Concrete-filled Steel Tube Arch Bridge Research Articles

Test of Broken Suspender Specimen and Equivalent Static Calculation Method for Half-Through and Through Concrete-Filled Steel Tubular Arch Bridges

In response to the frequent collapse of main girders caused by the breakage of suspenders on half-through and through arch bridges, a test specimen has been designed and fabricated with a through concrete-filled steel tube (CFST) arch bridge as the engineering background. A new electromagnetic disconnect trigger is employed to realize the rapid suspender breakage in the test specimen. Dynamic response tests of the residual structure of the arch bridge after suspender failures employing the test specimen have been carried out. A finite element model accounting for the suspender breakage dynamic process has been constructed by implementing ANSYS/LS-DYNA, and the results of the test and finite element analysis are compared. In order to simplify the dynamic response calculation process of the residual structure after hanger failures, the dynamic coefficient is introduced, and an equivalent static calculation method (ESCM) considering the dynamic effect of the suspender fracture is presented. Eleven kinds of CFST standard arch bridges with different spans are constructed, the static and dynamic effects of the standard arch bridge with various dynamic coefficients are compared, and then their corresponding dynamic coefficients for various suspender fractures are determined. The obtained results reveal that the proposed electromagnetic suspender breakage trigger can realize the hanger fracturing within 0.1 s, which accurately simulates the fracture process of an actual bridge suspender, and the influence on the value of the dynamic coefficient can be ignored when the duration for suspender fracture is less than or equal to 0.15 s. The influence of suspender fracture on the displacement and stress of the longitudinal beam is more notable than those of the arch rib. In particular, the long suspender breakage has the highest influence on the displacement and stress of the longitudinal beam and arch rib. The fracture of the second short suspender has a remarkable impact on the suspender force of the adjacent hanger. When the ESCM is utilized to assess the mechanical behavior of the half-through and through CFST arch bridge, the dynamic coefficients of the longitudinal beam (suspender) were evaluated to be, conservatively, 1.8 (1.8) and 1.8 (1.7), respectively.

Corrosion Fatigue Test and Performance Evaluation of High-Strength Steel Wires Based on the Suspender of a 11-Year-Old Concrete-Filled Steel Tube Arch Bridge

In this study, based on an actual project, the steel wire in the suspender of a concrete-filled steel tube arch bridge was selected from appropriate samples to perform acetic acid-accelerated salt spray tests, and steel wire samples with different corrosion degrees were obtained. A laser microscope was used to measure the roughness of the samples, and three corrosion samples were randomly selected from each group for grinding. Fatigue tests were performed on steel wire samples with different degrees of corrosion and polished steel wire samples, and the fatigue fracture was observed and analyzed. The results showed that few cracks on the steel wire surface could be eliminated by grinding, and the fatigue life of the specimens could be increased. Finally, the stress-life-mass loss rate (S-N-η) probability model based on the Weibull distribution was obtained using the measured fatigue data, which can be further referenced in the planning of the inspection of suspender service status, steel wire corrosion protection, and fatigue life prediction, etc.

Performance of Bolt-Welded CFST Short Columns with Different Initial Imperfections: Experimental and Numerical Studies

Gap between the steel tube and core concrete of Concrete-Filled Steel Tube (CFST) members is regarded as an initial imperfection, which may exist in the CFST arch bridge due to construction process problems. In this paper, based on the design scheme of the bolt-welded joints in arch rib columns of an extra-long span CFST arch bridge, the effects of two types of initial imperfections, interfacial gap and spherical-cap gap, on the mechanical properties of Bolt-Welded CFST (BWCFST) short column under axial compression were investigated. Axial compression tests were conducted on three column specimens with spherical-cap gap, three specimens with interfacial gap, and one normal specimen without imperfection. A Finite Element Analysis (FEA) model was developed to further investigate the behavior of the BWCFST short columns, and was validated by the experiment.

