This thesis investigates the performance of diamond-shaped dowel joints in concrete slabs on ground under static loads. Diamond-shaped dowels have been in common use in concrete slab construction since 1996. A comprehensive literature review revealed that published studies regarding laboratory tests and finite element modelling of diamond-shaped dowel performance were limited to primary experiments and simple numerical analysis. Importantly, the limited finite element modelling has not been verified against test data, and the scant published test data lacks clarity. The results were inconclusive, unclear and there exists different recommendations for joint stability. Some recommended design data are not based on any testing, but on inferred or extrapolated data from smaller slabs with smaller dowel thicknesses. Hence, this research provides the opportunity to enlighten the design community with real data on the performance of diamond-shaped dowel joint behaviour. The research program includes experimental, numerical modelling and parametric evaluations. In the experimental investigation, testing facilities were designed and developed in the course of this research. A total of one trial and six cast-in-place slabs encompassing two slab thicknesses, two diamond-shaped dowel thicknesses, and two dowel spacing, were tested in the structures laboratory of the Division of Civil Engineering at the University of Queensland. Joint gaps of 10 or 15 mm were used to simulate typical slab contraction causing by the shrinkage of concrete slabs. All tests were subjected to static loading to failure. This enabled slab joint response to be evaluated in terms of relative deflection, load transfer efficiency, load transfer, ultimate load and crack geometry. In addition to the experiments, numerical models were developed using the LUSAS finite element program. The model dimensions corresponded to those of the laboratory test specimens. The concrete slabs were modelled using a “multi-crack concrete model 94”. The test rig, diamond-shaped dowels and other materials were modelled as elastic materials. Results from the laboratory experiments were compared to the finite element results in order to validate the model. These models were then used to undertake a preliminary parametric study of diamond-shaped dowel performance. Criteria such as joint gap widths, dowel spacing, concrete property reduction, and dowel and slab thickness were investigated. The three main sections of this work - comprising laboratory testing, finite element modelling and parametric study evaluating have been combined to provide a betterinformed understanding of the performance of concrete slabs using diamond-shaped dowels.

A new three-dimensional finite solid element (3D FE) model for dowel-type wood connections was developed using the concept of a beam on a nonlinear wood foundation, which addresses the intricate wood crushing behaviour under the connector in a dowel type connection. In order to implement the concept of wood foundation with solid elements, a 3D FE wood foundation model was defined within a prescribed foundation zone surrounding the dowel. Based on anisotropic plasticity material theory, the material model for the foundation zone was developed using effective foundation material constants that were defined from dowel-embedment test data. New 3D FE single nail connection models were developed that incorporated the wood foundation model. The 3D wood foundation model was justified and validated using dowel-embedment test data with a range of dowel diameters, from a 2.5-mm nail to a 25.4-mm bolt. The connection models provided successful results in simulating the characteristics of load-slip behaviour that were experimentally observed. Based on the success of the single nail connection models, several applications of the 3D FE connection models were investigated including statistical wood material models, bolted connection models and a multiple nail connection model. Throughout the application studies, discussion of the benefits and limitations of the new model approach using the 3D FE wood foundation are presented. Also, future areas of study are proposed in order to improve the 3D FE dowel-type wood connections models.

A new three-dimensional finite solid element (3D FE) model for dowel-type wood connections was developed using the concept of a beam on a nonlinear wood foundation, which addresses the intricate wood crushing behaviour under the connector in a dowel type connection. In order to implement the concept of wood foundation with solid elements, a 3D FE wood foundation model was defined within a prescribed foundation zone surrounding the dowel. Based on anisotropic plasticity material theory, the material model for the foundation zone was developed using effective foundation material constants that were defined from dowel-embedment test data. New 3D FE single nail connection models were developed that incorporated the wood foundation model. The 3D wood foundation model was justified and validated using dowel-embedment test data with a range of dowel diameters, from a 2.5-mm nail to a 25.4-mm bolt. The connection models provided successful results in simulating the characteristics of load-slip behaviour that were experimentally observed. Based on the success of the single nail connection models, several applications of the 3D FE connection models were investigated including statistical wood material models, bolted connection models and a multiple nail connection model. Throughout the application studies, discussion of the benefits and limitations of the new model approach using the 3D FE wood foundation are presented. Also, future areas of study are proposed in order to improve the 3D FE dowel-type wood connections models.

