Prestressed Concrete Bridge Girders Research Articles

Design and Application of PC Composite Box-Girder Bridge with Corrugated Steel Webs

The structure characteristic of prestressed concrete(PC) composite box-girder with corrugated steel webs is introduced, and the advantage is shown compared to PC girder bridge. Design of PC composite girder bridge with corrugated steel webs is introduced, contents including corrugated steel webs, shear connector, etc. The domestic application and development of PC composite box-girder bridge with corrugated steel web is reviewed, and part of the typical bridges combined with corrugated steel web PC box-girder are listed. On behalf of PC composite box-girder bridge with corrugated steel web, Shandong Juancheng Yellow River Bridge is introduced in detail. At last, the future of this type of bridge is prospected.

Investigation of Extreme Environmental Conditions and Design Thermal Gradients during Construction for Prestressed Concrete Bridge Girders

Current AASHTO specifications provide engineers with a temperature gradient across the depth of the cross section to predict the vertical thermal behavior of bridges. This gradient is based on one-dimensional heat flow and does not account for change in the cross section, as found in prestressed concrete girders, nor does it account for thermal effects on the sides of the girder. Furthermore, the current specifications do not provide the transverse temperature gradient that is needed to predict the lateral thermal behavior of the girders, especially during construction, before the placement of the bridge decks. To determine the transverse and vertical temperature gradients in prestressed concrete girders, experimental and analytical studies were conducted on a prestressed BT-63 concrete girder segment. The analytical results were found to be in good agreement with experimental measurements. The analytical model was then used to determine the seasonal temperature gradients in four standard PCI girder sections at selected cities in the United States. On the basis of these findings, vertical and transverse temperature gradients were developed to aid engineers in predicting the thermal behavior of prestressed girders during construction.

Graphical Assessment for Span Ranges of PSC Girder Bridges

Although the prestressed concrete (PSC) girder bridge is known to be more economical than other types of bridges in short and medium spans, a longer span has also been achieved by applying several strategies. This paper presents a systematic procedure that can be used to assess the effects of these strategies on the span. The proposed scheme adopts a graphical approach that represents a relationship between the number of prestressing tendons and the span and is derived on the basis of stress assessment equations of the girder at each stage of fabrication and in service. A quantitative evaluation for the extension of the span is performed by adopting a sample bridge. A number of advantages of the proposed scheme are apparently shown for determining why and how each strategy contributes to the span extension and for suggesting further improvement for a longer span. The results imply that increasing the strength of the girder, making the girders continuous, multistage prestressing, and the decked PSC girder are very effective.

Reliability-Based Dynamic Load Allowance for Capacity Rating of Prestressed Concrete Girder Bridges

The current highway bridge design in the United States follows the AASHTO-LRFD specifications, which prescribe a dynamic load allowance, IM, of 0.33 for the dynamic effect of truck/tandem loading. Studies have shown that the IM value prescribed by the LRFD code may underestimate this dynamic effect under poor road surface conditions (RSCs). One reason for this underestimation is that the IM value employed in the AASHTO specifications was obtained from the statistical properties of the IM relative to average RSC, as defined by the ISO 1995 standards. In addition, the IM, which is a random variable with certain statistical properties, was modeled as a deterministic constant in the code calibration process. In this paper, the reliability indexes of a selected group of prestressed concrete girder bridges, designed following the AASHTO-LRFD code, are calculated by modeling the IM explicitly as a random variable for different RSCs. It is found that although the calculated bridge reliability indexes are usually above the target reliability index value of 3.5 under above-average RSCs, they can be significantly below the target value of 3.5 when the RSCs are below average. Following the load rating procedure proposed by the AASHTO load and resistance factor rating (LRFR) manual, it is also found that the code-employed IM value may overestimate the rating factors when RSCs are below average. Based on these results, appropriate IM values are suggested for different RSCs to achieve a consistent target reliability index and a reliable load rating. The results presented in this paper are particularly valuable for the rating of existing prestressed concrete girder bridges, for which the actual RSCs can be directly evaluated. The RSCs must be properly taken into account to accurately estimate the actual safety of the considered bridge.

