This paper presents study of optimization of Fink Truss by Fully Stressed Design (FSD) method using STAAD.Pro software version STAAD.Pro V8i (SELECT series 5). Three spans of the trusses have been considered and each ...This paper presents study of optimization of Fink Truss by Fully Stressed Design (FSD) method using STAAD.Pro software version STAAD.Pro V8i (SELECT series 5). Three spans of the trusses have been considered and each truss has been subjected to 27 types of load cases by changing nodal load locations. Central node load has been kept constant in each truss as 100 kN. Three sets of load condition is taken, viz, 100 kN, 120 kN and 150 kN. Total 81 trusses have been analyzed in this study to achieve a target stress of 100 MPa. Steel take-off for each case and maximum displacement for each case have been calculated and compared in this study and it shows that weight does not always increase with increase in the span or height. Results of the study could be helpful in designing a truss that does not waste material.展开更多
For planning optimum multiple stresses accelerated life test plans, a commonly followed guiding principle is that all parameters of the life-stress relationship should be estimated, and the number of the stress level ...For planning optimum multiple stresses accelerated life test plans, a commonly followed guiding principle is that all parameters of the life-stress relationship should be estimated, and the number of the stress level combinations must be no less than the number of parameters of the life-stress relationship. However, the general objective of an accelerated life test(ALT) is to assess thep-th quantile of the product life distribution under normal stress. For this objective,estimating all model parameters is not necessary, and this will increase the cost of test. Based on the theoretical conclusion that the stress level combinations of the optimum multiple stresses ALT plan locate on a straight line through the origin of coordinate, it is proposed that a design idea of planning the optimum multiple stresses ALT plan through transforming the problem of designing an optimum multiple stresses ALT plan to designing an optimum single stress ALT plan. Moreover, a method of planning the optimum multiple stresses ALT plan which can avoid estimating all model parameters is established. An example shows that, the proposed plan which only has two stress level combinations could achieve an accuracy no less than the traditional plan, and save the test time and cost on one stress level combination at least; when the actual product life is less than the design value, even the deviation of the model initial parameters value is up to 20%, the variance of the estimation of thep-th quantile of the proposed plan is still smaller than the traditional plans approximately 25%. A design method is provided for planning the optimum multiple stresses ALT which uses the statistical optimum degenerate test plan as the optimum multiple stresses accelerated life test plan.展开更多
Fatigue design method is usually used for estimating whether a platform structure meets the requirements of fatigue resistance. It is described in API RP-2A and ZC rules for fixed offshore platforms, in which the allo...Fatigue design method is usually used for estimating whether a platform structure meets the requirements of fatigue resistance. It is described in API RP-2A and ZC rules for fixed offshore platforms, in which the allowable stresses for fatigue design are defined. In this paper discussed are the allowable stresses related factors, such as wave climate, structural response, fatigue behaviour of structural members.展开更多
China’s Ministry of Commerce(MOFCOM)and the Ministry of Industry and Information Technology(MIIT)have designed a stress-test for China’s labor-intensive industries,
Accelerated life testing(ALT)has been widely used to obtain information about the product's life characteristics at normal conditions in a relatively short period of time.Two key issues with ALT are test design an...Accelerated life testing(ALT)has been widely used to obtain information about the product's life characteristics at normal conditions in a relatively short period of time.Two key issues with ALT are test design and data analysis.The test design of constant stress ALT was studied in this paper.The test design usually combines engineering experiences with optimization models.Such approaches are hard to be implemented by practitioners.A"pure"empirical approach was presented to address this issue.With the proposed approach,some of the decision variables are determined based on the results from the literature,some of the other variables are determined based on engineering analysis and /or judgment,and the remaining variables are determined based on the empirical relations developed in this paper.A real-world example is included to illustrate the appropriateness of the proposed approach.展开更多
