Thesis (Ph. D.)--University of Wisconsin--Madison, 1984. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographies.

Thesis (M.C.E.)--University of Delaware, 2007. / Principal faculty advisor: Jennifer Righman McConnell, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

The aim of this research project is to investigate, experimentally and analytically, the effects of reinforcement corrosion on the flexural, shear and blast behaviours of reinforced concrete beams. As part of the experimental study, twenty-four beams reinforced were tested under quasi-static and simulated blast loads using the University of Ottawa Shock tube. All beams had dimensions of 125 mm x 250 mm x 2400 mm and were tested under four-point bending. Tension reinforcement consisted of either 2 – 10M (ρ= 1%) or 2 – 15M bars (ρ= 1.6%) for the flexure dominant specimens, and 2 – 25 M bars (ρ= 4%) for the shear-dominant specimens. In all cases, transverse reinforcement consisted of 6 mm stirrups spaced at s = 100 mm (d/2) throughout the beam span. Eighteen of the specimens were subjected to an accelerated corrosion process to induce different amount of mass loss in the longitudinal and transverse steel reinforcement. The test variables included: the type of corrosion (i.e. on the longitudinal or transverse reinforcement), the amount of corrosion (i.e. % mass loss in the steel reinforcement) and the extent / location of corrosion on the tension steel reinforcement (i.e. over the full length, middle span or end spans). The results from the experimental tests showed that corrosion of the tension and transverse steel reinforcement decreased the strength and ductility of the reinforced concrete beams under static loading, ultimately changing the failure mode. Similarly, the results from the blast tests showed that corrosion of the longitudinal and transverse reinforcement affected maximum displacements and support rotations, reduced blast capacity, increased damage and fragmentation, and ultimately changed the failure process from ductile to brittle. Results under both static and blast loads were sensitive to the amount and extent/location of the corrosion. As part of the analytical study, the static results were predicted using 2D finite nonlinear element (FE) modelling. The effects of corrosion were considered using several modeling features including: reduction in steel bar cross-sectional area, modification of the steel stress-strain response, and introducing corrosion-induced cracking using applied pre-strains. The predicted results from the FE simulations were to provide acceptable predictions in terms of load capacity and failure mode when compared to the experimental static test results. The blast results were predicted using two approaches, including: 1) single-degree of freedom (SDOF) analysis (with the resistance functions developed using FE modelling); and 2) the blast analysis capabilities of FE software VecTor2. Overall both approaches led to acceptable predictions of maximum mid-span displacements when compared to the experiments.

With recent improvement in wood manufacturing technologies, taller and larger wooden structures are being constructed, thereby increasing the risk for potential damage due to a blast threat against such structures. Recent studies on the effects of high strain rate in wood have been undertaken, however the vast majority of these studies have focussed on structural elements with idealized boundary conditions. Some studies included realistic connections as the boundary conditions, but little progress has been made to date in order to quantify the behaviour of connections in isolation. The current study aims to investigate the response of steel-wood-steel bolted connections when subjected to blast loads. This includes determining the dynamic increase in resistance and stiffness for stocky and slender bolts in both the parallel and perpendicular to grain directions. The study also explores analytical solutions to predict the joint behaviour and discusses the validity of current blast design provisions. Bolted wood connections were investigated under both static and simulated blast loading using the University of Ottawa’s shock tube. The study found a dynamic increase in resistance and stiffness when the failure mode was dominated by wood crushing in both the parallel and perpendicular to grain directions. No increase in resistance or stiffness was observed when bolt yielding dominated the failure. A loss of ductility was observed under dynamic loading for the parallel to the grain connections designed to fail in wood crushing. It was found that the use of self-tapping screw reinforcement was an effective method of preventing premature splitting failures and enhancing the performance of a connection. The results showed that connections which engaged the fastener in bending exhibited more favourable behaviour than connections which engaged only in wood crushing. A two degree-of-freedom model was capable of modelling the connections even when the support frame system had some flexibility. The validated model was used to investigate cases where the connection could contribute to the energy dissipation. It was found that the performance of the assembly improved when the connections were considered. Recommended future work includes an investigation of brittle failure modes in bolted connections, exploring connections with more deformation capacities, and expanding the experimental component of the study to include full-scale structural assemblies with wood elements and boundary connections. Limited design recommendations have been proposed in the current study, however testing at the assembly level could shed more light on such an important topic.

