Reinforced Concrete Girders Research Articles

Comparative Study on the Seismic Vulnerability of Continuous Bridges with Steel–Concrete Composite Girder and Reinforced Concrete Girder

For medium- and small-span bridges, the weight of the superstructure in steel–concrete composite girder bridges is lighter than that of a reinforced concrete girder bridge. However, it is still uncertain whether steel–concrete composite girder bridges exhibit superior seismic performance compared to reinforced concrete girder bridges. This study quantitatively compared the seismic performance of the two types of bridges. Using the theory of probabilistic seismic demand analysis, the seismic vulnerability curves of bridges were derived. To conduct seismic demand analysis for probabilistic analysis on the OpenSEES platform, bridge samples were generated using the Latin hypercube stratified sampling method, which considers the uncertainties associated with the two types of bridges. The vulnerability curves of the piers, bearings, abutments, and the system of the two bridges were established using probabilistic analysis of the time history analyses. The results showed that the seismic vulnerabilities of components and the overall system of the steel–concrete composite girder bridge were both lower than those of the reinforced concrete girder bridge. When the peak ground acceleration (PGA) of the ground motion was 0.3 g, the moderate and serious damage probabilities of the piers in the steel–concrete composite bridge were only 54.61% and 60.89%, respectively, of those of the reinforced concrete bridge. Consequently, replacing the upper reinforced concrete girders with steel–concrete composite girders can significantly improve the seismic performance of a large number of existing bridges.

Numerical Simulations on the Flexural Behaviours of Reinforced Concrete Girders Strengthened with Bolts

Precast reinforced concrete (RC) girders with dapped ends are used in order to reduce the overall depths of concrete floors and bridge decking and meet architectural requirements. The structural requirements by reducing the depths of these girders result in stress concentrations within the recessed zones. Thus, girders with dapped ends require special details for the strengthening systems. The use of open transverse holes in RC sections is for the passage of various service lines such as telecommunication cables, gas lines, water pipes, electricity cables, etc. The behaviours of RC girders with dapped ends and openings strengthened by bolts subjected to two vertical concentrated loads were numerically simulated by utilising commercial finite element software ANSYS. The numerical results from the simulated models were identical and compatible with those experimental results stated in literature. The validation of the numerical results with those experimental ones was based on the statistical analysis by including the calculations of the correlation coefficients, arithmetic means, and standard deviations for all the simulated girder models in terms of loads and deflections. The obtained numerical results showed that an increase in the compressive strength of concrete by 20% would cause an increase in the loading resistance of the models by 13% and a decrease in the deflection by 21%, respectively. Also, it was indicated that the type of section, i.e., the change of the section from solid to open (with transverse openings), would decrease the resistance of the section by 8–16% and increase the deflections by 15–20%. Similarly, an increase in the number of holes would result in the decreases in the load resistance by up to 6% and the increases in the deflections by up to 24% under the same applied loads. Strengthening openings using vertical bolts has an important role in enhancing the resistance of the models by 8–20% and decreasing the deflections by 20–30%. The failure patterns were hybrid, e.g., flexure and shear, and identical with the experimental ones. Finally, the effect of using the cylindrical compressive strength of concrete as a mechanical parameter on the structural behaviours of the simulated models was investigated, which could improve the resistance loading and decrease the deflections of the models.

Effect of Skew Angle on the Dynamic Response of a Reinforced Concrete Bridge under Blast Loading

Accidental explosions and subversive blasts are on rise. The recent devastating Beirut explosion witnesses this fact. Performance of the structures such as bridges in cities and strategic boarder areas is of paramount importance. With this concern the effect of skew angle on the performance of a single span reinforced concrete (RC) bridge deck supported on three symmetrically placed RC girders under blast loading generated by1000kgTNT charge located above and below the mid-section of the central girder at a standoff distance of 0.5 m has been investigated using ABAQUS/CAE. Analyses have been performed at different skew angles i.e. 0º, 10º, 20º, 30º, 40º, and 50º. Several empirical relations from the literature have been used to estimate the blast parameters such as peak overpressure, positive phase duration, the arrival time of blast wave, and decay coefficient. Blast pressure P(t), has been modeled using modified Friedlander’s equation. Distributions of damages have been evaluated with a mesh size of 300 mm using concrete damage plasticity (CDP) model. Maximum displacements have been computed and are compared with those obtained from the provisions of AASHTO: Load Resistance and Factor Design (LRFD) - Bridge Design Specifications (2014). It has been found that the midspan displacement and the stresses of the deck increase for 10º skew angle but decrease for subsequent increase in skew angle for the explosive charge loaded above the mid-section of the central girder. However, tensile as well as compressive damages in girders increase with increase of skew angle irrespective of the location of the blast. Side girders suffer more damage with increase in skew angle than uniform damage for ‘under the deck’ location of explosive charge.