Objective:To study the stress distribution of the femoral hip prosthesis after the hip joint replacement.Methods:After the hip joint replacement,when the femur and prosthesis are considered as concentric cylinders wit...Objective:To study the stress distribution of the femoral hip prosthesis after the hip joint replacement.Methods:After the hip joint replacement,when the femur and prosthesis are considered as concentric cylinders with perfectly banded interface,a relatively perfect theoretical model of simulating the interfacial stress transfer is established.Results:The maximum interfacial shear stress occured at Z=0.At the cross-section of the femoral neck,interfacial shear stress decreased exponentially with the increases of the Z.Shear stress became very small at Z>0.1 m,which meant that the shear stress at the far end of the femoral hip prosthesis was very small.In order to avoid the stress concentration and femoral hip prosthesis sinking,interfacial stress must remain constant and balanced with the pressure load at Z=0.The radius of the femoral hip prosthesis changed with interfacial shear stress.The maximum value of the radius occured at Z=0,then it decreased at m.Specially,a=18.2 mm at Z=10 mm,a=5.36 mm at Z=98 mm,these are ideal radius.Conclusion:A theoretical model of simulating the interfacial stress is established when the femur and prosthesis are considered as concentric cylinders.The distributions of the interfacial shear and radial stresses with the axial positions are obtained.A theoretical reference for the design of the prosthesis is provided.展开更多
Stress Joint (SJ) plays a key role in the Top Tensioned Riser (TTR) system for deep water engineering. A preliminary design method of tapered SJ is proposed in the paper, which could help designers obtain accurate...Stress Joint (SJ) plays a key role in the Top Tensioned Riser (TTR) system for deep water engineering. A preliminary design method of tapered SJ is proposed in the paper, which could help designers obtain accurate design data. After a further sensitive analysis is carried out, the related parameters choice and control methods are recommended in the engineering practice. By taking the extreme environment conditions into consideration, the effects of bending stress reduction and curve control are analyzed, and the 3-D FE models are established by ABQOUS for numerical evaluation to verify the correctness of design results. At last, dynamic analysis and fatigue analysis, based on actual project, are carried out with designed stress joint. The analysis results prove the feasibility and guidance of this method in the practical engineering applications.展开更多
The distribution of thermal stresses in functionally graded polycrystalline diamond compact (PDC) and in single coating of PDC are analyzed respectively by thermo-mechanical finite element analysis (FEA). It is shown ...The distribution of thermal stresses in functionally graded polycrystalline diamond compact (PDC) and in single coating of PDC are analyzed respectively by thermo-mechanical finite element analysis (FEA). It is shown that they each have a remarkable stress concentration at the edge of the interfaces. The diamond coatings usually suffer premature failure because of spallation, distortion or defects such as cracks near the interface due to these excessive residual stresses. Results showed that the axial tensile stress in FGM coating is reduced from 840 MPa to 229 MPa compared with single coating, and that the shear stress is reduced from 671 MPa to 471 MPa. Therefore, the single coating is more prone to spallation and cracking than the FGM coating. The effects of the volume compositional distribution factor (n) and the number of the graded layers (L) on the thermal stresses in FGM coating are also discussed respectively. Modelling results showed that the optimum value of the compositional distribution factor is 1.2, and that the best number of the graded layers is 6.展开更多
针对焊接锚垫板齿板锚固区配筋,提出了一种锚固区新型拉压杆模型。首先对齿板锚固区6种典型效应、主应力迹线以及力流平衡关系进行分析并建立新型拉压杆模型,其次通过美国国家公路与运输官员协会(American Association of State Highway...针对焊接锚垫板齿板锚固区配筋,提出了一种锚固区新型拉压杆模型。首先对齿板锚固区6种典型效应、主应力迹线以及力流平衡关系进行分析并建立新型拉压杆模型,其次通过美国国家公路与运输官员协会(American Association of State Highway and Transportation Officials,AASHTO)Load-and-resistance Factor Design Bridge Design Specifications、Building Code Requirements for Structural Concrete and Commentary(ACI 318-19)、《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG 3362—2018)和欧洲设计建议Practical Design of Structural Concrete进行拉压杆模型参数定量化设计,根据拉压杆几何关系推导出焊接锚垫板齿板锚固区劈裂力计算式,利用有限元分析,拟合出焊接锚垫板下齿板锚固区劈裂力合力重心计算式。最后通过算例分析,按本文建议的拉压杆方法进行焊接锚垫板齿板锚固区结构配筋设计,能较好地控制锚下典型效应问题,相比《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG 3362—2018)给出的设计方法,拉压杆模型法能较好地反映结构传力机制且具备可行性和可应用性,可为焊接锚垫板齿板锚固区配筋设计提供参考。展开更多
文摘This paper presents study of optimization of Fink Truss by Fully Stressed Design (FSD) method using STAAD.Pro software version STAAD.Pro V8i (SELECT series 5). Three spans of the trusses have been considered and each truss has been subjected to 27 types of load cases by changing nodal load locations. Central node load has been kept constant in each truss as 100 kN. Three sets of load condition is taken, viz, 100 kN, 120 kN and 150 kN. Total 81 trusses have been analyzed in this study to achieve a target stress of 100 MPa. Steel take-off for each case and maximum displacement for each case have been calculated and compared in this study and it shows that weight does not always increase with increase in the span or height. Results of the study could be helpful in designing a truss that does not waste material.
