型钢连接装配式低矮剪力墙抗震性能试验研究

采用带锚筋的锚板、腹板、端板以及加劲板作为连接件,能够通过干式连接方法将上下预制剪力墙构件连为整体。为研究该新型全装配式剪力墙的受力性能和抗震性能,设计了2个剪跨比为0.783的试件和1个相同剪跨比及配筋率的现浇整体墙体,并进行了低周往复拟静力试验,分析了该全装配式剪力墙的承载能力、刚度、延性性能和耗能能力等。研究结果表明:现浇整体墙体和全装配式剪力墙的破坏形式均为受剪破坏,全装配式剪力墙的极限位移角大于现浇整体墙体极限位移角,分别为1/77和1/133,轴压比为0.3时平均延性系数3.47,低于现浇整体墙体平均延性系数4.62;但该全装配式剪力墙具有较高的承载能力和耗能能力。型钢与剪力墙的锚筋需采用穿孔塞焊的形式连接,避免锚筋与锚板焊接的位置发生剪断的现象。     

西太暖池区生物组分对海底表层沉积物物理力学性质的影响

西太平洋暖池区是指位于热带西太平洋及印度洋东部海表温度常年在28 ℃以上的海域,是全球海表温度最高的深海区,构造环境与沉积环境复杂,沉积物中的生物组分含量差异较大,生物组分会对深海沉积物物理力学性质产生显著影响,但目前对沉积物中生物组分含量和沉积物物理力学性质之间的相关性关系尚不明确。本文对西太平洋暖池区核心部位的表层沉积物样品进行现场物理力学性质测试和室内涂片鉴定,研究深海表层沉积物的物理力学性质与生物组分之间的关系。结果表明:研究区表层沉积物含水率范围为61.1%~435.1%,天然密度范围为1.04~1.76 g/cm³,贯入阻力范围为0~100 kPa,十字板剪切强度范围为0~8.6 kPa,整体具有高含水率、低密度、低强度等典型的深海沉积物物理力学性质特点。西加洛林海脊、海山等CCD以浅的区域为钙质生物组分>50%的钙质沉积区;西加洛林海槽西南部及其周边的深水沟槽地区一般为硅质生物组分>50%的硅质沉积;西加洛林海盆内部则主要为黏土沉积区。随钙质生物组分减少和硅质生物组分增多,表层沉积物类型分别为钙质沉积物、黏土沉积物和硅质沉积物,天然含水率变高,天然密度、贯入阻力和十字板剪切强度降低,表明深海表层沉积物的物理力学性质与生物组分含量密切相关:贯入阻力、十字板剪切强度、天然密度与钙质生物组分含量呈正相关,与硅质生物组分含量呈负相关;而天然含水率正好相反,与钙质生物组分含量呈负相关,与硅质生物组分含量呈正相关。本文建立了深海沉积物中生物组分与物理力学性质之间的相关关系,提出了沉积物生物组分含量与物理力学性质之间的拟合公式,可以为深海沉积物工程性质的评价提供参考。     

基于抗转模型的颗粒材料宏−细观关系研究

接触模型的宏?细观参数标定是成功使用离散元方法的关键。在离散元的接触模型中线性接触模型与抗转线性接触模型均可用于模拟砂性土的力学行为,其中抗转线性接触模型在模拟密砂的剪胀性方面具备优势。采用抗转线性接触模型对室内密实砂土三轴试验进行了离散元模拟,验证了抗转线性接触模型的可靠性;进而系统分析了颗粒间摩擦系数、刚度比和抗转动系数等细观参数与砂土峰值内摩擦角、残余内摩擦角、峰值剪胀角等宏观参数的相关关系并进行了验证;揭示了偏应力作用下,细观参数对密实砂土试样内部剪切带宽度与倾角变化的影响规律,提出了考虑剪胀角的剪切带倾角经验公式。通过研究建立了抗转线性接触模型宏?细观参数的量化关系并给出了标定参数的具体流程图,提出了快速标定宏观参数的方法并应用实例进行了验证,为采用抗转线性接触模型精准模拟密实砂土的力学特性提供依据。     

巯基棉富集-分光光度法测定地球化学样品中铂钯的野外快速分析方法研究

对于地球化学样品中铂钯的测定,传统和现代分析方法均是建立在试金或树脂及活性炭富集后用分光光度法或电感耦合等离子体质谱法测定,而在野外满足不了这些条件。本文基于样品的性质及分光光度法的适应性强等特点,开发了一种适合于野外简单条件下快速测定地质样品中铂和钯的分析方法。样品用盐酸-氯酸钾-氯化钠-氟化氢铵常温常压密闭分解,巯基棉分别富集铂和钯,灰化处理后采用三氯甲烷-石油醚(1∶3)为萃取剂,DDO为显色剂萃取比色测定铂、钯的含量。巯基棉对钯的吸附率可达98%;加入氯化亚锡-水合肼(还原剂)使铂的吸附率提高到99%。方法检出限为Pt 0.05μg/g,Pd 0.02μg/g,标准物质的测定值与推荐值基本一致,野外地质样品的测定值与实验室分析结果吻合。     

大直径深层钻孔灌注桩拔除工艺研究

结合郑州南站连接线明挖隧道（拔桩区间）拟拔桩基直径大、桩长的特点,对桩体受力特征和拔桩工艺进行了研究。通过拔桩过程中桩周土破坏模式和桩体自身的抗拉强度分析计算,选取有效的减阻方法并应用于工程实践,取得良好效果。最后总结出大直径深层钻孔灌注桩拔除工程中桩身局部扩大、桩侧摩阻力过大和断桩等问题及相应的解决方法,供今后类似工程借鉴。     

ISO2394:2015 Annex D (Reliability of Geotechnical Structures)

ISO2394:2015 contains a new informative Annex D on “Reliability of Geotechnical Structures”. The emphasis in Annex D is to identify and characterize critical elements of the geotechnical reliability-based design process, while respecting the diversity of geotechnical engineering practice. This paper highlights the main features of Annex D and gaps for future work.     

