Analysis of continuous PC box girder bridges with CSWs by using equivalent computational model

In the present paper, based on the three-dimensional finite element analysis for a three-span continuous PC box girder bridge with corrugated steel webs and the corresponding conventional box girder bridge with concrete webs, a comparative study on the shear lag effect under self-weight is carryied out together with the analyslis on the coefficient of the effective flange width. The results show that At the sections in the negative bending moment near the intermediate piers, the shear lag effect in the bridge with corrugated steel webs is more obvious than that in the bridge with concrete webs by 8%; and the corresponding effective flange width coefficient in the bridge with corrugated steel webs is even smaller than 0.9, so the shear lag effect at these sections should be considered in the design of this type of bridges. At the mid-span section of the middle span of a three-span continuous bridge either with corrugated steel webs or concrete webs, the shear lag effect can be omitted since the corresponding effective flange width coefficient there is close to 1.0.

To study the vehicle–bridge interaction (VBI) of highway bridges under seismic excitation, a vehicle–bridge couple analysis method based on Ansys is proposed. The 1/2 vehicle model and space beam element model were established to analyze the VBI response of Lanzhou Xiaoshagou bridge. The self‐excited excitation of the system is represented by road surface irregularity randomness, while the external excitation is represented by an earthquake. The impact of seismic types, seismic direction, seismic intensity, vehicle speed, and road surface irregularity on the bridge vibration under the vehicle–bridge coupling during an earthquake is thoroughly analyzed. The results reveal that the type of earthquake significantly influences the dynamic response of the bridge, showing a minimum difference of 31.4%. The intensity of the earthquake is positively correlated with the dynamic response of the bridge. Longitudinal and vertical earthquakes have a more noticeable effect on the bridge’s vertical vibration compared to lateral earthquakes. The ratio of the bridge response under vertical or longitudinal seismic excitation to the response of lateral earthquakes ranges from 1.50 to 26.61. Vehicle speed, road irregularity grade, and randomness have a negligible impact on the dynamic response of vehicle–bridge interaction under an earthquake, accounting for less than 3%. These findings indicate that the analysis of earthquake‐bridge vibration can simplify the VBI analysis for continuous rigid frame composite box girder bridges with corrugated steel webs under seismic conditions.

During the installation and removal of the support of continuous steel box girder bridge, the internal force of the main girder will change, and the range of internal force change is closely related to the position of the support. However, at present, the position of bridge support is mainly determined by experience, which can not effectively reduce the internal force change of main girder during construction and affect the safety of bridge construction. Based on the matrix displacement method, this paper theoretically analyzes the internal force changes of the main girder with or without support, and puts forward the method to determine the optimal position of the support of the continuous steel box girder bridge. According to the theoretical method, the support position is determined and the finite element model is established. The internal force changes of the key sections of the bridge are calculated by numerical simulation and theoretical analysis respectively. By comparing the calculation results and combining the bending moment diagram of the main girder, it can be concluded that the calculation error of the two methods is less than 6%, which shows that the theoretical method has high accuracy and engineering applicability; The optimal position of the support determined by theoretical method is located near the transition point of positive and negative bending moments. Based on this rule, the position of the support can be preliminarily judged in engineering to improve the efficiency and safety of construction.

Corrugated steel webs have crinkled effect without capacity bearing the axial force and bending moment, which leads to its effective elastic modulus is smaller than that of material. This paper deduced the computational formula of effective elastic modulus corrugated steel webs, and puts forward the calculation method for corrugated steel webs of composite beams. Combined with a continuous composite box-girder bridge with corrugated steel webs, the finite element model is built to analyze the bending performance such as normal tensile stress, normal compressive stress and crack resistance.

The distribution of the temperature gradient and temperature change of the pre-stressed concrete box girder are extremely complicated because of the multiplex environment. Temperature load has attached great importance in the field of engineering, and it has a great influence on the bridge’s structure, especially the box structure. The engineering background of this paper is a typical three-dimensional pre-stressed concrete continuous box girder bridge with variable cross section, comprising five spans in one continuous unit. Experiment on it and research the change rules of the temperature distribution, as well as the influence of the structure’s internal force resulted by temperature. Finite element software-Midas/FEA is used to model and calculate the bridge in order to analyze the temperature influence on structure’s stress in contrast to the measured data from the experiments