基金Supported by National Natural Science Foundation of China (Grant Nos.50935002,51075370,51105341,51275480,51305402)Zhejiang Provincial Natural Science Foundation of China (Grant No.Y1100777)+1 种基金Zhejiang Provincial Key Science and Technology Innovation Team (Grant No.2010R50005)Key Program of Science and Technology of Sichuan Provincial Education Department,China (Grant No.14ZA0005)
文摘For planning optimum multiple stresses accelerated life test plans, a commonly followed guiding principle is that all parameters of the life-stress relationship should be estimated, and the number of the stress level combinations must be no less than the number of parameters of the life-stress relationship. However, the general objective of an accelerated life test(ALT) is to assess thep-th quantile of the product life distribution under normal stress. For this objective,estimating all model parameters is not necessary, and this will increase the cost of test. Based on the theoretical conclusion that the stress level combinations of the optimum multiple stresses ALT plan locate on a straight line through the origin of coordinate, it is proposed that a design idea of planning the optimum multiple stresses ALT plan through transforming the problem of designing an optimum multiple stresses ALT plan to designing an optimum single stress ALT plan. Moreover, a method of planning the optimum multiple stresses ALT plan which can avoid estimating all model parameters is established. An example shows that, the proposed plan which only has two stress level combinations could achieve an accuracy no less than the traditional plan, and save the test time and cost on one stress level combination at least; when the actual product life is less than the design value, even the deviation of the model initial parameters value is up to 20%, the variance of the estimation of thep-th quantile of the proposed plan is still smaller than the traditional plans approximately 25%. A design method is provided for planning the optimum multiple stresses ALT which uses the statistical optimum degenerate test plan as the optimum multiple stresses accelerated life test plan.
文摘Fatigue design method is usually used for estimating whether a platform structure meets the requirements of fatigue resistance. It is described in API RP-2A and ZC rules for fixed offshore platforms, in which the allowable stresses for fatigue design are defined. In this paper discussed are the allowable stresses related factors, such as wave climate, structural response, fatigue behaviour of structural members.
文摘China’s Ministry of Commerce(MOFCOM)and the Ministry of Industry and Information Technology(MIIT)have designed a stress-test for China’s labor-intensive industries,
基金National Natural Science Foundation of China(No.71371035)
文摘Accelerated life testing(ALT)has been widely used to obtain information about the product's life characteristics at normal conditions in a relatively short period of time.Two key issues with ALT are test design and data analysis.The test design of constant stress ALT was studied in this paper.The test design usually combines engineering experiences with optimization models.Such approaches are hard to be implemented by practitioners.A"pure"empirical approach was presented to address this issue.With the proposed approach,some of the decision variables are determined based on the results from the literature,some of the other variables are determined based on engineering analysis and /or judgment,and the remaining variables are determined based on the empirical relations developed in this paper.A real-world example is included to illustrate the appropriateness of the proposed approach.
