Upper Part Of Column Research Articles

Parametric study of wave impact pressure impulse and characteristic pressure on a square column with overhanging deck

Semi-submersible platforms may suffer safety accidents due to severe wave impacts on the decks and columns in extreme ocean environment. The pressure impulse considering the cumulative effect of time is significant for the dynamic response analysis of offshore and coastal structures, and has attracted attentions in recent years. In this study, wave impact tests on a square column with overhanging deck were carried out under a series of fifth-order Stokes waves with large steepness to investigate the influence parameters on the impact pressure impulse. A novel definition of characteristic pressure is proposed from the perspective of pressure impulse, meanwhile, its dimensionless relation with the peak impact pressure is presented. The spatial distributions of the pressure impulse and characteristic pressure on the square column with overhanging deck, as well as the influences of several environmental and model parameters are discussed in detail. The results show that the spatial distributions and vertical variations of wave pressure impulse are affected significantly by the wave parameters, initial air gap, column incline angle and wave incidence angle. In general, the wave impact on the overhanging deck and the upper part of column is severer, and the inclination of column can reduce the pressure impulse to some extent. The research findings may provide references for further research and the predesign of the column–deck structure of semi-submersibles.

Effect of the position of core on the strength of concrete of columns in existing structures

Engineers usually evaluate existing structures by core tests, which are affected by several factors. Two of the main factors that affect the strength of the core are their location and method of construction. The combination of these factors has not been given special attention by researchers.In this research, the author investigates the combined effect of the position of core and the method of construction on the strength of vertical members in existing structures. Three various methods of construction are included: one manual casting and two pump casting. 147 cores from different existing buildings were extracted from various columns' locations and then tested.The tests included in the study are the rebound hammer, the pulse velocity through concrete and the core crushing strength. The results show that the method of construction and the position of cores are critical factors in determining the strength of the concrete in existing structures. In manually casted columns, using all testing methods, the strength was low at the lower and upper ends of the column and most are below 75% of characteristic strength. In this case, the rebound hammer values are usually misleading. In all construction methods, the strength of cores is always low in the upper parts of column. In the upper parts, 33–66.7% of the cores failed to pass the 75% limit while in the lower parts the ratio ranged between 0 and 93%. The pulse velocity showed better expected results than the rebound hammer. All methods proved that the internal 2 m height have the highest strength.It is recommended that specifications must include these factors when analyzing the core results. Also, the results can be used as a guide for locating representative correct positions of cores in vertical members. Various standards and specifications can benefit from results.

Spiranthes himalayensis (Orchidaceae, Orchidoideae) a new species from Asia.

Spiranthes himalayensis is described here as a new species based primarily on molecular phylogenetic evidence followed by morphological comparison with other Asian Spiranthes species. It is distributed widely from southern India to tropical China. Phylogenetic analysis shows its close affinity to S. nivea which is endemic to Taiwan. Morphologically, the new species looks close to S. sinensis and S. hongkongensis. S. himalayensis is an allogamous species which can be differentiated from its allies on the basis of pubescent plant body, floral bract longer or of the same length as that of ovary, petals with blunt apex, labellum width around hypochile same as the width of epichile, epichile widely flabellate or semi-tunicate, column length equal to or more than 1.5mm, clavate operculum attached to the column on the broader part by an arm-like extension emerging from the upper part of column and a well developed rostellum partitioning the stigma and pollinarium.

Effect of Geotextile Encapsulation on Lime Column Axial Stress in Pontain Marine Clay

Previous researchers reported that problematic soft clay can be improved by deep lime stabilization. However, due to low confining pressure of surrounding soil, problems often occurred at top part of column which reduced the performance of lime column, such as: crushing at column head and higher settlement for surrounding soil at the upper part of column. Geotextile encapsulated lime column (GELC) was proposed in this study. The stresses on column are essential in the analysis on columnar improved soil. Multi-stage loading test was conducted on lime column and GELC stabilized Pontian marine clay aged 14 days, 28 days and 56 days in order to investigate axial stress on lime column and GELC stabilized Pontian marine clay. Geotextile encapsulation increased the compressive strength of lime column about 70 percent at axial strain of 8 percent.

水溶液中の微量有害有機物の除去に対する溶媒浮選法の適用

Removal of 12 organic compounds containing chloro-chemicals from an aqueous solution has been carried out using solvent sublation. The removal mechanism of solvent sublation was studied, from which the calculated value for removal was obtaind to compare with the experimental results.The removal rate of organic compounds is strongly concerned with the physical and chemical properties of their compounds, such as solubility, vapor pressure, surface tension and distribution coefficient between the aqueous and organic phase. The experimental removal rate is evaluated and discussed concerning the physical and chemical properties of the compounds to be removed. A model for the removal mechanism is constracted by considering several terms such as adsorption on bubble, entrainment with boundary layer of bubble, vaporization to bubble and mass transfer to the organic solvent in the upper part of column. The calculated value is in good agreement with the experimental results. According to the removal model, contribution percentage of the above terms is estimated and then it is clarified which terms are significant for the removal of the organic compounds with different chemical properties.