This thesis presents three new three-dimensional constitutive models for cementitious materials. All three models use embedded damage planes and adopt the theory of contact mechanics to describe the characteristic behaviour of cracks formed in concrete and other cementitious materials. The first of these is a smooth frictional contact model which incorporates a simplified Mohr-Coulomb yield surface to capture plastic slip planes in concrete. The aim of the model is to accurately represent the behaviour of smooth construction joints in large concrete structures. The second proposed model is the dual-surface contact model. The model employs two contact surfaces, each of which nominally represents a different component of concrete composite, i.e. coarse aggregate particles and mortar. The third model is the 'embedded planes with local plasticity contact' model (EPLPC). The model adopts a yield surface, which is similar to the damage surface in strain space, to capture plastic embedment on crack surfaces. This model, as with the dual-surface contact model, is developed to simulate crack opening-closing, as well as the behaviour of aggregate interlock. The models are integrated with a hardening/softening frictional plasticity component that uses a smoothed triaxial plastic yield surface developed from that used by Lubliner et al. (1989). Each of the proposed models is implemented with a consistent tangent stiffness operator and return mapping algorithm, similar to that of the Closest Point Projection algorithm. The models are coded in Fortran77 and implemented in a constitutive driver program, and also a finite element software package LUSAS. The models are assessed using a series of stress/strain paths at the constitutive level, and also validated against a range of experimental data. These include data from uniaxial and multiaxial compressive tests, uniaxial tensile tests with and without unloading-reloading cycles, and also tests in which shear load is applied on open cracks.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:583813 |
| Date | January 2006 |
| Creators | Hee, Siew Chang |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/55157/ |
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