Showing papers in "Journal of Bridge Engineering in 2015"

Nontarget Vision Sensor for Remote Measurement of Bridge Dynamic Response

Abstract: Displacements of railroad bridges under trainloads need to be closely monitored, but conventional displacement sensors have limitations for use in the field. This paper presents a new vision-based sensor system developed for remote measurement of structural dynamic displacements without requiring a specially installed target-marker panel. By implementing a robust object-search algorithm, the displacement can be accurately measured by tracking existing bridge surface features from a remote distance. The accuracy of measured dynamic displacements was first evaluated using a shaking table test. Then field tests were carried out on two railroad bridges subjected to freight trainloads traveling at various speeds. Measurements were taken remotely during the daytime and also at night from different distances with and without a target panel. Through comparison with a conventional contact-type displacement sensor, the high accuracy of the proposed nontarget remote-sensor system was demonstrated in the real...

Model Updating of Railway Bridge Using In Situ Dynamic Displacement Measurement under Trainloads

Abstract: To address the need for monitoring aging railway bridges, this paper presents a finite-element (FE) model updating approach using time-domain optimization based on in situ measurement of the bridge’s dynamic displacement histories under trainloads. Field tests are performed on a short-span plate girder railway bridge to measure its displacement response to freight trainloads with different speeds using a low-cost remote vision sensor recently developed by the authors’ group. A FE model of the bridge is developed considering train–track–bridge dynamic interactions. Sensitivity analysis is carried out to investigate the intrinsic effects of parameters of the train, track, and bridge subsystems on the dynamic response of the bridge. It is found that the bridge displacement response is primarily sensitive to the stiffness of the bridge, whereas the acceleration response is affected by many other parameters. This justifies that the bridge dynamic displacement is more suited than acceleration for updating the railway bridge stiffness. Consequently, a model updating approach is proposed using the measurement of bridge displacement response to trainloads. This approach is applied to the short-span bridge to first identify the train speed, followed by the bridge stiffness by minimizing the error between the measured and computed displacement time histories. Furthermore, this paper investigates the frequency characteristics from both the measured and computed displacements. The analysis shows that the trainload does not excite the bridge’s natural modes of vibration because the frequency is much lower than the bridge’s natural frequencies. Therefore, it is difficult to use the modal identification-based FE model updating methods based on the dynamic response measurement. This is commonly the case for short-span railway bridges, which tend to have high natural frequencies. The proposed periodic displacement measurement and time-domain FE model updating can be developed into an effective tool for long-term structural health monitoring of short-span railway bridges.

State-of-the-Art Review of Dynamic Impact Factors of Highway Bridges

Abstract: Dynamic impact of moving vehicles on bridges is an important and long-standing issue in the design and evaluation of bridges and has received much attention from researchers and engineers The use of the dynamic impact factor (IM) to account for the impact effect of vehicles has been widely accepted in bridge engineering Accurate evaluation of the IM will lead to safe and economical designs of new bridges and provide valuable information for condition assessment and management of existing bridges Nevertheless, agreement on the evaluation of IMs is yet to be reached Numerous studies have shown that the evaluation of the IM is a difficult task because it is influenced by a large number of parameters and uncertainties As a result, different forms and values of IMs are specified by different bridge design codes and this disagreement has been debated in many studies in the past few decades Furthermore, some field tests observed that the IMs in design codes are overestimated while many other field

Ultrahigh-Performance Concrete Segmental Bridge Technology: Toward Sustainable Bridge Construction

Abstract: This paper presents the current state of practice in the development of ultrahigh-performance concrete (UHPC) bridge construction in Malaysia. Since 2006, Dura Technology (DT) has pioneered research in the optimal uses of UHPC in bridge construction through its Sustainable Bridge Construction Initiative. After several years of research and development work, DT has collaborated with the Malaysia Works Ministry to design and build bridges in some of their bridge projects, especially those bridges under the rural development program where sourcing of material, site access, and construction method are major challenges when using conventional methods. The most current information and details on the completed and ongoing UHPC bridge projects in Malaysia are presented. To date, a total of 26 segmental UHPC bridge projects have been constructed and opened for service. In this paper, a selected UHPC bridge case study is examined in terms of the design aspects, quality control, constructability, and of how ...

