China
Africa
Explore chapters and articles related to this topic
Foundations in structurally unstable soil
Published in B.I. Dalmatov, R.B. Zeidler, Soil Mechanics, Footings and Foundations, 2020
The growth of considerable non-uniform settlement upon construction of weak soil cannot always be avoided. Hence one must predict the possible deformation of structure. As a prevention measure, one should reduce the pressure exerted on the foundation soil. This can be achieved, in particular, by construction of a solid slab under the building or structure. Another method of reducing the pressure exerted on foundation soils consists in the design of cellars and basements. In certain situations the footing can float (the weight of soil removed during construction of the footing is equal to the weight of structure). Structures on floating footings should not cause consolidation of foundation soil because the stresses do not exceed the natural ones. However, as a result of unloading upon earth moving operations in the excavations, decompression of soil occurs, as pointed out in Section 9.2.3. Decompression settlement will therefore develop within the stratum of excavation. One should remember that the structure of the weak soils is very sensitive during earth moving operations (Section 9.2.), so respective prevention measures should be taken.
Fatigue life as a factor in assessing warship design flexibility to support batch-building programs
Published in J. Parunov, C. Guedes Soares, Trends in the Analysis and Design of Marine Structures, 2019
D.M. Dwyer, T. Magoga, B.A. Morris, G. Condon
To better understand the impacts of evolving mission and technological requirements in order to maximise fleet capability, RAN stakeholders will benefit from a deeper understanding of the relationships between the base platform’s design flexibility characteristics. Quantifying the physical space, weight, power and cooling limits, or rather reserve capacities, of the base platform allows any capability risks to be identified due to the physical demands of a technology upgrade, or changes in operational profile. One significant physical characteristic to consider in the flexibility assessment is the ships weight. The ‘…weight affects the ability of a ship to float upright (stability), its ability meet speed and seakeeping requirements, and its ability to withstand the ocean environment without breaking up (strength)’ (Cimino & Tellet, 2007 p. 5). Hence, the weight is tightly coupled to the structural and stability performance of the platform. Thereby, determining the structural and stability limits of the base platform, the flexibility, regarding weight, can be better understood. Also, new mission requirements may lead to operation in a different ocean environment. This is likely to influence the ship’s structural service life or fatigue life (Guzsvany et al., 2006, Magoga & Dwyer, 2018), and can be a new constraint on the ship’s stability.
Fluid Statics
Published in Jenn Stroud Rossmann, Clive L. Dym, Lori Bassman, Introduction to Engineering Mechanics, 2015
Jenn Stroud Rossmann, Clive L. Dym, Lori Bassman
The line of action of the buoyancy force acts through the centroid of the displaced fluid volume. The stability of an object designed to float on or maneuver in a fluid depends on the moments due to the buoyancy and weight forces on the object, and whether the resultant moment will tend to right or to capsize the craft. For submerged vessels that operate at a range of depths, mechanisms that allow active control of these forces are necessary. Tanks that can be flooded or filled with air to adjust the vessel’s weight mimic the swim bladder in fish to allow vessels to maintain the proper force balance.
Degradation properties of petroleum degrading bacteria immobilized on modified corn straw in marine environment
Published in Petroleum Science and Technology, 2018
Huachun Xu, Yanan Wu, Xinmiao Xu, Meng Gu, Deying Jiang, Jianliang Xue, Lin Li
With the increased of offshore oil exportation, and transportation, oil spill accidents were becoming more frequent year by year, which caused huge economic losses and devastated disasters for the ecology (Han, Nambi, and Prabhakar Clement 2018). For example, the Deepwater Horizon Oil Spill accident caused approximately 1.55 million square kilometers of marine pollution, which seriously damaged to the ecological environment along the Gulf Coast (Rabalais, Smith, and Turner 2018). In 2018, an Iranian oil tanker (Sanchi), carrying 136,000 tons of condensate, collided with another vessel in the East China Sea. Except no hope of finding survivors, lots of condensate leaked, causing serious seawater pollution. In these oil spill accidents, the oil floats on the surface of the seawater, which could affect the growth of marine plankton, destroy the ecological balance of the ocean (Melaku Canu et al. 2015).