Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 241-244).

This thesis presents the results of a theoretical and experimental study of the lateral buckling of straight beams of rectangular cross-section resting on columns, a type of structure commonly found in the roofing system of multi-bayed buildings. The structure is analyzed as a simply supported beam, uniformly loaded, restrained at one end against longitudinal torsion and resting near the other end on a flexible column which may provide various torsional and lateral restraints. Beyond the column is a cantilevered projection of various lengths and loads. The entire top edge of the beam is considered as fastened to a continuous decking which restrains it against horizontal displacement but permits free rotation about this edge. The method of solution of the theoretical lateral buckling load is by using a computer program to calculate the structure stiffness matrix's determinant at increasing load levels, and a plot of the determinant versus load level yields the critical load (at determinant equals zero). This theoretical approach is verified by model experiments in the laboratory. Design curves and equations are produced incorporating the usual flexural beam and axially loaded column strength concepts, with lateral buckling considerations. Recommended design code procedures are forwarded based on these curves which would permit more economical use of deep beams. Included in the thesis is the computer program listing used in the solution technique. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The fracture problem due to the singular stresses arising from the sudden change of geometric properties around cracks and notches was studied both analytically and experimentally. The failure models of the cracked and the notched specimens were derived by using linear elastic fracture mechanics methodology, which led to the determination of the critical stress intensity factors. Experiments were conducted to determine fracture toughness for different modes as well as the effect of variations in the crack-front width, specimen size and moisture content. Subsequently, failure surfaces for cracks and notches were developed based on the experiments undertaken, describing in each case the interaction between mode I and mode II fracture toughness. To verify the reliability of these experiments, the results obtained were compared with the published literature. As an application, design curves for a 90 degrees-cracked beam and a 90 degrees-notched beam are presented. These curves allow the prediction of the failure loads due to the rapid crack propagation under different loading conditions. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Failure of pitched-tapered glulam beams in tension perpendicular to grain has been attributed to the inadequacy of the present method of calculating stresses. In this thesis, the factors of time and size for tension perpendicular to grain were investigated to determine how they would affect the allowable stresses. A total of 229 Douglas Fir glulam blocks of two sizes were loaded for ?0 days in uniform tension perpendicular to grain to investigate time effect. Test data were analyzed by developing estimates for the strength ratios. Results indicate that strength reductions increase at an increasing rate with the logarithm of time. The presently used time factors were shown to be conservative and could be increased for the 2-month, the 7-day and the 1-day durations. Experimental data also indicate that the present time factors may be non-conservative for load durations less than 5 minutes and more than ?0 days. In addition, short-term testing of 24-0 Southern Pine glulam blocks of three sizes was performed to investigate size effect. Results show that the relationship between specimen strength and volume is a straight line in a log.-log. plot, thus verifying the weakest-link model for Southern Pine. Comparison with Douglas Fir data taken from literature was also made. It was found that Southern Pine is definitely stronger than Douglas Fir In tension perpendicular to grain. Size effect, however, is almost identical for the two species. Significant difference was observed in the long-term test results between the two specimen volumes. This may be due to the effect of size, but it could also be caused by the different stress levels used for the two volumes. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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Yes / Twelve reinforced-concrete continuous deep beams having web openings within interior shear spans were tested to failure. The main variables investigated were the opening size and the amount of inclined reinforcement around openings. An effective inclined reinforcement factor combining the influence of the amount of inclined web reinforcement and opening size is proposed and used to analyse the structural behaviour of continuous deep beams tested. It was observed that the end support reaction, diagonal crack width and load capacity of beams tested were significantly dependent on the proposed effective inclined reinforcement factor. As this factor increased, the end support reaction and increasing rate of diagonal crack width were closer to those of companion solid deep beams. In addition, a higher load capacity was exhibited by beams having an effective inclined reinforcement factor above 0.077 than the companion solid deep beam. A numerical procedure based on the upper-bound analysis of the plasticity theory was proposed to estimate the load capacity of beams tested. Comparisons between the measured and predicted load capacities showed good agreement.

C.T.G. Looney proposed a method of solving the problem of steady-state forced vibration of continuous frames. Starting with the analysis of a single span, simply supported beam, the method was extended to continuous beams and frames. An investigation of his method was undertaken comparing experimental deflection with those predicted by Looney’s method. A single span beam and a two span continuous beam was used in the experiment. A mechanical shaker was used to vibrate the beam. The experimental and nautical curves showed good agreement with the experimental values being consistently higher. Although the weight of the shaker's moving parts was less than one-tenth the weight of the beam it had considerable effect in lowing the resonant frequency and increasing amplitudes. / M.S.