Search Results (7)

This paper presents laboratory devices on which measurements were carried out to prove the validity of the assumption about the reduction in vibrations transmitted to the conveyor belt structure generated by the impact forces of falling material grains in the places of transfer or on the hoppers of conveyor belts. In order to limit damage to the conveyor belts caused by the impact of the sharp edges of material grains, conveyor belts are supported by impact rollers or impact rubber rods. A special modification of the fixed conveyor idler is presented, which consists of inserting plastic brackets into the structurally modified roller axle holders of the fixed conveyor idler. Measurements showed that the specially modified fixed conveyor idler resulted in a higher damping of up to 15% of the impact forces of the falling weight on the rubberized hoop of the impact roller shell compared to the conventional fixed conveyor idler design. Measurements carried out show that the effective vibration velocity values detected at the points where the impact roller axis fits into the fixed roller table holder are higher than when using plastic brackets, up to 6% for a 108-mm-diameter roller, compared to steel impact roller brackets. Full article

The study’s objective is to analyze the mechanical properties of steel pipe piles as a part of a trestle bridge subjected to five years of natural marine corrosion degradation. Sixteen tensile specimens are extracted from the steel pipe piles in the splash, tidal, and immersion zones. The experimental tensile test results are used to establish regression equations defining the elastic modulus, yield strength, strain hardening index, and strength coefficient for the true stress–strain curves of the three regions. A non-linear time-dependent mathematical model is exploited to identify the corrosion degradation, using the data from one single corrosion degradation measurement campaign. The analysis indicates that the splash zone is experiencing the most severe corrosion degradation, and there are progressive losses in the mechanical properties of each zone as the corrosion degradation progresses. The established relationships of the mechanical properties, as a function of the ratio of corroded plate thickness to the as-built one, can be used as a fast-engineering approach to identify the mechanical properties of severely corroded piles. The corrosion degradation allowance is also defined using the first-order reliability method, accounting for existing uncertainties covered by the partial safety factors. By examining the impact of marine corrosion on the mechanical properties of marine structures and developing predictive models to assess the corrosion’s effect on material strength and corrosion allowance, the study aims to improve offshore structures’ safety, design, and maintenance. Full article

This paper presents the basic structural parts, a 3D model, and the overall design of a laboratory machine, which was created to detect vibrations generated by the casing of a conveyor roller rotating at different speeds. The intention of the authors was to verify whether plastic brackets inserted into the structurally modified trestles of a fixed conveyor idler can reduce the vibration values transmitted from the rotating conveyor roller to the trestle of a fixed idler. Experimental vibration measurements taken on the non-rotating parts of conveyor rollers, performed on a laboratory machine according to ISO 10816, are suitable for characterizing their operating conditions with regard to trouble-free operation. The aim of this paper is to detect the vibrations of a rotating conveyor roller on a laboratory machine in the defined places of a fixed conveyor idler and also on the steel frame of a laboratory machine that represents the supporting track of a belt conveyor. Vibrations detected by piezoelectric acceleration sensors were recorded by a measuring apparatus and displayed in the environment of Dewesoft X software (version 10). The measurements show that the vibration values grow with the increasing speed of the conveyor roller rotation. Experimental measurements have proven the correctness of the assumption that the vibrations transmitted to the trestle of a fixed conveyor idler are lower by up to 40% when using plastic brackets into which the axle of the conveyor roller is attached, compared to the solution where the axle of the conveyor roller is inserted into the notches of a steel trestle. Full article

Thermal power plants play a crucial role in the power system as critical lifeline infrastructure. In order to meet the production process requirements, the main building of a thermal power plant is often connected to a coal conveyor trestle. This study focuses on investigating the seismic interaction between the common three-row reinforced concrete frame-bent main building and the steel trestle in a circulating fluidized bed (CFB) unit. The objective is to assess the influence of the trestle on the main building and understand the failure mode of the trestle structure. The seismic interaction is analyzed through fragility analysis based on Incremental Dynamic Analysis (IDA). The results indicate that the trestle has minimal influence on the main building, except during the large deformation stage. The study identifies the failure mode of the coal conveyor trestle as excessive relative displacement along the longitudinal direction at the connection points, leading to collisions or falls. A seismic demand model based on longitudinal relative displacement is developed to obtain the fragility curve for the trestle structure. These findings offer valuable insights for assessing the seismic performance of thermal power plants. Full article

