Thesis (M.S.)--Oregon State University, 2004. / Printout. Includes bibliographical references (leaves 158-164). Also available on the World Wide Web.

Relatively few research efforts have focused on splice length requirements for reinforced masonry, despite the significant impact of these requirements on the safety, economy, and constructability of masonry walls. The Canadian masonry provisions for splice lengths in CSA S304.1-04 are taken directly from the Canadian concrete design standard, CSA A23.3-04, and thus do not necessarily reflect factors unique to masonry construction. Provisions in American masonry standard TMS 402-13/ACI 530-13/ASCE 5-13 are based on test results of double pullout specimens, but may be overly conservative due to shortcomings of the specimen type chosen. The purpose of this study is to examine the splice lengths needed for flexural masonry elements reinforced with bar sizes typically used in Canadian masonry construction. In this study, 27 wall splice specimens and 12 double pullout specimens were constructed. The wall splice specimens were tested horizontally in four point loading, while the double pullout specimens were tested in direct tension. Results from the double pullout specimen testing suggest that the techniques used at the University of Saskatchewan (U of S) are reasonably similar to those of the National Concrete Masonry Association (NCMA), and are thus adequate to assess current provisions in the American and Canadian standards. A predictive equation for the tensile resistance of spliced reinforcement was developed from the results of the wall splice specimen testing. This predictive equation was then adjusted to incorporate an adequate margin of safety for calculating splice length requirements for design purposes, using a five percent quantile approach. The adjusted predictive equation was then extrapolated to determine the splice lengths corresponding to the nominal yield strength of the reinforcement. These splice lengths were compared to current code provisions. It was found that the current CSA S304.1-04 Class B provisions, used almost exclusively in construction, are conservative for No. 15, 20, and 25 bars. In contrast, the TMS 402-13 provisions were overly conservative for all three bar sizes. Changes to the bar size factors of the current provisions for both codes were recommended to bring better consistency to the requirements of the two codes, and thus ensure the safety, economy, and constructability of masonry walls.

As an alternative to lap splicing, mechanical splices can be used for retrofit purposes. They are generally most economical than traditional lap splices when available spacing or length makes laps difficult to utilize. Mechanical splices are frequently used in new construction. However, their use is limited and not practical for use in retrofitted structures. However, if the bars to be joined do not need to be threaded in order to be connected with a special mechanical splice, such mechanical splices can be useful. It is presented a proposal of using two types of mechanical splices for retrofit purposes. Cycle Tension and cycle tension-compression tests are presented and discussed. It was found that mechanical splices are suitable and have acceptable response under seismic loads.

Post-earthquake examinations of reinforced concrete structures often show structural damage resulting from bond and shear failures. Such failures typically occur in reinforced concrete elements with details known to cause problems, such as widely spaced transverse reinforcement and/or lap splices located in regions of flexural yielding. These details are common in older reinforced concrete buildings (built before 1970) that have reinforced concrete columns with longitudinal reinforcement spliced just above the floor level, and transverse reinforcement spaced at a distance of d/2 or longer. This investigation focused on means to increase the deformability of existing reinforced concrete elements susceptible to bond and shear failures during a seismic event or other applications requiring toughness. The effects of confinement provided by epoxied anchors, spiral transverse reinforcement, and post-tensioned external clamps were investigated. Emphasis was placed on producing a strengthening device that can be sized, fabricated, and installed with ease because most of the existing strengthening techniques require specialized labor, tools, and materials. The observations collected support the idea that active confinement provided by post-installed and post-tensioned transverse reinforcement was the most effective method to improve structural deformability among the methods studied and within the ranges considered.

There is continued interest in nonlinear devices for different types of optical signal processing, such as Raman or parametric amplifiers. The small nonlinearity of conventional single-mode fibers sets a major limitation for these devices. A large nonlinearity can be achieved by having a large nonlinear coefficient, a small effective area, or both. Having a small effective area, however, requires efficient coupling to very small core fibers. A novel technique for splicing conventional single-mode fibers to small core fibers is proposed and demonstrated. The coupling efficiency obtained by this technique is considerably improved over that obtained by the butt-joint splice. This technique uses a highly tapered splice in which the field leaves the core and propagates as a fundamental cladding mode before it couples back to the core mode of the small core fiber. At the beginning of the taper the fundamental core mode carries most of the power. Over the down-taper region, the core mode couples to the fundamental cladding mode for which the cladding-air interface plays a major role in guiding the light. Over the up-taper region, the cladding mode is coupled back to the core mode. Fabrication of such a device involves many constraints. Alignment of the cores, the slope of the taper, and the taper length are important issues to ensure that excessive radiation loss does not take place. The theory of tapered single-mode fiber is discussed including adiabaticity criteria, length considerations, mode coupling and wavelength dependence. We use a computational simulation to examine how the field changes from one part of the taper to the other. Variations of the fiber and the field properties along the taper are studied. In this simulation, the tapered region is approximated as a sufficiently large number of cascaded uniform fiber segments of decreasing or increasing diameters. Another analysis based on the conservation of power flow is also provided. Tapered splices were fabricated using two different experimental setups. The experimental setup to verify our theoretical results is shown. The tapering process is thoroughly discussed. The spectrum of a tunable laser passing through a splice shows how modes interact with each other during the tapering process. We successfully fabricated very low loss tapers with extremely small diameters. Tapered splices showed a lower loss than their butt-joint counterparts. Experimental measurements of these tapered splices are presented and discussed. / Ph. D.

