This thesis explores two hybrid systems employing a core material reinforced by an external skin, namely, cladding walls composed of polyurethane foam core sandwiched between fibre-reinforced polymer (FRP) skins, and beams composed of concrete-filled FRP or steel tubes. The walls were studied in two phases. In phase I, the polyurethane foam core was injected between two carbon-FRP (CFRP) skins. Ten panels were tested to investigate their structural performance and failure modes. Test parameters included quality control in terms of reproducibility of test results, moment-shear ratio, and the orientation of an architectural masonry-like coating. The study showed that design is governed by stiffness and not strength and that the CFRP was underutilized. Also, quality control was shown to be poor for this method of fabrication. As such, in phase II, ten panels were fabricated by laminating glass-FRP (GFRP) skins to prefabricated polyurethane foam blocks. Similar flexural testing was carried out to investigate two different densities of foam, and moment-shear ratio. The study showed evidence of high quality control and that the density of the foam core significantly affected flexural capacity and stiffness. Rectangular concrete-filled tubes (CFTs), with either steel or pultruded GFRP tubes were fabricated and tested as beams in three-point bending, at different shear span-to-depth (a/d) ratios of 1 to 5 to examine crack patterns, strength and failure modes. It was shown that the critical (a/d) ratio, at which moment capacity drops, is between 4 and 5 for CFTs with GFRP tubes and between 1 and 2 for CFTs with steel tubes. It was also shown that ductility is drastically reduced at (a/d) ratios below 3 for steel tubes. Crack pattern and size were highly dependent on the magnitude of slip between the concrete and tube. A major full depth flexural crack developed in all CFTs with GFRP tubes. However, when internal steel rebar was added, major diagonal cracks were formed in addition to fine flexural cracks. In CFTs with steel tubes, fine flexural cracks developed, except at a/d = 1, where fine diagonal cracks were predominant. A strut-and-tie model was developed and provided reasonable agreement with test results. / Thesis (Master, Civil Engineering) -- Queen's University, 2008-12-23 12:25:09.685

Concrete-Insulation-Concrete Sandwich Panels with Glass Fibre Reinforced Polymer (GFRP) shear connectors can be a solution to increasing energy efficiency in building envelopes, while also providing many architectural, structural, and economic benefits for building designs. This study consists of extensive experimental investigation of the shear and thermal properties of a unique sandwich panel design, incorporating GFRP shear connectors and a concrete “stud” system. The goal of this study is to expand upon the knowledge of alternative connectors’ effect on structural and thermal properties of sandwich panels, and to develop a thermally, structurally, and economically efficient panel. In the structural phase fifty 254x254x900 mm specimens representing segments of the precast sandwich wall, comprising two concrete wythes and a concrete stud surrounded by insulation foam, were tested in a double shear configuration. Three types of GFRP connectors produced from available sand-coated and threaded rods were tested and compared to conventional steel and polymeric connectors. GFRP connector diameters varied from 6 to 13 mm, and spacing varied from 80 to 300 mm. Both circular and rectangular cross-sections were examined, along with various end treatments to compare with simple straight embedment. The shear strength of GFRP connectors ranged from 60 to 112 MPa, significantly higher than polymeric connectors but lower than steel connectors. As the connectors bridged a small gap of insulation between the concrete wythe and stud, their shear strength was lower than manufacturer reported values due to the presence of some bending. Varying the size, spacing, cross-section shape or end treatment of connectors had insignificant effect on their strength. The connectors failed by longitudinal delamination then transverse shear, but did not pull out of the concrete wythe. Adhesion bond between concrete and insulation was significant and contributed about 28% of resistance, but was too variable for use in design. In the thermal testing phase, ten 254x1550x2400 full-scale specimens were tested in a purpose-built hot box apparatus under steady-state conditions. GFRP connectors showed minimal thermal bridging regardless of cross-section area or spacing, while steel connectors demonstrated significant thermal bridging in recorded temperatures despite a smaller cross-section area, and were clearly visible in thermal imaging. / Thesis (Master, Civil Engineering) -- Queen's University, 2014-05-06 13:32:38.896

