Prestressed Concrete Bridge Research Articles

Computation of Deflections for PC Box Girder Bridges with Corrugated Steel Webs considering the Effects of Shear Lag and Shear Deformation

Prestressed concrete (PC) girders with corrugated steel webs (CSWs) have received considerable attention in the past two decades due to their light self-weight and high prestressing efficiency. Most previous studies were focused on the static behavior of CSWs and simple beams with CSWs. The calculation of deflection is an important part in the static analysis of structures. However, very few studies have been conducted to investigate the deflection of full PC girders or bridges with CSWs and no simple formulas are available for estimating their deflection under static loads. In addition, experimental work on full-scale bridges or scale bridge models with CSWs is very limited. In this paper, a formula for calculating the deflection of PC box girders with CSWs is derived. The longitudinal displacement function of PC box girders with CSWs, which can consider the shear lag effect and shear deformation of CSWs, is first derived. Based on the longitudinal displacement function, the formula for predicting the deflection of PC box girders with CSWs is derived using the variational principle method. The accuracy of the derived formula is verified against experimental results from a scaled bridge model and the finite element analysis results. Parametric studies are also performed, and the influences of shear lag and shear deformation on the deflection of the box girder with CSWs are investigated by considering different width-to-span ratios and different girder heights. The present study provides an effective and efficient tool for determining the deflection of PC box girders with CSWs.

Development of Robotic Nondestructive Testing of Steel Corrosion of Prestressed Concrete Bridge Girders using Magnetic Flux Leakage System

This paper describes the development and validation of a new magnetic-based corrosion detection device integrated in a robotic system. The system nondestructively scans the length of AASHTO-type prestressed concrete I-girders of bridges. The system includes two primary subsystems: an independent magnetic flux leakage (MFL) system for nondestructive testing, and a robotic rover to transport the MFL system along the girder’s length with navigation around transverse diaphragms. The MFL unit inspects prestressing steel strands embedded in concrete and detects cross-section losses caused by corrosion. The MFL is designed with two permanent magnets to magnetize embedded strands and multiple Hall-effect sensors to detect normal and axial magnetic flux leakage. The system is evaluated by testing a laboratory mockup girder and further applied on a field girder. Resulting magnetic signals from both normal and axial Hall-effect sensors are recorded using a newly developed and integrated data acquisition system. Finite element simulations through multi-physics 3D transient analysis aided the development of the new MFL system components, including appropriate magnets strength and dimensions, as well as the verification of the developed system. The effects of lateral reinforcements on nearby section loss are obtained from tests and analyzed with numerical models. Results indicate that the system can successfully disclose magnetic leakage signals at the corrosion zone.

Statistical vibration-based damage localization for the S101 bridge, Flyover Reibersdorf, Austria

This paper is focused on the description and application of an extended version of the Interpolation Method for the damage localization where a statistical characterization of the indicator is proposed. The damage indicator is defined in terms of the probability of exceedance of a detection threshold corresponding to the accepted probability of false alarm. The verification of the accuracy of the novel indicator is carried out with reference to a real case study of a typical example of a European highway pre-stressed concrete road bridge, the S101 Flyover Reibersdorf Bridge built in Austria in the early 1960. Responses to ambient vibration have been recorded on the bridge both in the undamaged and in several different damage scenarios artificially inflicted. In the paper data recorded on the S101 have been used to check the accuracy of damage indicator for the several damage scenarios and its sensitivity to the statistic model assumed to describe the variability of the damage feature.

Low-Frequency Electromagnetic Energy Harvesting from Highway Bridge Vibrations

Abstract This paper focuses on energy harvesting from low-frequency vibrations in bridges via an electromagnetic device. Two pre-stressed concrete highway bridges are considered as case studies. In...

