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Although design codes have accepted lightweight concrete as a suitable structural material for nearly 50 years, there is still a good deal of uncertainty as to how to calculate the strength of this material when designing for shear in beams.  Design codes tend to penalize lightweight concrete due to its lower tensile strength and smoother interface along the shear cracks.  In this study, there were twelve tests on six full-scale, prestressed girders with composite decks designed to provide answers to some of those uncertainties.  The variables considered were concrete density, concrete compressive strength, effective shear depth, shear span-to-effective depth ratio, the amount of shear reinforcement, and the composite cross-sectional area.  Results show that the sand-lightweight concrete girders exceeded the expected shear strength according to the 2010 AASHTO LRFD Bridge Specifications.  Compared to normal weight concrete, sand-lightweight concrete performed reasonably well, and therefore, does not need a lightweight modifier when designing for shear.  However, a reliability analysis of the sand-lightweight girders in this study as well as twelve previous experiments indicate that there should be two different strength reduction factors for the shear design of sand-lightweight concrete depending on which shear design procedures are used in the 2010 AASHTO LRFD Bridge Design Specifications.  For the General Procedure as well as the guidelines outline in Appendix B5, the strength reduction factor should be increased from 0.70 to 1.00.  For the Simplified Procedure, that factor should be 0.75. / Ph. D.

Ultra high performance concrete, specifically Ductal® concrete, has begun to revolutionize the bridge design industry. This extremely high strength material has given smaller composite sections the ability to carry larger loads. As the forces being transferred through composite members are increasing in magnitude, it is vital that the equations being used for design are applicable for use with the new materials. Of particular importance is the design of the horizontal shear reinforcement connecting the bridge deck to the top flange of the beams. Without adequate shear transfer, the flexural and shearing capacities will be greatly diminished. The current design equations from ACI and AASHTO were not developed for use in designing sections composed of Ductal® and Lightweight concrete. Twenty-four push-off tests were performed to determine if the current horizontal shear design equations could accurately predict the horizontal shear strength of composite Ductal® and Lightweight concrete sections. Effects from various surface treatments, reinforcement ratios, and aspect ratios, were determined. The results predicted by the current design equations were compared to the actual results found during testing. The current design equations were all found to be conservative. For its ability to incorporate various cohesion and friction factors, it is recommended that the equation from AASHTO LRFD Specification (2004) be used for design. / Master of Science

Single plate shear connections are designed to have sufficient strength to resist the shear force and moment transferred from the beam. The connections must also provide sufficient ductility to allow the beam end to rotate freely. In the United States the current recommended design method is found in the AISC 13th Edition Steel Construction Manual (2005b). The limited experimental work which led to the current method necessitated additional single plate shear connection investigations. This paper summarizes the results and analysis of eight full scale single plate shear connections tested at Virginia Polytechnic Institute and State University. The test setup consisted of a test beam attached to a test column with a single plate shear connection at one end and supported by a roller at the other end. The single plate was welded to the column flange and bolted to the beam web. Load was applied to the test beam at third points until failure of the connection or test beam. The current design method used in the United States was examined with respect to the connection tests performed. In particular, the ultimate shear strength and the rotational capacity were investigated. Suggestions are made regarding changes to the method and further research. / Master of Science

The effect of door and window openings on long timber framed shear walls was the subject of this thesis. Four different wall configurations containing various openings and one control wall with no openings were tested to examine ultimate load capacity and stiffness. All walls were forty feet in length and contained tie-down anchorage at the extreme ends of the wall only. Two replications of the five wall configurations were built. Each of the five wall configurations was tested using a: 1) monotonic displacement pattern and 2) sequential phased displacement pattern. A better understanding of the effect of monotonic and cyclic loading (and the relationship between the two loading types) on ultimate load capacity and stiffness for a given wall configuration were examined. To efficiently design shear walls, the effect of openings on shear wall performance must be known. This thesis adds to previous work on shear walls with openings to provide valuable information for future use. Results from this investigation are intended to provide useful information regarding performance of long shear walls with openings. Data concerning capacity, drift, elastic stiffness, and ductility are presented. Two methods of capacity prediction of shear walls with openings are examined. Sugiyama (1994) provided an empirical equation for prediction of load resistance that has been applied to capacity and is the basis for the perforated shear wall method. This thesis further validates his work to full scale long shear walls. A new method for capacity prediction was developed by the author and is also presented. / Master of Science

In this thesis, a new traction stress based method for characterizing shear strength is investigated by carrying out a series of shear strength tests. The AWS method for the calculation of shear strength shows significant discrepancies between longitudinal and transverse specimens. The main purpose of this new traction based definition for shear strength is to demonstrate that there exists a single shear strength value regardless of specimen geometry and loading conditions. With this new approach a better correlation between shear strength values for transverse and longitudinal specimens is achieved. Special issues occur with the multi-pass welds in regards to the failure angle. The AWS equation does not account to different failure angles of the specimens, it only assumes 45o failure angle in all the cases, but the new approach takes into account the different failure angles. Finally with this method a quantitative weld sizing can be achieved for fillet welds.

This Masters Thesis describes the continuation of the Snow Probe development. The focus of this project was to establish the rotational shear vane as a useful tool in avalanche safety work as well as develop a robust method for measuring the applied torque. A new and novel way of measuring the torque on a rotational shear vane has been developed to illustrate its effectiveness. The new system measures the power supplied to a cordless drill to get an indication of the applied torque. This was done because it was found that the earlier method of using a strain gauge/cantilever system repeatedly failed to work, largely due to complexity. The snow probe in its present embodiment has been shown to provide a good clear indication of the snow profile under easily repeated circumstances. Shear strength results are at this stage not sufficiently for reliable quantitative results. However the probe in its present form is able to give pictorial impressions of the snow pack that compare well to current hand hardness profiles derived from snow pit methods. Even in its current form the snow probe is able to collect useful snow profile data in a matter of minutes, much quicker than conventional snow pit methods. A loose relationship was found to exist between the approach angle of a shear vane blade and the clarity of the snow profile. These relationships are relatively inaccurate at present due to lack of rotational velocity data and therefore pproach angle data. It is believed that the addition of a rotation counter would greatly increase the accuracy of the probe results and enable a shear strength profile to be quantified. Further developments and testing are underway with a view to forming a company around the snow probe.

Plate girders are fabricated in situations where standard structural shapes do not possess the required strength necessary to carry applied loads. In many instances, plate girders are tapered so that the resistance to bending is proportional to the bending moment, creating cost effective, aesthetically pleasing structures. The AISC 2010 Specifications accurately predict the flexural capacity of tapered plate girders but recent research has suggested that the required shear strength is overly conservative. The researchers postulate that the required shear strength is overly conservative due to an effect known as modified shear that has been neglected from the AISC 2010 Specifications but has been suggested by several authors. This research investigates both analytically and experimentally, tapered member ultimate shear strength considering a “modified” and “unmodified” applied shear approach. A new design formula introduced by Lee et al. (2008) will be used in conjunction with the AISC 2010 Specification in making ultimate shear strength comparisons. A total of 12 specimens are tested to failure, ten tapered and two prismatic built-up plate girders.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 62-64). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 58-60). Also available on the World Wide Web.