Prestressed Concrete Bridge Research Articles

Development of Embedded EM Sensors for Estimating Tensile Forces of PSC Girder Bridges.

The tensile force of pre-stressed concrete (PSC) girders is the most important factor for managing the stability of PSC bridges. The tensile force is induced using pre-stressing (PS) tendons of a PSC girder. Because the PS tendons are located inside of the PSC girder, the tensile force cannot be measured after construction using conventional NDT (non-destructive testing) methods. To monitor the induced tensile force of a PSC girder, an embedded EM (elasto-magnetic) sensor was proposed in this study. The PS tendons are made of carbon steel, a ferromagnetic material. The magnetic properties of the ferromagnetic specimen are changed according to the induced magnetic field, temperature, and induced stress. Thus, the tensile force of PS tendons can be estimated by measuring their magnetic properties. The EM sensor can measure the magnetic properties of ferromagnetic materials in the form of a B (magnetic density)-H (magnetic force) loop. To measure the B-H loop of a PS tendon in a PSC girder, the EM sensor should be embedded into the PSC girder. The proposed embedded EM sensor can be embedded into a PSC girder as a sheath joint by designing screw threads to connect with the sheath. To confirm the proposed embedded EM sensors, the experimental study was performed using a down-scaled PSC girder model. Two specimens were constructed with embedded EM sensors, and three sensors were installed in each specimen. The embedded EM sensor could measure the B-H loop of PS tendons even if it was located inside concrete, and the area of the B-H loop was proportionally decreased according to the increase in tensile force. According to the results, the proposed method can be used to estimate the tensile force of unrevealed PS tendons.

APPLICABILITY OF WIDE-RANGE ULTRASONIC TESTING TO NON-DESTRUCTIVE INSPECTION OF GROUT CONDITION IN PRESTRESSED CONCRETE BRIDGES

Complete grouting of tendon ducts is important for durability of post-tensioned prestressed concrete (PC) bridges. Voids in the ducts may induce failure of PC tendons, possibly causing a reduction in load capacity and collapse of the bridge. The wide-range ultrasonic testing (WUT) is one of the non-destructive inspection techniques. The focus of this study is to examine the applicability of the WUT to grout inspection. This paper summarizes the characteristics of the non-destructive methods available for the PC grout inspection and outlines the sensing and analyzing techniques of the WUT method performed in practice in PC bridge construction. The inspection accuracy of the WUT method was examined by comparison to a sensor-based inspection method. This paper also reports comparative investigation and discusses the advantages of the WUT method including inspection accuracy, cost performance, time efficiency and safety. It was confirmed in on-site application that the WUT method was capable of determining grout condition at a concrete cover depth of 250 mm.

Influence of long-wavelength track irregularities on the motion of a high-speed train

ABSTRACTVertical track irregularities over viaducts in high-speed rail systems could be possibly caused by concrete creep if pre-stressed concrete bridges are used. For bridge spans that are almost uniformly distributed, track irregularity exhibits a near-regular wave profile that excites car bodies as a high-speed train moves over the bridge system. A long-wavelength irregularity induces low-frequency excitation that may be close to the natural frequencies of the train suspension system, thereby causing significant vibration of the car body. This paper investigates the relationship between the levels of car vibration, bridge vibration, track irregularity, and the train speed. First, this study investigates the vibration levels of a high-speed train and bridge system using 3D finite-element (FE) transient dynamic analysis, before and after adjustment of vertical track irregularities by means of installing shimming plates under rail pads. The analysis models are validated by in situ measurements and on-board measurement. Parametric studies of car body vibration and bridge vibration under three different levels of track irregularity at five train speeds and over two bridge span lengths are conducted using the FE model. Finally, a discontinuous shimming pattern is proposed to avoid vehicle suspension resonance.