Glass facade/curtain wall assemblies are commonly used in modern building construction as part of building envelop. This system has a number of advantages, including pleasant architectural appearance, building energy optimization, acceptable fire resistance and low maintenance. However, they pose tremendous risk towards maliciously intended acts of terror in the form of bomb blasts. The literature review conducted revealed lack of previous research on mullion strengthening/hardening. The present study has the objective of developing hardening techniques for curtain wall mullions to withstand high-intensity impulsive blast loads. Combined experimental and analytical research was conducted for the development of mullion retrofit techniques using the Shock Tube Facility of the University of Ottawa. The test program involved retrofitting existing, commercially used aluminum mullions with steel plates and subjecting them to different levels of blast loads. The mullions were retrofitted with three techniques with the help of steel L shaped angles, steel plates and with a combination of steel HSS sections and plates. The results indicated an increase of load carrying capacity of the mullions up to a factor of 2.2 with up to 30% reduction in mid-height displacements. It was shown that the steel hardening components developed full composite action with the existing aluminum section, indicating the effectiveness of the hardening technology. The analytical research followed the experimental research with the main objective of validating experimental results, as well as validating the assumption of full composite action between the core aluminum mullion and the hardening plates. The first step was to develop resistance functions followed by the validation of main analytical tool RC-Blast and the UFC charted solution. Following excellent agreement between these two analytical tools, RC-Blast was further validated against the experimental results. In addition, Pressure-impulse (P-I) diagrams were developed as design aids for different pressure-impulse combinations. The retrofit techniques developed were applied to a selected prototype building to assess their feasibility for use in practice. Two different blast threats were considered for this application. Conclusions were drawn regarding the effectiveness of the curtain wall hardening techniques for use in practice.

In presplit blasting operations airborne energy called air blast overpressure or impulsive sound is produced. The air blast induced by blasting may vary significantly at or around an open pit mine depending on several parameters such as the amount of charge detonated, the physical distance between the blast and the monitoring locations and the weather conditions. Therefore evaluation and assessment of noise condition at or around an open pit mine is necessary. The objective of this research study is to monitor and record the noise and to investigate and assess the noise conditions that will be induced from presplit blasting operations at Kisladag Gold Mine. In this research study, several parameters such as the amount of charge, the physical distance to the location of monitoring device or residential structures and the weather condition parameters such as wind direction, wind speed were recorded, analyzed and evaluated. It is observed that with increasing charge per delay air overpressure increases, whereas with increasing scaled distances it decreases. It is also understood that wind speed and the direction are effective in air overpressure propagation also, but this subject needs further investigation. It is concluded that according to the U.S. regulations there is no damage risk to the structures and no disturbance to the inhabitants at present. Due to the uncertainties in weather conditions, in order not to take any risks, the charge amount per delay should be kept at 35 kg or less for presplit blasting at the mine.

<p>Explosions are associated with more than 80% of the casualties in the Iraq and Afghanistan wars. Given the widespread use of thoracic protective armor, the most prevalent injury for combat personnel is blast-related traumatic brain injury (TBI). Almost 20% of veterans returning from duty had one or more clinically confirmed cases of TBI. In the decades of research prior to 2000, neurotrauma was under-recognized as a blast injury and the etiology and pathology of these injuries remains unclear.</p><p>This dissertation used the finite element (FE) method to address many of the biomechanics-based questions related to blast brain injuries. FE modeling is a powerful tool for studying the biomechanical response of a human or animal body to blast loading, particularly because of the many challenges related to experimental work in this field. In this dissertation, novel FE models of the human and ferret head were developed for blast and blunt impact simulation, and the ensuing response of the brain was investigated. The blast conditions simulated in this research were representative of peak overpressures and durations of real-world explosives. In general, intracranial pressures were dependent on the peak pressure of the impinging blast wave, but deviatoric responses in the brain were dependent on both peak pressure and duration. The biomechanical response of the ferret brain model was correlated with in vivo injury data from shock tube experiments. This accomplishment was the first of its kind in the blast neurotrauma field.</p><p>This dissertation made major contributions to the field of blast brain injury and to the understanding of blast neurotrauma. This research determined that blast brain injuries were brain size-dependent. For example, mouse-sized brains were predicted to have approximately 7 times larger brain tissue strains than the human-sized brains for the same blast exposure. This finding has important implications for in vivo injury model design, and a scaling model was developed to relate animal experimental models to humans via scaling blast duration by the fourth-root of the ratio of brain masses. </p><p>This research also determined that blast neurotrauma is correlated to deviatoric metrics of the brain tissue rather than dilatational metrics. In addition, strains in the blasted brain were an order-of-magnitude lower than expected to produce injury with traditional closed-head TBI, but an order-of-magnitude higher in strain rate. The 50th percentile peak principle strain metric of values of 0.6%, 1.8%, and 1.6% corresponded to the 50% risk of mild brain bleeding, moderate brain bleeding, and apnea respectively. These findings imply that the mechanical thresholds for brain tissue are strain-based for primary blast injury, and different from the thresholds associated with blunt impact or concussive brain injury because of strain rate effects.</p><p>The conclusions in this dissertation provide an important guide to the biomechanics community for studying neurotrauma using in vivo, in vitro, and in silico models. Additionally, the injury risk curves developed in this dissertation provide an injury risk metric for improving the effectiveness of personal protective equipment or evaluating neurotrauma from blast.</p> / Dissertation