Finite Element Model Updating of RC Bridge Structure with Static Load Testing: A Case Study of Vietnamese ThiThac Bridge in Coastal and Marine Environment.

Diagnostic load testing refers to the use of the measured historical responses of the structure in the field data to better understand its dynamic and static structural behaviours. It is important and necessary to predict the health state, load capacity, and aging of the structure by updating the finite element (FE) model, which can give useful information to aid the design of retrofits and the maintenance of the existing bridge in the future. The paper presents an update of the full-scale FE model for the reinforced concrete (RC) bridge structure over the seawater river based on the experimental strains under the static load testing in which the representative FE model of the actual structure is determined from the optimisation procedures. The optimisation variables are applied, including the cross-sectional properties and concrete material calibrated through the genetic algorithm (GA) optimisation in the MATLAB software, which interfaces with the FE modelling in the scripting of the SOFISTIK TEDDY software automatically. The bending moments at the mid-span of the RC girders are determined in the FE modelling to compute stresses, which are compared with the measured stresses through optimisation scenarios with a percentage error of the objective function less than 10%. The measured data of concrete strains are recorded from reusable strain transducers installed on the mid-span girders for every bridge span, which are used to calibrate the bridge model in static load testing. The novelty of the solution is to implement innovative techniques using field data as an improved approach for calibrating automatically the analytical FE model parameters of all RC spans of the bridge until its static behaviours are very similar to those of the actual bridge. The final updated FE modelling is used to apply truck load configurations according to bridge design standards such as the AASHTO specifications, which can predict the load limits of the existing bridge structure more accurately and reliably. These proposed approaches can be applied to large bridges as well as complex structures with supporting FE analysis software and data processing software.

Effect of the interaction of corrosion pits among multiple tensile rebars on the reliability of RC structures: Experimental and numerical investigation

The deterioration of reinforced concrete (RC) structures due to chloride-induced corrosion is not spatially uniform because of the spatial variability related to material properties and environmental stressors. This variation has a substantial effect on the reliability of RC structures. However, few experimental studies have focused on the effect of the interaction of corrosion pits among tensile rebars on the reliability of RC structures. Therefore, in this paper, an experimental procedure that incorporates X-ray and digital image processing techniques was conducted on RC slab specimens subjected to accelerated corrosion. Using the experimental results, the parameter of the transverse correlation function of steel weight loss distributions was estimated to investigate how the corrosion pits in corroded rebars are correlated. Based on the experimentally obtained model parameters, the spatial steel weight loss distributions were simulated by spectral representation method. A three-dimensional (3D) nonlinear finite element (FE) analysis of RC structures with simulated steel weight loss distributions was conducted to obtain the ultimate bending capacity of RC structures. In an illustrative example, the effect of the transverse correlation among steel weight loss distributions of multiple tensile rebars on the failure probability of RC girders was quantified.

Multi-channel random decrement smart sensing system for concrete bridge girders damage location identification