With the development of algorithms for autonomous decision-making in the field of structural engineering, the design of precast concrete segment (PCS) box girder bridges faces new challenges. This paper proposes using a multi-objective optimization method based on genetic algorithms for the rapid design of PCS box girder bridges with small and medium spans. By considering 20 design parameters such as the physical dimensions of the box girder cross-section, material properties, and prestressing parameters, the paper formulates and quantifies three objective functions: cost, safety, and structural performance. The multi-objective optimization was conducted using four optimization algorithms (NSGA-II, NSGA-III, GDE3, and PSO). An optimization evaluation index (φ[F(x)]) was established and weights were assigned to different optimization objectives. A specific design case based on the general diagram of a 3 × 25 m-long continuous PCS box girder bridge was carried out. The results indicate that genetic algorithms performed exceptionally well on this problem, with the NSGA-III algorithm achieving the best φ[F(x)] value of 0.2789 among all algorithms. A performance analysis was conducted on various optimization models using box plots and sensitivity studies. Scatter plots and surface plots of the Pareto front of the optimized solutions were generated, and corresponding cross-sectional design drawings were created based on the two proposed solutions. Compared with the general graph, the design cases provided by the NSGA-III algorithm model have a change rate of 8.03%, −0.29%, and 75.49% in the three optimization objectives, respectively, indicating a significant improvement effect. The research content of this paper provides a reasonable direction for future studies on intelligent bridge design methodologies.

Based on an accident of bursting and crack of bottom slab of one continuous box girder bridge during construction, the damage mechanism was analyzed using spatial finite element method. Parameter analysis on main factors influencing the vertical stress state of bottom slab of cantilever casting prestressed box girder segment closure and nearby segment was carried out. Then stability performance of box girder segments with cracked bottom slab were studied. It is concluded that radial force of bending prestressing strand and additional radial force with its deviation from the design position were the main reasons for bursting cracks in box girder bottom slabs, and the final failure form of bottom slabs was unstable destruction.

Comparison of dynamic response of isolated and non-isolated continuous girder bridges subjected to near-fault ground motions

Box girders are commonly utilized in bridge engineering because of their economical and visually appealing form. Due to recent advancements in the design sector. However, safety in the economy is the fundamental demand of the current generation, therefore, it is vital to pick an optimal design. Prestrained concrete is used for large-span bridges. Standard heuristic optimization is frequently used to do structural optimization because of how complex structural concerns remain. However, traditional heuristic optimization still takes a significant amount of time. Particle Swarm trained Hierarchically Stepped Adversarial Networks (PS-HSAN) are presented as an alternative approach to speeding up the optimization of complex problems, and their use reduces the cost of computation for optimization. To find the best design for “a three-span continuous box-girder pedestrian bridge, this research” will apply both classical heuristic optimization and PS-HSAN. This will include analyzing and assessing a variety of crime types and sample sizes. Particle swarm optimization is shown to be as effective as conventional heuristic optimization but with significant time savings. Therefore, using a PS-HSAN in structural design challenges provides an original method for handling certain structural difficulties that need a great degree of computing power while simplifying the solution of other problems.

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.

The construction of a modern long span rigid frame box girder bridge gives impetus to the development of structural analysis design theory and construction technology. Moreover, it makes construction monitoring of the rigid frame box bridge a significant research subject. Construction monitoring of the rigid frame box bridge signifies regulating the structure’s internal force and alignment in the construction process and completion state, and thence satisfies the designed expectation. Based on the construction monitoring of Liang-Ji Canal Bridge project, the construction process and the designed completion state have been simulated and analyzed at a certain precision level [1]. A plane bar finite element computational model is established, and the alignment and internal force of the bridge in each construction stage are analyzed. Then the simulation analysis of construction process is derived according to its construction characteristics [2]. Through systematical research on the form work elevation and the stress monitoring of the cantilevers during the cast-in-situ construction, the factors which influence deflection and stress are analyzed. The elevation is predicated by the Kalman's filter estimation, the modified grey model and the combination of these two methods. The stress monitoring error and corresponding reasons are analyzed. The measured results show that the combination of the two approaches can improve prediction accuracy. The presented analysis, processing and control methods accumulate many experiences for the design and construction of the long span box girder rigid frame bridge.

