No description available.

<p>In safety-related nuclear structures, steel-plate composite (SC) walls are often used in combination with reinforced concrete (RC) walls or foundations. The design demands need to be transferred between the two different structural systems through appropriate connections without connection failure, which is often associated with brittle failure mode. This study presents a design procedure developed for mechanical connections between SC and RC walls. This procedure implements the full-strength connection design approach as per Specifications for Safety-Related Steel Structures for Nuclear Facilities, AISC N690-18, which requires connections to be stronger than the weaker of the connected walls. The study also presents the results from experimental and numerical investigations conducted to verify the structural performance of the full-strength SC wall-to-RC wall mechanical connection.</p> <p>The experimental program involved testing six mechanical connections comprising four full-scale and two scaled specimens. The four specimens subjected to out-of-plane moment (OOPM) and out-of-plane shear (OOPV) represented a unit cell of a typical wall in a nuclear facility. The remaining two specimens subjected to in-plane shear (IPV) were scaled (1:3) to facilitate testing using the existing loading setup. Two specimens were tested for each loading scenario. The two specimens per loading case were differentiated by longitudinal rebar-to-baseplate connection plans: coupler (C) and double nut (DN). The performance, strength, ductility, and failure mode of the proposed mechanical connection were evaluated based on the experimental observations.</p> <p>The observed governing failure mode of all test specimens was either RC wall flexural yielding or RC wall shear failure. The connection region steel plates (tie plates, wing plates, and baseplates) remained within their elastic range until failure ensuring energy dissipation away from the connection region. Additionally, the wing plates and baseplates strains remained comparatively lower than the tie plate strain values. This was attributed to the contribution of concrete during the force transfer between the two structural elements indicating that the proposed connection design procedure is suitable and conservative for SC wall-to-RC wall mechanical connections.</p> <p>Three-dimensional (3D) finite element models (FEM) were developed and benchmarked against the experimental data to gain an additional insight into the connection behavior. Parametric studies were conducted to compensate for the limited experimental database and evaluate the influence of design parameters such as wall thickness and RC wall longitudinal reinforcement layers on the performance of the designed mechanical connection. Numerically predicted results compared favorably with experimental observations. The recommended design procedure is intended to help designers consider mechanically connecting SC-RC walls where non-contact lap splicing is not feasible and in an attempt to utilize the potential for accelerated construction time and enhanced structural performance of SC walls.</p> <p><br></p>

The performance of thin-plate structural systems is known to be greatly influenced by the effect of buckling and post-buckling behaviour. The main factors, which affect the buckling, and post-bucking characteristics and consequently the ultimate performance of thin plate structural components, are noted to be structural geometry, material properties, loading and boundary conditions and geometric imperfections. Present day knowledge and understanding of the buckling and post-buckling behaviour of thin plate structures is at a fairly sophisticated level due to the intensive research that has been carried out over the years in this field of study. This is particularly true for the case of compressive loading whereby the collapse and unloading failure mechanics of thin plate structures has been well documented for this case. The same is not true for the case of shear loading and although much work has been carried out there is a lack of knowledge and in-depth understanding of shear post-ultimate conditions which essentially defines the initiation and progressive development of the plastic failure mechanisms of thin plate structural system. This thesis makes a contribution to the area of study by taking advantage of the developments in recent years of computational technology and computing power to develop finite element modelling strategies and solution procedures using the commercially available FE package PATRAN/NASTRAN to describe in detail the post-buckled shear failure of thin plate structural systems. The work of this thesis provides an in-depth understanding of the complex post-buckled failure mechanics associated with thin-plate structures subjected to in-plane shear displacement and combined shear and compression loading. Simply supported in-plane normal stress free and straight edge boundaries are employed to examine the shear performance as well as the failure mechanisms of thin and stocky web plates. Finite element modelling strategies are developed, which are able to describe the complete loading history from the onset of initial buckling through the nonlinear elastic post-buckling to initial material yielding and its further propagation throughout the structure leading to the development of an appropriate failure mechanism that causes final plastic collapse and subsequent load drop-off. The post-buckled failure response of the thin plate structures is determined with due consideration being given to the effects of geometric and material nonlinearities. The effect of stiffeners on structural performance is detailed for single and multiple asymmetrical and symmetrically attached stiffeners. The degrading influence on the structural performance of cut-outs as well as the considerable redeeming effect due to reinforcements attached at the cut-out boundaries is highlighted in this thesis. The work of the thesis covers the in-plane shear displacement loading of thin web plates, thin web plates with transverse stiffeners, web plates with cut-outs, web plates with stiffened cut-outs and the interactive shear and compressive loading of transversely stiffened web structures. The in-plane shear displacement loading of these structures using the multipoint constraint loading strategy in the finite element modelling procedures has shown to be highly successful in being able to provide an in-depth understanding of the failure mechanics of these structures to a level not to be found in the existing literature.

