Over the past fifty years, many states have recognized the benefits of making precast, prestressed multi-girder bridges continuous by connecting the girders with a continuity diaphragm. Although there is widespread agreement on the benefits of continuous construction, there has not been as much agreement on either the methods used for design of these systems or the details used for the continuity connections. To aid designers in choosing the most appropriate method, an analytical and experimental study was undertaken at Virginia Tech. Analyses were done to compare the differences in the predicted continuity moments for different design methods and assumptions over a range of commonly used systems of Precast Concrete Bulb Tee (PCBT) girders and cast-in-place slabs. The results of the analyses were used to develop three continuity connection details for testing during the experimental study. Three different continuity connections were tested using full depth PCBT 45 in. deep girders made continuous with a 6 ft wide slab. The bottom of the ends of the girders were made continuous with the continuity connection by extending prestressing strands for one test and extending 180 degree bent bars for the other test. Both connections adequately resisted service, cyclic, and ultimate loads. But, the test with the extended bars remained stiffer during cyclic loading and is recommended for use. A third test was performed on a system using only a slab cast across the top of the girders. Two primary cracks formed above the ends of the girders at the joint during service testing, after which no significant increase in damage took place. Results from the analytical study indicate that the predicted positive thermal restraint moments may be significant, similar in magnitude to the actual positive cracking moment capacities. Results from the experimental study indicate that restraint moments develop early due to thermal expansion of the deck during curing and subsequent differential shrinkage; however, the magnitudes of the early age restraint moments are much less than conventional analyses predict. / Ph. D.

This research document focuses on prestressed PCBT girders made composite with a cast-in-place concrete deck and continuous over several spans through the use of continuity diaphragms. The current design procedure in AASHTO states that a continuity diaphragm is considered to be fully effective if a compressive stress develops in the bottom of the diaphragm when the superimposed permanent load, settlement, creep, shrinkage, 50 percent live load, and temperature gradient are summed, or if the girders are stored at least 90 days when continuity is established. It is more economical to store girders for fewer days, so it is important to know the minimum number of days that girders must be stored to satisfy AASHTO requirements. In 2005, Charles Newhouse developed the positive moment diaphragm reinforcement detail that is currently being adopted by VDOT. This thesis concludes that Newhouse's detail, four No. 6 bars bent 180° and extended into the diaphragm, is adequate for all girders except for the PCBT-77, PCBT-85, and the PCBT-93 when the girders are stored for a minimum of 90 days. It is recommended that two additional bent strands be extended into the continuity diaphragm for these three girder sizes. It was also concluded that about half of the cases result in a significant reduction in the minimum number of storage days if the designer is willing to perform a detailed analysis. The other half of the cases must be stored for 90 days because the total moment in the diaphragm will never become negative and satisfy the AASHTO requirement. In general, narrower girder spacing and higher concrete compressive strength results in shorter required storage duration. The PCA Method was used in this analysis with the updated AASHTO LRFD creep, shrinkage, and prestress loss models. A recommended quick check is to sum the thermal, composite dead load, and half of the live load restraint moments. The girder must be stored 90 days if that sum is positive, and a more detailed time-dependent analysis would result in a shorter than 90 day storage period if that sum is negative. / Master of Science

Freudenberg Sealing Technologies has developed a new concept for the manufacture of diaphragm accumulators. Its advantages are a reduced need for components, fewer process steps, shorter assembly times, a higher level of product cleanliness, and an expansion of the product portfolio into additional fields of application. These diaphragm accumulators also weigh significantly less. This is opening up new opportunities for applications in the automotive and industrial fields. The assembly concept is based on a hermetically sealed pressure chamber in which the joining of the two housing halves with the help electromagnetic pulse technology (EMPT) as well as the filling of the gas side with nitrogen takes place in a single operation. In this way, downstream filling to generate the initial gas charge is no longer necessary.

