Study On The Steel-ultra-thin UHPC Composite Bridge Deck Based On Ultra-short Stud

In order to solve the problems of orthotropic steel deck,the author team put forward the steel UHPC light composite deck structure.On this basis,in order to meet the needs of repairing and strengthening the steel deck of long-span steel bridge and open bridge which are sensitive to self-weight,a steel-ultra-thin UHPC light composite structure using ultra-short stud is proposed.The UHPC layer of this structure is only 35 mm and is connected to the steel plate by ultra-short studs.In order to explore the basic performance of the structure and verify the f easibility of the scheme,this paper mainly completes the following work:(1)Nine static push-out test specimens were used to study the effects of stud diameter,loading method,and interface treatment on the shear performance of ultra-short studs.The finite element analysis method further studies the shear performance of ultra-short studs.The main conclusions can be drawn: the failure modes are shearing of studs;the studs’ diameter has a significant effect on the shear capacity of ultra-short studs;the interface treatment method and loading method do not affect.The load-slip curve can be divided into three phases: the elastic phase,the plastic damage phase,and the failure phase.At the same time,a fitting formula is also proposed,and the calculated value of the formula fits well with the experimentally measured value.(2)The effects of stud height,stud diameter,and interface treatment on the drawing performance were studied through 11 statically pull-out test specimens.The results show that the failure modes are that the studs are pulled out intact,the UHPC is tapered,and the interface separation is about 0.6mm during failure.Increasing the diameter and height of the studs can effectively improve the pull-out bearing capacity of the studs.Compared with the 13 mm diameter stud,the pull-out capacity of 16 mm diameter stud is increased by 22%;when the height of the stud increasing from 24 mm to 32 mm,the pulling capacity is increased by about 30%.(3)Through the tests of 14 steel-ultra-thin UHPC composite plates under the negative moment,the influence of the main design parameters on the transverse bending performance of the composite plates was studied.The results showed that: when the maximum crack width on the UHPC surface was less than 0.15 mm,the growth of the maximum crack width was approximately linear;when the maximum crack width reaches 0.2 mm or the steel bar yield,the crack width increased rapidly;The influence of reinforcement ratio and reinforcement diameter on nominal cracking stress is more significant,while the steel plate thickness influence less.(4)Based on the tests,taking a long-span suspension bridge as the engineering background,the whole bridge and local finite element model were established to verify the feasibility of the ultra-thin system based on ultra-short studs for practical engineering.The results show that when using the ultra-thin system,the stress change of the main cable and the sling was within 2.1%,and the stress level of the bridge tower,the slip safety factor of the main cable saddle,as well as the deflection of the stiffening beam all meet the requirements of the code;the ultra-thin system can significantly improve the mechanical performance of the orthotropic bridge deck,the stress drop of each typical fatigue detail of the steel bridge deck is 10.1% ～ 52.0%,and the maximum stress amplitude after the drop was less than 2 million times of fatigue strength;the stress of ultra-thin UHPC layer and the internal force of ultra-short stud in real bridge are far less than the test value,and the structure has a very sufficient safety reserve,which shows that the ultra-thin system is completely feasible in the actual project.