Rohana Hassan

Dowel-Bearing Strength Properties of Two Tropical Hardwoods

Bearing strength of wood is one of the properties that are use to estimate the lateral connection of wood design strength based on the European Yield Model (EYM), National Design Specification [NDS 2005 in National design specification for wood construction american forest and paper association (AFPA), Washington D.C, 2005] theory. This study investigated the characterisation of load to grain directions and two dowel sizes in two high-density Malaysian hardwood species; Kempas (koompassia Malaccensis) and Kapur (Dryobalanop spp.). Experimental work as stipulated in ASTM 5764-9a [American Standard Testing Method (ASTM) D 5764-95a in ), Standard test method for evaluating dowel-bearing strength of wood and wood-based products, 2007] was adopted. Result shows that according to the species, the lower strength group of species attributes to higher bearing strength of wood. It was also found that the bearing strength of parallel to the grain is higher than the perpendicular to the grain. In terms of dowel diameter, the bearing strength perpendicular and parallel to the grain decreased slightly as the dowel diameter increased regardless of the timber species. The EYM equations were found viable and sufficient in predicting the dowel-bearing strength of bigger dowel diameter for Kempas but not for the smaller dowel diameter. Contradict to Kempas species; the EYM equations were viable for the smaller dowel diameter and not for the bigger dowel diameter for Kapur. Thus, in the case of the insufficient predictions, three modified equations based on EYM, were proposed according to the specific gravity, density, species, dowel diameter and loading directions respectively.

Shear capacity of dowelled mortise and tenon in tropical timber

The European Yield Models (EYM) concept has been applied to observe an experimental study of single-dowelled mortise and tenon. Specimens consisting of structural size mortise and tenon dowelled with 20.6 mm diameter were axially loaded in shear. Test variables are the material for the dowels namely steel; glass fibre reinforced plastic (GFRP) and wood. Connections were tested until failure to observe the ultimate capacities and possible modes of failure as the variables were changed. Results show that the shear strength capacity of the mortise and tenon connection single-dowelled with steel, GFRP and wood is not directly reflected the capacity of the dowel. The proportional limit, 5% diameter offset and maximum strength of the connection are in the order of steel, wood and GFRP but the dowel yield modes are in the order of steel, GFRP and wood. Failure modes of GFRP were found as stiff as steel (mode Im) compared to wood (mode IIIs).

Computational Approach for Timber and Composite Material Connection Using Particle Swarm Optimization

Timber and composite material connection are currently a popular combination in construction industry. Although composite timber connection has been studied previously, it was based on traditional experimental laboratory work, which led to a higher cost and more time consuming. Therefore, this paper studies the tensile load carrying capacity of the composite connections by using Particle Swarm Optimization (PSO) which has the capability of finding optimal solutions. From the results, it can be concluded that even though the PSO fitness functions has not exactly matched the brittle behavior of the load-displacement response for both single and double shear connections, their overall tensile performance and capacity of the connections are well predicted. Therefore, the findings from this research will be benefited by timber engineers in predicting the timber composite connections behavior and capacity, particularly single and double shear connections.

Particle Swarm Optimization for Single Shear Timber Joint Simulation

This paper presents a new paradigm that is possible to aid the traditional experimental analysis in timber joints research. Laboratory experiment has incurred a lot of cost and times to find optimize end distance of a timber joint. Particle swarm optimization (PSO) is applied and tested focusing on a single shear timber joints. The determination of fitness function is based on the findings from the previous datasets of the traditional laboratory experiments. The dataset includes the timber species of Kapur that emphasizes on 2D and 3.5D in diameter of end distance. Several PSO parameters were tested to find the maximum load carrying capacity of timber joint for different end distances. The findings show that PSO can give a feasible solution for a single shear strength timber joint performance. It demonstrates that the PSO has a potential to be used as a timber joint simulations that would be beneficial to timber joint researchers in predicting the load carrying capacity of a joint and contributes in reducing time and cost.

Finite Element Model of Mortise and Tenon Joint Fastened with Wood Dowel Using Kempas Species

Finite element method (FEM) was used to model the behavior of mortise and tenon joint with wood dowel subjected to pull-out loads. The stress-state in the dowel was observed and the type of failure was indentified according to European Yield Model (EYM). The experimental results from Rohana [6] were used to validate a three-dimensional finite element model of mortise and tenon joint. In this study, linear-elastic orthotropic material was adopted to represent the Kempas wood behavior in FEM. The analysis was conducted by introducing tensile loads on the top of tenon to see the behavior of the dowel. The EYM mode of failures and load–displacement curves were then being compared between FEM results and experimental results obtained by Rohana [6].

Experimental performance of mortice and tenon joint strengthened with glass fibre reinforced polymer under tensile load

This paper reported on the experimental performance of mortise and tenon joint for beam-to-column structural member made of Kempas species. The joints were dowelled with glass fibre reinforced polymer (GFRP) and compared to the joints strengthened with steel dowel and wood dowel. The failure modes performance analyses were observed based on European Yield Model (EYM) theory according to National Design Specification (NDS) 2008. Results show that the experimental performance of the mortise and tenon joints dowelled with GFRP under tensile load may provide comparable strength to the joints dowelled with steel. The sequence of having the higher capacity to hold the mortise and tenon joints is by strengthening it using GFRP, followed by steel and wood dowel. The failure behavior of both joints dowelled with steel or GFRP were almost similar. Nevertheless, different behavior was shown in wood dowelled joints, the flexibility of wood dowels extended the displacement longer made the yield load and load at rapture extended compared to the other types of joints.

