Current Issue : July - September Volume : 2020 Issue Number : 3 Articles : 5 Articles
The purpose of this paper was to systematically investigate the influence of acid rain environments on the seismic behaviour of a\nreinforced concrete (RC) column. Six RC column specimens with shear span ratios of 2.84 were tested under low cyclic reversed\nloads after being subjected to accelerated corrosion tests in an artificial climate. The corrosion level and stirrup ratio were used as\nthe control variables. The corrosion ratios of the longitudinal rebars ranged from 0 to 13.17%, and the corrosion ratios of the\nstirrups varied from 0 to 6.75%. The seismic behaviours of the column specimens were analysed with respect to visual damage,\nfailure mode, hysteresis behaviour, load-carrying capacity, deformation capacity, stiffness degradation, and energy dissipation\nbehaviour. The test results showed that the appearance characteristics of the six column specimens exhibited varying degrees of\nvisual damage as a result of the simulated acid rain exposure. All six specimens were dominated by similar flexural-shear failures\nunder low cyclic reversed loads, regardless of the distinctions in the corrosion levels or stirrup ratios. For the specimens with the\nsame ratios of stirrup, as the corrosion level increased, the load-carrying capacity, deformation capacity, stiffness, and energy\ndissipation capacity were continuously decreased. For the specimens with the same levels of corrosion, the higher the stirrup ratio\nwas, the stronger the restraint effect of the stirrups on the concrete, and the seismic behaviours of the specimens were\nobviously improved....
Construction worker safety and safety training continue to be the main issues in the construction industry. As a means of\nimproving construction worker safety, this study focuses on safety training at an actual construction worksite. In order to promote\nsafety awareness among workers, it is imperative to develop more effective safety training. This study examined safety training as a\nmethod of improving construction worker safety, focusing on the effectiveness of the instructional delivery method. Effectiveness\npertains to level of understanding of instruction and can be enhanced through improving instructional delivery method. This\nstudy aims to examine two different types of safety training methods: (1) the conventional lecture method and (2) innovative\nmethod using the 3D Building Information Modeling (BIM) simulation, reflecting the hazard condition of the actual site. An\nexperiment is conducted, in which the two types of training are implemented and assessed through testing traineesâ?? understanding.\nThe workers trained via BIM simulation showed a higher level of understanding than the group of workers who were\ntrained conventionally. Also, a survey was conducted targeting safety managers, in which the workers evaluated lifelike quality of\nthe training, active learning and enjoyment that each of the training methods can promote. This research will provide implications\nthat an innovative method using the virtual reality is more effective than the conventional lecture method....
Urban subway construction inevitably causes disturbances to the rock strata. It can even cause ground collapse accidents when\nconstruction encounters a bad geological body in the stratum. To verify the influence of cavities on surface settlement and the\nmechanism of formation instability, the instability mechanism of cavity-bearing strata under tunnel excavation disturbance was\nherein studied by tests using self-designed indoor models and numerical simulations. This study was based on the concrete project\ncase of Qingdao Metro. Two groups of experiments (with and without cavities) were designed to simulate the four-step excavation\nby staged unloading of an airbag. The results show that the settlement value in the cavity state was about twice as much as that in\nthe nonvoid state at the same stage. Besides the first step of excavation, in the numerical simulation, the settlement value of the\nsame stage is about 1.3 times that of the model test. Simulating the deformation process of the surrounding rock in model tests\nshows that, in the excavation of the tunnel, the collapse surface of the tunnel arch roof will be connected with the sliding surface of\nthe formation cavity. The cavity will gradually change from a regular circle to an ellipse or may even close, resulting in a sudden\nincrease in land subsidence or even ground collapse. This indicates that disturbance during tunnel excavation would cause greater\ninstability in a stratum when bad geological bodies, such as cavities, exist in the stratum....
In the process of tunnel construction, the problems of strong sealing, inconvenient communication, and harsh environment\npose a serious threat to the personal safety of construction workers. Therefore, personnel positioning technology has important\napplication value in tunnel safety construction. A special environment for tunnel personnel positioning and the ultrawideband\n(UWB) positioning system are affected by personnel movement, which leads to the problem of lowering positioning accuracy.\nA wavelet threshold denoising method for motion positioning of people in tunnels is proposed. The positioning algorithm of\nthe method adopts a three-sided positioning algorithm based on symmetric double-sided two-way ranging. The wavelet\nanalysis is used to decompose the motion signal of the personnel in the tunnel, and the low frequency coefficient and high\nfrequency coefficient of the signal are decomposed to determine the influence of the motion noise of the personnel on the UWB\npositioning. The soft threshold function and the hard threshold function are, respectively, selected to perform wavelet\nthreshold denoising on the motion positioning result in the tunnel. According to the denoising effect, the db5 wavelet 5-layer\ndecomposition, under the heuristic threshold estimation criterion, the soft threshold function denoising is the best denoising\nmethod. The verification by the positioning experiment shows that the method is suitable for tunnel personnel positioning. The\nwavelet threshold denoising method can weaken the influence of outliers in the motion positioning of UWB personnel and\nimprove the positioning accuracy....
The effectiveness and the safety of road construction depend on many factors that pose the greatest risk to system safety.Theaim of\nthis study is to conduct a comprehensive assessment for these risk factors to contribute to the safety performance of road\nconstruction. To achieve this goal, this study constructs a hierarchical safety assessment framework comprising comprehensive\nrisk indicators according to rich work experience and a relevant literature review and then proposes a group AHP-PCA (group\nanalytic hierarchy process-principal component analysis) to calculate the weights of relevant risk factors. The important rankings\nof a case study using GAHP-PCA show that professional skill, safety education, and work attitude are the most important factors,\nwhich are consistent with the experience and knowledge of road construction safety management. The results also demonstrate\nthat judgment dispersion naturally existing in classical AHP can be effectively reduced when combined with PCA, which is the\ninnovation point of the method given in this article....
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