The Compressive Behavior Of PEC Specially Shaped Columns With Thin-walled Steel Plate

Composite structure is a structure composed of two or more structural materials.Partial Encased Concrete(PEC)composite structure is formed by pouring concrete between flanges of H-section steel and on both sides of web,also known as semi-composite structure.PEC structure can be used as beam and column components of multi-storey and high-rise frame structures such as office buildings,residential buildings,etc.Its advantages are good fire resistance,easy prefabrication and lightweight,and simple construction.Special-shaped column structure is composed of cross-shaped,T-shaped,L-shaped and Z-shaped special-shaped cross-section columns instead of general frame columns as vertical supporting members.It can avoid frame columns bulging in indoor space,reduce occupancy of building space and improve the ornamental of buildings.Combining PEC structure with special-shaped column structure is the PEC special-shaped column structure discussed in this paper.At present,there are few studies on PEC special-shaped column structure.Most of the related studies are focused on single I-shaped partially encapsulated concrete composite structure.It is precisely because of the lack of research on PEC special-shaped column system at present that it is difficult to give full play to its advantages in practical engineering,which restricts its popularization and application.In this paper,theoretical analysis,finite element analysis and experimental study of PEC special-shaped column structure are carried out.Firstly,the descriptions of the ultimate bearing capacity formulas under axial compression in various codes are introduced and compared with examples.In view of the fact that the current codes do not specify specific eccentric compression formulas for PEC special-shaped columns,the formulas for unidirectional eccentric compression of cross-shaped,T-shaped and L-shaped PEC special-shaped columns are deduced through assumptions of full section plasticity and some simplification,which can be used for the initial calculation and design of PEC special-shaped columns.Secondly,the finite element analysis and experimental study of the cross-shaped PEC special-shaped short columns under axial compression are carried out,and the specimens of the same size,material and structure are compared and analyzed.Five specimens were designed,and the control variables were the thickness of steel plate and the spacing of tie bars.By comparing the results of the finite element calculation with the experimental results,the correctness of the finite element calculation is verified,and more influencing factors can be further studied by using the finite element method.Finally,the influence factors of axial compression,unidirectional eccentric compression and bidirectional eccentric compression of cross-shaped PEC special-shaped columns are studied by finite element simulation.The effects of plate thickness,spacing between tendons,steel strength,concrete strength,eccentricity and loading angle on ultimate bearing capacity and ductility of members are considered respectively.