Categories of SHM Deployments: Technologies and Capabilities

Abstract: The findings of an extensive literature survey focusing on bridge structural health monitoring (SHM) deployments are presented. Conventional, maturing, and emerging technologies are reviewed as well as deployment considerations for new SHM endeavors. The lack of published calibration studies (and quantification of uncertainty studies) for new sensors is highlighted as a major concern and area for future research. There are currently very few examples of SHM systems that have clearly provided significant value to the owners of monitored structures. The results of the literature survey are used to propose a categorization system to better assess the potential outcomes of bridge SHM deployments. It is shown that SHM studies can be categorized as one (or a combination) of the following: (1) anomaly detection, (2) sensor deployment studies, (3) model validation, (4) threshold check, and (5) damage detection. The new framework aids engineers specifying monitoring systems to determine what should be measured and why, hence allowing them to better evaluate what value may be delivered to the relevant stakeholders for the monitoring investments.

Finite-Element Analysis of Shear-off Failure of Keyed Dry Joints in Precast Concrete Segmental Bridges

Abstract: © 2014 This work is made available under the terms of the Creative Commons Attribution 4.0 International license,. The structural behavior of precast concrete segmental bridges largely depends on the behavior of the joints between segments. The current practice of precast concrete segmental bridges is to use small keys that are usually unreinforced, normally dry, and distributed over the height of the web and the flange of concrete segments. In this study, a numerical analysis model was established based on finite-element code to investigate structural behavior of keyed dry joints under direct shear. The concrete damage plasticity model along with the pseudodamping scheme were incorporated to analyze the system for microcracks and to stabilize the solution, respectively. The numerical model was calibrated by full-scale experimental results described in the literature. It was found that the predicted ultimate load, cracking evolution history, and final crack pattern agreed reasonably well with experimental results. The validated numerical model was then used for parametric study on factors affecting shear behavior of keyed dry joints, in this case confining pressure. The authors found that shear capacity predicted by the AASHTO code equation diverges from that predicted by numerical analysis at high confining pressure, because the contribution of friction in the total shear capacity decreased with an increase in confining pressure. Hence, the authors recommend reducing the friction coefficient used in the AASHTO code equation when high confining pressure is applied. Moreover, the propagation of inclined crack was arrested at high confining pressure owing to the fact that the fracture propagation direction is governed by the criterion of the maximum energy release rate.

Damage Detection in Long Suspension Bridges Using Stress Influence Lines

Abstract: Numerous long-span cable-supported bridges have been built throughout the world in recent years. These bridges begin to deteriorate once built and continuously accumulate damage during their long service life. The growing popularity of comprehensive structural health monitoring systems (SHMSs) in recently built long-span bridges has started a new trend of integrating SHMS and damage detection technology for real-time condition assessment of these bridges. This paper explores a novel damage detection technique based on stress influence lines (SILs) of bridge components and validates the efficacy of the technique through a case study of the Tsing Ma suspension bridge. A mathematical regularization method is first introduced to identify SILs based on the in situ measurement of train information and train-induced stress responses in local bridge components. Good agreement between the identified and baseline SILs demonstrates the effectiveness of the proposed identification method. Damage indexes based...

Hydrodynamic Experiment of the Wave Force Acting on the Superstructures of Coastal Bridges

Abstract: This paper presents a hydrodynamic experiment that examines the wave forces acting on the superstructure of coastal highway bridges to gain insight into the mechanical characteristics of the wave forces caused by the combination of storm surges and huge waves. The experiment is unique in that the specimen is a full bridge model, including its superstructure, substructure, and neighboring segments. After introducing the experimental setup and test program, this study analyzes the quasi-static and slamming components of the vertical wave force, the horizontal wave force of the superstructure in different clearances, wave heights, and wave periods. The test results are subsequently compared with two theoretical models suggested by Douglass and AASHTO guidelines to provide the experimental validation of those models. By comparing the test results and the existing models, a number of observations and discussions are produced to improve the accuracy of those theoretical models further.