A new three-dimensional finite solid element (3D FE) model for dowel-type wood connections was developed using the concept of a beam on a nonlinear wood foundation, which addresses the intricate wood crushing behaviour under the connector in a dowel type connection. In order to implement the concept of wood foundation with solid elements, a 3D FE wood foundation model was defined within a prescribed foundation zone surrounding the dowel. Based on anisotropic plasticity material theory, the material model for the foundation zone was developed using effective foundation material constants that were defined from dowel-embedment test data. New 3D FE single nail connection models were developed that incorporated the wood foundation model. The 3D wood foundation model was justified and validated using dowel-embedment test data with a range of dowel diameters, from a 2.5-mm nail to a 25.4-mm bolt. The connection models provided successful results in simulating the characteristics of load-slip behaviour that were experimentally observed. Based on the success of the single nail connection models, several applications of the 3D FE connection models were investigated including statistical wood material models, bolted connection models and a multiple nail connection model. Throughout the application studies, discussion of the benefits and limitations of the new model approach using the 3D FE wood foundation are presented. Also, future areas of study are proposed in order to improve the 3D FE dowel-type wood connections models. / Forestry, Faculty of / Graduate

After 333 years under depths of the Baltic Sea, the warship Vasa was salvaged and nowadayslies in a dry dock inside the Vasa Museum in Stockholm. Its current support system, which consists on eighteen cradle-stanchions pairs of steel, is not able to handle the present loads in a satisfactory manner. Experimental tests showed that the Vasa's hull is gradually deforming mainly due to creep behavior. Thus, in order to preserve the Vasa for future generations, a new support system has to be implemented in a foreseeable future. There are several factors to take into consideration for its construction, which are: the degradation of the oak, its current mechanical properties and its inhomogeneity in addition to the climatic conditions of the Museum and the impossibility of taking unlimited specimens for its analysis. Hence, it is crucial to investigate the areas where the stresses and deformations are critical in the ship and how affected is the stiffness of the hull, its most important component. In this dissertation work two Finite Element Analyses are accomplished. The first study consists on the creation of a superelement of a section of Vasa's hull with the intention of investigating the influence of the dowels on the stiffness of the hull. In the second analysis a simplied model of the entire warship Vasa is created in order to analyze it and locate possible critical areas on the hull due to its own weight and the stresses originated by the support system. The software selected for these simulations are Abaqus and CreoSimulate 2.0. From the first study it is concluded that that the dowels do not have a signicant influence in the stiffness coeffcients of the hull. The second analysis determines that the maximum stresses are located on the bottom part of the hull. This dissertation work concludes with a suggested future work.

The concept of a ready-to-assemble kit fabricated in a factory and delivered to the customer is well known and commonly used by the furniture industry. In wood construction, the lack of a simple and reliable method of assembling the frame members creates a barrier to wide acceptance of prefabricated kit structures. This thesis focuses on a novel technology of assembling structural components of a wood frame using a metal nail plate connector (NPC). This technology was referred to as a ready-to-assemble (RTA) wood framing system. The RTA system simplifies the framing process and allows for rapid erection of a wood structural frame by a small nonprofessional crew. A 16 x 24 foot RTA building was constructed to demonstrate the feasibility of the RTA system concept. An effective assembly sequence was proposed and successfully implemented. The design procedure for the RTA buildings was presented. The lateral load path for the RTA building includes diaphragms and shear walls. The contribution of the RTA frame can be ignored from the lateral load analysis. This conclusion was validated for the diaphragms with aspect ratios up to 4:1. The finite element method was used to model the RTA structures. The models incorporated semi-rigid behavior of the NPC. An analytical model was developed to predict the nonlinear moment-rotation relationship of the NPC. The proposed model showed a good agreement (R2=0.98) with the experimental data. Tests were conducted to measure the load-drift response of the RTA shear walls. / Master of Science

