Box Girder Cross-section Research Articles

A Study of the Mechanical Properties of Polyester Fiber Concrete Continuous Rigid Frame Bridge during Construction

This study investigates the mechanical performance of a polyester fiber concrete continuous rigid frame bridge during construction and the spatial stress distribution of the 0# block box girder, with a focus on the backdrop of the bridge in Pipa Zhou, Jiangxi Province. Stress monitoring at critical cross-sections during bridge construction was combined with FE simulations to analyze the stress and alignment deviation variations along the cantilevered construction process of the bridges. Subsequently, after validating the accuracy of the whole bridge model, the actual internal force of the box girder cross-section was extracted to act on the 0# block box girder solid model, and the spatial force of the 0# block box girder under the state of maximal cantilever and the completed bridge was further investigated. The results indicate that during cantilever construction, the top, and bottom plates of the box girder were subjected to compression, with the bottom plates having relatively low compression stress close to the critical values for compression and tension. Attention should be paid to controlling tensile stress application. After reaching a quarter of the bridge’s span in construction, the alignment deviation of the main beam increases, necessitating enhanced monitoring and adjustments of the main beam elevation. Furthermore, FE analysis shows that under maximum cantilever and the completed bridge states, the stress variations of the top and bottom plates of the 0# block box girder remain consistent, with the top plate stress varying by no more than 2.5 MPa and the bottom plate stress varying by approximately 1 MPa. Moreover, the 0# block box girder shrinkage cracks were mainly located in the bottom and web plate, and the number of cracks in the 0# block box girder with polyester fibers was reduced compared to the cracks in the ordinary concrete box girder.

Intelligent Identification and Verification of Flutter Derivatives and Critical Velocity of Closed-Box Girders Using Gradient Boosting Decision Tree

Flutter derivatives (FDs) of the bridge deck are basic aerodynamic parameters by which flutter analysis determines critical flutter velocity (CFV), and they are traditionally identified by sectional model wind tunnel tests or computational fluid dynamics (CFD) numerical simulation. Based on some wind tunnel testing results and numerical simulation data, the machine learning models for identifying FDs of closed-box girders are trained and developed via a gradient boosting decision tree in this study. The models can explore the underlying input–output transfer relationship of datasets and realize rapid intelligent identification of FDs without wind tunnel tests or numerical simulation. This method also provides a convenient and feasible option for expanding datasets of FDs, and the distribution of FDs can be analyzed through the post-interpretation of trained models. Combined with FD sensitivity analysis, the models can be verified by the calculation error of CFV. In addition, the proposed method can help determine the appropriate shape of the box girder cross-section in the preliminary design stage of long-span bridges and provide the necessary reference for aerodynamic shape optimization by modifying the local geometric features of the cross-section.

Comparison of the Ultimate Strength with and without Hatch Opening Subjected to Longitudinal Bending

The hatch opening has function to enter the load into the cargo hold. One of the ship type like this is Bulk Carrier. The hatch opening must be designed in suitable way because its influence to the ultimate strength since the hull girder under longitudinal bending moment. The application of the hatch opening on the ship’s deck should be considered for the ship design critreria. The objective of the present study is to analyze the ultimate strength with and without hatch opening subjected to longitudinal bending moment. The cross section of box girder is used to analyze the effect of hatch opening to the ultimate strength. This cross section of box girder is adopted for simple calculation. The application of Multiple Point Constrained (MPC) is adopted to analyze the box girder under longitudinal bending moment. The cross section of box girder is assumed remained plane during progressive collapse. The material such as density, yield strength, elastic modulus and poisson ratio are homogeneous. The type and dimensions of the stiffeners are also identic. The only one of the difference for the stiffener is number due to the hatch opening at the top of the box girder. It is found that the ultimate strength of the box girder with hatch opening is smaller than without opening one.