Dynamic Assessment of Timber Railroad Bridges Using Displacements

Abstract: Infrastructure spending is such a large component of a railroad budget that it must be prioritized to meet the concurrent safety and line capacity requirements. Current bridge inspection and rating practices recommend observing bridge movements under a live load to help assess bridge conditions. However, measuring bridge movements under trains in the field is a challenging task. Even when they are measured, the relationships between bridge displacements and different loads/speeds are generally unknown. The research reported herein shows the effects of known train loadings, speeds, and traffic directions on the magnitude and frequency of displacements as measured on timber pile bents of a Class I railroad bridge. Researchers collected both vertical and transverse (lateral) displacements under revenue service traffic and work trains using LVDTs with a sampling frequency of 100 Hz. To investigate the effect of traffic on timber railroad bridges, displacements were measured under crossing events at d...

Seismic Response of a Damage-Resistant Recentering Posttensioned-HYFRC Bridge Column

Abstract: This paper presents the shake-table tests of a damage-resistant posttensioned bridge column designed to rock at the interface with its foundation. It compares the response to that of a conventional bridge column detailed to conform with current California seismic design criteria. The lower portion of the rocking column was built using hybrid fiber-reinforced concrete (HYFRC) and was armored with headed rebars; these features enhanced the compression damage resistance at the column base. Unbonded rebars that crossed the rocking plane provided hysteretic energy dissipation. Both columns were subjected to a sequence of scaled historical triaxial earthquake ground motions including near-fault pulse-like motions. The conventional column formed a flexural plastic hinge with extensive spalling. It accumulated a 6.8% residual drift ratio after a sequence of seven ground motions, which caused a peak drift ratio of 10.8%. The posttensioned-HYFRC column sustained only light damage and accumulated only a 0.4%...

Calibrating Markov Chain–Based Deterioration Models for Predicting Future Conditions of Railway Bridge Elements

Abstract: Existing nonlinear optimization-based algorithms for estimating Markov transition probability matrix (TPM) in bridge deterioration modeling sometimes fail to find optimum TPM values, and hence lead to invalid future condition prediction. In this study, a Metropolis-Hasting algorithm (MHA)-based Markov chain Monte Carlo (MCMC) simulation technique is proposed to overcome this limitation and calibrate the state-based Markov deterioration models (SBMDM) of railway bridge components. Factors contributing to rail bridge deterioration were identified; inspection data for 1,000 Australian railway bridges over 15 years were reviewed and filtered. The TPMs corresponding to a typical bridge element were estimated using the proposed MCMC simulation method and two other existing methods, namely, regression-based nonlinear optimization (RNO) and Bayesian maximum likelihood (BML). Network-level condition state prediction results obtained from these three approaches were validated using statistical hypothesis tests with a test data set, and performance was compared. Results show that the MCMC-based deterioration model performs better than the other two methods in terms of network-level condition prediction accuracy and capture of model uncertainties.

Multiscale Modeling and Model Updating of a Cable-Stayed Bridge. II: Model Updating Using Modal Frequencies and Influence Lines

Abstract: To facilitate an effective assessment of stress-related bridge performance and safety, a baseline multiscale finite-element (FE) model and a corresponding model-updating technique are required so that the FE model can best represent the prototype and can be used to well predict both global and local responses The companion paper demonstrates that considering modal frequencies alone as updating objectives cannot ensure the updated multiscale FE model being able to predict local (stress) responses accurately This paper presents a new updating method that uses both modal frequencies and multiscale (displacement and stress) static influence lines as updating objectives The paper first explains the relationship between displacement influence lines and mode shapes and the relationship between strain influence lines and strain mode shapes The formulation of the multiscale objective functions and the selection of updating parameters are then presented As a case study, the proposed model-updating met