Research on Hanger Force and Main Arch Stability of Long-Span Concrete-Filled Steel Tube Arch Bridge

In recent years, the construction of a CFST arch bridge has developed rapidly; however, as a kind of structural system dominated by compression, with the increase of material strength and span, the stability of the main arch of the CFST arch bridge has become more and more important. In this paper, the finite element method is used to analyze the hanger force and the main arch stability of the long-span CFST arch bridge. Combined with the Shenzhen Rainbow Bridge project, the axial force of the hanger, the internal force, and stability of the main arch of the arch bridge are studied. In the establishment of the finite element model, considering the actual operation of the arch bridge, the model simulates the interaction between steel pipe and concrete, it studies the large deformation of CFST arch bridges, and the stress distribution and overall stability of the arch bridge are analyzed. The results show that the main deformation of the CFST arch bridge is the vertical displacement of the deck, and the axial force of most members of the upper arch ribs is greater than that of the lower arch ribs. The axial force and bending moment of the lower arch rib near the arch foot are larger, and the compressive stress of the arch foot is greater than that of other positions. The axial force of the suspender of the arch bridge is the largest at both ends of the hanger and the middle hanger, and the axial force of the other hanger is close to each other, and the axial force changes little under the same case. The buckling modes of the arch are mainly the lateral buckling or flexural buckling of the arch rib outside the plane, which indicates that the vertical stiffness of the arch bridge structure is larger than that of the transverse stiffness. The research results make the load-bearing mechanism of the CFST arch bridge more clear and also provide a certain reference for the design and construction of the CFST arch bridge.

Seismic stability analysis of the large-span concrete-filled steel tube arch bridge considering the long-term effects

Creep and shrinkage of the confined concrete changes the dynamic performance of concrete-filled steel tubular (CFST) arch bridges over time. However, less attention is paid to the seismic behaviour of CFST arches considering such long-term effects. The effects of long-term behaviour on the dynamic strength of CFST arch bridges are analysed and discussed in detail in this paper. A novel dynamic stability analysis method for structures subjected to any arbitrary excitations is proposed and validated. The time-dependent properties of concrete have been numerically implemented and also the difference in concrete pouring time at different arch positions is considered. An existing large-span CFST arch bridge is analysed as a case study adopting the proposed method. Moreover, the long-term performance evolution of CFST sections are discussed. It is found that the creep-induced stress within CFST sections has a great influence on the dynamic stability of arch bridges. The critical peak ground acceleration (PGA) at the 1000th day of the service life is suggested as the reference value for the limit state under earthquake excitations. The influence of travelling wave effect and concrete pouring sequence are also investigated. Finally, the post-seismic performance of the whole bridge is evaluated.

Distributed detection of internal cavities in concrete-filled steel tube arch bridge elements

Internal cavities in structural elements, such as in concrete-filled steel tubes (CFSTs) of arch ribs reduce confinement, bearing capacity, and the durability of the arch bridges. Formation of internal cavities may be either materials related, which affects proper consolidation, or construction related, especially in terms of proper timing and delivery of concrete slurry to horizontal and inclined structural members. Nondestructive test methods such as ultrasonics have been employed for detection of internal cavities. Despite their success, point-by-point inspection of structural members becomes time-consuming and inefficient, especially when entire structures need to be inspected. Infrared thermography (IR) provides a more reasonable global approach for detection of anomalies. The accuracy and resolution of IR depend on the local ambient conditions affecting convection and external thermal flux prior to detection by IR. The research described herein pertains to the development of a hybrid thermographic approach by using Brillouin fiber optic sensors (BFOSs) for direct detection of thermal convection at the surfaces of steel tubes. Accurate quantitative detection of internal cavity locations and their dimensions required development of a specific machine learning-based approach through which the distributed thermographic data was converted to a series of grayscale images. A Faster Region-based Convolutional Neural Network (Faster R-CNN) based on the improved VGG-16 (IVGG-16) network architecture was utilized for this purpose. The experimental work involved design and fabrication of a distributed temperature sensing sheet (DTSS) for simultaneous transmission of thermal energy into CFST specimens and acquisition of distributed thermographic data by the BFOS. By using the proposed approach, it was possible to detect the embedded internal cavities during the experiments.

Optimization of Suspender Cable Force of Long-Span Concrete Arch Bridges Based on Embedded Matrix Method

In order to simplify the completion process of cable force optimization and adjustment in long-span concrete-filled steel tube arch bridges, a new method was proposed in the present study. To this end, a reasonable completion cable force calculation method was proposed based on the influence matrix principle of cable force optimization. Then combined with the mechanical characteristics of concrete-filled steel tube arch bridge, the weighted matrix was introduced to simplify the influence matrix of cable force and optimize the suspender cable force. The performed comparative study showed that the maximum difference of single cable force between the measured and calculated values is less than 5%, and the calculation error satisfies the requirements of the specification. It is concluded that the proposed method can accurately control the suspender tension construction in the arch bridge, optimize the cable force of long-span concrete filled-steel tube arch bridge, and realize the comparison and selection of various optimization schemes. The research results have been successfully applied to the suspender force adjustment of Third Pingnan Bridge, which greatly simplifies the adjustment steps and the total cable force difference in the whole bridge is 1.37%, the difference between the measured and designed suspender tensions of Heshan Hongshui River Bridge at completion state is less than 2%. The successful application of this method effectively saves the labor and material cost of suspender adjustment and further enhances the superiority of steel tube concrete arch bridge. The proposed method is expected to be an excellent choice to monitor constructions, adjust the bridge completion stage, and provide a reference for the suspender tension construction control of similar bridges.

