构造岩研究的新进展

构造岩的研究已取得很大进展。有关构造岩的分类，无论是描述性的还是按成因的分类，都各具特点，但还是以二者兼顾为好。对构造岩，尤其是糜棱岩的识别，要注意在野外区分应变梯度带和在岩相学上利用显微构造判据。构造岩的变形机制包括碎裂作用和粘性流动，而以二者之间的转换尤为重要。变形机制的交替和转换使构造岩的显微构造具一定的演化规律。由构造岩的应变局部化和力学失稳可引起成分变异、体积亏损，而流体的流动在其中也起着重要的作用。     

The role of thermal viscous remanent magnetisation (TVRM) in magnetic changes associated with volcanic eruptions: Insights from the 2000 eruption of Mt Usu,Japan

Volcanic eruptions can produce large magnetic field changes by thermomagnetic effects, especially when magma cools from high temperatures and acquires a permanent magnetisation from the Earth's magnetic field. After the 2000 eruption of Mt Usu, Japan, significant magnetic field changes were observed not only in the vicinity of the magmatic intrusion but also in an area some distance away that was unlikely to be at a temperature near the Curie Point.     

节理对爆炸波传播影响的数值研究

采用加入无反射边界条件的DDA程序,研究了节理面对应力波传播的影响。结果表明,节理面能阻碍波的传播,有利于波的衰减,节理面越多,波的反射越强,而波的透射越弱。模拟了一个现场爆炸试验,研究爆炸产生的应力波在节理岩体中传播、衰减的规律,模拟结果与现场试验结果比较吻合。研究表明,DDA方法可以模拟节理面对应力波传播的阻碍作用,用它来模拟爆炸波在节理岩体中的传播是适用的。     

边界条件对土石坝地震反应的影响研究

土石坝地震反应分析中,需要对有限网格的边界条件进行处理,以反应实际地基在空间上的无限性。分别采用黏性边界和刚性边界,对土石坝进行了动力分析。结果表明：随着坝高增加,黏性边界对坝顶加速度反应影响逐渐增大;对于均质坝,考虑黏性边界计算的坝顶加速度反应约比刚性边界低10 %～30 %;对于实际双江口直心墙土石坝,考虑黏性边界计算的坝顶加速度反应约比刚性边界低30 %～40 %左右。     

Fail-safe optimization of viscous dampers for seismic retrofitting

This paper presents a new optimization approach for designing minimum-cost fail-safe distributions of fluid viscous dampers for seismic retrofitting. Failure is modeled as either complete damage of the dampers or partial degradation of the dampers' properties. In general, this leads to optimization problems with large number of constraints. This may result in high computational costs if all the constraints are simultaneously considered during the optimization analysis. Thus, to reduce the computational effort, the use of a working-set optimization algorithm is proposed in this paper. The main idea is to solve a sequence of relaxed optimization subproblems with a small subset of all constraints. The algorithm terminates once a solution of a subproblem is found that satisfies all the constraints of the problem. The retrofitting cost is minimized with constraints on the interstory drifts at the peripheries of frame structures. The structures considered are subjected to a realistic ensemble of ground motions, and their response is evaluated with time-history analyses. The transient optimization problem is efficiently solved with a gradient-based sequential linear programming algorithm. The gradients of the response functions are calculated with a consistent adjoint sensitivity analysis procedure. Promising results attained for 3-D irregular frames are presented and discussed. The numerical results highlight the fact that the optimized layout and size of the dampers can change significantly even for moderate levels of damage.     

黏滞阻尼器对高层钢结构地震易损性的影响

为研究黏滞阻尼器对高层钢结构地震易损性的影响,基于Open SEES有限元分析平台,建立一个25层钢框架结构以及同尺寸附着黏滞阻尼器的钢框架结构,对两个钢框架结构以地震动峰值加速度(PGA)作为地震动强度指标,以结构最大层间位移角θmax为工程需求参数,从太平洋地震工程研究中心(PEER)中选取了15条地震动记录,分别对两个结构进行增量动力分析(Incremental Dynamic Analysis,IDA),建立结构的IDA曲线簇。结合地震易损性分析,对分析结果进行对数拟合,构筑两个结构的连续易损性曲线,并进一步提出用贝塔分布函数将结果转化为地震动参数-震害指数概率密度函数的概率表达方式,可以更加直观简便地观察到黏滞阻尼器显著的减震效果。该表达方法具有直观性,研究成果可为既有结构的地震灾害风险评估等提供简明且有力的分析方法。     

Energy dissipation models for RC members and structures

The unloading parameters of hysteretic models for RC members are given in terms of their shear-span-to-depth ratio and the viscous damping used to model other energy dissipation sources. They reflect the energy dissipation in full post-yield load cycles in 534 tests of rectangular or circular members. Pre-yield hysteretic energy dissipation—ignored if the model is elastic till yielding—amounts in the tests to a mean viscous damping around 8.5% and can be considered in nonlinear response-history analysis through a new model which combines constant elastic stiffness in virgin loading with hysteretic energy dissipation both before and after yielding. Models with linear behavior till yielding and hysteretic energy dissipation only after it come closer to the results of the new model if viscous damping is 5%.     

独塔自锚式悬索桥纵向设置黏滞阻尼器参数分析

以鼓山大桥为工程背景,研究黏滞阻尼器对该桥抗震性能的影响。利用非线性动力时程分析的方法讨论了黏滞阻尼器参数C及ξ的不同组合对该桥塔底、墩底、梁端及塔顶等关键部分内力及变形的影响规律。综合考虑桥梁结构各个关键部位的反应情况,得出该桥的拟安装阻尼器的最优参数约为C=1500kN／（m·s）^0.3,ξ=0．30左右。分析结果表明：在纵桥向设置适当参数的阻尼器可有效减小纵桥向位移的同时改善关键构件受力。     

成层土中桩土耦合扭转振动特性理论研究

假设桩周土层为成层黏弹性体,土体材料阻尼为黏性阻尼,从三维轴对称角度出发,对任意激振扭矩作用下,成层土中完整桩与土扭转耦合振动时的桩顶振动特性进行了理论研究.首先建立定解问题,然后利用拉氏变换求解得到其振动角位移的形式解,并利用桩土接触界面处的连续条件来考虑桩土耦合作用,使用桩段阻抗函数的传递性进行逐层递推求解,最终得到桩顶频域和时域响应的理论解.通过参数影响分析研究发现,成层土中桩顶复刚度主要受上部土层动力特性及性质影响;随着上层土模量增大桩顶复刚度的刚度部分也相应增大,阻尼部分相应减小.成层土由于土层模量变化,桩的导纳曲线有大峰夹小峰循环的特征.当上层土模量大于下层土模量时,在土层分界面时域波形与初始脉冲反向,反之则同向,土模量突变导致的时域波形的特征反射较平缓,幅度不大.