Numerical simulations of a highway bridge structure employing passive negative stiffness device for seismic protection

A new passive seismic response control device has been developed, fabricated, and tested by the authors and shown to be capable of producing negative stiffness via a purely mechanical mechanism, thus representing a new generation of seismic protection devices. Although the concept of negative stiffness may appear to be a reversal on the desired relationship between the force and displacement in structures (the desired relationship being that the product of restoring force and displacement is nonnegative), when implemented in parallel with a structure having positive stiffness, the combined system appears to have substantially reduced stiffness while remaining stable. Thus, there is an ‘apparent weakening and softening’ of the structure that results in reduced forces and increased displacements (where the weakening and softening is of a non‐damaging nature in that it occurs in a seismic protection device rather than within the structural framing system). Any excessive displacement response can then be limited by incorporating a damping device in parallel with the negative stiffness device. The combination of negative stiffness and passive damping provides a large degree of control over the expected performance of the structure. In this paper, a numerical study is presented on the performance of a seismically isolated highway bridge model that is subjected to various strong earthquake ground motions. The Negative Stiffness Devices (NSDs) are described along with their hysteretic behavior as obtained from a series of cyclic tests wherein the tests were conducted using a modified design of the NSDs (modified for testing within the bridge model). Using the results from the cyclic tests, numerical simulations of the seismic response of the isolated bridge model were conducted for various configurations (with/without negative stiffness devices and/or viscous dampers). The results demonstrate that the addition of negative stiffness devices reduces the base shear substantially, while the deck displacement is limited to acceptable values. This assessment was conducted as part of a NEES (Network for Earthquake Engineering Simulation) project which included shaking table tests of a quarter‐scale highway bridge model. Copyright © 2014 John Wiley & Sons, Ltd.     

山东省德州市地面沉降控沉分析及建议

山东省德州市地面沉降具有发展历史久、沉降量大、分布范围广、持续发展等特征,地面沉降防治工作形势紧迫.为分析《山东省德州市地面沉降防治规划(2018—2025年)》控沉目标如期实现的可能性,以德州市地面沉降现状及现有防治手段为基础,通过区域地面沉降速率公式量化计算及中心沉降速率预测进行控沉目标可行性分析.结果表明,在最严格的水资源管理制度条件下,控沉目标可以实现.针对地面沉降防治存在的问题,如地面沉降监测手段及监测频率有待提高、防治经费缺乏保障、地面沉降成因机理研究不深入、治理欠缺等,从管理和技术两方面出发,提出了包括健全监测网络、控采地下水、加大地面沉降知识宣传等控沉建议.该研究可为德州市切实有效进行地面沉降防治工作提供参考.     

航空甚低频电磁异常在胶东牟乳地区构造填图中的应用

通过对胶东牟平－乳山地区１：２．５万航空甚低频电磁异常的分析研究，并结合航磁，航放、遥感以及区域构造地质资料，进行了构造地质填图，首次进一步证实了被前人所忽视的近东西向断裂构造的存在，并给予了准确定位。在此基础上进行了金矿成矿远景预测，取得了比较满意的效果。     

长江中游洞庭湖防洪系统水流模拟——Ⅰ．建模思路和基本算法

针对长江中游洞庭湖防洪系统规模庞大、水流复杂、资料短缺和预报时限紧迫的实际条件,提出了具有层次和模块结构特点、一维与二维水流模拟、水力学与水文学方法、理论模型与补充信息相结合的建模途径.所建模型的湖泊部分采用无结构网格二维非恒定流高性能有限体积格式,以适应湖区复杂的边界形状和保持水量平衡;河网部分采用一维非恒定流守恒型显格式,避免隐格式矩阵算法的复杂性,同时有利于与二维模型的耦合及与各种复杂连通关系的显式连接.这种一、二维混合非恒定流模型可用于长江干流、洞庭湖河网及湖泊、堤垸区的洪水演进和防洪调度的水流仿真.     