Shear Behavior of Dry Joints with Castellated Keys in Precast Concrete Segmental Bridges

Abstract: Precast concrete segmental bridges with dry joints have the advantages of rapid construction speed and low cost. The shear strength and shear behavior of dry joints with castellated keys in precast concrete segmental bridges are still debatable. In this paper, full-scale dry joints with castellated keys were tested under different confining stress levels. The main parameters for tests were the number of keys, the confining stress, the depth in key geometry, and the distance between two keys. For comparison purposes, flat joints, monolithic joints, and joints with steel fibers were also tested. The shear behavior, shear capacity, and crack pattern of the joints were investigated as well. Two crack modes for the single-keyed joints are explicitly proposed. The phenomenon of sequential failure of multikeyed dry joints from the inferior key to the superior one was observed in the tests and verified by finite-element simulation. The experimental results obtained in these tests were compared with the design provisions. A shear failure mechanism of sequential failure for multikeyed dry joints is presented to explain the differences between the test results and the formula used. Based on the new explanation and test results, a reduced coefficient of 0.7 is recommended for the shear strength of three-keyed dry joints. Pending more test data, this conclusion could be extended to the shear strength of multikeyed dry joints to improve the formula.

Characteristics and Dynamic Impact of Overloaded Extra Heavy Trucks on Typical Highway Bridges

Abstract: Overloaded trucks, including some extra heavy trucks, often cause serious threats to bridges, such as deterioration, fatigue damage, or even collapse. Compared with the standard traffic design loads in design specifications, the actual characteristics of overloaded trucks, such as truck weight and types, are very difficult to predict or define. These characteristics are not specific only to the location. Rather, they depend on the economy, regulations, and law enforcement, and also vary over time as a result of uncertainties at a given location. In the current study, long-term traffic monitoring data are statistically studied to identify the key characteristics of extra heavy trucks, such as vehicle type, lane distribution, speed, axle weight, axle distance, and the variation of flow rate over time. All of the trucks from the traffic monitoring data are classified into 17 typical vehicle types, in which a total of 1,319 extra heavy truck scenarios are extracted from the traffic monitoring data. To...

Displacement Monitoring and Analysis of Expansion Joints of Long-Span Steel Bridges with Viscous Dampers

Abstract: The often-reported premature failures of expansion joints of long-span steel bridges call for a better understanding of their performance in service conditions. This paper presents the long-term monitoring and analysis of displacements of expansion joints, with emphasis on the influence of viscous dampers that were installed to mitigate seismic responses of the bridges. Data from the three long-span steel bridges in China—the Sutong Bridge, the Runyang Suspension Bridge, and the Jiangyin Bridge—are compared. Decomposition of displacement signals in various frequency bands reveals that temperature-induced movements contribute to only a small portion of the total cumulative displacements. Because of the small but rapid movements caused by vehicle/wind loads, the cumulative displacements of long-span steel bridges may far exceed those caused by temperature changes. According to the monitoring data, the existence of viscous dampers may reduce the vehicle/wind-induced displacements but have no signific...

Analytical and Finite-Element Modeling of FRP-Concrete-Steel Double-Skin Tubular Columns

Abstract: This paper presents a finite-element (FE) analysis of hybrid fiber-reinforced polymer (FRP)-concrete-steel double-skin tube (FSDT) in the form of columns. The FSDT columns that were examined consisted of a concrete wall sandwiched between an outer FRP tube and an inner steel tube. A FE software was used to develop a pushover analysis of three-dimensional FSDT models to simulate seismic loading. The FE models were validated against the experimental results gathered from seven FSDT columns tested under cyclic loading. The FE analysis results were in good agreement with the experimental backbone curves. The maximum error was 9% in predicting the bending strengths of the columns. A parametric study evaluated the effect of axial load level, concrete wall thickness, concrete strength, diameter-to-thickness ratio (D/t) of the steel tube, and number of FRP layers on the FSDT columns’ behavior. This study revealed that the behavior of FSDT columns is quite complex. It also revealed that this behavior is co...