Hollow precast segmental prestressed concrete bridge columns with a shear resistant connecting element

The purpose of this study was to investigate the performance of hollow precast segmental prestressed concrete (PSC) bridge columns with a shear resistant connecting element. A model of hollow precast segmental PSC bridge columns was tested under a constant axial load and a cyclically reversed horizontal load. The computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology) was used. Non-dimensional P-M interaction diagrams were developed to predict the design resistance of precast segmental PSC bridge columns. Among the numerous parameters, this study concentrates on concrete compressive strength, prestressing reinforcement ratio, effective prestress, diameter of circle passing through tendon centerlines-to-outside diameter of section ratio (Ds/Do) and inside diameter of section-to-outside diameter of section ratio (Di/Do). This study documents the testing of hollow precast segmental PSC bridge columns under cyclic loading and presents conclusions and design recommendations based on the experimental and analytical findings.

Strength-based differential tolerable settlement limits of bridges

Based on realistic modeling of 44 bridges in national bridge inventory using its actual layout and dimensions, a theoretical framework is defined to calculate the tolerable differential settlement limits based on the over-bending moment or over-shear force generated by settlements and the moment or shear capacity of the bridge. First, the derived over-bending moment or over-shear force is validated through literature results. Second, the differential settlement limits of bridges are derived from the bridge strength capacities. Finally, based on the established differential settlement limits, the relationship of bridge differential settlement limits with its span length, number of spans, bridge skew, and the bridge type is discussed and compared with American Association of State Highway and Transportation Officials specification (2010). A statistics-based differential settlement limit criterion is also suggested for steel and pre-stressed concrete bridges and compared with the field survey results. From the research outcomes, it is concluded that extra caution is needed when implementing the 0.4% differential settlement limits of bridge foundations in American Association of State Highway and Transportation Officials.

FRP strengthening of 60 year old pre-stressed concrete bridge deck units

Over the past few decades fibre reinforced polymers (FRPs) have gradually gained recognition as an effective material for the strengthening of reinforced concrete (RC) structures. FRP strengthening techniques provide an attractive alternative to the existing cumbersome traditional bridge strengthening methods due to FRPs superior properties, such as lightweight, easy to install, and highly resistant to corrosion. FRP strengthening has been sought as an option for strengthening pre-stressed concrete deck unit bridges in Queensland, Australia. This paper presents an investigation in to the effectiveness of two different FRP strengthening techniques on increasing flexural capacity and flexural stiffness of pre-stressed RC deck units. Two different FRP strengthening schemes, one with adhesively bonded carbon FRP (CFRP) pultruded plates and another with adhesively bonded and mechanically fastened glass FRP (GFRP) I beam and adhesively bonded CFRP pultruded plates were investigated. Three 60years old pre-stressed RC deck units taken from a bridge in Queensland, Australia were tested. One beam was tested as the control specimen, while the other two were strengthened with the two different FRP strengthening techniques. FRP strengthening using the two proposed systems found to increase the loads at serviceability limit by 10% and 31%, while ultimate strength was increased by 54% and 105%. A section analysis based on perfect composite section assumption was found to predict the moment curvature behaviour of the FRP strengthened specimens quite accurately. Existing design code methods were found to provide conservative design strength of the FRP strengthened pre-stressed RC deck units.

Finite element analysis of CFRP laminate repairs on damaged end regions of prestressed concrete bridge girders

Over the past couple decades, externally bonded fiber reinforced polymer (FRP) composites have emerged as a repair and strengthening material for many concrete infrastructure applications. This paper presents an analytical investigation of the use of carbon FRP (CFRP) for a specific problem that occurs in concrete bridge girders wherein the girder ends are damaged by excessive exposure to deicing salts and numerous freezing/thawing cycles. A 3D finite element (FE) model of a full scale prestressed concrete (PC) I-girder is used to investigate the effect of damage to the cover concrete and stirrups in the end region of the girder. Parametric studies are performed using externally bonded CFRP shear laminates to determine the most effective repair schemes for the damaged end region under a short shear span-to-depth ratio. Experimental results on shear pull off tests of CFRP laminates that have undergone accelerated aging are used to calibrate a bond stress-slip model for the interface between the FRP and concrete substrate and approximate the reduced bond stress-slip properties associated with exposure to the environment that causes this type of end region damage. The results of these analyses indicate that this particular application of this material can be effective in recovering the original strength of PC bridge girders with damaged end regions, even after environmental aging.

