Lateral response of ultra‐high performance concrete columns confined with high‐strength spiral stirrups

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The local bearing strength and deformation capacity of the reactive powder concrete (RPC) specimens can be dramatically improved by arranging steel spirals. In effect, the actual stress level of spirals is closely correlated with the compression behavior of concrete loaded over limited area. However, limited work has been focused on the actual stress of steel spirals in RPC. To obtain the actual confinement provided by the high-strength spirals in anchorage zones, 10 RPC specimens loaded over limited area were conducted. The loadspiral strain relationships and the deformation-spiral strain responses were discussed to investigate the lateral response of RPC. The high-strength spirals failed to reach the yield strength at the peak load, and the actual strain of the spirals ranged from 1800 to 2500 με, while the residual strength of the highstrength spirals could be fully utilized after the peak load. The actual stress of

Section: Establishment Of Actual Steel Stress Calculation Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of actual confinement provided by high‐strength steel spirals in reactive powder concrete of anchorage zones

Zheng

Zhou

et al. 2021

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“…The lateral confinement of stirrups was related to the volumetric ratio, yield strength, spacing, diameter, and configuration 80,81 . The lateral confinement of stirrups can be expressed in Equation ().

σ_{le} = k_{normale} ρ_{normalv} f_{yv},

where

σ_{le}

was the effective lateral stress of stirrups;

k_{normale}

was the effective confinement coefficient of stirrups, for rectangular stirrups,

k_{normale} = (1 - (\sum b_{i}^{2} / 6 b_{cor} h_{cor})) (1 - (s^{'} / 2 b_{cor})) (1 - (s^{'} / 2 h_{cor})) / (1 - ρ_{normals})

;

b_{i}

was longitudinal reinforcement spacing confined by stirrups in both directions along the perimeter of the rectangular column section;

b_{cor}

and

h_{cor}

were width and height of core concrete;

s^{'}

was the clear spacing of stirrups;

ρ_{normals}

was the ratio of longitudinal reinforcement.…”

Section: Parametric Analysismentioning

confidence: 99%

Estimation of ductility of concrete columns under horizontal seismic load

Chang,

Hao,

Zheng

2023

The ductility of concrete columns, which determined the deformability of concrete columns, was an important parameter in evaluating the safety of framework structures under horizontal seismic loads. In this paper, 231‐group test data for evaluating the ductility of concrete columns under seismic loads were collected to establish a reliable database. The effects of investigated parameters including the compressive strength of concrete, the lateral confinement of stirrups, the ratio and yield strength of longitudinal reinforcements, axial compression ratio, shear span ratio, and the ratio between gross area and confined concrete area on the ductility of concrete columns were analyzed. The accuracy of theoretical models for evaluating the ductility of confined concrete relied on the prediction performance for the plastic hinge length of the concrete column. The existing models for the plastic hinge length of concrete columns underestimated the test results, which should be re‐evaluated. The prediction models were developed to evaluate the ductility of concrete columns based on the parametric analysis, which had high prediction performance. In addition, the design ductility limited value of concrete columns under horizontal seismic loads was obtained.

“…Mander et al 11,12 developed the efficient confinement concept and proposed evaluation models of efficient confinement coefficients. Saatcioglu et al, 5,8,13 Chang et al, 14,15 and Li 16 found that high‐strength concrete needed more lateral confinements than normal‐strength concrete and improved the tensile strength of stirrups can significantly improve the compressive strength concrete. In particular, Wei and Wu 7 found that the peak stress and the peak strain of concrete (35.8–36.9 MPa) confined with high‐strength steel wire (1803 MPa) was increased by 2.93 and 5.68 times, respectively.…”

Section: Introductionmentioning

confidence: 99%

Compression behavior of reactive powder concrete confined with high‐strength spiral stirrups

Chang

Zheng

Hao

2023

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The lateral confinement of stirrups can improve the load‐bearing capacity and ductility of reactive powder concrete (RPC) columns. To explore the compression behavior of RPC confined with high‐strength stirrups, 45 specimens were prepared and tested under axial compression. The concrete strength was in the range of 99.86–138.24 MPa, the tensile strength of stirrups was Grade 800, Grade 970, and Grade 1270, and the volumetric ratios of stirrups were in the range of 0.9%–2.0%. The results showed that the failure modes of RPC confined with stirrups were shear expansion failure. The compressive strength and ductility of confined RPC were improved with the increase of stirrups volumetric ratios, while stirrups strength slightly affected the compressive strength and ductility. In addition, the peak stress, peak strain, and residual stress prediction models were proposed. Furthermore, the ductility index prediction models were proposed, which can be applied to determine the volumetric ratio of stirrups in stirrups confined concrete columns.