Technical textiles are increasingly being engineered and used in challenging applications, in areas such as safety, biomedical devices, architecture and others, where they must meet stringent demands including excellent and predictable load bearing capabilities. They also form the bases for one of the most widespread group of composite materials, fibre reinforced polymer-matrix composites (PMCs), which comprise materials made of stiff and strong fibres generally available in textile form and selected for their structural potential, combined with a polymer matrix that gives parts their shape. Manufacturing processes for PMCs and technical textiles, as well as parts and advanced textile structures must be engineered, ideally through simulation, and therefore diverse properties of the textiles, textile reinforcements and PMC materials must be available for predictive simulation. Knowing the detailed geometry of technical textiles is essential to predicting accurately the processing and performance properties of textiles and PMC parts. In turn, the geometry taken by a textile or a reinforcement textile is linked in an intricate manner to its constitutive behaviour. This thesis proposes, investigates and validates a general numerical tool for the integrated and comprehensive analysis of textile geometry and constitutive behaviour as required toward engineering applications featuring technical textiles and textile reinforcements. The tool shall be general with regards to the textiles modelled and the loading cases applied. Specifically, the work aims at fulfilling the following objectives: 1) developing and implementing dedicated simulation software for modelling textiles subjected to various load cases; 2) providing, through simulation, geometric descriptions for different textiles subjected to different load cases namely compaction, relaxation and shear; 3) predicting the constitutive behaviour of the textiles undergoing said load cases; 4) identifying parameters affecting the textile geometry and constitutive behaviour under evolving loading; 5) validating simulation results with experimental trials; and 6) demonstrating the applicability of the simulation procedure to textile reinforcements featuring large numbers of small fibres as used in PMCs. As a starting point, the effects of reinforcement configuration on the in-plane permeability of textile reinforcements, through-thickness thermal conductivity of PMCs and in-plane stiffness of unidirectional and bidirectional PMCs were quantified systematically and correlated with specific geometric parameters. Variability was quantified for each property at a constant fibre volume fraction. It was observed that variability differed strongly between properties; as such, the simulated behaviour can be related to variability levels seen in experimental measurements. The effects of the geometry of textile reinforcements on the aforementioned processing and performance properties of the textiles and PMCs made from these textiles was demonstrated and validated, but only for simple cases as thorough and credible geometric models were not available at the onset of this work. Outcomes of this work were published in a peer-reviewed journal [101]. Through this thesis it was demonstrated that predicting changes in textile geometry prior and during loading is feasible using the proposed particle-based modelling method. The particle-based modelling method relies on discrete mechanics and offers an alternative to more traditional methods based on continuum mechanics. Specifically it alleviates issues caused by large strains and management of intricate, evolving contact present in finite element simulations. The particle-based modelling method enables credible, intricate modelling of the geometry of textiles at the mesoscopic scale as well as faithful mechanical modelling under load. Changes to textile geometry and configuration due to the normal compaction pressure, stress relaxation, in-plane shear and other types of loads were successfully predicted. During simulation, particles were moved randomly until a stable state of minimum strain energy in the system was reached; as particles moved upon iteration, the configuration of fibres in the textile changed under constant boundary conditions. Then boundary conditions were altered corresponding to strains imposed on the textile, and the system was iterated again towards a new state of minimum strain energy. The Metropolis algorithm of the Monte Carlo method was adopted in this specific implementation. The method relies on a statistical approach implemented in computational algorithms. In addition to geometrical modelling, the proposed particle-based modelling method enables the prediction of major elements of the constitutive behaviour of textiles and textile reinforcements. In fact, prediction of the constitutive behaviour is integral to the prediction of the meso-scale geometry. Simulation results obtained from the proposed particle-based modelling method were validated experimentally for yarns, single-layer textiles and multi-layer textiles undergoing compaction. Validation work showed that the particle-based modelling method replicates reality very faithfully, and it also showed the suitability of including Gutowski's function along with Hertz' function for representing lateral compaction of yarns. The procedure and results were accepted in final form for publication in a peer reviewed journal [104]. The capability of the proposed particle-based modelling method towards replicating the time-dependent relaxation and reconfiguration of woven textiles subjected to compaction loading was investigated. The capability, which was demonstrated for single and double-layers of plain woven textiles, is intrinsic to the modelling method. The method is unique in the fact that in contrary to work previously reported in the literature, it models the compaction and the relaxation seamlessly in the same simulations and environment. This work is being finalised towards submission for publication in a peer reviewed journal [103]. The proposed particle-based modelling method was also used for modelling in-plane shear in woven textiles. Simulation results were validated experimentally for a single-layer plain woven textile. Validation work showed that the particle-based modelling method reproduces experimental data and published trends very well. A novel algorithm for modelling friction was introduced, leading to results being obtained from a significantly less computationally demanding procedure in these simulations. This work was submitted for publication in a peer reviewed journal [102]. Finally the thesis discusses early work towards the application of the method to carbon fibre fabrics through the description of expansion algorithm (EA) to be used in modelling textiles made of yarns featuring very large numbers of fibres. Furthermore, additional modelling work is presented towards further manufacturing process involving technical textiles, namely textile bending and punching. The latter part is presented as early steps towards future work.

