Cross-laminated timber (CLT) is an emerging engineered wood product in North America. Past research effort to establish the behaviour of CLT under extreme loading conditions has focussed CLT slabs with idealized simply-supported boundary conditions. Connections between the wall and the floor systems above and below are critical to fully describing the overall behaviour of CLT structures when subjected to blast loads. The current study investigates the effects of “realistic” boundary conditions on the behaviour of cross-laminated timber walls when subjected to simulated out-of-plane blast loads. The methodology followed in the current research consists of experimental and analytical components. The experimental component was conducted in the Blast Research Laboratory at the University of Ottawa, where shock waves were applied to the specimens. Configurations with seismic detailing were considered, in order to evaluate whether existing structures that have adequate capacities to resist high seismic loads would also be capable of resisting a blast load with reasonable damage. In addition, typical connections used in construction to resist gravity and lateral loads, as well as connections designed specifically to resist a given blast load were investigated. The results indicate that the detailing of the connections appears to significantly affect the behaviour of the CLT slab. Typical detailing for platform construction where long screws connect the floor slab to the wall in end grain performed poorly and experienced brittle failure through splitting in the perpendicular to grain direction in the CLT. Bearing type connections generally behaved well and yielding in the fasteners and/or angles brackets meant that a significant portion of the energy was dissipated there reducing the energy imparted on the CLT slab significantly. Hence less displacement and thereby damage was observed in the slab. The study also concluded that using simplified tools such as single-degree-of-freedom (SDOF) models together with current available material models for CLT is not sufficient to adequately describe the behaviour and estimate the damage. More testing and development of models with higher fidelity are required in order to develop robust tools for the design of CLT element subjected to blast loading.

The large ductile deformation response of stiffened plates subjected to blast loads is investigated and simplified methods of analysis of such response are developed. Simplification is derived from modelling stiffened plates as singly symmetric beams or as grillages thereof. These beams are further assumed to behave in a rigid, perfectly plastic manner and to have piecewise linear bending moment-axial force capacity interaction relations, otherwise known as yield curves. A blast loaded, one-way stiffened plate is modelled as a singly symmetric beam comprised of one stiffener and its tributary plating, and subjected to a uniformly distributed line load. For a stiffened plate having edges fully restrained against rotations and translations, both transverse and in-plane, use of the piecewise linear yield curve divides the response of the beam model into two distinct phases: an initial small displacement phase wherein the beam responds as a plastic hinge mechanism, and a final large displacement phase wherein the beam responds as a plastic string. If the line load is restricted to be a blast-type pulse, such response is governed by linear differential equations and so may be solved in closed form. Examples of a one-way stiffened plate subjected to various blast-type pulses demonstrate good agreement between the present rigid-plastic formulation and elastic-plastic beam finite element and finite strip solutions. The response of a one-way stiffened plate is alternatively analysed by approximating it as a sequence of instantaneous mode responses. An instantaneous mode is analogous to a normal mode of linear vibration, but because of system nonlinearity exists for only the instant and deformed configuration considered. The instantaneous mode shapes are determined by an extremum principle which maximizes the rate of change of the stiffened plate's kinetic energy. This approximate rigid-plastic response is not solved in closed form but rather by a semi-analytical time-stepping algorithm. Instantaneous mode solutions compare very well with the closed-form results. The instantaneous mode analysis is extended to the case of two-way stiffened plates, which are modelled by grillages of singly symmetric beams. For two examples of blast loaded two-way stiffened plates, instantaneous mode solutions are compared to results from super finite element analyses. In one of these examples the comparison between analyses is extremely good; in the other, although the magnitudes of displacement response differ between the analyses, the predicted durations and mechanisms of response are in agreement. Incomplete fixity of a stiffened plate's edges is accounted for in the beam and grillage models by way of rigid-plastic links connecting the beams to their rigid supports. Like the beams, these links are assumed to have piecewise linear yield curves, but with reduced bending moment and axial force capacities. The instantaneous mode solution is modified accordingly, and its results again compare well with those of beam finite element analyses. Modifications to the closed-form and instantaneous mode solutions to account for strain rate sensitivity of the panel material are presented. In the closed-form solution, such modification takes the form of an effective dynamic yield stress to be used throughout the rigid-plastic analysis. In the time-stepping instantaneous mode solution, a dynamic yield stress is calculated at each time step and used within that time step only. With these modifications in place, the responses of rate-sensitive one-way stiffened plates predicted by the present analyses once again compare well with finite element and finite strip solutions. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The scope of this study is to establish extensive material tests to determine the mechanical properties of cellular concrete and evaluate its potential as energy absorption material against air blast load. This study includes a literature review of existing studies on cellular concrete, proportioning, and its mechanical properties, together with studies on the properties and application of other foams such as aluminium and polymer foams. It is concluded that, unlike other foam materials, there is a lack of systematic studies on the mechanical properties of cellular concrete especially for densities less than 1000 kg/m3. The survey also reviewed the existence of materials being used as a sacrificial layer against air blast load, together with the analytical models proposed to determine the parameters required to design a cladding system. As a result it was found that cellular concrete can maintain most of the properties of the cladding materials and can be applied as a new sacrificial layer against the blast load. Extensive material tests are carried out to characterise the effect of ingredients and density on material properties of cellular concrete. Based on the experimental results, an empirical model is proposed which determines the plateau and densification regime of nominal stress-strain curve of the cellular concrete with different densities. The penetration resistance of cellular concrete with different densities under truncated, conical, flat and hemi-spherical solid indenters are studied experimental. By determining the deformation mechanism of cellular concrete under indentation with application of an X-Ray tomography image system, an analytical model is proposed to determine the resistance of cellular concrete under penetration of flat indenter. Experimental closed range blast tests are performed with 1kg and 3kg C4 explosive to determine the mitigation potential of cellular concrete against air blast load. Numerical modelling of the experimental blast test is carried out using Ansys LS-DYNA to evaluate the feasibility of the numerical modelling techniques to predict the response of cellular concrete against air blast load.

