Steel Composite Bridges Research Articles

Detection and localization of small damages in a real bridge by local excitation using piezoelectric actuators

Detection, localization and estimation of small damage using piezoelectric actuators for local excitation is the main idea of this study. The theoretical background of an algorithm based on power spectral density (PSD) method suiting multiple damage detection is developed and verified experimentally with the field data obtained from a composite steel bridge. The method is based on only the output data from the accelerometers without the need for measuring the excitation force. Some damage scenarios were introduced to the test structure by releasing bolts from the members connecting the lower lateral members and the main longitudinal girder. The results indicate that the PSD method could identify the location and monitor small damage growth in structural members.

철도교량 구조형식별 감쇠비 하한값 산정을 위한 시험적 연구

철도교량 동적 설계 및 동적 안전성을 해석적으로 평가하기 위해서는 교량의 감쇠비를 산정하는 것이 매우 중요하다. 본 연구에서는 국내 고속 및 일반철도에서 일반적으로 사용되고 있는 소수주형강합성교, PSC Box, Steel Box, PSC, IPC, Precom, Preflex에 대하여 실내 모형실험 및 운행 중 현장계측을 하였다. 이러한 고속 및 일반철도의 대표적 교량형식에 대한 실내외 시험을 통해 대수감소율을 적용하여 감쇠비를 분석하였다. 따라서 철도교량의 감쇠비는 하중크기, 가진주파수, 진폭에 영향을 받지 않는 것으로 분석되었다. 또한, 기존 철도설계기준에 제시된 감쇠비 하한치와 비교하여 PSC구조 및 강합성구조 철도교량의 경우 감쇠비 하한값을 1.0%로 적용하는 것이 합리적이라 판단되었다. The damping ratio of railway bridge has become one of the most important issues in dynamic design and dynamic stability of railway bridge. In the present study, laboratory and field test were performed for railway bridges such as a twin I-shaped steel composite girder, PSC box, steel box, PSC, IPC, PRECOM, preflex. The damping ratio of railway bridge according to structure types was estimated by logarithmic decrement method. Therefore, magnitude, frequency and amplitude of load did not affect damping ratio of railway bridge. Also, damping ratio limit of steel composite and PSC bridges was evaluated in 1.0%.

EFFECTS OF CLAMPS IN COMPOSITE I-BEAMS STRENGTHENED WITH HM-CFRP

Corrosion of steel members and an increase in the traffic loads make the retrofit necessary for steel bridge beams. To strengthen composite steel bridge beams, either the existing damaged members are reinforced or they are replaced with the new ones. Both process demand a bridge to be closed to traffic for a long time. In emergency cases such as earthquakes, it is crucial to maintain traffic flow for delivering the urgent needs. The bridge can shortly be opened to traffic after the damaged beams are rapidly strengthened by means of composite member reinforcements. In addition, it is possible to quickly strengthen a steel member, which underwent a reduction in cross-sectional area due to corrosion resulting from ambient conditions by applying composite material to its tension flange. In this study, steel beams with I-cross section are reinforced using High Modulus Carbon Reinforced Polymer shortly named HM-CFRP. Also in this study, the effect of using steel clamps on the strengthening method is investigated. The clamps are used to avoid the slip of HM-CFRP material from epoxy. Different brands of epoxy are tested in order to determine which type of epoxy is to be used. Made up I-cross section beam having a similar bending behavior were tested in place of reinforced concrete composite steel beams and the reinforcement methods are subsequently applied on the made up I-cross section steel beams.

Optimisation of Transversal Disposition of Steel and Concrete Composite Road Bridges

The paper deals with optimisation of transversal disposition of steel and concrete composite road bridges in terms of the number of steel beams. For this purpose, a parametric study was performed, in which a total of 32 superstructures of steel and concrete composite road bridges, with different number of steel beams, different road widths and theoretical spans, were modelled and assessed. The reliability verification of the superstructure has been done according to Eurocodes. A result of parametric study is a comparison of advantages of the double-beam and the four-beam variants in terms of material consumption when considering different transverse dimensions and spans of the bridge. The individual variants are compared on the basis of the consumption of structural steel, concrete and reinforcing steel bars.

