Experimental Research on the Mechanical Properties of MURSP-Type Steel-Concrete Composite Beams in Negative-Moment Region

To verify the effectiveness of uplift-restricted and slip-permitted (URSP) connectors in alleviating crack formation in the negative-moment region of steel-concrete composite beams (SCCBs) and improve the engineering adaptability of URSP connectors, this paper proposes a modified uplift-restricted and slip-permitted (MURSP) connector. Static load tests and theoretical analysis were conducted on two overhanging beams with MURSP connectors and ordinary studs to analyze the influence of different stud forms on the deflection, crack, and slip of SCCBs in the negative-moment region. Finally, a nonlinear finite element modeling method for MURSP-type steel-concrete composite beams was developed, and a finite element model was established. The results showed that the use of MURSP connectors could effectively alleviate the concrete cracking problem in the negative-moment zone of SCCBs. Compared with the common stud SCCB, the crack load of the MURSP-type SCCB was higher, the maximum crack width was lower, and the crack distribution was more uniform; however, the overall flexural stiffness of the overhanging beam with MURSP connectors was reduced by 3.08%. The interface slip of the overhanging beam with the MURSP connectors increased suddenly in the initial stage of loading, whereas the increase was more gradual in the later stage. The SCCB model established in this study was in good agreement with the results of experimental beams. The finite element analysis results showed that the ordinary stud and MURSP connector exhibited different stress and deformation states in the negative-moment region of SCCBs, and the deformation states changed from bending type to shear type.

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