Considerations on the Bearing Capacity of Existing Prestressed Concrete Bridges

Abstract Military actions generally unfold rapidly in different operational environments for which the commanding officer has assess the bearing capacity of the prestressed concrete bridges existing in the country’s road network. The bearing capacity is the maximum weight of the predetermined constitution convoy, which may safely circulate on the bridge, in stable conditions, considering the physical condition of the bridge. The paper shows that the bearing capacity will be assessed only through a technical analysis performed by an authorized expert together with a military engineer specialized in genius. This experts report will compare the initial condition of the bridge to the present one. The initial condition is based on the research of the execution design; the year of elaboration; the standard loadings at the moment; proprieties of the used building materials; execution modality, possible alterations occurring during execution as to the initial project. These data, together with the road traffic census, can be obtained from the company administrating the road network where the bridge is located. The current state to be assessed through analysis, calculation and static loading tests, showing if the capacity of the bridge can to support the increase of traffic military vehicle loading and reduction of the bearing capacity due to fatigue phenomena in the reinforcement. The paper proposes that authorities draw up and approve a standard concerning the verification periodicity of the bearing capacity in the existing prestressed concrete bridges.

Static loading test and analysis of prestressed concrete bridge

In order to test the structural performance for the bridge of Linxi 9th road project, the static test of precast prestressed concrete bridge hollow slab was carried out by four stage static loading method. Under the condition of elastic working, the flexural bearing capacity, crack propagation and relative residual displacement of the main control sections of the hollow slab are mainly investigated. The results of static loading test show that, when the efficiency of static loading test is 97%, the structural calibration coefficient, residual displacement of main measuring points and crack propagation meet the requirements.

Study of Simplified Calculating Model on Friction Correlated Prestress Loss for PC Bridges

The friction correlated loss for prestress takes up a comparative large proportion in the total prestress loss, which is hard to control and brings unsafe factor to the Prestressed Concrete (PC) bridges. For better quantification, a simplified calculating model for friction correlated prestress loss was put forward in a universal way based on comparatively sophisticated prestressing loss method in current code. The determinant simplified coefficients may also provide some references in calculating the friction relevant losses for prestress of the space curve tendon in other PC bridges.

Environmental and Social Impact Assessment of Optimized Post-Tensioned Concrete Road Bridges

Most of the definitions of sustainability include three basic pillars: economic, environmental, and social. The economic pillar has always been evaluated but not necessarily in the sense of economic sustainability. On the other hand, the environmental pillar is increasingly being considered, while the social pillar is weakly developed. Focusing on the environmental and social pillars, the use of methodologies to allow a wide assessment of these pillars and the integration of the assessment in a few understandable indicators is crucial. This article is structured into two parts. In the first part, a review of life cycle impact assessment methods, which allow a comprehensive assessment of the environmental and social pillars, is carried out. In the second part, a complete environmental and social sustainability assessment is made using the ecoinvent database and ReCiPe method, for the environmental pillar, and SOCA database and simple Social Impact Weighting method, for the social pillar. This methodology was used to compare three optimized bridges: two box-section post-tensioned concrete road bridges with a variety of initial and maintenance characteristics, and a pre-stressed concrete precast bridge. The results show that there is a high interrelation between the environmental and social impact for each life cycle stage.

Laboratory and In-Situ Testing of Integrated FBG Sensors for SHM for Concrete and Timber Structures.

Long-term structural health monitoring (SHM) plays an important role in the safety of public transport infrastructure such as bridges or tunnels and warns in the event of any emerging problem. This article describes development and testing of system based on fiber Bragg grating (FBG) sensors that can detect changes in strain and temperature. The first phase of the research has been focused on the development of new fiber optic sensors for the monitoring of concrete structures and their investigation in laboratory conditions. The work also shows novel applicability of the same FBG technology for glulam structures. Mechanical loading tests of the concrete beam as well as glulam beam with embedded sensors were carried out. Data measured by developed fiber optic sensors were compared with the readings from reference sensors as well as with the analytically calculated values. The achieved results proved good agreement between the measured data, analytical data and reference methods. In second phase of the research, the pilot installation of the sensors was carried out on the newly constructed prestressed-concrete bridge. The bridge was monitored throughout pre-stressing phase and monitoring continued after the completion of the construction works. Problems with the fragility of the sensors occurred during the measurements, but the obtained results provide a good basis for further improvement of the system.

