Study and Design of Prefabricated Fiber Concrete Segments of Metro Tunnels Using with the Beam-Spring Method

The extension of used tunneling mechanized drilling machines (TBMs) in tunneling projects has led to the increased use of prefabricated concrete segments. The use of fiber concrete as a substitute for concrete reinforced concrete with regard to the improvement of concrete fiber performance and its cost-effectiveness is a subject in civil engineering. Arming reinforcements are effective against the stresses of concrete segments, such as concentrated forces that enter the segment during the construction process. On the other hand, fiber reinforced concrete is able to perform well against widespread stresses such as stresses caused by ground pressure and underground water. Due to the presence of both concentrated and extensive force, the pre-fabricated tunnel segments can be presented as a combination of reinforcement and fiber. In this research, according to the method presented in the ACI 544.7R instruction, the two-dimensional beam-spring modeling in the SAP2000 and the design of the structure of the tunnel under the transient loads and the segment's production stages, the transient loads in the steps Construction and permanent loads have been dealt with in the exploitation phase. According to the specifications of the project and the load applied to it, the concrete segment with 0.5% of the steel fibers alone was not responsive to the loads involved and the reinforcement was used to compensate for the resistance and the prefabricated concrete segment with the combination of reinforcement and steel fibers for designing it was proposed. Finally, the proposed model led to a 30% reduction in steel reinforcement consumption.