A reliability-based optimization (RBO) methodology was developed and applied to fiber-reinforced polymer (FRP) bridge decks. Commercially available software was used to optimize a FRP bridge deck panel by weight with structural reliability, stress, and deflection constraints. A methodology using optimization software, finite element analysis, and probabilistic analysis software was developed to examine the effects of load and resistance uncertainties in FRP bridge deck optimization. Eight modular deck designs were considered for use in the RBO methodology. Investigations into random variable sensitivities, design variable sensitivities, wheel positions, and buckling were conducted to minimize computational effort. Five models were eventually optimized with deterministic methods and the RBO methodology. Ply thicknesses were treated as design variables. Material parameters, design variables, and load were taken as random variables in the reliability calculations. A comparison of RBO designs was made with the best candidate chosen based on deck panel weight.

Axxor is one the main leader in paper honeycomb production by supplying automotive, furniture, and door manufacturers. Paper honeycomb material holds the lead over any existing cores in performance, price and density ratio. The main drawback of PHC products is its lack of water/fire resistance which reduces significantly its scope of applications. Consequently, the Axxor company intends to perform a new type of product which could withstand a water exposition: impregnated paper honeycomb. By coating the paper honeycomb cellulose fibers, the mechanical properties are significantly improved with three times higher compressive strength compared to PHC. Two impregnated resins have been selected for a potential large scale production: Epoxy and Polyurethane resins. The totality of IPHC is produced through two processes which are a manual impregnation performed by hand or a continuous impregnation performed by an impregnation machine. With these independent variables in mind, this study concerns the degree of water resistance by comparing three IPHC samples: - Epoxy IPHC performed with handmade impregnation - Polyurethane IPHC performed with handmade impregnation - Polyurethane IPHC performed with the impregnation machine (higher resin content) By using the available characterization devices, water resistance is defined by measuring the decreases of the mechanical performances depending on the remaining water content in each samples.

Honeycomb sandwich panels, formed by bonding a core of honeycomb between two thin face sheets, are in wide use in aerospace, automotive and marine applications due to their well-known excellent density-specific properties. There are many technological methods of damping vibrations, including the use of inherently lossy materials such as viscoelastic materials, viscous and friction damping and smart materials such as piezoelectrics. Some have been applied to damping of vibrations, in particular to sandwich panel and honeycomb structures, including viscoelastic inserts in the cell voids. Complete filling of the cell with foam, viscoelastic or particulate fillers have all been demonstrated to improve damping loss in honeycombs. However, the use of an additional damping material inside the core of a sandwich panel increases its mass, which is often deleterious and may also lead to a significant change in dynamic properties. The work presented in this thesis explores the competing demands of vibration damping and minimum additional mass in the case of secondary inserts in honeycomb-like structures. The problem was tackled by initially characterising the main local deformation mechanism of a unit cell within a sandwich panel subjected to vibration. Out-of-plane bending deformation of the honeycomb unit cell was shown to be the predominant mode of deformation for most of the honeycomb cells within a sandwich panel. The out-of-plane bending deformation of the honeycomb cells results in relatively high in-plane deformation of the cells close to the skins of the sandwich panels. It was also highlighted that the magnitude and loading of the honeycomb unit cell are dependent on its location within the honeycomb or sandwich panel and the mode shape of the panel. An optimisation study was carried out on diverse honeycomb unit cell geometries to find locations at which the relative displacement between the honeycomb cell walls of the void is maximal under in-plane loadings. These locations were shown to be dependant of the nature of the loading, i.e. in-plane tension/compression or in-plane shear loading of the honeycomb unit cell and the unit cell geometry. Analytical expressions and finite element analyses were used to investigate the partial filling of the honeycomb unit cell with a damping material, in this case a viscoelastic elastomer, in the target locations identified previously where the relative displacement between the honeycomb cell walls is maximal. Damping inserts in the form of ligaments partially filling the honeycomb cell void have shown to increase the density-specific loss modulus by 26% compared to cells completely filled with damping material for in-plane tension/compression loading. The form of the damping insert itself was then analysed for enhancement of the dissipation provided by the damping material. The shear lap joint (SLJ) damping insert placed in the location where the relative displacement between the honeycomb cell walls of the void is maximal under in-plane loadings was characterised with very significant damping improvements compared to honeycomb cells completely filled with viscoelastic material. A case study of a cantilever honeycomb sandwich panel with embedded SLJ damping inserts demonstrated their efficiency in enhancing the loss factor of the structure for minimum added mass and marginal variation of the first modal frequency of the structure. Partial filling of the cells of the honeycomb core was shown to be the most efficient at increasing damping on a density basis.