Vehicle Loads for Assessing the Required Load Capacity Considering the Traffic Environment

The effects of traffic loads on existing bridges are quite different from those of design live loads because of the various traffic environments. However, the bridge maintenance and safety assessment of in-service bridges maintain the design load capacity without considering the current traffic environment. The real traffic conditions on existing bridges may require a load capacity that is considerably different from the design. Therefore, the required load capacity of an existing highway bridge should be determined according to the extreme load effects that the bridge will experience from the actual traffic environment during its remaining service life for more rational maintenance of the infrastructure. A simulation process was developed to determine evaluation vehicle loads for bridge safety assessment based on the extreme load effects that may occur during the remaining service life. Realistic probabilistic traffic models were used to reflect the actual traffic environment. The presented model was used to analyze the extreme load effect on pre-stressed concrete (PSC) and steel box girder bridges, which are typical bridge types. The traffic environmental conditions included the traffic volume (2000–40,000), the proportion of heavy vehicles (15–45%), and the consecutive vehicle traveling patterns. The spans of the sample bridges were 30 m (PSC bridge) and 45 or 60 m (steel box girder bridge). In the results, the extreme load effects tended to increase with either the traffic volume or proportion of heavy vehicles. The evaluation vehicle loads for bridge safety assessment may be adjusted with the traffic conditions, such as the traffic volume, the proportion of heavy vehicles, and the consecutive vehicle traveling patterns.

Evaluation of initial prestress state in PS strand using the deformation characteristics of multi-strand anchor head

Prestressed concrete (PSC) bridge resists to deflection and cracking by prestressing its concrete superstructure using steel strands. The initial prestress force introduced in the strands at the completion of the structure influences sensitively its long-term performance. Rating the health of the PSC bridge should thus start with the knowledge of this initial prestress. However, the measurements given by the hydraulic jack and load cell used during prestressing may not be absolute indicators of the effective stress introduced in the strands. Considering that the strain distribution in the anchor can be used to measure the prestress in the strands and that the anchor head is the most accessible part of the PSC member, this study presents a method using the deformation characteristics of the anchor head to evaluate the initial prestress of the strands. To that goal, experimental and numerical analyses were performed on an anchorage-strand system considering the coefficient of friction between the wedge and the anchor head. The results show that the variation of the hoop strain measured in the multi-strand anchor head can be used to evaluate effectively the initial prestress state of the strands with respect to the applied jacking force.

Railway Continuous Prestressed Concrete Bridge Design in Ballastless Track Turnout Zones

Laying ballastless track on railway bridges has the advantages of reducing the train noise problem, improving passenger comfort, and reducing track maintenance costs. Therefore, railway bridges with ballastless track have gradually turned into a major trend in railway systems all over the world. In Taiwan, railway bridges with ballastless track have been in use for many years, with ballastless track turnouts also starting to be constructed in recent years. Where railway bridges with ballastless track turnouts are located in urban areas, special consideration must be given to the road crossings and the use of continuous bridges in the turnout zones. Accordingly, there arise a number of difficulties related to the bridge configurations or the continuous length of bridges being excessively long. Often, such situations necessitate the use of extremely large-sized bridge piers in the bridge design, or create the risk of serious damage to the pier structure should insufficient attention be given to any of the factors. This article will take a continuous prestressed concrete bridge as an example. The prestressed concrete bridge must be absolutely continuous, be able to include ballastless track turnout zones, and meet the needs of crossing roads. For this example, the length of the continuous prestressed concrete bridge is over 300 m. This article will also discuss the configuration of a continuous prestressed concrete bridge of railway, and—through the analysis of track–bridge interaction and temperature detection—provides suggestions on the optimal configuration model of the continuous prestressed concrete bridges, which should allow improper configuration and possible structural damage to be avoided.

