Thin-walled Box Girder Bridges Research Articles

STUDY ON SPATIAL STRESS EFFECT OF PC CONTINUOUS THIN-WALLED BOX GIRDER BRIDGE

In order to study the influence of spatial stress effect and shear lag effect on the cracking of PC continuous thin-walled box girder bridge, a spatial model was established by using ANSYS finite element software to analyze the internal stress distribution of the bridge. The test results are compared with the analysis results of spatial model and plane link system model through the load test of real bridge. The results show that the longitudinal stress is evenly distributed along the width direction, which means that the spatial stress effect and the shear lag effect have little influence on the downdeflection of the bridge. The shear lag coefficient at the longitudinal axis of midspan bottom plate and the intersection of bottom plate and web are larger than other positions, which is most likely to produce cracks caused by stress concentration, and should be strengthened here in practical engineering. The results of load test show that the results of spatial finite element analysis are more reliable than those of plane link system calculation, and the design and construction based on the results of spatial finite element analysis is safer.

Scanning torsional-flexural frequencies of thin-walled box girders with rough surface from vehicles’ residual contact response: Theoretical study

This paper studies theoretically the retrieval of torsional-flexural frequencies of mono-symmetric thin-walled box girder bridges from vehicles’ residual contact response for the first time. To start, the three-dimensional vehicle–bridgeequations of motion including the lateral and torsional (coupled) and vertical (uncoupled) vibrations are derived for a moving test vehicle. Then, closed-form solutions for the vehicle and vehicle–bridge contact point are derived. The contact response is selected since it is free of vehicle frequency, which may overshadow the bridge frequencies in FFT spectra. The other disturbing factor is surface roughness, which will be resolved by the residue method, i.e., by using the residual response of two connected vehicles. Through the parametric study, the proposed approach is verified to be feasible. The conclusions include: (1) the contact response performs better than the vehicle response for all the scenarios considered; (2) the surface roughness effect can be virtually eliminated using the residual contact response even for damped bridges with not-so-good pavements; (3) a larger vehicle’s eccentricity from bridge’s centerline enables the torsional-flexural frequencies to be better identified; and (4) the first several flexural and torsional-flexural frequencies of the girder can always be identified for a wide variety of parameters considered.

Analytical observability method for the structural system identification of wide-flange box girder bridges with the effect of shear lag

In the field of bridge structural system identification (SSI), Bernoulli beam element models are often used to solve inverse problems. More rarely, Timoshenko beam element models can be calibrated. However, these models account for only the general shear effects, whereas other shear effects, such as shear lag, are not accounted for. However, as wide-flange box girder bridges become prevalent due to design demands, neglecting shear lag may introduce significant errors in predicting the mechanical parameters of the system and, hence, reduce the accuracy. In this paper, for the first time, the shear lag's effect on the vertical deflections is taken into account in an inverse problem. A parametric SSI, the observability method (OM), is updated to address the identification of thin-walled box girder bridges with wide flanges, including the shear lag effects. The structural analytical equations are used to connect the spatial shear effects with the beam-unidimensional-element model to be applied in the inverse analysis, which is referred to as the analytical observability method (AOM-SSI). This updated version of the OM is established and validated to identify the mechanical parameters of a structural test. The identified mechanical parameters show much better agreement with the expected results than those obtained with previous methods.

Free vibration behaviour of thin-walled concrete box-girder bridge using Perspex sheet experimental model

Purpose: Curved box-girder bridges offers an excellent solution to the problems associated with traffic congestion. However, owing to their complex geometry, they are subjected to shear lag, torsional warping and cross-sectional distortion, which must be assessed in their study and design. Furthermore, the dynamic behaviour of curved bridges adds to the complexity of the issue, emphasizing the importance of studying free vibration. The purpose of this study is to numerically model the concrete curved box-girder bridge considering torsional warping, distortion and distortional warping effects and to identify key parameters that influence the free vibration response of the box-girder bridge by validating it with experimental and analytical studies. Design/methodology/approach: The concrete bridge is numerically modelled by means of computationally effective thin-walled box-beam finite elements that consider torsional warping, distortion and distortional warping, which are prominent features of thinwalled box-girders. The free vibration analysis of the concrete curved box-girder bridge is performed by developing a finite element based MATLAB program. Findings: The identification of critical parameters that influence the free vibration behaviour of curved thin-walled concrete box-girder bridges is one of the main findings of the study. Each parameter and its effect has been extensively discussed. Research limitations/implications: The study limits for the preliminary design phase of thin-walled box-girder bridge decks, where a complete three-dimensional finite element analysis is unnecessary. The current approach can be extended to future research using a different method, such as finite element grilling technique on multi-span curved bridges having unequal span.

