Evaluating the behavior of notched connections in timber-concrete composite beams

The existing design procedures for timber-concrete composite (TCC) beams typically rely on pushout tests or simplified analytical methods developed from pushout tests to estimate the capacity of notched connections. However, these methods do not account for the differences in loading conditions and stress distributions between pushout tests and actual beams. In addition, there is limited guidance on optimizing the design of notched connections in TCC beams to enhance structural performance at ultimate load. This study addresses these gaps through both numerical and analytical modeling of notched connections. A detailed finite element (FE) modeling approach is developed and validated against experimental results from various TCC beam and pushout tests. Following validation, an extensive parametric study is carried out to assess the influence of key design parameters, such as notch geometry, spacing, location, and material properties, on connection effectiveness and beam behavior. Corresponding pushout models are also developed to evaluate the reliability of pushout tests in predicting connection capacity in beams. The use of FE analysis enables direct comparison of connection behavior between pushout and beam models. Based on the results of over 100 case studies, strength modification factors are proposed to adjust pushout capacities to more accurately represent connection behavior in TCC beams. These factors are incorporated into a previously developed simplified analytical method, improving its prediction accuracy and extending its applicability. The findings provide practical guidance for designing more reliable and efficient notched connections in TCC beams.