Concrete-filled Steel Tubular Arch Research Articles

Application Research on Magnetic Coupling Stress Testing Technique for In-service Steel Bridge

Magnetic effect of ferromagnetic materials was discussed, the magneto-mechanical properties of ferromagnetic materials were studied, as well, Jiles Atherton constitutive mode was studied. Through the establishment of concrete filled steel tubular arch bridge structure calculation model, analysis the boom in tension and compression of the magnetic coupling. Results show that the resultant magnetic coupling model of Q345 steel derrick, the boom and load changes, the change of the magnetic parameters is more sensitive, can be better applied to the stress testing of such components.

Finite Element Analysis of Mechanical Characteristics of Arch Ribs under Vehicle Impact

In order to explore the impact of vehicle on mechanical property of arch ribs when it hits the arch foot of the arch bridge, with the 80m through truss CFST(Concrete Filled Steel Tubular) arch bridge as background, this paper uses madis/civil finite element analysis software to model by establishing two different working conditions of changing impact speed and impact angle, analyzing the changes of axial force, bending moment and vertical displacement of the left arch foot, 1/4 arch rib, 1/2 arch rib, 3/4 arch rib and right arch foot, and finally, the variation rules of mechanical characteristics of arch rib under different impact of vehicle speed and impact angle are obtained.

Research on mechanical behavior of circular concrete-filled steel tube arch joints with built-in opening stiffener

For the concrete-filled steel tubular tension nodes, the opening stiffener can effectively reduce the stress concentration of the joints and increase the ultimate bearing capacity and tensile stiffness of the joints. For the concrete-filled steel tubular arch ribs, the steel arches are subjected to both horizontal and normal forces. Open type stiffener has an important influence on the mechanical performance of the arch rib joint, and the mechanism of the joint force transmission is more complicated. Taking a bearing circular concrete-filled steel tube arch bridge as an example, a nonlinear finite element model is established by selecting arch rib joints to analyze the influence of the setting of Open type stiffeners on the mechanical properties of CFST arch joints. The results show that after the Open type stiffener is set, the failure mode of the joint is represented by the buckling deformation of the arched steel tube and the obvious deformation of the arch rib steel pipe. The Open type stiffener avoids the void of the joint steel pipe and concrete, ensuring the steel pipe and concrete at the arch rib joint. The built-in opening stiffener is an effective form of improvement for concrete-filled steel tubular arch rib joints.

Research on Wire-Broken Monitoring of Bridge cable based on Acoustic Emission technique

Acoustic emission signals generated by broken prestressed steel strand of cable can transmit up to 29.5 meters without maintaining significant attenuation of the amplitude. Therefore, the installation of a few acoustic emission sensors can comprehensively monitor the damage of the entire prestressed steel strand. Thereby, the detection of unknown defects is realized, and the structural health status can be quantitatively and quantitatively evaluated. In this paper, the acoustic emission technology is used to monitor the damage and fracture of prestressed steel strand under over tension. The acoustic emission technology is used to test the broken wires of cable of a concrete-filled steel tubular arch bridge. The correlation of the broken wires test results of the bridge is qualitatively analysed, including the stress state of the cable, the location of the measuring points and whether there is a PVC sheath at the measuring points. Therefore, a safe, reliable and efficient method is sought to monitor the damage status of the in-service cable-supported bridge.

Thermal in-plane stability of concrete-filled steel tubular arches

This paper analytically and numerically investigates the pre-buckling response and in-plane stability boundaries of circular concrete-filled steel tubular (CFST) arches subjected to combined thermal and mechanical loading. The governing non-linear equations of equilibrium are obtained using energy methods and both elastic and inelastic material behaviour is considered. A novel mechanically derived non-discretisation numerical method is proposed for the pre-buckling analysis. The stress-strain relation of the confining steel tube is described using a bi-linear plasticity model, and an inelastic material model is adopted for the concrete core which considers the effects of confinement and transient thermal strain. The result is a system of first-order differential equations which can be numerically solved with known boundary conditions including fixed ends, pinned ends or crowned-pinned cases. Closed-form solutions are presented for the elastic anti-symmetric bifurcation loads, whilst the inelastic anti-symmetric buckling strength was studied using finite element (FE) analysis. The FE model is verified by comparison to the derived analytical and numerical models which show a high level of agreement. Additionally, a sensitivity analysis is conducted which explores the influence of the constitutive material law for the concrete core and contact model for the steel-concrete interface on critical buckling loads.

