Mountainous freeways with high bridge and tunnel ratios are a new type of road that rarely contain many special road sections formed by various structures. The crash characteristics of the road are ...still unclear, but it also provides conditions for studying how various road environments affect traffic. In view of the various structures and differences in the driving environments, a scenario-based discretization method for such a road was established. The traffic-influence areas of elementary and composite structures were proposed and defined. Actual data were analyzed to investigate the crash patterns in an entire freeway and in each special section through statistical and comparative research. The results demonstrate the applicability and validity of this method. The crash rates were found to be the highest in interchange and service areas, lower in ordinary sections, and the lowest in tunnels, being mostly attributed to collisions with fixtures. The crash severity on bridges and bridge groups was significantly higher than that on the other types of road sections, being mostly attributed to single-vehicle crashes. The annual average daily traffic and driving adaptability were found to be related to crashes. The findings shed some light on the road design and traffic management implications for strengthening the traffic safety of mountainous freeways.
•Propose a framework for typhoon-induced non-stationary buffeting analysis of a bridge.•Model non-stationary wind as time-varying mean wind plus evolutionary random process.•Consider effects of ...time-dependent force coefficients and flutter derivatives.•Use pseudo excitation method to compute evolutionary response spectra of a bridge.•It is necessary to consider non-stationary effects on bridge buffeting response.
This paper presents a framework for predicting typhoon-induced non-stationary buffeting response of long-span cable-supported bridges located in a complex terrain. First, a non-stationary typhoon wind model is proposed based on observations from measured typhoon wind data. The wind model includes mainly time-varying mean wind speed, mean wind speed profile and evolutionary power spectral density (EPSD) function. Typhoon-induced wind loading on a bridge deck is then represented by time-varying mean wind forces, non-stationary buffeting forces associated with time-dependent aerodynamic coefficients and self-excited forces characterized by time-dependent aerodynamic derivatives. A nonlinear static analysis is performed to determine time-varying mean wind response, whereas the pseudo excitation method is employed to compute the EPSD-expressed non-stationary buffeting response of a long-span cable-supported bridge. The proposed framework is finally applied to predict non-stationary buffeting responses of a long-span cable-stayed bridge located in a complex terrain during a strong typhoon as a case study. The case study demonstrates how to apply the proposed framework and the results show that the proposed framework is feasible and necessary.
Thermal energy exchange induces non-uniform temperature distribution on the concrete bridge structures, leading to variation of static and dynamic properties of structural systems. The finite element ...method can facilitate thermal simulation and predict the structural temperature distribution based on heat flow theories. Previous studies mainly focused on the daytime with sunny weather, and the effects of solar shadow distribution were not fully considered or even ignored. In this paper, a systematic all-weather thermal simulation method was proposed to investigate the temperature distributions of concrete maglev bridges. The solar shadow distribution on the bridge surface could be accurately simulated to determine the solar radiation-imposed range. A meteorological station and some thermocouples were installed on a real concrete maglev bridge to obtain the real-time structural temperatures and environmental conditions. Its temperature distribution is also simulated using the proposed method within the 27 monitoring days in Summer. Results show that the simulated structural temperature matches well with the measured results under various weather conditions, except that of the east structural surface. Moreover, the simulation method acquired a higher accuracy under overcast or rainy weather due to weaker solar radiation effects. Both the numerical results and experimental records illustrated that direct solar radiation dominates the thermal energy exchange under sunny or cloudy conditions. The proposed methodology for temperature field simulation is oriented by all-weather prediction of structural temperature, which is reliable for concrete bridge structures with the help of accurate measurement of real-time solar radiation.
Since their discovery, spicules have attracted increased attention as energy/mass bridges between the dense and dynamic photosphere and the tenuous hot solar corona. Mechanical energy of photospheric ...random and coherent motions can be guided by magnetic field lines, spanning from the interior to the upper parts of the solar atmosphere, in the form of waves and oscillations. Since spicules are one of the most pronounced features of the chromosphere, the energy transport they participate in can be traced by the observations of their oscillatory motions. Oscillations in spicules have been observed for a long time. However the recent high-resolution and high-cadence space and ground based facilities with superb spatial, temporal and spectral capacities brought new aspects in the research of spicule dynamics. Here we review the progress made in imaging and spectroscopic observations of waves and oscillations in spicules. The observations are accompanied by a discussion on theoretical modelling and interpretations of these oscillations. Finally, we embark on the recent developments made on the presence and role of Alfvén and kink waves in spicules. We also address the extensive debate made on the Alfvén versus kink waves in the context of the explanation of the observed transverse oscillations of spicule axes.
•Large structure is decomposed and condensed into substructure using CMS.•Damage detection is first performed in substructure level and then in element level.•The computational efforts are decreased ...while the identifiability is increased.•Responses of suspicious substructure are reconstructed using Kalman filter.•Both numerical and experimental studies are conducted on a complex bridge testbed.