Effect of cap gap and welded seam strength on concrete-filled steel tube arch bridge ribs

Effect of cap gap and welded seam strength on concrete-filled steel tube arch bridge ribs

Effect of cap gap and welded seam strength on concrete-filled steel tube arch bridge ribs

In this paper, the quantitative analysis is investigated for the concrete-filled steel tube (CFST) ribs strength that contained defects. The friction Coulomb model was used to investigate the interaction between the steel tube and the concrete core. Based on the non-destructive testing data, the finite element analysis is simulated with ABAQUS to obtain the strength of serviced concrete-filled steel tube ribs containing cap gaps and reduced spiral-welded seam strength which is exposed to weak eccentric axial compression. The results show that spiral-welded seam defects have weaker influence on the bearing capacity of CFST than that on empty steel tube. However, they have a significant influence on CFST local yield failure mode. The cap gap defects have effect on the shape of N-ε relationships. For CFSTs with composite defects, welded seam defects weakened local steel tube restrain capacity to concrete, resulting in CFST bending failure.

Reinforcement Effect Evaluation on Dynamic Characteristics of an Arch Bridge Based on Vehicle-Bridge Coupled Vibration Analysis

To numerically evaluate the reinforcement effect on dynamic characteristics of a concrete-filled steel tube arch bridge with vibration problems, a 12-degree-of-freedom sprung-mass dynamic vehicle model and a 3D finite element bridge model were established. Then, the coupled equations of vehicle-bridge interaction were derived and a computer program was developed using the FORTRAN language. This program can accurately simulate vehicle-bridge coupled vibration considering the bumping effect and road surface irregularity during motion of the vehicle. The simulated results were compared with those of relevant literatures to verify the correctness of the self-developed program. Then, three reinforcement schemes for the bridge (Addition of longitudinal beams, Reinforcement of bridge decks, and Replacement of suspenders) were proposed and numerically simulated, and the vibration reduction effects of the three schemes were evaluated based on the numerical results to find effective ones. It is confirmed that the reinforcement scheme of Addition of longitudinal beams shows the most significant vibration reduction effect. It is recommended in the engineering practice that the combination of the reinforcement schemes of Addition of longitudinal beams and Replacement of bridge deck can be used to solve the excessive vibration problem.

Seismic Response Analysis of Multidimensional and Multiangle Long‐Span Top‐Supported CFST Arch Bridge

Taking a concrete‐filled steel tube (CFST) arch bridge with a clear span of 400 m as an example, the in‐depth analysis of its natural vibration characteristics is carried out by establishing a finite element model. Then, the three‐dimensional El Centro recorded wave after amplitude modulation is taken as the excitation wave; the structural response under three kinds of single dimension and four kinds of multidimensional combined excitation and 0∼90° transformation X(longitudinal) + Y(transverse) orthogonal combined excitation is evaluated. The results show that the structure of long‐span top‐supported arch bridge extends in the longitudinal and vertical dimensions at the same time, and the mode shape density and mass distribution have multidirection and multiangle coupling. With the increase of excitation dimensions, the value and relative ratio of chord axial force increase. The maximum axial force ratio of X + Y to X and Y is 2.1, the maximum axial force ratio of X + Y + Z (longitudinal) to X + Y, X + Z, and Y + Z is 1.4, 1.8, and 1.8; the displacement in X and Y direction under combined excitation is independent and the displacement in Z direction is its coupling term, but the displacement under X + Y + Z combined excitation is only 10% larger than that under X + Z and Y + Z combined excitation. Under the combined excitation of X + Y with a changing angle of 0°∼90°, the axial force variation of the chord at different positions and on the same section of the arch rib has spatial characteristics. The variation range of upper and lower rod axial force varies from 0.63 to 1.35 and from 0.81 to 1.51, respectively, the change trend of displacement in the X and Y directions is relatively consistent, the change of displacement in the Z direction is asynchronous, and the displacement of vault section increases by one time. The seismic response of this bridge type under multidimensional and multiangle excitation shows obvious superposition.

