Influence of concrete material ductility on the behavior of high stress concentration zones.

The thesis focused on the development of a comprehensive understanding of how concrete material tensile ductility influences the structural performance of high stress concentration zones and the translation of this understanding into design guidelines for the advantageous use of such material in stress concentration zones. The ductile concrete material investigated is Engineered Cementitious Composites (ECC) which represents a unique class of high performance fiber reinforced cementitious composites featuring high tensile ductility and low fiber content due to a micromechanics design approach. The influence of concrete material ductility on the behavior of high stress concentration zones was first investigated experimentally via three case studies which vary in the loading mode (tensile or shear, monotonic or fatigue loadings), type of stress concentration (steel/ECC interaction, concrete crack/ECC interaction), and also material properties (tensile ductility, compressive strength). Building upon these case studies, the fundamental damage, load redistribution and reflective cracking resistance mechanisms with ECC in stress concentration zones were further clarified and demonstrated by numerical and/or experimental approach. Based on the solid understanding of these fundamental mechanisms, design guidelines for ECC/anchor connection, ECC/stud connection in link slab transition zone, and ECC overlay are established for the advantageous use of ECC material in civil infrastructures where high stress concentration often exists. This research established experimentally and numerically that ECC material ductility can overcome many of the current limitations of normal brittle concrete where high stress concentrations may be induced inadvertently. Through various mechanisms, several demonstrated with specific case studies in this thesis, enhanced structural load capacity and ductility, energy dissipation, and fatigue life can be achieved with intrinsic material ductility. As a result, material ductility is shown to contribute directly to structural safety and durability, as well as to lessening environmental burden by reducing the need for maintenance of infrastructure.PhDApplied SciencesCivil engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/126801/2/3276272.pd