Comparison of the level of required prestressing of road bridges according to the historical development of technical standards in Slovakia

The paper deals with the level of required prestressing designed for box-girder bridges. Mainly focuses on the development of standards used in the design of prestressed concrete road bridges in the Slovak Republic. The standards for bridge design have been amended several times. A parametric study was performed on a model post-tensioned concrete bridge with a box-girder cross-section. The bridge has three-span with a main span of 50 m and end spans of 40 m. The study compares the normal stresses caused by traffic load along the length of the bridge according to various standards and technical regulations. The differences in design principles were investigated while the amount and geometry of the longitudinal prestressing of the bridge were changed as required by corresponding standards. The numerical model is considered as a beam element with neglecting of the torsional effects of the load. The parametric study points out the differences in the normal stresses along the bridge according to different design regulations and standards. The aim of the study is to compare level of prestressing according to the historical development of prestressed bridges

Effect of Load Combinations on Distortional Behaviors of Simple-Span Steel Box Girder Bridges

When eccentric live loads are applied on the deck overhang of steel-box girder bridges, torsional moments, comprising pure torsional and distortional moments are generated on the box sections. The torsional moment on the bridge girders distorts the box girder cross-sections, inducing additional normal stress components and causing instability of the box girder sections in severe cases. Hence, it is essential to install intermediate diaphragms in the box sections to minimize distortional behaviors. Although the applied live loads are critical parameters that influence intermediate diaphragm spacings, the effects of live load combinations have rarely been addressed in the design of intermediate diaphragm spacings. Thus, load combinations should be evaluated to design the intermediate diaphragm spacing of the box girder bridges more thoroughly. In this study, the load combination effects on the distortional behavior and adequate intermediate diaphragm spacing were evaluated through a finite element analysis (FEA). Composite rectangular box girder bridges with different cross-sectional aspect ratios (H/B) and spans (L) were analyzed in the parametric study. It was found that the truck load, which represents the concentrated load, significantly influences the distortional warping normal stress, normal stress ratio, and intermediate diaphragm spacing. In addition, the FEA results showed that the controlling load combinations could be varied with the span.

Study on Solar Radiation and the Extreme Thermal Effect on Concrete Box Girder Bridges

Thermal effect is an essential factor in the durability and safety of concrete bridges. Therefore, this paper mainly studied the concrete bridge box girder temperature distribution and thermal effect under solar radiation and the thermal load. With a concrete rigid frame bridge as the engineering background, the temperature distribution of the box girder on a clear summer day was observed. Then, according to the solar physics and heat transfer theory, the different surfaces of the box girder cross-section are classified based on the heat transfer conditions, and the variation of solar radiation on different surfaces is investigated. The temperature field of the box girder is simulated by ANSYS. To obtain the extreme thermal condition, the meteorological data of the bridge site from 1990 to 2020 are collected. The data are fitted by generalized extreme value distribution to obtain the extreme temperature and average wind factors in the bridge design lifetime. Combined with the solar radiation, temperature, and wind factors, the extreme thermal condition of the concrete box girder is obtained. Lastly, the thermal effect of the box girder under the extreme condition is analyzed, and the thermal stress is compared with the allowable stress in the design code. The results show that the girder temperature difference is closely related to the solar radiation intensity and heat transfer conditions, and the solar radiation intensity is the more critical factor. The tensile stress caused by the extreme thermal load is more significant than the design strength value in the girder cross-section. The results also provide a method to obtain the extreme thermal condition and evaluate the impact of the thermal effect on concrete box girder bridges.

Numerical Study on the Mechanical Properties of the Novel Wide Box Girders Stiffened by Transverse Ribs

The dimensioning of the cross section is a critical step in designing wide box girder bridges with long cantilevers. The typical box girder cross section may not be the most economical and reasonable choice for wide box girder bridges considering the stress conditions and construction costs. Arranging transverse stiffened ribs underneath the top slab is an effective way to widen the bridge deck. In this study, the influence of the transverse stiffened ribs on the mechanical performance of the ribbed top slab is investigated by finite element (FE) modelling. The results show that the transverse mechanical properties of the box girders with ribbed slabs are significantly different from those of the traditional box girders with solid slabs. The ribbed slabs can provide additional transverse capacities over those of the traditional solid slabs. Furthermore, the transverse tensile stress in the root section of the ribbed cantilever slab is found to fluctuate periodically along its length, and a considerable stress concentration is observed in the transverse ribs. The key design parameters of the transverse ribs (depth, width and spacing) influencing the tensile stress amplitude at the cantilever root section are determined through FE parametric analysis.