Spatial Finite Element Analysis for Dynamic Response of Curved Thin-Walled Box Girder Bridges

According to the flexural and torsional characteristics of curved thin-walled box girder with the effect of initial curvature, 7 basic displacements of curved box girder are determined. And then the strain-displacement calculation correlations were established. Under the curvilinear coordinate system, a three-noded curved girder finite element which has 7 degrees of freedom per node for the vibration characteristic and dynamic response analysis of curved box girder is constructed. The shape functions are used as the interpolation functions of variable curvature and variable height to accommodate to the variation of curvature and section height. A MATLAB numerical analysis program has been implemented.

Numerical and Experimental Modeling of the Static Response of Simply Supported Thin-Walled Box Girder Bridges

This paper presents numerical and experimental modeling of the static response of simply supported thin-walled reinforced concrete box girder bridges. The work is executed to verify the validity of software developed by the authors for the finite strip analysis of continuous thin-walled box girder bridges and also to observe the effect of flange width on the static response of these type of structural elements under service load from experimental and numerical studies. The laboratory load/deformation relationship is presented in the form of deflection ratios that is displayed alongside the finite strip analysis results of the same loading condition. The results obtained from the laboratory experiment and the software showed very good agreement and are, averagely, 21.5% and 19.5% higher than that of the beam theory solution respectively. Verification of the software with published solutions is also conducted. The results from the developed software showed very good agreement with literature in terms of deflection and stress distributions. These results suggest that the effect of shear deformation, which is more significant on deflection than on stresses, increases with increase in flange width and that the developed software is capable of capturing the general behavior of thin-walled box girder bridges. http://dx.doi.org/10.4314/njt.v34i4. 4

Review of Elastic Analysis of Box Girder Bridges

The importance of thin-walled box girder bridges has attracted the attention of researchers since the last five decades. A lot of literature has dealt with the analytical formulations as well as experimental investigations. Field studies have increased tremendously in the last decade. So far the agreement between the analytical and experimental results has been excellent and, therefore, has made it possible to augment a limited number of experimental tests with hundreds of analytical studies. Highlights of research efforts in published literature regarding the analysis methods and experimental studies related to the elastic analysis of box girder bridges have been presented in this review. Subjects discussed include: (1) Thin –Walled Curved Beam Theory; (2) BEF/EBEF Method; (3) Finite Segment Method; (4) Folded Plate Method; (5) Finite Difference Method; (6) Energy Variational Principle; (7) Grillage Analogy and Space Frame Methods; (8) Finite Element Method; (9) Finite Strip Method; (10) Simplified/Miscellaneous Methods; (11) Experimental Studies. http://dx.doi.org/10.4314/njt.v34i1.10