Residual Prestress Forces and Shear Capacity of Salvaged Prestressed Concrete Bridge Girders

Seven prestressed concrete bridge girders that had been in service for 42 years, and represented two span lengths and reinforcement designs, were tested to determine their effective prestress force and ultimate shear capacity. A cracking moment test was used to determine the effective prestress force in the girders. The measured effective prestress force was compared with calculated values according to the AASHTO LRFD prestress loss equations to investigate their adequacy. The AASHTO refined method was shown to provide the most accurate results to within 10% of the measured values. An ultimate shear test was also performed on two of the girders. An external load was applied near the support and increased until the girder failed in shear. The various procedures in the AASHTO LRFD specifications were compared with the measured results. The AASHTO simplified procedure predicted only 51% and 39% of the average measured shear capacity for the short and long span girders, respectively. The strut-and-tie models were found to estimate the shear capacity more accurately. The AASHTO refined method was shown to provide the most accurate results.

Optimization on Closure Scheme of Multi-Span Prestressed Concrete Box-Girder Bridge

The stress state of finished bridge and service stage is influenced by various closure schemes in cantilever construction of multi-span prestressed concrete box-girder bridge. Two typical bridges—multi-span prestressed concrete continuous rigid frame bridge and girder bridge are investigated, The stress state in different closure schemes are analyzed using finite element(FE) analysis. Meanwhile, compared the healthy monitoring data, it has been found that taking the closure sequence from side span to middle span in cantilever construction of multi-span prestressed concrete box-girder bridge can lower stress of girder and pier in finished bridge stage, as well as reducing deformation of girder in service stage. Hence, the closure sequence from side span to middle span is more suitable for cantilever construction of multi-span prestressed concrete box-girder bridge.

Behavior of instrumented prestressed high performance concrete bridge girders

A comprehensive monitoring of the behavior of four prestressed high performance concrete (HPC) bridge girders, with higher compressive strength, during construction and while in-service, is presented. The monitoring program covered instrumentation and monitoring of a series of four girders during the casting operation, after construction, under the effects of traffic and thermal loads, as well as under controlled load conditions. Information regarding transfer length, prestress loss, heat of hydration, compressive strength, modulus of elasticity (MOE), modulus of rupture (MOR), creep, shrinkage, coefficient of thermal expansion, and chloride permeability of the concrete used is obtained and presented. Furthermore, the in-service monitoring and controlled load tests and details regarding thermal expansion, bridge stiffness, and load distribution factors are also presented. This paper provides details of testing of the concrete properties and field instrumentation of the bridge girders as well as a discussion of service level monitoring and controlled load testing. Comparisons are made between experimental and theoretical results.

Space Frame Latice Model for Stress Analysis of Bridge

This article presents a space frame lattice model for the analysis of stress of entire cross-section of bridge. The authors focused on analyzing the relatively weaker position of stress in box-girder section, using as an example the Xintan Bridge over the Qijiang River in Chongqing, China. The Xintan Bridge has a continuous prestressed concrete rigid frame with 75+130+75 m span. They calculated and analyzed the shear stress and principle tensile stress of the box girder cross-section in this bridge, using an innovative layout method of mixed internal and external prestressed tendons. They conclude that the space frame lattice model is accurate for calculating the stress state of a bridge. This model can simulate the process of long-term cracking as well as deflection of large-span pre-stressed concrete girder bridges.