Health monitoring of infrastructures is one of the essential modern services for civil engineering structures. A design of a Structural Health Monitoring (SHM) system that allows a continuous assessment of the structure’s integrity is required to increase safety, and to optimize operational and maintenance costs. Nowadays, non-destructive techniques are common to predict the damage as it monitors the structure during its service lifetime. The advances of using Fiber Bragg Grating (FBG) array sensors for continuous monitoring has been proven to be far superior and more accurate than strain gauges and accelerometers due to the great reduction in noise signals. The Random Decrement (RD) technique is one of the output measurement diagnostic techniques used for identifying the dynamic properties of bridge girders. The technique to be applied on multi-channels for enhancing the efficiency of data aggregation and integrity identification using fiber optic multi-channel sensor networks system known as Multi-Channel Random Decrement (MCRD) for concrete bridge monitoring. The significance of RD and MCRD approaches in SHM is that it determines the bridge’s dynamic properties without the prior knowledge of the magnitude of excitation forces; so the identification system of the bridge is based on random bridge actual traffic loading response through the installed FBG sensing system to record the dynamic response due to the applied traffic loading.The concept has been used before for steel and metal structure. However, the concrete material is a nonlinear elasto-plastic damaged material with unique qualities of cracking, tension softening, shear degradation and tension stiffening effects. The emphasis for the steel beam monitoring is focused on the change in the natural frequency; however, the emphasis for the concrete beam monitoring is focused on the change in the Random Decrement Damping (RDD) between the intact and damaged case. The change in RDD is more evident for concrete beams due the rapid change in stiffness due to cracking and the propagation of cracking due to loading. The focus in this work is to assess the applicability of using MCRD with FBG arrays for monitoring reinforced concrete (RC) girders based on experimental testing. For validating the feasibility of the proposed approach, a laboratory investigation has been performed on a main and secondary girder to identify the suitability of using FBG sensors on RC girders to detect the damage and locate it. The results of the investigation showed that MCRD using FBG sensors has the potential to detect the damage location that could be implemented effectively in bridge monitoring strategies.

Behavior of CFRP strengthened RC multicell box girders under torsion

The use of fiber reinforced polymer (FRP) for torsional strengthening of reinforced concrete (RC) single cell box beams has been analyzed considerably by researchers worldwide. However, little attention has been paid to torsional strengthening of multicell box girders in terms of both experimental and numerical research. This paper reports the experimental work in an overall investigation for torsional strengthening of multicell box section RC girders with externally-bonded Carbon Fiber Reinforced Polymer CFRP strips. Numerical work was carried out using non-linear finite element modeling (FEM). Good agreement in terms of torque-twist behavior, steel and CFRP reinforcement responses, and crack patterns was achieved. The unique failure modes of all the specimens were modeled correctly as well.

Torsional Resistance of Reinforced Concrete Girders with Web Openings

In this study, a three dimensional finite element analysis was utilized to study the behavior of reinforced concrete T-
 girders with and without web openings under pure torsion by using
 ANSYS
 APDL
 15.0 program.
 Fourteen
 reinforce concrete T
 -
 girders were ana
 lyzed; one of the
 girders (without web openings)
 was
 modeled as a control girder. The analysis variables
 considered for the other girders are: size, shape, position
 of web openings
 , number of web
 openings and the method
 was
 used to strengthen the member at
 openings, (using internal
 deformed steel bars as in the case where the openings are planned before casting the girders).
 To
 study the general
 behavior of
 finite element models,
 torque
 -
 angle
 of twist plots at the end of the
 span near the loaded arms were r
 epresented.
 From this
 relation
 , it was
 showed a de
 c
 reasing in
 the strength of the T
 -
 girders with web openings under the torsional loads and increasing of the
 angle of twist
 .
 The
 results were analyzed in terms of torque twist characteristics; ultimate torque,
 crack patterns,
 crack width,
 warping
 and
 stresses.
 These terms were presented and a comparison
 between the finite element results was made.
 Keywords
 :

Ecological-Economic and Technical Advantages of Reinforced Concrete Girders with Combined Reinforcement

Changing of usual reinforcement, having, as a rule, welding joints with the pre-stressed joint-free steel has a significant ecological meaning, reducing harmful emissions. Decrease of the concrete consumption is also solving this important ecological issue, since the volume of concrete and concrete dust is reduced. In the compressed elements extreme compressing forces in the reinforcement upon concrete destruction reach 400-500 MPa due to limited concrete compression, which is why use of extra-strong reinforcement in such elements is not reasonable. With the purpose of increase of extreme compressing forces in the reinforcement of compressed elements it is suggested to pre-compress it. Increase of limits of stress in the reinforcement allows to efficiently using extra-strong reinforcement in the compressed zone which will lead to substantial reduction of its consumption. Effect from the pre-compression of the reinforcement is the higher, the bigger is the reinforcement percent. Degree of increase of strength of the elements upon pre-compression of reinforcement with decrease of concrete strength increases.