Stress Distribution in Continuous Thin-Walled Multi-Cell Box Girder Bridges

Several researchers have studied stresses in thin-walled box girder bridges but stress distribution in continuous thin-walled multi-cell box girder bridges has not received much attention in published literature. Hence, this research investigated stress distribution in continuous thin-walled multi-cell box girder bridges. Analysis of box girder bridges is complex and the complexity is even more when the box girder is continuous with multi-cells. The modern trend in the analysis is to program the more straightforward methods for ease of computer application. Therefore, the analytical tool for this study is a MATLAB program developed by the authors for the finite strip analysis of continuous thin-walled box girder bridges. Numerical study on stress distribution was carried out on two box girder bridges. The first was a simply supported box girder bridge subjected to eight point loads which was used primarily for comparison with literature. The result obtained by the program was in good agreement with literature. The second was a continuous thin-walled multi-cell box girder bridge subjected to vehicular loads and self weight. The beam theory solution was also used for comparison of results in both cases. The study concluded that under symmetrical loading the longitudinal normal stress, shear stress at end supports, transverse bending moment, and longitudinal bending moment are substantial while the transverse normal stress and twisting moment are negligible. The program can, therefore, be used in practice to determine stress distributions of box girders and prismatic folded plates. However, classical finite strip underestimates stress values at points of high stress concentration. http://dx.doi.org/10.4314/njt.v33i4.5

Mechanical Properties Analysis of CFRP Pre-Stressed Section Continuous Thin-Walled Box Girder Bridge Models 22

An externally pre-stressed continuous box girder bridge model is designed according to loading features of the continuous beam. The CFRP bars and steel strands are used to make two models for externally pre-stressed reinforcements Analysis of the two models under three different load stiffness and loss of prestress, through calculation and analysis, found that two kinds of prestressed concrete material model under three load deflection basic same, also almost the same change trend, prestressed RMS model than model 1, 2 but with the increase of load model 2 prestress loss is big. Analysis results of CFRP materials and application to provide the reference in the bridge.

Stress Analysis of High Thin-Walled Box Girder Bridge in Chong He Bridge

Based on the Chong He Bridge as research object, this paper expounds the purposes, methods and analysis results of prestressed concrete continuous thin-walled box girder bridge in the process of cantilever construction. The purpose of the research is to make a reasonable structure which meets the designed stress monitoring and to ensure the quality of construction. The method is to layout stress control points in the main control section and conduct real-time control. The result shows that the beam stress is within the safety range and can predict that the structure meets strength requirements in next stage. The conclusion is that through the data analysis, the results guide the whole process of bridge construction as well as fit the design plan.

Simplified Analysis of Longitudinal Stiffened Plates in a Continuous Steel Box Girder Bridge

This paper investigates the thin-walled box girder bridges with large width-to-span ratios through both experimental and numerical studies. For the complexity of the bridge, different discrete models are presented in the analyzing of the longitudinal stiffened plate. In addition, a large-scale Plexiglas model is tested under different loading cases. The simplified simulation of the computation results compared well with the experimental results. It is illustrated that it is an effective method to predict properties of this kind of bridges.

Experimental and analytical studies on a streamlined steel box girder

A new type of streamlined girder ( lenticular cross-section) bridge with a thin-walled steel box girder is proposed. In order to deal with the problem of increasing traffic congestion, this bridge is designed with a large width-to-span ratio, which results in significant shear lag effects and causes non-uniform stress distribution in the three-cell thin-walled box girder, especially along the flanges of the girder. The aim of this study is to investigate the effect of shear lag in thin-walled box girder bridges with large width-to-span ratios through both experimental and numerical studies. A large-scale Plexiglas model is tested under different loading cases. The material parameters are obtained from physical characteristics tests and tensile tests. In addition, a computational model is presented for a comprehensive simulation of a girder bridge including the orthotropic top/bottom/web plates and their ribs, which leads to accurate modeling of structural properties of the girder. The simulation of the computation results compared well with the experimental results. It is illustrated that the finite element analysis is an effective method to predict properties of this class of bridges.

Theoretical analysis of Y-shape bridge and application

Mechanic behavior of Y-shape thin-walled box girder bridge structure is complex, so one can not exactly hold the mechanical behavior of the Y-shape thin-walled box girder bridge structure through general calculation theory and analytical method. To hold the mechanical behavior better, based on elementary beam theory, by increasing the degree of freedom analytical method, taking account of restrained torsiondistortion angledistortion warp and shearing lag effect at the same time, authors obtain a thin-walled box beam analytical element of 10 degrees of freedom of every node, derive stiffness matrix of the element, and code a finite element procedure. In addition, authors combine the obtained procedure with spatial grillage analytical method, meanwhile, they build a new analytical method that is the spatial thin-walled box girder element grillage analysis method. In order to validate the precision of the obtained analysis method, authors analyze a type Y-shape thin-walled box girder bridge structure according to the elementary beam theory analytical method, the shell theory analytical method and the spatial thin-walled box girder element grillage analysis method respectively. At last, authors test a type Y-shape thin-walled box girder bridge structure. Comparisons of the results of theory analysis with the experimental text show that the spatial thin-walled box girder element grillage analysis method is simple and exact. The research results are helpful for the knowledge of the mechanics property of these Y-shape thin-walled box girder bridge structures.