Master of Science / Department of Architectural Engineering and Construction Science / Kimberly Waggle Kramer / Insulated precast concrete sandwich panels are commonly used for exterior cladding on a building. In recent years, insulated tilt-up concrete sandwich panels are being used for the exterior load-bearing walls on a building. The insulation is sandwiched between exterior and interior concrete layers to reduce the heating and cooling costs for the structure. The panels can be designed as composite, partially composite, or non-composite. The shear ties are used to achieve these varying degrees of composite action between the concrete layers. A parametric study analyzing the standard, solid single-wythe tilt-up concrete wall panel and solid sandwich (double-wythe separated by rigid insulation) tilt-up concrete wall panels subjected to eccentric axial loads and out-of-plane seismic loads is presented. The sandwich tilt-up panel is divided into two categories – non-composite and composite wall panels. The height and width of the different types of tilt-up wall panel is 23 feet (21 feet plus 2-foot parapet) and 16 feet, respectively. The solid standard panel (non-sandwich) is 5.5 inches in thickness; the non-composite sandwich panel is composed of 3.5-inch architectural wythe, 2.5-inch rigid insulation, and 5.5-inch interior load bearing concrete wythe; and the composite sandwich panel is composed of 3.5-inch exterior, load bearing concrete wythe, 2.5-inch insulation, and 5.5-inch interior, load bearing concrete wythe. The procedure used to design the tilt-up wall panels is the Alternative Method for Out-of-Plane Slender Wall Analysis per Section 11.8 of ACI 318-14 Building Code Requirements for Structural Concrete and Commentary. The results indicated that for the given panels, the applied ultimate moment and design moment strength is the greatest for the composite sandwich tilt-up concrete panel. The standard tilt-up concrete panel exhibits the greatest service load deflection. The non-composite sandwich tilt-up concrete panel induced the greatest vertical stress. Additionally, the additional requirements regarding forming materials, casting, and crane capacity is covered in this report. Lastly, the energy efficiency due to the heat loss and heat gain of sandwich panels is briefly discussed in this report. The sandwich tilt-up panels exhibit greater energy efficiency than standard tilt-up panels with or without insulation.

