钻井船实测中的若干技术问题

介绍了港海一号钻井船实测情况 ,讨论了钻井船实测中的若干技术问题 ,给出了港海一号钻井船强度实测结果 ,对于钻井船的研究开发和钻井船规范修订具有一定意义 .

结构用侧压竹集成材强度取值研究

侧压竹是一种由竹片经胶合压制而成的竹集成材。为确定侧压竹集成材的强度指标,参照木材试验标准,对结构用侧压竹集成材试件进行了抗压强度、抗拉强度、抗弯强度、抗剪强度及弹性模量的试验实测,得到了侧压竹集成材清材的顺纹抗压强度、横纹弦向抗压强度、顺纹抗拉强度、横纹抗拉强度、抗拉弹性模量、抗弯强度、抗弯弹性模量、抗剪强度的平均值和标准值;以侧压竹集成材清材试件实测数据为基础,采用Pearson χ^(2)方法,验证了侧压竹集成材的各项强度实测值的概率分布均服从正态分布N(μ,σ^(2));基于可靠度理论,考虑材料的天然缺陷、干燥缺陷、长期荷载等影响强度取值的因素,提出了考虑多因素影响的侧压竹集成材强度设计值的确定方法,给出了侧压竹集成材构件的强度标准值和强度设计值的建议数值。结果表明:侧压竹集成材的力学性能优良,可以作为建筑结构用材。

钢筋屈服强度差异对抗震建筑的影响

由于一次试验的结果与预期不相符合,在寻找原因的过程中发现钢筋屈服强度的离散性较大,通过两个例子分析,证明了钢筋屈服点的大差异会造成抗震建筑违背抗震原则,因此建议对于抗震结构的钢筋应偏严格地限制其屈服强度实测值与钢筋强度标准值的比值。一、二级抗震建筑设计中,这个比值应采用统一值,建议不大于1.2。

现行《钢筋机械连接通用技术规程》（JGJ 107-2003）实际应用中的理解及验收时存在问题的分析

从工程生产角度出发,对现行<钢筋机械连接通用技术规程>(JGJ 107-2003)的有关内容加以分析与说明,如钢筋机械连接接头验收的指标,钢筋机械连接接头的破坏形态等,并提出相应的建议.借以促进广大工程技术人员能够正确地理解该规程的内涵及其编制者的意图,发挥其控制工程施工质量的关键作用.

建筑抗震鉴定和加固设计的软件实现方法

基于新版《建筑抗震鉴定标准》GB50023-2009、《建筑抗震加固技术规程》JGJ116-2009,在PKPM结构设计软件基础上,通过补充输入鉴定加固相关信息,如后续使用年限、构件实测强度、加固方案等,说明对现有建筑鉴定加固设计的软件实现方法。软件不仅能对现有建筑做第二级鉴定,同时也可对其进行抗震承载力验算,并将计算结果以多种方式(图形、文本、计算书)输出。

某框架结构办公楼安全性鉴定

就某框架结构办公楼安全性鉴定,介绍其调查、检测、验算、分析和评定的过程,当材料检测强度不满足原设计要求时,应根据实测强度进行验算、分析。按构件、子单元、鉴定单元三层次进行安全性评级。

强屈比及屈标比对抗震框架结构纵向受力钢筋的意义

本文介绍了钢筋力学特征值的一般规定和一、二级抗震等级框架结构纵向受力钢筋强度实测值的特殊规定,阐述了钢筋的强屈比、屈标比的实际目的和意义,指出了限制钢筋强度实测值的重要意义,并提出确保选用符合质量要求的钢筋的控制措施的建议。

某砌体结构房屋危险性鉴定

就某砌体结构老旧住宅楼的危险性鉴定,介绍其调查、检测、验算、分析和评定的过程。鉴定过程中应注重其承重体系拆改、使用历史及环境的调查。根据实测强度进行验算、分析,按构件、房屋组成部分、房屋三层次进行等级评定。

抗震框架结构纵向受力钢筋的检验与使用

介绍了对钢筋力学性能、工艺性能的一般规定和对一、二级抗震等级框架结构纵向受力钢筋强度实测值的特殊规定,分析了限制钢筋强度实测值的重要意义并提出确保选用钢筋质量符合要求的几项控制措施。

