Finite-Element Analysis of Cantilever Slab Deflections with ANSYS SOLID65 3D Reinforced-Concrete Element with Cracking and Crushing Capabilities

Abstract

This paper presents a finite-element (FE) study conducted to investigate the deflections of newly constructed cantilevered slabs built for a medical facility expansion. From the beginning of the construction stage, the deflections of the newly built cantilevers caused disputes among the owner, contractor, and the structural engineer of record. The study presented here was performed to understand whether the cantilevers were designed and built to conform to the governing codes. The cantilever deflections at three levels and their relative displacements were studied in detail for comparison with the measured values at the job site and code limitations. The mainstream structural engineering software programs predominantly used in structural engineering offices are generally run to identify the most critical load combinations, critical forces, moments, and deflections of structural members; however, a deflection study such as the one described here requires an extensive FE model created with comprehensive software like ANSYS to investigate the sequential loading of cantilever deflections. In ANSYS, the reinforced concrete behavior can be simulated with SOLID65 elements, which provide an excellent fit for representing the true stress-strain diagram of reinforced concrete. The FE modeling with ANSYS SOLID65 elements for flat slab cantilever deflections have not been discussed in detail in a technical publication before: This study fills that gap. The study not only covers the detailed FE modeling with SOLID65 elements, but it also compares the results with the measured deflections and code requirements. In addition, the study provides recommendations for avoiding excessive deflections in cantilevered reinforced concrete construction.