Aerospace structural components made from polymer matrix composites (PMCs) offer numerous advantages. Their high stiffness and high strength combined with low densities enable lower fuel consumption coupled with higher payloads. As a result, PMCs provide an important economic advantage over typical metallic airframes. Textile reinforcements for PMCs are made by assembling reinforcement fibres, typically carbon. Then, the textile reinforcements are typically cut into smaller pieces, stacked, draped and assembled into a dry assembly called a preform, the shape of which generally approaches that of the PMC part to be made. This manufacturing process is labour intensive and expensive. Novel thick, net-shape, drapable, high vf textile reinforcements used toward manufacturing aerospace PMCs are being developed at the University of Ottawa. The technology enables the manufacturing of flat, drapable multilayered near net-shape preforms. The bending and in-plane shear behaviours of such novel thick reinforcement textiles was investigated to understand and define the behaviour of such thick fabric reinforcements when formed into required shapes. A bending apparatus was developed for investigating the bending behaviour of these novel thick reinforcement fabrics and an articulated frame shear rig was used for investigating the in-plane shear behaviour. A non-destructive inspection method using infrared imaging was used for investigating and identifying flaws and defects in these thick, dry textile reinforcements, aiming at increasing the quality and reproducibility of the final PMC parts made from these reinforcements.

Technical textiles are increasingly being engineered and used in challenging applications, in areas such as safety, biomedical devices, architecture and others, where they must meet stringent demands including excellent and predictable load bearing capabilities. They also form the bases for one of the most widespread group of composite materials, fibre reinforced polymer-matrix composites (PMCs), which comprise materials made of stiff and strong fibres generally available in textile form and selected for their structural potential, combined with a polymer matrix that gives parts their shape. Manufacturing processes for PMCs and technical textiles, as well as parts and advanced textile structures must be engineered, ideally through simulation, and therefore diverse properties of the textiles, textile reinforcements and PMC materials must be available for predictive simulation. Knowing the detailed geometry of technical textiles is essential to predicting accurately the processing and performance properties of textiles and PMC parts. In turn, the geometry taken by a textile or a reinforcement textile is linked in an intricate manner to its constitutive behaviour. This thesis proposes, investigates and validates a general numerical tool for the integrated and comprehensive analysis of textile geometry and constitutive behaviour as required toward engineering applications featuring technical textiles and textile reinforcements. The tool shall be general with regards to the textiles modelled and the loading cases applied. Specifically, the work aims at fulfilling the following objectives: 1) developing and implementing dedicated simulation software for modelling textiles subjected to various load cases; 2) providing, through simulation, geometric descriptions for different textiles subjected to different load cases namely compaction, relaxation and shear; 3) predicting the constitutive behaviour of the textiles undergoing said load cases; 4) identifying parameters affecting the textile geometry and constitutive behaviour under evolving loading; 5) validating simulation results with experimental trials; and 6) demonstrating the applicability of the simulation procedure to textile reinforcements featuring large numbers of small fibres as used in PMCs. As a starting point, the effects of reinforcement configuration on the in-plane permeability of textile reinforcements, through-thickness thermal conductivity of PMCs and in-plane stiffness of unidirectional and bidirectional PMCs were quantified systematically and correlated with specific geometric parameters. Variability was quantified for each property at a constant fibre volume fraction. It was observed that variability differed strongly between properties; as such, the simulated behaviour can be related to variability levels seen in experimental measurements. The effects of the geometry of textile reinforcements on the aforementioned processing and performance properties of the textiles and PMCs made from these textiles was demonstrated and validated, but only for simple cases as thorough and credible geometric models were not available at the onset of this work. Outcomes of this work were published in a peer-reviewed journal [101]. Through this thesis it was demonstrated that predicting changes in textile geometry prior and during loading is feasible using the proposed particle-based modelling method. The particle-based modelling method relies on discrete mechanics and offers an alternative to more traditional methods based on continuum mechanics. Specifically it alleviates issues caused by large strains and management of intricate, evolving contact present in finite element simulations. The particle-based modelling method enables credible, intricate modelling of the geometry of textiles at the mesoscopic scale as well as faithful mechanical modelling under load. Changes to textile geometry and configuration due to the normal compaction pressure, stress relaxation, in-plane shear and other types of loads were successfully predicted. During simulation, particles were moved randomly until a stable state of minimum strain energy in the system was reached; as particles moved upon iteration, the configuration of fibres in the textile changed under constant boundary conditions. Then boundary conditions were altered corresponding to strains imposed on the textile, and the system was iterated again towards a new state of minimum strain energy. The Metropolis algorithm of the Monte Carlo method was adopted in this specific implementation. The method relies on a statistical approach implemented in computational algorithms. In addition to geometrical modelling, the proposed particle-based modelling method enables the prediction of major elements of the constitutive behaviour of textiles and textile reinforcements. In fact, prediction of the constitutive behaviour is integral to the prediction of the meso-scale geometry. Simulation results obtained from the proposed particle-based modelling method were validated experimentally for yarns, single-layer textiles and multi-layer textiles undergoing compaction. Validation work showed that the particle-based modelling method replicates reality very faithfully, and it also showed the suitability of including Gutowski's function along with Hertz' function for representing lateral compaction of yarns. The procedure and results were accepted in final form for publication in a peer reviewed journal [104]. The capability of the proposed particle-based modelling method towards replicating the time-dependent relaxation and reconfiguration of woven textiles subjected to compaction loading was investigated. The capability, which was demonstrated for single and double-layers of plain woven textiles, is intrinsic to the modelling method. The method is unique in the fact that in contrary to work previously reported in the literature, it models the compaction and the relaxation seamlessly in the same simulations and environment. This work is being finalised towards submission for publication in a peer reviewed journal [103]. The proposed particle-based modelling method was also used for modelling in-plane shear in woven textiles. Simulation results were validated experimentally for a single-layer plain woven textile. Validation work showed that the particle-based modelling method reproduces experimental data and published trends very well. A novel algorithm for modelling friction was introduced, leading to results being obtained from a significantly less computationally demanding procedure in these simulations. This work was submitted for publication in a peer reviewed journal [102]. Finally the thesis discusses early work towards the application of the method to carbon fibre fabrics through the description of expansion algorithm (EA) to be used in modelling textiles made of yarns featuring very large numbers of fibres. Furthermore, additional modelling work is presented towards further manufacturing process involving technical textiles, namely textile bending and punching. The latter part is presented as early steps towards future work.

