Two-Way Slab Systems: Recent Developments and Showcases on Design, Analysis, Construction, and Evaluation Methods-Modeling of Reinforced and Fiber-Reinforced Concrete Slabs under Impact Loads (PDF)

Modeling of Reinforced and Fiber-Reinforced Concrete Slabs under Impact Loads (PDF)

Pdf Summary

This document outlines research conducted by Trevor D. Hrynyk and Frank J. Vecchio on modeling reinforced concrete (RC) and fiber-reinforced concrete (R/FRC) slabs under impact loads. The work addresses the need for improved impact-resistant infrastructure due to increased hazards and threats. Traditional modeling approaches have had limited success, prompting this study to explore alternative analytical methods.<br /><br />The researchers utilized a Shell Structure Analysis Program named ‘APECS’, developed by Polak and Vecchio, to simulate the behavior of concrete slabs under impacts. This method incorporates multilayered, thick-shell finite elements and employs the Modified Compression Field Theory (Vecchio and Collins, 1986) to handle complex structural responses like shear failures.<br /><br />The constitutive modeling for cracked concrete uses the Disturbed Stress Field Model (DSFM) by Vecchio, addressing variables such as compression softening, tension stiffening, and crack shear slip. A layered modeling approach is applied, which is useful for various concrete structures like non-planar shear walls and flat slab systems.<br /><br />Experiments involved subjecting test specimens to impact loads using drop-weight techniques with weights between 150 kg and 300 kg at velocities of 8 m/s. Results showed that the addition of steel fibers to RC slabs improved crack distribution and mitigated damage.<br /><br />For analysis, the study used stiffness proportional damping and strain rate effects derived from existing literature. Numerical results from the analysis provided close agreement with experimental data regarding displacement-time histories and deformation shapes.<br /><br />The DSFM-based shell element analysis effectively estimated the responses for RC and R/FRC slabs under high-mass, low-velocity impacts. While peak support reactions were less accurately estimated, the overall agreement between experiments and analyses was commendable, with mean computed-to-experimental ratios near unity, indicating strong model validity.

Keywords

reinforced concrete

fiber-reinforced concrete

impact loads

APECS

Modified Compression Field Theory

Disturbed Stress Field Model

drop-weight techniques

steel fibers

finite element analysis

structural response