不同浇筑方式下UHPC空心板受力性能研究

为了研究不同浇筑方式下的UHPC空心板结构的受力性能,通过两点对称加载法分别对1块UHPC整浇空心板和2块抗剪腹筋数量不同且分2次浇筑的UHPC叠合空心板进行弯曲加载试验,对试件的承载力、挠度、裂缝形态以及混凝土应变进行分析。研究结果表明:有腹筋叠合空心板和整浇空心板在对称荷载作用下纯弯段满足平截面假定;整体浇筑可以提高试件的承载力且显著增强试件的延性;增加抗剪腹筋的数量能够显著降低叠合板的滑移,提高叠合板的整体抗弯刚度和承载力,仅靠人工粗糙面难以满足叠合面的抗剪要求。最后,参考相关规范对各试件受弯承载力进行了计算对比,计算值与试验值吻合较好。     

船用EH36高强钢无缝药芯焊丝焊接接头组织和冲击韧性研究

本文以SRSF501无缝药芯焊丝在船用EH36高强钢中的焊接应用为目的,研究了国产无缝药芯焊丝SRSF501在船用EH36高强钢焊接中的组织和冲击韧性。通过试验表明：SRSF501焊接EH36钢接头各区域的冲击性能均满足船级社要求；多层多道焊时,焊缝组织由粗大的柱状组织和细小的等轴晶组织组成,底层焊缝和末道焊缝柱状晶区域较大；盖面层两侧接头热影响区存在粗晶区,其它位置接头的热影响区不存在粗晶区；焊接接头中熔合线外2mm处,晶粒最细,冲击韧性最好。     

Fracture mechanics analysis for mooring chain links subjected to out-of-plane bending (OPB)

A fracture mechanics (FM) based investigation on the mechanism of out-of-plane bending (OPB) between mooring chain links and its effects on fatigue lives of mooring chain links are conducted. Four types of OPB problems that mooring chain links laying on the chain wheel, chain links passing over the bending shoe, chain links constraint provided by the chain hawse, and chain links constraint provided by the chain stopper are considered. Tension ranges of mooring lines are calculated based on the combined loading process induced by the motions of wave frequency (WF) and low frequency (LF). Initial cracks are assumed to propagate from surfaces of chain links and stress intensity factors are calculated in terms of stress ranges determined by a finite element (FE) analysis. The results show that fatigue lives of mooring chain links are decreased significantly due to OPB effects. In addition, the increase of the number of pockets of chain wheel mitigates OPB effects on fatigue lives of mooring chain links laying on the chain wheel, and the increase of the track diameter would reduce OPB effects on fatigue lives of mooring chain links passing over the bending shoe as well. However, for chain links constraint provided by the chain hawse, the diameter of mooring chain hawse has no significant effect on fatigue lives of the mooring chain links subject to OPB if without the abrupt change of the contact conditions between chain links and chain hawse. For mooring links constraint provided by chain stoppers considering the effect of proof loading test, fatigue lives of mooring chain links would drop significantly with the increase of interlink angles and friction coefficient.     

基于高频感应加热的船用钢板材弯曲成形

在船舶建造过程中,高频感应加热是实现船体板材高效高精度弯曲成形的重要方法。本文首先采用25KW新型高频感应加热设备,进行不同感应加热过程及工艺的实验,得到典型弯曲形式的船体外板（马鞍型和帆型）。同时,采用三坐标定位仪进行面外弯曲变形的测量和曲面重构,得到实验板材面外弯曲变形的分布和数值。通过热-弹-塑性有限元分析与弹性有限元分析两种方法,计算预测板材在高频感应加热作用下的面外弯曲变形;两种数值方法预测的板材面外弯曲变形趋势和数值与测量结果比较吻合,且在弹性有限元分析中,计算机资源消耗少,计算结果精度高。     

A model for the biaxial dynamic bending of unbonded flexible pipes

An analytical model is given to investigate the behavior of unbonded flexible pipes under biaxial dynamic bending. The stick-slip conditions of each wire are studied in the framework of incremental analysis by an operator splitting of the time step into a stick-state prediction and a slip-state correction step. The tension gradient is calculated using the classical return-mapping algorithm and the obtained tension gradients are integrated numerically to find the axial tension by imposing appropriate boundary conditions. From the axial tension the bending moments with respect to the principal bending axes of the pipe are obtained. Poisson's effect, bending induced tension in the wire, shear deformations of the supporting plastic layer and the changes of the effective torsion and curvature increments of the wire after slip occurs are taken into account in the model. The results of bending moment–curvature relationship from this model are compared with the test data from simple bending and good correlations are found. The comparison of the biaxial bending moment results between this model and the available model also shows good agreement.     