青岛城市规划区不同岩性氡浓度差异及其控制因素

青岛是典型的花岗岩地区,通过分析青岛不同岩性的氡浓度探讨其差异和控制因素。结果表明：青岛不同岩芯的氡浓度变化范围为0.05～19.51 KBq/m3,平均值为2.56 KBq/m3（n=210）,花岗岩氡浓度均值为1.54 KBq/m3,同其他岩性相比氡浓度较低。不同岩性样品氡浓度释放量平均值表现为粉质黏土＞泥岩＞砂质泥岩＞泥质砂岩＞闪长岩＞粉土/填土＞砂岩＞正长花岗岩＞粗砂＞花岗岩＞二长花岗质片麻岩。综合来看,土壤层中氡浓度最高,其次是沉积岩和岩浆岩,变质岩中氡浓度最低。不同岩性氡浓度与其铀含量和孔隙率有关,除花岗岩外,沉积岩和变质岩中铀含量越高所含氡浓度越高,沉积岩、岩浆岩以及变质岩的氡浓度和孔隙率大小呈正相关,沉积岩中氡浓度高于岩浆岩,推测与其所含的富水砂层有关;土壤的土质均匀疏松,孔隙度最高,氡在土壤中有大量的存储空间,故在所有岩性中所含的氡浓度最大。     

Wave energy conversion under constrained wave-by-wave impedance matching with amplitude and phase-match limits

This paper investigates an approach to limit the fullness of ‘tuning’ provided by wave-by-wave impedance matching control of wave energy devices in irregular waves. A single analytical formulation based on the Lagrange multiplier approach of Evans [1] is used to limit the velocity amplitude while also limiting the closeness of the phase match between velocity and exciting force. The paper studies the effect of the present technique in concurrently limiting the device velocity and the required control/actuation force. Time domain application requires wave-profile prediction, which here is based on a deterministic propagation model. Also examined in the time domain is the effect of possible violation of the displacement constraint, which for many designs implies impacts at hard stops within the power take-off mechanism. Time domain simulations are carried out for a 2-body axisymmetric converter (with physical end-stops) in sea states reported for a site off the US east coast. It is found that the approach leads to effective power conversion in the less energetic sea states, while as desired, considerable muting of the optimal response is found in the larger sea states. Under the assumptions of this work, the end-stop collisions are found to have a minor effect on the power conversion. The present approach could be used to guide the design of power take-off systems so that their displacement stroke, maximum force, and resistive and reactive power limits are well-matched to the achievable performance of a given controlled primary energy converter.     

海带的病害

本文综述了养殖海带危害严重的主要疾病其防治方法。文章按海带夏苗培育中的病害及其防治，海上栽培期间发生的病害 及其防治的顺序分别叙述了各主要病害，尤其对危害严重的病害种类进行了较为详细的记述，以期对海带疾病的研究提供参考材料。     

四川汶川大地震的构造分析

2008年5月12日在汶川映秀(北纬31.0°,东经103.4°)发生8级大地震,而后发生万余次余震,其最大震级为6.4级.此次地震属主震-余震型地震.通过构造分析认为.汶川大地震是构造地震,主要受龙门山断裂带的强烈活动控制.它是一种板内地震,其动力来源来自印度板块与欧亚板块的碰撞.而成都平原处于稳定地块中,尽管离震中较近,然受地震的影响有限,是比较安全的.     

新疆西部苏盖特构造带构造特征及勘探前景

苏盖特构造带位于新疆昆仑山弧形推覆体前缘.本文通过研究苏盖特构造带的构造特征,确定了地震反射层的地质属性,认为苏盖特构造带由表层推覆体及下部下第三系-二叠系之间的地层经过3次重复形成的叠瓦状推覆体构成.苏盖特构造带活动始于上新世阿图什组沉积期,定型于更新世.通过研究西昆仑逆冲推覆体及已钻探井的地表油源、储层特征及储盖组合,认为苏盖特构造带具有两套好的油源即石炭-二叠系及侏罗系油源,两套好的储集层即白垩系和下第三系储层,相应地,发育两套储盖组合,具有良好的圈闭及运聚条件,是有利的勘探目标区.     

龙门山北段九龙山构造几何学运动学分析

九龙山构造是川西北地区的重点勘探构造。据地震剖面分析,解析了九龙山的构造几何学特征。研究表明,九龙山背斜受到米仓山构造和龙门山构造的双重影响,主要经历了三期次构造叠加,其叠加组合形成了现今九龙山的复杂构造。通过合理的构造建模,对九龙山构造运动过程、多期构造叠加及油气运移与分布规律等有了新的认识。