Ett sätt att öka mängden trä i byggnader är att ersätta stålförband i takstolar med ett trädymlingsförband. Det bör dock undersökas om trädymlingsförbandet har tillräckligt högt hållfasthetsvärde. Denna studie undersöker hållfastheten på träförband förankrade med trädymlingar. Dymlingarna har tre olika dimensioner (8, 10 och 12 mm) och förankras i förbanden genom svällning. Teoretiska beräkningar utförs med formler från Eurokod 5 (2004) för stålskruvar. Formlerna modifieras för att kunna tillämpas på trä istället för stål. Trycktester utförs på tio tvåplansskjuvnings-modeller per dymlingsdimension. Studien anses vara statistisk och sammanställs i normalfördelningskurvor. Av data från testerna räknas karakteristiska värden för trädymlingarna med säkerhetsmarginalen 95 %. Karakteristiskt hållfasthetsvärdet för trädymlingsförbanden blev 2100 N för 8 mm, 2300 Nför 10 mm och 4400 N för 12 mm. / One way to increase the amount of wood in buildings is to replace framing tie with timber dowel joints. It has to be investigated if timber dowel joints strength value is high enough. This study investigates the strength of timber joints anchored with a dowel. The dowels have three different dimensions and were anchored in the joint by swelling. Theoretical calculations were made with formulas from Eurokod 5 (2004) for steel screws. The formulas were modified to be applied to wood instead of steel. Pressure tests wereperformed on ten double shear models per dowel dimension. The tests are considered tobe statistically and compiled in a normal distribution curve. Characteristic strength with thesafety margin of 95 % was calculated from the data from the tests. Characteristic strength for the timber dowel joints were 2100 N for 8 mm, 2300 N for 10mm and 4400 N for 12 mm.

Dowel bars are provided at the transverse joints of the Jointed Plain Concrete Pavement (JPCP) to transfer the load between adjoining slabs and to allow for expansion and contraction of the pavement due to temperature and moisture changes. The current study involved evaluation of the performance of Glass Fibre Reinforced Polymer (GFRP) dowels in JPCP as an alternative to the conventional epoxy-coated steel dowel bars, especially in the presence of dowel misalignment. This research involved two main sets of experimental tests. The first set focused on the evaluation of load-deflection response of GFRP dowels using a scaled model of pavement slabs. The second set investigated the combined effect of dowel misalignment and cyclic wheel load on the performance of steel and GFRP dowels. The tested slabs (in the second set) were supported on a steel-beam base with stiffness such that the effects of the underlying layers of real pavements are incorporated. In both of these sets of experiment the GFRP dowels were compared with the steel dowels of similar flexural rigidity. The research also involved detailed numerical investigations using ABAQUS for all experimental tests in the current study. The validated numerical model was used to conduct three sets of parametric studies: to propose design considerations for the GFRP dowels; to simulate all important cases of dowel misalignment (111 cases) for steel and GFRP dowels and to give an insight into the damaged volume in the surrounding concrete pavement; and to investigate the effects of diameter, length and type of dowel bar, concrete grade, pavement thickness, and slab-base friction on the joint-opening behaviour. The results from the first set of experiments showed that the 38 mm GFRP dowels perform better in terms of deflection response compared to the 25 mm steel dowels. Also, it was observed that the relative deflection (RD) is more sensitive to the changes in the joint width rather than the concrete strength. The numerical results from the first set showed a good agreement with the experimental results and showed lower magnitude and better distribution of stress in the concrete underneath the GFRP dowels as compared with the steel dowels. Finally, on the basis of a detailed parametric study (70 different cases), design considerations for GFRP dowels in JPCP were suggested. The second set of experimental results showed that the GFRP dowels can withstand a cyclic traffic load and significantly reduce joint lockup and dowel looseness (DL) and can provide sufficient load transfer efficiency (LTE). It was also observed that the dowel misalignment affects DL significantly more than the repeated traffic load. Slab-base separation and the orientation of misaligned dowels have significant effects on the pull-out load required to open the joint. The numerical results from the second set indicated that the pull-out load was small for the vertical misalignment cases compared to the horizontal and combined misalignment cases. The results also indicated the occurrence of concrete spalling and deterioration at smaller joint openings for combined misalignment when compared to other misalignment types. The use of GFRP dowels significantly reduced the pull-out load and joint lockup when dowel misalignment exists. Consequently, the deterioration of the surrounding pavement substantially decreased. The long term performance of the JPCP fitted with GFRP dowels improves because of a reduction in the DL and the RD, and by maintaining a good LTE even for misaligned dowels. The numerical results also showed that the pull-out load increases significantly for an increase in the concrete compressive strength and the dowel bar diameter. Small increase in pull-out load was observed for higher embedded length of the dowel bar, whereas the increase was insignificant for an increase in the pavement thickness and slab-base friction. In general, the study showed the GFRP dowel can be a potential alternative for the conventional steel dowel bars in JPCP.

