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2 Archives of Civil and Mechanical Engineering

2 2021

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Seismic performance of circular reinforced concrete columns subjected to compression, bending and torsion with low and moderate shear span ratio

Jiao Chiyu, Liu Yang, Wei Biao, Li Jianzhon, Hu Zhangliang, Zhu Gexi

Archives of Civil and Mechanical Engineering

2021

Vol. 21, no. 3

836--851

Under the action of an earthquake, the piers of urban curved bridges are usually subjected to compression, bending and torsion due to the geometric irregularity and with low and moderate shear-span ratio. To explore the seismic performance of piers under combined actions, this paper made a theoretical analysis on the seismic performance of four circular RC columns under combined action with low and moderate shear-span ratio through experimental research. Taking the shear-span ratio and torsion-bending ratio as the main variables, cyclic bending loading and combined cyclic bending and torsion loading were carried out on the columns, respectively. The results showed that the increase of torsional effect and shear effect will increase the failure height of the piers and weaken the energy dissipation capacity and bearing capacity. Through the extraction of characteristic points in the test data, the relationship between force, displacement and torsion-bending ratio of columns with shear-span ratio below 4 was fitted. The bending and shear restoring force models of columns with spiral stirrups and small torsion-bending ratio were established. Moreover, based on the variable angle truss theory, the concrete improvement coefficient β was introduced, and the formula of torsional bearing capacity of columns under combined actions with low and moderate shear-span ratio was deduced. Compared with the test data, when the value of β was taken as 1.1, the proposed formula could be well applied to the calculation of bearing capacity of piers with torsion-bending ratio below 0.2 under combined actions with low and moderate shear-span ratio.

Effects of horizontal ground motion incident angle on the seismic risk assessment of a high-speed railway continuous bridge

Wei Biao, Hu Zhangliang, Zuo Chengjun, Wang Weihao, Jiang Lizhong

Archives of Civil and Mechanical Engineering

2021

Vol. 21, no. 1

304--323

This study investigates the effects of horizontal ground motion incident angle on a high-speed railway continuous bridge (HSRCB). To that end, incremental dynamic analyses (IDA), seismic vulnerability analyses and seismic risk assessments were conducted on a three-span HSRCB subjected to a set of ground motions under five incidence angles θ (0°–90°). The analysis was developed only from the perspective of PGA and the results showed that the longitudinal waves (θ = 0°) only caused seismic responses in the longitudinal direction, while the waves in other directions, especially in the transverse direction, caused a coupling response both in longitudinal and transverse directions for some components, such as the sliding layer and CA mortar layer. The longitudinal seismic damage of the sliding layer and CA mortar layer under the transverse waves should receive more attention in seismic design since the exceeding probabilities and seismic risk probabilities under various incident angles θ are as high as the calculated value for θ = 0°, and with a variation within 5.95%. The maximum variation of the longitudinal response and probability for track parts was within 10.59% under various incident angles, with a significant difference in the transverse response and probabilities in response to different incident angles. In addition, the responses of bridge structure components were more sensitive to the incident angles in comparison with the track parts. Finally, results indicate that the risk probabilities are at a maximum when the ground motions fall within horizontal orientations of 67.5°–90° at the bridge longitudinal axis.