Highway bridges in the United States are frequently damaged by overheight vehicle collisions. The increasing number of prestressed concrete bridges indicates that the probability of such bridges being impacted by overheight vehicles has increased. This thesis, sponsored by the Virginia Center for Transportation Innovation and Research (VCTIR), investigated three repair techniques for impact damaged prestressed bridge girders: strand splices, fiber reinforced polymer (FRP) overlays, and fabric reinforced cementitious matrix (FRCM) overlays. The flexural strength of four AASHTO Type III girders, three of which were intentionally damaged and repaired, was evaluated. Six experimental tests were performed on these girders: one undamaged girder test and five repair method tests. Nonlinear beam models and three-dimensional finite element (FE) models were created to predict the behavior of the beams under flexural testing, and subsequently validated and calibrated to experimental test data. The very good accuracy of the beam models indicated that they can be used alone for the performance assessment of damaged and repaired girders. Of course, the analyst must always be aware of the fact that a beam model cannot explicitly account for potentially crucial effects such as diagonal cracking. A direct comparison between repair methods was made by creating analytical models of a prototype girder setup. FRP overlays were seen to restore the most strength, while strand splices were seen to restore the most ductility. From observation, combining repair methods resulted in an additive effect on strength, but the deformation at onset of failure will be governed by the less ductile method. / Master of Science

This study is part of a VDOT sponsored project focusing on repair techniques for impact damaged prestressed bridge girders. The investigation included evaluation of the repair installation and flexural strength of four AASHTO Type III girders that were intentionally damaged and repaired. In addition, nonlinear finite element modeling was used to aid in the development of design protocols for each repair method. This report discusses two of the three repair techniques. Three Master of Science students report on the project results: Justin Liesen, Mark Jones, and Michael Gangi. Liesen and Jones (2015) had responsibility for the installation and testing of the repaired girders and Gangi (2015) performed the finite element modeling of the girders. Three repair methods were identified for experimental investigation: strand splice, bonded FRP, and FRCM. During this investigation the repair methods were evaluated by conducting six flexural tests on four AASHTO Type III girders. Flexural tests were conducted instead of shear tests because typical impact damage from overheight vehicles occurs around the mid-span and flexural strength dominated region of bridge girders. The cracking and failure moments for each test were evaluated and compared to predictions of the girder's behavior using AASHTO calculations, a moment-curvature diagram, and non-linear finite element modeling. / Master of Science

The tensile resistance of No. 15 lap spliced reinforcing bars with varying transverse spacing and lap splice length was evaluated in full-scale concrete block wall splice specimens. The range of the transverse spacing between bars was limited to that which allowed the bars to remain within the same cell, and included the evaluation of tied spliced bars in contact. Two-and-a-half block wide by three course tall double pullout specimens reinforced with contact lap splices were initially used to determine the range of lap splice length values to be tested in the wall splice specimens such that bond failure of the reinforcement occurred. The double pullout specimens were tested in direct tension with six replicates per arrangement. Three values of lap splice length: 150, 200, and 250 mm, were selected from the testing of the double pullout specimens and tested in the wall splice specimens in combination with three values of transverse spacing: 0, 25, and 50 mm, with three replicates per configuration. A total of twenty-seven two-and-a-half block wide by thirteen course tall wall splice specimens reinforced with two lap splices were tested in four-point loading. Both the double pullout and the wall splice specimens were constructed in running bond with all cells fully grouted. The tensile resistance of the lap spliced bars in the double pullout specimens was measured directly. The contact lap splices with a 150, 200, and 250 mm lap splice length developed approximately 38, 35 and 29% of the theoretical yield load of the reinforcement, respectively. The difference between the mean tensile resistances of the three reinforcement configurations tested in the double pullout specimens was found to be statistically significant at the 95% confidence level. Different than expected, the tensile resistance of the lap spliced reinforcing bars in the double pullout specimens was inversely proportional to the lap splice length provided. For the short lap splice lengths used in this investigation, the linear but not proportional relationship between bond force and lap splice length known from reinforced concrete is believed to have caused this phenomenon. An iterative sectional analysis using moment-curvature response was used to calculate the tensile resistance of the lap spliced reinforcement in the wall splice specimens. The calculated mean tensile resistance of the reinforcement increased with increasing lap splice length, and was greater when the bars were in contact. Securing the bars in contact may have influenced the tensile capacity of the contact lap splices as higher stresses are likely to develop as a result of the bar ribs riding over each other with increasing slip. Results of the data analysis suggest that the tensile resistance of non-contact lap splices within the same cell is generally independent of the spacing between the bars. A comparison of the experimental results for the wall splice specimens with the development and splice length provisions in CSA S304.1-04 and TMS 402-11 indicate that both the Canadian and U.S. design standards are appropriate for both contact and non-contact lap splices located within the same cell given the limited test database included in this investigation.

