جستجوی مقالات مرتبط با کلیدواژه « Bridge » در نشریات گروه « پدافند غیرعامل »

The design of elements under blast load came to the attention of scientists after World War II. Extensive research has been done in the last fifty years on the behavior of structures against blast loads and their reaction. Due to the intensity and magnitude of blast loads, it is important to carry out the most appropriate scheme in terms of economics and safety for a structure. If the design is not done correctly and with the right criteria selected, it may impose exorbitant costs on the execution of a structure. The type of blast in this research is blast in the open air and unrestricted surface. A surface blast is a blast that occurs at a surface or at a very close distance to the ground. In this research, different methods of strengthening the column of concrete bridges under blast load will be investigated. The considered strengthening methods include changing the arrangement of the rebars on the cross-sectional area, increasing the amount of cross-sectional rebars, using FRP rebars and increasing or changing the geometric shape of the column cross-sectional area; Then the most appropriate, economical and safest strengthening scheme is selected and a suitable strengthening model for the above system is presented. The structural models studied in this research are investigated at an identical blast level (1000 kg TNT at 3 meters from the structure). The software used in analyzing the studied models is SAP2000 software. The results showed that some strengthening methods, such as increasing the amount of cross-sectional rebars, increase structural responses. Also, among the strengthening methods selected in the research, replacing FRP rebars instead of regular rebars in the reinforced concrete bridge columns is the most effective and the best method of strengthening these structures against the blast loads.

Bridges are important structures in a transportation system which may be one of the targets of terrorist attacks. Given the complexity of bridges against the blast, the purpose of this research is determining a suitable equivalent static load pattern for nonlinear analysis of composite steel deck bridges under the load of the blast. For this purpose, at first, the simulation of blast and modeling of bridges with composite decks have been performed and the accuracy of the proposed modeling method is evaluated. Then several samples of bridges with the composite deck under the load of the blast have been modeled with different intensities and nonlinear dynamic analysis is carried out on them. By proposing a suitable load pattern and after the nonlinear static analysis on all samples using displacement control, the equivalent static load factor to correct the desired pattern in each sample is calculated. Based on the results of the nonlinear analysis of the samples, a correlation for the equivalent static load factor is extracted and evaluated.