Experimental study on seismic behavior of beam-column sandwich joints with big beam-column eccentricity

Three specimens of sandwich joints with eccentricity being larger than a quarter of the column width in middle floor of frame are designed and loaded under cyclic loading. Their shear capacity, failure modes, and ductility, as well as energy dissipation are analyzed. The results show that the performance of sandwich joints with big eccentricity is good under cyclic loading. X-type reinforcements can be used to substitute for stirrups in the joint to bear shear forces. But the anchorage of longitudinal bars of beams in eccentric sandwich joints is relatively weak. Comparing to sandwich joints without eccentricity, the column longitudinal bars near the sandwich joints with big eccentricity are vulnerable to sudden change of strain.     

半干旱区玉米降解地膜覆盖栽培综合效应研究

针对吉林省西部半干旱区降水量少,特别是玉米生育期降水分布不均,玉米产量稳定性差等问题,采用降解地膜覆盖、不覆盖、普通地膜覆盖3种栽培模式,对土壤温度、水分、土壤理化性状、土壤微生物及玉米产量的影响进行研究。结果表明,降解地膜覆盖具有显著的增温保墒作用,可改善土壤物理性状,增加土壤速效养分,促进土壤微生物的活动,提高玉米的产量。降解地膜覆盖较不覆盖地膜增产14.51%;使用的降解地膜在7月下旬可分解至6级,重量减少66.35%,降低了地膜对土壤环境的污染程度。     

黑龙江省主要农业气象灾害时序特征及其对大豆产量影响的灰色关联分析

为了探讨黑龙江省农业气象灾害对大豆产量的影响,基于1974—2016年黑龙江省农业气象灾害以及大豆产量的数据,采用数理统计方法,分析黑龙江省农业气象灾害和大豆产量时序变化特征。建立基于灰色关联分析法的数理模型,引入受灾范围和灾害强度构建受灾比率,以1998年为节点,将研究期划分为1982—1998年和1999—2016年2个阶段进行研究。结果表明:黑龙江省农业气象灾害对大豆生产存在负面影响;无论是受灾范围还是受灾强度,干旱都是第1阶段（1982—1998年）黑龙江省大豆生产的关键农业气象灾害;第2阶段（1999—2016年）洪涝灾害对灾害范围影响大,风雹对受灾强度影响大。第1阶段（1982—1998年）是大豆受灾严重的时期,4类灾害对大豆的总产和单产的影响都很大。在第2阶段（1999—2016年）,4类灾害对大豆单产的影响大于对总产的影响。     

Study on the Comparison of Different Methods of Simplifying Capacity Spectrum

It is necessary to simplify the capacity spectrum into bilinear form so as to get characteristic point of hysteretic bone curve(especially the yield point and the yielded stiffness),ductility and equivalent damping of the structure.Three general methods of calculating yield point and yielded stiffness of equivalent SDOF are introduced and the yield point and the yielded stiffness of three frame structures are compared using above given methods in this paper.The hysteretic bone curves of equivalent SDOF are decided by the equivalent yield force and displacement,the maximum plastic displacements of equivalent SDOF under rare earthquake are calculated,and it is compared with the maximum plastic displacements of member structures using nonlinear dynamic analysis.Finally,the advice of simplifying capacity spectrum is advanced.     

Two-dimension Opto-electronic Test Method to Determine the Cancellous Bone Porosity

A two dimension opto electronic test method has been developed to determine the distribution characteristics of cancellous bone porosity. The fresh pig tibiae concellous bone in behind leg was sectioned. A total of 36 cancellous bone sections were divided two groups. The first group consisted of 18 transversal sections along the axial direction, and the second group consisted of 18 axial sections along the transversal direction of the tibiae. Their images were examined microscopically and processed quantitatively. The total area, solid matrix area and pore area of each specimen and its porosity were determined, too. The cancellous bone porosity is gradually decreased along the axial direction of tibiae and approaching to the compact bone, but almost constant along the transversal direction. Cancellous bone is modeled as a transversely isotropic, liquid saturated porous solid. The two dimension opto electronic test method can be used to relatively accurately determine the distribution characteristics of the cancellous bone porosity from different directions if the cancellous bone sections are enough.     

An Experimental Research on the Deformation and Strength Properties of Chongqing Sandstone

An experimental research on the 22 samples of Chongqing sandstone was carried out on the INSTRON press machine. Based on the experimental results, the failure types in the four applied loading paths were analyzed. The deformation and strength properties of Chongqing sandstone were discussed. The quadratic functional relations between the confined pressing and the maximal strain (or the maximal deviated stress) were proposed, which could be applied to the estimating the maximal deformation and strength of Chongqing sandstone under different confined pressing.     

A Design Method for Composite Ply Containing Preformed Hole

A iteration method for the orientation and the distribution of fibers in a composite ply with a pre-formed hole is proposed, which is based on the FEM analysis and the corresponding criterion of strength and continuous condition of fibers. It is shown that, there is marked increase of the load carrying capability compared with that of the ply with a drilled hole. The obtained result can further be extended to the design of composite laminate with pre-formed holes.     

Elastic-plastic Solution of Expansion of Spherical Cavities under 3D Loading

In elastic-plastic solution of expansion of spherical cavities, based on Mohr-Coulomb strength criterion, the effect of intermediate principal stress on yield and failure of soil is not analyzed. Therefore, there is disparity between results obtained by Mohr-Coulomb strength criterion and those obtained from experimental data. In this paper, the elastic-plastic solution of expansion of spherical cavities, based on unified strength theory is established and unified solutions are obtained. The corresponding solutions of different materials can be obtained. The unified solution cannot only be used to fit the properties of the materials with different tension-pressure strength, but also those with equal tension-pressure strength. The results show that by this solution, full use of the properties of the materials can be attained to reduce supports, which is of important significance for engineering     

Experimental Analysis on the Physicochemical Characterization of Kiel Bone

Xenograft bone such as Kiel bone has long been used as a grafting materials,but the results of Kiel bone application in clinic are still controversial due to it's some drawbacks. To investigate the novel procession method of xenograft bone, the physicochemical characterization of Kiel bone and it's relationship with the clinical application are studied. Kiel bone is prepared from bovine femoral cortical bone according to Salama's methods.The bone specimens are characterized with a number of physicochemical methods such as FTIR spectroscopy, X-ray diffraction spectroscopy , differential scanning calorimetry (DSC) and uniaxial tension mechanical tests. The result indicates that Kiel bone is composed of hydroxyapatite and organic component ,and the deproteination of Kiel bone is imcomplete, but processes with hydrogen peroxide, the collagen is denatured which reduce the mechanical properties of materials. The immunogenicity of Kiel bone is weakened since the main antigenic protein is removed and collagen is denatured, which not only weakens the strength of materials but influences on it's physiological property, all make the osteoinductive properties of materials unideal. To overcome these problems, it is necessary to develop the novel procession method of the xenogeneic bone.     

反算法在某边坡稳定性评价中的应用

重点探讨了反算法的基本原理、反算的具体方法步骤、反算法建立联立方程的条件,应用边坡稳定性反算分析原理,依据工程实例对边坡滑移面的抗剪强度参数进行反算,给出了抗剪强度参数的建议值。