Flexural behaviour of low-magnetic concrete beams reinforced with zero-magnetic steel bars

With the rapid evolution of low-magnetic environments in scientific research, military and quantum metrology, the development of high-performance zero-magnetic structures is imperative. To accommodate the need for low magnetic permeability, long-term durability and superior mechanical properties, a novel type of concrete beam is proposed, incorporating zero-magnetic steel bars and low-magnetic concrete with white cement as the cementitious material and quartz sand and stone as aggregates. Eight beams were designed and tested under flexural loading. The experimental parameters included steel bar type, sectional height and reinforcement ratio. It is confirmed that the moment-resisting mechanism and failure pattern of the proposed beams are analogous to those of conventional concrete beams. Due to the higher strength of zero-magnetic steel, the flexural capacity of low-magnetic beams is significantly enhanced under equal stiffness design conditions. The load-displacement curves exhibited a similar morphology to those of ordinary reinforced beam, but without distinct yield plateau. Consequently, low-magnetic beams demonstrated smaller maximum crack widths and superior crack resistance. Based on the influence of low-magnetic concrete microstructure and surface treatments of zero-magnetic steel bars, recommended parameter values were proposed for the stiffness calculation formula and maximum crack width calculation formula of low-magnetic beams. Comparing two methods for determining the yield point of low-magnetic concrete beams, the farthest point method was found to more accurately reflect the actual behavior of low-magnetic steel beams by considering the continuous yield characteristics of zero-magnetic steel. A finite element model was established based on material constitutive relationships, and its computational accuracy was verified.