钢管套筒灌浆连接轴向受拉性能模拟试验研究

为研究钢管套筒灌浆连接轴向受拉破坏过程及破坏机理，试验中设计了16组48个钢管套筒灌浆连接试件，试件采用钢板代替圆钢管，并进行静载试验。分析了灌浆料裂缝扩展过程、荷载-相对位移曲线，并对抗剪键高距比、灌浆料厚度、侧向力等因素对破坏过程及承载力的影响进行分析。结果表明：对于不设置抗剪键的套筒灌浆连接试件，斜裂缝随机产生，裂缝分布不均匀；对于设置抗剪键的套筒灌浆连接试件，裂缝首先出现在底部抗剪键位置处，与水平方向夹角约为30°，随后在中部和上部抗剪键位置处分别出现斜裂缝。由于每个抗剪键上荷载分担并不均匀，与抗剪键接触的灌浆料逐渐达到极限压应力，达到极限状态时，承载力全部由抗剪键间的机械咬合力承担，在连接承载力中，可忽略摩擦力和胶结力作用。随着抗剪键高距比h/s增大，各试件初始剪切刚度相差不大，承载力增大，但增幅逐渐减小，建议抗剪键高距比0.06g/s>0.3，同时需要满足灌浆料灌注的施工要求。     

Dynamic dip-slip fault rupture in a layered geological medium: Broken symmetry of seismic motion

As recorded recently on 22 November 2014 during the Nagano-ken Hokubu (Kamishiro Fault), Japan, earthquake, one important observation in dynamic rupture (fracture) related to a shallow dip-slip earthquake (usually assumed as mode-II shear crack propagation from depth towards a free surface) is the broken symmetry of seismic motion in the vicinity of the fracturing fault plane. Generally, the strong motion (particle motion) on the hanging wall is much larger than that on the footwall, but the physical mechanisms causing this asymmetry have not been fully clarified yet. Here, utilising the techniques of finite difference calculations and dynamic photoelasticity in conjunction with high speed cinematography, we investigate the fracture dynamics of a dip-slip fault plane situated near a free surface and try to explain the mechanics behind the asymmetry, numerically as well as experimentally. In our two-dimensional crack-like rupture models, we prepare a flat fault plane, which dips either vertically or at an angle, in a monolithic (scenario (1)) or layered (scenario (2)) linear elastic medium (representing rocks). In the basic scenario (1), when the primary fault rupture initiated at some depth approaches the free surface, four Rayleigh-type waves may be induced: two of them propagate along the free surface as Rayleigh surface waves into the opposite directions to the far field, and the other two travel back downwards along the fractured fault plane as interface waves into depth. If the fault plane is inclined, in the hanging wall, the interface and Rayleigh waves may interact with each other and a shear wave carrying concentrated energy (corner wave) can be produced to cause stronger disturbances. The corner waves, generated by primary fault rupture, may exist only when the fault plane is inclined, i.e. only when the geometry considered is asymmetric. In the scenario (2), however, we indicate that (anti-)symmetry of mode-II seismic motion can be easily broken even in geometrically symmetric models if the secondary fracture is allowed at an interface between layers. If primary vertical dip-slip fault rupture in an (anti-)symmetric model moves from depth and interacts with a horizontal interface that follows, for example, a tensile fracture criterion, basically only the interface segments where the primary rupture induces dynamic tension (in the relatively subsiding footwall) may be fractured and the segments in compression (in the rising hanging wall) may remain unbroken. In this case, in the hanging wall, the dynamic stresses in the upper layer above the interface become relatively large because the compressive parts of the primary rupture-induced wave (rupture front wave) can propagate from the lower layer across the still bonded interface into the upper layer, with less reflection back to the lower one. On the contrary, in the footwall, much of the energy carried by the rupture front wave in the lower layer is reflected at the broken interface and dynamic disturbances in the upper layer tend to become smaller. Thus, the strong motion on the hanging wall is expected to become larger than that on the footwall not only in geometrically asymmetric cases but also in symmetric ones.     