文摘Objective:To study the stress distribution of the femoral hip prosthesis after the hip joint replacement.Methods:After the hip joint replacement,when the femur and prosthesis are considered as concentric cylinders with perfectly banded interface,a relatively perfect theoretical model of simulating the interfacial stress transfer is established.Results:The maximum interfacial shear stress occured at Z=0.At the cross-section of the femoral neck,interfacial shear stress decreased exponentially with the increases of the Z.Shear stress became very small at Z>0.1 m,which meant that the shear stress at the far end of the femoral hip prosthesis was very small.In order to avoid the stress concentration and femoral hip prosthesis sinking,interfacial stress must remain constant and balanced with the pressure load at Z=0.The radius of the femoral hip prosthesis changed with interfacial shear stress.The maximum value of the radius occured at Z=0,then it decreased at m.Specially,a=18.2 mm at Z=10 mm,a=5.36 mm at Z=98 mm,these are ideal radius.Conclusion:A theoretical model of simulating the interfacial stress is established when the femur and prosthesis are considered as concentric cylinders.The distributions of the interfacial shear and radial stresses with the axial positions are obtained.A theoretical reference for the design of the prosthesis is provided.
基金supported by the National High Technology Research and Development Program of China (863 Program,Grant No. 2008AA09A105-04)
文摘Stress Joint (SJ) plays a key role in the Top Tensioned Riser (TTR) system for deep water engineering. A preliminary design method of tapered SJ is proposed in the paper, which could help designers obtain accurate design data. After a further sensitive analysis is carried out, the related parameters choice and control methods are recommended in the engineering practice. By taking the extreme environment conditions into consideration, the effects of bending stress reduction and curve control are analyzed, and the 3-D FE models are established by ABQOUS for numerical evaluation to verify the correctness of design results. At last, dynamic analysis and fatigue analysis, based on actual project, are carried out with designed stress joint. The analysis results prove the feasibility and guidance of this method in the practical engineering applications.
基金Research Program in the Ninth National Five-Year-Plan of Ministryof Land and Resources, China
文摘The distribution of thermal stresses in functionally graded polycrystalline diamond compact (PDC) and in single coating of PDC are analyzed respectively by thermo-mechanical finite element analysis (FEA). It is shown that they each have a remarkable stress concentration at the edge of the interfaces. The diamond coatings usually suffer premature failure because of spallation, distortion or defects such as cracks near the interface due to these excessive residual stresses. Results showed that the axial tensile stress in FGM coating is reduced from 840 MPa to 229 MPa compared with single coating, and that the shear stress is reduced from 671 MPa to 471 MPa. Therefore, the single coating is more prone to spallation and cracking than the FGM coating. The effects of the volume compositional distribution factor (n) and the number of the graded layers (L) on the thermal stresses in FGM coating are also discussed respectively. Modelling results showed that the optimum value of the compositional distribution factor is 1.2, and that the best number of the graded layers is 6.
文摘针对焊接锚垫板齿板锚固区配筋,提出了一种锚固区新型拉压杆模型。首先对齿板锚固区6种典型效应、主应力迹线以及力流平衡关系进行分析并建立新型拉压杆模型,其次通过美国国家公路与运输官员协会(American Association of State Highway and Transportation Officials,AASHTO)Load-and-resistance Factor Design Bridge Design Specifications、Building Code Requirements for Structural Concrete and Commentary(ACI 318-19)、《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG 3362—2018)和欧洲设计建议Practical Design of Structural Concrete进行拉压杆模型参数定量化设计,根据拉压杆几何关系推导出焊接锚垫板齿板锚固区劈裂力计算式,利用有限元分析,拟合出焊接锚垫板下齿板锚固区劈裂力合力重心计算式。最后通过算例分析,按本文建议的拉压杆方法进行焊接锚垫板齿板锚固区结构配筋设计,能较好地控制锚下典型效应问题,相比《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG 3362—2018)给出的设计方法,拉压杆模型法能较好地反映结构传力机制且具备可行性和可应用性,可为焊接锚垫板齿板锚固区配筋设计提供参考。