Flexural Behaviors of Damaged Full-Scale Highway Bridge Girder Strengthened by External Post Tension

Problem statement: Prestressed Concrete (PC) I section girder with Re inforced Concrete (RC) topping slab has been widely applied to long span bridge girders for several years. A bridge girder is subjected to severe conditions c aused by an aggressive environment and overloading. A crack can be initiated and propagate when the tensile stress exceeds the tensile strength of concrete due to overloading. Deteriorat ion of the girder may be caused by a wide crack due to corrosion of the reinforcement and other mec hanisms. Prestressing force and flexural stiffness (EI) of PC-I section girder are reduced d epending on the level of overloading and the corresponding damage. Approach: Full scale tests of Type III AASHTO highway girder with a 20 cm thick RC topping slab were performed to study both the degradation process due to overloading and also the effects of external post-t ension in the recovery of structural performance of a damaged highway PC bridge girder. Results: The results showed that degradation, loss of internal prestressing force in the PC-I girder and flexural stiffness of the composite girder depend directly on Damage Index (DI) expressed in terms of permanent deformation. External post tension with three levels of prestressing forces wa s applied to strengthen the damaged girder to recover its structural performance, flexural stiffn ess and strength. A simplified analytical model, verified by test results, was developed to predict flexural behaviors, loss of internal prestressing force and flexural stiffness of highway girder due to overloading and also structural performance of the strengthened girder. Conclusion: It was found that the required external prestressi ng force to effectively recover structural performance of a damaged girder depended directly on the damage index of the girder.

Differences between Calculated and Measured Long-Term Deflections in a Prestressed Concrete Girder Bridge

The monitoring of five precast, prestressed bridge girders during fabrication and service provided the opportunity to observe changes in camber over time. These camber variations were compared with corresponding strain and temperature measurements. Each of the girders was cast outside during the winter. As a result, the cold ground acted as a heat sink, and a significant temperature gradient existed during curing of each of the instrumented girders. These temperature gradients are believed to have caused the wide range in the short- and long-term cambers. A procedure to calculate the effect that curing temperatures have on girder camber is presented. In addition, the measured camber values are compared with predicted values using the multiplier method, improved multiplier method, and a detailed time-step method. It was found for the long-span girders that the measured camber values were on average within 10% of the predicted values using the detailed time-step method, but ranged from 22% lower to 27% higher for the simpler methods.

Shear capacity of continuous pre-stressed concrete bridge girders with different static systems through vertical prestressing

Shear strength requirements are not met by some existing bridge girders, and so study of this strength seems essential. Pre-stressed concrete bridge girder shear strength with and without vertical prestressing is studied in this paper. First, several prestressed concrete beam models are selected and analyzed using the finite-element method. In this regard modeling validity is evaluated based on some tests performed on an existing bridge girder in Switzerland. In the study's second part, several beam specimens are built and tested and their load-deformation curve and cracking pattern are studied. The slope of shear cracks and shear reinforcement ratio are investigated using all numerical and experimental studies and the effect of horizontal and vertical pre-stressing on the noted parameters is evaluated. The findings should be of interest to researchers as well as practicing engineers involved in prestressed concrete beam analysis and design.

In-Service Shear and Moment Girder Distribution Factors in Simple-Span Prestressed Concrete Girder Bridge

An optical fiber monitoring system was designed and built into the I-25 bridge at the Dona Ana exit in Las Cruces, New Mexico. The bridge is a simple-span, high-performance prestressed concrete girder bridge. The girders are six BT-63 high-performance-concrete girders with a span length of 112.5 ft (34.2 m). Fiber Bragg grating optical fiber deformation sensors along with thermocouples were embedded in the girders during fabrication. Sensors were installed along the top and bottom flanges and at midspan and quarter spans. Pairs of crossed sensors in a rosette configuration were embedded in the webs at the supports. The bridge was monitored for 2 years, from transfer of the prestressing force through service. The sensor data were analyzed to evaluate shear and moment girder distribution factors, in situ material properties, pre-stress losses, camber, dynamic load allowance, and bridge performance under traffic loads. This study focuses on the lateral load distribution in the bridge. Shear and moment girder distribution factors are obtained from a finite element model, sensor measurements under a live load test, as well as regular traffic loading and compared with the values specified by the AASHTO standard specifications (2002) and the AASHTO load and resistance factor design specifications (2007).