岩石高边坡稳定性并行计算及其应用

在高地震烈度区的岩石高边坡抗震安全评价需要大规模数值计算,而现有商业软件无法有效解决这类复杂的工程问题,因此,本文开发了解决岩石高边坡接触稳定性问题的对等架构并行计算程序,并应用于泰山公司抽水蓄能电站上水库左岸边坡的静力和动力稳定性评价。在数值建模过程中,将岩石边坡滑块体、地质结构面、库水作用以及近场地基作为岩石高边坡动力接触系统。在稳定性安全评价中结合了有限元法、极限平衡法和接触算法,考虑影响高边坡稳定性的多种复杂因素,通过计算特定滑动面的安全系数或安全系数时程,基于现行水电工程水工建筑物抗震设计规范,完成了岩石高边坡稳定性评价,回避了求解复杂岩体材料非线性的问题。计算结果显示,所开发的程序具有较高的并行计算效率,对解决复杂岩石高边坡稳定问题具有显著的优势。     

梁板式筏形基础冲切性能的有限元分析

利用ADINA有限元软件对单跨梁板式筏形基础进行了冲切模拟和非线性分析,得出了筏板基础的裂缝、变形及地基反力分布。结果表明：在小荷载情况下,筏板的地基反力分布比较均匀,随着荷载的增加,筏板的地基反力呈非线性分布并且主要集中在肋梁及其周围2．5倍板厚的范围内;板格及肋梁都出现了反向弯曲的现象;冲切验算时考虑了板格冲切破坏模式和节点破坏模式2种情况,并取两者的最不利值作为筏板的冲切承载力。数值模拟结果为筏板结构设计和试验研究提供了理论依据。     

改进的EMD方法及大坝强震反应信号应用分析

基于经验模态分解(EMD)的希尔伯特黄变换(HHT)方法能够较好地分析非平稳和非线性的信号。在EMD分解过程中易产生模态混淆现象,影响了信号分析结果的准确性。本文通过对EMD分解过程进行改进,在分解进程中增加滤波手段有效抑制了模态混淆现象,应用仿真信号实例进行对比分析表明抑制效果明显。最后,应用该改进方法对大坝强震反应信号进行分析,研究大坝在强震下特性变化规律。     

Numerical investigation of effectivity indices of space-time error indicators for Navier–Stokes equations

In this paper we propose two error indicators aimed at estimating the space discretization error and the time discretization error for the unsteady Navier–Stokes equations. We define a space error indicator for evaluating the quality of the mesh and a time error indicator for evaluating the time discretization error. Moreover, we verify the reliability of the estimations through numerical experiments and we propose an effective space-time adaptive strategy for the unsteady Navier–Stokes equations. Such technique is based on two residual-based error indicators that suitably drive the mesh and the timestep-length modifications. Adaptive simulations show that the presented strategy allows to obtain accurate solutions in efficient way.     

Enhancing integrated earthquake simulation with high performance computing

Integrated earthquake simulation (IES) is a seamless simulation of the three earthquake processes, namely, the earthquake hazard process, the earthquake disaster process and the anti-disaster action process. High performance computing (HPC) is essential if IES, or particularly, the simulation of the earthquake disaster process is applied to an urban area in which 10^4∼6 structures are located. IES is enhanced with parallel computation, and its performance is examined, so that virtual earthquake disaster simulation will be made for a model of an actual city by inputting observed strong ground motion. It is shown that parallel IES has fairly good scalability even when advanced non-linear seismic structure analysis is used.     

不规则结构隔震设计与研究

目的对比L型不规则隔震结构不同布置方案,确定最优方案并对最优方案进行结构减震分析．方法从建筑功能和减震效果两个方面评价3种不同方案,对最优方案进行抗风计算和地震作用下的非线性时程分析．结果不同方案会引起建筑功能和减震效果的不同,需要综合评价;L型隔震结构可以通过隔震层支座有效布置,使得结构质心和刚心尽量重合,减小了结构的扭转效应;最优方案在地震作用下的非线性时程分析结果显示结构减震效果良好,各项指标均满足规范要求．结论L型隔震结构可选用将隔震层以上结构完全连接的布置方案,既保持了良好的建筑功能,又获得了良好的减震效果,亦可以采用两个结构完全分开的布置方案．     

FFT 谱连续细化分析在频域模态参数识别中的应用

在频域模态参数识别法中,传递函数的精度对模态参数的识别结果有很大的影响。针对经典传递函数算法中存在高分辨率和平滑性不能同时满足的矛盾,本文提出了一种利用FFT谱连续细化算法对传递函数在峰值处和模态耦合密集处进行加密,进而利用Levy法对加密后的传递函数进行模态参数识别的方法。数值仿真结果表明,由于加密后提高了传递函数的分辨率和精度,应用Levy法在区分密集模态和提高模态参数识别结果、抗噪声方面有较大的改进。在某大型升船机振动台模型试验中,应用本文提出的方法取得了满意的结果。