“穷举法”在油船货油舱分舱优化设计中的应用

为实现油船货油舱分舱优化,以一艘大型油船为例,根据MARPOL公约和共同结构规范(HCSR)的要求,在主尺度、船型和货油舱总舱容确定的情况下,以最小静水弯矩为优化目标,基于"穷举法"编制优化货油舱横舱壁位置的应用程序。实际应用结果表明,该程序可运用到油船的分舱优化中,能达到快速、合理地分舱,提高设计效率的目的。     

舰船加筋板局部强度评估中的总纵应力折减系数研究

舰船加强筋尺寸的合理确定一直是结构设计中的热点问题。本文综合考虑总纵弯曲应力和局部载荷的相互作用,研究加强筋的许用应力折减系数(C_s)的影响因素与合理取值方法。通过分析加强筋的力学模型、对比不同规范中的C_s取值,以及用非线性有限元软件Abaqus计算一系列加筋板模型,拟合C_s曲线并与规范对比,并验证剖面对称性和局部载荷作用方向对C_s取值的影响方式,丰富了舰船局部强度校核方法的技术背景,为板架设计、舰船三维局部校核程序开发提供借鉴。     

小方型系数船舶的船体波浪载荷综合研究

从船级社规范对于不符合主尺度比要求的船舶船体梁波浪载荷的规定出发,采用理论预报和船模试验2种综合方式,进行了小于0.6方型系数、高航速、高海况目标船的波浪载荷研究.从规范对波浪载荷的线性理论预报值进行的非线性修正,修正后中拱和中垂波浪弯矩绝对值之和与线性理论预报极值全幅值相等出发,阐述所研究船特殊主尺度比下的模型试验结果、三维非线性水弹性理论预报结果显示出的波浪载荷非线性行为;同时综合模型试验与理论预报的共同规律,研究不同波高、航速、浪向等非常规船型船体波浪载荷的强非线性行为,从而认为规范基于的线性理论预报值进行非线性修正的统一规定太过笼统,进而建议规范对波浪载荷的非线性修正予以进一步的明确区分和规定.     

A regression and beam theory based approach for fatigue assessment of containership structures including bending and torsion contributions

Container shipping has been expanding dramatically during the last decade. Due to their special structural characteristics, such as the wide breadth and large hatch openings, horizontal bending and torsion play an important role to the fatigue safety of containerships. In this study the fatigue contributions from vertical bending, horizontal bending and torsion are investigated using full-scale measurements of strain records on two containerships. Further, these contributions are compared to results from direct calculations where a nonlinear 3D panel method is used to compute wave loads in time domain. It is concluded that both bending and torsion have significant impacts on the fatigue assessment of containerships. The stresses caused by these loads could be correctly computed by full-ship finite element analysis. However, this requires large computational effort, since for fatigue assessment purposes the FE analysis needs to be carried out for all encountered sea states and operational conditions with sufficient time steps for each condition. In this paper, a new procedure is proposed to run the structure finite element analysis under only one sea condition for only a few time steps. Then, these results are used to obtain a relationship between wave loads and structural stresses through a linear regression analysis. This relation can be further used to compute stresses for arbitrary sea states and operational conditions using the computed wave loads (bending and torsion moments) as input. Based on this proposed method for structure stress analysis, an efficient procedure is formulated and found to be in very good agreement with the full-ship finite element analysis. In addition it is several orders of magnitude more time efficient for fatigue assessment of containership structures.     

X80管线钢管的屈强比对其失效评估曲线的影响

X80及以上级别管线钢管的高屈强比是工程应用中的一个突出问题,失效评估曲线是其安全评定的重要依据。文中通过单轴拉伸和断裂韧性试验建立了高屈强比X80管线钢管的特征失效评估图及拟合方程。结果表明：随着钢管屈强比升高,失效评估曲线的截至线（最大载荷比）降低;高、低屈强比钢管的评估曲线在载荷比大于某一临界值时发生分离,且高屈强比钢管的评估曲线处于低屈强比钢管的评估曲线之下;高屈强比钢管的选择3评估曲线比选择1和选择2曲线更偏于安全。