Experimental and analytical research has been conducted to investigate the degradation of shear performance of beams due to bond deterioration and longitudinal bar cutoffs. To achieve the controlled rate of bond degradation, the method of adjustment of the rib height by machining was adopted. Bond behaviour of the milled bars were measured in tension stiffening tests with internally installed strain gauges. Maximum bond stresses for the milled bars were reduced by up to 50% compared to those for normal deformed bar. The bond behaviour of the milled bars were compared with those of the bars subjected to accelerated corrosion. It was confirmed that the stripped bar had the possibility to simulate corroded bars to some extent. Based on the calculations of average tensile stresses in the cracked concrete for each specimen, appropriate tension stiffening factors for each type of bar were suggested and then verified with the 2-dimensional nonlinear finite element analysis program VecTor2. Next, eight simply supported beams were tested. In four of them half of the longitudinal bars were cut off near the supports. Various combinations of normal and machined reinforcing bars were selected for both longitudinal and transverse reinforcement. The predicted shear failure load for the cutoff beam based on the general method for shear design in CSA A23.3-04 was unconservatively estimated. Cutoffs of longitudinal reinforcement resulted in much more significant drops of shear resistance than did bond deterioration of reinforcement. The inclinations of diagonal cracks for the cutoff series were larger than those for the no-cutoff series due to significant concentrations of longitudinal strains near the cutoff locations. Finally modifications to the general shear design method in CSA A23.3-04 were proposed based on the results of VecTor2 analyses for the beam tests. It was found that the influence of bond deterioration on the shear strength of reinforced concrete member can be accounted for by adjusting the tension stiffening factor applied to the equation for β. With respect to bar cutoffs, its influence on shear strength can be expressed by the strain concentration factor applied to the equation for ε_x.

It is well known that arching action in reinforced concrete slabs resulting from surrounding restraining elements is responsible for much greater collapse loads than those estimated considering flexural effects only. However, the subject needs to be better understood and simplified if it is to be reliably applied in broader practice. This thesis presents a rational treatment of the problem. By limiting the scope of investigation to one-way slab systems, for the first time an explicit method of calculating the load-carrying capacity of elastic- plastic slab strips with a laterally rigidly restrained boundary condition is derived. Application of the proposed model to specimens selected from four experiment programs proves its reliability in ultimate strength calculations. The proposed model is then employed in a parametric study of structural responses of deck slab strips. The parametric study shows that a longer span, lightly reinforced deck slab system is still adequate in strength if it is cast in higher strength concrete and sufficient lateral restraint is available.

Experimental and analytical research has been conducted to investigate the degradation of shear performance of beams due to bond deterioration and longitudinal bar cutoffs. To achieve the controlled rate of bond degradation, the method of adjustment of the rib height by machining was adopted. Bond behaviour of the milled bars were measured in tension stiffening tests with internally installed strain gauges. Maximum bond stresses for the milled bars were reduced by up to 50% compared to those for normal deformed bar. The bond behaviour of the milled bars were compared with those of the bars subjected to accelerated corrosion. It was confirmed that the stripped bar had the possibility to simulate corroded bars to some extent. Based on the calculations of average tensile stresses in the cracked concrete for each specimen, appropriate tension stiffening factors for each type of bar were suggested and then verified with the 2-dimensional nonlinear finite element analysis program VecTor2. Next, eight simply supported beams were tested. In four of them half of the longitudinal bars were cut off near the supports. Various combinations of normal and machined reinforcing bars were selected for both longitudinal and transverse reinforcement. The predicted shear failure load for the cutoff beam based on the general method for shear design in CSA A23.3-04 was unconservatively estimated. Cutoffs of longitudinal reinforcement resulted in much more significant drops of shear resistance than did bond deterioration of reinforcement. The inclinations of diagonal cracks for the cutoff series were larger than those for the no-cutoff series due to significant concentrations of longitudinal strains near the cutoff locations. Finally modifications to the general shear design method in CSA A23.3-04 were proposed based on the results of VecTor2 analyses for the beam tests. It was found that the influence of bond deterioration on the shear strength of reinforced concrete member can be accounted for by adjusting the tension stiffening factor applied to the equation for β. With respect to bar cutoffs, its influence on shear strength can be expressed by the strain concentration factor applied to the equation for ε_x.