Bridge Damage Detection Using Weigh-In-Motion Technology

Abstract: This paper proposes a novel Level I damage-detection technique for short- to medium-span road bridges using weigh-in-motion (WIM) technology. The technique is based on the input provided by two WIM systems: (1) a pavement-based WIM station located in the same route as the bridge (which gives vehicle weight estimates without the influence of the bridge), and (2) a bridge-based WIM (B-WIM) system that estimates vehicle weights based on the deformation of the bridge. The authors show that the ratio of estimations of vehicle weights by both systems is a reliable and robust indicator of structural integrity, even for WIM systems with relatively poor accuracy. They further show that this indicator is more sensitive to damage than the traditional method based on variation in natural frequencies.

Multiscale Modeling and Model Updating of a Cable-Stayed Bridge. I: Modeling and Influence Line Analysis

Abstract: Structural health monitoring (SHM) systems have been installed in many long-span bridges to assess bridge performance and safety. However, the number of sensors in a SHM system is always limited; therefore, not all of the bridge components can be directly monitored. To facilitate an effective assessment of stress-related bridge performance and safety, a multiscale finite-element (FE) model with detailed geometry and affordable computation time is needed. This paper presents the details of establishing a multiscale model for the Stonecutters Bridge in Hong Kong, which is a cable-stayed bridge with a 1,018-m main span. The twin-box deck of the bridge is modeled with shell elements in detailed geometry such that all stress responses in the bridge deck can be directly computed; other bridge components are modeled using either beam or truss elements. Each segment of the girder is then condensed into a superelement with the substructuring method in order to reduce the number of degrees of freedom. A se...

Effect of Solar Radiation on Suspension Bridge Performance

Abstract: Observations of a U.K. suspension bridge show that thermal expansion and contraction cycles do not follow simple linear relationships with a single temperature value and that time lag and temperature distribution can be significant factors. This investigation explores these effects by simulating the transient thermal and quasistatic response of the Tamar Bridge with separate finite-element models of the bridge and suspension cables. Thermal loads are determined by calculated solar radiation intensities and temperature data from the bridge monitoring system. Because cloud cover plays an important role in the levels of solar radiation, cloud coverage was estimated indirectly using monitored temperature differences between the top and bottom of the suspended structure. The results demonstrate that peak temperatures of the suspended structure and cables occur at different times. The lag is caused by differing material properties and the surfaces’ ability to absorb and lose heat. Transient phenomena ma...

Estimating Inspection Intervals for Bridges Based on Statistical Analysis of National Bridge Inventory Data

Abstract: This paper describes a statistical approach to estimating an appropriate inspection interval for highway bridges based on historical condition data collected from 20 years of routine inspections. Condition ratings of 4,270 bridges with concrete, steel, and prestressed-concrete superstructures were analyzed in this study to determine the time-in-condition rating (TICR) for superstructure components. The Anderson-Darling test was used to assess five conventional distributions to determine goodness of fit for describing the distribution of the TICR probabilistically. The test results revealed that the Weibull distribution was the best fit for the TICR for superstructure components. Parameters of the Weibull distribution were estimated for concrete, steel, and prestressed concrete in different condition ratings and used to define probability-density functions (PDFs), which were then used to determine the likelihood of a bridge deteriorating from a good condition to a poor condition over some time period. These data can be used for rational decision making regarding the appropriate inspection interval for bridges of a given type based on quantitative historical analysis of data. This study is beneficial because of the simplicity of the models developed and their accessibility for practicing engineers.

