Fragility curves of concrete bridges retrofitted by column jacketing

The Northridge earthquake inflicted various levels of damage upon a large number of Caltrans' bridges not retrofitted by column jacketing.In this respect,this study represents results of fragility curve development for two (2) sample bridges typical in southern California,strengthened for seismic retrofit by means of steel jacketing of bridge columns.Monte Carlo simulation is performed to study nonlinear dynamic responses of the bridges before and after column retrofit.Fragility curves in this study are represented by lognormal distribution functions with two parameters and developed as a function of PGA.The sixty (60) ground acceleration time histories for the Los Angeles area developed for the Federal Emergency Management Agency (FEMA) SAC (SEAOC-ATC CUREe) steel project are used for the dynamic analysis of the bridges. The improvement in the fragility with steel jacketing is quantified by comparing fragility curves of the bridge before and after column retrofit.In this first attempt to formulate the problem of fragility enhancement,the quantification is made by comparing the median values of the fragility curves before and after the retrofit.Under the hypothesis that this quantification also applies to empirical fragility curves developed on the basis of Northridge earthquake damage,the enhanced version of the empirical curves is developed for the ensuing analysis to determine the enhancement of transportation network performance due to the retrofit.

A 600-m Jacketing Line of Cable-In-Conduit Conductor (CICC) and the First 600-m Dummy Cable

A cable-in-conduit conductor(CICC ) production line was designed and constructed in Institute of Plasma Physics of Chinese Academy of Sciences (IPPCAS) by the end of 2000. It can produce a length of 600 meters and three kinds of sections of 20.8±0. 1×20.8±0.1, 20.4±0. 1×20.4± 0.1 and 18.6±0.1×18.6±0.1mm2. If the rollers of the shaping machine are changed, it can also produce other sizes of CICCs. So-called inserting-cable technology is adopted in this production line, where the procedures consist of tube pre-treatment (cleaning, pressure and leakage testing, end cutting), conduits butt-welding, six kinds of quality checking (endoscopy, dye penetration, pressure control, leakage testing, ultrasonic inspection and X-ray testing), cable inserting, shaping (compacting & squaring), pre-bending & winding and final checking. Now all the instruments and facilities required for these technologies have been installed and got ready. Some key technologies have been explored and good results obtained. Some short samples were produced and a 600 meters long sample was made out in August, 2001.

Wind-Vortex-Induced Vibrations of a Deepwater Jacket Pipe and Vibration Suppression Using a Nonlinear Energy Sink

The purpose of this study is to investigate the suppression effect of a nonlinear energy sink(NES)on the wind-vortex-induced pipe vibration and explore the influence of damping,stiffness,and NES installation position on the suppression effect.In this work,the wind-vortex-induced vibration of an elastic pipe of a deepwater jacket was studied,and vibrations were suppressed by using an NES.A van der Pol wake oscillator was used to simulate vortex-induced force,and the dynamic equation of the pipe considering the NES was established.The Galerkin method was applied to discretize the motion equation,and the vortex-induced vibration(VIV)of the pipe at reduced wind speeds was numerically analyzed.The novelty of this research is that particle swarm optimization was used to optimize the parameters of the NES to improve vibration suppression.The influence of the installation position,nonlinear stiffness,and damping parameters of the NES on vibration suppression was analyzed.Results showed that the optimized parameter combinations of the NES can effectively reduce wind-vortex-induced pipe vibration.The installation position of the NES had a significant effect on vibration suppression,and the midpoint of the pipe was the optimal NES installation position.An increase in stiffness or a 10% decrease in damping may cause vibration suppression failure.The results of this study provide some guidance for VIV suppression in deepwater jacket pipes.

