A Bilinear Residual Strength Model for Concrete Subjected to Fatigue Loads Based on Discrete Element Virtual Tests

Abstract Accurate assessment of fatigue residual strength is essential to ensure the safety and reliability of concrete structures given long-term fatigue loads. This study proposes a practical model for predicting concrete’s fatigue residual strength, which differs from conventional methods by being entirely based on data from virtual tests in the discrete element method (DEM) framework. A series of virtual tests using a fatigue damage model were conducted to obtain the residual strength of concrete at different maximum stress levels. These tests systematically captured the progressive deterioration of concrete given cyclic loading conditions. Based on these results, a bilinear residual strength degradation model was established, providing a clear mathematical representation of the strength evolution process. Compared with existing models, the proposed model demonstrates superior accuracy in predicting the degradation characteristics of residual strength, with results consistently biased toward safety for conservative engineering applications. Moreover, it clearly indicates key inflection points in residual strength evolution, which is of great significance for structural safety assessment. The identification of these critical transition phases enables more precise monitoring and maintenance planning for concrete structures subjected to repetitive loading, ultimately contributing to enhanced durability and risk management in structural engineering practice.