Damage identification of a large and complex bridge structure often requires an enormous computational effort to solve an ill-posed inverse problem with a large number of unknowns. Moreover, the predefined sensors usually cannot sufficiently cover all the potential damage regions for a large bridge structure, which will introduce additional difficulties in damage identification. To deal with these challenges, a multi-level damage identification method with response reconstruction that uses a divide-and-conquer approach is proposed. An entire bridge structure is firstly decomposed into several manageable substructures and condensed as super elements using component mode synthesis (CMS); damage identification is then carried out at the substructure level to locate potentially damaged (target) substructures. The second level is at the element (member) level to further localize and quantify damage for the target substructures. To this end, a Kalman filter-based response reconstruction is performed on the target substructure for more accurate damage quantification. To examine the feasibility and effectiveness of the proposed method, a combined numerical and experimental investigation is performed on a laboratory testbed model of the Tsing Ma suspension bridge (TMB). Numerical studies are firstly conducted to inform optimal sensor placement for response reconstruction and multi-level damage identification. The sensor system is then installed on the TMB testbed model, and the proposed multi-level damage identification method is validated through comparison with experimental results. The numerical and experimental results demonstrate that the proposed multi-level damage identification method is capable of identifying damage in a large bridge structure.
Railroad vehicle and bridge coupled lateral vibration problems are traditionally solved through detailed nonlinear models in time domain using limited samples to represent rail irregularity. Ideally, ...a random vibration and reliability based approach should be implemented because of the random nature of the excitation process. In this study, vehicle–bridge coupled dynamic equation was derived using the principle of virtual work utilizing a linearized wheel–rail contact equation. This simplification enables the calculation of the system random lateral responses through the pseudo-excitation method. By applying rail irregularity as random excitations to the system, this study utilized an explicit linearization method to avoid iterative solution at each time step of the integration. The results from the linearized method were validated through comparison with results obtained from Monte-Carlo simulations. By applying the linearized approach to probabilistic assessment of the vehicle–bridge system reliability, it was shown that system probability of exceedance of admissible limits increases with train speed and reduces with increased bridge self-weight. It is concluded that the proposed approach provides a viable efficient alternative to investigate the random dynamic characteristics of vehicle–bridge system especially in the lateral direction, which is dominated by the random rail irregularities.
► Influence of seismic design of multispan bridge classes on performance. ► Assessment of failure probability and comparison using analytical fragility curves. ► Confidence bounds to characterize ...uncertainty about median fragility curves. ► Significant improvement in performance due to seismic design and detailing. ► Good agreement with median fragilities reported in HAZUS.
Vulnerability estimation as well as quantitative and qualitative assessment of the seismic risk to highway bridges is crucial in obtaining reliable estimates of the resilience of highway transportation systems. Although previous studies have evaluated the seismic response and fragility of various bridge classes common to the central and southeastern United States, there is very little research that explores the differences in performance of bridge classes built with and without seismic detailing. This paper addresses this gap by investigating the influence of seismic detailing of four multispan bridge classes on the seismic performance, as well as the failure probability through the development and comparison of fragility curves. The primary differences between seismically and non-seismically designed bridges are the column reinforcement details and bridge bearings. Component and system fragility curves are developed to provide insight into the difference in performance of non-seismically and seismically designed bridges and are compared with those currently found in HAZUS-MH. Confidence bounds are finally developed to characterize the uncertainty about the proposed median fragility curves for the bridge classes. Bridge classes with seismic provisions incorporated in their design tend to have reduced confidence bandwidth at higher damage states. Significant improvement in performance is seen in all bridge classes considered in this study when seismic design and details are used.
With the change of the public's aesthetic concept, people's requirements for the landscape and art of bridges are constantly improving. The connotation of bridge has developed from the original ...traffic architecture to the carrier of human landscape and historical culture. Therefore, integrating the concept of landscape art into bridge design is an important development direction in the field of bridge design. This paper expounds the connotation of landscape art in bridge design, and enumerates the typical application of the landscape art concept in bridge design. On this basis, this paper analyses the advantages of computer two-dimensional image technology for bridge landscape design, and discusses several aspects that should be improved in future bridge landscape design, which provides new thinking and reference for modern bridge design.
Particle flow code 2D (PFC2D) was adopted to simulate the shear behavior of rocklike material samples containing planar non-persistent joints. Direct shear loading was conducted to investigate the ...effect of joint separation on the failure behavior of rock bridges. Initially calibration of PFC was undertaken with respect to the data obtained from experimental laboratory tests to ensure the conformity of the simulated numerical models response. Furthermore, validation of the simulated models were cross checked with the results of direct shear tests performed on non-persistent jointed physical models. Through numerical direct shear tests, the failure process was visually observed, and the failure patterns were found reasonably similar to the experimentally observed trends. The discrete element simulations demonstrated that the macro-scale shear zone resulted from the progressive failure of the tension-induced micro-cracks. The failure pattern was mostly influenced by joint separation, while the shear strength was linked to the failure pattern and failure mechanism. Furthermore, it was observed that the failure zone is relatively narrow and has a symmetrical pattern when rock bridges occupy a low percentage of the total shear surface. This may be due to the high stress interactions between the subsequent joints separated by a rock bridge. In contrast, when rock bridges are occupying sufficient area prohibiting the stress interactions to occur then the rupture of surface is more complex and turns into a shear zone. This zone was observed to be relatively thick with an unsymmetrical pattern. The shear strength of rock bridges is reduced by increasing the joint length as a result of increasing both the stress concentration at tip of the joints and the stress interaction between the joints.
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