Shake-Table Test for a Typical Curved Bridge: Wave Passage and Local Site Effects

Abstract: To study the effects of ground motion spatial variations on curved bridges, this paper presents a shake-table test for a 1/10-scale typical curved bridge under spatial ground motions, including wave passage effect, local site effect, and ground motion multidimensionality. The experimental results show that both wave passage and local site effects have significant influence on seismic responses of curved bridges. Wave passage effect on curved bridges is attributed primarily to the higher asymmetric modes and pseudostatic displacements induced by asynchronous excitations, whereas local site effect is more obvious for structures with fundamental frequencies close to the predominant frequencies of the sites. Compared with straight bridges, the curvature radius causes curved bridges to be more sensitive to ground motion spatial variations, especially the local site effect. Therefore, curved bridges may be damaged more seriously than straight bridges during the same earthquake. Furthermore, seismic responses of irregular curved bridges are more sensitive to ground motion multidimensionality than are those of straight bridges. In this experiment, the effects of bridge abutments and nonuniform sites along the bridge were not considered.

Seismic Repair of Reinforced Concrete Bridge Columns: Review of Research Findings

Abstract: Repair has become a viable option for restoring the use of earthquake-damaged RC elements, even those that have been severely damaged. To select and design an appropriate repair system for damaged RC bridge columns, it is important that results from previous studies are known. This paper presents a comprehensive summary and review of techniques to repair earthquake-damaged RC bridge columns, as well as numerical methods for analyzing the response of repaired columns. Repair of columns with and without fractured longitudinal reinforcing bars is discussed. Studies are reviewed in terms of the apparent damage, repair technique, and performance of the repair. Advantages and disadvantages associated with each repair technique are discussed.

Shake Table Studies of Seismic Structural Systems of a Taizhou Changjiang Highway Bridge Model

Abstract: Taizhou Changjiang Highway Bridge is the longest three-pylon two-span suspension bridge in the world. To investigate the seismic performance of different connecting configurations between the deck and pylons, which are referred to as seismic structural systems, a 1/40-scale model of Taizhou Changjiang Highway Bridge incorporating different seismic structural systems was tested on the shake tables at Tongji University, Shanghai, China. In this paper, the design, construction, instrumentation, and loading protocol of the test model are introduced first. The fundamental frequencies of the eight bridge models are identified and are compared with numerical results. The damping ratios corresponding to the fundamental frequencies are obtained by the half-power bandwidth method. The test results show that the seismic responses of the three-pylon two-span suspension bridge under seismic loads are highly dependent on the connecting configurations between the deck and pylons. The relative displacement responses between the deck and the pylons in the longitudinal direction can be decreased effectively by viscous dampers or elastic cables. In addition, the influences of variations in those viscous dampers and elastic cables on the response of the model are investigated. Numerical results and test results are compared, and good agreement is achieved.

Method for Analyzing Time-Series GPR Data of Concrete Bridge Decks

Abstract: Ground-penetrating radar (GPR) has been extensively studied in North America as a nondestructive evaluation (NDE) technology for inspection of concrete bridge decks. With current practices, however, GPR has only proven to be an indicator of potential damage. Basically, to obtain the condition map for a concrete bridge deck, one would try to analyze one-time GPR data based mostly on the relative difference between reflection amplitudes at the top rebar layer. With a hypothesis that time-series GPR data can provide better information on bridge deck deterioration progression, this study investigates and proposes a new method to interpret those time-series data sets. Based on a correlation coefficient between A-scans, the proposed methodology was implemented and validated for a bare concrete bridge deck in New Jersey. The map provided by the proposed method clearly shows deterioration progression between the two consecutive scans, whereas the traditional analysis technique using the top rebar amplitud...

Aerodynamic Stabilization Mechanism of a Twin Box Girder with Various Slot Widths

Abstract: Five representative girder cross sections with various slot widths are utilized to analyze the effects of center slots on their aerodynamic performance, based on wind-tunnel tests and theoretical analyses. It is shown that the favorable aerodynamic effects of the center slot on bridge decks depend on the aerodynamic shape of the box girders and on the slot widths rather than unconditionally improving the aeroelastic stability. Further investigation of a streamlined box girder with various slot widths results in a modified Selberg formula to calculate the critical flutter wind speed for design purposes, wherein the Lorentz peak-value function is utilized. The flutter mechanism is illustrated utilizing a two-dimensional three-degrees-of-freedom (2D-3DOF) analysis scheme. The results indicate that the center slot changes the participation level of the heaving motion at the flutter onset, which is highly correlated with the critical flutter wind speed. In addition, particle image velocimetry (PIV) and proper orthogonal decomposition (POD) techniques are employed to assist in revealing the aerodynamic stabilization mechanism of the center slotting of box girders.