Life cycle assessment based environmental impact estimation model for pre-stressed concrete beam bridge in the early design phase

The late rise in global concern for environmental issues such as global warming and air pollution is accentuating the need for environmental assessments in the construction industry. Promptly evaluating the environmental loads of the various design alternatives during the early stages of a construction project and adopting the most environmentally sustainable candidate is therefore of large importance. Yet, research on the early evaluation of a construction project's environmental load in order to aid the decision making process is hitherto lacking. In light of this dilemma, this study proposes a model for estimating the environmental load by employing only the most basic information accessible during the early design phases of a project for the pre-stressed concrete (PSC) beam bridge, the most common bridge structure. Firstly, a life cycle assessment (LCA) was conducted on the data from 99 bridges by integrating the bills of quantities (BOQ) with a life cycle inventory (LCI) database. The processed data was then utilized to construct a case based reasoning (CBR) model for estimating the environmental load. The accuracy of the estimation model was then validated using five test cases; the model's mean absolute error rates (MAER) for the total environmental load was calculated as 7.09%. Such test results were shown to be superior compared to those obtained from a multiple-regression based model and a slab area base-unit analysis model. Henceforth application of this model during the early stages of a project is expected to highly complement environmentally friendly designs and construction by facilitating the swift evaluation of the environmental load from multiple standpoints.

Structural Performance of Prestressed Concrete Bridge Piles Using Duplex Stainless Steel Strands

AbstractThe use of duplex high-strength stainless steel (HSSS) Grade 2205 prestressing strand and austenitic stainless steel (SS) Grade 304 spiral wire reinforcement is proposed for reinforcing pre...

Estimation of gross weight, suspension stiffness and damping of a loaded truck from bridge measurements

Particle filter method (PFM) based on Bayesian inference gives a reliable estimate of hidden parameters from the noisy measured signal. A new method of vehicle parameter identification based on measured bridge response has been proposed using PFM. An uncoupled iterative technique is utilised for solving bridge vehicle interaction problem which has been used as a forward solution of the PFM. A field test under moving truck has been conducted on an existing pre-stressed concrete bridge to collect response data at different locations. Based on the extracted bridge natural frequencies and measured peak acceleration responses at five sensor locations, finite element model of the tested bridge has been updated using response surface-based model updating technique. In addition to estimation of test truck parameters using measured bridge response, dynamic wheel load induced in the bridge has been determined. Excellent agreement has been found between the measured and reconstructed bridge response using estimated parameters.

Early-Age Behavior of an Adjacent Prestressed Concrete Box-Beam Bridge Containing UHPC Shear Keys with Transverse Dowels

AbstractAdjacent precast prestressed concrete box-beam bridges have been used in the United States for many years and have performed well. However, the shear keys between adjacent box beams are sus...

Analysis of Fiber-Optic Strain-Monitoring Data from a Prestressed Concrete Bridge

This paper presents data from fiber-optic strain monitoring of the Nine Wells Bridge, which is a three-span, pretensioned, prestressed concrete beam-and-slab bridge located in Cambridgeshire in the United Kingdom. The original deployment at the site and the challenges associated with collecting distributed strain data using the Brillouin optical time domain reflectometry (BOTDR) technique are described. In particular, construction and deployment issues of fiber robustness and temperature effects are highlighted. The challenges of interpreting the collected data as well as the potential value of information that may be obtained are discussed. Challenges involved with relating measurements to the expected levels of prestress, including the effects due to debonding, creep, and shrinkage, are discussed and analyzed. This paper provides an opportunity to study whether two commonly used models for creep and shrinkage, adequately model data collected in field conditions.