Time dependent uncertain free vibration analysis of composite CFST structure with spatially dependent creep effects

• Uncertain free vibration analysis of composite concrete filled steel tubular structure is investigated. • Spatially dependent uncertain creep effect of the concrete core is considered. • Interval field model is adopted to model the spatially dependent uncertain parameters. • Robust bounds of natural frequencies of the structure can be determined. In this study, the time dependent free vibration analysis of composite concrete-filled steel tubular (CFST) arches with various uncertainties is thoroughly investigated within a non-stochastic framework. From the practical inspiration, both uncertain material properties and mercurial creep effect associated with such composite materials are simultaneously incorporated. Unlike traditional non-probabilistic schemes, both spatially independent (i.e., conventional interval models) and dependent (i.e., interval fields) interval system parameters can be comprised within a unified uncertain free vibration analysis framework for CFST arches. For the purpose of achieving a robust framework of the time-dependent uncertain free vibration analysis, a new computational approach, which has been developed within the scheme of the finite element method (FEM), has been proposed for determining the extreme bounds of the natural frequencies of practically motivated CFST arches. Consequently, by successfully solving two eigenvalue problems, the upper and lower bounds of the natural frequencies of such composite structures with various uncertainties can be rigorously secured. The unique advantage of the proposed approach is that it can be effectively integrated within commercial FEM software with preserved sharp bounds on natural frequencies for any interval field discretisation. The competence of the proposed computational analysis framework has been thoroughly demonstrated through investigations on both 2D and3D engineering structures.

Evaluation on ultimate load-carrying capacity of concrete-filled steel tubular arch structure with preload

When casting wet concrete into hollow steel tubular arch during the construction process of a concrete-filled steel tubular arch bridge, an initial stress (due to dead load, etc.) would be produced in the steel tube. In order to understand the influence of this initial stress on the strength of the concrete-filled steel tubular arch bridge, a total of four single tubular arch rib (bare steel first) specimens (concrete-filled steel tubular last) with various initial stress levels were constructed and tested to failure. The test results indicate that the initial stress has a large influence on the ultimate load-carrying capacity and ductility of the arch structure. The high preloading ratio will reduce significantly the strength and ductility that the maximum reductions are over 25%. Then, a finite element method was presented and validated using the test results. Based on this finite element model, a parametric study was performed that considered the influence of various parameters on the ultimate load-carrying capacity of concrete-filled steel tubular arches. These parameters included arch slenderness, rise-to-span ratio, loading method, and initial stress level. The analysis results indicate that the initial stress can reduce the ultimate loading capacity significantly, and this reduction has a strong relationship with arch slenderness and rise-to-span ratio. Finally, a method for calculating the preloading reduction factor of ultimate load-carrying capacity of single concrete-filled steel tubular arch rib structures was proposed based on the equivalent beam–column method.

Dynamic Parameter Identification of a Long-Span Arch Bridge Based on GNSS-RTK Combined with CEEMDAN-WP Analysis

Under the action of wind, traffic, and other influences, long-span bridges are prone to large deformation, resulting in instability and even destruction. To investigate the dynamic characteristics of a long-span concrete-filled steel tubular arch bridge, we chose a global navigation satellite systems-real-time kinematic (GNSS-RTK) to monitor its vibration responses under ambient excitation. A novel approach, the use of complete ensemble empirical mode decomposition with adaptive noise combined with wavelet packet (CEEMDAN-WP) is proposed in this study to increase the accuracy of the signal collected by GNSS-RTK. Fast Fourier transform (FFT) and random decrement technique (RDT) were adopted to calculate structural modal parameters. To verify the combined denoising and modal parameter identification methods proposed in this paper, we established the structural finite element model (FEM) for comparison. Through simulation and comparison, we were able to draw the following conclusions. (1) GNSS-RTK can be used to monitor the dynamic response of long-span bridges under ambient excitation; (2) the CEEMDAN-WP is an efficient method used for the noise reduction of GNSS-RTK signals; (3) after signal filtering and noise reduction, structural modal parameters are successfully derived through RDT and illustrated graphically; and (4) the first-order natural frequency identified by field measurement is slightly higher than the FEM in this work, which may have been caused by bridge damage or the inadequate accuracy of the finite element model.

