The definition of the spatial variability of the ground motion (SVGM) is a complex and multi-parametric problem. Its effect on the seismic response of cable-stayed bridges is important, yet not ...entirely understood to date. This work examines the effect of the SVGM on the seismic response of cable-stayed bridges by means of the time delay of the ground motion at different supports, the loss of coherency of the seismic waves, and the incidence angle of the seismic waves. The focus herein is the effect of the SVGM on cable-stayed bridges with various configurations in terms of their length and of design parameters such as the pylon shape and the pylon–cable system configuration. The aim of this article is to provide general conclusions that are applicable to a wide range of canonical cable-stayed bridges and to contribute to the ongoing effort to interpret and predict the effect of the SVGM in long structures. This work shows that the effect of the SVGM on the seismic response of cable-stayed bridges varies depending on the pylon shape, height, and section dimensions; on the cable-system configuration; and on the response quantity of interest. Furthermore, the earthquake incidence angle defines whether the SVGM is important to the seismic response of the cable-stayed bridges. It is also confirmed that the SVGM excites vibration modes of the bridges that do not contribute to their seismic response when identical support motion is considered.
Electrocution on poorly designed power pylons is one the most important human-related causes of large bird mortality worldwide. Raptor mortality caused by 22 kV distribution power lines was studied ...in south-west Morocco. We surveyed 323 pylons (53.5 km) and collected 65 carcasses of electrocuted raptors in the period 2016 to 2019. The species most affected by electrocution were Long-legged Buzzard and Bonelli's Eagle (49.23% and 29.23%, respectively). Average electrocution rate was 0.201 carcasses pylon−1. Metal pylons, suspended insulators, devices and vaulted configuration had the highest electrocution events. Substitution or corrective measures should be applied on existing pylons that pose the greatest risk to resident breeding and threatened wintering raptors, such as Bonelli's Eagle and Spanish Imperial Eagle in this area.
Double-skin composite walls (DSCWs) stiffened with perforated ribs (perfobond leiste in German, abbreviated as PBL) has gained popularity in large-scale structures due to their industrial ...construction potential. This study aims to explore the axial compressive behavior of PBL-stiffened DSCWs, considering the post-local buckling effect of the faceplates. Six PBL-stiffened DSCWs underwent an experimental investigation under axial compressive loads to evaluate their failure mode, load-axial behavior, ductility, and local buckling behavior. The study also examined the effect of the spacing of transverse and longitudinal PBLs and the introduction of headed studs on the axial compressive behavior of DSCWs. Results reveal that decreasing the spacing of transverse PBLs enhances the confining effect on the infilled concrete, increasing the axial compressive resistance of DSCWs. The introduction of studs delays local buckling and results in strain-hardening of the faceplates, improving the axial compressive resistance of DSCWs. However, increasing the longitudinal PBL spacing weakens the out-of-plane restraint of the faceplates, decreasing both local buckling load and compressive resistance. Assuming the longitudinal PBLs as out-of-plane continuous elastic supports, the elastic critical local buckling coefficient of PBL-stiffened plates with unilateral restraints was derived using the Ritz method. Based on this, the critical relative stiffness of the PBL can be determined, which helps in identifying the local buckling mode of the PBL-stiffened plates. To estimate the post-local buckling behavior of PBL-stiffened plates with unilateral restraints, an effective area method was proposed. Finally, a formula was proposed to predict the axial compressive resistance of PBL-stiffened DSCWs, considering the post-buckling effect. A suggested design procedure for PBL-stiffened DSCWs was also provided.
•Axial compressive behavior considering local buckling of PBL-stiffened DSCWs is experimentally and theoretically studied.•Buckling coefficient of PBL-stiffened plates with unilateral restraints was derived.•Effective area method was developed to estimate post-buckling strength of PBL-stiffened plates.•Proposed formula accurately predicts axial compressive resistance of PBL-stiffened DSCWs.
The effect of air temperature on the penetration and mixing of a liquid hydrocarbon fuel injected into supersonic airflows was investigated. The supersonic air of Mach 1.8 with a total temperature in ...the range of 373–673 K was supplied to the test section. The liquid fuel was injected into the supersonic airflow by means of an alternating-wedge pylon with a fuel-to-air momentum flux ratio of 15. A laser sheet imaging system using Mie scattering has been used to investigate the instantaneous and ensemble-averaged characteristics of the fuel plume, the fuel/air mixing process, and fuel evaporation. As the air temperature increased, the Mie scattering signal gradually weakened due to fuel-air mixing enhancement and fuel evaporation downstream of the pylon. At an air temperature of 673 K, most of the fuel evaporated before reaching the outlet of the test section (X/d = 703). As the air temperature increased from 373 to 673 K, the total pressure loss without fuel injection decreased from 20.6 to 15.4%. In addition, the total pressure losses due to fuel injection was about 3.5% greater than that without fuel injection. As the air temperature increased, the fuel penetration height decreased. However, at the air temperatures higher than the fuel boiling temperature, the fuel jet/spray penetration heights were almost similar, showing little effect of temperature any further.
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•The effect of air temperature on the penetration and mixing of a liquid fuel in supersonic airflows was investigated.•The Mie scattering technique was used to visualize the mixing structure of liquid fuel in supersonic airflows.•The effect of air temperature increase on the total pressure loss due to the pylon and fuel injection was investigated.
