Critical Top Tension for Static Equilibrium Configuration of A Steel Catenary Riser

This paper aims to present the critical top tension for static equilibrium configurations of a steel catenary riser（SCR） by using the finite element method. The critical top tension is the minimum top tension that can maintain the equilibrium of the SCR. If the top tension is smaller than the critical value, the equilibrium of the SCR does not exist. If the top tension is larger than the critical value, there are two possible equilibrium configurations. These two configurations exhibit the nonlinear large displacement. The configuration with the smaller displacement is stable, while the one with larger displacement is unstable. The numerical results show that the increases in the riser＇s vertical distances, horizontal offsets, riser＇s weights, internal flow velocities, and current velocities increase the critical top tensions of the SCR. In addition, the parametric studies are also performed in order to investigate the limit states for the analysis and design of the SCR.

Ancient Materials and Substitution Materials Used in Thai Historical Masonry Structure Preservation

The historical structures of Thailand are some of the most fascinating ancient sites in Asia.Their architectures reveal past cultures,traditions,knowledge,and expertise.Masonry materials are the major materials used to construct the historical structures in Thailand.One of the essential problem of Thai historical structure preservation is a shortage of engineering properties data for the structural stability assessment.Moreover,the in-depth engineering properties and the suitable substitution materials for Thai historical preservation are rarely found.Therefore,the engineering properties of the ancient masonry materials have to be explored together with the development of suitable substitute materials.This paper presents the physical and engineering properties of ancient materials and substitution materials for the preservation of Thailand’s historical structures.The ancient materials,including brick and mortar,are collected from historical places in the Bangkok and Ayutthaya Provinces.The physical and engineering properties of the masonry materials,such as the chemical composition,mineralogical composition,density,porosity,absorption,water vapor transmission,compressive strength,and modulus of elasticity,were evaluated in the laboratory.Fly ash was used as a pozzolanic material to partially replace the slaked lime to restore the historical mortar.The binder to sand ratio was controlled at 1:3 by weight.The slaked lime was substituted by fly ash at the rates of 10–30%by weight of binder.The engineering properties of the substitution mortars were also evaluated and compared with the ancient masonry materials.A masonry prism was also constructed to evaluate the compressive strength and the modulus of elasticity of the masonry structures.The physical and engineering properties of the ancient masonry materials obtained in this study can be included in a database for the preservation of Thailand’s historical masonry structures.The use of fly ash to partially replace the slaked lime could decrease the setting time and increase the compressive strength of historical repair mortar.The empirical equation obtained from this study could be used to predict the compressive strength of the masonry prisms of Thailand’s historical structures.