AN INVESTIGATION INTO WORKING BEHAVIOR CHARACTERISTICS OF PARABOLIC CFST ARCHES APPLYING STRUCTURAL STRESSING STATE THEORY

This paper conducts the experimental and simulative analysis of stressing state characteristics for parabolic concretefilled steel tubular (CFST) arches undergoing vertical loads. The measured stain data is firstly modeled as the generalized strain energy density (GSED) to describe structural stressing state mode. Then, the normalized GSED sum Ej,norm at each load Fj derives the Ej,norm-Fj curve reflecting the stressing state characteristics of CFST arches. Furthermore, the Mann-Kendall criterion is adopted to detect the stressing state change of the CFST arch during its load-bearing process, leading to the revelation of a vital stressing state leap characteristic according to the natural law from quantitative change to qualitative change of a system. The revealed qualitative leap characteristic updates the existing definition of the CFST arch’s failure load. Finally, the accurate formula is derived to predict the failure/ultimate loads of CFST arches. Besides, a method of numerical shape function is proposed to expand the limited strain data for further analysis of the stressing state submodes. The GSED-based analysis of structural stressing state opens a new way to recognize the unseen working behavior characteristics of arch structures and the updated failure load could contribute to the improvement on the structural design codes.

上承式钢管混凝土拱桥钢管生命全过程应力状态分析

上承式钢管混凝土拱桥钢管生命全过程应力状态分析

Level 2 safety evaluation of concrete‐filled steel tubular arch bridges incorporating structural health monitoring and inspection information based on China bridge standards

Concrete-filled steel tubular (CFST) arch bridges have been widely used in mainland China, and their systematic safety evaluation has gained increasing attention from the bridge authorities in recent years. This paper presents the framework and application of Level 2 safety evaluation of CFST arch bridges, incorporating structural health monitoring (SHM) and inspection information. In contrast with the traditional inspection-based qualitative assessment and direct measurement-based quantitative assessment for SHM, Level 2 safety evaluation considers the inevitable resistance deterioration and site-specific loading under normal operation conditions. For such safety evaluations, the most important element is using the well-established finite element modelling for representing the actual conditions as accurately as possible. Thus, in this study, component and global finite element model (FEM) updating techniques are employed to ensure the local and global behaviour of the updated FEM, through which several types of common CFST arch bridge defects are investigated and updated. Measured site-specific live loads experienced by CFST arch bridges are considered and transformed into design loads for comparison. Unfavourable load patterns are applied to the updated FEM for structural reanalysis, to evaluate the component safety status, and gradually increasing unfavourable load patterns are applied to the FEM to perform an ultimate load-bearing analysis to obtain the global safety reservation. Level 2 safety evaluation is conducted by considering modal parameters, displacements, fatigue damage, and component and global safety status. Level 2 safety evaluation is applied to a typical CFST arch bridge, to demonstrate the entire evaluation process and the effectiveness of the proposed safety evaluation framework.

Seismic behavior of long-span concrete-filled steel tubular arch bridge subjected to near-fault fling-step motions

Special characteristics of earthquakes in the near-fault regions, mainly fling-step and forward-directivity effects, may result in the significant damage to long-span bridge. In this paper, investigations are performed to analyze the seismic behaviors of the long-span concrete-filled steel tubular arch bridge called Zangmu Bridge under fling-step motions. Firstly, a three-dimensional finite-element model for the bridge is constructed with proper consideration of the material and geometric nonlinearities; secondly, three kinds of seismic loadings are comprehensively illustrated including recorded ground motions, idealized pulse models and residual components; then, comparative analysis and parametric analysis are conducted to gain insight into the effect of different components in fling-step motions on the seismic response; finally, the potentially dangerous locations of the CFST arch are estimated by taking the strain index as performance evaluation standard. Findings from the studies reveal that fling-step motions consist of static and dynamic pulses, both of which possess significant influence on the seismic response and performance state; the seismic demands depend on both pulse period and pulse amplitude; and the 'narrow band' effect for different members appears at different pulse periods related to the mode contribution.

Simulation Calculation and Monitoring of Deformation of Concrete-Filled Steel Tube Arch Bridge

Concrete-filled steel tubular arch bridge is a relatively new structure system, because of its unique mechanical properties, it has a good advantage in the construction of modern Bridges. In the course of construction, the arch rib axis and the system beam will have the upper and lower deformation. If improper linear control, the compression performance of the material cannot be fully played after the arch rib is formed, which has a great influence on the state of the bridge. In order to make the arch axis of the bridge more reasonable, this paper takes a concrete-filled steel tube arch bridge with a span 60m as an example. Through theoretical analysis and monitoring, it is found that the line shape control of the bridge is reasonable in the construction stage; the line shape of the bridge stage is basically consistent with the design expectation, and the line type is smooth, the multiple cable adjustment is eliminated and the expected target of the construction period is reduced.

Dynamic Performance of Strengthened Concrete-Filled Steel Tubular Arch Bridge due to Moving Vehicles

AbstractA strengthened concrete-filled steel tubular (CFST) arch bridge which has experienced serious damage due to long-term heavy-truck action is studied. An in-depth study of the dynamic perform...