砂土中长径比对三筒基础水平承载特性的影响

The tripod foundation(TF)is a prevalent foundation configuration in contemporary engineering practices.In comparison to a single pile,TF comprised interconnected individual piles,resulting in enhanced bearing capacity and stability.A physical model test was conducted within a sandy soil foundation,systematically varying the length-to-diameter ratio of the TF.The investigation aimed to comprehend the impact of altering the height of the central bucket on the historical horizontal bearing capacity of the foundation in saturated sand.Additionally,the study scrutinized the historical consequences of soil pressure and pore water pressure surrounding the bucket throughout the loading process.The historical findings revealed a significant enhancement in the horizontal bearing capacity of the TF under undrained conditions.When subjected to a historical horizontal loading angle of 0°for a single pile,the multi-bucket foundation exhibited superior historical bearing capacity compared to a single-pile foundation experiencing a historical loading angle of 180°under pulling conditions.With each historical increment in bucket height from 150 mm to 350 mm in 100 mm intervals,the historical horizontal bearing capacity of the TF exhibited an approximately 75%increase relative to the 150 mm bucket height,indicating a proportional relationship.Importantly,the historical internal pore water pressure within the bucket foundation remained unaffected by drainage conditions during loading.Conversely,undrained conditions led to a historical elevation in pore water pressure at the lower side of the pressure bucket.Consequently,in practical engineering applications,the optimization of the historical bearing efficacy of the TF necessitated the historical closure of the valve atop the foundation to sustain internal negative pressure within the bucket.This historical measure served to augment the historical horizontal bearing capacity.Simultaneously,historical external loads,such as wind,waves,and currents,were directed towards any individual bucket within the TF for optimal historical performance.

OH Diffusion in Silica Glass Preform During Jacketing Process by Oxy-Hydrogen Burner

Radial distribution of OH diffusion in silica glass preform during jacketing process using a oxy-hydrogen burner was investigated by FTIR spectroscopy. The OH peaks at the jacketing boundary and the surface of the preform were found to be due to diffusion of OH incorporated from the burner.

The next GORE-TEX for jackets?

Columbia is a world-renowned manufacturer of outdoor products.Its product range covers all aspects of outdoor equipment such as jackets,down jackets,outdoor footwear,backpacks and accessories.In the outdoor industry,Columbia was the first brand to propose a three-in-one garment design concept.This practical design has since been adopted by almost every outdoor brand.The Columbia Jacket is positioned for urban outdoor recreation.Its rugged materials and design make it suitable for low-altitude outdoor sports as well as urban commuting.

Upgrading jackets for spring

When the gentle breeze of spring starts to fill the air,it's often a time of transition,where the chill of winter gives way to the warmth of the coming season.However,for those who love the outdoors,spring can still present its own set of challenges,especially when it's time to choose the right jacket.Whether you're hiking in the hills,exploring the trails,or just taking a leisurely walk in the park,having a jacket that offers the perfect blend of warmth,comfort,and breathability is crucial.We'll delve into the various options available for jackets that are perfect for the outdoors in spring.

Why own an Arc’teryx jacket?

Arc’teryx’s Beta AR Jacket sets a new bar in terms of what a mainstream outdoor jacket can do.You’ll turn around and charge headfirst into a rainstorm with this fully impermeable outer layer that packs in everything you need to lock in your core and stay dry.Unlike some jackets,the best part is that this jacket also pays dividends in sunny weather.While it’s designed for nasty weather,it stays comfortable when the storm passes away.The company’s high-tech waterproof membrane simultaneously wicks moisture and finally kicks that classic clammy raincoat feeling to the curb.

Hydrodynamic Characteristics of Three-Bucket Jacket Foundation for Offshore Wind Turbines During the Lowering Process

The three-bucket jacket foundation is a new type of foundation for offshore wind turbine that has the advantages of fast construction speed and suitability for deep water. The study of the hoisting and launching process is of great significance to ensure construction safety in actual projects. In this paper, a new launching technology is proposed that is based on the foundation of the three-bucket jacket for offshore wind turbine. A complete time domain simulation of the launching process of three-bucket jacket foundation is carried out by a theoretical analysis combined with hydrodynamic software Moses. At the same time, the effects of different initial air storage and sea conditions on the motion response of the structure and the hoisting cable tension are studied. The results show that the motion response of the structure is the highest when it is lowered to 1.5 times the bucket height. The natural period of each degree of freedom of the structure increases with the increase of the lowering depth. The structural motion response and the hoisting cable tension vary greatly in the early phases of Stages Ⅰ and Ⅲ, smaller in Stage Ⅱ, and gradually stabilize in the middle and late phases of Stage Ⅲ.

