Prestressed Concrete Beams Research Articles

Research on static and dynamic behaviors of PC track beam for straddle monorail transit system

In this study, in-situ static and dynamic tests of four pre-stressed concrete (PC) track beams with different span lengths and curvatures in a straddle monorail transit system were reported. In the static load tests, the strain and deflection at critical sections of the PC track beams were measured to determine the load bearing capacity and stiffness. The dynamic responses of strain, deflection, acceleration, and displacement at key positions of the PC track beams were measured under different train speeds and train loads to systematically study the dynamic behaviors of the PC track beams. A three-dimensional finite element model of the track beam-vehicle coupled vibration system was established to help understand the dynamic behavior of the system, and the model was verified using the test results. The research results show that the curvature, span length, train speed, and train loads have significant influence on the dynamic responses of the PC track beams. The dynamic performance of the PC track beams in the curve section is susceptible to dynamic loads. Appropriate train loads can effectively reduce the impact of the train on the PC track beam. The PC track beams allow good riding comfort.

Development and application of a hybrid prestressed segmental concrete girder utilizing low carbon materials

A hybrid prestressed segmental concrete (HPSC) girder utilizing low carbon materials was developed in this paper. This paper introduces the hybrid prestressing concept of pre-tensioning the center segment and assembling all segments by post-tensioning, as well as the development process of the low carbon HPSC girder. First, an optimized mix proportion of 60 MPa high strength concrete containing high volume blast furnace slag was developed, then its mechanical properties and durability characteristics were evaluated. Second, the mechanical properties of 2,400 MPa high strength prestressing strands and the transfer length characteristics in pre-tensioned prestressed concrete beams were evaluated. Third, using those low carbon materials and the hybrid prestressing concept, the HPSC girders were manufactured, and their structural performance was evaluated. A 30-m long HPSC girder for highway bridges and a 35-m long HPSC girder for railway bridges were designed, manufactured, and structurally confirmed as having sufficient strength and safety. Finally, five 35-m long HPSC girders were successfully applied to an actual railway bridge for the first time.

Shear behavior of concrete beams pre-stressed with carbon fiber reinforced polymer tendons

This article presents experimental and numerical studies on the shear behavior of reinforced concrete beams pre-stressed with carbon fiber reinforced polymer tendons. A total of 23 beams were tested to analyze the failure mode and shear performance of pre-stressed concrete beams. Experimental results revealed that there were two typical shear failure modes, that is, shear compression failure and inclined compression failure. Next, the experimental and numerical results were used to explore factors influencing the failure mode and the shear behavior of the concrete beams, including the type of pre-stressing tendons, stirrup ratio, shear span–depth ratio, number of pre-stressing tendons, and their initial pretension levels. It is demonstrated that shear span–depth ratio and stirrup ratio are the two main determinants of the failure mode and shear capacity of the concrete beams pre-stressed with carbon fiber reinforced polymer tendons. However, the bonding conditions of the pre-stressing carbon fiber reinforced polymer tendons have no significant effect on the shear capacity of the pre-stressed concrete beam.

Nonlinear deformation analysis for precast pre-stressed concrete beam systems

The structural systems such as road bridge beam systems (span superstructure) or beam systems used in high-rise buildings with precast pre-stressed reinforced concrete might be subjected to the load higher than the calculated load of the design process. In the process of operation the internal forces of the beams reach to a certain value, the section stiffness in elements will be changed. The change in section stiffness will lead to redistribution of internal forces in the whole system. However, that has not been included in the design process. The paper presents nonlinear deformation analysis of precast pre-stressed beam system used in road bridge span superstructure or high-rise buildings using nonlinear model of materials according to Russian construction codes to build the relationship between internal forces and section stiffness. From the calculation results, some comments will be recommended about increased load capacity in comparison with the results obtained from analysis using linear model of material.

Experimental Study on Damaged Prestressed Concrete Beams Using External Post-Tensioned Tendons

Experimental Study on Damaged Prestressed Concrete Beams Using External Post-Tensioned Tendons

Nonlinear Finite Element Analysis of Corrugated Steel Web Composite Beam Based on ABAQUS

Considering the nonlinearity of the material, this paper uses the finite element analysis software Abaqus to model and analyse the external prestressed concrete composite beam of corrugated steel web. In this paper, the key processing methods in the modeling process are described in detail. The whole process of loading and destroying the prestressed concrete composite beams of corrugated steel webs is simulated. The calculated load-deflection curve and load-stress increment curve are in good agreement with the author’s early test results, which verifies the accuracy and reliability of the calculation analysis of external prestressed concrete composite beams of corrugated steel webs. Further analysis shows that in the calculation analysis, the secondary effect of the external prestressing tendon cannot be ignored. In addition, under the limit state, the calculated stress increment of the external prestressed tendons is smaller than the actual measurement, and the preliminary analysis may be related to the calculation of the tensile constitutive model of the concrete material. The in-depth study of the external reinforced stress increment and the transmission mechanism between the concrete and the corrugated steel web will be carried out in the following state.

