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[Objective] Identifying production-living-ecological spaces (PLES) and analyzing their spatiotemporal characteristics, as well as optimizing PLES pattern provide scientific references for the rational development of the territorial space and precise implementation of major function-oriented zoning strategy. [Methods] The methods of this research include calculation method for land functions at the grid scale, mechanical equilibrium model, and comparative advantage index, which effectively solve the problems of insufficient consideration of the strong and weak relationships between land functions and insufficient scale refinement in identifying and optimizing PLES. [Results] (1) Between 2000 and 2019, there were three dominant functional spaces Xiangyang City, of which the ecology dominant space and the living dominant space had the largest and the smallest area, respectively, but the former increased and the latter decreased. There were twelve compound functional spaces, in which the ecology dominant-living weak-production inferior space and living dominant-production weak-ecology inferior space had the largest and the smallest area, respectively, and both of which showed an increasing trend. (2) The production dominant space was concentrated in the central and eastern regions, the ecology dominant space mainly occurred in the west and the south, and the living dominant space was concentrated in the urban centers of the counties. Also, the compound functional spaces’ pattern and degree of agglomeration exhibited obvious heterogeneity. (3) The PLES can be optimized into urban development zone, rural improvement zone, and agricultural production and ecological conservation zones, which showed overall consistency and local differences with major function-oriented zoning of Xiangyang City. [Conclusion] It is reasonable and scientific to identify PLES at the grid scale and formulate a differentiated optimization plan by taking into account the strong and weak relationships of land functions. This study contributes to understanding the functional compounding and spatiotemporal heterogeneity of PLES, which is an important reference for promoting the precise implementation of major function-oriented zoning and balanced development of territorial spaces in Xiangyang City.

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The objective of this study is to evaluate the axial load-bearing capacity of section-enlargement concrete columns. To reach the objection, a new strengthened method in which columns are jacketed with a large welded octagonal stirrup at the center and four spiral stirrups at the corners of column is developed. The new section-enlargement method avoids interrupting existing columns and improves the reliability of strengthened part, besides, the confining stress generated by octagonal stirrup and spiral stirrups enhances the compressive strength and deformability of strengthened columns. In addition, sixteen large-scale concrete columns strengthened by the new strengthened method were tested under axial compressive loads. The experimental results show that the axial compression ratio of existing column generates stressstrain lag in strengthened part and decreases the load-bearing capacity of specimens; the stirrups in strengthened part significantly enhance the axial load-bearing capacity of specimens. According to confinement conditions, the cross-section of specimens is divided into five parts and the confinement factor for each part is calculated to establish the prediction models for the load-bearing capacity of specimens. Furthermore, by comparing the results between the developed model and existing models, the developed model has high accuracy in evaluating the load-bearing capacity of strengthened columns. [ABSTRACT FROM AUTHOR]