Modal Parameter Identification Method of Jacket Platform Structure Based on AFDD and Optimized FBFFT

Offshore platforms are susceptible to structural damage due to prolonged exposure to random loads,such as wind,waves,and currents.This is particularly true for platforms that have been in service for an extended period.Identifying the modal parameters of offshore platforms is crucial for damage diagno sis,as it serves as a prerequisite and foundation for the process.Therefore,it holds great significance to prioritize the identification of these parameters.Aiming at the shortcomings of the traditional Fast Bayesian Fast Fourier Transform(FBFFT) method,this paper proposes a modal parameter identification method based on Automatic Frequency Domain Decomposition(AFDD) and optimized FBFFT.By introducing the AFDD method and Powell optimization algorithm,this method can automatically identify the initial value of natural frequency and solve the objective function efficiently and simply.In order to verify the feasibility and effectiveness of the proposed method,it is used to identify the modal parameters of the IASC-ASCE benchmark model and the j acket platform structure model,and the Most Probable Value(MPV) of the modal parameters and their respective posterior uncertainties are successfully identified.The identification results of the IASC-ASCE benc hmark model are compared with the identification re sults of the MODE-ID method,which verifies the effectivene ss and accuracy of the proposed method for identifying modal parameters.It provides a simple and feasible method for quantifying the influence of uncertain factors such as environmental parameters on the identification results,and also provide s a reference for modal parameter identification of other large structures.

海上风电螺旋桩侧向承载能力分析

The rapid development of offshore wind power and the need to move to deeper sea areas while reducing costs per kilowatt necessitate the employment of a new jacket and helical pile combination.This new combination combines the advantages of both jacket structures and helical piles and provides a superior bearing capacity and installation efficiency compared to conventional pile foundations.Foundations account for 25%-34%of the overall cost of construction,but the use of this new foundation would be highly significant for the further development of offshore wind power.This study presents numerical results for the horizontal bearing capacity when horizontal displacement is applied,focusing on the bearing capacity and characteristics of the helical pile jacket foundation as well as the differences between the bearing mechanisms and failure modes of normal pile and helical pile types.ABAQUS model parameters are obtained through trial calculations based on actual engineering data,and the finite element model(FEM)is validated using data from a model experiment.Subsequently,different FEMs are established,and numerical results are compared and presented.Through a comparison between a normal pile jacket foundation and a helical pile jacket foundation with different helical blade numbers,the differences in the bearing mechanisms and failure modes are revealed.The failure of the normal pile jacket foundation is instantaneous and sudden,whereas that of the helical pile foundation is incremental and accumulative.These data highlight the most significant contributions and vulnerabilities of the one-pile side of the foundation and suggest that the addition of blades on the one-pile side is the most effective way of improving the foundation’s bearing performance.In addition,the interaction between the compression side and tension side is analyzed in relation to differing the relative magnitudes of their bearing capacities.

ITER线圈终端盒真空隔断的结构设计与分析

真空隔断是真空盒体与低温分配管路之间的连接接口。本文主要介绍了真空隔断的结构设计,并应用有限元分析软件ANSYS Workbench建立了真空隔断的三维实体模型,对其进行了热和结构的耦合分析,获得真空隔断故障态时的应力和温度分布以及传导热。分析的结果为真空隔断的研制提供了可靠的理论依据。

Dynamic performance of angle-steel concrete columns under low cyclic loading-I:Experimental study

This paper describes low cyclic loading testing of nine angle-steel concrete column （ASCC） specimens. In the tests, the influence of the shear-span ratio, axial compression ratio and shear steel plate ratio on the hysteretic behavior, energy dissipation, strength degradation, stiffness degradation, skeleton curve and ductility of the ASCCs is studied. Based on the test results, some conclusions are presented. The P-A and sectional M -φ hysteretic models for the ASCCs are presented in a companion paper （Zheng and Ji, 2008）.

Parametric study on performance of bridge retrofitted by unseating prevention devices