Investigation on the dynamic impact factor of a concrete filled steel tube butterfly arch bridge

This study introduces the dynamic impact factor (IF) assessment of a concrete filled steel tube (CFST) butterfly arch bridge with both experimental and numerical results. The modal parameters are identified from the measured accelerations and the IFs are computed from the dynamic strain responses. Four well-known bridge design codes are applied to assess the experimental IFs. A vehicle-bridge coupled vibration system is established to numerically investigate certain effects of vehicle speed, road roughness and structural damping on the IF. Both experimental and numerical results indicate that the IFs of distinct structural components vary significantly, suggesting that a uniform formula is insufficient to describe the impact effect of the whole bridge, which has been generally adopted in many bridge design codes. For the irregular shaped CFST arch bridge, the experimental method is currently the most accurate way to determine dynamic IF. New methodologies must be developed to support the engineers to design safer complex bridges and new formulations must be developed to be part of the bridge codes.

Intelligent Active Correction Technology and Application of Tower Displacement in Arch Bridge Cable Lifting Construction

In order to control the tower deviation in the cable hoisting process of long-span concrete-filled steel tubular arch bridge during construction monitoring, a practical method of tower deviation correction was studied and established. In the paper, based on the studies about the deviation error formation mechanism of tower in the process of cable lifting, the relevant formulas of the arch rib elevation changes caused by the change of tower state were deduced. The traditional control methods including increase of tower stiffness and strength of the anchor cable, are not effective, costly, and require a longer construction period. To overcome these defects, in virtue of the Beidou GNSS measurement system and hydraulic jack active control system, the active control technology of the CFST (Concrete Filled Steel Tube) arch bridge tower deviation was thoroughly studied. Besides, a perfect active control theory was established. Finally, the author puts forward the idea of reverse pulling tower deviation. The field measurement and comparative study show that after the optimization of this method, the tower deviation is within 2 cm, and the error meets the specification requirements. The proposed method can accurately control the tower deviation in the process of arch bridge cable hoisting, and establish a set of perfect active control related systems and theories, which is especially suitable for the construction monitoring and adjustment in the construction stage of arch bridge, and can provide reference for the construction control of tower deviation of the same type of bridge.

Static and dynamic evaluation of a butterfly-shaped concrete-filled steel tube arch bridge through numerical analysis and field tests

The butterfly-shaped concrete-filled steel tube (CFST) arch bridge is an irregular bridge with unique esthetics. In this paper, this new shape of CFST arch bridge is introduced, and a refined three-dimensional finite element model (FEM) is established to evaluate static and dynamic behavior of the bridge. In order to reduce model errors, the FEM is calibrated according to numerical analysis and field tests. Static calculation results show that the butterfly-shaped bridge has good structural performance. The bending moment and axial force of the arch ribs increase when the camber angle of suspender changing from 15° to 50°. Dynamic test is carried out by ambient vibration testing under traffic and wind-induced excitations. The modal parameters of the bridge were calculated by the stochastic subspace identification method in the time domain. In terms of natural frequencies and mode shapes, the FEM analysis was validated by experimental modal analysis. The updated model thus obtained can be treated as a baseline finite element model, which is suitable for long term monitoring and safety evaluation of the structure in different severe circumstances such as earthquakes and wind loading in future.

Bayesian Updates for an Extreme Value Distribution Model of Bridge Traffic Load Effect Based on SHM Data

As the distribution function of traffic load effect on bridge structures has always been unknown or very complicated, a probability model of extreme traffic load effect during service periods has not yet been perfectly predicted by the traditional extreme value theory. Here, we focus on this problem and introduce a novel method based on the bridge structural health monitoring data. The method was based on the fact that the tails of the probability distribution governed the behavior of extreme values. The generalized Pareto distribution was applied to model the tail distribution of traffic load effect using the peak-over-threshold method, while the filtered Poisson process was used to model the traffic load effect stochastic process. The parameters of the extreme value distribution of traffic load effect during a service period could be determined by theoretical derivation if the parameters of tail distribution were estimated. Moreover, Bayes’ theorem was applied to update the distribution model to reduce the statistical uncertainty. Finally, the rationality of the proposed method was applied to analyze the monitoring data of concrete-filled steel tube arch bridge suspenders. The results proved that the approach was convenient and found that the extreme value distribution type III might be more suitable as the traffic load effect probability model.