Eigenfrequencies of continuous prestressed concrete bridges subjected to prestress losses

The paper presents a numerical procedure to evaluate the consequences of prestress loss on the frequencies of vibration of continuous prestressed concrete (PSC) bridges. The importance of being able to identify an excessive loss of prestressing, caused for instance by the breaking of some strands, is evident considering that currently the majority of collapses occurred in prestressed bridges is due to the stress-corrosion cracking of the prestressing steel.The method allows to solve the structural problem taking into account the following mutually interconnected features: non-linearity of the materials mechanical properties, redistribution of stresses based on the actual flexural stiffness of the beam segments in statically indeterminate structures and loss of prestressing. The application of the proposed procedure to two case studies found in the literature indicates that the variation of the first three eigenfrequencies for a prestress loss of 30% turned out to be in the range 1.5%–2.5%. The procedure could, thus, be included in continuous monitoring systems of PSC bridges that already take into account the frequency variations produced by other causes (temperature, humidity, …) for a timely detection of relevant prestress losses.

Analysis and correction of stress error in construction monitoring of cantilever cast prestressed beam bridge

In order to correct the monitoring stress of long-span prestressed concrete girder more accurately, and consider the characteristics of bridge load gradually applied during cantilever construction, this paper proposes an accurate correction method for monitoring stress of long-span prestressed concrete bridge. Based on the linear creep theory and Bauer boltzmann (L.B oltzman) superposition principle, the invariant elastic mode of traditional calculation isreplaced by the equivalent elastic modulus from load-to-pre-calculation, and the formula of concrete creep, and the time-varying elastic mode is taken into account. The effect of concrete shrinkage and temperature change softer on the real stress value of the structure is accurately corrected by separating and removing stress-free strain from the measured strain. This method is applied to the calculation of the measured stress in the key section of the main beam of a long-span continuous beam of a high-speed railway. The results show that the modified stress value is in good agreement with the theoretical value and the error is significantly reduced, which verifies the reliability and accuracy of the modified method.

Fabrication and Design of Precambered Precast, Prestressed Concrete Bridge Girders

Fabrication and Design of Precambered Precast, Prestressed Concrete Bridge Girders

Effects of prestressing force on natural frequency of prestressed concrete beams considering self-weight

This study investigated the effects of prestressing force on the natural frequency of concrete beams considering changes in the self-weight of the beam. For this, a finite element formulation was derived to account for the increase in the stiffness of a beam-tendon system due to the axial force and deformation induced by prestressing of the tendon. The developed finite element formulation was validated with the data obtained in laboratory experiments. The experimental natural frequencies of the small prestressed concrete (PSC) beam specimens were consistent with those obtained using the proposed method. The first natural frequency increased almost linearly as the prestressing force increased. The proposed method was then applied to four actual PSC bridges typically employed in the field. Different from the laboratory specimens, the first natural frequencies of the actual PSC bridges barely changed or increased with increasing prestressing force. The results of an analytical parametric study showed that the increase in the natural frequency strongly depended on the magnitude of the prestressing force relative to the total weight of the structure. Thus, the variation in the natural frequencies of the actual PSC bridges with high total weight relative to the prestressing force was negligible due to the application of the prestressing force.