Evaluation of Dowel-Bearing Strength for Wood Dowel Using ‘Spring Theory’

Dowel-bearing strength of wood base material is one of the important parameter to design the load carrying capacity of a timber joint. The information about the dowel-bearing strength using steel is available in National Design Standard (NDS, National Design Specification for Wood Construction Ameican Forest and Paper Association (AFPA) Washington DC, 2005). However none of these standards include dowel-bearing strength compressed using wood dowel. Very limited studies were published in determining the dowel-bearing strength of wood base material compressed with wood dowel. The ‘Spring Theory’ proposed by Schmidt and Daniels (Design Considerations for Mortise and Tenon Connections. Report for Timber Framers Guild. Becket. MA, 1999) was found reliable to be applied for European timber species. However, the capability of this theory in determining the dowel-bearing strength of wood based compressed with wood dowel has not be investigated for tropical timber. Therefore this study is aimed to investigate the capability of the ‘Spring Theory’ for 12.7 mm wood dowel. ‘Spring Theory’ is about the combination result of wood dowel compressed with steel block (WDCSB) and wood block compressed with the steel dowel (WBCSD). It was found that ‘Spring Theory’ value of Kempas is 34.81 Mpa. The value of the proportional, 5 % offset and maximum load of Kempas is 11.74, 18.12 and 50.64 kN respectively. The ‘Spring Theory’ was found capable and valid in determining the wood dowel of Kempas compressed with 12.7 mm wood dowel.

Shear strength of steel and CFRP to timber interface

Adhesives can be used to form load-bearing joints in timber structures, both in repair and in new-build applications. An efficient and cost-effective method of making joints is to use rods or dowels or plate, bonded into pre-drilled holes in timber elements, by using structural adhesive for transferring structural loads between such elements. An adhesive is expected to hold materials together and transfer design loads from one adherend to other within a given service environment for the life of the structure. The behavior of the joints depends on many parameters such as glue-line thickness, types of rods, types of adherends etc. This paper reports the behavior of bonded-in joint by varying the plate types (steel and carbon fiber reinforced plastic (CFRP) plates) and timber types (Keruing and Kempas). To characterize the performance of the bonded-in joints, a series of test were conducted such as pull-out test and block shear test. As the strength properties of the joint greatly affected by the adhesive, the mechanical properties of the adhesives were also determined by conducting flexural and tensile test. The results show that the shear strength of bonded-in joint using CFRP plate is higher than bonded-in joint using steel plate.

Effect of Different Diameter of Glulam Dowel-Bearing Strength Made of Mengkulang Species

Timber is one of the construction materials to construct sustainable construction. Mengkulang species are one of the timber that widely used nowadays. It is suitable for flooring, interior finishing, furniture and paneling. In order to improve the ability of timber as structural components, its value is added through innovation in timber engineering such as glulam. Dowel-bearing strength is the maximum load capacity that the specimen or structural component can cater. In this study, the load bearing test was conducted using universal testing machine (UTM). The physical properties such as moisture content, density and specific gravity also had been determined. The dowel-bearing strength of 16 mm bolt diameter for Fe 5% and Fe max is 0.018 and 0.02 kN/mm2, respectively. For 20 mm bolt diameter, average value of Fe 5% and Fe max are 0.015 and 0.018 kN/mm2, respectively. From the result, it can be concluded that the smaller the bolt diameter, the higher the dowel-bearing strength. The record of bearing strength for Mengkulang species is not yet available. Therefore, this study can help in order to enhance the understanding of load bearing strength of this species.

Particle Swarm Optimization Application for Timber Connection with Glass Fiber-Reinforced Polymer (GFRP) and Non-GFRP

Timber connection is one of the important aspects that need to be evaluated in construction and manufacturing. The end product produced from these sectors depends on the strength of the timber connection especially in building constructions. A lot of laboratory experiments to measure the strength of timber connection were done before proceeding with the transformation process of a product. However, these experiments require high cost and time-consuming. In addressing these issues, there is an alternative mean that can be applied to predict the strength of timber connection to overcome those problems. This paper addresses on the employment of particle swarm optimization (PSO) in a simulated timber connection for tensile test with and without glass fiber-reinforced polymer (GFRP). Data from laboratory experiment of tensile test of tropical timber were used. The PSO potentially can adapt the behavior of the timber and predict the maximum weight that can be supported by the timber connection. The findings are acceptable which obtained 99.39 % accuracy for GFRP joints and 95.34 % accuracy for non-GFRP joint. By using population size of 20, it has shown that PSO provides good results and has capability to predict the timber joint strength. Results show that by combining the glass fiber-reinforced polymer (GFRP) sheet, the timber joint gives better strength than timber joint without GFRP. Thus, the outcome of PSO application would encourage the engineer or related construction fields to predict the timber joint strength with various fiber-reinforced polymer or other composite material.