Investigation of Performance Prediction of Blast Loaded Concrete Flexural Members Reinforced with High-Strength Bars

Abstract

This study investigates the use of high-strength reinforcements (ASTM A1035 Grade 100) instead of conventional reinforcement (such as ASTM A615 Grade 60) in a blast-resistant reinforced concrete flexural member. The stress-strain curve of an ASTM A1035 Grade 100 steel differs from conventional grade 60 steel. Grade 100 steel possesses higher strength and an unclear yield threshold. When designing a flexural member to resist blast loading, its resistance function is typically developed utilizing the Unified Facilities Criteria (UFC 3-340-02) manual. The UFC approach simplifies the behavior of steel reinforcement to an elastic portion up to the yield point, followed by a perfectly plastic plateau. With the absence of a clear yield point in high-strength steel, this simplification may not be well represented. The dynamic performance for flexural concrete members reinforced with high-strength steels is developed using the generalized single-degree-of-freedom (SDOF) system. The SDOF performance generated with the simplified approach is compared with a more realistic resistance function of the system obtained by a computational model established with the virtual work principle and the moment curvature of a section. The results indicated that using the UFC approach for the high-strength steel flexural member may require an adjustment factor in order to reach conservative predictions when the reinforcement ratio is between 0.4% and 2%. The results also illustrated a 50% reduction in the area of steel reinforcement when using grade 100 instead of grade 60, indicating less steel congestion in the high-strength reinforced cross-section.