Improved Powder Equivalence Model for the Mix Design of Self-Compacting Concrete with Fly Ash and Limestone Powder

The use of fly ash (FA) limestone and powder (LP) in combination with cement in concrete has several practical, ecological, and economic advantages by reducing carbon dioxide emissions, reducing the excessive consumption of natural resources, and contributing to a cleaner production of self-compacting concrete (SCC). A mix design method for SCC based on paste rheological threshold theory can guide the SCC mix design by paste tests. This method can be visualized by the self-compacting paste zone (SCP zone), a plane area where all the mix points meet the paste threshold theory, and SCC zone, a plane area consisting of all the mix points satisfying the criteria of qualified SCC. In the case of cement SCC, the SCP zone coheres with the SCC zone. However, in the case of the addition of FA or LP with different granulometry and shape characteristics from cement, experimental results indicate that the SCP zone is separated from the SCC zone. This work quantitatively studied the influence of FA and LP on the movement of the SCP zone by introducing the improved powder equivalence model. The improved model was obtained by powder equivalence coefficients calculated through the mortar test results with or without FA or LP, instead of SCC tests in the former method. The equivalence coefficients by volume of FA and LP are 0.55 and 0.79, respectively, which means that 1.82 unit volume of FA or 1.27 unit volume of LP is equivalent to one unit volume of cement. The improved powder equivalence model was verified by the successful preparation of SCC incorporating FA or LP simply and effectively. The equivalent SCP zone cohered better with the SCC zone than the former SCP zone, which could guide the quick mix design of SCC without SCC premix tests.

SHIPS WITH SMALL WATER-PLANE AREA: THE MAIN INFORMATION

Ships with small water-plane area (below “SWA ships”) have very special shape of hulls. It is the reason of characteristic specificity of such ships. SWA ships usually are multi-hull ones. And as all multi-hulls, SWA ships differ from the comparable mono-hulls by bigger deck area relative the displacement and by simple ensuring of stability. There are some architectural types of SWA ships. Their differences are shown by the article. Relative area of deck and initial transverse stability of SWA ships are compared. Statistical data on performance: twin-hull SWA versus catamarans. Common specificity of and . The main external loads. Special method of designing. Main disadvantages. Conclusions, recommendation.

PROFITABLE HIGH-SPEED PASSENGER VESSEL FOR SHORT LINES AT SEA

The paper [1] had presented an alternative option of outrigger high-speed passenger vessel for short lines. Such ships can compete with existed ones from economy point of view if the firsts will have minimal cost of building and minimal operation price, firstly – because of minimal outlay of fuel, but for comparable service speed and capacity of passengers. Besides, usually small enough vessels are strongly affected by weather, by waves in main. It means, seaworthiness of such ships is a permanent problem if they must operate at more or less severe conditions of weather. Two newly proposed options of outrigger ships are described below: the first has small water-plane area of the main hull bow, and the second has small water-plane area of the main hull as a whole. The selection of the main dimensions are shown in main, the results are discussed from seaworthiness point of view. Both new options are recommended for further designing, including researching of motion characteristics and possible economy results.

PENGEMBANGAN MEDIA PEMBELAJARAN KONSEP LUAS BIDANG DATAR BERBASIS PERANGKAT LUNAK GEOGEBRA

Abstract�This study aims to produce GeoGebra-based learning media of plane area concept that is valid, practical, and has good potential effects. This research use development research method or development research of formative research type which is simplified. Learning media development procedure in this research consists of 3 stages: 1) self evaluation, 2) prototyping (validation, evaluation and revision), 3) Field test. The results of research can be explained that: 1) the development of GeoGebra-based learning media of plane area concept in MTs Kab. Bandung valid based on contents, language, and conformity of context used and practical based on ease of use of students, 2) trials result of development of GeoGebra-based learning media of plane area concept given in MTs Kab. Bandung has a potential effect, namely: students love to learn with computer media, students love to learn with GeoGebra software, GeoGebra-based learning media of plane area concept helps students understand the area concept, learning media of area rectangular is most helpful to students understand the area concept.Keywords: learning media, GeoGebra, area, plane

A Novel Approach for Selecting Main Dimensions of New Sandglass-Type FPSO

In order to fully exploit the potential of FPSOs in the development of offshore oil field, a new concept of sandglass-type FPSO has been put forward recently. In this paper, a novel approach is proposed for designing the main dimensions of the new sandglass-type floating body. With the application of the strip method, the wave-free frequency in heave motion is intensively investigated. The resulting expression shows that the wave-free frequency has close connection with the water-plane area and the corresponding added mass. Then a uniform approximation of the relationship between the added mass and the main dimensions of structure below the waterline is discussed. By comparing with the numerical results of minimum heave RAO of heave motion, the validity and rationality of the proposed method are verified. Besides, experiments are carried out for the sandglass-type floating model and the results support the numerical results and the proposed method. Finally, combining with other requirements in the configuration of the structure above the waterline for the operation at sea, the design scheme for the main dimensions of the sandglass-type FPSO is established.

Experimental and Numerical Investigation on the Effect of Varying Hull Shape Near the Water Plane on the Mathieu-Type Instability of Spar

Spar platforms have been used for oil and gas exploration in deep water for the past two decades. Spar experience low heave and pitch motions in operating conditions with its deep draft and large inertia. The heave motions can be large when encountered by long period swells. These resonant response leads to unstable motions due to heave-pitch coupling in spar platforms when the heave/pitch natural period ratio is 0.5, 1.0, 1.5 and 2.0, referred to as Mathieu-type instability. This instability can be avoided by changing heave or pitch natural periods, so that the heave-pitch coupling can be avoided. The buoy form Spar proposed in this study is a cylindrical hull with curved surface near the water plane. A classic Spar of 31 m diameter and deep draft buoy form Spars with 25 m and 20 m diameter at the water plane area have been considered. The moon pool diameter of 12.5 m and the displacement of 63000 tonnes are maintained for all Spars. The experimental investigations are conducted using 1:100 scale models in the wave flume. Numerical simulations have been carried out using panel method. The classic Spar experiences Mathieu-type instability, since the heave/pitch natural period ratio is 0.5. The heave natural period of the buoy form Spar is higher than the classic Spar by 24% and 72%. The heave/pitch natural period ratio of the first buoy form Spar with 25 m diameter at the water plane area is 0.667; hence the heave-pitch coupling is avoided. The second buoy form Spar with 20 m diameter at the water plane area does not experience Mathieu-type instability, even though the heave/pitch natural period ratio is 1.0. Also the heave natural period of the second buoy form Spar is 36s (3.6 s in scale model) which is much above the design wave period. The possibility of Mathieu-type instability is avoided in the Spar by varying the hull shape near the water plane.