Different systems of fire protection coatings are used to protect the metal structures of stories and trestles at oil and gas facilities from low (when filling cryogenic liquids) and high temperatures (in case of the possible development of a hydrocarbon fire regime). This paper presents the results of experiments of fireproof coatings on an epoxy binder after the simulation of a liquefied hydrocarbons spill and subsequent development of a hydrocarbon fire regime at the object of protection and exposure of structures to a standard fire regime. According to the experimental results, the temperatures on the samples at the end of the cryogenic exposure were determined and the time from the beginning of the thermal exposure to the limit state of the samples at a hydrocarbon and standard temperature fire regime was determined. As a result, temperature–time curves in the hydrocarbon and standard fire regimes were obtained, showing good convergence with the simulation results. The solution of the inverse task of heat conduction using finite element modeling made it possible to determine the thermophysical properties of the formed foam coke at the end of the fire tests of steel structures with intumescent coatings. It was determined that an average of 12 mm of intumescent coating thickness is required to achieve a fire protection efficiency of 120 min and for the expected impact of the hydrocarbon fire regime, the coating consumption should be increased by 1.5–2 times compared to the coating consumption for the standard regime. Full article

This article explores technical and socio-political factors that impacted construction of the Gokteik Viaduct railway bridge in Shan State, Burma, and the recurring failure of political powers to complete a continuous railway between Rangoon (Yangon) and Yunnan. Under rather contentious circumstances, the British government awarded an American steel company with the contract to construct what would become the world’s longest railway trestle bridge at the time of its completion in 1900. As an engineering marvel of its era, the Gokteik Viaduct is in the same category as the Eiffel Tower in Paris. Until now, however, scarce research has explored the Gokteik Viaduct in terms of historicity and factors that ultimately prevented this structure from fulfilling its intended purpose of transporting trainloads of marketable goods between Burma and Yunnan. This raises an ironic question: How could engineers construct such a remarkable bridge to service a railway that was never finished? Furthermore, why does the Gokteik Viaduct largely remain unexamined in terms of its noteworthy place in the geopolitics of Southeast Asia? In answering such questions, the authors conclude that the “unseen” story of the Gokteik Viaduct is not only about engineering prowess but of a political and social environment that continues to bedevil massive infrastructure projects in Upper Burma today. Full article

Offshore steel trestles (OSTs) are exposed to severe marine environments with stochastic wave and current loads, making structural safety assessment challenging and difficult. Reliability analysis is a suitable way to consider both wave and current loading intensity uncertainties, but the implicit and complex limit state functions of the reliability analysis usually imply huge computational costs. This paper proposes an efficient reliability analysis framework for OST using the kriging model of optimal linear unbiased estimation. The surrogate model is built with stochastic waves, current parameters, and the corresponding load factors. The framework is then used to evaluate the reliability of an example OST subjected to wave and current loads at three limit states of OST, including first yield (FY), full plastic (FP), and collapse initiation (CI). Three different distributions are used for comparison of the results of failure probability and reliability index. The results and the computational cost by the proposed framework are compared with that from the Monte Carlo sampling (MCS) and Latin hypercube sampling (LHS) method. The influences of sample number on the prediction accuracy and reliability index are investigated. The influence of marine growth on the reliability analysis of the OST is discussed using MCS and the kriging model. The results show that the reliability analysis based on the kriging model can obtain the reliability index for the OST efficiently with less calculation time but similar results compared with MCS and LHS. With the increase of the number of samples, the prediction accuracy of the kriging model increases, and the corresponding failure probability fluctuates greatly at first and then tends to be stable. The reliability of the example OST is reduced with the increase of marine growth, regardless of the limit state. Full article