Improved Longitudinal Joint Details in Decked Bulb Tees for Accelerated Bridge Construction: Fatigue Evaluation

This companion paper focuses on an investigation of improved continuous longitudinal joint details for decked precast prestressed concrete girder bridge systems. Precast concrete girders with an integral deck, which are cast and prestressed with the girder, provide benefits of rapid construction along with improved structural performance and durability. Despite these advantages, the use of this type of construction has been limited to isolated regions of the United States. One of the issues limiting more widespread use is the perceived problem with durability of longitudinal joints used to connect adjacent girders. Four full-scale slabs connected by No. 16 (#5) headed reinforcement detail using a 152 mm (6 in.) lap length were fabricated and tested. An analytical parametric study was conducted to provide a database of maximum forces in the longitudinal joint. These maximum forces are then used to determine the loading demand necessary in the slab testing due to the service live load. Static and fatigue te...

Vehicle Signal Analysis Using Artificial Neural Networks for a Bridge Weigh-in-Motion System

This paper describes the procedures for development of signal analysis algorithms using artificial neural networks for Bridge Weigh-in-Motion (B-WIM) systems. Through the analysis procedure, the extraction of information concerning heavy traffic vehicles such as weight, speed, and number of axles from the time domain strain data of the B-WIM system was attempted. As one of the several possible pattern recognition techniques, an Artificial Neural Network (ANN) was employed since it could effectively include dynamic effects and bridge-vehicle interactions. A number of vehicle traveling experiments with sufficient load cases were executed on two different types of bridges, a simply supported pre-stressed concrete girder bridge and a cable-stayed bridge. Different types of WIM systems such as high-speed WIM or low-speed WIM were also utilized during the experiments for cross-checking and to validate the performance of the developed algorithms.

Improved Longitudinal Joint Details in Decked Bulb Tees for Accelerated Bridge Construction: Concept Development

This paper focuses on an investigation of improved continuous longitudinal joint details for decked precast prestressed concrete girder bridge systems. Precast concrete girders with an integral deck that is cast and prestressed with the girder provide benefits of rapid construction along with improved structural performance and durability. Despite these advantages, use of this type of construction has been limited to isolated regions of the United States. One of the issues limiting more widespread use is a perceived problem with durability of longitudinal joints used to connect adjacent girders. This paper presents the results of a study to assess potential alternate joint details based on constructability, followed by testing of selected details. Seven reinforced concrete beam specimens connected with either lapped headed reinforcement or lapped welded wire reinforcement were tested along with a specimen reinforced by continuous bars for comparison. Test results were evaluated based on flexural capacity, curvature at failure, cracking, deflection, and steel strain. Based on the survey and the experimental program, a headed bar detail with a 152 mm 6 in. lap length was recommended for replacing the current welded steel connector detail. DOI: 10.1061/ASCEBE.1943-5592.0000067 CE Database subject headings: Reinforcement; Joints; Bridge construction; Bridge decks. Author keywords: Lap length; Headed reinforcement; WWR; Longitudinal joint; Decked bulb tee; Accelerated bridge construction.

Experimental Determination of Resistance Characteristics of Support Details Used in Prestressed Concrete Bridge Girders

Static load tests were performed on support details used at the ends of prestressed concrete pedestrian bridge girders to determine the resistance characteristics of girder supports in the direction perpendicular to the longitudinal axis of the girders. The specimens tested represent support details that have also been widely used in prestressed concrete highway bridges in Minnesota and in other states. Two specimens, one representing the free-end detail and one representing the restrained-end detail were subjected to a combination of vertical and lateral loads. The applied loading was intended to simulate the loading conditions to which the girder ends would be subjected in the event of an over-height vehicle collision with the bridge. The tests revealed two types of lateral load resisting mechanisms depending on the type of support detail. The specimen with the free-end detail resisted the lateral loading through sliding friction between the components of the support assembly. Deformation of this specimen was a combination of shear deformation of the bearing pad and sliding of various support components. The restrained-end detail exhibited larger lateral load capacity than the free-end detail due to the resistance provided by the anchor rods that were intended to prevent the lateral movement of the girder ends. Failure of the specimen with restrained-end detail was due to the concrete breakout and bending of the anchor rods.

