یک رویکرد نظری در مورد تیر بتن مسلح پیش تنیده خارجی ضد انفجار
Abstract
1- Introduction
2- Dynamic resistance model
3- Theoretical approach to dynamic responses of EPC beam
4- Verification of the theoretical approach
5- Parameter discussion
6- Conclusions
References
Abstract
Externally prestressed reinforced concrete (EPC) is employed in long-span civil infrastructure, and a simplified dynamic analytical method is required to evaluate the blast-resistant performance of these EPC components. A theoretical approach is proposed that combines the elasto-viscoplastic rate-sensitive model with an improved layered-section method to predict the dynamic responses of EPC beams subjected to blast loadings, based on an equivalent single-degree-of-freedom system. A corresponding calculation program is compiled on the MATLAB platform. The proposed approach and the compiled program are validated by application to existing static and blast testing data, as well as the corresponding finite element calculation results. Three key parameters—the conventional reinforcement ratio ρs, the prestressing reinforcement ratio ρp, and the span-depth ratio l/h—that significantly affecting the dynamic responses of the EPC beam to explosion are discussed, providing useful design insights. The analytical results indicate that the determination of the three affecting parameters should be balanced to achieve a higher blast resistance in designing the EPC beam.
Introduction
External prestressing is a technique in which concrete structural members are prestressed longitudinally using tendons located entirely outside the concrete section. This technique is widely used to strengthen or rehabilitate existing concrete structures and in the construction of new concrete structures because of its superiority compared with other conventional prestressing techniques [1]. The advantages of external prestressing tendon systems include their easier tendon layout and placement, better corrosion protection, and significant contribution to restricting the deflection of long-span structures [2]. Furthermore, externally prestressed reinforced concrete (EPC) structures can potentially resist explosion, and are therefore used in key civil infrastructure, particularly in long-span concrete structures. Because of the ubiquity and importance of the external prestressing technique, the associated static behaviors have been intensively studied, including in engineering applications. The use of external prestressed tendons increases the load-carrying performance of beam components, which has been confirmed both theoretically and experimentally [3–7]. The load-bearing capacity is influenced by several factors, researchers have paid much attention to study the effects of these factors. Aparicio et al. [8] tested five monolithic and three segmental EPC beams in bending failure and in combined bending and shear failure. They observed that reducing the length of the tendon will increase the ultimate load-bearing capacity. Lou et al. [9] and El-Ariss [10] studied the flexural behavior of EPC beams, the results showed that high span-to-depth ratios led to a significant decrease in the eccentricity and therefore resulted in reduced rigidity and lower flexural capacity. The setting of the external tendons has a great influence on the load-bearing capacity of structures. Ghallab and Beeby [11] found that the ultimate stress in the external tendon was slightly affected by the internal bonded steel ratio, and was significantly affected by the value of the prestress, the number of deviators, the concrete strength, and the ratio of the distance between deviators to the span. Cao et al.