Bioenergy production from forest resources offers opportunities to reduce greenhouse gas (GHG) emissions associated with fossil fuel use, reduce non-renewable energy consumption, and provide investment and employment in the forestry sector. These opportunities, however, must be considered within the broader contexts of forest systems. Of particular interest is how bioenergy opportunities impact carbon storage within the forest. This thesis develops a method to integrate life cycle assessment and forest carbon analysis approaches to quantify the total GHG emissions associated with forest bioenergy. Bioenergy production and utilization decisions are then investigated to evaluate opportunities to increase GHG mitigation performance. An accounting method is developed to evaluate the impact of emissions timing on the cost-effectiveness of GHG emissions reductions from biomass-based electricity generation. Applying the integrated life cycle assessment/forest carbon analysis method to a case study of forest bioenergy production in Ontario reveals significant reductions in forest carbon associated with bioenergy production. Wood pellet production from standing trees or harvest residues (displacing coal in electricity generation) would increase total GHG emissions over periods of approximately 40 and 15 years, respectively. Ethanol production (displacing gasoline) would increase GHG emissions throughout the 100-year model period if produced from standing trees; emissions would increase over a period of approximately75 years if produced from harvest residues. Strategic ethanol production decisions (e.g., process energy source, co-location with other processes, co-product selection) can improve GHG mitigation. Co-production of biomass pellets with ethanol performs best among co-product options in terms of GHG emissions; co-location with facilities exporting excess steam and biomass-based electricity further increases GHG mitigation performance. Delayed GHG reductions due to forest carbon impacts the cost of GHG emissions reductions associated with electricity production from forest biomass. Cost-effectiveness is heavily dependent on the time horizon over which global warming impacts are measured and influences the ranking of biomass electricity pathways (biomass co-firing is the most cost-effective pathway between 2020 and 2100; biomass cogeneration is the most cost-effective pathway beyond year 2100). The accounting tools and methods developed within this thesis will to help inform decision-makers in the responsible development of forest bioenergy opportunities and associated policies.

It is well known that arching action in reinforced concrete slabs resulting from surrounding restraining elements is responsible for much greater collapse loads than those estimated considering flexural effects only. However, the subject needs to be better understood and simplified if it is to be reliably applied in broader practice. This thesis presents a rational treatment of the problem. By limiting the scope of investigation to one-way slab systems, for the first time an explicit method of calculating the load-carrying capacity of elastic- plastic slab strips with a laterally rigidly restrained boundary condition is derived. Application of the proposed model to specimens selected from four experiment programs proves its reliability in ultimate strength calculations. The proposed model is then employed in a parametric study of structural responses of deck slab strips. The parametric study shows that a longer span, lightly reinforced deck slab system is still adequate in strength if it is cast in higher strength concrete and sufficient lateral restraint is available.

Master of Science / Department of Architectural Engineering and Construction Science / Sutton F. Stephens / Glass can be beautiful and strong, so why is it not used more often as a structural material? Most often the reasoning is because people fear its perceived fragile and dangerous nature. Although this is the perception, it is far from the reality. Structurally designed glass can even withstand higher loads than steel. The following report will present several advantages of using glass as a structural material. Because understanding the history of glass can foster a greater understanding of where the future of glass is headed, it is discussed early on. After this, the focus is on how to make a mixture of molten liquid into a structural member. The manufacturing process is at the root of the strength of glass, as are the material properties. The composition and properties of glass are addressed before discussing various uses of glass as a structural material. As architects begin to ask for more structural glass in their projects, structural engineers must be prepared to design the systems or to specify performance criteria to a specialty engineer. To aid in design, published guidelines and testing must be utilized and are therefore discussed. In a glass structural system, the glass is not the only aspect that needs an engineer's attention. Connections present a special challenge when designing with structural glass, but several different forms of connections have been successfully demonstrated in construction. To tie all the previous topics together, three examples of structural glass systems are presented. Europe has been using glass as a structural material for years, but the United States has been slow to follow the trend. Glass has been proven to work as a structural material that can create impressive visual impact. With the support of the glass manufacturing industry and the courage of design engineers, the United States could easily start a movement towards building with structural glass.

Master of Science / Department of Civil Engineering / Mustaque A. Hossain / Pavement preservation by adopting low-cost maintenance techniques is increasing among transportation agencies day by day. Chip seal, also known as seal coat, is widely used as a low-cost, thin surface treatment in preventive maintenance of asphalt pavements in many states, including Kansas. Loosening of aggregate particles from chip-sealed pavement and associated windshield damage to vehicles is a common problem. Thus the Kansas Department of Transportation (KDOT) uses lightweight aggregates as cover materials for chip seals. Although this has decreased windshield damage problems extensive chip loss on seal-coated pavements in the state has been reported. In this study, lightweight aggregates along with polymer-modified asphalt emulsion were used to determine proper aggregate and emulsion application rates to minimize chip loss in chip seals. Again, lightweight aggregates were studied in the laboratory to determine the effect of moisture content and electrical charge on chip loss. Evaluation of chip seal was performed by statistical analysis based on rutting potential, chip embedment, and retention. Results show that aggregate retention and embedment depth depend on aggregate-emulsion interaction, whereas rutting depends on the type of aggregate. Proper selection of aggregate and asphalt emulsion is important to maximize aggregate retention in chip seal. Chip loss also results from a lack of compatibility between the aggregate and asphalt emulsion. Results indicate that retention of aggregate depends on the prevailing charges of aggregate and emulsion particles. Moisture condition of the aggregate does not have any effect on chip loss. A new sweep test machine has been developed to assess chip loss, and it was found to be better than the sweep test currently recommended by the American Society for Testing and Materials (ASTM).