Dynamic Characteristics Analysis of High Pier Steel Pipe Lattice Support System in Typhoon Region

According to similar criteria, the on-site lattice support on-site in the typhoon area is 62m high and scaled down at 1: 150 to produce an aeroelastic scaled model of the lattice support. Based on the specifications and the characteristics of the wind field in the area where the project is located, a type A landform is used for wind tunnel tests. Through the measured structural dynamic characteristics combined with the help of the finite element analysis software Ansys, the dynamic characteristics of the lattice support under typhoon wind field were studied. The test results showed that under wind load, the lattice support itself is dominated by second-order low-frequency vibrations. The top end of the bracket is excited with a lower first-order frequency. The difference between the first-order and second-order natural frequencies is small. The support is about H / 3 height or more, which is greatly affected by wind load and speed, and is less affected below 30m; at each wind direction angle, the acceleration response of each measurement point of the support generally increases non-linearly with the increase of wind speed. The response of the measuring point shows a quadratic curve relationship with the wind speed. The acceleration of the measuring point gradually decreases from the top to the bottom. At the same wind speed, the closer to the top, the larger the acceleration. The positive change is more than H / 2, and the change period is unstable. Below 20m, the positive and negative acceleration changes relatively uniformly, the closer to the bottom, the smaller the acceleration period; the maximum value of the wind vibration response at each measurement point occurs under the wind angle of 0 ° and 90 °, the wind resistance generated by the box girder cross section has little effect on the support; at a wind angle of 45 °, the response value of the crosswind and windward wind vibration is similar, and the effect of the crosswind cannot be ignored.

Thermal Effects on Box Girder Concrete Bridges

Thermal load, especially vertical temperature gradient, is an important factor that should be considered during the bridge design procedure. In the world, several researches focusing on temperature gradient was made, mostly in USA and China, but only a few analyzed actual temperature gradients measuring at European bridges. In this paper, short overview of temperature loading of bridge structures is described. Then, the temperature measurement of prestressed concrete box girder bridge built by launching method is analyzed. Recorded temperature gradient has been compared with temperature gradients for the concrete box girder cross section recommended by Eurocode design specifications.

Optimizacija ukrućenih tlačnih pojasnica u sandučastom presjeku mosta

Uslijed savijanja, pojasnice celicnih sanducastih presjeka grednih mostova ponasaju se kao tlacni plocasti elementi i zahtijevaju ukrucenja. Koristeci dokaz stabilnosti prema EN 1993-1-5 provedena je parametarska analiza za 6 razlicitih tipova ukrucenja. Dobiveni dijagrami pokazuju racunsko naprezanje otpornosti na izbocivanje za razlicite sirine i debljine ploca, te tip i broj ukrucenja. Nadalje, proveden je optimizacijski postupak kojim se pronalazi najpovoljniji tip i broj rebara ovisno o djelujucoj racunskoj tlacnoj sili. Optimizacijski parametri su minimalna povrsina celika i minimalni broj rebara.

Influence Lines of Bridges with Box-Girder Cross-Section under Torsion and Distortion

Influence lines of torsion and distortion internal forces of large concrete and steel cable-stayed bridges with continuous box-girders. Application for real bridges: (i) steel SNP bridge over river Danube in Bratislava, Slovak Republic, (ii) concrete Harp bridge over pond Jordán near Tábor, Czech Republic.

Numerical Analysis of Shear-Off Failure of Keyed Epoxied Joints in Precast Concrete Segmental Bridges

© 2016 American Society of Civil Engineers. Precast concrete segmental box girder bridges (PCSBs) are becoming increasingly popular in modern bridge construction. The joints in PCSBs are of critical importance, which largely affects the overall structural behavior of PCSBs. The current practice is to use unreinforced small epoxied keys distributed across the flanges and webs of a box girder cross section forming a joint. In this paper, finite-element analysis was conducted to simulate the shear behavior of unreinforced epoxied joints, which are single keyed and three keyed to represent multikeyed epoxied joints. The concrete damaged plasticity model along with the pseudodamping scheme was incorporated to analyze the key assembly for microcracks in the concrete material and to stabilize the solution, respectively. In numerical analyses, two values of concrete tensile strength were adapted: one using a Eurocode formula and one using the general assumption of tensile strength of concrete as 10%f cm . The epoxy was modeled as linear elastic material because the tensile and shear strength of the epoxy were much higher than those of the concrete. The numerical model was calibrated by full-scale experimental results from literature. Moreover, it was found that the numerical results of the joints, such as ultimate shear load and crack initiation and propagation, agreed well with experimental results. Therefore, the numerical model associated with relevant parameters developed in this study was validated. The numerical model was then used for a parametric study on factors affecting shear behavior of keyed epoxied joints, which are concrete tensile strength, elastic modulus of epoxy, and confining pressure. It has been found that the tensile strength of concrete has a significant effect on the shear capacity of the joint and the displacement at the ultimate load. A linear relationship between the confining pressure and the shear strength of single-keyed epoxied joints was observed. Moreover, the variation in the elastic modulus of epoxy does not affect the ultimate shear strength of the epoxied joints when it is greater than 25% of the elastic modulus of concrete. Finally, an empirical formula published elsewhere for assessing the shear strength of single-keyed epoxied joints was modified, based on the findings of this research, to be an explicit function of the tensile strength of concrete.

