Behaviour of partially encased composite slender columns

Abstract

Partially Encased Composite (PEC) Columns consist of thin-walled built-up H-shaped steel sections with links welded near the !lange tips and concrete cast betwcen the !langes.This study presents the bchaviour of slender partially cncased composite (PEC) columns tinder eccentric axial load causing symmetrical single curvature bending. The load to dellection responsc of slender pm1ially encased composite column is formulated using the Newmark's iterative procedure. The performance of the proposed numerical method is demonstrated by simulating the three slender PEC column tests from the literature. The ultimate capacity of the test columns arc compared to that obtained numerically. The proposed numerical method is observed to predict the experimental results with good accuracy. A parametric study is conducted using this method to identify the potential variables that can significantly affect the behaviour of slenderpartially encased composite column. Both the major and minor axis bending is considered to observe the significancc of the sclected parametcrs. The geometric properties that can greatly affect the behaviour ofPEC columns include the column cross-sectional dimensions. length of the column. longitudinal spacing of the transverse links. thickness of the steel !lange plates and initial load ecccntricity. The efTects of these parameters on the axial capacity, mid-height de!lection and interaction diagram of the slender PEC column are studied. Among material propel1ies. variation of concrete strength is considered. The axial capacity of a panially encased compositc columns arc found to decrease significantly as the overall slenderness ratio increases. panicularly lor columns with slender plates. The efTect of the ratio of initial load eccentricity to the overall depth of the column cross-section is observed to increase the lateral displacement of slender columns significantly and is found more pronounced for columns with higher Lid ratio. Besides, a reduction in load carrying capacity has been lound with increasing the !lange plate slenderness ratio. On the other hand. link spacing-to-depth ratio has negligible efrect on the axial capacity and lateral deflection of slender PEC column. The axial capacity drops significantly in weak axis bending since lower stiffness is achieved here. EITect of overall column slenderness ratio. flange plate slenderness ratio and concrete strength are also studied on the P-M curve of the slender PEC column.