Behavior of prestressed concrete box bridge girders Under hydrocarbon fire condition

Abstract Currently, prestressed concrete (PC) bridges are often suffered from fire caused by oil tanker. However, there is very little research information and test data in the literature on the fire resistance of PC bridge girders. This paper presents an investigation into behavior of PC box bridge girder under hydrocarbon fire condition. A numerical model, in the form of the computer program ANSYS, for predicting the influence of a significantly critical factor, namely, prestress degree, on the performance of prestressed concrete bridge with box girder subjected to hydrocarbon fire is presented. The three stages associated with the numerical procedure, for evaluating fire resistance of PC box girders, namely, fire temperature calculation; cross-sectional thermal gradient evaluation and determination of mechanical response in box girders are elucidated. A simplified approach to account for thermal gradient distribution within girder section and deformations of PC box girder under hydrocarbon fire condition is incorporated into the FEM model. The applicability of the computer program for evaluating the fire resistance of PC box girder, resulting from combined effect of thermal and mechanical loading, is demonstrated through a case study. Through the numerical analysis results of case study, it is shown that different prestress degree adopted in girders has significant influence on the fire resistance of PC bridges.

Evaluating fire resistance of prestressed concrete bridge girders

This paper presents an approach for evaluating performance of prestressed concrete (PC) bridge girders exposed to fire. A finite element based numerical model for tracing the response of fire exposed T girders is developed in ANSYS. The analysis is carried out in three stages, namely, fire temperature calculation, cross sectional temperature evaluation, and then strength, deformation and effective prestress analysis on girders exposed to elevated temperatures. The applicability of the computer program in tracing the response of PC bridge girders from the initial preloading stage to failure stage, due to combined effects of fire and structure loading, is demonstrated through a case study, and validated by test data of a scaled PC box girder under ISO834 fire condition. Results from the case study show that fire severity has a significant influence on the fire resistance of PC T girders and hydrocarbon fire is most dangerous for the girder. The prestress loss caused by elevated temperature is about 10% under hydrocarbon fire till the girder failure, which can lead to the increase in deflection of the PC girder. The rate of deflection failure criterion is suggested to determine the failure of PC T girder under fire.

Considering Low Frequency Sound Propagation in Bridge Design

This paper investigates low frequency sounds radiated from a two-span continuous steel box girder bridge, three-span continuous steel plate girder bridge and three-span continuous prestressed concrete bridge. Those three bridges were selected as candidate bridges crossing a rural town. Velocity responses of bridges are estimated by a three-dimensional traffic-induced bridge vibration analysis, and those velocity responses are used in the frequency-domain sound propagation analysis by means of boundary element method. The propagation of sound pressure in the time-domain was also investigated. The inverse fast Fourier transformation was used to convert the sound pressure in the frequency-domain to the sound pressure at any point around the bridges in the time-domain. The analytical study showed that the lowest sound pressure level among three bridges was observed at the two-span continuous steel box girder bridge demonstrated.

Productivity Improvement for a Prestressed Concrete Bridge by Using U-shaped PC Girder Shin Tomei Expressway

Productivity Improvement for a Prestressed Concrete Bridge by Using U-shaped PC Girder Shin Tomei Expressway

Automated structural health monitoring based on adaptive kernel spectral clustering

Structural health monitoring refers to the process of measuring damage-sensitive variables to assess the functionality of a structure. In principle, vibration data can capture the dynamics of the structure and reveal possible failures, but environmental and operational variability can mask this information. Thus, an effective outlier detection algorithm can be applied only after having performed data normalization (i.e. filtering) to eliminate external influences. Instead, in this article we propose a technique which unifies the data normalization and damage detection steps. The proposed algorithm, called adaptive kernel spectral clustering (AKSC), is initialized and calibrated in a phase when the structure is undamaged. The calibration process is crucial to ensure detection of early damage and minimize the number of false alarms. After the calibration, the method can automatically identify new regimes which may be associated with possible faults. These regimes are discovered by means of two complementary damage (i.e. outlier) indicators. The proposed strategy is validated with a simulated example and with real-life natural frequency data from the Z24 pre-stressed concrete bridge, which was progressively damaged at the end of a one-year monitoring period.