Continuous Prestressed Concrete Beams Research Articles

Moment redistribution capacity in prestressed concrete continuous beams

In prestressed concrete continuous beams, building code provisions often allow for a reduction in the moment at a critical section (calculated through elastic analysis). This reduction is permitted as long as the moments in all other sections are adjusted to maintain equilibrium and support the designated loads. However, the allowable moment redistribution percentage (MRP) for prestressed concrete beams (PCBs) remains a topic of debate. Many codes currently assign a similar MRP limitation to both PCBs and reinforced concrete beams (RCBs). This approach might be over-simplistic for PCBs due to their unique behaviour. A method for identifying the maximum available MRP is proposed in this article. An in-depth study was conducted on the maximum available MRP of PCBs based on calibrated finite-element models. The results showed that parameters such as the passive reinforcement ratio, steel yield strength, slenderness ratio, eccentricity of prestressing tendons, concrete grade and load pattern, which are not considered in the codes, influence the maximum available MRP to an extent. Using the same permissible MRP as RCBs may thus be inappropriate. An equation is proposed to estimate the maximum available MRP for PCBs.

STUDY ON CONSTRUCTION MONITORING AND CONTROL OF MULTI-SPAN PRESTRESSED CONCRETE CONTINUOUS BEAM BRIDGE

This article focuses on the construction monitoring and control of a pre-stressed concrete continuous beam bridge, consisting of 13 spans. The goal is to ensure that the bridge structure meets the design requirements throughout the entire construction process. By comparing the theoretical and measured values of the bridge’s alignment and stress during the cantilever construction, closure, and completion phases, it can be observed that the deflection deformation of the bridge is generally in agreement with the theoretical calculations. After the completion of the entire bridge, the measured elevations of each section have an error range of -18mm to 20mm compared to the design elevations, which satisfies the specifications. A comparison analysis of the measured and theoretical stress values at the root and mid-span of the cantilever indicates that the stress difference at the root is within the range of -0.2MPa to 0.2MPa, and the stress differences at the mid-span after completion are 0.03MPa (upper) and 0.09MPa (lower), all of which meet the structural design and code requirements. By establishing a gray GM (1,1) model and using gray system theory, the deflection error during the construction process is predicted and controlled. The prediction accuracy of different methods is compared to determine a reasonable prediction method suitable for long-span pre-stressed continuous beam bridges, providing reference for similar engineering projects.

Arch Action Model for the structural assessment of existing prestressed concrete bridges

AbstractStructural assessments of existing older prestressed concrete bridges according to the currently applicable standards and guidelines in Germany generally reveal significant deficiencies in shear reinforcement. Large‐scale tests within the scope of research activities commissioned by the Federal Highway Research Institute (BASt) were carried out at TU Dortmund University to analyze the shear load‐bearing behavior of continuous prestressed concrete beams in more detail. The Arch Action Model (AAM) was derived from the Simplified Arch Action Model (SAAM) to provide a possible analysis method for determining shear contribution from concrete. Thus, the shear capacity of prestressed beams can be determined in a more realistic manner than using the truss model underlying the current state of standardization. The paper at hand provides information and explanations about the SAAM and AAM with regard to their application to real‐world structures for structural bridge assessments.

Experimental investigations of flexural and shear behavior of continuous prestressed HSC beams under repeated loads

The results of an experimental study into the flexural and shear conduct of continuous two span unbonded posttensioned high strength concrete beams subjected to static and a limited number of repeated loading cycles are presented in this paper. The experimental program comprising testing and experimentation of four continuous unbonded posttensioned high strength beams with a total length (4300) mm. The main objective of this study was to see how the strength and serviceability of continuous prestressed concrete beams were affected by restricted repeated loading cycles. As a result, these beams were split into two similar groups. The first set consisted of two beams to study the flexural behavior. The second set consisted of two beams to study the shear behavior. For each set one tested under static loads and the second tested under repeated loads. They were subjected to two concentrated loads in the middle of each span loads up to destruction. It was determined that the repeated load ranged between 0.4 and 0.6 of the ultimate load generated by the static test. Immediately following the ten cycles, the load was withdrawn, and the beams were subjected to a monotonic static test until failure was achieved. Recorded the cracking and ultimate load capacity, midspan deflections, and crack widths. The experimental results explained that the ultimate flexural and shear strength for beams that are tested under repeated loads is a little reduced (1.7%) and (3.9%) comparing with the strength of the identical beams under monotonic static loading and increasing the ultimate deflection after ten cycles of repeated loading, decreased about (5.3%) and (15.1%) for flexural set and shear set, respectively.

