BEHAVIOUR OF PLAIN AND REINFORCED CONCRETE UNDER HIGH RATE LOADING - NUMERICAL SIMULATION

摘要

The response of structures and structural elements made up of concrete or other quasi-brittle materials is known to be significantly influenced by the rate of loading with respect to time. In general, with the increase in the loading rate, the nominal resistance of the concrete structure or specimen increases but at the same time the failure modes tend to become brittle. The response of concrete is influenced by the rate of loading through three different mechanisms namely, creep of bulk material between the cracks (most influential for slow loading rates); rate of crack propagation (most influential for medium loading rates) and structural inertial forces (most influential for high loading rates). In recent past, a new formulation has been developed where the rate sensitivity has been considered in the framework or microplane model with relaxed kinematic constraints and the same has been implemented in the 3D finite element code for macroscopic space analysis of concrete structures. In this work, an attempt is made to numerical simulate the response of concrete specimens, structural elements, sub-assemblages and structures when subjected to various loading rates. The analysis is performed with the Macroscopic Space Analysis program, MASA, using the three dimensional finite element formulation based on the theoretical framework of continuum mechanics and irreversible thermodynamics. The analysis has been performed for various kinds of geometries starting from a compact tension specimen, simply supported beams with different shear reinforcements, plain and reinforced concrete slabs and beam-column joints. It has been shown that the formulations and procedure followed in this work can be effectively utilized to predict the response of concrete structures under different loading rates. The effects of loading rate on the response of different kind of structural elements are discussed.