No abstract

Compressive strength of cross-laminated timber (CLT) is one of the important mechanical properties which should be considered especially in design of midrise CLT building because it works to resist a vertical bearing load from the upper storeys. The CLT panel can be manufactured in various combinations of the grade and dimension of lamina. This leads to the fact that an experimental approach to evaluate the strength of CLT would be expensive and time-demanding. In this paper, lamina property-based models for predicting the compressive strength of CLT panel was studied. A Monte Carlo simulation was applied for the model prediction. A set of experimental compression tests on CLT panel (short column) was conducted to validate the model and it shows good results. Using this model, the influence of the lamina's width on the CLT compressive strength was investigated. It reveals that the CLT compressive strength increases with the increase in the number of lamina. It was thought that repetitive member effect (or dispersion effect) is applicable for the CLT panel, which was explained by the decrease of the variation in strength. This dependency of the number of lamina needs further study in development of reference design values, CLT wall design and CLT manufacturing.

A method for the shape control of double-plate structures is presented. The model consists of three plates and many ribs. Two of the plates are placed parallel to each other and clamped at one edge. The third plate connects the edges of the parallel plates that are opposite the fixed edge. Each rib is made of shape memory alloy (SMA) wire and connected to the parallel plates. Each rib generates a concentrated force and applies it to the plates in perpendicular and oblique directions. Piezoceramic patches are bonded onto the plates and exert concentrated moments upon the plates at several locations. The object of this research is to generate various structural shapes by combining the concentrated forces from the SMA wires and moments from the piezoceramic patches. The possibility of shape control is examined by finite element analysis. Numerical results show the capability of shape control by SMA wires and piezoceramics in the elastic range. Experimental results on shape control are presented to compare with the numerical results.

One of the unique features of photovoltaic (PV) modules is the power drop that occurs as the silicon temperature increases due to the characteristics of the crystalline silicon used in a solar cell. To overcome this reduction in power, module surface cooling using water circulation was employed. The model performance was then conceptually evaluated and experimentally verified. A transient model was developed using energy balances and heat and mass transfer relationships from various other sources to simulate the surface cooling system. The measurements were in good agreement with the model predictions. The maximum deviation between the measured and predicted water and silicon temperature differed by less than 4 °C. The maximum power enhancement in response to the cooling was 11.6% when compared with a control module. The surface cooling system also washed the module surface via water circulation, which resulted in an additional power up of the PV module in response to removal of the particles that interfere with solar radiation from the surface of the PV module. Accordingly, the cooling system could reduce maintenance costs and prevent accidents associated with cleaning. In addition, the increase in cooling water temperature can serve as a heat source. The system developed here can be applied to existing photovoltaic power generation facilities without any difficulties as well.

No abstract

No abstract

The aim of this study was to predict the withdrawal resistance of a screw in hybrid cross-laminated timber (CLT) composed of two types of lamina layers. A theoretical model to predict the withdrawal resistance was developed from the shear mechanism between a screw and the layers in hybrid CLT. The parameters for the developed model were the withdrawal stiffness and strength that occurs when a screw is withdrawn, and the penetration depth of a screw in layers of a wood material. The prediction model was validated with an experimental test. Screws with two different diameters and lengths (Ø6.5 × 65 mm and Ø8.0 × 100 mm) were inserted in a panel composed of solid wood and plywood layers, and the withdrawal resistances of the screws were evaluated. At least 30 specimens for each group were tested to derive the lower 5th percentile values. As a result, the developed model predictions were 86–88% of the lower 5th percentile values of hybrid CLT from the properties of the lamina layer. This shows that the withdrawal resistance of hybrid CLT can be designed from the properties of its layer.

This study established a prediction model for bending properties of glued-laminated timber (glulam) using optimized knot and modulus of elasticity (MOE) distributions of lumber laminate as the main input variables. For this purpose, knot and MOE data were investigated for all pieces of lumber that were prepared for glulam manufacturing, and statistical distributions of knot size, knot number in one lumber, and MOE of each laminate were optimized as distribution functions. These knot and MOE data were used as input variables in the prediction model for bending properties, and were also used in generating virtual glulam using the inverse transform method. Prediction of bending properties for glulam was carried out using the transformed section method, which is partially provided in ASTM D 3737 (Annex A4). Predicted values were compared with those from full-scale four-point bending tests for 60 sixlayered glulams with 10 different laminar combinations. Finally, the allowable bending properties of glulam for each specific laminate combination were determined by calculating the fifth percentile of the modulus of rupture and the average modulus of elasticity from virtual test results of more than 1000 virtual glulams. From the results of this study, predicted bending properties for glulam and their distributions could be used for structural design in both allowable stress design and limit state design.