The Train-Bridge Coupled Vibration Analysis of a Long-Span Prestressed Concrete Continuous Beam Bridge under Creep Deformation Effect

The track smoothness of high-speed railroads is severely limited to ensure train performance. The concrete continuous girder bridge is deformed to influence the smoothness of the bridge decks and track caused by creep bulge. There is a need to research the impact of beam creep on the dynamical response of bridge and train operation safety. This paper used Midas software to calculate the long-term deformation of large-span prestressed concrete continuous beam bridges under concrete creep and shrinkage. The train-bridge coupled system was established by adopting self-programming software. Thereafter, the large-term deformation results of the main girder are considered as track irregularity input into the vibration equation of the train-bridge system. The safety of the train operation was evaluated by calculating the dynamic response of the bridge and analyzing the criteria of train running safety. It was shown that the indicators of the large-span bridge are within the allowable code values under all working conditions. The bridge deformation under creep has an impact on the displacement and acceleration response of the bridge when a high-speed train passes through. There is no noticeable impact of creep deformation on the operational performance of trains. Nevertheless, the criteria for assessing the safety of trains’ operation, such as derailment factor, wheel load differences, lateral wheel forces, and vehicle acceleration, have been increased.

Structural behavior of continuous two-span prestressed concrete T beams with different tendon profiles

Approximately half-scale tests were conducted to inves­tigate the behavior of indeterminate prestressed concrete T beams with two different unbonded tendon profiles. Three T beams were employed for the tests: T beam specimen 1 (TB1) was the control specimen and had no eccentricity at the interior support and T beam speci­mens 2a and 2b (TB2a and TB2b) had eccentricity at the interior support. The results indicate that the specimens with eccentricity at the interior support had a greater number of cracks than the control specimen at the ten­sion zone of the support. This finding was explained by hyperstatic moment reducing the negative moment in the control. The trend in the slope of the strain-applied load tension relationship was different in TB1 than in TB2a due to a difference between the specimens in terms of the distance from the extreme compression fiber to the centroid of reinforcement at the support. Although the interior support was a roller with no vertical restraint, hyperstatic moment at the support occurred due to a cold welding effect, creating a partial roller condition. The hyperstatic action then decreased as the loading was increased. The authors conclude that the effect of hyperstatic moment should be accounted for in the calculation of concrete stress at the service level for continuous prestressed concrete beams with unbonded tendons and a vertically unconfined support condition.

Shear strengthening of continuous prestressed concrete beams with precast SIFCON laminates subjected to monotonic and repeated loads

Slurry Infiltrated Fibre Concrete (SIFCON) is one of the recently developed construction material that can be considered as a special type of high performance fibre reinforced concrete (HPFRC) with higher fibre content. This study describes the findings of an experimental research to determine the contribution of Precast SIFCON Laminates to the enhancement of the shear strength of continuous prestressed concrete beams. Precast SIFCON Laminates were used in the investigation. It was decided to test six two-span prestressed high strength concrete continuous beams with rectangular cross-sections, each of which had a rectangular cross section. In this case, two beams were left un-enhanced as a control, and the other four beams were strengthened with varied arrangements of Precast SIFCON Laminates. The variables chosen were several wrapping strategies for the Precast SIFCON Laminates, which were then tested. The aim was to develop a better understanding of the shear contribution of Precast SIFCON Laminates and to investigate the effect of repeated loading. The results indicate that the strengthening the maximum shear regions with precast SIFCON laminates glued by epoxy resin led to improve the shear behavior the delay in first crack appearance time reached (26.4%−105.7%), Increased the ultimate shear capacity of the tested beams (19.2%–46.5%), The improvement in stiffness about (94.5%–144.9%) and the Experimental results explained that the ultimate shear strength for beams that are tested under repeated loads is a little reduced (2.2%–3.8%), comparing with the strength of the same beams under monotonic static loading.

Moment redistribution versus neutral axis depth in continuous PSC beams with external CFRP tendons

The neutral axis depth is adopted by many codes of practice as an indicator of flexural ductility to quantify moment redistribution in continuous prestressed concrete (PSC) beams. Moment redistribution, however, does not only depend on ductility but also on differences in stiffness along the length of the beam. Therefore, the effectiveness of using solely the neutral axis depth for redistribution quantification needs to be further evaluated. This study examines moment redistribution against neutral axis depth in two-span PSC beams with external CFRP tendons by applying a validated finite element model. The main variable is the content of non-prestressed reinforcement either at the positive or negative moment zone to generate varying stiffness differences between critical sections. The study shows that the use of neutral axis depth as a key parameter is inadequate when quantifying moment redistribution in these beams. Modifications of CSA, BSI and EC2 equations are proposed by introducing a parameter reflecting the impact of stiffness difference. The proposed equations show much better fit to the actual redistribution than that provided by equations in current design codes.