A two-dimensional constant heating rate thermoelastic model has been used to develop design and selection criteria for refractory components of linings of high-temperature furnaces and process vessels. The criteria are in the form of resistance to fracture initiation and resistance to damage parameters which account for the influence of thermal and mechanical properties, geometry, and temperature range, while distinguishing between the heating and cooling cases. The resistance to fracture initiation parameter ɸs is the maximum rate at which a shape can be heated or cooled through a specified temperature range without causing fracture. The damage resistance parameter Rd is expressed as the ratio of surface energy per unit area to the elastic strain energy available for crack propagation. Both parameters can be quickly estimated for arbitrary conditions with the aid of tabulated solutions for the maximum principal tensile stress and total strain energy Thermoelastic analyses were used to interpret published results of a variety of thermal shock experiments. Thermal conditions associated with water quenching, radiative furnace heating, gas burners, and controlled heating were simulated using appropriate analytical solutions. Finite element analysis was used to compute maximum principal tensile stresses and elastic strain energy. A simple procedure was developed to invert the stress solution and thereby determine the instant of fracture. Good agreement between thermoelastic predictions and published experimental results with regard to strength retained versus thermal shock relationships, location of fracture, and safe heating rates provided justification for a thermoelastic approach to the thermal shock. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

Retaining walls (RW) are among the most common geotechnical structures. They have been widely used in railways, bridges (e.g. bridges abutment), buildings, hydraulic and harbor engineering. Once built, the RW can be exposed to dynamic loads, such as those produced by earthquakes, machines, vehicles and explosions. They must remain operational in aftermath of the natural or human-induced dynamic events. Hence, the understanding of the geotechnical response of RW to these dynamic loads is critical for the safe design of several civil engineering structures such as railways, highways, bridges, and buildings. Although fairly reliable methods have been developed for assessing and predicting the response of RW to dynamic loads induced by earthquakes, there is very little information to guide engineers in the design of RW that are exposed to surface explosions (surface blast loadings). These methods for assessing RW response to earthquake loads cannot directly be applied to the design of RW subjected to surface blast loads. Indeed, blast loads are short duration dynamic loads and their durations are very much shorter than those of earthquakes. The predominant frequencies of a blast wave are usually 2-3 orders of magnitudes higher than those of earthquake wave, and the same can be said for blast wave acceleration as compared to the peak acceleration that results from an earthquake. Thus, RW response under blast loading could be significantly different from that under a loading with much longer duration such as an earthquake. There is a need to increase our understanding of the response of RW to surface explosion loadings since there is a significant increase of terrorist threat on important buildings and some lifeline infrastructures. Transportation structures (bridges, highway, and railway) are unquestionably being regarded as potential targets for terrorist attacks. The purpose of this PhD research is to investigate the geotechnical response of reinforced concrete retaining wall (RCRW) with sand as a backfill material to surface blast loads. The soil-RW model was subjected to a simulated blast load using a shock tube. The influence of the backfill relative density, backfill saturation, blast load intensity, and live load surcharge on the behaviour of RCRW with sand backfill was studied. The dimensions of the stem and heel of the retaining wall in this study were 650 mm (height) x 500 mm (width) x 60 mm (thickness) and 400 mm (width) x 500 mm (length) x 60 mm (thickness), respectively. Soil-RW model was placed inside a wooden box. The overall height of the box was 1565 mm. The retained backfill extended behind the wall for 1300 mm. Based on the results, it is found that the maximum dynamic earth pressures were recorded at a time greater than the positive phase duration regardless of the backfill condition. The total earth pressure distribution along the height of the wall showed that the magnitude of total earth pressure for loose and medium backfill at the mid-height of the wall slightly exceeded the dense backfill. In addition, the lateral earth pressures increased with the increase in the blast load intensities. On the other hand, under the same load conditions, an increase in the wall movement was noticed in loose backfill, and a translation response mode was evident in this condition. The mobilized passive resistance of the RW backfill induced by blast load was used to determine the force-displacement relationship. Finally, the susceptibility of the RW with saturated dense sand to liquefaction was examined, and it was ascertained that liquefaction was not triggered when the RW was subjected to a blast load of 50 kPa. The results and findings of this PhD research will provide valuable information that can be used to evaluate the vulnerability of transportation structures to surface blast events as well as to develop guidance for their design.