Fatigue life prediction of horizontally curved thin walled box girder steel bridges

The fatigue damage accumulation rates of horizontally curved thin walled box-girder bridge have been estimated from vehicle-induced dynamic stress history using rain flow cycle counting method in the time domain approach. The curved box-girder bridge has been numerically modeled using computationally efficient thin walled box-beam finite elements, which take into account the important structural actions like torsional warping, distortion and distortional warping in addition to the conventional displacement and rotational degrees of freedom. Vehicle model includes heave-pitch-roll degrees of freedom with longitudinal and transverse input to the wheels. The bridge deck unevenness, which is taken as inputs to the vehicle wheels, has been assumed to be a realization of homogeneous random process specified by a power spectral density (PSD) function. The linear damage accumulation theory has been applied to calculate fatigue life. The fatigue life estimated by cycle counting method in time domain has been compared with those found by estimating the PSD of response in frequency domain. The frequency domain method uses an analytical expression involving spectral moment characteristics of stress process. The effects of some of the important parameters on fatigue life of the curved box bridge have been studied.

Dynamic Behavior of Continuous and Cantilever Thin-Walled Box Girder Bridges

The free vibration characteristics and the dynamic response to a multivehicle load moving across rough bridge deck of continuous and cantilever thin-walled box girder bridges are studied. The box girder bridge is divided into a number of thin-walled beam elements. Both warping torsion and distortion are considered in the study. The analytical vehicle is simulated as a nonlinear vehicle model with 11 independent degrees of freedom according to the HS20-44 truck design loading contained in the AASHTO specifications. Four different classes of road-surface roughness generated from power spectral density function for very good, good, and average roads are used in the analysis. One continuous and two cantilever three-span box girder bridges are designed based on the AASHTO specifications. The dynamic responses of the bridges are evaluated for single truck, three, and six trucks, with different speeds and road surface roughness. The analytical results show that the effects of different loading models, road surface profiles, and vehicle speeds on the dynamic response for different types of bridges are quite different. The most important factor which affects the impact of cantilever bridges is the vehicle speed. namic characteristics and impact of continuous and cantilever box girder bridges with different vehicle models, road surface roughnesses, as well as vehicle speeds. In the present study, the bridge is modeled as a thin-walled structure with deform­ able cross sections. The traveling vehicle is treated as a non­ linear space model. Multitruck loading is considered in both transverse and longitudinal directions of the bridge. The results obtained in this study are significant for both practical bridge design and further theoretical study of continuous and canti­ lever box girder bridges.

Analysis of continuous box girder bridges including the effects of distortion

Torsional warping and distortion of the cross-section are important features of thin-walled beams and must be considered fully in the design of box girder bridges. A method of elastic analysis is developed based on the stiffness approach which includes the effects of warping torsion and distortion in addition to the more familiar actions of bending moment and torsion. The method, which is applicable to straight single cell box girders with at least one axis of symmetry, is demonstrated here in the analysis of three different box girder models for which experimental or analytical results were already available. The method is shown to be easy and economical to use and provides a physical insight into the structural response of thin-walled box girder bridges under general loading conditions.

Parallel Programming And Parallel Execution Of ANew Formulation For The Finite Element Analysis OfBox Girder Bridges

This paper addresses the results of a researeh on a Finite Element Parallel Formulation for the Structural Analysis of Thin-walled Box Girder Bridges and its implementation in the GLU Programming Environment. This new formulation whieh is based on plane stress quadrilateral quadratic elements has demonstrated that it is well suited to Coarse-grain Parallel processing.