Response of continuous concrete beams internally prestressed with unbonded FRP and steel tendons

This paper analyzes the global behavior of two-span continuous prestressed concrete beams with internal unbonded fiber reinforced polymer (FRP) and steel tendons. A nonlinear model is introduced and calibrated by the experimental results of unbonded prestressed specimens. Aramid and carbon fibers are used as composite tendons. The tendon area varies from 200 to 1700mm2 so as to generate a wide range of prestressing reinforcement index. The analysis shows that rupture of unbonded FRP tendons is unlikely to take place even at a very low prestressing reinforcement index. The type of unbonded tendons has practically no influence on the cracking mode and moment redistribution while it has limited effects on the development of deformation, nonprestressed steel stress and neutral axis depth. The effect of prestressing reinforcement index on the structural response is important. The ACI code may overestimate the ultimate stress in unbonded tendons in continuous beams at a low prestressing reinforcement index while it is conservative in predicting the permissible moment redistribution. The results also demonstrate that the type and amount of auxiliary bonded bars affect significantly the member behavior.

Behaviour of continuous prestressed concrete beams with external tendons

External prestressing has been applied to both new construction and retrofitting of existing reinforced and prestressed concrete structures. Continuous beams are preferred to simply supported beams because of economy, fewer movement joints and possible benefits from moment redistribution. However, this paper argues that continuous prestressed concrete beams with external unbonded tendons demonstrate different full-range behaviour compared to reinforced concrete (RC) beams. Applying the same design approach for RC to external prestressing may lead to design with a lower safety margin. To better understand the behaviour of continuous prestressed concrete beams with unbonded tendons, an experimental investigation is performed in which nine such specimens are tested to failure. The full-range behaviour is investigated with reference to moment-curvature relationship and moment redistribution. The amounts of moment redistribution measured in the experiments are compared with those allowed by BS 8110, EC2 and ACI 318. Design equations are also proposed to estimate the curvature ductility index of unbonded prestressed concrete beams.

Shear tests on continuous prestressed concrete beams with external prestressing

AbstractAccording to current design codes, many existing road bridges exhibit shear capacity deficits. This is partly due to increased traffic loads and partly due to changes in the code provisions. In order to extend the service lives of these bridges, either refined design approaches may be used or strengthening measures performed. This paper describes the results of experimental investigations into how additional external prestressing influences the shear capacity of continuous prestressed concrete beams. Within the research project, six shear tests were performed on three test beams with parabolic internal post‐tensioning and additional, variable external prestressing. The aim of the project was to determine the effect of external prestressing on the shear capacity of existing bridges, and whether current design approaches lead to conservative results when used for recalculating existing bridge structures.

Numerical modelling of nonlinear behaviour of prestressed concrete continuous beams

The development of a finite element model for the geometric and material nonlinear analysis of bonded prestressed concrete continuous beams is presented. The nonlinear geometric effect is introduced by the coupling of axial and flexural fields. A layered approach is applied so as to consider different material properties across the depth of a cross section. The proposed method of analysis is formulated based on the Euler-Bernoulli beam theory. According to the total Lagrangian description, the constructed stiffness matrix consists of three components, namely, the material stiffness matrix reflecting the nonlinear material effect, the geometric stiffness matrix reflecting the nonlinear geometric effect and the large displacement stiffness matrix reflecting the large displacement effect. The analysis is capable of predicting the nonlinear behaviour of bonded prestressed concrete continuous beams over the entire loading stage up to failure. Some numerical examples are presented to demonstrate the validity and applicability of the proposed model.

