Search

Partially encased composite beams (PECBs) have advantages over conventional steel–concrete composite beams in load-carrying capacity, flexural stiffness and fire resistance. In order to determine whether the shearing force is sufficient to ensure the yield of the tensile reinforcement in the case of a large tensile reinforcement ratio, as well as the influence of encasing concrete strength and the addition of studs on the steel web, three PECB specimens were tested under bending. The results show that, in the case of a 5% tensile reinforcement ratio, natural bonding and friction forces ensure the yield of tensile reinforcement whether studs are added on the steel web or not. The encasing concrete strength and the addition of studs on the steel web have no obvious effect on both the elastic and plastic bending resistance of PECBs. The addition of studs on the steel web significantly slows down the stiffness deterioration of PECBs within the elastoplastic stage, while the flexural stiffness is not obviously affected by the strength of encasing concrete. The simplified plastic theory is proved to be applicable to predict the flexural capacity of PECBs with a large tensile reinforcement ratio. It is also indicated by calculation that, by increasing the tensile reinforcement ratio from 2% to 5%, the flexural capacity of PECBs has a significant increase, by about 32%. [ABSTRACT FROM AUTHOR]

Partially encased composite beams (PECBs) have advantages over conventional steel–concrete composite beams in load-carrying capacity, flexural stiffness and fire resistance. In order to determine whether the shearing force is sufficient to ensure the yield of the tensile reinforcement in the case of a large tensile reinforcement ratio, as well as the influence of encasing concrete strength and the addition of studs on the steel web, three PECB specimens were tested under bending. The results show that, in the case of a 5% tensile reinforcement ratio, natural bonding and friction forces ensure the yield of tensile reinforcement whether studs are added on the steel web or not. The encasing concrete strength and the addition of studs on the steel web have no obvious effect on both the elastic and plastic bending resistance of PECBs. The addition of studs on the steel web significantly slows down the stiffness deterioration of PECBs within the elastoplastic stage, while the flexural stiffness is not obviously affected by the strength of encasing concrete. The simplified plastic theory is proved to be applicable to predict the flexural capacity of PECBs with a large tensile reinforcement ratio. It is also indicated by calculation that, by increasing the tensile reinforcement ratio from 2% to 5%, the flexural capacity of PECBs has a significant increase, by about 32%.

This study undertakes a comprehensive experimental and numerical assessment of the flexural behavior of two innovative configurations of partially encased composite (PEC) beams, incorporating H-shaped castellated and T-shaped castellated main steel components (MSCs). Seven test specimens, i.e., two traditional PEC specimens featuring H-shaped solid-web MSC, two PEC specimens with H-shaped castellated MSC (PEC-HC), one PEC specimen with a T-shaped castellated MSC (PEC-TC), and two bare steel beams, are subjected to pure static bending. The experimental outcomes manifest diverse failure mechanisms across the examined specimens. The measured flexural strength of the traditional PEC specimens and the PEC-TC specimen closely aligns with the theoretical plastic moment capacity of composite beam section. However, the observed strength of the PEC-HC specimens surpasses the theoretical plastic moment capacity by at least 20%. The compressive flange and the embedded concrete significantly enhance the flexural strength and deformability of the beams, while shear force exerts a detrimental impact on their flexural resistance. Replacing solid-web MSCs with castellated MSCs markedly increases the strength of the composite beams without altering the steel consumption, although ductility may be compromised due to excessively increased section height. Web openings within the MSC reduce the flexural strength of the PEC beams but exert a negligible impact on their stiffness. Among the variants, PEC-HC beams with circular web openings exhibit superior strength, while those with quadrilateral web openings shows the lowest strength. In addition, stress concentration at the compromised sections of the MSCs in the PEC-HC beams triggers fracture in the tensile steel flange. • Two novel castellated partially encased composite (PEC) beams are proposed. • Both experimental and numerical investigations on novel and traditional PEC beams are conducted. • Comparison of flexural behavior between novel and traditional PEC beams is conducted. • Influences of web openings, compressive steel flange and infilled concrete on beam behavior are investigated. • Capacity of novel PEC beams is assessed by plastic method of composite beam section. [ABSTRACT FROM AUTHOR]

Various countries across the globe have implemented strategic policies that encourage the development and use of high-performance materials in engineering structures. This study focused on the shear performance of partially encased composite beams with high-strength steel and UHPC (PEHC beams). Seven PEHC beams under simply supported three-point loading conditions were tested to investigate the effect of main parameters such as the shear span-depth ratio, thickness of steel web, types of steel web, and types of stirrups on shear failure modes, crack patterns, load-deflection behavior, and the response of strains. Two failure modes were observed in PEHC beams, involving diagonal compression failure and shear compression failure. As the shear span-depth ratio decreased from 2.0 to 1.5 and 1.0, the shear strength increased significantly by 13.3% and 70.8%, respectively. Test results demonstrated that the increase in the thickness of steel web and the use of steel solid web positively affect the shear strength of PEHC beams, whereas the impact of normal-strength stirrups types proved insignificant. Finally, a theoretical method was proposed to predict the shear strength of PEHC beams by considering the coworking of four mechanisms: the composite truss, the steel web, the stirrups, and the steel fibres. Then the method was validated by the good agreement between the predicted and tested shear strength results, highlighting its applicability in providing accuracy. • The partially encased composite beams with Q690 steel and UHPC are proposed. • The effects of some factors on shear performance are investigated. • A method is proposed to predict the shear strength of the beams. [ABSTRACT FROM AUTHOR]