Seismic retrofit of substandard beam-column joint by planar joint expansion

A seismic retrofit technique for existing reinforced concrete beam-column connections using planar joint expansion is proposed. The method is based on a two-dimensional expansion of beam-column joint using cast in-situ concrete and dowel bars. The method is economical and architecturally acceptable. Three half-scale sub-standard beam-column specimens were tested under quasi-static cyclic loading. One was control specimen and the other two were retrofitted specimens with triangular and square joint expansion. According to test results, the control specimen showed brittle joint shear failure while retrofitted specimens showed beam flexural failure. The strength, stiffness, energy dissipation and ductility of retrofitted specimens were greatly improved. The planar joint expansion is effective to reduce joint shear stress and improve anchorage bond of beam bar within the joint. The plastic hinge formation can be moved away from column face, thus preventing joint shear failure. The triangular and square expansions perform almost equally well. The construction joints formed at the interfaces between specimen and joint expansion do not produce an adverse effect in cyclic behavior.     

Design of Porous Banana Foam Mat to Resist Moisture Migration Using a 2-D Stochastic Pore Network and Its Textural Property

The high porosity of dried banana foam allows it to quickly adsorb moisture from the air during storage, leading to a loss of quality and textural properties. Therefore, the main purpose of this research was to design and study banana foam structure at the pore level to limit moisture migration using a 2-D stochastic pore network. A 2-D network formed by the interconnection of cylindrical pores was used to represent the voids inside the banana foam and the moisture movement inside the individual pore segments during adsorption was described by Fick's law. The pore network was divided into two layers with different banana foam densities and the top surface of the network was exposed to humid air. The upper layer was assigned with pore sizes from the banana foam density of 0.31 g/cm³, having a void area fraction of 0.22, or from a density of 0.21 g/cm³, having a void area fraction of 0.31; the lower layer was assigned specifically with the pore sizes from the banana foam density of 0.26 g/cm³, having a void area fraction of 0.26. The predictions agreed well with the experimental results, with an R² value above 0.95. The two-layered banana foam mat with high banana foam density (characterized by mostly small pores) on the upper layer could limit the transport of moisture, with a rate relatively lower than that of a single-layered banana foam mat, and also exhibited more crispiness than the single banana foam. However, when the low banana density was in the upper layer, the two-layered sample adsorbed moisture quickly and its texture was less crispy.     

Effects of pore size distribution and pore-architecture assembly on drying characteristics of pore networks

Simulation of isothermal drying using two-dimensional networks comprised of interconnected cylindrical pores is presented. Transport of moisture inside pore segments was described by Fick’s law. The results have shown that the shielding of large pores by the smaller pores in the stochastic pore network, which is supposed to be representative of real porous medium, causes the lower drying rate and hence lower effective diffusion coefficient as compared to those predicted from the idealized network of pores with a single size. The strength of shielding is found to vary with the characteristics of pore size distribution as interpreted by the moisture concentration experienced by the pores, which is remarkably different amongst the pore size distributions. The inefficient transport of moisture through the stochastic pore network can be improved or even better with the suitable architecturally assembled structure. The minimum shielding archetype network, appearing very high porous at particle surface, is predicted to enhance greatly the drying rate. On the other hand, the maximum shielding network, which is small pores allocated onto the network exterior, exhibits the slowest drying rate.     

Investigation on thermal performance of glazed solar chimney walls

This paper reports investigation on the thermal performance of glazed solar chimney walls (GSCW) under the tropical climatic conditions of Thailand. The GSCW consisted of double glass panes with an air layer and openings located at the bottom (room side glass pane) and at the top (ambient side glass pane). A prototype of GSCW was integrated into the southern wall of a small room of 2.8 m³ volume. Its dimensions were as follows: 0.74 m height, 0.50 m width and 0.10 m air gap. The size of openings was 0.05 × 0.5 m². With a clear glass of 6 mm thickness, velocity field measurement indicated that the induced airflow rate was about 0.13–0.28 m³/s. The temperature difference between room and ambient was less than that with a single layer clear glass window. The reduction of daylight due to the double glass layer is negligible. Comparison between simulated and experimental results showed a reasonable agreement, therefore, the developed numerical model is valid and could be used as a tool for the design of GSCW.     

Assessment of heavy metal contamination and its mobilization from municipal solid waste open dumping site

Influence of heavy metals was investigated by conducting various tests on the samples collected from Nonthaburi dumpsite in Thailand. The heavy metal concentration in the solid waste and its mobility potential based on its binding forms was studied. The sequential extraction method was used to determine the binding forms of metals. From the analysis, Zn was found to be highest concentrated heavy metal compared to Mn, Cu, Cr, Cd, Pb, Ni and Hg in the solid waste. From the sequential extraction, Mn, Zn and Cd mostly found in reducible form, showed its susceptibility to be leached easily. Cu and Cr were found predominantly in oxidizable form and stable under anaerobic condition. Pb and Ni were present in residual form, which is inert. The estimated individual contamination factor (C(f)(i)), showed Zn with highest affinity to leach. The concentration level of all the heavy metals in the leachate except for Cr was noticed to be below the National effluent standards. Though, indicated to be safe for disposal, its effect in any concentration proved toxic to the plant life from the seed germination toxicity test using synthetic chelate ethylene diamine tetraacetic acid (EDTA).     

Effect of Adsorption Conditions on Effective Diffusivity and Textural Property of Dry Banana Foam Mat

Foamed banana product, a crispy snack, can quickly adsorb the moisture from the moist air, leading to loss of textural property. The main purpose of this research was therefore to study moisture adsorption kinetics of dry banana foam mat and its texture quality change. The adsorption isotherm experiments were carried out with a standard static method using saturated salt solutions over a wide range of relative humidities from 32 to 82% and temperatures of 35, 40, and 45°C. Three dry banana foam densities of 0.21, 0.26, and 0.30 g/cm³ adsorbed water vapor under controlled conditions. Fick's second law coupled with an optimization technique was used to estimate the effective moisture diffusivity at sorption conditions. Empirical equations with two and three constant parameters for describing the dependence of the effective moisture diffusivity on moisture content were tested. The two constant parameters could suitably describe the variation of the effective moisture diffusivity with moisture content. The initial foam density, relative humidity, and temperature significantly affected the effective moisture diffusivity. The banana foam mats for all densities lost their crispy texture at moisture content of 0.078 kg/kg db.     

Modelling of moisture diffusion in pores of banana foam mat using a 2-D stochastic pore network: Determination of moisture diffusion coefficient during adsorption process

The purpose of this research was to determine the diffusion coefficient of moisture in the pores of banana foam mat using stochastic pore network. A 2-D pore network was used to represent the pore voids inside the banana foam sample and the moisture movement inside the individual pore segments was described by Fick’s law. To determine the moisture diffusion coefficient, the adsorption experiments were carried out with standard static method using saturated salt solutions. Two banana foam densities of 0.21 and 0.26 g/cm³ were used to adsorb the water vapour. The interactions between moisture and pore structure were illustrated using a 3-D pictorial representation of network concentration gradients in spaces with colour representing the moisture content. The network model described the experimental results relatively well. The diffusion coefficient of moisture in pores was in order of 10^-9${10}^{-9}$ m²/s which was nine times higher than the effective diffusion coefficient calculated from the continuum model. The value of moisture diffusion coefficient was dependent on the temperature and independent of the foam densities and the relative humidity, except for the diffusivity determined from the condition at higher relative humidity of 70%.