山东烟台大季家地区海水入侵界面划分的意义

在沿海地区划分海水入侵界线具有重大意义,在海水入侵范围内,地下水由于含盐量高,虽然工业生产、人畜生活不能利（饮）用,但深部海水可为海产品养殖业带来较高的利用价值。利用高密度电法和可控源音频大地电磁2种方法准确划分了浅、深部海水入侵界线,并根据电性特征分析探讨了海水入侵区域的由浅至深的侵入特点,推测了不同深度上岩石破碎及富水规律,为探讨沿海养殖业利用温度相对稳定或较高的深部入侵海水进行了积极、有益的探讨。     

Debating clean energy: Frames,counter frames,and audiences

In the United States, both scholars and practitioners have repeatedly emphasized the importance of “issue framing” for garnering public support for climate change policy. However, the debate frequently overlooks the importance of counter frames. For every framing attempt by advocates of climate policy, there will be a counter frame by the opponents of climate policy. How do counter frames influence the effectiveness of issue framing as a communication strategy? To answer this question, we report results from a survey experiment on a nationally representative sample of 1000 Americans on clean energy policy, a key policy issue in the public debate on climate change in the United States. Overall, we find that different combinations of positive and negative frames have remarkably little effect on support for clean energy policy. A follow-up on-line survey experiment with a convenience sample of 2000 Americans suggests that the counter frames are responsible for undermining the effects of the original frames.     

Rocking vibrations of a rigid embedded foundation in a poroelastic half‐space

This paper presents an analysis of the rocking vibrations of a rigid cylindrical foundation embedded in poroelastic soil. The foundation is subjected to time‐harmonic rocking excitation and is perfectly bonded to the surrounding soil. The soil underlying the foundation base is represented by a homogeneous poroelastic half‐space, whereas the soil along the side of the foundation is modeled as an independent poroelastic stratum composed of a series of infinitesimally thin layers. The behavior of the soil is governed by Biot's poroelastodynamic theory. The contact surface between the foundation base and the poroelastic soil is assumed to be smooth and either fully permeable or impermeable. The dynamic interaction problem is solved by employing a simplified analytical method. Some numerical results for the nondimensional rocking dynamic impedance and nondimensional angular displacement amplitude of the foundation are presented to show the effect of nondimensional frequency of excitation, poroelastic material parameters, hydraulic boundary condition, depth ratio and mass ratio of the foundation. Copyright © 2009 John Wiley & Sons, Ltd.     

Displacement‐controlled method and its applications to material non‐linearity

For the analysis of non‐linear problems, the displacement‐controlled method (DCM) has a more extensive application scope and more powerful abilities than the load‐controlled method (LCM). However, difficulties of the DCM's procedure not amenable to most finite element implementations of the conventional LCM have restricted its applications in geomechanics. By means of Sherman–Morrison's theorem, the solution of DCM is improved. The improved procedure is characterized by high efficiency, good numerical stability and a programme structure similar to LCM. Two aspects of applications of DCM are illustrated. The first application is to compute the response of a structure under a given load level like the conventional finite element analysis. The second application is to trace the equilibrium path of a structure under a given load distribution type. A simple but effective algorithm is presented for automatically adjusting the step length in tracing the equilibrium path. Examples illustrate that the proposed procedures are suited for modelling complicated non‐linear problems in geomechanics. Copyright © 2005 John Wiley & Sons, Ltd.     

皖南山区钢管砼拱桥施工技术

铜管砼拱桥在皖南山区受到应用限制的主要因素是钢管加工困难,构件运输的自然环境条件差,大型预制构件不易到达桥位处,加之某些区域的环境因素影响,使钢管砼拱桥施工,养护和维修成为主要问题.文章主要叙述了钢管砼拱桥的几种施工方法,对各种施工方法的适用条件及技术要点进行了分析,供同行参考.     

