Design methods for spiral stirrups confined concrete columns by evaluating the lateral performance of transverse reinforcements

Abstract

Transverse reinforcements may not yield at the peak stress of confined concrete when the tensile strength and volumetric ratio of lateral steel do not be coordinate with concrete strength. The compressive strength and ductility of confined concrete are closely related to the lateral strain of transverse reinforcement at peak stress. However, determining the lateral strain of transverse reinforcements at peak stress is difficult due to many parameters should be considered. In this paper, a regression analysis model and an artificial neural network (ANN) model were developed to predict the lateral strain in transverse reinforcements and an ANN model was established to determine the volumetric ratio ranges of transverse reinforcements which transverse reinforcements yield at the peak stress of confined concrete. To reach the purpose, 111-group data sets assembled from previous studies were applied to test the effects of influential parameters on the lateral strain and judge whether transverse reinforcements yield at the peak stress of confined concrete. The aspect ratio of specimens, the tensile yield strength and volumetric ratio of transverse reinforcements, the compressive strength of unconfined concrete, as well as longitudinal reinforcements ratio were considered. For lateral strain prediction models, the regression analysis equation was proposed based on theoretical analysis, while the ANN model was determined by collected data; for appropriate volumetric ratio ranges determination model, the outputs of ANN model were based on the classification method to judge the lateral steel yields. The results showed that the prediction models of lateral strain had high efficiency for predicting lateral strain. Besides, the accuracy and the prediction ability of the ANN model was higher than regression analysis model. Furthermore, the appropriate volumetric ratio ranges of transverse reinforcements in different confined concrete were calculated by proposed ANN model. Finally, the recommended lateral strain prediction models and volumetric ratio of transverse reinforcements determination model can be utilized to instruct the design of confined concrete.