Current Issue : July-September Volume : 2023 Issue Number : 3 Articles : 5 Articles
The U-shaped steel support has good surface protection and is one of the main supporting forms of the roadway under rock bursts. However, in the supporting process of roadways under rock burst, there are poor mechanical properties of lap joints, resulting in a serious decline in the anti-impact performance of U-shaped steel supports. Using a combination of laboratory experiments and theoretical analysis, we study the sliding mechanism of the U-shaped steel bracket’s overlap section bearing and find the key factors affecting the sliding performance of the overlap section. The characteristics of deformation and failure of U-shaped steel supports under impact loads are analyzed by numerical calculations. An improved method for optimizing the sliding performance of the lap section is proposed to provide theoretical support for the design of stable and constant-resistance energy-absorbing Oshed supports. The research results show that the frictional properties between the contact surfaces of the overlapped sections, especially the frictional properties between the contact surfaces of the clamp and the U-shaped steel, determine the sliding characteristics of the U-shaped steel overlapped sections, which are the key factors affecting the bearing capacity of the support. The single-point maximum bearing capacity of the U-shaped steel bracket under the uniformly distributed impact load is basically close to the maximum bearing capacity of the U-shaped steel bracket under the concentrated impact load. When the U-shaped steel bracket is uniformly loaded, its bearing capacity can be increased several times. When a gasket is added between the U-section steel and the clamping bolt in the lap section, the bearing capacity changes smoothly during the sliding process, which greatly improves the friction performance between the contact surfaces, and can greatly improve the overall bearing capacity, energy absorption, and anti-impact performance of the support structure. Based on this, a stable and constant energy-absorption O-type shed structure for the impacted underground roadway in Laohutai Mine was proposed. The field application proved that improving the sliding performance at the joint of the U-shaped steel support can effectively control the deformation of the roadway under the impact load....
With the development of national railways and railways as one of the important channels for heavy-haul transportation, the construction of heavy-haul railways must be a rapid development, which makes it inevitable that the heavy-duty situation of smalldistance interchange tunnels will appear. Nanomaterials refer to materials that have at least one dimension in the threedimensional space in the nanoscale range (1nm100 nm) or are composed of them as basic units. Ferroelectric domain polarization refers to the existence of electric domains in ferroelectrics, electric domains refer to small regions with the same spontaneous polarization direction, and the boundaries between electric domains and electric domains are called domain walls. It is also urgent to study the dynamic structure of the surrounding rocks of heavy-duty railways. This article aims to study the use of nanomaterial and ferroelectric domain technology to improve the overall strength, wear resistance, toughness, and other properties of steel to ensure the safety of the surrounding rock dynamic structure of the heavy-duty railway in the small clearance intersecting tunnel. Moreover, on this basis, this article proposes the method of spraying steel with nanomaterials and the use of ferroelectric domain polarization technology. The strength and wear resistance of steel can be improved under different nanomaterial content and the degree of ferroelectric domain polarization. Sustainability and toughness have been improved, respectively. After the wear resistance experiment and analysis, the experimental results of this article show that the impact resistance of the steel increased by 18.75%. When 0.012% of CeO2 is added, the impact toughness of the steel is increased to the maximum of 3.4 J, an increase of 16.31%, and a 37% increase in wear resistance. Under the premise of ensuring the demand for heavy-duty transportation, the safety performance and sustainability of transportation are greatly improved....
In this work, cyclic-load tests on reduced-scale corroded reinforced-concrete hollow crosssection bridge piers have been experimentally performed and compared to the results of similar non-corroded piers. Piers were aged by using an imposed electric current and sodium chloride water solution before performing a mechanical cyclic-load test. The corrosion process has been detected with Non-Destructive Evaluation techniques by means of SonReb method (to check concrete degradation) and by measuring corrosion potential (to check steel degradation). The crack pattern was recorded by dedicated cameras, and an LVDT system was set up to monitor the cyclic-load test. Experimental results focused on degradation monitoring and mechanical performance under cyclic loads. During the cyclic-load mechanical test, the first cracks on the piers surface occurred diagonally, inclined at about 45◦. This is the consequence of the failure mode change from ductile failure, as expected for slender designed piers, to brittle shear failure. The flexural failure occurred in the case of non-corroded piers. Presented tests can provide a useful contribution of experimental data to analyse the behaviour of corroded reinforced concrete hollow bridge piers, scarcely tested. In particular, the cyclic response can be a useful reference for the proposition/validation of nonlinear capacity models for the evaluation of the seismic capacity of corroded bridge piers....
Digital twins (DTs) have a great potential for bridge operation and maintenance. Geometric digital twins (gDTs) are the key component of DTs. At present, a growing number of researchers are using high-precision 3D laser point clouds to generate gDTs. However, for large bridges, such as arch, cable-stayed, and suspension bridges, comprehensive point-cloud collection stations are difficult to set up due to their large span, narrow site, and limited field of vision. Consequently, the complete point clouds of these bridges cannot be easily obtained. Thus, knowing how to process absence point clouds and generate gDTs is an urgent problem. This study proposes a semiautomatic method of extracting geometric information of a bridge’s components in the absence of point clouds. First, an algorithm based on the combination of the iterative polynomial fitting curve and sliding window is developed to extract the arch ring accurately. Second, an improved random sample consensus (RANSAC) algorithm based on distribution density is adopted to extract the cross sections of the arch bridge components, except the arch ring. For cross sections that lack point clouds, a translation strategy is used to supplement the unknown line segment. Finally, for the T-beam, a model alignment method is proposed to best match the characteristic intersections extracted by the improved RANSAC algorithm and the points corresponding to the design model. The quality of the generated models is gauged using a point cloud deviation chromatogram. In addition, the stressed component piers are compared with its design parameters to verify the accuracy of the proposed method. Results show that our method can efficiently and accurately extract geometric information and generate gDT for the bridge....
In view of the poor accuracy and unsatisfactory effect of shrinkage compensation for concrete-filled steel tubular structures of large cross-sea bridge (CSTS-LCSB), a new shrinkage compensation technology for CSTS-LCSB is proposed. The shrinkage mechanism of CSTS-LCSB is analyzed, including plastic shrinkage, dry shrinkage, autogenous shrinkage, and carbonation shrinkage. The proportion of dry shrinkage and autogenous shrinkage in ordinary concrete and high-strength concrete is determined. The CSTS-LCSB has different shrinkage forms in different environments, and the shrinkage strain state of CSTS-LCSB in different environments is calculated according to the difference. The shrinkage area of the concrete structure is determined, and the expansion agent is used to compensate for the shrinkage area of CSTS-LCSB. The experimental results show that the proposed compensation technology has a good effect on shrinkage compensation and has certain feasibility....
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