Selecting the criterion for diagnosing imbalance of electric mining shovel rotors

The limit state criteria for a mining shovel mechanical equipment that contains the faults of a rotor imbalance-type are studied in the article. On the bases of a statistical analysis of mining shovel failures, it is demonstrated that rotor imbalance is a prevailing reason for their accident-caused failures. On the bases of three-year monitoring of supporting elements vibrating activity the vibratory norms for electrical mining shovel rotors that take into account their service condition are substantiated.

New service limit state criteria for reinforced concrete in chloride environments

In chloride environments, reinforcement stress limits, intended to control flexural cracking, are one of the most important requirements for service limit state (SLS) design. However, concrete damage at the steel-concrete interface between bending cracks, so called cover-controlled cracking, is always correlated to areas of severe steel reinforcement corrosion. Based on the assumption that cover-controlled cracking should be limited, a model has been developed to provide alternative reinforcement stress limits in marine exposure conditions such as concrete in sea water, including permanently submerged, spray zone and tidal/splash zone, as well as coastal constructions located within 1 km of the shoreline. In this paper, the new reinforcement stress limitation is compared to the Australian Standards AS3600 concrete building code and AS5100.5 concrete bridge code provisions. Analysis shows that the new model is very sensitive to the reinforcement percentage of the cross-section. As a result, the existing AS3600 and AS5100.5 code provisions are more conservative than the new limitation for lightly to normally reinforced concrete cross-section. In this case, crack width control governs the SLS design. However, for normally to heavily reinforced concrete cross-section, the new model provides more conservative results suggesting that cover-controlled cracking governs the SLS design.

An Automated Approach for Optimizing Monopile Foundations for Offshore Wind Turbines for Serviceability and Ultimate Limit States Design

Pile foundation design is conventionally conducted using a process of trial and error, where the dimensions of a pile are estimated and the performance is computed and compared with design criteria. The dimensions are varied and the process is repeated in order to converge to a safe and economical design. In this paper, this time-consuming and labor intensive process is replaced with an automated approach using the example case of an offshore monopile supporting a wind turbine. The optimum length and diameter of the monopile are determined with the aim of minimizing the pile weight while satisfying both serviceability and ultimate limit state criteria. The approach handles general soil and loading conditions and includes an ability to incorporate cyclic loading.

Reeling Analysis and Limit State Criteria

Reeling has been an attractive offshore installation method for rigid flowlines and steel catenary risers due to its fast speed, cost effectiveness and reliability. Over years of evolution, it has become a proven technology, and the understanding to the engineering fundamentals is greatly improved as well. Due to the reeling process, the pipeline is plastically deformed; residual stresses, pipe ovality, and pipe out of straightness are increased. The strength, fatigue, and fracture performance of the pipe and the girth weld have to be closely evaluated to insure the pipeline integrity during and after the installation. As part of the installation design, different types of analyses are generally carried out to demonstrate the reelability, and the pipeline responses against all limit states. However, the methods adopted by different contractors can vary greatly. In this paper, the engineering fundamentals of reeling process are reviewed. A few typical reeling analyses, both analytical and finite element based, are demonstrated with examples. The local buckling limit state criteria based on DNV-OS-F101 for different stages of reeling are also illustrated.

Mathematical Foundations of Limit Criterion for Anisotropic Materials

In the paper a new proposition of limit state criteria for anisotropic solids exhibiting different strengths at tension and compression is presented. The proposition is based on the concept of energetically orthogonal decompositions of stress state introduced by Rychlewski. The concept of stress state dependent parameters describing the influence of certain stress modes on the total measure of material effort was firstly presented by Burzynski. The both concepts are reviewed in the paper. General formulation of a new limit criterion as well as its specification for certain elastic symmetries is given. It is compared with some of the other known limit criteria for anisotropic solids. General methodology of acquiring necessary data for the criterion specification is presented. The ideas of energetic and limit state orthogonality are discussed - their application in representation of the quadratic forms of energy and limit state criterion as a sum of square terms is shown