Bond Behavior of Corroded Strand in Pretensioned Prestressed Concrete Beams

Bond Behavior of Corroded Strand in Pretensioned Prestressed Concrete Beams

Experimental Study of a New Precast Prestressed Concrete Joint

Precast monolithic structures are increasingly applied in construction. Such a structure has a performance somewhere between that of a pure precast structure and that of a cast-in-place structure. A precast concrete frame structure is one of the most common prefabricated structural systems. The post-pouring joint is important for controlling the seismic performance of the entire precast monolithic frame structure. This paper investigated the joints of a precast prestressed concrete frame structure. A reversed cyclic loading test was carried out on two precast prestressed concrete beam–column joints that were fabricated with two different concrete strengths in the keyway area. This testing was also performed on a cast-in-place reinforced concrete joint for comparison. The phenomena such as joint crack development, yielding, and ultimate damage were observed, and the seismic performance of the proposed precast prestressed concrete joint was determined. The results showed that the precast prestressed concrete joint and the cast-in-place joint had a similar failure mode. The stiffness, bearing capacity, ductility, and energy dissipation were comparable. The hysteresis curves were full and showed that the joints had good energy dissipation. The presence of prestressing tendons limited the development of cracks in the precast beams. The concrete strength of the keyway area had little effect on the seismic performance of the precast prestressed concrete joints. The precast prestressed concrete joints had a seismic performance that was comparable to the equivalent monolithic system.

Performance of precast segmental concrete beams posttensioned with carbon fiber-reinforced polymer (CFRP) tendons

Precast segmental prestressed concrete beams (PSBs) have been widely used in many elevated highway bridge projects around the world. Steel tendons at joint locations, however, are vulnerable to corrosion damages, which cause deteriorations and in extreme cases lead to the collapse of the whole structures. This study experimentally investigates the use of carbon fibre-reinforced polymer (CFRP) tendons as an alternative solution for the PSBs to tackle the corrosion issue. Four large-scale segmental T-shaped concrete beams with internal bonded or unbonded tendons and dry or epoxied joints were built and tested under four-point loading. The test results indicated that CFRP tendons showed satisfactory performances therefore could replace steel tendons for the use in PSBs. All the tested beams exhibited excellent load-carrying capacity and ductility. Tendon bonding condition greatly affected the flexural performance of the segmental beams. Joint type had only a slight effect on the load-carrying capacity and ductility of the beams, but significantly affected the beams’ initial stiffness. Unbonded tendons experienced an evident reduction in the tendon strength at the ultimate stage as a consequence of the loading type, harping effect and joint opening. Both AASTHO-1999 and ACI 440.4R-04 predicted well the tendon stress, thus the load-carrying capacity of the beams with bonded tendons, however, the accuracy significantly reduced for the cases with unbonded tendons. Similarly, the codes did not well estimate the deformation capacity of the prestressed beams with unbonded tendons. An empirical formula is proposed to predict the deflections of beams with unbonded tendons, which yields very close predictions to the experimental results.

Generalized Softened Variable Angle Truss Model for PC Beams under Torsion

In a previous study, a new model (Generalized Softened Variable Angle Truss Model—GSVATM) was proposed to compute the global behavior of reinforced concrete beams under torsion, including for low loading stages. In this article, the GSVATM is extended to cover prestressed concrete (PC) beams under torsion, with longitudinal and uniform prestress. The changes in the GSVATM, in order to include the influence of the initial stress state due to prestress, the contribution of the prestress reinforcement after the decompression of concrete and the constitutive laws for prestress reinforcement, are presented, as well as the solution procedure. The theoretical predictions of the extended GSVATM are compared with experimental results of PC beams under torsion, where good agreement is observed in terms of stiffness, transition from the non-cracked stage to the cracked stage and also in terms of the maximum torque. It is also shown that when compared with the predictions of some codes of practice, namely for the cracking and ultimate torque, the estimates from the GSVATM are in general more accurate.

Evaluation of the Increased Dynamic Effects on the Highway Bridge Superstructure

Dynamic properties of the bridge superstructure vary depending on many characteristics of the bridge and the loading conditions. In this paper, maximum Dynamic Amplification Factor was calculated for six different types of typical pre-stressed concrete beam bridges. It showed that each type of bridge with similar loading has a different range of Dynamic Amplification Factor. At the same time, every recently built bridge has different geometry and design load. Hence, it is difficult to determine a characteristic value of Dynamic Amplification Factor for the similar type of structures. By using fullscale dynamic and static bridge tests, it is possible to determine the necessary characteristics which show possibly high Dynamic Amplification Factor. This factor indicates if it is necessary to make a full-scale bridge dynamic analysis. It was found that those characteristics are natural frequency (first mode), damping ratio, relative deflection, and span and depth ratio. Obtained results from tests show a range of values for each of the characteristic. These ranges were analysed for reinforced concrete slab and pre-stressed concrete slab, and girder bridges.