Research on the material properties of prestressed concrete girder bridge after exposed to fire

The factors such as maximum temperature, duration, diffusion condition and concrete bursting at high temperature increase the difficulty of obtaining material properties by using temperature. In order to quickly obtain the real performance parameters of the materials of the pre-stressed concrete beam bridge in the post-disaster bridge evaluation, the appearance classification and material test of 32 hollow slabs demolished after the fire of the existing beam bridge in a highway were carried out. The relationship between the commonly used testing indexes and the properties of materials is obtained by measuring the properties of materials after fire. The applicability of these indexes is verified by the ultimate bearing capacity test and finite element simulation. The results show cracking and spalling of concrete at high temperature not only results in significant loss of section, but also significantly reduces the strength of concrete and prestressing steel strand in this area, which leads to the reduction of bearing capacity. When the spalling depth of concrete exceeds 2/3 of the net protective layer of steel strand after overfire, the reduction coefficient of compressive strength and tensile strength of pre-stressed steel wire reaches 0.7, which will seriously affect the ultimate bearing capacity. The normal plain round steel bar can be deviated safely to the design standard value when calculating the ultimate bearing capacity of the structure. The ultimate bearing capacity of the prestressed hollow beam after fire is analyzed by using the reduction relationship between the conventional inspection indexes and the material properties, and the finite element simulation, so as to meet the engineering precision.

Bayesian Prediction of Pre-Stressed Concrete Bridge Deflection Using Finite Element Analysis.

Vertical deflection has been emphasized as an important safety indicator in the management of railway bridges. Therefore, various standards and studies have suggested physics-based models for predicting the time-dependent deflection of railway bridges. However, these approaches may be limited by model errors caused by uncertainties in various factors, such as material properties, creep coefficient, and temperature. This study proposes a new Bayesian method that employs both a finite element model and actual measurement data. To overcome the limitations of an imperfect finite element model and a shortage of data, Gaussian process regression is introduced and modified to consider both, the finite element analysis results and actual measurement data. In addition, the probabilistic prediction model can be updated whenever additional measurement data is available. In this manner, a probabilistic prediction model, that is customized to a target bridge, can be obtained. The proposed method is applied to a pre-stressed concrete railway bridge in the construction stage in the Republic of Korea, as an example of a bridge for which accurate time-dependent deflection is difficult to predict, and measurement data are insufficient. Probabilistic prediction models are successfully derived by applying the proposed method, and the corresponding prediction results agree with the actual measurements, even though the bridge experienced large downward deflections during the construction stage. In addition, the practical uses of the prediction models are discussed.

Partial factor methods for existing structures according to fib Bulletin 80: Assessment of an existing prestressed concrete bridge

AbstractThe assessment of existing reinforced concrete structures is one of the major aspects for engineers and practitioners. In particular, existing infrastructures, as bridges and viaducts, are extensively exposed to environmental actions, materials aging, degradation, and variation of magnitude of traffic loads during their service life. Hence, the assessment of existing structural systems assuming the same criteria conceived for the design (i.e., partial factor method—EN 1990) can be too conservative and, sometimes, may lead to unnecessary and expensive structural interventions. In this context, fib Bulletin 80 defines the partial factor methods suitable for the assessment of existing reinforced concrete structures accounting for their residual service life, information from in situ and laboratory tests, measurements of variable actions and reduced target reliability levels according to both economical and human safety criteria. The methodologies proposed in fib Bulletin 80 have been applied to assess the safety of an existing prestressed reinforced concrete bridge built in 90s and located in Italy. The results are compared to the outcomes from the assessment performed according to EN1990 and, finally, limits and advantages of the methodologies proposed by fib Bulletin 80 are discussed.