Increased national and international travel over the lastdecades has caused an increase in the global number ofpassengers using different means of transportation. Greateffort is being directed to improving the noisy environment inthe residential community. This is to face the growing strictnoise requirements which are implemented by international noiseregulatory authorities, governments, and local airports. Thereis also a strong competition between different manufacturers tomake their products quieter. The propulsion system in anaircraft is the major source of noise during relevant flightconditions. The engine noise in a vehicle dominates the totalradiated noise at low speeds especially inside cities. Manyrecent studies on noise reduction involve the use of perforatedplates in the air and gas flow ducting connected to the engine.This thesis deals with the modelling of perforates as anabsorbent. There are many difficulties in using liners in theseapplications. The most important is that there is no largesurface area to which the linings may be applied. Equally, theenvironment in which linings have to survive is hostile.Therefore, liners have to be carefully tailored in order toachieve the most efficient attenuation. The full-scalesimulation testing, which is usually necessary to define thenoise attenuation produced by a liner installation, is bothtime-consuming and expensive. Therefore, a need for accuratemodels is a must. This thesis fills some gaps in the impedancemodelling of perforated liners. It also concentrates on thosecomplicated situations of sound propagation in ducts that weresolved earlier using Finite Element Methods. Alternateanalytical solutions to these problems are developed here,which gives more physical insight into the results. The key design parameter of perforates is the acousticimpedance. The impedance is what determines their efficiency toabsorb sound waves. A semi empirical impedance model wasdeveloped to be capable of accurately predicting the linerimpedance as a function of its physical properties and thesurrounding conditions. It was compared to all previous modelsin the literature. Nothing in the literature has been reportedon the effect of temperature on the perforate impedance,therefore a complete study was performed. A new inverseanalytical impedance measurement technique was proposed. It isbased on educing the impedance value based on the measurementof the attenuation across a lined duct section. Twoapplications were further considered: The effect of hard stripsin lined ducts on there attenuation properties; and themodelling of perforations in a complicated automotive mufflersystem. Keywords:Perforates–Liners–Acousticimpedance–Hot stream liners–Hard splices–Mufflers–Lined ducts–Collocation–Flowduct.

The effectiveness of a new structural material, namely textilereinforced mortar (TRM), was investigated experimentally in this study as a means of confining old-type reinforced concrete columns with limited capacity due to bar buckling or due to bond failure at lap splice regions. Comparisons with equal stiffness and strength fiber-reinforced polymer (FRP) jackets allow for the evaluation of the effectiveness of TRM versus FRP. Tests were carried out on full scale non-seismically detailed RC columns subjected to cyclic uniaxial flexure under constant axial load. Thirteen cantilever-type specimens with either continuous longitudinal reinforcement (smooth or deformed) or lap splicing of longitudinal bars at the floor level were constructed and tested. Experimental results indicated that TRM jacketing is quite effective as a means of increasing the cyclic deformation capacity of old-type RC columns with poor detailing, by delaying bar buckling and by preventing splitting bond failures in columns with lap spliced bars. Compared with their FRP counterparts, TRM jackets used in this study were found to be equally effective in terms of increasing both the strength and deformation capacity of the retrofitted columns. From the response of specimens tested in this study, it can be concluded that TRM jacketing is an extremely promising solution for the confinement of reinforced concrete columns, including poorly detailed ones with or without lap splices in seismic regions.