دانلود رایگان مقاله انگلیسی ارزیابی لرزه ای پایه های پل بتنی مسلح شده دایره ای توخالی - تیلور و فرانسیس 2018

ABSTRACT

Experimental works in literature have paid proper attention to the seismic response of hollow circular piers only quite recently, despite their widespread use in existing bridges. More attention should be certainly paid to these elements to reliably assess their seismic capacity. Herein, experimental cyclic tests on two scaled reinforced concrete piers with hollow circular cross section, representative of typical existing Italian bridges, are carried out. Depending on the aspect ratio, flexure and flexure-shear failure modes have been observed. Design criteria, adopted setup, experimental response and damage evolution are presented and discussed. A focus on shear-critical piers has been performed, collecting a proper experimental database of tests from literature. The very few specific shear strength models existing in literature and main models by codes are compared with the collected data. Model by Ranzo and Priestley (2001), also in conjunction with proposal by Turmo et al. (2009), has finally shown promising results.

6 CONCLUSIONS

The present work provides a contribution towards a deeper investigation about the cyclic lateral response of RC existing bridge piers with hollow circular cross section. In particular, two reducedscale hollow circular RC piers different for aspect ratio have been tested under cyclic loading and constant axial load. The specimens were characterized by low percentage of longitudinal and transverse reinforcement (distributed on a single layer), with poor concrete, inadequate details and lack of suitable confinement reinforcement. Such specimens represent a structural typology that is widespread worldwide, even if a very small number of related experimental tests has been found from literature. Two distinct failure modes were experimentally observed, depending on the specimen slenderness, namely, a flexure mode for the tallest piers and a flexure-shear for the shortest one.

Global response and the evolution of damage has been analysed and described in details for both the specimens. It was noted that lateral strength increases as the aspect ratio decreases, as expected. On the other hand, the lower the pier aspect ratio, the lower its ultimate deformation capacity. The squat specimen, which exhibited a flexure-shear failure mode, exhibited the lower value of ultimate drift. Local response in terms of deformability contributions due to flexure, shear and fixed-endrotation mechanisms has been also investigated. For both tests, the flexural deformability contribution resulted as predominant with respect to the shear deformability contribution, nevertheless the latter cannot be considered negligible, especially for the squat specimen.