Dynamic behavior comparison of steel-composite and concrete high speed railway bridges

The dynamic behavior of two steel bridges crossed by the Korean High Speed Train (KTX) has been investigated experimentally and the results are compared with the specification requirement and other typical prestressed concrete box girder bridge’s responses. The investigated bridges are two 2-girder steel bridges, one of 1@40 m span length, and the other of 2@50 m span length, and a PSC Box girder bridge of 2@40 m span length. A set of experimental tests were performed during the operation of KTX, and a number of accelerometers, LVDTs and ring-type displacement transducers were utilized for measurement of three kinds of dynamic responses (acceleration, deflection, and end-rotation angle). Measured responses show that the vertical deflections and end-rotation angles of the three bridges all satisfy the spec. requirement with a large margin, but acceleration responses were also found to be very close to, or exceeded, the limit value. It was found that most of the excessive acceleration responses occurred when the passing speed of the train is close to the critical velocity which causes resonance. No noticeable differences of dynamic responses due to the different materials (steel or concrete) could be found within these experimental results.

Composite steel and concrete bridge trusses

Distribution of longitudinal shear along an interface between steel and concrete parts of various composite truss bridges from elastic phase up to plastic collapse is presented. With respect to the authors’ previous experimental research reported in references, the numerical analysis and the Eurocode approach concerning distribution of the longitudinal shear flow is studied in detail. The main interest is devoted to elastic and elastic–plastic distribution of the flow corresponding to the design level of bridge loading and plastic collapse. The analysis covers both the common elastic frame 2D modelling of the shear connection used by designers and the 3D GMNA (geometrically and materially non-linear analysis) using ANSYS software package. Results of the various models are mutually compared and confronted with provisions of Eurocode 4 for composite bridges. The non-linear distribution of the longitudinal shear, required for correct design of shear connection of composite steel and concrete bridges (in both ultimate limit state including fatigue and serviceability limit state) significantly depends on rigidity of the shear connection and densification of the shear connectors above truss nodes. These issues are analysed in parametrical studies, commented and finally some recommendations for practical design are suggested.

Three dimensional modeling for steel-concrete composite bridges using systems of bar elements — Modeling of skewed bridges

A new improved way for modeling steel composite straight bridges has been presented (Vayas, 2009; Vayas, 2010). The proposed model is based on the representation of steel I-girders through the use of equivalent trusses. The concrete slab is suitably represented by a set of bar elements. Diaphragms and stiffeners may also be taken into account. In contrast to the grillage model, which is usually used for the analysis of bridges, the recommended three dimensional model allows for a more reliable prediction of deformations and internal forces. This paper discusses the extension of the model to skewed composite bridges. The presence of skew makes the analysis complicated and for this reason the grillage analysis is not always recommended. Phenomena like differential deflections of the main girders during concreting and lateral displacements of the flanges can be adequately predicted using the proposed model. The new way for modeling composite bridges, using a spatial system of beam-like structural elements, can also be used for stability analysis of skewed bridges. Worked examples are provided to illustrate the set up procedure of the proposed modeling and to compare the different ways of analysis.

Application of the continuous wavelet transform on the free vibrations of a steel–concrete composite railway bridge

In this article, the Continuous Wavelet Transform (CWT) is used to study the amplitude dependency of the natural frequency and the equivalent viscous modal damping ratio of the first vertical bending mode of a ballasted, single span, concrete–steel composite railway bridge. It is shown that for the observed range of acceleration amplitudes, a linear relation exists between both the natural frequency and the equivalent viscous modal damping ratio and the amplitude of vibration. This result was obtained by an analysis based on the CWT of the free vibrations after the passage of a number of freight trains. The natural frequency was found to decrease with increasing amplitude of vibration and the corresponding damping ratio increased with increasing amplitude of vibration. This may, given that further research efforts have been made, have implications on the choice of damping ratios for theoretical studies aiming at upgrading existing bridges and in the design of new bridges for high speed trains. The analysis procedure is validated by means of an alternative analysis technique using the least squares method to fit a linear oscillator to consecutive, windowed parts of the studied signals. In this particular case, the two analysis procedures produce essentially the same result.

