Fatigue strengthening of tubular X joint using un-bonded CFRP laminates

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Finite element modeling of the influence of residual weld stresses on buckling

One of the determining factors in the design of steel-tied arch bridges is the out-of-plane buckling behavior. While considerable research, focusing on the determination of the geometrical imperfections, using non-destructive testing as well as analytical calculation methods, is available, the influence of residual welding stresses has not been studied in depth. It is assumed that these stresses would have only limited influence on buckling. Still, this paper claims the residual stresses, which are present in the arches, can be of limited importance, since they do influence the out-of-plane shape of the arch. Firstly, a fundamental approach is followed by developing a three-dimensional finite element model of the influence of the welding parameters and weld sequence. In addition, the resulting residual welding stresses are used for an elastic-plastic calculation of an entire arch. This allows for calculating the buckling behavior of arches as realistically as possible

Seismic behavior of triple tunnel complex in soft soil subjected to transverse shaking

Combining multiple tunnels into a single tunnel complex while keeping the surrounding area compact is a complicated procedure. The condition becomes more complex when soft soil is present and the area is prone to seismic activity. Seismic vibrations produce sudden ground shaking, which causes a sharp decrease in the shear strength and bearing capacity of the soil. This results in larger ground displacements and deformation of structures located at the surface and within the soil mass. The deformations are more pronounced at shallower depths and near the ground surface. Tunnels located in that area are also affected and can undergo excessive distortions and uplift. The condition becomes worse if the tunnel area is larger, and, thus, the respective tunnel complex needs to be properly evaluated. In this research, a novel triple tunnel complex formed by combining three closely spaced tunnels is numerically analyzed using Plaxis 2D software under variable dynamic loadings. The effect of variations in lining thickness, the inner supporting structure, embedment depth on the produced ground displacements, tunnel deformations, resisting bending moments, and the developed thrusts are studied in detail. The triple tunnel complex is also compared with the rectangular and equivalent horizontal twin tunnel complexes in terms of generated thrusts and resisted seismic-induced bending moments. From the results, it is concluded that increased thickness of the lining, inner structure, and greater embedment depth results in decreased ground displacements, tunnel deformations, and increased resistance to seismic-induced bending moments. The comparison of shapes revealed that the triple tunnel complex has better resistance against moments with the least amount of thrust and surface heave produced

Integrating spatial and temporal approaches for explaining bicycle crashes in high-risk areas in Antwerp (Belgium)

The majority of bicycle crash studies aim at determining risk factors and estimating crash risks by employing statistics. Accordingly, the goal of this paper is to evaluate bicycle-motor vehicle crashes by using spatial and temporal approaches to statistical data. The spatial approach (a weighted kernel density estimation approach) preliminarily estimates crash risks at the macro level, thereby avoiding the expensive work of collecting traffic counts; meanwhile, the temporal approach (negative binomial regression approach) focuses on crash data that occurred on urban arterials and includes traffic exposure at the micro level. The crash risk and risk factors of arterial roads associated with bicycle facilities and road environments were assessed using a database built from field surveys and five government agencies. This study analysed 4120 geocoded bicycle crashes in the city of Antwerp (CA, Belgium). The data sets covered five years (2014 to 2018), including all bicycle-motorized vehicle (BMV) crashes from police reports. Urban arterials were highlighted as high-risk areas through the spatial approach. This was as expected given that, due to heavy traffic and limited road space, bicycle facilities on arterial roads face many design problems. Through spatial and temporal approaches, the environmental characteristics of bicycle crashes on arterial roads were analysed at the micro level. Finally, this paper provides an insight that can be used by both the geography and transport fields to improve cycling safety on urban arterial roads