表明:随着填芯段高度的增大,底部填芯预制节段拼装桥墩的承载能力和耗能能力显著提高,但残余位移和填芯段上部接缝开口宽度也增大;随着初始张拉力的增大,底部填芯预制节段拼装桥墩承载能力和耗能能力略有提高,残余位移和墩底混凝土损伤程度基本不变;随着耗能钢筋配筋率的增大,底部填芯预制节段拼装桥墩承载能力和耗能能力提高,但填芯段上部接缝开口宽度增大。研究结果可为底部填芯预制节段拼装桥墩合理构造提供参考,促进预制拼装桥墩在山区复杂环境和强震地区的应用。

Rapid repair techniques for severely earthquake-damaged circular bridge piers with flexural failure mode

In this study, three rapid repair techniques are proposed to retrofit circular bridge piers that are severely damaged by the flexural failure mode in major earthquakes. The quasi-static tests on three 1：2.5 scaled circular pier specimens are conducted to evaluate the efficiency of the proposed repair techniques. For the purpose of rapid repair, the repair procedure for all the specimens is conducted within four days, and the behavior of the repaired specimens is evaluated and compared with the original ones. A finite element model is developed to predict the cyclic behavior of the repaired specimens and the numerical results are compared with the test data. It is found that all the repaired specimens exhibit similar or larger lateral strength and deformation capacity than the original ones. The initial lateral stiffness of all the repaired specimens is lower than that of the original ones, while they show a higher lateral stiffness at the later stage of the test. No noticeable difference is observed for the energy dissipation capacity between the original and repaired pier specimens. It is suggested that the repair technique using the early-strength concrete jacket confined by carbon fiber reinforced polymer （CFRP） sheets can be an optimal method for the rapid repair of severely earthquake-damaged circular bridge piers with flexural failure mode.

Experimental Study on Local Scour Around Bridge Piers in Tidal Current

Local scour around a bridge pier is an important parameter for the design of a bridge. Compared with the local scour in a mono-directional current, the local scour in a tidal current has its unique characteristics. In this paper, several aspects of local scour around bridge piers in tidal current, including the scour development process, the plane form of a scour hole and the maximum scour depth, are studied through movable bed flume experiments.

Experimental research and finite element analysis of bridge piers failed in flexure-shear modes

In recent earthquakes, a large number of reinforced concrete （RC） bridges were severely damaged due to mixed flexure-shear failure modes of the bridge piers. An integrated experimental and finite element （FE） analysis study is described in this paper to study the seismic performance of the bridge piers that failed in flexure-shear modes. In the first part, a nonlinear cyclic loading test on six RC bridge piers with circular cross sections is carried out experimentally. The damage states, ductility and energy dissipation parameters, stiffness degradation and shear strength of the piers are studied and compared with each other. The experimental results suggest that all the piers exhibit stable flexural response at displacement ductilities up to four before exhibiting brittle shear failure. The ultimate performance of the piers is dominated by shear capacity due to significant shear cracking, and in some cases, rupturing of spiral bars. In the second part, modeling approaches describing the hysteretic behavior of the piers are investigated by using ANSYS software. A set of models with different parameters is selected and evaluated through comparison with experimental results. The influences of the shear retention coefficients between concrete cracks, the Bauschinger effect in longitudinal reinforcement, the bond-slip relationship between the longitudinal reinforcement and the concrete and the concrete failure surface on the simulated hysteretic curves are discussed. Then, a modified analysis model is presented and its accuracy is verified by comparing the simulated results with experimental ones. This research uses models available in commercial FE codes and is intended for researchers and engineers interested in using ANSYS software to predict the hysteretic behavior of reinforced concrete structures.

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.