Are Reinforced Concrete Girder Bridges More Economical Than Structural Steel Girder Bridges ? A South African Perspective

This study investigated the cost-effectiveness of steel girders compared with conventional reinforced concrete girders used in bridge construction in South Africa. The investigation considered an existing bridge which required widening as a result of increased traffic flow. The consulting engineers chose two 10 m reinforced concrete girders for the end spans, while two 22 m post-tensioned reinforced concrete girders were used for the central spans. To determine the cost-effectiveness of the consulting engineer’s choice, steel girders were designed for the 10 m and 22 m beams based on the relevant South African design codes of practice. The analysis was conducted for both non-composite and composite action between the steel girders and the reinforced concrete bridge deck. Based on the design calculations, a cost comparison was performed. The investigation revealed that steel girders are an economically viable option when off-the-shelf steel sections up to 10 m in length are considered. For the 10 m girders, a significant cost saving was achieved for both noncomposite and composite construction compared with reinforced concrete. However, for the 22 m spans, the post-tensioned reinforced concrete girders are significantly more cost-effective compared with steel plate girders. Thus, bridge design engineers should consider steel girders as an option during the conceptual design stage for end spans. A survey was also conducted among senior engineering professionals to determine the reason(s) for the apathy towards using structural steel sections as girders in bridge construction in South Africa.

Effects of Axial Tension on Shear-Moment Capacity of Full-Scale Reinforced Concrete Girders

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Behavior of Epoxy-Injected Diagonally Cracked Full-Scale Reinforced Concrete Girders

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Fatigue Failure Characteristics of Steel Reinforced Concrete Girders

With the rapid development of the express railways in China, a large number of express railway station buildings have been constructed in recent years. Steel reinforced concrete (SRC) girders are used in many buildings for express railway stations. It is a new subject for fatigue behavior of SRC girders under daily train loading. This subject is discussed preliminarily in the current paper. Fatigue tests on three SRC girders were carried out in Tongji University. The test specimens, testing program as well as experimental results are presented. The fatigue failure characteristics of the SRC girders are described in detail and compared with the static failure characteristics. It was found that the fatigue cracking was initiated at the weld toe of shear studs on the tension flange of welded H-section steel inside the SRC girder and then the crack propagated along the flange width and the web height until the girder lost loading capacity due to lack of enough cross section. The fatigue strength of the welded H-section steel played a key role in the fatigue strength of SRC girders. Suggestions for improving the fatigue strength of SRC girders and future research work are proposed finally.

Shear Strength of Reinforced Concrete Girders with Carbon Fiber-Reinforced Polymer: Experimental Results

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Evaluation of debonding failure of reinforced concrete girders strengthened in flexure with FRP laminates using finite element modeling

The use of Fiber-Reinforced Polymer (FRP) materials dates back to the early 1940s when they were used in aerospace and naval applications. During the 1970s and early 1980s, FRP started being used in civil engineering applications for new construction, but more importantly for repair and strengthening of existing structures. However, experimental research showed that the typical failure mode of reinforced concrete (RC) structures strengthened with FRP composite materials is due to the debonding that occurs at the interface between concrete and FRP. The bond between FRP and concrete is therefore the key factor controlling the behavior of these structures since it limits the full use of the FRP strength. The paper evaluates the effect of the debonding failure on the response of FRP-strengthened RC beams. A nonlinear RC beam element with bond-slip between the concrete and the FRP laminates is developed and used to analyze several test specimens and to investigate their corresponding failure mode. The model was also used to study the reduction factor of FRP tensile strength of simply supported strengthened RC girders due to debonding failure. This reduction factor proved to be affected by several parameters: (a) the bond strength between FRP and concrete interface; (b) the concrete strength; (c) the thickness of FRP; (d) the modulus of FRP; (e) the width of FRP laminate; and (f) the development length of the FRP sheet. A large number of beam specimens were analyzed in order to conduct a thorough evaluation of debonding failure of RC beams strengthened with FRP laminates. Based on these studies, new equations that account for the aforementioned parameters were proposed to address the reduction in FRP strength due to debonding failure.