Blast profiles and two primary methods of determining them were reviewed for use in the creation of a computer program for calculating blast pressures which serves as a design tool to aid engineers or analysts in the study of structures subjected to explosive air blast. These methods were integrated into a computer program, BLAST.F, to generate air blast pressure profiles by one of these two differing methods. These two methods were compared after the creation of the program and can conservatively model the effects of spherical air blast and hemispherical surface burst. The code, BLAST.F, was used in conjunction with a commercial finite element code (NASTRAN) in a demonstration of method on a 30 by 30 inch aluminum 2519 quarter plate of fixed boundary conditions in hemispherical ground burst and showed good convergence with 256 elements for deflection and good agreement in equivalent stresses of a point near the blast between the 256 and 1024 element examples. Application of blasts to a hypothetical wing comprised of aluminum 7075-T6 was also conducted showing good versatility of method for using this program with other finite element models. / Master of Science

Injury from blast is significant in both military and civilian environments. Although injuries from blast are well-documented, the mechanisms of injury are not well understood. Developing better protection requires knowledge of injury mechanisms and material response to blast loading. The importance of understanding how soft materials such as foams and fabrics behave under blast loading is further apparent when one realizes the capacity for some of these materials, frequently used in protective ensembles, to increase the potential for injury under some conditions. The ability for material configurations to amplify blast pressure and injury has been shown experimentally by other researches, and numerically in this study. Initially, 1-D finite element and mathematical models were developed to investigate a variety of soft materials commonly utilized in ballistic and blast protection. Foams, which have excellent characteristics in terms of energy absorption and density, can be used in conjunction with other materials to drastically reduce the amplitude of the transmitted pressure wave and corresponding injury. Additionally, a more fundamental examination of single layers of fabric was undertaken to investigate to the effects of parameters such as fabric porosity and density. Shock tube models were developed and validated against experimental results from the literature. After the models were validated, individual fabric properties were varied independently to isolate the influence of parameters in ways not possible experimentally. Fabric permeability was found to have the greatest influence on pressure amplification. Kevlar, a ballistic fabric, was modelled due to its frequent use for fragmentation protection (either stand-alone or in conjunction with a hard ballistic plate). The developed fabric and foam material models were then utilized in conjunction with a detailed torso model for the estimation of lung injury resulting from air blast. It was found that the torso model predicted both amplification and attenuation of injury, and all materials investigated as a part of the study had the capacity for both blast amplification and attenuation. The benefit of the models developed is that they allow for the evaluation of specific protection concepts.

Injury from blast is significant in both military and civilian environments. Although injuries from blast are well-documented, the mechanisms of injury are not well understood. Developing better protection requires knowledge of injury mechanisms and material response to blast loading. The importance of understanding how soft materials such as foams and fabrics behave under blast loading is further apparent when one realizes the capacity for some of these materials, frequently used in protective ensembles, to increase the potential for injury under some conditions. The ability for material configurations to amplify blast pressure and injury has been shown experimentally by other researches, and numerically in this study. Initially, 1-D finite element and mathematical models were developed to investigate a variety of soft materials commonly utilized in ballistic and blast protection. Foams, which have excellent characteristics in terms of energy absorption and density, can be used in conjunction with other materials to drastically reduce the amplitude of the transmitted pressure wave and corresponding injury. Additionally, a more fundamental examination of single layers of fabric was undertaken to investigate to the effects of parameters such as fabric porosity and density. Shock tube models were developed and validated against experimental results from the literature. After the models were validated, individual fabric properties were varied independently to isolate the influence of parameters in ways not possible experimentally. Fabric permeability was found to have the greatest influence on pressure amplification. Kevlar, a ballistic fabric, was modelled due to its frequent use for fragmentation protection (either stand-alone or in conjunction with a hard ballistic plate). The developed fabric and foam material models were then utilized in conjunction with a detailed torso model for the estimation of lung injury resulting from air blast. It was found that the torso model predicted both amplification and attenuation of injury, and all materials investigated as a part of the study had the capacity for both blast amplification and attenuation. The benefit of the models developed is that they allow for the evaluation of specific protection concepts.