Abstract
In this research paper, simulations on five specimens of square steel tube truss concrete beams with grouted chords were conducted by finite element analysis (FEA) software ABAQUS. Comparison of failure modes, vertical load-deflection curves, and steel tube strain variation with tests was done. The rationality and validity of the FEA models were also verified. On this basis, parameter analysis was carried out, and the influence of concrete strength, steel ratio of upper and lower chords, and spacing of steel tube truss joints on the vertical load-deflection curves were obtained. From the results of tests and parameter analysis, design formulae of flexural bearing capacity for composite beams were proposed based on the assumption that steel tubes are equivalent to ordinary longitudinal steel bars. Accordingly, the results indicated that the steel tubes of the upper chords in the composite beams cannot get yield for full sections due to the structural requirements; the steel tube of the lower chords will be the first to reach fully yielding and the upper concrete crushed subsequently, showing a failure mode analogous to that of the under-reinforced concrete beam; the steel ratio of lower chords is the primary factor affecting the flexural capacity of the normal section among the parameters; the calculation from the proposed design formulae for the flexural capacity of normal section is in agreement with the tests and simulations. This research could provide reference for the design of this kind of composite beam.
Highlights
Square steel tube truss concrete beams belong to a kind of steel-concrete composite component which is fabricated by replacing longitudinal steel bars with upper and lower chords and replacing stirrups with vertical and oblique web members of square steel tube truss
Due to the fact that the square steel tube truss concrete composite beam have higher rigidity and bearing capacity, if they are used as precast members, they can minimize the section size and reduce transport and lifting costs
Recent researches on this kind of composite beams have not covered pattern failures and the main factors affecting the flexural capacity of normal sections. erefore, it is of great engineering significance to investigate the flexural performance of the square steel tube truss concrete beams and propose calculation methods of the flexural capacity of this kind of beam
Summary
Square steel tube truss concrete beams belong to a kind of steel-concrete composite component which is fabricated by replacing longitudinal steel bars with upper and lower chords and replacing stirrups with vertical and oblique web members of square steel tube truss. Due to the fact that the square steel tube truss concrete composite beam have higher rigidity and bearing capacity, if they are used as precast members, they can minimize the section size and reduce transport and lifting costs. Recent researches on this kind of composite beams have not covered pattern failures and the main factors affecting the flexural capacity of normal sections. Zheng et al [6, 7] and Zhang et al [8] studied the flexural and seismic behaviour of prestressed steel tube truss concrete composite beams with grouted chords, and the calculation formulae for bearing capacity and crack width of normal sections were put forward. The calculation approach of flexural capacity for square steel tubular truss beams with grouted chords was established based on the tested and simulated results. is provided a basis for the design of such composite beams
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