From the beginnings of humanity, natural or unnatural misfortunes such as illnesses, wars, automobile accidents cause loss of body limbs like teeth, arms, legs, etc. The solution found for the ...replacement of these missing limbs is in the use of prostheses. Lower limbs tubes or pylons are prosthetics components that are claimed to support loads during walking and other daily tasks activities. Commonly, prosthetic tubes are manufactured using metal materials such as stainless steel, aluminum and titanium. The mass of these tubes is generally high compared to tubes made of carbon fiber reinforced polymer matrix (CFRP) composite. Therefore, this work has the objective of design, manufacturing and analyzing the feasibility of a new tube concept, made of composite material, which makes use of lattice structure and inner layer. Until the present moment, lower limb prosthesis tubes using lattice structure and ineer layer have never been studied and/or tested to date. It can be stated that the tube of rigid ribs with inner layer and angle of 40° is more efficient than those of 26° and 30°. The proposed design allows a structural weight reduction in high performance prostheses from 120 g to 40 g.
For the exposed steel anchor box cable–pylon anchorage structure, there is a good application prospect in urban bridges of medium and small span due to its good mechanical behavior, easy construction ...and beautiful overall appearance. This paper reveals the stress-transfer mechanism of the exposed steel anchor box cable–pylon anchorage structure through a segmental model test with a scaled-down ratio of 1:2, and focused on the effect of prestress in the pylon. Three calculation modes for the anchorage structure are proposed, and simplified calculation equations of the horizontal load distribution relationship and the vertical shear force of the stud are derived. The effects of various design parameters on the load distribution ratio, the pylon wall tension caused by shrinkage and the vertical shear force of the studs are discussed by using the simplified calculation equation. The research results show that the exposed steel anchor box cable–pylon anchorage structure has good applicability in medium and small span bridges. Prestress can significantly reduce the tensile stress of the pylon wall concrete, and improve its crack resistance. There is no significant difference between the results of the simplified calculation equations and the finite element calculation, and the simplified calculation equations meet the design requirement.
•The stress-transfer of exposed steel anchor box revealed by a segmental model test.•Simplified calculations of horizontal load distribution and vertical shear force.•Prestress reduces the tensile stress of the pylon wall and improves crack resistance.•The design requirements can be satisfied by the simplified calculations.
As an important power facility for transmission corridors, automatic three-dimensional (3D) reconstruction of the pylon plays an important role in the development of smart grid. In this study, a ...novel three-dimensional reconstruction method using airborne LiDAR (Light Detection And Ranging) point cloud is developed and tested. First, a principal component analysis (PCA) algorithm is performed for pylon redirection based on the structural feature of the upper part of a pylon. Then, based on the structural similarity of a pylon, a pylon is divided into three parts that are inverted triangular pyramid lower structures, quadrangular frustum pyramid middle structures, and complex upper or lateral structures. The reconstruction of the inverted triangular pyramid structures and quadrangular frustum pyramid structures is based on prior knowledge and a data-driven strategy, where the 2D alpha shape algorithm is used to obtain contour points and 2D linear fitting is carried out based on the random sample consensus (RANSAC) method. Complex structures’ reconstruction is based on the priori abstract template structure and a data-driven strategy, where the abstract template structure is used to determine the topological relationship among corner points and the image processing method is used to extract corner points of the abstract template structure. The main advantages in the proposed method include: (1) Improving the accuracy of the pylon decomposition method through introducing a new feature to identify segmentation positions; (2) performing the internal structure of quadrangular frustum pyramids reconstruction; (3) establishing the abstract template structure and using image processing methods to improve computational efficiency of pylon reconstruction. Eight types of pylons are tested in this study, and the average error of pylon reconstruction is 0.32 m and the average of computational time is 0.8 s. These results provide evidence that the pylon reconstruction method developed in this study has high accuracy, efficiency, and applicability.
In recent years, with the rapid growth of State Grid digitization, it has become necessary to perform three-dimensional (3D) reconstruction of power elements with high efficiency and precision to ...achieve full coverage when simulating important transmission lines. Limited by the performance of acquisition equipment and the environment, the actual scanned point cloud usually has problems such as noise interference and data loss, presenting a great challenge for 3D reconstruction. This study proposes a model-driven 3D reconstruction method based on Airborne LiDAR point cloud data. Firstly, power pylon redirection is realized based on the Principal Component Analysis (PCA) algorithm. Secondly, the vertical and horizontal distribution characteristics of the power pylon point cloud and the graphical characteristics of the overall two-dimensional (2D) orthographic projection are analyzed to determine segmentation positions and the key segmentation position of the power pylon. The 2D alpha shape algorithm is adopted to obtain the pylon body contour points, and then the pylon feature points are extracted and corrected. Based on feature points, the components of original pylon and model pylon are registered, and the distance between the original point cloud and the model point cloud is calculated at the same time. Finally, the model with the highest matching degree is regarded as the reconstructed model of the pylon. The main advantages of the proposed method include: (1) identifying the key segmentation position according to the graphical characteristics; (2) for some pylons with much missing data, the complete model can be accurately reconstructed. The average RMSE (Root-Mean-Square Error) of all power pylon components in this study was 15.4 cm. The experimental results reveal that the effects of power pylon structure segmentation and reconstruction are satisfactory, which provides method and model support for digital management and security analysis of transmission lines.
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