Damage model of fresh concrete in sulphate environment

A model of damage to fresh concrete in a corrosive sulphate environment was formulated to investigate how and why the strength of corroded concrete changes over time. First, a corroded concrete block was divided into three regions: an expanded and dense region; a crack-development region; and a noncorroded region. Second, based on the thickness of the surface corrosion layer and the rate of loss of compressive strength of the corroding region, a computational model of the concrete blocks' corrosion-resistance coefficient of compressive strength in a sulphate environment was generated. Third, experimental tests of the corrosion of concrete were conducted by immersing specimens in a corrosive medium for 270 d. A comparison of the experimental results with the computational formulae shows that the calculation results and test results are in good agreement. A parameter analysis reveals that the corrosion reaction plays a major role in the corrosion of fresh concrete containing ordinary Portland cement,but the diffusion of the corrosion medium plays a major role in the corrosion of concrete mixtures containing fly ash and sulphate-resistant cement. Fresh concrete with a high water-to-cement ratio shows high performance during the whole experiment process whereas fresh concrete with a low water-to-cement ratio shows poor performance during the late experiment period.

Experimental study on the compressive strength of grouted concrete block masonry based on nondestructive detection methods

Existing nondestructive detection methods were adopted to test the compressive strength of grouted concrete block masonry,i.e.the rebound method,pulling-out method and core drilling method were employed to test the strength of block,mortar and grouted concrete,respectively.The suitability of these methods for the testing of strength of grouted concrete block masonry was discussed,and the comprehensive strength of block masonry was appraised by combining existing nondestructive or micro-destructive detection methods.The nondestructive detection test on 25 grouted concrete block masonry specimens was carried out.Experimental results show that these methods mentioned above are applicable for the strength detection of grouted concrete block masonry.Moreover,the formulas of compressive strength,detection methods and proposals are given as well.

Studies on UVC Treatment of Polyamide Fibers for Improved Adhesion on TPU and TPA

We report about current work which is aimed to improve the adhesion of melt processable elastomers onto relevant reinforcement materials by means of short wave UVC （ultraviolet C） light. Results of laboratory tests regarding UVC surface activation ofpolyamide fiber materials in air using low-pressure mercury lamps with 185 nm and 254 nm emissions are shown. The effect of irradiation on fiber strength was studied to find out suitable process parameters for providing the UVC treatment efficient but as gentle as possible to avoid negative effects on reinforcement properties. Application of a laboratory process for UVC pretreatment leads to significantly increased adhesion strength between the fibers and the melt processable elastomers on the base of TPA （polyamide） respectively TPU （polyurethane）.

Scratching by pad asperities in copper electrochemical-mechanical polishing

Low dielectric constant materials/Cu interconnects integration technology provides the direction as well as the challenges in the fabrication of integrated circuits(IC) wafers during copper electrochemical-mechanical polishing(ECMP). These challenges arise primarily from the mechanical fragility of such dielectrics, in which the undesirable scratches are prone to produce. To mitigate this problem, a new model is proposed to predict the initiation of scratching based on the mechanical properties of passive layer and copper substrate. In order to deduce the ratio of the passive layer yield strength to the substrate yield strength and the layer thickness, the limit analysis solution of surface scratch under Berkovich indenter is used to analyze the nano-scratch experimental measurements. The modulus of the passive layer can be calculated by the nano-indentation test combined with the FEM simulation. It is found that the film modulus is about 30% of the substrate modulus. Various regimes of scratching are delineated by FEM modeling and the results are verified by experimental data.

Updating empirical results of wind loads on cooling towers for turbulence intensity effects

Variations of wind effects on large cooling towers observed at different turbulence intensities for our previous full-scale measurements might be caused by the inherent uncertainties in our physical experiments.Accordingly,the one-way analysis of variance(ANOVA)technique is employed for analyzing the data measured on the prototype Pengcheng cooling tower.Because ANOVA indicates that the variations of full-scale wind effects are basically the effects of turbulence intensity,the empirical results of wind loads on cooling towers obtained by generalizing physical experimental data without considering the turbulence intensity effects are updated using model test results obtained in multiple flow fields.The empirical fluctuating wind pressure distribution is updated based on the fact that the fluctuating wind pressure coefficient linearly increases with the increase in the turbulence intensity,and the empirical formulae of the spectra and the coherences is updated based on conservative assumptions.Comparisons of the empirical results and full-scale measurement data suggest that the original empirical results are either too conservative or unsafe for use.However,economic efficiency and conservativeness will be balanced if the updated empirical results are employed for the wind engineering design.