No description available.

Dowel bars in jointed plain concrete pavement (JPCP) have the important function of transferring wheel loads from one slab to the other, hence ensuring that the deflections on each side of the joint are kept almost equal. As well, the dowels should not impede the concrete pavement movements due to environmental effects (temperature and moisture). Dowel bar misalignment, attributed to deficient construction practice, is a major cause of joint distress or faulting by inhibiting the free movement of the slab at the joint. To prevent these issues, tolerance guidelines on misalignment levels are implemented by transportation agencies. Review of previous studies indicate that many researchers analysed the effects of dowel bar misalignment on pavement behaviour using a pull-out test, that is a forcebased opening of the joint. These approaches neglect that joints movements in the field are strain-governed by non-linear temperature and shrinkage actions, leading to combined axial movements and curling of the slab. In this study, the fundamental dowel bar behaviour under shrinkage and thermal loading was determined through detailed 3D finite element modelling (3D-FEM). To that end, models of dowel jointed concrete slabs were developed and subjected to realistic non-linear profiles of shrinkage and thermal strains. Studies were carried out on a single-bar model, taking into account bar-concrete friction and plastic concrete behaviour. The parameters that were investigated included different configurations and levels of bar misalignment and different friction coefficients between the steel and the concrete, simulating the use of bond-breakers. To interpret the results from the numerical analysis, criteria for concrete damage were developed and used in parallel with measures of joint load transfer efficiency; these were obtained by examining the response of the slab under a Falling Weight Deflectometer (FWD) drop at the joint. The results were verified by comparing the outputs of a model consisting of one half of a slab to published data. The analysis of the models revealead that none of the models showed signs of significant damage after the application of shrinkage and two thermal cycles. Analyses with up to ten thermal cycles did not indicate progressive accumulation of damage, suggesting that for the chosen parameters there is no the concrete around the dowel bar will not fail. Models with bars placed higher in the slab and bars with angular misalignment exhibited more damage than the non-misaligned models without reaching the damage criteria used in this study. The models did not exhibit the amount of damage reported in the studies on dowel bar misalignment having used pull-out tests. It was found that no significant difference existed between uncoated and coated dowel bars models results with regards to concrete damage at the joint. However, a high coefficient of friction between the dowel and the concrete, simulating dowel bar corrosion, proved to be the most detrimental to joint integrity. All of the models performed very well with respect to joint load transfer efficiency, suggesting that the plastic strains in the concrete around the dowel did not have a significant impact on joint performance for the realistic range of parameters investigated.