A High-Performance Quadrilateral Flat Shell Element for Seismic Collapse Simulation of Tall Buildings and Its Implementation in OpenSees

Shear walls are important lateral force-resistant components of tall buildings. Hence, a reliable numerical model that can accurately represent the mechanical characteristics and large deformations of shear walls is critical for realistic collapse simulation of tall buildings. Based on the theory of generalized conforming element, a high-performance quadrilateral flat shell element, NLDKGQ, accounting for the large deformation using the updated Lagrangian formulation, is proposed herein and implemented in OpenSees. The reliability of NLDKGQ is validated using classical benchmark problems and reinforced concrete specimens. In addition, its capability in simulating the collapse of a tall building is also demonstrated.     

The Numerical Study of Base-Isolated Buildings Under Near-Field and Far-Field Earthquakes

The behavior of base-isolated building frame is investigated with the help of a numerical study for far-field and near-field earthquakes with directivity and fling-step effects. Both design-level and extreme-level earthquakes are considered. Selected response parameters are peak floor displacement, acceleration, base shear, and isolator displacement. Inelastic behavior of base-isolated structure during the earthquake is investigated performing nonlinear time history analysis of a ten-story building frame. This study shows that base isolation is not effective for near-field earthquakes. Even for design-level earthquake, the frame gets significantly into inelastic range for earthquakes with fling-step effect.     

高精度变形监测预警系统在明显陵遗址保护中的应用研究

为在遗址完整性保护与滑坡灾害预警方面制定切实有效的解决方案,使用基于高精度全球卫星定位系统GPS与远程遥测终端RTU的高精度变形监测预警系统,并结合无线通讯方式实现对遗址保护区陵墓边坡的安全监测。系统完成墓冢内部环境监测与滑坡方位的监测定位。并通过通用无线分组业务GPRS方式将监测参数与警情信号实时传输至监控中心,在管理软件平台上进行实时显示并提示安保人员及时出警。该系统可针对不同规模野外文物保护区和古墓群实现有效的滑坡监测与预警防范,具有广泛的应用推广价值。     

Elastic Displacement Spectrum-Based Design Approach for Buckling-Restrained Braced Frames

The design focus for a buckling-restrained braced frame (BRBF) is that the buckling-restrained braces (BRBs) dissipate most of the seismic energy while the main frame retains a degree of elastic stiffness under a major earthquake. An elastic displacement spectrum based design method is presented in this article, which can directly determine the sectional area of the BRBs. The yield displacement in the roof of the main frame is taken as the target displacement under a major earthquake. An elastic displacement design spectrum is used to solve the target period of the BRBF. To validate this method, a six-story buckling-restrained braced steel frame is designed using the proposed method, and a series of nonlinear response history analyses (RHAs) are performed to verify the design result. The example shows that the required BRB area can be simply and accurately determined by the proposed method. The error between the given target displacement and the RHA results is 4.0% and 21.3% for BRBFs designed with BRB yield strength of 235 Mpa and 100 Mpa, respectively.     

Stochastic Seismic Response of Pipelines with Corrosion

For aging pipelines, corrosion gradually appears inside and outside during in-service time. However, because the uncertainty characteristics of the soil around the pipeline and conveying material in the pipeline, the generation and development processes of the pipeline corrosion would be stochastic processes. This background must be taken into account in the seismic response analysis of the pipeline. In this article, using Markov chain with absorbing barrier, a model simulating the evolution of the pipeline corrosion is presented. This model divides a pipeline into several segments and obtains the distribution probabilities of the cross section areas of the segments. Elastic foundation beam method and random perturbation method are used to obtain the seismic response of the pipeline with corrosion. To validate the proposed method, two pipelines are investigated in detail. The mean and standard deviation of the displacements and stress of the pipeline under earthquake are evaluated by the proposed method. Also, the results of one pipeline are compared with Monte Carlo random simulation. The numerical results show that the proposed model can reasonably predict the seismic response of the pipeline with corrosion.     

Multiple Degrees of Freedom Positioning Correction for Hybrid Simulation

This study proposes a high-precision positioning correction method for multiple degree-of-freedom loading units in hybrid simulation. These loading units can impose inaccurate displacements to the specimens due to the elastic deformation at the reaction wall or connections. To compensate for these displacement errors, an online correction method adjusts the displacement command by the difference between the target and achieved displacement. This correction method also accompanies an accurate 6DOF monitoring system to detect the displacement errors. Two examples of hybrid simulation tests are provided to demonstrate the precise displacements attained on the specimens through this control method.     

虎丘塔的维修加固与变形测量

对虎丘塔的沉降、位移、层面倾斜等指标进行了测量,进而了解塔体的结构趋向变化。经过维修加固,虎丘塔塔体倾斜得到控制,现在塔体变化趋于稳定状态。     

出土饱水竹简失水干缩的复形研究——以海昏侯墓葬出土竹简等为例

失水干缩竹简不仅改变了竹简的形貌,而且字迹无法辨认,不能进行考古释文,极大地影响了其承载的历史价值和研究价值。通过海昏侯墓葬等出土竹简等残片的干缩复形研究实验,对复形前后外形尺寸、化学组分、微观结构等方面进行比较。结果表明:经生物碱和表面活性剂等材料浸润后的干缩竹简残片,外形尺寸可恢复到干缩前的98%以上,竹简残片内部干缩变小的空隙结构得到恢复,化学组分无明显变化。运用该技术对干缩竹简进行复形处理,复形后的竹简基本恢复到饱水时的状态,而且对字迹无损伤。     

Diffraction around a Semi-Parabolic Canyon in an Elastic Half-Space by Out-of-Plane SH-Waves,II: Rocking and Resultant Rotations

This paper is the second of the two papers, discussing the rocking and resultant component of rotations, with the torsional components of motions presented earlier in the first paper for the case of out-of-plane SH waves excitation on a semi-parabolic canyon. The rotational motions are gaining importance in recent years in the field of strong-motion seismology and earthquake engineering. Many previous papers on out-of-plane SH waves excitation presented the associated torsion rotational motions, when in fact there is also a rocking rotational component of motions. Both the rocking and torsion rotational motions, in as much as the translational motions, had shown to play an important role in structural responses, even though rotations are not incorporated into building design codes at present. Studying the rotational motions can thus help to a better understanding of the behavior of surface topographies that are in the vicinity of structures in the event of seismic excitation. This paper included, besides the additional rocking motions, also the resultant rotational motions combining torsion and rocking.     

Experimental Evaluation of Seismic Performance of Squat RC Structural Walls with Limited Ductility Reinforcing Details

This article describes an experimental study carried out on of reinforced concrete (RC) walls of less confining reinforcement than that recommended by ACI 318. A total of eight RC walls with boundary elements comprising of five walls with aspect ratio of 1.125 and three walls with aspect ratio of 1.625 were tested by subjecting them to low levels of axial compression loading and simulated seismic loading, to examine the structural performance of the walls with limited transverse reinforcement. Conclusions are reached concerning the failure mode, drift capacity, strength capacity, components of top deformation, and energy dissipation characteristics of walls on the seismic behavior with limited transverse reinforcement. The influences of axial loading, transverse reinforcement in the wall boundary elements, and the presence of construction joints at the wall base on the seismic behavior of walls are also studied in this paper. Lastly, reasonable strut-and-tie models are developed to help in understanding the force transfer mechanism in the walls tested.