The Research On Shaft Pull Performance Of Assembled NC Components With UHPC Wet Joints

Assembled concrete structures are widely applied due to their advantages in convenient construction and time saving.The existing wet joints used in conventional fabricated concrete structures are still ordinary concrete.However,the joint strength between ordinary concrete joints and old concrete structures is not such high,leading to a large number of diseases at the joints of cast-in-place concrete.Ultra-high performance concrete(UHPC)has been developed as a new civil engineering material in recent years with better mechanical properties compared to conventional concrete.When UHPC is used as a wet joint,it has better bond strength with the original ordinary concrete structure.Currently UHPC wet joints has been widely studied and used in engineering in abroad,but in China,the study on the uniaxial tensile test of fabricated NC-UHPC structures is relatively lacking.This paper designed 51 test components to explore the effect on uniaxial tensile performance of the assembled NC-UHPC specimens..At the same time,combined with the finite element modeling,the simulation of the test was carried out,and some factors affecting joint strength in the test were analyzed.After the uniaxial tensile test and finite element analysis,the main conclusions are as follows:(1)UHPC can be used as a wet joint.Under the same conditions,its uniaxial tensile performance is much higher than that of conventional ordinary concrete wet joints.The joint strength can be further improved handling with punching,notching,diamond,etc.compared to the rectangular joint pattern,and the crack strength of the diamond-shaped joint with failure at the joint of specimens is higher than that of the original ordinary concrete;(2)Compared with UHPC cured by normal condition,steam cured UHPC wet joints can increase the joint strength;in terms of wettability treatment in joint,the joint strength increased with the increase of wettability.The butt joint w ith interface chiseling treatment showed better performance than the butt joint with moistening treatment;(3)With the increase of joint curing time,the cracking load and load capacity of the specimen under the axial pull is obviously improved.In additi on,within a certain reinforcement ratio,when the specimen is pulled off,the width of the main crack becomes larger with the increase of the reinforcement ratio.Moreover,with consideration of influence of the shrinkage in the wet joint UHPC,the additi onal tensile stress was induced in the joint interface,resulting in weakening of the tensile properties of the joint compared to those without considering the effect of shrinkage.(4)The numerical results obtained by finite element(FE)modeling basicall y agrees well with the experimental results.In FE modeling,traction-separation model previously proposed was used for simulation of interfacial properties.The reliability and validity were examined by this model for NC-UHPC interface.(5)The cracking location occurred at original ordinary concrete in drilled joint and grooved joint when the drilling depth was 3 cm and the perforation area ratio(Par)exceeded 23.4% as well as when the groove depth was 3 cm and the groove area ratio(Gar)exceeded 23.1%,repectively.