Modeling of curved composite I-girder bridges using spatial systems of beam elements

A new way of modeling steel composite bridges has been presented by Vayas et al. (in press, 2010) [3,4]. The proposed model is based on the representation of steel I-girders by equivalent trusses. The concrete slab is suitably represented by a set of bar elements, and the bearings by appropriate springs. Diaphragms and stiffeners may also be taken into account. In comparison to the grillage model, which is usually used for the analysis of bridges, the proposed three-dimensional model allows a more reliable prediction of deformations, internal forces, and stresses. Curved bridges display unique behavior characteristics, and for this reason a grillage analysis is not always suitable. The new way of modeling composite bridges, using a spatial system of beam-like structural elements, is applied in this paper for the modeling of curved composite bridges. Worked examples are provided to illustrate the set-up procedure of the proposed modeling and to compare its results with those of corresponding finite element models.

Spatial systems for modelling steel‐concrete composite bridges — comparison of grillage systems and FE models

AbstractPlane grillages and finite element models are widely used for the design of bridges. In a grillage idealization the entire superstructure of the bridge is suitably represented by different sets of bar elements. On the other hand, the finite element method makes use of plane and solid elements for the three‐dimensional representation of the structure. Although these models are generally accepted as sufficiently accurate, they are associated with some drawbacks. To overcome the difficulties of plane grillage and finite element analyses, a new way of modelling steel composite bridges is presented in this paper. The proposed model is based on the simulation of steel I‐girders through the use of equivalent trusses. The concrete slab is represented by a set of bar elements and the bearings by the use of appropriate springs. Diaphragms and stiffeners may also be taken into account.This new way of modelling composite bridges using a spatial system of beam‐like structural elements allows deformations and internal forces to be predicted reliably, and can be used for dynamic and stability analysis. Worked examples are also provided to illus trate the setup procedure for 3D modelling and to compare the different analysis methods. The work presented in this paper is part of a research project investigating the modelling of steel and composite bridges which is being carried out at the National Technical University of Athens.

Testing a soil–steel bridge under static and dynamic loads

The static and dynamic response of a long-span arch soil–steel composite railway bridge is studied. The bridge has a span of 11 m and a rise of 4·3 m. Two field tests were carried out before and after the first winter. Strains and displacements were measured during passages of a locomotive at different speeds. Vertical ballast accelerations and the effects of braking forces were also measured. The measurements indicated that the speed of the vehicle had a large influence on the displacements, thrusts and moments. The structure was found to be safe when measured values of moments and thrusts were compared with live load calculations according to design codes. It is concluded that the dynamic amplification factors calculated from the tests were larger than the theoretical values according to bridge design codes. However, there are indicators of post-winter effects in the form of reduced dynamic amplification factors.

중간지점부의 캠버 조정에 따른 강합성교의 모멘트저감 효과

본 연구에서는 구조해석 모델링의 적합성을 평가하기 위하여, 고속철도상의 2주형 거더교에서 KTX 시험 활 하중에 의한 동적 거동에 대한 계측과 3D 모델링을 통한 시간이력해석이 수행된다. 이를 바탕으로 중앙지점부 캠버 조정을 통한 프리스트레스가 도입된 대상 교량에서 지점부의 모멘트저감 효과의 검토를 위하여, 시공단계 해석이 수 행되며, 장기거동에 대한 응력손실까지 고려된다. 적정수준의 초기 도입력을 산정하여 경제적인 교량단면을 위한 모 멘트 저감 방법이 연구된다. 최종적으로 교량 단면을 보다 효율적으로 사용할 수 있는 경제적인 교량 설계방법을 제 시한다.

Review and Assessment of Fire Hazard in Bridges

Bridge fires are low-probability but high-consequence incidents. Generally, bridge design codes and standards, in contrast to building codes, do not take into account the concept of fire safety. However, recent high-profile fire incidents on bridges and in other infrastructure have opened a debate on the need for fire resistance requirements on bridges. An overview of fire hazard in bridges is presented. A state-of-the-art review related to the bridge fire hazard was carried out. Different conditions and complexities associated with characterizing fire hazards in bridges are discussed, and a design strategy to integrate performance-based fire safety into bridge design is suggested. Further, a strategy to assess and repair fire-damaged bridges is proposed. A case study is presented to evaluate the fire performance of a composite steel bridge girder. Finally, needed research that can lead to improved performance of bridges during fire incidents is highlighted.