Shaking table tests of a resilient bridge system with precast reinforced concrete columns equipped with springs

This paper presents the shake table test results of a novel system for the design of precast reinforced concrete bridges. The specimen comprises a slab and four precast columns. The connections are dry and the columns are connected to the slab by an ungrouted tendon. One of the tendon ends is anchored above the slab, in series with a stack of washer springs, while the other end is anchored at the bottom of the column. The addition of such a flexible restraining system increases the stability of the system, while keeping it relatively flexible allowing it to experience negative post-uplift stiffness. It is a form of seismic isolation. Anchoring the tendon within the column, caps the design moment of the foundation, and reduces its size. One hundred and eighty-one shake table tests were performed. The first 180 caused negligible damage to the specimen, mainly abrasion at the perimeter of the column top ends. Hence, the system proved resilient. The 181^st excitation caused collapse, because the tendons unexpectedly failed at a load less than 50% of their capacity (provided by the manufacturer), due to the failure of their end socket. This highlights the importance of properly designing the tendons. The tests were used to statistically validate a rigid body model. The model performed reasonably well never underestimating the median displacement response of the center of mass of the slab by more than 30%. However, the model cannot predict the torsion rotation of the slab that was observed in the tests and is due to imperfections.     

竖波钢板组合剪力墙震损修复研究

钢板组合剪力墙在强震作用下受损严重,震损修复问题较为突出。现设计一片以方钢管作为边缘约束构件的竖波钢板组合剪力墙,在最大弹塑性层间位移角时的震损情况进行分析:竖波钢板组合剪力墙边缘约束方钢管刚度较大,与墙体不匹配,最终发生方钢管从地梁拔动的脆性破坏模式。对竖波钢板组合剪力墙进行震损修复,得到墙趾可更换竖波钢板组合剪力墙,然后进行拟静力试验。试验结果表明:（1）在震损后的竖波钢板组合剪力墙的墙趾处安装阻尼器,其抗震性能基本得到恢复。（2）修复后的竖波钢板组合剪力墙承载力较修复前降低了23%,但延性和耗能能力显著提升。（3）改变了竖波钢板组合剪力墙的破坏模式,由脆性破坏转化为延性破坏。借助有限元软件详细讨论了内嵌竖向波形钢板厚度和波角、轴压比、阻尼器腹板数量对修复后竖波钢板组合剪力墙抗剪承载力的影响,结果表明:改变内嵌竖向波形钢板厚度对试件抗剪承载力影响较大,而改变内嵌竖向波形钢板波角、轴压比和阻尼器腹板数量对试件抗剪承载力影响较小。结合有限元算例,提出修复后竖波钢板组合剪力墙抗剪承载力的计算公式,可为工程实际提供参考。     

基于耐震时程法的钢筋混凝土框架弹塑性地震响应及损伤发展

耐震时程法（ETA）仅需少量的非线性时程分析,便可以掌握结构倒塌破坏的全过程。但是,此方法目前较少应用于结构倒塌失效分析。本文探讨了耐震时程曲线的特性及拟合思路,以钢筋混凝土框架为研究对象,应用ETA方法分析了钢筋混凝土框架的地震响应及损伤发展。研究结果:（1）混凝土框架结构的地震响应分析结果表明:采用ETA方法分析时结构顶点位移和层间位移角与采用IDA方法分析时接近,而最大基底剪力会略大;但是,两种方法的结果相关系数均接近于1。（2）强震下的结构倒塌分析结果表明:ETA方法能较为准确的预测结构的塑性铰分布、塑性铰出现概率及塑性铰发展顺序。当采用多条耐震时程加速度曲线作为输入时,评估结果准确性更高。由于ETA方法仅需进行少量几条耐震时程分析且计算高效,因此ETA方法可以成为预测结构失效模式的高效方法。     

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。     

内约束方钢管混凝土柱抗震性能研究

由于方钢管对混凝土约束作用较弱,地震作用下方钢管混凝土柱底部钢管易出现屈曲,因此本文提出一种新型内约束方钢管混凝土柱。基于ABAQUS有限元软件,本文采用合理的材料本构模型建立内约束方钢管混凝土柱三维实体精细有限元模型,该模型能准确反应钢管、混凝土以及拉筋之间的相互作用,又能反应拟静力作用下混凝土的塑性损伤和钢材的循环硬化规律。有限元结果与试验结果吻合良好。首先,在此基础上笔选出最佳内约束形式,对拉箍筋方钢管混凝土柱的抗震性能明显优于圆环箍筋;其次,提出在不同轴压比下内约束方钢管混凝土柱的焊接拉筋最佳布置长度和合理体积配箍率;再次,探讨不同参数对内约束方钢管混凝土柱滞回性能的影响,结果表明:提高截面含钢率和长细比能有效改善组合柱的极限承载力,而轴压比在一定范围内有利于能提高柱的承载力;最后,讨论了约束措施对内约束方钢管混凝土柱耗能性能的影响。