Doctor of Philosophy / Department of Civil Engineering / Asadollah Esmaeily / Civil structures are susceptible to damages over their service lives due to aging, environmental loading, fatigue and excessive response. Such deterioration significantly affects the performance and safety of structure. Therefore, it is necessary to monitor the structural performance, detect and assess damages at the earliest possible stage in order to reduce the life-cycle cost of structure and improve its reliability. Over the last two decades, extensive research has been conducted on structural health monitoring and damage detection. In this study, a signal-based pattern-recognition method was applied to detect structural damages with a single or limited number of input/output signals. This method is based on the extraction of sensitive features of the structural response under a known excitation that present a unique pattern for any particular damage scenario. Frequency-based features and time-frequency-based features of the acceleration response were extracted from the measured vibration signals by Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT) to form one-dimensional or two-dimensional patterns, respectively. Three pattern recognition algorithms were investigated when performing pattern-matching: (1) correlation, (2) least square distance, and (3) Cosh spectral distance. To demonstrate the validity and accuracy of the method, numerical and experimental studies were conducted on a simple small-scale three-story steel building. In addition, the efficiency of the features extracted by Wavelet Packet Transform (WPT) was examined in the experimental study. The results show that the features of the signal for different damage scenarios can be uniquely identified by these transformations. Suitable correlation algorithm can then be used to identify the most probable damage scenario. The proposed method is suitable for structural health monitoring, especially for the online monitoring applications. Meanwhile, the choice of wavelet function affects the resolution of the detection process and is discussed in the “experimental study part” of this report.

Master of Science / Department of Architectural Engineering and Construction Science / Kimberly W. Kramer / The concept of prestressed concrete appeared in 1888 when P.H. Jackson was granted the first patent in the United States for prestressed concrete design. Jackson’s idea was perfect, but the technology of high strength steel that exhibited low relaxation characteristics was not yet available. It was not until Eugene Freyssinet defined the need for these materials that prestressed concrete could be used as a structural building material. Unfortunately, although Freyssinet, a brilliant structural designer and bridge builder, lacked the teaching qualities necessary to communicate his ideas to other engineers. It would take Gustave Magnel to write the first book of design in prestressed concrete, communicating this idea to designers worldwide. Magnel designed and built the legendary Walnut Lane Bridge in Philadelphia, which revolutionized prestressed concrete in America. Simultaneously, Urlich Finsterwalder, the German bridge builder and designer, was revolutionizing the construction means and methods for prestressed concrete bridges. For example, Finsterwalder invented the free-cantilever construction method of prestressed concrete bridges, which allowed long span bridges to be constructed without stabilized shoring. He then designed stress-ribbon bridges, which would eventually allow prestressed concrete to span distances only steel suspension bridges could achieve. However, it wasn’t until Paul Abeles and his peer, H. von Emperger studied and tested prestressed concrete that the idea of “partial prestressing” emerged. Initially, Freyssinet and Magnel were adamant that prestressed concrete should not be allowed to exhibit any tensile forces at sustained loading. Later, the Roebling family developed the first stress--relieved wire followed by the first stress-- relieved strand. T.Y. Lin once again brought prestressed concrete back into the spotlight when he organized the First Prestressed Concrete World Conference in 1957. Shortly after this conference, Lin published a technical paper in the Prestressed Concrete Institute (PCI) Journal that introduced a new Load Balancing technique which allowed most structural engineers to design prestressed concrete very easily.

Master of Science / Department of Architectural Engineering and Construction Science / Sutton F. Stephens / Cold-formed steel studs, though they are a relatively new building material, have become a mainstay in modern construction. They are favored over traditional lumber studs for their high strength to weight ratio and resistance to insects and rot. Due to their relative newness as a material, new advances in their design and implementation are being developed quite rapidly. One such advancement is flange embossing, a technique used to increase the strength of the connection of screws into the studs. Currently, embossed flanges are not specifically addressed in the North American Specification for the Design of Cold-Formed Steel Structural Members (AISI S100), thereby preventing current design equations from being used to calculate an embossed stud's member properties. An experimental investigation was undertaken to determine what effect, if any, flange embossing has on the nominal flexural strength of cold-formed steel studs as determined using the provisions of AISI S100-07. Studs with embossed flanges were tested in bending and their actual flexural strength was computed. This data was then compared with the nominal flexural strength determined using the AISI Specification, without embossing, to determine if these equations would still be appropriate for the design of embossed studs.