Influence of static pre-loading on the dynamic bending strength of concrete with particle element modeling

Experimental tests show that static pre-loading has a significant effect on the dynamic strength of concrete.Based on meso-scale particle element model,numerical simulations of dynamic bending tests with pre-loading are performed.Complete stress–strain relationships are then obtained.Significant increase in dynamic strength is found when the pre-loadings are imposed within the elastic limit of concrete.However,when the imposition of pre-loadings reaches the plastic or softening range,dynamic strengths may gradually decrease along with the increase in pre-loadings.The distribution of energy components and the failure modes are discussed to explain the mechanisms of the phenomena.

Mechanism of broadening of slab in continuous casting

The mechanism of broadening of slab in continuous casting was studied by numerical simulations and experimental measurements in factories. The mechanism is derived by gradual exclusion of various factors related to the broadening of slab. It is concluded that the slab exposes to no constraint at the direction of narrow face. Because of the static pressure of molten steel, the slab deforms creepily in the direction that consequently results in the broadening of slab. The broadening of slab increases with casting speed and static pressure of molten steel. The decrease of secondary cooling intensity and strength of steel at high temperature also contribute to the broadening of slab. The micro-alloying plays an important role in improving the strength of steel and in reducing the broadening of slab.

Experimental investigation of the unsteady flow in a double-blade centrifugal pump impeller

Particle Image Velocimetry (PIV) technology was used to study the unsteady internal flow in a double-blade centrifugal pump (DBCP) impeller at the design flow rate.Relative velocity distributions and turbulence intensity distributions in the DBCP impeller at six phase conditions were obtained.And mean dimensionless relative velocity,turbulence intensity,mean absolute flow angle,mean relative flow angle,mean dynamic pressure and mean angular momentum distributions at the different radii of impeller were calculated.Results show that from impeller inlet to impeller outlet,turbulence intensities gradually decrease.With the increase of radius r,mean dimensionless relative velocity first decreases and then increases,while variation tendencies of mean absolute flow angle and mean dynamic pressure are the opposite.With the increase of radius r,turbulence intensity and mean relative flow angle first decrease,then increase,and then decrease,while mean angular momentum gradually increases.

Experimental study on the effect of porosity on the uniaxial compressive strength of sea ice in Bohai Sea

For the abnormal ice condition in 2009-2010 winter, sea ice samples were collected in a tide ditch outside a port in the east coast of Liaodong Bay, and ice specimens were prepared. Experimental study was carried out with a temperature-control precision of 0.1℃, and 117 columnar-grained ice specimens were loaded along the direction parallel to ice surface under different test temperatures （-4, -7, -10, -13, -16℃） and strain rates ranging from 10^-6 to 10^-2 s^-1 within which the ductile region, duetile-brittle transition and brittle region are contained. The uniaxial compressive strengths, density and salinity of the ice specmens were measured. The results support the curved-surface relationship between the uniaxial compressive strength and porosity within a wide range of strain rate. The curved-surface relationship gives a quantitative description about the variations of the mechanical behavior transition point with ice porosity, and supplies a uniform mathematical representation of uniaxial compressive strength under different failure modes. Besides, it is deduced that abnormal ice condition in 2009-2010 winter will not result in a change of the uniaxial compressive strength of sea ice in Bohai Sea.

A research study on the spallation strength of LY12 aluminum under the pre-compression condition

To pre-compress the disk-shaped LY12 samples along the radial direction can be done with the aid of overstress assembly by heating or by mechanical clamping, which can also generate the deviatoric stress fields under different states. The spallation signals of these pre-compressed samples are measured by VISAR in the light-gas gun shock experiments. The experimental results show that even under the same impact velocity, the pullback amplitudes of the velocity at the free surface of the sam- pies vary significantly. According to the experimental data, we propose a distinct concept that the material spallation strength is closely related to the deviatoric stress fields in the material. Based on the numerical simulation, we develop a damage con- stitutive model, which reveals that the deviatoric stress reduces the tensile threshold of the void growth. The numerical inves- tigations also demonstrate that the spallation strength decreases as pre-compression increases. The experimental idea proposed in this paper can also be used to study the spallation process in other structures.