Tawich Pulngern

Analytical and Experimental Studies on the Large Amplitude Free Vibrations of Variable-Arc-Length Beams:

Using the finite element method, we investigate large amplitude vibrations of horizontal variable-arc-length beams, considering the effect of large initial static sag deflections due to self-weight. The variability in beam arc-length arises from one end being pinned, and the other end being supported by a frictionless roller at a fixed distance from the pinned end. Using Lagrange’s equation of motion, the large amplitude free vibration equation of motion is derived based on the variational formulation. Included in the formulation are the energy dissipation due to large bending using the exact non-linear expression of curvature and the non-linearity arising from axial force. The non-linear eigenvalue problem is solved by the direct iteration method to obtain the beam’s non-linear frequencies and corresponding mode shapes for specified vibration amplitudes. We also present changes in the frequency of vibration as a function of amplitude, demonstrating the beam non-linearity. A more accurate solution analyzed in the frequency domain of the direct numerical integration method is adopted as an alternative solution. Large amplitude vibration experimental modal analysis was also conducted to complement the analytical results. The measured results were found to be in good agreement with those obtained from two analytical solutions.

Experimental and Computational Investigations of Creep Responses of Wood/PVC Composite Members

Abstract This article reported on finite element simulation to predict the creep responses of wood/poly (vinyl chloride) (WPVC) composite members before and after strengthening by using high carbon steel (HCS) flat bar strips bonded to the tension side of composite members. The short-term properties and creep characteristics, in accordance with power law models of WPVC composites and HCS flat bar materials, were determined individually by extensive experimental investigations. The experimental results indicated that strengthening of WPVC composites with HCS flat bar strips could increase the flexural and creep performances of the WPVC composite members both in flat-wise and edge-wise directions. The improvement in the edge-wise direction was relatively greater than that in the flat-wise direction, representing the loading direction dependence for this composite member. Abaqus finite element analysis (FEA) software was applied to predict the creep responses of WPVC composite members based on the characteristics of the individual component material; these results were then verified by the experimental results. Good correlations between FEA and experimental results were found in all cases, indicating that Abaqus software with the power law creep model can be used as an alternative tool for determining the creep responses of WPVC composites.

Effect of Nanosilica Particle Size on the Water Permeability, Abrasion Resistance, Drying Shrinkage, and Repair Work Properties of Cement Mortar Containing Nano-SiO2

This work presents the effect of nanosilica particle sizes on durability properties and repair work properties of cement mortar containing nanosilica (NS). Three different NS particle sizes of 12, 20, and 40 nm were used and compared with those of cement mortar without NS and cement mortar with silica fume (SF). Interesting results were obtained in which the particle size of NS affected directly the abrasion resistance and water permeability. NS with particle size of 40 nm is the optimum size and gave the highest abrasion resistance and water permeability. For repair work properties, cement mortars containing NS (12 and 20 nm) and SF experienced higher drying shrinkage than that of cement mortar without NS and then presented cracking behavior and debonding between the cement mortars and concrete substrate. Cement mortar containing 40 nm of NS gave the lowest drying shrinkage, the lowest crack number, and the highest adhesive strength. These results indicate that the particle size of NS affected not only the durability properties but also the repair work properties of cement mortar.

Finite Element Simulation for Creep Response of Strengthened Wood/PVC Composite

This paper investigates the finite element simulation to predict the creep response of Wood/PVC (WPVC) composite members before and after strengthening by using high carbon steel (HCS) flat bar strip adhered to the tension side. The creep parameters based on power law models of WPVC composites and the HCS flat bars were determined experimentally. Then, the nonlinear finite element analysis (FEA) software of ABAQUS was applied to predict the creep behaviors of composite members using the obtained experimentally creep parameters of individual component of WPVC composites and HCS flat bars. Good correlation between finite element simulation and experimental results are obtained for all cases. ABAQUS software with power law creep model show good potential for prediction the creep response of WPVC composites before and after strengthening.

Compressive load, thermal and acoustic properties of wood/polyvinyl chloride composite log-wall panels

The cross-section design of wood/polyvinyl chloride composite log-wall panels was studied for effects on compressive load, thermal and acoustic properties. Variation in the slenderness ratio (2, 4, 8, 10 and 12) on compressive load was also included. Two parameters of log-wall cross sections consisting of web thickness (3.5, 7.0 and 10.0 mm) and flange spacing (45, 60 and 90 mm) were also investigated. Experimental results indicated that higher web thickness and lower flange spacing of wood/polyvinyl chloride composite log-wall cross sections increased the ultimate compressive load and noise reduction. However, lateral deflection and thermal resistance decreased. Increasing the slenderness ratio of the log-wall panels resulted in lower ultimate compressive load and higher lateral deflection. Empirical equations for predicting the ultimate compressive load of wood/polyvinyl chloride composite log-wall panels in practical uses were proposed regarding web thickness, flange spacing and slenderness ratio.