Vibration and impedance monitoring for prestress-loss prediction in PSC girder bridges

A vibration-impedance-based monitoring method is proposed to predict the loss of prestress forces in prestressed concrete (PSC) girder bridges. Firstly, a global damage alarming algorithm using the change in frequency responses is formulated to detect the occurrence of damage in PSC girders. Secondly, a local damage detection algorithm using the change in electro-mechanical impedance features is selected to identify the prestress-loss in tendon and anchoring members. Thirdly, a prestress-loss prediction algorithm using the change in natural frequencies is selected to estimate the extent of prestress-loss in PSC girders. Finally, the feasibility of the proposed method is experimentally evaluated on a scaled PSC girder model for which acceleration responses and electro-mechanical impedances were measured for several damage scenarios of prestress-loss.

Repair of Bridge Girder Damaged by Impact Loads with Prestressed CFRP Sheets

A sound repair on a 40 year old four-span prestressed concrete girder bridge is performed with an innovative strengthening method using prestressed carbon fiber reinforced polymer (CFRP) sheets. In fact, this application is the first North American field application of its type. An adequate repair design is conducted based on the American Association of State Highway and Transportation Officials Load Resistance Factor Design (AASHTO LRFD) and the Canadian Highway Bridge Design Code. To ensure the feasibility of the site application using prestressed CFRP sheets, tests are conducted and closed-form solutions are developed to investigate the behavior of the anchor system that is necessary for prestressing the CFRP sheets. A full-scale finite-element analysis (FEA) is performed to investigate the flexural behavior of the bridge in the undamaged, damaged, and repaired states. The AASHTO LRFD exhibits conservative design properties as compared to the FEA results. The repaired bridge indicates that the flexural...

Diaphragm Effects of Prestressed Concrete Girder Bridges: Review and Discussion

Construction of intermediate diaphragms is an extra cost financially and in scheduling. Practice of intermediate diaphragms in prestressed concrete bridges is still controversial, and the practice in each state is different. This paper presents a review of the state-of-the-art practice regarding intermediate diaphragms of prestressed concrete bridges. Through a critical review, issues regarding the intermediate diaphragm effects on bridge performance are discussed. It is found that the ways to model the intermediate diaphragms make a significant difference on the results, and it is crucial to quantify the actual stiffness contribution of the intermediate diaphragms. Through field inspections, more specific information has been acquired for the current practice in Louisiana. This information is of invaluable help for developing finite element analysis and for the research team to make sound recommendations regarding the practice of intermediate diaphragms. The presented information will also help other states in examining the functions of intermediate diaphragms and in developing their policies of practice.

Effectiveness of Continuity Diaphragm for Skewed Continuous Prestressed Concrete Girder Bridges

Continuity diaphragms have caused difficulties in detailing and construction when used in bridges composed of prestressed concrete girders supported on skewed bents. This paper investigates the effect of full-depth continuity diaphragms on the deflection of, and stress in, skewed precast, prestressed concrete girders. Bridge models used had the following parameters: girder type and spacing, bridge skew angle, span length, and diaphragm type. As either skew angle increases or girder spacing decreases in these types of bridges, construction becomes more difficult and effectiveness of the diaphragms becomes questionable. If diaphragms are determined to be unnecessary as an outcome of this research, the construction and maintenance costs of these types of bridges could possibly be reduced. The aims of this research were to determine the need for continuity diaphragms in skewed, precast, prestressed concrete girder bridges; study the load transfer mechanism through full-depth continuity diaphragms; and determine the minimum skew angle at which a diaphragm becomes ineffective in performing its function.