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Dynamic Response Research of Continuous Curved Concrete Bridges under Moving Vehicles

Author: HuangXinYi
Tutor: ShengHongFei
School: Harbin Institute of Technology
Course: Bridge and Tunnel Engineering
Keywords: continuous concrete curved bridges dynamic analysis model coupled vehicle-bridge vibration braking force impact factors
CLC: U441.3
Type: PhD thesis
Year: 2008
Downloads: 679
Quote: 10
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With the rapid development of highway construction and urban road transportation in recent years, curved beam bridges are widely used in highway viaducts, approach of long span bridges and large interchanges, most of which are concrete curved bridges. Though great progress has been made in static analysis theory of concrete curved bridges in the last years, less theoretical and experimental research was conducted on the dynamic performances. These lead to an insufficient understanding and no specific criteria are available on dynamic design on concrete curved bridges. The impact factor assessment method of curved bridge under moving vehicles mostly adopts the usages of straight beam bridges, but not enough argumentations can demonstrate the reasonability. Thus, the dynamic performance studies of concrete curved bridges have important significance on the perfection of design theories, regulation of impact factor assessment method, maintenance management and service life evaluation for concrete curved bridges. Box girder beams are commonly used in curved bridges to resist the extant coupled bending-torsional effect. This thesis focuses on the dynamic characteristics and dynamic responses due to vehicles for curved box girder bridges. The main contents are as follows:First, based on the shear force flexible grillage method, the triple beam model suitable for the dynamic analysis of curved bridges, in which the effects of warping stiffness and moment of inertia are both considered, is presented by improving the existing model. The model is validated by both ambient excitation test and solid model analysis. Then, based on the commercial program ANSYS, 3D beam element, mass element and spring-damper element are adopt together in building the 12 DOFs spatial vehicle model and the bridge model. A simplified numerical method is put forward for solving the coupled vehicle-bridge vibration problems, of which the effect of centrifugal force, random road roughness and its velocity term are considered comprehensively. The method is validated by comparison between the numerical simulation and dynamic loading test of a preselected bridge under vehicle at uniform velocity.Second, by using the former presented model and numerical method, parametric studies are conducted on dynamic responses of curved bridges under a single vehicle, in which road roughness, curvature of radius, vehicle travelling eccentricities, rigidity and damping of the tyres, damping ratio of the bridge, number of bridge spans, bearing types and the longitudinal gradient of the bridge are included. Both the dynamic responses and dynamic amplification factors are calculated and compared. Then, the influence of lateral multi-lane loading, longitudinal multi-vehicle loading, space headway and velocity are also investigated for bridges under platoon. The parametric analysis results can provide good references for the selection, analysis of engineering examples and the stipulation of impact factor formulae in the later studies.Third, the formulae of load transferring caused by accelerating and decelerating resistance are deduced by d’Alembert theorem and also the formulae of braking force distribution. These forces are all considered in the dynamic response analysis of bridges due to vehicle at various velocities. Based on the former presented method and taken varying time steps and velocities into account, the effects of braking rise time and braking position in braking process, as well as the effects of initial velocity and acceleration in the acceleration process are investigated on the bridge dynamic responses and impact effects. The results indicate that vehicle travelling at various speeds has great influence on bridge dynamic responses.Last, an extensive investigation is conducted to determine the effects of key parameters on the impact factors of continuous concrete curved bridges. Studies on correlation among impact factors and various important parameters are conducted to determine the most important ones. Based on the results, it is found that the impact factors of internal forces at various position, deflection and support reaction have great significance. The upper-bound envelop expressions of the impact factors for maximum bending moment, torsional moment, shear force, de?ection and support reaction were deduced and given in different road roughness classes as the function of central angle and the fundamental bending vibration frequency, respectively. It is found that the impact factors of curved bridges descend as the value of central angle and the fundamental bending vibration frequency ascend, which is contrary to the relationship between impact factor and the fundamental bending vibration frequency of straight beam bridges presented in the current bridge design standard (JTG D60-2004). Therefore, it may be relative unsafe for the medium to large span concrete curved bridges whose fundamental bending vibration frequencies are low while impact factors are calculated according to the current bridge design standard (JTG D60-2004). The formulae presented in the thesis can offer references for dynamic design and maintenance of concrete curved bridges.

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CLC: > Transportation > Road transport > Bridges and Culverts > Structural principles, structural mechanics > Bridge vibration and damping device
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