Experimental and numerical studies on bonded prestressed concrete beams at low temperatures

This manuscript studied the structural performances of bonded prestressed concrete (PC) beams at different low temperatures (+20 °C to −100 °C). The main parameters of analysis and discussion were temperature and prestress levels. Theoretical models were proposed to predict the cracking and ultimate resistances of the bonded PC beams at low temperatures. Numerical model was also proposed to simulate behaviours of PC beams at low temperatures. The accuracies of these theoretical and numerical models were validated against the test results. Compressive tests on concrete after freeze-thaw cycles were also carried out to obtain the corresponding mechanical properties. With these test results as input information, numerical parametric studies were performed to study the behaviours of bonded PC beams at low temperatures or after freeze-thaw cycles.

Challenge in Structural Behaviours of Corroded Pre-stressed Concrete Beams

Challenge in Structural Behaviours of Corroded Pre-stressed Concrete Beams

Effect of diagonal cracks on shear stiffness of pre-stressed concrete beam

PurposeDuring service period, due to the overload or other non-load factors, diagonal cracks of the pre-stressed concrete beam are seriously affecting the safety of the bridge structure. The purpose of this paper is to quickly realize the shear bearing capacity and shear stiffness through maximum width of the diagonal cracks and make correct judgments.Design/methodology/approachThrough the shear failure test of four test beams, collecting data of diagonal cracks and shear stiffness loss value. According to the deformation curve of the shear stiffness, and combined with the calculation formula of the maximum width of diagonal cracks, the formula for calculating the effective shear stiffness based on the maximum width of diagonal cracks is deduced, then the results are verified by test data. Data regression method is used to establish the effective shear stiffness loss ratio calculation formula, the maximum width of diagonal cracks used as a variable factor, and the accuracy of this formula is verified by comparing the shear failure test results of pre-stressed hollow plates.FindingsWith the increase in width of the diagonal crack, the loss rate of shear stiffness of the concrete beams is initially fast and then becomes slow. The calculation formulae for shear stiffness based on the maximum width of the diagonal cracks were deduced, and the feasibility and accuracy of the formulae were verified by analysis and calculation of shear test data.Originality/valueA method for quickly determine the shear stiffness loss of structures by using maximum width of the diagonal cracks is established, and using this method, engineers can quickly determine effective shear stiffness loss ratio, without complex calculations. So this method not only ensures the safety of human life, but also saves money.

Probabilistic Safety Analysis of Prestressed Concrete Beams Failing Due to Web-crushing

Web-crushing failure in beams is a brittle failure mode as it typically occurs suddenly without warning. In order to ensure ductile shear behaviour, shear strength is limited by the maximum strut capacity equation (web-crushing equation) to prevent the crushing of concrete before the yielding of shear reinforcement. The accurate prediction of the web-crushing strength of beams is an involved process. Consequently, many codes of practices have resorted to implementing simplified methods for predicting web-crushing failure in beams. Eurocode 2 uses the Variable Strut Inclination Method. This paper aims to assess the model uncertainty and bias (model error) related to the web-crushing strength of prestressed concrete beams. The characteristics of the model error were obtained by comparing experimental web-crushing strengths to predicted web-crushing strengths. Effects of shear parameters on the model error realisations were analysed. The model error was treated as a random variable and used as input in the reliability and safety performance assessment of prestressed concrete beams designed according to Eurocode (EC2) design provisions and failing due to web-crushing. The reliability analysis was conducted using the First Order Reliability Method (FORM). The assessment revealed that the reliability levels implied by the operational EC2 code for web-crushing failure in beams are not consistent over the parametric variation of shear reinforcement (ρwfywm) investigated. The results indicated an increase in estimated reliability index (β) values as ρwfywm increases and a decrease in reliability as concrete strength fcm increases. Low strength beams with ρwfywm ≤ 12.5 MPa and medium strength beams with ρwfywm ≤ 17 MPa generally failed to meet the resistance safety requirement as recommended by EN 1990. The research has contributed to existing studies on the effective application of reliability methods in deriving structural design guidelines.

