Reducing the cost of offshore platform construction is an urgent issue for marginal oilfield development.The offshore oil well structure includes a riser and a surface casing.The riser,surface casing and oil well ceme...Reducing the cost of offshore platform construction is an urgent issue for marginal oilfield development.The offshore oil well structure includes a riser and a surface casing.The riser,surface casing and oil well cement can be considered special variable cross-section piles.Replacing or partially replacing the steel pipe pile foundation with a variable cross-section pile to provide the required bearing capacity for an offshore oil platform can reduce the cost of foundation construction and improve the economic efficiency of production.In this paper,the finite element analysis method is used to investigate the variable cross-section bearing mode of composite piles composed of a riser and a surface casing in saturated clay under a vertical load.The calculation formula of the bearing capacity at the variable section is derived based on the theory of spherical cavity expansion,the influencing factors of the bearing capacity coefficient N_(c) are revealed,and the calculation method of N_(c) is proposed.By comparing the calculation results with the results of the centrifuge test,the accuracy and applicability of the calculation method are verified.The results show that the riser composite pile has a rigid core in the soil under the variable cross-section,which increases the bearing capacity at the variable cross-section.展开更多
To study the flexural behavior and calculation model,8 coral aggregate concrete(CAC)beams with different types of steel were designed.The flexural behavior of CAC beam was tested.The failure mode,bearing capacity,the ...To study the flexural behavior and calculation model,8 coral aggregate concrete(CAC)beams with different types of steel were designed.The flexural behavior of CAC beam was tested.The failure mode,bearing capacity,the maximum crack width(ws)and average crack spacing(lm)were studied.A calculation model for the bearing capacity of CAC beam was proposed.The results indicated that with the steel strength increased,the cracking moment(Mcr)and ultimate moment(Mu)of CAC beam increased,and the development of the ws gradually slowed,which effectively inhibited the formation of cracks and improved the flexural behavior of CAC beam.For CAC structures in the ocean engineering,it is recommended to use organic new coated steel to extend its effective service life.In addition,considering the influence of steel corrosion,a calculation model for the Mcr,Mu,lm and ws of CAC beam was established.展开更多
In order to study the mechanical behavior of corroded channel steel beam,experiment on five corroded channel steel beams is carried out. Test results show that the bending failures may occur under the ultimate load ca...In order to study the mechanical behavior of corroded channel steel beam,experiment on five corroded channel steel beams is carried out. Test results show that the bending failures may occur under the ultimate load carrying capacity of members,compared with the calculating results of non-corrosion channel steel beam,and the bearing capacity of corroded channel steel beam is reduced,while the deflection is increased. With the increase of shear-span ratio,the bearing capacity of corroded channel steel beam reduces and the deflection increases gradually; with the increment of heightspan ratio, the bearing capacity increases and the deflection decreases gradually; with the enhancement of width-height ratio,the bearing capacity reduces and the deflection-span ratio increases gradually. The measured results indicate that the load-deflection relationship curves of corroded channel steel beam may be divided into four sections: the exfoliated rust layer stage,the elastic stage,the yielding stage and the descending stage. The load-strain relationship curves include two sections: the elastic stage and the yielding stage. The strain measurement of web proves that the average strains agree well with the assumption of plane section. This paper could provide some scientific bases for the maintenance and reinforcement of the corroded steel structure.展开更多
基金This research was financially supported by the National Science Fund for Distinguished Young Scholars(Grant No.51825904)the National Science and Technology Major Project from the Ministry of Science and Technology(MOST)of China(Grant No.2016ZX05058004-005).
文摘Reducing the cost of offshore platform construction is an urgent issue for marginal oilfield development.The offshore oil well structure includes a riser and a surface casing.The riser,surface casing and oil well cement can be considered special variable cross-section piles.Replacing or partially replacing the steel pipe pile foundation with a variable cross-section pile to provide the required bearing capacity for an offshore oil platform can reduce the cost of foundation construction and improve the economic efficiency of production.In this paper,the finite element analysis method is used to investigate the variable cross-section bearing mode of composite piles composed of a riser and a surface casing in saturated clay under a vertical load.The calculation formula of the bearing capacity at the variable section is derived based on the theory of spherical cavity expansion,the influencing factors of the bearing capacity coefficient N_(c) are revealed,and the calculation method of N_(c) is proposed.By comparing the calculation results with the results of the centrifuge test,the accuracy and applicability of the calculation method are verified.The results show that the riser composite pile has a rigid core in the soil under the variable cross-section,which increases the bearing capacity at the variable cross-section.
基金Projects(11832013,51878350)supported by the National Natural Science Foundation of ChinaProject(B200201063)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(BK20180433)supported by the Natural Science Foundation of Jiangsu Province,China。
文摘To study the flexural behavior and calculation model,8 coral aggregate concrete(CAC)beams with different types of steel were designed.The flexural behavior of CAC beam was tested.The failure mode,bearing capacity,the maximum crack width(ws)and average crack spacing(lm)were studied.A calculation model for the bearing capacity of CAC beam was proposed.The results indicated that with the steel strength increased,the cracking moment(Mcr)and ultimate moment(Mu)of CAC beam increased,and the development of the ws gradually slowed,which effectively inhibited the formation of cracks and improved the flexural behavior of CAC beam.For CAC structures in the ocean engineering,it is recommended to use organic new coated steel to extend its effective service life.In addition,considering the influence of steel corrosion,a calculation model for the Mcr,Mu,lm and ws of CAC beam was established.
基金National Natural Science Foundation of China(No.51578001)Natural Science Foundations of Anhui Province,China(Nos.KJ2010A046,KJ2015ZD10)the Science and Technology Item Foundation of Ma'anshan,China(Nos.2012(6),2013(79))
文摘In order to study the mechanical behavior of corroded channel steel beam,experiment on five corroded channel steel beams is carried out. Test results show that the bending failures may occur under the ultimate load carrying capacity of members,compared with the calculating results of non-corrosion channel steel beam,and the bearing capacity of corroded channel steel beam is reduced,while the deflection is increased. With the increase of shear-span ratio,the bearing capacity of corroded channel steel beam reduces and the deflection increases gradually; with the increment of heightspan ratio, the bearing capacity increases and the deflection decreases gradually; with the enhancement of width-height ratio,the bearing capacity reduces and the deflection-span ratio increases gradually. The measured results indicate that the load-deflection relationship curves of corroded channel steel beam may be divided into four sections: the exfoliated rust layer stage,the elastic stage,the yielding stage and the descending stage. The load-strain relationship curves include two sections: the elastic stage and the yielding stage. The strain measurement of web proves that the average strains agree well with the assumption of plane section. This paper could provide some scientific bases for the maintenance and reinforcement of the corroded steel structure.
