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Seismic performance of concrete columns confined by high‑strength stirrups

Hou Chongchi, Zheng Wenzhong, Liu Pengfei, Wang Qinghe, Qi ShaoBo

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e69, 2023

EN

The concrete columns confined by high-strength stirrups exhibited higher bearing capacity and better deformation ability. Based on the test results of concrete columns confined by high-strength stirrups under lateral cyclic loading, it is found that stirrup yield strength could not be used directly in calculating bearing capacity, because the high-strength stirrup could not yield at the peak point. Moreover, according to the seismic performance of a total of 49 sets of confined concrete columns from this paper and other 5 research papers, an easy-to-use model of skeleton curve is proposed by using a set of empirical equations to calculate the characteristic points of skeleton curve. Furthermore, based on the proposed model of skeleton curve, hysteretic rules are developed for the unloading and reloading stages by providing calculating formula of unloading stiffness and ignoring the effect of strength degradation. Finally, the proposed model of skeleton curve and hysteretic rules are verified and evaluated by comparing the calculated curves and experimental curves.

2

Experiment and validation of local bearing capacity for reactive powder concrete confined with high-strength spirals

Li Sheng, Zheng Wenzhong, Zhou Wei, Jiang Zhisheng, Wang Ying

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e40, 2022

EN

In this study, ten reactive powder concrete (RPC) specimens confined by high-strength spirals loaded over a limited area are used to investigate their behaviour and determine their local bearing capacity. The crack, wedge, and failure characteristics of RPC are discussed based on tests and simulation. The index of pressure versus deformation is used to evaluate the loading stages. The ratio of the cracking load to the ultimate load varies from 34 to 60%. A wedge pyramid is formed ahead of the bearing plate when approaching the ultimate load; thereafter, it slips downward, splitting the concrete below. The high-strength spirals did not yield even under the ultimate load. According to the test data, all the existing models for predicting the local bearing capacity are nonconservative. In this case, the effect of the actual stress caused by high-strength spirals is considered to further modify the existing calculation models when high-strength spirals are used, and a simple empirical equation for calculating the local bearing capacity of the RPC is developed. The equation and the models modified as described are verified experimentally.

3

Compression behavior of ultra-high performance concrete (UHPC) confined with high-strength rectilinear ties

Chang Wei, Zheng Wenzhong, Hao Meijing

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e27, 2022

EN

To explore the compression behavior of ultra-high-performance concrete (UHPC) confined with rectilinear ties, sixty specimens were tested under axial compression. The investigated parameters included the compressive strength of UHPC in the range of 84.72–155.45 MPa, the volumetric ratio of rectilinear ties in the range of 0.9–2.0%, and the yield strength of rectilinear ties in the range of 873–1215 MPa. The failure modes of specimens were the formation of an inclined shear failure plane. The axial stress–axial strain curves and the axial stress–lateral strain curves of confined UHPC were analyzed. Besides, the effects of investigated parameters on the load-bearing capacity and ductility of confined UHPC were analyzed. Moreover, the prediction models for the lateral strain of rectilinear ties at peak stress, load-capacity and ductility of confined UHPC were developed.

4

Experimental investigation of full-scale concrete columns confined by high-strength transverse reinforcement subjected to lateral cyclic loadin

Hou Chongchi, Zheng Wenzhong, Li Sheng, Wu Xiaohao

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

250--267

EN

The use of high-strength longitudinal and transverse reinforcements in confined concrete columns can improve bearing capacity and deformability. Besides, experiments on confined concrete columns with side length of 400 mm can better reflect the behaviour of confined concrete columns in engineering project. Thus, the purpose of this study is to investigate the seismic behaviour of full-scale confined concrete columns with high-strength longitudinal and transverse reinforcements. Based on 15 confined concrete columns subjected to lateral cyclic loading, the effects of axial compression ratio, shear span ratio and volumetric ratio on the seismic behaviour of confined concrete columns were studied. The results showed that the ultimate drift ratios of the 15 confined concrete columns ranged from 1/43 to 1/20, i.e. 1.2–2.5 times as much as the specified limit (1/50) of rate earthquake, indicating excellent ductility. Additionally, the high-strength transverse reinforcements could not yield at peak load but could yield at the ultimate displacement. The high-strength transverse reinforcement stresses at the peak lateral load were 430–690 MPa, approximately 56–91% of the transverse reinforcement yield strength. Finally, an empirical formula was proposed to predict the ductility factor that was then evaluated by comparing the predicted values with the experimental results of 37 confined concrete columns.