Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Bibliography: leaves 140-141. / by Chin Pang Wong. / M.S.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / by Michael Peter Manahan. / Sc.D.

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In the course of studying the effects of programming in multiple languages, we unearthed troubling trends in SourceForge artifacts. Our initial studies suggest that programming in multiple languages concurrently negatively affects developer productivity. While addressing our initial question of interest, we discovered a pattern of monolithic commits in the SourceForge community. Consequently, we also report on the effects that this pattern of commits can have when using SourceForge as a data-source for temporal analysis of open source projects or for studies of individual developers.

<p>Structural walls in existing buildings designed to pre 1970s codes may have deficient shear reinforcement and lap splice detailing. Lap splices at the bottom of the walls were designed in compression with anchorage length of 24-bar diameter. When the structural wall is subjected to lateral loads during a major seismic event, the lap splice is in the zone of maximum moment and shear and may be subjected to tension. Such design may cause nonductile behaviour and sudden failure of the wall due to shear or bond slip of the lap splice reinforcing bars. The effect of shear and ductility rehabilitation on the behaviour of reinforced concrete structural walls, without lap splice, have shown improvement in the structural wall shear resistance and ductility and hence overall structural ductility and seismic loads resistance. Research on rehabilitation of reinforced concrete (RC) structural walls with both deficient shear reinforcement and lap splice detailing is still needed. </p> <p> The principal objectives of this study were to evaluate the seismic behaviour of non-ductile reinforced concrete structural walls before and after rehabilitation using carbon fibre reinforced polymers (CFRP). These objectives were achieved through experimental and analytical investigations.</p> <p> The experimental phase of this research involved testing large scale models of RC structural walls with deficient shear strength and lap splice detailing to reproduce failure modes observed following major seismic events and to evaluate the rehabilitation schemes. Ten RC structural walls were built and tested under cyclic loading. Three control walls were tested as-built with non-ductile detailing and seven walls were rehabilitated before testing. The purpose of the rehabilitation techniques was to prevent brittle failure in shear or bond slip and to improve the ductility and energy dissipation of RC structural walls.</p> <p> The analytical phase of this study involved evaluation of the inelastic dynamic response of RC residential building with nonductile structural walls as well as retrofitted walls. An efficient macroscopic model to represent the behaviour of RC structural walls when subjected to pushover, cyclic and dynamic seismic loads was developed. The proposed model was intended to adequately describe the hysteretic behaviour of walls and to be capable of accurately predicting both flexural and shear components of inelastic deformation. The model predictions were compared with the experimental results. The comparisons showed that the developed analytical model predicted the inelastic walls response with a good accuracy. The analytical model was capable to evaluate the nonlinear dynamic behaviour of an existing building under seismic excitation before and after rehabilitation.</p> / Thesis / Doctor of Philosophy (PhD)

<p> The behavior of concrete block walls subjected to vertical compressive loads with out-of-plane eccentricities was investigated both experimentally and analytically. Particular attention was devoted to the effect of wall slenderness on capacity.</p> <p> In the experimental study, 14 full scale walls and numerous small specimens were tested to provide complete and reliable data concerning the behavior of concrete block walls and its components. Plain walls and partially grouted reinforced walls were tested in symmetric single curvature under compressive loads with out-of-plane eccentricities. Reinforced walls were tested in pure bending, as well.</p> <p> Prisms were tested to analyze the behavior of concrete masonry in compression with no slenderness or eccentricity effects. Bond tests were carried out to determine the behavior at interfaces of grout and steel reinforcing bars as well as between mortar and concrete blocks. Material tests were conducted to determine the mechanical properties of the blocks, mortar, grout and steel reinforcement used.</p> <p> A two-dimensional finite element model for the vertical cross section of block masonry walls was developed. It is capable of modeling local failure modes such as cracking, crushing and debonding. Material properties of the concrete blocks, mortar, grout, and steel bars were treated individually. The large deformation analysis allowed for consideration of the slenderness effect. The model was verified through comparison with experimental results. Fairly good agreement was obtained.</p> <p> The material properties of specimens tested during the experimental investigation were the basis of a parametric study. Results of this study were used to investigate the effect of the wall slenderness and the eccentricity of applied loads on the capacity of concrete block walls. They were used to evaluate the current provisions in the Canadian Masonry Code, CAN3-S304-M84. An attempt was made to develop original design equations based on the reduction coefficient approach. The proposed equations for plain and reinforced blockwork were shown to provide more consistent predictions of capacity than current design methods.</p> / Thesis / Master of Engineering (MEngr)

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