In order to investigate the flexural behavior of ultra-high performance concrete (UHPC) lightweight composite decks under local wheel load

four demountable steelUHPC composite slabs connected by high-strength bolts were designed and four-point bending test was conducted. The influence of steel plate type and spacing of shear connector on the flexural characteristics of demountable steelUHPC composite slabs was analyzed

including failure mode

load-deflection curve

interface relative slip

crack width

and sectional strain distribution. Results showed that under positive bending moment

the failure mode of composite slabs adopting Q355 steel plate was that the high-strength bolt was cut off. While the failure mode of composite slabs using steel plate with negative Poisson’s ratio (NPR) was as follows: part of high-strength bolts was cut off

part of pre-embedded elongated nuts with cushion was pulled out

and UHPC collapsed due to instantaneous instability. Besides

under the same spacing of high-strength bolts

the relative slip of plate end of composite slabs employing NPR steel plate was relatively small

indicating that NPR steel plate can effectively delay and restrain the relative slip between steel plate and UHPC plate

thus improving the synergistic deformation capacity

flexural stiffness

and flexural bearing capacity for composite slabs. According to the sectional strain distribution analysis

due to the negative Poisson’s ratio effect

high stiffness

and high yield strength of NPR steel plate

the tensile strain between NPR steel plate and the bottom UHPC layer maintained strain compatibility during the whole loading process

and the upward displacement for sectional plastic neutral axis could be ignored with increasing load. Therefore

under the premise that NPR steel plate is employed to improve the flexural performance of steelUHPC composite slab system

the thickness of UHPC should be reasonably matched with the performance of NPR steel plate

so as to give full play to their material properties

and avoid the buckling failure prior to the material strength failure of UHPC.