Analysis and Comparison on Dynamic Characteristics of CFST Arch Bridge

In order to obtain the natural frequency and vibration mode of concrete-filled steel tube (CFST) arch bridge with different parameters, the modal analysis of a double-span arch bridge with a total length of 257.4 meters and a full width of 31.8 meters is carried out. By controlling the three variables of concrete strength, steel tube thickness and the number of transverse braces in arch ribs, the regularity of the natural frequency and vibration mode of CFST arch bridge with different variables is discussed. The results show that with the increasing of the strength of concrete-filled steel tube in arch ribs, the fundamental frequency increases gradually. The vertical stiffness of the arch bridge is positively related to the thickness of the arch rib steel pipe. The fundamental frequency of the arch bridge can be improved by setting transverse brace, and the change of the number of transverse braces has a significant effect on the sixth-order natural frequency. It is limited for the arch bridge to improve the stiffness by changing the number of transverse braces. These can lay the foundation for the dynamic response analysis of the CFST arch bridge.

Gray Relation Analysis for Optimal Selection of Bridge Reinforcement Scheme Based on Fuzzy-AHP Weights

In order to solve the problem on optimal selection of old bridge reinforcement schemes, a decision-making method of gray relation analysis based on fuzzy-AHP weights is proposed. Firstly, the fuzzy-AHP is used to develop the decision index system of old bridge reinforcement schemes and determine the weight of decision indexes. The 0.1–0.9 scale method is introduced as the index judgment criterion, and the weight judgment matrix is established. Through the consistency test, the relative weight vector of each decision index in the index layer is calculated. Secondly, according to the gray relation model of the old bridge reinforcement schemes, the decision matrix is constructed, and the gray relation coefficient matrix is calculated to obtain the gray relation coefficient corresponding to the ideal optimal scheme. Finally, the optimal scheme is determined. Through an engineering example, the reinforcement scheme of a concrete-filled steel tube arch bridge deck system is calculated and analyzed, and the best reinforcement scheme is selected. The optimal selection result is consistent with the actual reinforcement scheme available for the bridge. The decision-making method of gray relation analysis based on fuzzy-AHP weights make the evaluation system more organized and systematic and the index weight more operable and quantitative, reduce the subjective evaluation impact, and make the evaluation result more objective and reliable. Considering the fuzzy and gray information of comparison and selection, the optimal scheme with high feasibility and applicability is selected by the gray relation method.

Study on sling replacement of concrete-filled steel tube arch bridge

Study on sling replacement of concrete-filled steel tube arch bridge

Concrete performance time-varying effect of CFST arch bridges

Concrete-filled arch ribs of concrete-filled steel tubular (CFST) arch bridges experience temperature effects and shrinkage/creep effects, as well as effects based on their interaction, that reduce the calculated stiffness of the arch ribs of the CFST arch bridges, resulting in a reduced bearing capacity. To address this problem, this paper proposes a Gaussian process response surface method based on the concept of dichotomy. When the training sample parameter interval is uncertain, it achieves the fastest retrieval of training samples that meet the requirements, it makes up for the shortcomings of the traditional small sample Gaussian process method. It can accurately predict the equivalent stiffness of the concrete-filled arch ribs of the CFST arch bridge, considering the effects of temperature and time, and grasp the time-varying degradation law of the mechanical performance of the CFST arch bridge arch rib. To verify the correctness and reliability of the proposed method, a refined analysis model of a CFST arch bridge is established using the general finite element software ANSYS, and the optimal creep equation and temperature effect function are selected. Using the improved Gaussian process model, the equivalent calculated stiffness of the arch rib filled with concrete after ten years under the combined action of shrinkage, creep and temperature effects of the concrete-filled steel tube arch bridge is predicted, and the deflection value and stability coefficient are proposed as the evaluation index of the prediction accuracy. The research results show that the proposed method provides a more simplified and high-precision method for the performance degradation analysis of concrete filled steel tube arch bridge arch ribs under the coupling action of complex factors such as shrinkage, creep, and temperature effects.

Corrigendum to ‘‘Concrete-Filled Steel Tube Arch Bridges in China” [Engineering 4 (2018) 143–155

Corrigendum to ‘‘Concrete-Filled Steel Tube Arch Bridges in China” [Engineering 4 (2018) 143–155