Numerical Investigation of Cast-in-Place Anchor Pullout Strength Regarding CCD Methodology

Ensuring an adequate development length is a fundamental requirement for attaining the specified yield strength in concrete structural elements. This study investigates the tensile load response of cast-in-place headed anchor bolts, incorporating pullout strength data into the analysis. To facilitate this, an elasto-plastic concrete model is developed and integrated within the LS-DYNA simulation framework. Initially, the reliability and precision of the proposed model are verified through comparison with existing pullout test results. Subsequently, the framework is employed to assess the tensile performance of headed anchor bolts with varying embedment depth-to-diameter ratios. In this study, the parametric analysis includes several plain concrete slabs with varying compressive concrete strengths, anchor diameters, embedded depths, and yield strengths of steel. Observations reveal a substantial deviation in pullout strength at the conclusion of the monotonic loading steps when compared to the predictions of the Concrete Capacity Design (CCD) method. As the embedment depth-to-anchor dimension ratio decreases and the concrete strength increases, the discrepancy between the observed results and the CCD method predictions becomes significantly more evident. The CCD method underpredicts the concrete breakout capacity of anchor bolts embedded in plain concrete slabs with compressive strengths of 30 MPa and 40 MPa, whereas it overpredicts the capacity for concrete with a compressive strength of 20 MPa. The findings of the numerical investigation, which accounted for concrete strength, steel yield strength, and the embedment depth of cast-in-place headed anchors in unreinforced concrete slabs, led to the recommendation of a coefficient for estimating embedment depth as a function of anchor dimensions.