Because of an interaction between the load history and the material's properties a reduction in the serviceability of safety of a structure may be seen as the result of a random process of damage accumulation with time. A damage model is proposed and verified to deal with this type of problem in general, and specifically with duration-of-load effects in timber structures. Through comparisons with and discussion of other damage accumulation models, the proposed model is found to be both suitable to represent experimental results and relatively easy to use. A reliability analysis for a single structural member with a service life of 30 years is studied for different snow loading conditions of three Canadian cities,using the damage model in combination with Rackwitz-Fissler's algorithm. A simplified analysis method is proposed and compared with a large-scale Monte-Carlo simulation. The results of the reliability analysis are found to be satisfactory. Finally, the implementation of the reliability analysis in a simple design guideline for load duration effects is discussed. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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published_or_final_version / Civil Engineering / Master / Master of Science in Engineering

In 1987, Congress authorized a 5 year $150 million dollar research program called the Strategic Highway Research Program (SHRP). SHRP was divided into four major areas, including the asphalt research program. The asphalt research program was divided into six major research contracts, one such contract, SHRP-003A was called Performance Related Testing and Measuring of Asphalt Aggregate Interaction and Mixtures. Oregon State University performed the portion of this contract related to the development and validation of accelerated test procedures for aging, low temperature cracking, and moisture sensitivity of asphalt-aggreagte mixtures. This thesis contains five independent papers that discuss elements of the development, validation, and or implementation of these accelerated test procedures. In the first paper, the relationship between field performance and laboratory aging properties of asphalt-aggregate mixtures is discussed, including the relative importance of asphalt binder and aggregate type on the amount of aging experience. Based on this work recommended aging procedures are presented to simulate different environmental conditions and pavement age. The second paper makes use of the large body of resilient modulus data conducted as part of the SHRP research effort to compare data obtain in the diametral and the triaxial mode. It is not possible to give a relationship between triaxial and diametral resilient modulus, without describing specimen geometry and other test conditions. The third paper discusses the effect of aging on the thermal cracking properties of asphalt-aggregate mixtures. The temperature at which aging occurs affects the way cold temperature fracture properties change with time. Low temperatures result in quenching of the aging process, while high temperatures result in continued aging. The fourth paper discusses work conducted in association with the Oregon Department of Transportation to extend the environmental conditioning system (ECS) test procedure for moisture assessment to open graded mixtures. Comparison in the ECS of mixtures with and without anti-strip agents added indicates that they don't always decrease moisture damage potential. The final paper presents a discussion of asphalt chemistry and its relationship to asphalt-aggregate mixture performance. Using the SHRP asphalt model, aging and low temperature performance data collected at Oregon State University is explained. / Graduation date: 1995

Testing of asphalt binders and asphalt-aggregate mixtures using dynamic mechanical analysis is becoming popular with improvements in high-speed computers, precision equipment, and computer software. Researchers are trying to describe the behavior of asphalt binders and asphalt-aggregate mixtures in terms of their time- and temperature-dependent linear viscoelastic behavior. The objectives of this thesis were to develop a simplified pneumatic test to perform dynamic mechanical analysis (DMA), to evaluate the performance of the pneumatic and hydraulic test systems using the computer software developed to perform DMA tests, and, to develop a simplified method to evaluate the experimental data obtained from DMA tests on aged asphalt-aggregate mixtures. A simplified pneumatic test system was developed to perform DMA. Computer software was also developed to perform DMA testing on both the simplified pneumatic and hydraulic test systems. DMA was performed on both test systems to compare their performance, and on aged asphalt-aggregate mixtures to evaluate the application of the simplified method. The results from the pneumatic and hydraulic test systems show that there is about a 20 percent difference in the complex modulus, especially at high loading frequencies. This is due to the compressibility of the air used in the pneumatic test system. The compressibility of air is greater at warmer temperatures than at cooler temperatures. Therefore, the application of the pneumatic test system to perform dynamic testing should be limited to low frequencies ( < 2 Hz), low temperatures ( < 25°C), and low load ( < 454 kg (1000 lbs.)) applications unless a modification can be made to increase the pneumatic cylinder's response time to match the hydraulic cylinder's response time. The simplified analysis method developed in this thesis divides the DMA results into four complex modulus and five phase angle parameters. These parameters describe the shapes of the master stiffness and phase angle curves and distinguished between the different asphalt-aggregate mixtures and the aging methods performed on the aged asphalt-aggregate mixtures. The phase angle parameters were reduced into two variables, peak frequency and peak angle, which vary with the aging of each asphalt-aggregate mixture. The peak frequency and peak angle decrease as the aging severity increases and the change of peak frequency and peak angle vary with the asphalt-aggregate mixture and aging treatment. Therefore, the complex modulus parameters and peak frequency and peak angle may be good indicators to describe how a master curve's shape varies with asphalt, aggregate, and aging type. / Graduation date: 1993

An analytical model for lateral deflection in cold-formed steel shear walls sheathed with steel is developed in this research. The model is based on the four factors: fastener displacement, steel sheet deformation, and hold-down deformation, which are from the effective strip concept and a complexity factor, which accounts for the additional influential factors not considered in the previous three terms. The model uses design equations based on the actual material and mechanical properties of the shear wall. Furthermore, the model accounts for aggressive and conservative designers by predicting deflection at different shear strength degrees.