Browsing by Author "Asad-ur-Rehman Khan"
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- ItemRestrictedElasto-damage fatigue modeling of RC beams strengthened by CFRP(Saudi Digital Library, ) Asad-ur-Rehman KhanThe repair of understrengthened or damaged reinforced concrete (RC) members by external plate bonding of carbon fiber reinforced plastics (CFRP) laminates or plates is becoming increasingly popular in the construction industry. Prominent modes of failure in strengthened RC beams reported in literature are concrete crushing in compression, CFRP plate rupturing in tension and peeling of the CFRP plate due to high interfacial shear and peeling stresses at the plate cut-off point. In this study the fatigue behavior of RC beams strengthened by CFRP is modeled using continuum damage mechanics. Modeling of the overall system of strengthened RC beams requires individual modeling of the components that ultimately leads to failure i.e., concrete, CFRP and concreteCFRP interface. Component elasto-damage constitutive models are developed for concrete subjected to monotonic multiaxial and cyclic uniaxial tensile loading and concrete-CFRP interface subjected to monotonic and cyclic shear and peeling stresses using the data available in literature or derived during the course of the study. Concrete-CFRP interface is characterized experimentally by testing reinforced concrete blocks in shear and peeling, and the static and fatigue behavior of strengthened RC beams with or without end anchorages is investigated by testing strengthened RC beams in flexure. Numerical models are implemented in FORTRAN codes EDMON3D, EDMON3DS and EDCYC3D to predict the static and fatigue behavior of concrete, CFRP, concrete-CFRP interface and strengthened RC beams. Predictions are in good agreement with the experimental results available in literature or derived during the course of the study.
- ItemRestrictedThree dimensional finite element analysis of brittle materials using CDM model(Saudi Digital Library, ) Asad-ur-Rehman KhanIt is well documented that the major part of the nonlinearity in concrete is attributed to the development of microcracks and microvoids which tend to destroy the interface of bond between the cement matrix and aggregate and/or destroy the material grains and thus affecting the elastic properties. In the past two decades, the damage mechanics approach has emerged as a viable framework for the description of the observed phenomenological behavior of concrete such as material stiffness degradation, microcrack initiation and the strong directionality of DAMAGE. It is the objective of this thesis to incorporate a continuum damage model into a three dimensional finite element code (DAMAG3D) to predict the ultimate capacity and the overall response of structures made up of britle materials. The model is verified through the well-known Brazilian test, uniaxial compression test and plain concrete prism under strip loading. Numerical predictions are compared with the experimental results and the results predicted by other models.