Performance of Post-Fire Composite Prestressed Concrete Beam Topped with Reinforced Concrete Flange

The performance of composite prestressed concrete beam topped with reinforced concrete flange structures in fire depends upon several factors, including the change in properties of the two different materials due to fire exposure and temperature distribution within the composition of the composite members of the structure. The present experimental work included casting of 12 identical simply supported prestressed concrete beams grouped into 3 categories, depending on the strength of the top reinforced concrete deck slab (20, 30, and 40 MPa). They were connected together by using shear connector reinforcements. To simulate the real practical fire disasters, 3 composite prestressed concrete beams from each group were exposed to high temperature flame of 300, 500, and 700°C, and the remaining beams were left without burning as reference specimens. Then, the burned beams were cooled gradually by leaving them at an ambient lab condition, after which the specimens were loaded until failure to study the effect of temperature on the residual beams serviceability, to determine the ultimate load-carrying capacity of each specimen in comparison with unburned reference beam, and to find the limit of the temperature for a full composite section to remain composite. It was found that the exposure to fire temperature increased the camber of composite beam at all periods of the burning and cooling cycle as well as the residual camber, along with reduction in beam stiffness and the modulus of elasticity of concrete in addition to decrease in the load-carrying capacity.

THE EFFECT OF SHEAR REINFORCEMENT RATIO ON PRESTRESSED CONCRETE BEAMS SUBJECTED TO IMPACT LOAD

Structural elements subjected to impact loads have a different response than those subjected to static loads. This research studied the effect of using shear reinforcement to reduce the local damage occurred when an impact load applied on a prestressed concrete beam. An accurate finite element model was provided for the analysis using the advanced volumetric finite element modeling program (ABAQUS). The concrete material was defined using the built in concrete damage plasticity model (CDP), that considers the nonlinear behavior of concrete when subjected to dynamic loading. All material properties were modified using the dynamic increase factor (DIF) to consider the effect of impact loading. It was realized that the failure was concentrated in the impact zone. However, using shear reinforcement reduced the permanent damage occurred due to impact.

Intelligent tensioning control and management integrated system for high-speed railway pre-stressed concrete beam

The tension force pre-stressing of most pre-stressed concrete beams (BPS) for high-speed railways in China is currently performed using a traditional manual operation method, leading to low efficiency, poor precision, a complicated operation, and uncontrollable calibration authenticity, among other factors. This paper presents an intelligent tension control and management system for a BPS, including the hardware equipment and corresponding matching software system. In accordance with the current scenario in pre-stressed tension construction, intelligent tensioning control station, tensioning jacks, and other hardware equipment, matching BPS software has been developed. This system is based on radio frequency identification technology, cloud technology, big data technology, the building of a set platform regarding the pre-stressed tension construction control, process management, supervision, and implementation of a railway precast beam. The system achieves automation, information, visualization and remote of the entire process of pre-stressed tension construction, and lays the foundation for the popularization of the Internet of Things technology within railways in China.

Transfer length in full-scale pretensioned concrete beams with 1.4 m and 2.4 m section depths

This study aims to investigate the transfer length of full-scale prestressed concrete (PSC) beams with lengths of 30 m and 35 m and section depths of 1.4 m and 2.4 m for highway and railway bridge girders, respectively. To do this, newly developed high-strength (fpu of 2400 MPa) prestressing (PS) strands were used. The initial and effective prestressing forces applied were 94% of the yield strength and 70% of the ultimate tensile strength of the strands. The difference between the transfer lengths at the cut end and dead end was reduced by increasing the section depth. Greater strains were found at the cut end due to a lateral expansion of the strands by the Hoyer effect compared with those at the dead end, causing a greater stress concentration. The eight most widely used prediction models were adopted to predict the transfer lengths of high-strength PS strands in full-scale PSC beams, and it was found that all models significantly overestimated the transfer lengths. Accordingly, the conservative use of the ACI recommendation of 50db is suggested based on this study.

Efficiency of steel and macro-synthetic structural fibers on the flexure-shear behaviour of prestressed concrete beams

The efficiency of steel and structural synthetic fibers on the performance improvement of prestressed concrete (PSC) beams under combined flexure-shear is studied. Results of eleven PSC beams tested at a shear span (a) to depth (d) ratio of five are presented. Discrete steel and macro synthetic structural polyolefin fibers of varying dosages of 0.35%, 0.7% and 1.0% by volume of concrete were used. The effect of fiber addition on overall load – displacement, load- strain, and strain energy absorption capacity of PSC beams is analysed. Other parameters such as shear span to depth ratio (a/d), compressive strength of concrete, prestressing reinforcement ratio were kept constant. The test results portray that the addition of steel fibers stiffens the post cracking response, increases the strain energy absorption capacity more efficiently when compared to macro synthetic fibers (Polyolefin). The failure mode changed from less ductile flexure-shear to more ductile flexure dominant mode at 0.35% and 0.70% volumetric dosage of steel and synthetic fibers, respectively. The strain energy absorption capacity increased by more than 100% at 1.0% fiber addition for both steel and macro-synthetic fibers.