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AbstractReinforced concrete members under impact loading stress may be destroyed in a split period. Because of the need to investigate the impact resistance of reinforced concrete members, this issue remains a much-debated topic. This study investigates the response of reinforced concrete (RC) square members under an unequal lateral impact force. The performance of RC members under the effect of impact load is examined using a drop hammer impact test system. The importance of unequal lateral impact load is highlighted and addressed by examining RC members’ failure mode and dynamic response characteristics. Four types of RC members are experimentally investigated in detail. A finite element method (FEM) modeling is proposed to predict the impact responses of the RC members. Moreover, the effects of the impact position, height, and hammer mass on the dynamic response characteristics under an impact force are evaluated. The predictions of the proposed numerical model are validated against experimental results, emphasizing impact force history, deflection time history, and failure modes. Results indicate the viability of the FEM model. The findings from the experimental and numerical studies can improve the impact-resistant performance of reinforced concrete members.

A design of broadband dual-polarized antenna with low cross polarization and high isolation was presented. The antenna is composed of a cross dipole, a folded ground, two feeding networks, and a reflector. The impedance bandwidth was enhanced by utilizing the mutual coupling between the two dipoles. A kind of meandering folded Marchand balun was skillfully integrated on the support column of the antenna to excite the dipole differentially, which can deliver both balanced (within 0.5 dB) power splitting and consistent (±5°) phase shifting from 1.71 GHz to 2.17 GHz. The standing wave ratios (SWRs) of each port are less than 1.5. By using this feeding network, the antenna has good performance in isolation (> 45 dB) and cross polarization (> 30 dB) over the entire operating frequency band. Moreover, the gain (∼8.6 dB) of the proposed antenna is stable with frequency and the antenna structure is very firm due to the support column. The proposed antenna can be easily formed an array for digital cellular system (DCS), personal communications service (PCS) and 3rd generation (3G) applications.