NUMERICAL ANALYSIS OF A COMPOSITE STEEL BOX GIRDER BRIDGE IN FIRE

Box girder bridges are becoming more common because of their ease of construction, pleasing appearance, and serviceability. Projects with curved configuration and long spans can especially benefit from these advantages. However, the industry lacks a wide range of research on multi-span steel box girder cross-sections and their response to fire events. This poses a major risk to unprotected steel bridges using a box girder design. This paper will discuss a mathematical approach to determining and classifying different failure modes of weathering steel box girder bridges subject to two fire cases. Due to the rapid increase of temperature in the thin steel members, the strength of the steel deteriorates quickly. Results show that different fire locations can greatly affect the forces that act on the individual members of the structure.

Influence of secondary torsion on curved steel girder bridges with box and I-girder cross-sections

Steel curved girder bridges are largely used today in motorways and railways. They are often composed of thin-walled crosssections, entirely made of steel or with an upper concrete slab. The deck may have I-girders or box cross-sections: in any case curved girders are subjected to twisting moment, associated with bending, even for dead loads. Moreover, in thin-walled sections the influence of non-uniform torsion becomes sizable with respect to Saint Venant torsion, modifying the state of tangential stresses in the section and introducing axial stresses due to warping being prevented. Open sections of I-girder bridges are especially subject to these phenomena and warping can be significant not only for curved bridges but also for eccentrically applied traffic loads in straight ones. In this paper a method for the evaluation of the effects of non-uniform torsion, based on an energetic approach, is proposed; the method is simple and fast, with a reduced computational burden with respect to finite elements. The solution of curved girder bridges is performed by the Hamiltonian Structural Analysis method, which is implemented for straight and curved girders with thin-walled cross-sections. A parametric analysis is proposed for single and multi-span bridges, with variation in type of loads applied, crosssection parameters, geometric curvature of bridge deck and stiffness ratios of the cross-section. The parametric study is presented through dimensionless diagrams of internal forces for the evaluation of the global behaviour of curved girder bridges together with indications on the stress state of the cross-section. The interpretation of the results of the analyses performed can be useful to designers for the conceptual design stages and for optimization of the geometric and mechanical parameters of I-girder and box girder cross-sections.

Estimating extreme temperature differences in steel box girder using long-term measurement data

The extreme temperature differences in flat steel box girder of a cable-stayed bridge were studied. Firstly, by using the long-term measurement data collected by the structural health monitoring system installed on the Runyang Cable-stayed Bridge, the daily variations as well as seasonal ones of measured temperature differences in the box girder cross-section area were summarized. The probability distribution models of temperature differences were further established and the extreme temperature differences were estimated with a return period of 100 years. Finally, the temperature difference models in cross-section area were proposed for bridge thermal design. The results show that horizontal temperature differences in top plate and vertical temperature differences between top plate and bottom plate are considerable. All the positive and negative temperature differences can be described by the weighted sum of two Weibull distributions. The maximum positive and negative horizontal temperature differences in top plate are 10.30 °C and −13.80 °C, respectively. And the maximum positive and negative vertical temperature differences between top plate and bottom plate are 17.30 °C and −3.70 °C, respectively. For bridge thermal design, there are two vertical temperature difference models between top plate and bottom plate, and six horizontal temperature difference models in top plate.