To improve the crack-resisting behavior of normal-strength concrete (NC) bridge deck and to reduce the deadweight of conventional steel-concrete composite girders, a new steel-ultrahigh performance concrete (UHPC) continuous composite box girder was proposed. Aiming to reveal the static behavior of the proposed structure, including the load-deflection response, the strain distribution, the crack development, the moment redistribution and the failure mode, a comparative experimental study was conducted on two types of the composite girder, namely a steel-UHPC continuous composite girder (SUCG) and a prestressed steel-concrete continuous composite girder (SCCG). The test results indicated that the ultimate loading capacity of the SUCG was 20.4% higher than that of SCCG; the nominal cracking strength of the SUCG was 22.9 MPa, and its corresponding cracking moment was 2.1 times higher than the conventional one; the crack development mode of UHPC slab were significantly different from the SCCG, the cracks appeared in UHPC slab dominated by microcracks with smaller length were numerous and intensive. It is also shown that the SUCG has smaller degree of moment redistribution. Thus, the current study verified the SUCG could be one of effective solutions for long-span continuous composite girder bridges.

This paper proposes different optimization schemes for enhancing the performance of conventional continuous composite girder bridges with corrugated steel webs. In particular, for the positive moment region, the substitution of a ribbed steel plate for the reinforced concrete bottom flange is proposed for optimizing such bridges. Three-dimensional finite-element analysis was used to preliminarily validate this optimization scheme based on the background project, Dongbaohe Xinan Grand Bridge. An experimental study revealed that the optimization scheme can afford advantages, such as reduced self-weight, avoidance of cracking in the bottom flange, and convenient construction. If the steel plate with proper thickness is used, higher flexural stiffness and load capacity can be achieved as additional advantages due to the enhanced steel ratio of the cross section. For the negative moment region of the bridge, the optimization scheme was implemented in two parts identified as Optimization Schemes I and II. In Scheme I, corrugated steel plate–concrete composite webs were used, whereas a steel–concrete composite bottom flange was further adopted in Scheme II. Compared to the conventional scheme, both Optimization Schemes I and II significantly reduced the shear stress in the corrugated steel web and at the steel–concrete interface due to the lined concrete in the web. Thus, it can be deduced that the applied load corresponding to the yield of the corrugated steel web will be enhanced; namely, the shear capacity will be enhanced. Because shear connection failure was prevented in both optimization schemes, there were remarkable improvements of the load capacity and ductility of the girder. The confining effect of the lined concrete decreased the prestress lead-in ratio, but not significantly. In addition, Optimization Scheme II afforded much greater construction convenience compared to both Optimization Scheme I and the conventional scheme.

This paper aims to evaluate the impact interaction between the abutment and the girder subjected to nonuniform seismic excitation. An impact model based on tests is presented by taking material properties of the backfill of the abutment into consideration. The conditional simulation is performed to investigate the spatial variation of earthquake ground motions. A two-span continuous steel box girder bridge is taken as the example to analyze and assess the pounding interaction between the abutment and the girder. The detailed nonlinear finite element (FE) model is established and the steel girder and the reinforced concrete piers are modeled by nonlinear fiber elements. The pounding element of the abutment is simulated by using a trilinear compression gap element. The elastic-perfectly plastic element is used to model the nonlinear rubber bearings. The comparisons of the pounding forces, the shear forces of the nonlinear bearings, the moments of reinforced concrete piers, and the axial pounding stresses of the steel girder are studied. The made observations indicate that the nonuniform excitation for multisupport bridge is imperative in the analysis and evaluation of the pounding effects of the bridges.

<p>In order to promote the application of steel-concrete composite structure in mountainous areas in China, a conceptual design for a PC continuous rigid frame box-girder bridge with corrugated steel webs and main span of 300 m was performed in the present paper. The combined corrugated steel web was proposed to increase the compressive area and improve the stability performance; thus, the self-weight of the composite box-girder bridge is significantly reduced. Flexural capacity of the whole section had been calculated with a single-beam model for the ultimate limit state (ULS). For the service limit state (SLS) design, the calculation for the composite box-girder bridge was conducted with the spatial grid model (SGM), from which 27 complete checking stresses in three layers (i.e. outside, inside and middle planes) of concrete plates and steel webs in every cross-section could be obtained. The stress history under construction stage was incorporated into the results obtained by SGM. Moreover, the stress states and stability performance for the composite box-girder bridge constructed were evaluated. The present investigation can provide references for the design and construction of the composite box-girder bridge with corrugated steel webs for long spans.</p>