A comparative study of continuous beams prestressed with bonded FRP and steel tendons

This paper presents a numerical investigation of the performance of continuous prestressed concrete beams with bonded fiber reinforced polymer (FRP) and steel tendons. A finite element model has been developed and is validated against the available test data. A numerical test is carried out on two-span continuous bonded prestressed concrete beams. Three types of tendons are considered for a comparative study: aramid FRP (AFRP), carbon FRP (CFRP) and prestressing steel. Various levels of ωp (reinforcement index of prestressing tendons) are used. The results indicate that, with increasing ωp, the failure mode of FRP prestressed concrete beams would transit from tendon rupture to concrete crushing while the crushing failure always takes place in steel prestressed concrete beams. Moreover, FRP tendons mobilize significantly different behavior regarding the crack pattern, deformation characteristics and neutral axis depth compared to steel tendons. The moment redistribution at ultimate in AFRP prestressed concrete beams is comparable to that in steel prestressed concrete beams while, at a low ωp level, CFRP tendons register obviously lower redistribution than steel tendons.

Experimental study on moment redistribution of external prestressed concrete continuous beams

Experimental study on moment redistribution of external prestressed concrete continuous beams

The Linear Monitoring Analysis of PC Continuous Beam Bridge

According to the structure and construction characteristics of prestressed concrete (PC) continuous beam bridge and combined with the construction monitoring method of continuous beam bridge, this paper introduces the girder deflection test technology and method of prestressed concrete continuous box girder bridge, also analyzes the various factors which affect the linear monitoring. And draw the conclusion through the analysis of the deflection and linear monitoring of LinGang big bridge.

MIDAS-Based Finite Element Analysis of the Short Line Method of the Precast Segmental Bridge Construction

This paper studies the precast and cantilever erection process of pre-stressed concrete continuous beam bridge alignment control in short line method, basis on the construction of a light rail. Various stages of bridge construction performed on simulation analysis and calculated by the finite element software MIDAS, concluded the ultimate internal force and deformation values, and the maximum deformation are within the scope of design elevation deviation 20 mm allowed, as to achieve the target of bridge assembly.

Factors governing the fire response of bonded prestressed concrete continuous beams

Results from fire resistance experiments on nine bonded prestressed concrete (PC) continuous beams are presented in this paper. The test variables included concrete cover thickness, load level, degree of prestressing and effective prestress. Data from the experiments are utilized to study the effect of critical parameters on thermal and structural response of bonded PC continuous beams under fire conditions. Test results show that concrete cover thickness, load level, degree of prestressing and fire induced secondary moments have significant influence on the fire resistance of bonded PC beams. Specifically fire induced secondary moments increase the total moments at intermediate supports by as much as 1.6 times of that due to imposed external loading under ambient conditions. It is also shown that the fire resistance of PC continuous beams is significantly higher than similar PC simply supported beams. These critical factors are to be considered for evaluating the fire resistance of PC continuous beams under fire conditions.

Identification of Elastic Modulus and Effective Pre-Stress Based on Inversion Theory

Due to vehicle load, shrinkage, creep, temperature and other factors, the strength and stiffness degenerate increasingly for the pre-stressed concrete continuous beam bridge in service. The problem, such as cracking, excessive deflection in the mid-span caused by the deterioration of the elastic modulus and pre-stress, has a direct impact on the usability, durability and security. To solve the problem mentioned above, according to the monitored deflection of the bridge in service at different time, the elastic modulus and the effective pre-stress are evaluated by establishing the inversion analysis model based on the inversion theory.

Prestressed Concrete Continuous Beam Bridge Span Arrangement and Structure Size Proposed Analytical

By analyzing the bridge structure in the course of the dead load and live load, taking into account different load safety factor for load combinations that will limit state as a result of the combination of two kinds of forces calculated tendon force estimates, estimate the various sections of the steel beam, in accordance with certain requirements of the steel beam is a good layout, construction and consider re-simulate prestress for the role of the second combination, the process of the construction and use of a cross-sectional strength checking, stress and deformation checking checking.

Study on Internal Force Effect of a High-Speed Rail (40+56+40) m Prestressed Concrete Continuous Beam Bridge

The continuous beam bridge is a kind of bridge type used widely on the project. With the design theory and construction technology, prestressed concrete continuous beam bridge shown strong vitality. This design is a high-speed rail (40+56+40) m prestressed concrete continuous beam bridge design, whose width is 12.2m and its maximum Design speed is 300km/h. The form of the railway is double line which is 4.8m far away, and the cross-sectional slope is 2%.ZK load was applied on the bridge. A three-span P.C continuous Beam structure with variable cross-section is used in this bridge. The girder body adopts single cell and single box, the height of beam takes quadratic parabola relation, which is 5m high at the middle fulcrum, while at the side fulcrum and the mid-span is 2.5m. The design uses Midas/Civil to establish the finite element model that is reasonable and simple, analyzing the structure behavior of the girder body under loading, especially the internal forces of bridge structure under dead load, live load and additional force.