Extracting modal parameters of high-speed railway bridge using the TDD technique

In case the excitation frequency induced by a high-speed train passage coincides with the natural frequency of a railway bridge, a resonance of the bridge occurs. In addition, if the train is passing through the bridge very quickly, measurable time samples can be of limited numbers and thus modal parameters of the bridge can hardly be obtained. To get over this, effective technique for the extraction of modal parameters is proposed in the present study. With the cross correlations among free vibration responses immediately after the train passes, mode shapes are obtained by TDD (time domain decomposition) technique while temporal modal parameters are extracted by the proposed sensitivity-updating system identification technique. A two-span steel composite girder bridge, which is of typical Korean high-speed railway bridge system, is employed to verify the proposed approach. Comparative studies reveal that the predictions of the proposed approach agree well with those by the well-known existing methods. It is thus postulated that the present approach is promising in terms of both accuracy and applicability.

Dynamic testing of a soil–steel composite railway bridge

Actual dynamic response of a long-span corrugated steel culvert railway bridge is studied. The bridge, which is a type of soil–steel composite structures, has a span of 11 m. Tests were carried out by measuring strains and displacements during passages of a locomotive at different speeds. Vertical ballast accelerations as well as the effects of braking forces were also measured. The tests showed that the speed has a large influence on the displacements, thrusts and moments. The measured dynamic displacements and thrusts are as much as 20% larger than the corresponding static response. This is greater than the values specified in bridge design codes. Dynamic amplification factors as high as 1.45 were obtained for the moments at the quarter point which is found to be much larger than the values for the crown point. This type of bridge structure is believed to be less sensitive to resonance from passing trains than other common bridge types, due to the high damping values obtained from the forced vibration tests.

An actual test and FE analysis of a steel and concrete composite girder bridge exposed to fire

AbstractIt has been reported that there are many examples of bridges damaged by fire due to traffic accidents, doubt fires and incendiary fires. When steel and concrete composite girder bridges are exposed to fire, it is necessary to verify the decrease in strength of the structural steel and the concrete. This paper describes the fire test setup for a steel and concrete composite girder bridge. The experimental results are discussed. Furthermore, a finite element analysis is carried out for the steel and concrete composite girder. Finally, the experimental and analytical results are compared.

The Munkedal Bridge across the – River Örekil

AbstractThis 477 m long steel composite bridge is situated approximately 90 km north of Gothenburg and forms part of the 3000 km long European route E6, which connects Southern Sweden with Northern Norway. The 24.2 m wide steel composite deck is carried by a concrete arch spanning 225 m.

Long-term Structural Health Monitoring of a Multi-girder Steel Composite Bridge Using Strain Data

This paper presents an approach to use strain data from a multi-girder, composite steel bridge for long-term Structural Health Monitoring (SHM). The bridge being studied is part of a research project at the University of Connecticut in which long-term SHM systems are being installed on a series of bridges throughout the State of Connecticut. Strain data is collected from normal truck traffic to determine live load stresses, load distribution factors, and the location of the neutral axis in each girder. Known weight trucks were used along with a finite element analysis for verification of the behavior. The long-term monitoring approach is based on determining the live load distribution factors, peak strains, and the neutral axis locations. The goal is to use existing, readily applied technology for SHM for long-term use on bridges that have raised concerns, due to corrosion noted in routine visual inspections, overloading, or fatigue sensitive details. The SHM system proposed can be used on a continuous basis to determine if there are significant changes in the structural behavior that would be indicative of major damage to either the girders or the concrete deck.

Static and dynamic characteristic of the existing two span steel composite girder bridge considering influence of substructure

Static and dynamic characteristic of the existing two span steel composite girder bridge considering influence of substructure

Development of improved natural frequency equations for continuous span steel I-girder bridges

Field testing and analytical studies to predict natural frequencies of steel stringer bridges are reviewed in this paper. A three-dimensional (3D) finite element analysis (FEA) procedure using the commercial software ABAQUS, which efficiently captures the vibration characteristics of such bridges, is proposed. Two continuous-span composite steel bridges dynamically (field) tested by others were used to validate the proposed FEA model, which indicates excellent agreement between the analytical and field data. A natural frequency parametric study has been conducted by utilizing the FEA procedure. Based on the regression analysis of the parametric study results, practical equations are proposed to predict the natural frequencies of continuous-span composite steel bridges. The parametric study results are also compared with existing prediction methods, showing that the proposed equations represent a significant improvement over the existing prediction methods.