Study of creep effects in a long-span concrete-filled steel tube arch bridge

This paper reports how modelling experiments, theoretical analysis, finite-element analysis and in situ measurement were employed to research the effects of creep in a long-span concrete-filled steel tubular arch bridge in China. First, a creep experiment using a 1 : 2·5 scaled model of the arch-foot segment was carried out to investigate time-dependent behaviours. Experimental results showed that the creep strains of the arch developed very rapidly at the start of loading, but grew very slowly later. Subsequently, two theoretical analysis methods were used to determine creep coefficients of the arch members, considering the steel tubular confining effects and stress distribution, as well as the effects of the ratio of sectional areas and elastic modulus of steel and concrete. The calculated values of the two theoretical methods were in general agreement with the experimental results. It can be concluded from the in situ measured stress data that concrete stresses reduced and steel stresses, conversely, increased with time. Concrete compressive stresses from the in situ measurement were smaller, with some even being negative.

In-Plane Stability of Concrete-Filled Steel Tubular Parabolic Truss Arches

For determining the in-plane buckling resistance of a concrete-filled steel tubular (CFST) arch, the current technical code GB50923-2013 specifies the use of an equivalent beam-column method which ignores the effect of rise-to-span ratio. This may induce a gap between the calculated result and actual stability capacity. In this study, a FE model is used to predict the buckling behavior of CFST truss arches subjected to uniformly distributed loads. The influence of rise-to-span ratio on the capacity of truss arches is investigated, and it is found that the stability capacity reduces as rise-to-span ratio declines. Besides, the calculations of equivalent slenderness ratio for different truss sections are made to consider the effect of shear deformation. Moreover, based on FE results, a new design equation is proposed to predict the in-plane strength of CFST parabolic truss arches under uniformly distributed loads.

Out-plane stability safety factors of CFST arches using inverse finite element reliability method

Concrete filled steel tubular arch (CFST) bridges have been widely used in China since the 1990s. However, researches on the stability design of this type of bridges are limited, especially for the out-plane stability. Therefore, a numerical inverse finite element reliability method is presented to solve the problem. In this method, safety factors are introduced into the limit state equations. The cooperation of programming and general finite element software is utilized to implement the method. For different target reliability indices, out-plane stability safety factors of CFST arches considering nonlinearities are obtained via the method. The results show that: the method is of good efficiency and applicability; steel ratios and lateral loads have significant influences on the safety factors; the effects of resistance and load uncertainties on the factors are important which should be concerned in stability design of CFST arch bridges.

Structural Behaviors of Large Span Prestressed PC Bridge Stiffened by CFST Arch

High-speed railway system has been developed with unprecedented pace in recent decades. Various type of bridges (elevated structures) were built for high speed railway infrastructure due to land saving and sound operational condition provided. In this paper, the detailed modeling of the prestressed concrete girder stiffened by concrete filled steel tubular (CFST) arch was developed. Displacement, static stress, dynamic characteristics was obtained by analysis. The overall structural performance has been concluded.

Arch-Axis Coefficient Optimization of Long-Span Deck-Type Concrete-Filled Steel Tubular Arch Bridge

This paper is based on Nanpuxi super major bridge which is under construction and starts from Wencheng Zhejiang province to Taishun highway. A finite element model of the whole bridge is constructed using Midas Civil finite element software. The most adverse load combination in the specification is taken into consideration to determine the method of calculating the arch-axis coefficient of long-span deck-type concrete-filled steel tubular arch bridge. By doing this, this paper aims at providing references for similar engineering projects.

Static and Dynamic Structural Performances of a Special-Shaped Concrete-Filled Steel Tubular Arch Bridge in Extreme Events Using a Validated Computational Model

Recently, Yingzhou Bridge with a main span of 120 m has been built in Luoyang, China. Although the bridge’s unique concrete-filled steel tubular arch-rib system satisfies the aesthetic demand of the public, the innovative structure’s mechanics behaviors in extreme events are unknown yet, including both static and dynamic structural performances. To this end, numerical analyses have been undertaken based on ANSYS finite-element (FE) platform (version 9.0). A simplified computational FE model is established and effectively updated using reference information obtained from a detailed FE model. Using the validated simplified FE model, the bridge’s stability, ultimate load-carrying capacity and seismic performance are studied considering the original design and several modified designs. It is found that the bridge’s performances basically meet the design requirements; however, the structure’s lateral stability and stiffness are relatively weak for the original design. Adding K-shaped struts and reducing subarches’ angle of inclination can effectively solve this problem.