Browsing by Subject "Structural analysis"

Now showing 1 - 3 of 3
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    Bridge Health Monitoring and Inspections – A Survey of Methods
    (Minnesota Department of Transportation, 2009-09) Gastineau, Andrew; Johnson, Tyler; Schultz, Arturo
    Since the collapse of the I-35W bridge in August 2007, bridge health monitoring has become an area of intense interest. This report defines terminology related to bridge health monitoring and provides a general glossary of available monitoring systems. The glossary is meant to help readers make an informed decision by understanding how different systems function and their strengths and weakness. The authors developed a questionnaire to send to commercial companies offering monitoring systems. Of the 72 questionnaires that were sent to commercial companies, 38 companies responded and are included in this report. From information provided with these questionnaires, available commercial systems are briefly summarized. Criteria for system evaluation were developed to help the bridge owner narrow down company choices for bridge application. After the owner answers a set of questions pertaining to a particular bridge, a program developed in Microsoft EXCEL helps the bridge owner decide the best system for a particular situation. An example is provided for program clarity. Once company choice is narrowed down, additional criteria were developed to aid in final product choice.
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    Development of a thin-layer chromatography based method for structural analysis of phosphatidylcholine (PC)
    (2015-09) Tan, Guiwei
    Structural analysis of phosphatidylcholine (PC) plays an important role in omega-3 fatty acids enriched products assessment, developing structured omega-3 fatty acids– containing PC, metabolic processes studies and diseases diagnosis. In this thesis, a new positional analysis of PC is described. Its methodology is based on a smart connection between two-dimensional chromatography and in-situ enzymatic hydrolysis. Most characterizations of PC composition happened on a thin layer chromatography (TLC) plate. Firstly, PC was isolated from total lipids by TLC and its purity was confirmed by high performance liquid chromatography (HPLC). Without further extraction from the TLC plate, PC was hydrolyzed by phospholipases on the plate directly. The key step of the in-situ enzymatic reaction was to promote interactions between PC and phospholipases, because this in-situ enzymatic hydrolysis occurred on a silica gel matrix. These increases can be accomplished via adding a wetting agent consisting of chloroform/ methanol/ water (65:24:4, v/v/v) onto the reaction area. Free fatty acids (FFAs) released from different positions of PC were then isolated from products mixture by second-dimensional chromatography and were chemically transesterified into fatty acids methyl ethers (FAME). With help of gas chromatography- flame ionization detector (GC-FID), the presented method could reveal relative percentage of each fatty acid on sn-1 and sn-2 positions of PC with 91.59% and 84.80% accuracies, respectively. Therefore, separation of PC from total lipids, enzymatic conversion of PC to FFAs and lysophosphatidylcholine (LPC), and separation of FFAs from products mixture can be performed on one TLC plate. This will remove the need to extract the separated PC from the TLC plate for the enzymatic reaction, avoid the risk of losing materials during the extraction processes; saving time, labor and cost.
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    Development of Flexural Vibration Inspection Techniques to Rapidly Assess the Structural Health of Rural Bridge Systems: Phase II
    (Minnesota Department of Transportation, 2009-12) Brashaw, Brian K.; Vatalaro, Robert J.; Wang, Xiping; Verreaux, Matthew; Sarvela, Kevin
    Current timber bridge inspection procedures used in Minnesota and across the United States are mostly limited to visual inspection of the wood components. Use of advanced techniques like stress wave timing, moisture meters, resistance drills will significantly improve the reliability of the inspections but these inspection techniques are time consuming. The objective of this project was to conduct vibration testing of dowel laminated timber bridge systems to better understand the potential for using vibration testing to assess the structural health and condition of bridges in Minnesota. A second key objective was to improve and automate the vibration testing system that is currently being used. This research showed that the forced vibration system developed is an effective tool for conducting forced vibration tests of timber bridges and that there is a noted increase in frequency during each successive stage of construction. A reliable means for assessing the peak frequencies and an identification of the mode still needs to be developed for this system to use the vibration response to predict the EI product for use in load ratings. Each bridge has a unique set of vibration characteristics that were identified using the automated system. These characteristics showed peaks in amplitude as the frequency of the vibration was increased from 0 - 35 Hz during testing. It is believed that monitoring of the characteristic vibration response for each bridge would be a means of identifying changes in structural health over time due to wood decay, accidents, vandalism, or lack of maintenance.