No description available.

This thesis investigates the in-plane shear performance of full-scale walls made from compressed earth blocks. Compressed earth blocks are a type of masonry where the blocks are composed of compressed soil and typically dry-stacked without mortar. Prior research has demonstrated that the in-plane shear strength of these blocks falls far short of capacities predicted by conventional masonry building codes, requiring new testing to develop effective and safe designs for seismic conditions. This thesis specifically studies the effects of block type and the use of grouted shear keys at the block head joints. Three full-scale walls were constructed and tested under in-plane, cyclic loading. To compare the effect of block type on shear strength, one wall was constructed from Rhino blocks as used by the Center for Vocational Building Technology, while another used V-Lock blocks designed by the Vermeer Corporation. Apart from differences in size and interlock mechanism, the standard Rhino blocks have shear keys at the head joints which are not present on the V-Lock blocks. To examine the effect of these shear keys, a third wall was built from Rhino blocks with the shear keys removed. The two standard block types displayed no major difference in strength that could not be attributed to grouted area or the presence/absence of the head joint shear keys. The Rhino block wall with shear keys reached a higher peak load relative to the grouted area but experienced a brittle drop in capacity after peaking, while the other two walls exhibited an extended loading plateau after the initial peak. All walls failed with cracking and block sliding along the main diagonals, a failure mode similar to conventional masonry. Proposals are made for modifying the equations for shear capacity from the Masonry Standards Joint Committee (MSJC) 2013 code for use in designing compressed earth block shear walls.

This thesis investigates full-scale pipe stem reinforced cob walls under in-plane cyclic shear loads. Cob is the combination of clay subsoils, sand, straw and water that is built in lifts to produce monolithic walls. There is insufficient amount of information on cob as a building material in today’s age. The prior research that exists has examined varying straw content and type, water content, and mixture ratios to determine their effect on strength. There is currently one report that analyzes full-scale cob walls under in-plane loading. This thesis looks to iterate the full-scale tests and specifically studies the effect of reinforcement on cob walls. Concurrent to this research, another thesis was written that investigates a full-scale wire mesh reinforced cob wall under in-plane cyclic shear loads. From the data collected, a shear failure was suggested for the stem pipe wall. There appeared to be a large amount of ductility from the data and the cracks formed. Ductility, a seismic response modification factor (R-Factor) and stiffness were calculated using the yield point and ultimate loads.Iterations of this research and those performed in the past can be helpful in integrating cob in to the California Building Code.

No description available.