Recent terrorist attacks on critical infrastructures using car bombs have heightened awareness on the needs for blast resistance of structures. Blast design of civilian buildings has not been a common practice in structural design. For this reason, there is now an urgent need to mitigate the potentially devastating effects of blast shock waves on existing structures. The current research project, the results of which are reported in this dissertation, aims to expand knowledge on blast resistance of reinforced concrete building columns, while developing a technology and design procedure for protecting critical buildings columns against the damaging effects of impulsive blast loads through the use of externally applied fibre-reinforced polymer (FRP) jackets of different material architecture. The research project has a significant experimental component, with analytical verifications. A total of thirty two reinforced concrete columns were experimentally investigated under the effects of simulated blast loads using the University of Ottawa Shock Tube. Column dimensions were 150 mm x 150 mm in cross section and 2438 mm in length. Each concrete column was reinforced longitudinally with four 10M rebars which were tied laterally with 6.3 mm closed steel hoops, spaced at 37.5 mm and 100 mm c/c, representing seismic and non-seismic column details, respectively. The experimental research had two phases. Phase-I (sub-study) included blast tests of eight as-built, seismically detailed columns. The behaviour of these columns was explored under single and multiple blast shots, with and without the application of pre-blast axial loads. Phase-II (main-study) included column tests of different carbon FRP (CFRP) designs to investigate the significance of the use of different CFRP column jacket designs on dynamic response of twenty four seismic and non-seismic RC columns. Analytical investigation was conducted to assess and verify the significance of experimentally investigated parameters on column response. These included the use of Single-Degree-of-Freedom (SDOF) dynamic inelastic analysis, generation of dynamic resistance functions, the effects of variable axial loads, different plastic hinge lengths and the influence of secondary moments (P- moments) on column behaviour. The results indicate that the loading history has effects on column response, with multiple shots reducing column stiffness, and affecting dynamic response of columns relative to single blast shots of equivalent magnitude. The effect of concrete strength within the normal-strength concrete range is to increase strength and decrease deformations. Columns with CFRP jackets have considerable improvements in column deformability, with additional increases in column strength. The CFRP laminate design influences performance, with jackets having fibres in ±45o orientation especially improving column ductility and increasing plastic hinge lengths, thereby permitting redistribution of stresses and dissipating blast energy. Axial gravity loads vary during blast loads and can affect column strength. It was shown that SDOF dynamic inelastic analysis does capture key structural performance parameters in blast analysis. The consideration of experimentally observed parameters in column analysis; including the influence of CFRP design and associated change in plastic hinge length, variable axial load during response, and secondary moment (P- moments) result in significant improvements in the accuracy of blast analysis. The experimental results and the suggested improvements to the SDOF analysis technique can be used to implement a performance-based design approach recommended as part of the current research project for design of CFRP protection systems for concrete columns.This research project was conducted jointly by the National Research Council Canada (NRC) and the University of Ottawa.

A common view in today’s society is that natural background conditions is found just prior to the start of the industrialization. By employing this view in environmental work, it neglects the human impact attributed to historical site-specific activities such as metallurgy. These activities have been widespread throughout Sweden, reaching far back into history. It is therefore necessary to determine the site-specific background conditions in order to assess the impact these activities have had. This study investigates the start of the blast furnace Alntorpshyttan in Bergslagen by conducting geochemical analyzes using sediment profiles in Norasjön as a natural archive. This was coupled with an indirect dating method based on the immigration spruce (Picea abies) and the historical atmospheric lead (Pb) pollution. The earliest sign of human activities takes place at 1800 BP, possibly due to farming activities. Based on the increases in iron coupled with increases in other ore-related elements (e.g., Magnesium and copper) I placed the start of Alntorpshyttan in the early/late 13th century. This is consistent with the rapid expansion of blast furnaces throughout Bergslagen. Based on these results, I conclude that historical small-scale metallurgical activities have had a significant impact on local lake systems and potentially a cumulative effect further downstream.