Strengthening multiple span simply-supported girder bridges using post-tensioned negative moment connection technique

A post-tensioned negative moment connection technique is proposed to strengthen old multiple span simply-supported T-section reinforced concrete (RC) girders. In this technique, old concrete is removed from girder ends and flanges, a diaphragm is placed between the two adjacent girder ends over the interior support and negative moment steel strands are installed in new cast-in-place concrete and post-tensioned to make continuity. A total of six two-span simply-supported T-section RC girders were cast and five of them strengthened using the provision of the proposed post-tensioned negative moment connections. Both laboratory tests and nonlinear finite element (FE) analysis were conducted to investigate the structural performance of the strengthened RC girders. The moment redistribution in the strengthened continuous RC girders was also measured and is discussed. It is shown that the proposed post-tensioned moment connection technique can reliably transfer the negative moment over the support and markedly increase member stiffness and the load-carrying capacity of existing multiple span simply-supported RC girders. The validity of the FE analysis was also demonstrated through comparisons with experimental results.

Experimental and Analytical Evaluation of Reinforced Concrete Girders under Low-Cycle Shear Fatigue

Stirrup stresses in lightly reinforced concrete bridge girders may exceed the elastic limit while in service. Increasing load magnitudes and volume over time, multiple permit loads, and modern superloads creates the potential for low-cycle fatigue. In this study, six full-scale reinforced concrete girder specimens representative of those found in 1950s reinforced concrete deck-girder bridges were tested under low-cycle fatigue conditions. The specimens were tested in both T and inverted-T configurations. Other test variables included stirrup spacing, flexural reinforcing details, and spacing of supports. Results showed that low-cycle fatigue produced bond deterioration and cumulative plasticity of stirrups. Progressive fracture of stirrup reinforcement under low-cycle fatigue led to eventual specimen failure. A methodology for the analysis of low-cycle fatigue in girders is proposed using the finite element method to approximate stirrup stress ranges and a linear damage model to estimate the life of a conventionally reinforced concrete girder under repeated overloads. This methodology provided good correlation between the experimental and predicted number of fatigue cycles for lightly web-reinforced specimens.

Experimental and analytical behavior of haunched thin-walled RC girders and box girders

This paper presents an experimental and analytical investigation on the behavior of haunched thin-walled reinforced concrete (RC) girders and box girders subjected to centric and eccentric loads. Five tests were conducted on medium-scale RC girders and box girders to study the effect of load eccentricity and the influence of bottom slabs on their ultimate load-carrying capacities, failure mechanisms and load–deformation relationships. Accordingly, the tested girders were modeled using ADINA, and a non-linear finite element analysis was conducted. The investigation showed that load eccentricities considerably reduced the ultimate loads and the ductility of the girders with open sections. However, when the open section was converted to a full-span box section, the behaviors of the girders were significantly improved.

Fatigue of Diagonally Cracked RC Girders Repaired with CFRP

Fiber-reinforced polymers (FRP) are becoming more widely used for repair and strengthening of conventionally reinforced concrete (RC) bridge members. Once repaired, the member may be exposed to millions of load cycles during its service life. The anticipated life of FRP repairs for shear strengthening of bridge members under repeated service loads is uncertain. Field and laboratory tests of FRP-repaired RC deck girders were performed to evaluate high-cycle fatigue behavior. An in-service 1950s vintage RC deck-girder bridge repaired with externally bonded carbon fiber laminates for shear strengthening was inspected and instrumented, and FRP strain data were collected under ambient traffic conditions. In addition, three full-size girder specimens repaired with bonded carbon fiber laminate for shear strengthening were tested in the laboratory under repeated loads and compared with two unfatigued specimens. Results indicated relatively small in situ FRP strains, laboratory fatigue loading produced localized d...

Crack Condition Evaluation Approach for the Deteriorated Girder of an RC Bridge

A crack condition evaluation method is proposed that identifies the damaged state of deteriorated reinforced concrete (RC) girders on bridges directly on-site. This nondestructive testing approach is based on stress wave propagation theory and can identify the profile of flexural crack tips inside RC girders. A damage index is further determined by comparing the measured crack tip and the theoretical neutral axis of a girder. This index can be utilized to analyze the current loading capacity of deteriorated RC girders according to the AASHTO-LRFR Manual (AASHTO 2003), Manual for Condition Evaluation and Load and Resistance Factor Rating of Highway Bridge, Washington, D.C. Experimental results demonstrate that the position of crack tip can be accurately located.