Analysis Of The Influence Of Core Concrete Defects On The Mechanical Performances Of Axially Loaded Concrete Filled Steel Tubular Short Columns

Concrete-filled steel tube structure is widely applied in the stress of the system such as bridges,long-span space structures and high-rise super-tall buildings because of high bearing capacity,good plastic and toughness,great anti-seismic capability,convenient construction and excellent economic benefit.But in the process of construction,sometimes due to the influences of engineering mismanagement,construction technology and the performance of their own material,it brings defects in core concrete,such as hole,segregation and poor bond between core concrete and steel tube,thus weakens the mechanical performances of the concrete filled steel tubular in different degree.So it has important practical significance to research the mechanical performances of axially loaded concrete filled steel tubular short columns specimens with core concrete defects.First,experimental tests on the 22 specimens under axial compression were carried out to research the mechanical performances of concrete filled steel tubular columns.Then,based on the experimental results and domestic code,a revised calculating formula of bearing capacity was presented by reduction coefficient method.Finally,the finite element software was used to simulate the concrete filled steel tubular short columns.The major contents of this paper are as follows:(1)Experimental tests on the 22 specimens with different type,size and location defects under axial compression were conducted to obtain the failure modes and load displacement curves.The main experimental parametric analysis including different size hole defects,different location hole defects,different height circular separation defects,different length circular separation defects,different height spherical crown separation defects and different size spherical crown separation defects were performed to obtain the mechanical performance influence laws of the specimens with core concrete defects.(2)Based on the experimental results and the DL/T5085-1999 code,the reduction coefficient of bearing capacity was gained by multiple linear regression analysis method,then a revised calculating formula of bearing capacity was presented.(3)Compared with bearing capacity of the specimen without defect,the analysis of the weakening degree of interaction in concrete filled steel tube and the influence value of bearing capacity of the specimens with core concrete defects were performed.(4)The applicability of the finite element model was verified by comparing with experimental results,then the finite element software was used to simulate the mechanical performance influence laws of the specimens with different eccentricity hole defects and different thickness circular separation defects.