Abstract
Three-point bending experiments of concrete beams were conducted under the strain rate range of 10−6 s−1 and 1.5 × 10−3 s−1. A novel 3D laser scanner, Handy SCAN, was employed to detect the areas of interface, mortar and aggregate on the crack surface after the experiment. In this paper, the inhomogeneity of materials and the inertial effect were considered as the main factors in the strength enhancement of concrete together with a proposed dynamic model. With the obtained experimental results, the initial elastic modulus and tensile strength of concrete showed obvious rate sensitivity. Moreover, an empirical relationship of dynamic increase factor and strain rate was established for the strain rate range of 10−6 s−1 and 1.5 × 10−3 s−1. The contributions of aggregate and inertia effect to the dynamic enhancement of concrete strength were quantified with respect to the loading rate. The rate effect of concrete obtained by the experiments was verified by the finite element analysis on the mesoscopic scale with the model built by the three-dimensional random aggregate software.
Highlights
In civil engineering, concrete structures inevitably suffer from different type of dynamic loading during their designed lifetime, such as earthquakes
To investigate the dynamic strength enhancement of the concrete due to the loading rate, the the dynamic increase factors were observed through the experiment
The relation between the DIF and dynamic increase factors were observed through the experiment
Summary
Concrete structures inevitably suffer from different type of dynamic loading during their designed lifetime, such as earthquakes. Tall buildings and bridges may suffer from wind loading. Dynamic loading can cause the damage and collapse of these structures, which will lead to economic loss and major casualties. In the design of these structures, it is important to concern these loads, because they are unpredictable and destructive [4,5]. As a primary building material, concrete is rate-dependent, with its strength, stiffness and ductility subjected to the loading rate. In 1917, Abrams first observed that the concrete strength was sensitive to the loading rates in the compressive experiments with the strain rates of 8 × 10−6 s−1 and 2 × 10−4 s−1 [6]. The concept of the dynamic increase factor (DIF) was introduced to characterize the dynamic strength enhancement behavior and has been widely accepted, defined as the ratio of the dynamic strength to the quasi-static strength in the uniaxial compression or in uniaxial tension
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