Evaluating the Effect of the Compressive Strength Development Factor on Concrete Creep Deformation in Bridge Construction

Abstract Excessive midspan deflection is often observed in large-span prestressed concrete girder bridges. In particular, the deformation caused by shrinkage and creep of concrete is an important part of deflection that often exceeds expectations. To achieve creep deformation control, extending the curing time and postponing the loading age are frequently adopted during construction. This article proposed an approach based on creep experiments with prismatic and beam specimens and viscoelastic model-based finite element analyses to evaluate the effect of the concrete strength development factor on the ultimate creep coefficient in the Comité Euro-International du Béton-Fédération internationale de la précontrainte (CEB-FIP) model. The concrete strength development factor ξcc(t/tu) is defined as the ratio of the mean compressive strength at the loading time to the maximum mean compressive strength obtained in the test. The strategies for targeted regulation and control of ξcc(t/tu) were discussed by establishing an artificial neural networks model for strength prediction from a database provided in our previous work. Uniaxial compressive prismatic specimens and pure bending beam specimens with a span of 5.0 m were used in the experiment for creep behavior observation. A viscoelastic finite element analysis (FEA) model was established based on solidification theory. The FEA model results were verified with measured data for capturing the creep behavior under ambient conditions to obtain reliable long-term creep deformation predictions. Finally, the proposed method was validated with the Xincheng bridge construction for the optimistic loading age determination, and the results indicated good feasibility in girder deflection control.

Field Testing of a Prestressed Concrete Bridge With High Performance and Locally Developed Ultra-High Performance Concrete Girders

Recent research has developed mixture proportions for ultra-high performance concrete (UHPC) using materials primary local to New Mexico, United States of America (USA). In 2017, a two-span bridge was constructed in Anthony, New Mexico, USA consisting of prestressed girders using the locally developed non-proprietary UHPC, for span one, and high performance concrete (HPC), for the second span. Field tests were conducted on the bridge approximately nine months apart to investigate the performance and behavior of the UHPC and provide baseline data for future studies and condition evaluation of the bridge. The load tests consisted of various load configurations utilizing up to four trucks weighing 267 kN on average. The load paths were designed to maximize strains along the length of the bridge and investigate transverse load distributions between girders. The measured results provide a comparison of the behavior and performance of the UHPC and the HPC girders and were also compared to the American Association of State Highway and Transportation Officials (AASHTO) predicted behaviors. This study is one of the first that compares HPC and nonproprietary UHPC bridge performance subjected to the same environmental conditions and vehicular loading. The findings of the study will aid in the development of recommendations incorporating UHPC into design provisions as well as provide meaningful information of the short and long-term performance between the two materials including durability and load distribution.

A Study on Analysis of Long Span Continuous Rigid Frame Bridge

A case study of a large span pre-stressed concrete continuous rigid frame bridge (Ba-Mao-Chong bridge) of GUI DU high speed railway. Finite element program Midas/Civil is used to simulate the construction process and operation phase, the influence of concrete overweight, pre-stressing loss, concrete shrinkage and creep, stiffness loss and other factors that related the long-term deflection of bridge are analyzed. The calculation results show that: (1) The overweight concrete and Bridge deck pavement construction error could cause the bridge long-term deflection increases. (2) The creep coefficient, environment humidity, and other factors on the bridge have significantly influence on long-term mid-span deflection, (3) The beam stiffness reduction could lead to the bridge long-term mid-span deflection increase.

Damage detection under environmental and operational effects using cointegration analysis – Application to experimental data from a cable-stayed bridge

Abstract One of the main challenges that Structural Health Monitoring (SHM) faces when transitioning from academia to real-world applications is the discernment between structural changes due to damage and normal environmental, operational and long-term effects. In this context, a strategy for early damage detection based on multivariate cointegration analysis and statistical process control is proposed. The effects of environmental and operational variations are suppressed using cointegration analysis, being the cointegrating vector estimated following the multivariate Johansen procedure. The cointegrated residuals are then used for novelty detection by means of the Hotelling T2 control chart. The proposed strategy is systematised and is applied to a large prestressed concrete cable-stayed bridge of which 3.5 years of data are available, being the stay-cable forces used as damage sensitive-features. Several damage scenarios are studied involving increasing section loss of the stay cables. The damage intensities that can be detected using the proposed methodology and the available sensory system are quantified.