Experimental Seismic Performance of a Hybrid Sliding–Rocking Bridge for Various Specimen Configurations and Seismic Loading Conditions

Abstract: This paper presents the major findings of a shake table testing program on a large-scale (1:2.39) novel segmental concrete single-span bridge specimen. Emphasis is given on various specimen configurations and seismic loading conditions. The bridge specimen, termed hybrid sliding–rocking bridge, incorporated a box-girder superstructure with rocking joints and internal unbonded posttensioning (PT), and two single-column piers with internal unbonded PT. The pier columns included end rocking joints and intermediate sliding joints along the column height. Various configurations of the bridge specimen were considered with respect to the seismic mass and the superstructure-to-substructure connectivity. These configurations were subjected to far-field (F-F) and near-fault (N-F) ground motion ensembles scaled to various seismic hazard intensities. Asynchronous support excitation was also considered. The testing program included approximately 145 seismic tests. The dynamic response of the specimen was found...

Experimental Seismic Response of Hybrid Fiber-Reinforced Concrete Bridge Columns with Novel Longitudinal Reinforcement Detailing

Abstract: The experimental seismic response of two bridge columns built using highly flowable hybrid fiber-reinforced concrete under unidirectional static cyclic lateral loading is presented. The objective was to design bridge columns for use in regions of high seismic hazard that (1) sustain the seismic demands in a ductile manner; (2) minimize the concrete spalling that conventional RC bridge columns experience; and (3) avoid tension strain localization in the longitudinal steel bars observed in plastic hinge regions of fiber-reinforced concrete columns. The first column was designed to rock at its base. The second column was designed to form a flexural plastic hinge at its base and used stainless steel bars as longitudinal reinforcement. Both specimens experienced limited concrete spalling up to drift ratios of 4.8% and attained drift ratios of 11.3% without losing their vertical load resistance. The response of the specimens is compared with that of conventional RC columns.

Life-Cycle Cost Evaluation of Conventional and Corrosion-Resistant Steel for Bridges

Abstract: Steel bridges that are under severe chloride exposure due to deicing salts or marine environmental effects require frequent maintenance and repair activities to extend their service life and maintain an adequate performance level. In addition to the direct maintenance cost, these maintenance actions may lead to indirect costs associated with traffic delays and environmental effects that can significantly increase the life-cycle cost of the bridge under consideration. The use of more sustainable materials, such as maintenance-free steel, may increase the initial cost of the structure; however, the life-cycle cost, including the maintenance actions during the service life and their associated indirect effects, can be significantly reduced. This paper presents the computational approach and results of an analytical investigation to quantify the life-cycle cost of a steel bridge constructed using conventional painted carbon steel and to compare this cost to that of the same bridge constructed using ma...

New Method for Shape Finding of Self-Anchored Suspension Bridges with Three-Dimensionally Curved Cables

Abstract: A method for the shape finding of a specific type of self-anchored suspension bridge whose main cable is three-dimensionally curved is proposed in this study. The method, referred to as the coordinate iteration method (CIM), is developed from the force equilibrium features of the rational arch axis for suspension cables modeled by truss-cable elements. By establishing the linear iterative equations in terms of unknown coordinates and updating the relation matrices iteratively, a trial profile of the three-dimensional cable-only system easily and stably converges to the target system. The CIM is then extended to the shape finding of the total bridge system with the aid of a specific numerical model proposed in this study referred to as the indiscrimination coordinate rod model (ICRM). This model is used to simulate the core deformation effects of the total bridge. The detailed procedure undertaken to establish a finite-element model of the equilibrium system for the finished dead load state based on CIM and ICRM is also presented. The precision and efficiency of the method are demonstrated through actual numerical examples.