Research on Engineering Structures and Materials

231-240

Authors: Khaled Yaghi, Housam Hammoud

Strength evaluation of fire damaged concrete is not well studied although fire damaged concrete is encountered in many settings. There are limited studies that investigate the effect of physical properties on the strength of fire damaged concrete. In this paper, a fire damaged concrete slab element is evaluated based on non-destructive (rebound hammer and impact pulse velocity) and destructive (core and porosity) testing. Two correlation models are developed to assess the compressive strength of the slab element. The first model correlates the corrected core compressive strength to rebound number, impact pulse velocity and porosity. The second model correlates the corrected core compressive strength to rebound number and impact pulse velocity. Both correlation models are based on Pearson’s statistical approach. The two correlations are compared based on William’s modification of the Hotelling test and results indicate that rebound number, impact pulse velocity and porosity combined correlates more significantly to the corrected core compressive strength than rebound number and impact pulse velocity alone.

257-277

Authors: M. G. Sobamowo

In this paper, unsteady squeezing flow of Casson nanofluid between two parallel plates embedded in a porous medium and subjected to magnetic field is analyzed. The developed systems of partial differential equations for the fluid flow models are converted to ordinary differential equations through suitable similarity variables. The obtained ordinary differential equation is solved using method of matched asymptotic expansion. The accuracies of the approximate analytical method for the small and large values of squeezing numbers are investigated. Good agreements are established between the results of the approximate analytical method and the results numerical method using fourth-fifth order Runge-Kutta-Fehlberg method. Thereafter, the developed approximate analytical solutions are used to investigate the effects of pertinent flow parameters on the squeezing flow phenomena of the nanofluids between the two moving parallel plates. The results established that the as the squeezing number and magnetic field parameters decreases, the flow velocity increases when the plates come together. Also, the velocity of the nanofluids further decreases as the magnetic field parameter increases when the plates move apart. However, the velocity is found to be directly proportional to the nanoparticle concentration during the squeezing flow i.e. when the plates are coming together and an inverse variation between the velocity and nanoparticle concentration is recorded when the plates are moving apart. It is hope that this study will enhance the understanding the phenomena of squeezing flow in various applications.

297-323

Authors: Adeshina S. Adegoke, Ayo A. Oyediran

This paper studied the planar dynamics of top tensioned cantilevered pipes conveying pressurized steady two-phase flow under thermal loading. The governing equations of motions were derived based on Hamilton’s principle, the centerline is assumed to be extensible in order to account for possible thermal expansion; resulting to a set of coupled axial and transverse partial differential equations. Analytical approach was used to resolve the governing equations using the multiple scale perturbation technique, which aided the development of theoretical schemes for estimating the natural frequencies and mode shapes. Numerical results were presented for a case study of two phase flow of water and air with the stability and dynamic behavior of the system studied linearly via Argand diagrams which were constructed as the mixture flow velocity is increased for various void fractions. The Argand diagram assessment of the axial vibration natural frequencies shows that the attainment of the critical velocity is delayed for a cantilever pipe conveying two phase flow compared to when the pipe is conveying single phase flow. The result of the linear analysis of the transverse vibration reveals that at the critical mixture velocity, the system loses stability through Hopf bifurcation. Similarly, to the axial vibration, the attainment of the critical velocity was observed to be at higher velocities for a cantilever pipe conveying two phase flow as compared to when the pipe is conveying single phase flow. In addition to, the critical velocity is observed to be increasing as the void fraction of the two phase flow increases. The assessment of the effect of thermal loading, pressurization and top tension on the attainment of the critical velocity shows that thermal loading, pressurization and compression at the tip hastens the attainment of the critical velocity while tensioning top tension delays the attainment of the critical velocity.