Experimental Investigation Of Reinforced Concrete Bridge Piers Under Blast Loading

Bridge structures play an important role in a transportation system, the potential risk of blast attacks to bridges thus has been increasing quickly in recent years. For a bridge structure, bridge columns are more likely to experience blast loading, and once the bridge column failure occurs, severe losses in terms of national security, economic, and socioeconomic would be brought as a consequence. There is therefore a need to investigate the blast-resistance capacity of reinforcement concrete (RC) bridge columns. The main work of this paper is as follows:(1) The interaction between blast waves propagating in the air and RC brige columns were investigated using method of combined numerical simulation and blast testing. The distribution characteristics of overpressure and impulse on the surface of columns have also been analysed in this paper.(2) Five main parameters were taken into consideration during the experimental design including section area, type of concrete, column geometry, type of transverse reinforcement and axial compression ratio. And 11 columns were constructed and tested in the field. Combined with numerical simulation, dynamic response characteristics, damage mechanism and failure mode of columns were investigated under different scenarios including contact explosion and explosion with certain standoffs.(3) Damage assessment of reinforced concrete column under blast loading were conducted based on the method of equivalent single degree of freedom (SDOF).The main conclusions of this paper are as follows:(1) The interaction between blast wave and RC columns is significant and can not be ignored. For a middle-or far-field ground explosion, the distribution of overpressure and impulse along the column height is nonlinear; while that on both sides and the back face of column is approximatively linear along the column height. Based on the distribution of overpressure and impulse along the column height and cross section, the blast load model was determined, the eqution of relationship between measured overpressure and scaled distance was also obtained, which can be referred by engineers of blast-resistant structures.(2) For a contact explosion, punch failure is more likely to occur for RC columns, which means local damage is evident and serious, with numerous transverse cracks observed on the column body. However, although local damage is the dominant failure mode, the global dynamic response cannot be igored.(3) For non-contact explosion, columns with larger section area, steel fiber concrete, circular section, spiral stirrup and axial force performed better than benchmark column. But when it comes to contact explosion, columns with square section or axial force performed worse. When explosion with massive charge occur on the ground, shear failure will occur at the base of the RC column.(4) The pressure-impulse (PI) curve of RC column was established to evaluate the damage level under blast loading. Therefore, once the overpressure and impulse are determined for an explosion, the damage level of S1 RC bridge columns can be quickly evaluated, which can be reference for protective measures for bridge columns against blast loads.