Blast risk associated with terrorist threats and accidental explosions has become an international concern over the past decade and has provoked structural engineers to implement protective design measures. Recent advances in this area of research has seen tremendous improvements in mitigating this risk through the installation of retrofits, advanced structural design, or pre-emptive protective measures. Tilt-up and precast panel walls are constructed using a unique approach in which the walls are cast horizontally and lifted, or tilted, into their final vertical position. These unique structures are cost effective, energy efficient, and can be rapidly constructed. This approach is commonly applied to the construction of large industrial facilities and the construction of schools which are categorized as high importance structures in the National Building Code of Canada. These panels are inherently flexible and have a surplus of mass making them desirable for protective design applications, however their behaviour under blast induced loads is not well defined. This experimental research project investigates the behaviour of non-composite tilt-up sandwich (NCTS) panels and solid reinforced concrete (SRC) panels with realistic support conditions subjected to blast-induced shockwaves. Previous research shows that NCTS panels, identifiable by their large structural wythe, exhibit some degree of composite behaviour and require between 5% to 10% composite action for successful erection. Five scaled specimens were constructed following common procedures used in practice, equipped with identical data acquisition instruments, and tested at the University of Ottawa shock tube testing facility under similar blast pressure-impulse combinations. Test results for the NCTS and SRC panels are compared graphically in terms of displacement–time histories and sectional strain distributions. The data is evaluated to approximate the composite behaviour at mid-span of the NCTS panel. Analytical results generated, using “RC Blast,” single-degree-of-freedom analysis software developed at the University of Ottawa, were validated with empirical data and are presented graphically. Each specimen was equipped with connections similar to those commonly used in the construction of NCTS panels. These connections were experimentally studied under simulated blast pressures and analysed using CSA A23.3-04 guidelines for punching shear capacity. Modified support iii | P a g e reinforcement layouts and surface bonded FRP laminates were evaluated as strengthening and retrofit techniques to prevent support failure. Dynamic support reactions and predicted support resistances are tabulated for each shot of every panel. The results indicate that it is possible to accurately predict the flexural behaviour and support resistance of a NCTS panel using RC Blast and CSA A23.3-04 guidelines. Several factors considered in this analysis include boundary conditions, dynamic material properties, and shear tie degradation. This analysis of flexural behaviour is highly dependent on shear stiffness, which is directly related to the composite action within NCTS panels. Support resistance was increased significantly through application of the strengthening techniques outlined in this thesis.

No description available.

No description available.

Cellular core structures are the state-of-the-art technology for light weight structures in the aerospace industry. In an aerospace product, sandwich panels with cellular core represent the primary structural component as a given aerospace product may contain a large number of sandwich panels. This reveals the necessity of understanding the mechanical behavior of the cellular core and the impact of that behavior on the overall structural behavior of the sandwich panel, and hence the final aerospace product. As the final aerospace product must go through multiple qualification tests to achieve a final structure that is capable of withstanding all environments possible, analyzing the structure prior to testing is very important to avoid any possible failures and to ensure that the final design is indeed capable of withstanding the loads. To date, due to the lack of full understanding of the mechanical behavior of cellular cores and hence the sandwich panels, there still remains a significant lack of analytical capability to predict the proper behavior of the final product and failures may still occur even with significant effort spent on pre-test analyses. Analyzing cellular core to calculate the equivalent material properties of this type of structure is the only way to properly design the core for sandwich enhanced stiffness to weight ratio of the sandwich panels. A detailed literature review is first conducted to access the current state of development of this research area based on experiment and analysis. Then, one of the recently developed homogenization schemes is chosen to investigate the mechanical behavior of heavy, non-corrugated square cellular core with a potential application in marine structures. The mechanical behavior of the square cellular core is then calculated by applying the displacement approach to a representative unit cell finite element model. The mechanical behavior is then incorporated into sandwich panel finite element model and in an in-house code to test the predicted mechanical properties by comparing the center-of-panel displacement from all analyses to that of a highly detailed model. The research is then expanded to cover three cellular core shapes, hexagonal cores made of corrugated sheets, square cores made of corrugated sheets, and triangular cores. The expansion covers five different cell sizes and twenty one different core densities for each of the core shapes considering light cellular cores for space applications, for a total of 315 detailed studies. The accuracy of the calculated properties for all three core shapes is checked against highly detailed finite element models of sandwich panels. Formulas are then developed to calculate the mechanical properties of the three shapes of cellular cores studied for any core density and any of the five cell sizes. An error analysis is then performed to understand the quality of the predicted equivalent properties considering the panel size to cell size ratio as well as the facesheet thickness to core thickness ratio. The research finally expanded to understand the effect of buckling of the unit cell on the equivalent mechanical property of the cellular core. This part of the research is meant to address the impact of the local buckling that may occur due to impact of any type during the manufacturing, handling or assembly of the sandwich panels. The variation of the equivalent mechanical properties with the increase in transverse compression load, until the first folding of the unit cell is complete, is calculated for each of the three core shapes under investigation. / Ph. D.