接地电阻随季节及天气过程变化规律分析

为了解框架结构建筑物基础接地电阻的季节变化特征及天气过程对其变化的影响,分析了2010年广州从化气象局框架建筑物基础接地电阻和相关气象要素的自动气象站观测资料。从季节变化特征来看,框架结构接地电阻相对较为稳定,月平均值2月最大为0.78 Ω,9月份最小为0.57 Ω,全年变化最大值约为0.21 Ω。统计季节变化曲线和暴雨过程发现,接地体电阻与1.5 m土壤温度和1.0 m土壤含水量呈现明显的负相关,接地电阻减小值与暴雨的强度无明显的相关性。文中还对较长时间无降水的干旱过程进行了分析,结果表明：干旱时框架结构接地电阻值有明显的上升趋势,尤其在夏季,干旱对接地电阻影响较大。     

A simple parameterization of bulk canopy resistance from climatic variables for estimating hourly evapotranspiration

This paper examines a model for estimating canopy resistance r_c and reference evapotranspiration ET_o on an hourly basis. The experimental data refer to grass at two sites in Spain with semiarid and windy conditions in a typical Mediterranean climate. Measured hourly ET_o values were obtained over grass during a 4 year period between 1997 and 2000 using a weighing lysimeter (Zaragoza, northeastern Spain) and an eddy covariance system (Córdoba, southern Spain). The present model is based on the Penman–Monteith (PM) approach, but incorporates a variable canopy resistance r_c as an empirical function of the square root of a climatic resistance r* that depends on climatic variables. Values for the variable r_c were also computed according to two other approaches: with the r_c variable as a straight‐line function of r* (Katerji and Perrier, 1983, Agronomie 3 (6): 513–521) and as a mechanistic function of weather variables as proposed by Todorovic (1999, Journal of Irrigation and Drainage Engineering, ASCE 125 (5): 235–245). In the proposed model, the results show that r_c/r_a (where r_a is the aerodynamic resistance) presents a dependence on the square root of r*/r_a, as the best approach with empirically derived global parameters. When estimating hourly ET_o values, we compared the performance of the PM equation using those estimated variable r_c values with the PM equation as proposed by the Food and Agriculture Organization, with a constant r_c = 70 s m^?1. The results confirmed the relative robustness of the PM method with constant r_c, but also revealed a tendency to underestimate the measured values when ET_o is high. Under the semiarid conditions of the two experimental sites, slightly better estimates of ET_o were obtained when an estimated variable r_c was used. Although the improvement was limited, the best estimates were provided by the Todorovic and the proposed methods. The proposed approach for r_c as a function of the square root of r* may be considered as an alternative for modelling r_c, since the results suggest that the global coefficients of this locally calibrated relationship might be generalized to other climatic regions. It may also be useful to incorporate the effects of variable canopy resistances into other climatic and hydrological models. Copyright © 2005 John Wiley & Sons, Ltd.     

Estimating evapotranspiration for a temperate salt marsh,Newcastle, Australia

Evapotranspiration was studied at a salt marsh site in the Hunter River estuary, NSW, Australia, during 1996–8. Estimates of actual evapotranspiration (E_a) were obtained for three sites using the eddy correlation method. These values were compared with results obtained with the Penman and Penman–Monteith equations, and with pan evaporation. The Penman–Monteith method was found to be most reliable in estimating daily and hourly evapotranspiration. Surface resistance values averaging 12 s m^?1 were derived from the eddy correlation estimates. Recent tidal flooding and rainfall were found to decrease surface resistance and increase E_a/E_p ratios. Estimates of evapotranspiration obtained using the Penman–Monteith method were shown to be sensitive to changes in surface resistance, canopy height and the method used to estimate net radiation from incoming solar radiation. These results underline the importance of accurately estimating such parameters based on site‐specific data rather than relying on empirical equations, which are derived primarily for crops and forests. Copyright © 2001 John Wiley & Sons, Ltd.     

Flux–Profile Relationships Over a Fetch Limited Beech Forest

The influence of an internal boundary layer and a roughness sublayer on flux–profile relationships for momentum and sensible heat have been investigated for a closed beech forest canopy with limited fetch conditions. The influence was quantified by derivation of local scaling functions for sensible heat flux and momentum (_h and _m) and analysed as a function of atmospheric stability and fetch. For heat, the influences of the roughness sublayer and the internal boundary layer were in agreement with previous studies. For momentum, the strong vertical gradient of the flow just above the canopy top for some wind sectors led to an increase in _m, a feature that has not previously been observed. For a fetch of 500 m over the beech forest during neutral atmospheric conditions, there is no height range at the site where profiles can be expected to be logarithmic with respect to the local surface. The different influence of the roughness sublayer on _h and _m is reflected in the aerodynamic resistance for the site. The aerodynamic resistance for sensible heat is considerably smaller than the corresponding value for momentum.