Lightweight Design and Research of Box Girder for Double Girder Bridge Crane

With a design of the box girder of bridge crane for the rectangular right track girder, rectangular side rail girder and two trapezoidal side rail girder, MATLAB optimization tool is carried out to calculate the discrete variable by homing method one by one. Then the discrete variable which is the thickness of the steel plate used in box girder is used to determine the shape of the cross-section of box girder.

Thermal field characteristic analysis of steel box girder based on long-term measurement data

Thermal loads are important factors that affect the serviceability of long-span bridges. In this paper, the distribution characteristics and statistical features of thermal field in flat steel box girder are presented based on long-term field measurement data collected by the structural health monitoring system (SHMS) permanently installed on the Runyang Suspension Bridge (RSB). Firstly, the daily variations as well as seasonal ones of measurement temperature and temperature differences in the box girder cross-section are summarized. Secondly, employing a combined probability distribution model defined by the weighted sum of one Weibull distribution and one normal distribution, the probability density function (PDF) of each temperature difference is formulated. Thirdly, making use of the extreme value analysis, the extreme temperature differences are predicted with a return period of bridge design working life and compared with the expected values in British standard (BS EN 1991-1-5, 2003). Finally, the critical temperature difference models in cross-section are proposed for thermal stresses calculation according to correlation analysis. The results provide a clear understanding of thermal field in flat steel box girder bridges and have reference values for structural design and evaluation.

Transverse Shearing Strain Energy Calculation of Single Cell Box Girder

Both the increasingly-thin walls of box girder cross-sections and the super-loads from trains or track vehicles make the behavior research on diaphragms and side walls become particularly important. According to the deformation of single cell box girder cross-section, the displacement parameters were designed, and the displacement modes of cross-section distortion angles were deduced. The schematic plans of diaphragms and side walls were simulated by rigid frames or plates. Both the shearing strain energy and the shearing stiffness of diaphragms and side walls were deduced on the basis of the principles of mechanics and finite element. The results show that the shearing strain energy increases with the displacement by a power function. And the method calculation results are close to the commercial FE software calculation results, which show that the calculation method of single cell box girder presented in this paper is correct and reliable. The calculation method is simpler than the commercial FE software calculation method. In the calculation method, whether diaphragms and side walls are calculated separately or calculated as some parts of the box girder or the vehicle - bridge system, the calculation precision of diaphragms and side walls remains unchanged.

Space Frame Latice Model for Stress Analysis of Bridge

This article presents a space frame lattice model for the analysis of stress of entire cross-section of bridge. The authors focused on analyzing the relatively weaker position of stress in box-girder section, using as an example the Xintan Bridge over the Qijiang River in Chongqing, China. The Xintan Bridge has a continuous prestressed concrete rigid frame with 75+130+75 m span. They calculated and analyzed the shear stress and principle tensile stress of the box girder cross-section in this bridge, using an innovative layout method of mixed internal and external prestressed tendons. They conclude that the space frame lattice model is accurate for calculating the stress state of a bridge. This model can simulate the process of long-term cracking as well as deflection of large-span pre-stressed concrete girder bridges.

Cellular Automata Approach to Durability Analysis of Concrete Structures in Aggressive Environments

This paper presents a novel approach to the problem of durability analysis and lifetime assessment of concrete structures under the diffusive attack from external aggressive agents. The proposed formulation mainly refers to beams and frames, but it can be easily extended also to other types of structures. The diffusion process is modeled by using cellular automata. The mechanical damage coupled to diffusion is evaluated by introducing suitable material degradation laws. Since the rate of mass diffusion usually depends on the stress state, the interaction between the diffusion process and the mechanical behavior of the damaged structure is also taken into account by a proper modeling of the stochastic effects in the mass transfer. To this aim, the nonlinear structural analyses during time are performed within the framework of the finite element method by means of a deteriorating reinforced concrete beam element. The effectiveness of the proposed methodology in handling complex geometrical and mechanical boundary conditions is demonstrated through some applications. Firstly, a reinforced concrete box girder cross section is considered and the damaging process is described by the corresponding evolution of both bending moment–curvature diagrams and axial force-bending moment resistance domains. Secondly, the durability analysis of a reinforced concrete continuous T-beam is developed. Finally, the proposed approach is applied to the analysis of an existing arch bridge and to the identification of its critical members.