Integrative numerical and analytical approaches to bond strength in lightweight concrete: Innovative modeling and parametric insights for ribbed steel bars and seven-wire strands

This study explores the bond behavior between steel reinforcement and lightweight concrete (LWC), focusing on ribbed steel bars and seven-wire strands. Utilizing finite element (FE) analysis with ATENA 3D and ATENA-GiD software, along with analytical methods, the research examines the impact of bar diameter and concrete compressive strength on bond strength. Forty-two FE models were created to simulate pull-out tests, validated against experimental data and existing design codes. The investigation covers ribbed steel bars and seven-wire strands with diameters ranging from 8 to 17.8 mm, embedded in LWC with compressive strengths from 35 to 80 MPa. The study proposes a new empirical equation for predicting bond strength, highlighting that bond strength improves with higher concrete compressive strength but decreases with larger bar diameters. Notably, ribbed steel bars exhibit approximately double the bond strength compared to seven-wire strands in LWC. The findings provide valuable insights for optimizing the design of reinforced concrete elements in LWC, balancing reinforcement diameter and concrete strength for enhanced structural integrity.