Indiana University-Purdue University Indianapolis (IUPUI) / Analysis of explosives (intact and post-blast) is of interest to the forensic science community to qualitatively identify the explosive(s) in an improvised explosive device (IED). This requires high sensitivity, selectivity, and specificity. Forensic science laboratories typically utilize visual/microscopic exams, spectroscopic analysis (e.g., Fourier Transform Infrared Spectroscopy (FTIR)) and gas chromatography/mass spectrometry (GC/MS) for explosive analysis/identification. However, GC/MS has limitations for explosive analysis due to difficulty differentiating between structural isomers (e.g., 2,4-dinitrotoluene, 2,5-dinitrotoluene and 2,6- dinitrotoluene) and thermally labile compounds (e.g., ethylene glycol dinitrate (EGDN), nitroglycerine (NG) and pentaerythritol tetranitrate (PETN)) due to mass spectra with very similar fragmentation patterns. The development of a benchtop vacuum ultraviolet spectrometer coupled to a gas chromatography (GC/VUV) was developed in 2014 with a wavelength region of 120 nm to 430 nm. GC/VUV can overcome limitations in differentiating explosive compounds that produces similar mass spectra. This work encompasses analysis of explosive compounds via GC/VUV to establish the sensitivity, selectivity, and specificity for the potential application for forensic explosive analysis. Nitrate ester and nitramine explosive compounds thermally decompose in the VUV flow cell resulting in higher specificity due to fine structure in the VUV spectra. These fine structures originate as vibronic and Rydberg transitions in the small decomposition compounds (nitric oxide, carbon monoxide, formaldehyde, water, and oxygen) and were analyzed computationally. The thermal decomposition process was further investigated for the determination of decomposition temperatures for the nitrate ester and nitramine compounds which range between 244 oC and 277 oC. Nitrated compounds were extensively investigated to understand the absorption characteristics of the nitro functional group in the VUV region. The nitro absorption maximum appeared over a wide range (170 - 270 nm) with the wavelength and intensity being highly dependent upon the structure of the rest of the molecule. Finally, the GC/VUV system was optimized for post-blast debris analysis. Parameters optimized include the final temperature of a ramped multimode inlet program (200 oC), GC carrier gas flow rate (1.9 mL/min), and VUV make-up gas pressure (0.00 psi). The transfer line/flow cell temperature was determined not to be statistically significant.

This thesis examines the influences of five factors on the strain energy at failure of metallic alloy plates during a shock wave impact. The five factors are material type, initial damage, boundary conditions, plate thickness, and plate temperature. The finite element simulation matrix was developed using a statistical design of experiments (DOE) technique. The Eulerian hydrocode CTH was used to develop the pressure histories that were input into the finite element code Abaqus/Explicit, which implemented the Mississippi State University internal state variable (ISV) plasticity-damage model (DMG). The DMG model is based on the Bammann-Chiesa-Johnson (BCJ) ISV plasticity formulation with the addition of porosity and the void nucleation, growth, and coalescence rate equations that admit heterogeneous microstructures. Material type and thickness were the primary influences on the strain energy at failure, and the materials studied, magnesium and aluminum, showed two different failure mechanisms, tearing at the boundaries and spalling, respectively.

Detonation of an explosive charge, such as a mine or an improvised explosive device (IED) at the ground surface or buried at shallow depth in soil, can produce high airblast pressures and significant dynamic soil debris loads on an overlying or nearby structure, such as a vehicle passing over the explosive. The blast loading environment is a function of many factors including the explosive type, configuration, mass, and depth of burial, soil characteristics, and the distance between the ground surface and the structure or object. During the past several years, the US Army has focused considerable attention on developing improved methods for predicting this environment, particularly for use by vehicle/armor analysts, thereby, improving the survivability of these platforms. Research is needed to better understand the aboveground environment created by the detonation of a shallow-buried explosive in order to design adequate protective measures for an aboveground structure. Unfortunately, there is no accurate methodology for predicting these airblast and soil debris loads to support the designs. Development of the required prediction tools is hampered by lack of well controlled and documented experimental results for these complex loads. Without detailed experimental data, the numerical simulations of these loads cannot be adequately validated for the large deformation, stress, and motion gradients and the resulting interactions with structures. The focus of this research is to quantify the influence of soil properties on the aboveground environment from the detonation of a bare explosive charge resting on the soil surface or shallow-buried. In order to fully quantify the influence of soil parameters, well-controlled experiments were designed to directly measure soil debris and airblast loadings on an aboveground reaction structure due to the detonation of explosives at the surface of and shallow buried in three very different soils. The experiments were performed using specifications and strict quality controls that limited the influence of outside variables and ensured the experiments were repeatable. The experiments provided blast pressure, soil stress, and impulse data for each soil type. These data were analyzed to investigate the influence of the properties of the different soil types on the aboveground environment.