Experimental Study And Design Of Composite Structure Joint On Novel Offshore Platform

The 21 st Century is the century when mankind walks towards the Ocean,the ocean economy has become a new growth point of world economic development.In the background of global energy shortage,China's comprehensive national strength and economic level have been continuously improved,which bringing a great demand for oil and gas resource.The offshore platform plays an important role in China blue ocean strategic plan,it is not only the important infrastructure of ocean oil and gas resource exploration and exploitation,but also the facility for marine scientific research.The stainless steel-concrete-steel tube offshore platform is a new type of composite offshore platform structure.The joint connection between upper desk and lower blocks is not only the key point of structure design but also the emphasis of construction installation.In this paper,in order to increase the reliability and bearing capacity of joint connection,three new-type joints have been put forward and their axial compression mechanical properties are mainly analyzed.The main research works are as follows:1.In order to solve the problem that the forms of joint cross-sections between upper desk steel tube and lower composite structure platform legs are different and unequal diameter on stainless steel-concrete-steel tube offshore platform,three new-type joints have been designed and put forward based on JZ20-2 offshore platform including transitional connector joint,stiffened bearing plate joint and flange joint.2.Three 1/4 scale model joint specimens have been designed and material tests were performed as well.Through joint axial compression experiments,the plastic development,failure mode,bearing capacity,axial stiffness and load-strain curves of the three joint are analyzed meticulously,which provides a reference for the joint reliability.3.The experimental models of the joints are simulated by finite element software ABAQUS,and the joint yield sequence and deformation reasons are analyzed in detail.The calculated results are compared with the experimental results which are in good agreement.The validity of the finite element analysis is verified,which provides the possibility for further fullscale joint simulation of the offshore platform.4.The full-scale modeling and parameter analysis of transitional connectors joint and stiffened bearing plate joint are performed by ABAQUS.The effect of the slope(S)to the transitional connector joint bearing capacity,and the plate thickness(B),the stiffeners number(N),the stiffeners height(H),the stiffeners thickness(T)and the concrete strength(C)to the stiffened bearing plate joint bearing capacity are mainly discussed.5.Geometry optimization was made according to the joint failure mode and stress mechanism.The bearing capacity of the transitional connector joint and the stiffened bearing plate joint was significantly increased after optimized.6.The results show that,all these three forms of joint can well satisfy the capacity design requirements of offshore platform.The flange joint has the highest bearing capacity and the stiffened bearing plate joint has the best ductility,in addition,the failure mode of the transitional connector joint was brittle failure.