American Journal of Civil Engineering and Architecture
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  This is an Open Access Journal Open Access journal
     ISSN (Print) 2328-398X - ISSN (Online) 2328-3998
     Published by Science and Education Publishing Homepage  [19 journals]
  • Influence of the Density of Water on the Dynamic Behavior of Square
           Tension Leg Platform

    • Authors: Hala M. Refat; Amr R. El-gamal
      Pages: 122 - 129
      Abstract: tension-leg platform (TLP) or extended tension leg platform (ETLP) is a vertically normally used for the offshore production of or , and is particularly suited for water depths greater than 300 meters and less than 1500 meters. The platform is permanently moored by means of tethers or tendons grouped at each of the structure's corners. A group of tethers is called a tension leg. A feature of the design of the tethers is that they have relatively high (low ), such that virtually all vertical motion of the platform is eliminated. This allows the platform to have the production on deck (connected directly to the subsea wells by rigid risers), instead of on the . This allows a simpler and gives better control over the production from the or , and easier access for down whole intervention operations. In this paper a numerical study for a square TLP using modified Morison equation was carried out in the time domain with water particle kinematics using Airy’s linear wave theory to investigate the effect of changing water density on the mass matrix of TLP's and the dynamic behavior of TLP's. The effect was investigated for different parameters of the hydrodynamic forces such as wave periods, and wave heights. The numerical study takes into consideration the effect of coupling between various degrees of freedom. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables. Nonlinear equation was solved using Newmark’s beta integration method. Only uni-directional waves in the surge direction was considered in the analysis.
      PubDate: 2014-06-22
      Issue No: Vol. 2, No. 4 (2014)
       
  • Determination of Subsurface Geotechnical Properties for Foundation Design
           and Construction in Akenfa Community, Bayelsa State, Nigeria

    • Authors: Nwankwoala H.O; Amadi A.N, Ushie F.A, Warmate T.
      Pages: 130 - 135
      Abstract: This study aims at establishing the sub-soil types and profile to ascertain the geotechnical characteristics of the underlying soils in Akenfa in Yenagoa, Yenagoa Local Government Area of Bayelsa State, Nigeria and recommend appropriate foundation design and construction of projects in the area. Three (3) geotechnical boreholes were drilled at the site to obtain baseline data on geotechnical properties of the soil and water level monitoring, the boreholes were advanced with the use of a cable percussion boring rig and were terminated to a maximum depth of 30m. The particle size distributions of a number of representative samples of the cohesionless soils were determined by sieve analysis. The results show that the samples are low to medium plasticity silty clay. The lithology revealed intercalations of clay and sand in thin layers to a depth of 2.0 m below the existing ground level. Underlying this clay is a stratum of loose to medium dense sand and dense sand. The sand is well sorted grading from fine to medium as the borehole advances. The laboratory analysis showed that the silty clay has undrained shear strength of 48 kPa. The loose sand has a maximum SPT (N) value of 12 while the medium dense sand has maximum SPT (N) value of 28. Considering the nature of the civil structures to be sited in the area, it is anticipated the load and the moderate compressibility of this near surface silty clay and the underlying loose silty sand be supported by means of raft foundation founded within the clay layer. It is recommended that studies on the geotechnical characteristics of the area be carried out as it provides valuable data that can be used for foundation design and other forms of construction for civil engineering structures in order to minimize adverse effects and prevention of post construction problems.
      PubDate: 2014-08-07
      Issue No: Vol. 2, No. 4 (2014)
       
  • The Impact of Deep Foundations of Building Structures on the Neighbouring
           Buildings – a Static Analysis

    • Authors: Czesław Miedziałowski; Damian Siwik
      Pages: 136 - 142
      Abstract: Deep foundations of buildings and their impact on neighbouring buildings is one of the most important issues when planning a new facility. Whereas, the analyses of the threats often come down only to a simplified evaluation of the building subsidence and to comparing them with the limit values. The paper presents the methodologies for using the subsidence surface of the land behind the housing wall of the excavation to assess the impact of additional displacements on the technical condition of facilities, through the determination of the distribution and the values of stresses in the estimated structure.
      PubDate: 2014-08-12
      Issue No: Vol. 2, No. 4 (2014)
       
 
 
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