The alternative seismic design provisions for diaphragms provided in ASCE 7-22 Minimum design loads and associated criteria for buildings and other structures Section 12.10.3 account for both diaphragm ductility and displacement capacity, producing more accurate design forces and decreased detailing when compared to conventional seismic design methods. However, the diaphragm design force reduction factor has not yet been determined for tension-only roof truss diaphragms, a common system used in metal buildings. In this study, experimental tests of two cantilevered diaphragm subassembly specimens with tension-only rod bracing were conducted to determine the load-deformation behavior of the system. The first specimen used 7/8-in. rods, two types of hillside washers, two types of compression members, and two configurations of lateral bracing. The second specimen used 3/4-in. rods, one type of hillside washer, one type of compression member, and one configuration of lateral bracing. Four tests were conducted. One additional test was conducted on each specimen to determine the friction in the test setup. The system developed significant ductility during testing and the yield mechanism was primarily tensile yielding of the rods. The results indicate that a diaphragm design force reduction factor of 2.0 for structures with periods greater than 1.0 second and 1.7 for structures with periods between 0.12 and 0.5 seconds may be appropriate for metal building systems if the lateral bracing of the compression member is prevented from buckling.

Monitoring accurate temperature and pressure profiles in harsh environments is currently in high demand in aerospace gas turbine engines and nuclear reactor simulators. Having the ability to measure both quantities continuously over a region, without thermal coupling, using a sensor with a small size (envelope) is also highly desirable. Currently available MEMS (microelectromechanical systems) provide effective small scale pressure and temperature measurement devices, however, they have only been shown to be effective up to 600C and lack the ability to perform distributed measurements unless combined with fiber-optic techniques. In general, fiber-optics provide many advantages over electrical based sensors and are the ideal choice for high temperature regimes and distributed sensing. In this thesis, preliminary designs and suggested future work are presented for a sensor built within an 3.175 mm radius envelope and capable of distributed pressure and temperature sensing up to temperatures reaching 800C. Finite element analysis via ANSYS, along with analytical verification models have been used for the design evolution. Diaphragm based designs, seem to provide easy fabrication methods and good sensitivity, however, for this design to be realized at high temperature operation, a robust bonding method must be chosen to avoid unwanted deformation due to misfit strains. / Master of Science

Twenty cantilever diaphragm tests were performed in the Structures and Materials Laboratory at Virginia Tech. The tests included both deep deck and cellular deck profiles with varying structural and side-lap connections. The tests were conducted with three different structural connections: screws, pins and welds and two different side-lap connections: screws and button punch. The tests were conducted and both load and deflection of the diaphragms were recorded. The current International Code Council, ICC, evaluation procedure shows that there are two different methods for measuring diaphragm deflection. The first method was by measuring specific corner displacements and making corrections to remove any rigid body motion. The second method is by measuring the deflection of the diagonals of the diaphragm. In this study both measurements were taken to do a comparison of the results that were obtained. Both strength and stiffness values were calculated based on the Steel Deck Institute (SDI) Diaphragm Design Manual (2004) and modifications described by Luttrell (2005). The paper by Luttrell (2005) only recommends modifications for the calculation of diaphragm stiffness. The data obtained from the tests were compared to the SDI calculations to distinguish any noticeable trends. Modifications are recommended regarding diaphragm strength and further research is suggested to create a better stiffness prediction of diaphragms. / Master of Science

No description available.

Master of Science / Department of Architectural Engineering / Kimberly Waggle Kramer / Main lateral force resisting systems (MLFRS) in timber buildings consist of two components: diaphragms and shear walls. Diaphragms are used to collect the shear induced by the lateral force at each of the levels. The shear is transferred from the diaphragms to the shear walls via plywood sheathing and connections. The shear walls transfer shear to the sill plate via plywood sheathing and then into the foundation via anchors. Two approaches for designing shear wall are: the segmented shear wall approach and the perforated shear wall approach. The segmented shear wall approach uses only full height segments to resist shear; each individual segment must be designed to resist the shear and overturning force induced by the lateral load. The perforated shear wall approach uses both full height segments and segments around openings to resist shear; the wall as a whole is used to resist shear and overturning forces induced by the lateral load. This report examines one-, two-, and three-story timber buildings located in three different wind regions: a) 115 mph, b) 140 mph, and c) 160 mph. This report presents the design process for the MLFRS components and a comparison of the designs for each of the buildings. The purpose of this report is to determine how the design changes depending on the magnitude of the lateral load, the height of the building, and the approach used to design the shear walls.

Thesis (Ph. D.)--University of Missouri--Columbia, 2002. / "December 2002." Typescript. Vita. Includes bibliographical references (leaves 202-211). Also available on the Internet.

Tez (Yüksek Lisans) - Süleyman Demirel Üniversitesi, Sağlık Bilimleri Enstitüsü, Anatomi Anabilim Dalı, 2005. / Bibliyografya var.