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A cast modular connector (MC) has been developed for use in seismic-resistant steel moment frames. The MC is a field bolted beam flange connection intended to serve as the frame's special energy-dissipating detail. The connector is specifically configured for optimal seismic performance through a casting process. The MC possesses inherent ductility through variable-section arms that minimize plastic strain demand and a reliable yet economical fastening method through a base end-region that virtually eliminates prying forces on bolts.The dissertation presents three journal papers. The first paper describes the portion of the analytical research focused on establishing the optimum geometry for the energy dissipating arm elements. Key parameters were evaluated through parametric studies using nonlinear (material and geometry) finite element analysis and supported by basic theoretical models. The outcome was a set of optimum geometric ratios covering width reduction, length to thickness, aspect ratio, and fillet radius.The second paper describes the development process of the isolated connector rather than full-connection behavior. Designs were alternately evaluated for structural performance and castability through the electronic exchange of solid model files with steel foundry industry partners. The analytical results indicate the potential for excellent ductility and energy dissipation characteristics in the MC Beta prototype.The third paper focuses on the prototyping and experimental verification of the MC Beta prototype. Steel foundry industry partners cast the MC Beta prototype at approximately half-scale. The scaled MC Beta prototype was tested in isolated fashion under monotonic and cyclic loading. The experimental results confirmed the performance of the analytically-based designs. The MC Beta prototype exhibited exceptional performance in terms of stable energy dissipation, far exceeding qualifying rotational ductility capacities. In direct comparisons to a WT section of similar stiffness and strength, the MC Beta prototype possessed greatly enhanced ductility and energy dissipation characteristics.With the MC Beta prototype developed and experimentally verified under isolated conditions, an experimental verification of beam-to-column joints containing the scaled MCs were performed using accepted testing protocols. The preliminary test results indicate that the connection exceeded qualifying rotational ductility capacities and showed promise as a special energy-dissipating detail in seismic-resistant steel moment frames.

Masonry infilled walls have been commonly used as interior partitions as well as exterior walls infilled in either steel or reinforced concrete frames in the modern building constructions. In recent years, much research involving both experimentation and numerical modeling has been conducted in an effort to better understand the infill-frame interaction and to provide some rational design approaches. Studies have shown that infill walls can develop a number of possible failure mechanisms, depending on the strength and stiffness of the bounding frames with respect to those of the infills and the geometric configuration of the framing system. Most of models proposed for analysis of infill walls focused on one type of mechanism or the other, and they were not universally applicable to all infilled structures.

Steel bridges and structures often need strengthening due to increased life loads, or repair due to corrosion or fatigue cracking. This study explored the use of adhesively bonded Carbon Fibre Reinforced Polymers (CFRP) flexible sheets and rigid plates in retrofitting steel columns and girders, through experimental and analytical investigations. The first part of the research program investigated the behaviour of CFRP-strengthened steel columns comprised of square Hollow Structural Sections (HSS). Fifty columns, 175 mm to 2380 mm long (i.e. with slenderness ratios ranging from 4 to 93), were tested under axial compression loads to examine the effects of number and type of CFRP layers, fibre orientation, and slenderness ratio. Transverse wrapping was shown to be suitable for controlling outwards local buckling in HSS short columns, while longitudinal layers were more effective in controlling overall buckling in slender columns. The maximum increases in axial strength observed in the experiments were 18 and 71 percent, for short and slender columns, respectively. An analytical fibre-element model and a non-linear finite element model were developed for slender columns. The models account for steel plasticity, geometric non-linearities, and residual stresses. The models were verified using experimental results, and used in a parametric study. It was shown that CFRP effectiveness increases for columns with larger out-of-straightness imperfections and higher slenderness ratios. The second part of the research program investigated w-section steel-concrete composite girders retrofitted using CFRP materials. Three girders, 6100 mm long, were tested to study strengthening of intact girders using CFRP plates. Eleven girders, 2030 mm long, including girders artificially damaged by completely cutting their tension flanges at mid-span, were tested to study the effectiveness of repair using CFRP sheets. The parameters considered were the CFRP type, number of layers, number of retrofitted sides of the tension flange, and the length of CFRP repair patch. The strength and stiffness of the intact girders have increased by 51 and 19 percent, respectively. For the repaired girders, the strength and stiffness recovery ranged from 6 to 116 percent and from 40 to 126 percent, respectively. Unlike flexural strength, the stiffness was not much affected by the bond length. Analytical models were developed, verified, and used in a parametric study, which showed that the higher the CFRP modulus, the larger the gain in stiffness and yielding moment, but the lower the gain in strength and ductility. In general, this study demonstrated that steel structures can indeed be successfully strengthened or repaired using CFRP material. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2007-11-15 18:35:59.552

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Gerdau Manitoba Mill (Gerdau) at Selkirk, Manitoba is one of the biggest energy consumers in the province of Manitoba. This research analysis undertaken at Gerdau evaluated opportunities for energy efficiency, including the following six areas: 1) recovering waste heat to preheat billets, 2) upgrading the charge end in the reheat furnace, 3) recovering waste heat to preheat combustion air in the ladle preheater, 4) replacing direct-fired natural gas heaters with indirect-fired natural gas heaters, 5) Oxyfuel combustion, and 6) “tap to tap time” control in the eccentric bottom tapping (EBT) furnace in the melt shop. As part of this research, end-user distribution was analyzed and energy losses were assessed. An end-use analysis found that the melt shop that includes the EBT furnace is the biggest consumer of electricity consumption (kWh) and electric demand (kVa), which accounted for 68.7% and 73.6 % respectively. The 2010 delay time in the power-off time of EBT furnace at Gerdau was found to be 762.3 hr/yr. Further research to analyze the cause of each downtime at Gerdau is recommended to determine how these unplanned downtime can be reduced in the EBT furnace. The reheat furnace is the biggest natural gas consumer at Gerdau with 437,563 MCF in 2010. Flue gas losses from the reheat furnace are the biggest energy losses in the gross heat distribution with 26,874,657 Btu/hr. Energy losses from hearth and roof by heat transmission are the biggest energy losses in the net heat distribution during operation, which accounted for 8.9%. The average thermal efficiency in the reheat furnace at Gerdau is 58.9% ± 3.6%. Compared to peak capacity, idle and partial operations of the reheat furnace and idling were found to be less efficient. The opportunities that are considered feasible and recommended to Gerdau are: 1) recovering waste heat to preheat billets, 2) upgrading the charge end in the reheat furnace, 3) recovering waste heat to preheat combustion air in the ladle preheater, 4) replacing direct-fired natural gas heaters with indirect-fired natural gas heaters. These are both good for the environment, reducing fuel use and emissions and providing a good payback period and annual savings. Many opportunities are available for reducing energy as provided in Table A, which shows emissions reductions, costs, energy savings and payback. Oxyfuel combustion is not deemed feasible without considering productivity improvement as oxygen cost is more than natural gas saving. A number of incentive programs, including those from Manitoba Hydro, are applicable to Gerdau. However, a number of barriers to accessing these, particularly as regards tax incentive programs, should be explored to see if these barriers can be overcome.

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