Over the past decade, seismically induced damage to bridges has been widely reported following major earthquakes such as the 1994 Northridge, 1995 Kobe and 1999 Chi-Chi events. Since these earthquakes, restrainers and stoppers have been installed on bridges to prevent unseating and excessive displacements, respectively. Alternatively, column jacketing has also been proven to be effective. However, the enhanced shear strength may result in extra retrofitting works on the footing. For bridges damaged in the Chi-Chi earthquake, investigations revealed that most bridge columns experienced none-to-minor damage in the longitudinal direction. The reason for this unexpected performance was the construction practice of using a rubber bearing, which is an unbolted design that may slide under large lateral forces. In this paper, parametric studies on simply-supported bridges retrofitted by a restrainer or concrete shear key along the longitudinal and transverse axes were carried out. The research focuses on finding suitable combinations of the design force and gap spacing so the restrainer and concrete shear key can be used as an unseating prevention device, with respect to the allowable column damage in terms of displacement ductility under near-fault type earthquakes. A two-lane PCI-girder bridge was selected as the benchmark model. In the longitudinal direction, a total of nine combinations considering yielding strength and gap spacing for the restrainer were analyzed; while parameters for the concrete shear key were divided into three shear force levels and three gap spacings. In the transverse direction, a similar approach was adapted, except smaller gap spacing was used. For each of the above mentioned earthquakes, seven input ground motions were selected and their PGAs were adjusted to 0.36g and 0.45g as the Design earthquake and Maximum Considerable Earthquake, respectively. Based on the results of nonlinear time history analyses, proper parameters to design the restrainers and concrete shear keys are obtained. Responses obtained from numerical simulations under the Chi-Chi earthquake leaded to new implications to design those devices. Restrainer should not exceed its breaking strain and sufficient unseating length will be needed always. Concrete Shear key was determined by considering both displacement demand of the superstructure and displacement ductility of the column at the same time. Further study is needed to provide optimal design parameters for use in performance based bridge design.

基于GPU的MATLAB计算与仿真研究

图形处理单元(GPU)已经成为当今的主流计算系统的一个组成部分,现代GPU不仅是一个功能强大的图形引擎,也是一个高度并行的可编程处理器,GPU的峰值运算和内存带宽往往大幅超出其CPU所对应的峰值和内存带宽。本文介绍了基于GPU通用计算框架的JACKET加速MATLAB的计算仿真方法,通过FFT算法得出仿真结果,分析在CPU和GPU运行环境下的GFLOPS和加速比,最后得出基于GPU的MATLAB计算仿真程序运行效率在JACKET的加速下大大提高了。

图像处理的GPU加速技术研究

通过Matlab和Visual C++两个平台,实现了对图像工程的并行加速处理,并且通过Jacket,CUDA两种加速方案的介绍,进一步了解使用GPU高性能并行计算的工作流程以及性能效益。最后,给出了通过并行处理之后的关于两个图像工程计算性能的测试结果及比对。结果证明,经并行处理后的图像工程在计算效率方面有显著提高,结果精确,计算耗时小。

Seismic retrofi tting of RC columns with RC jackets and wing walls with different structural details

An original reinforced concrete(RC) column and four strengthened specimens, two with RC jackets and two with wing walls, were tested in this study. The original column specimen was designed to comply with older(pre-1999) design standards so that the usual detailing defi ciencies in existing school buildings in Taiwan could be simulated. Two different structural details were chosen to fabricate the full-scale specimens for each retrofi tting technique. The study confi rmed that either RC jacketing or the installation of wing walls with two different structural details can effectively improve the stiffness and strength of an existing column. RC jacketing shows a better improvement in energy dissipation and ductility when compared to the columns with wing walls installed. This is because the two RC jacketed columns experienced a fl exural failure, while a shear failure was found in the two columns with the wing walls installed, and thus led to a drastic decrease of the maximum lateral strengths and ductility. Since many factors may affect the installation of a post-installed anchor, it is better to use standard hooks to replace post-installed anchors in some specifi c points when using RC jacketing or installing wing walls.

有限域上快速分块Jacket变换

提出了一种在有限域上的简单上闭链分块逆Jacket变换(CBIJT)。为将高阶的上闭链逆Jacket矩阵(CBIJM)因式分解成单位矩阵和低阶稀疏矩阵,考虑运用带来快速变换的连续结构来减少计算负荷。采用类似的递归方式分析两个CBIJT,即单维和双维CBIJT。这两个CBIJT为单位矩阵和低阶CBIJT的多重Kronecker积。

应用CUDA加速免疫算法——Jacket与Matlab实现

作为继遗传算法后新兴的一种人工智能算法——免疫算法最近几年在理论研究和工程应用方面得到了极大的关注和发展,但由于免疫算法本身机理的并行性使得其在通用CPU上进行测试和运行时效率低下,不利于评价算法的性能。通过通用并行计算架构CUDA使用GPU运行则更符合算法本身机理,大幅节省运行时间,降低硬件成本。

动态模式识别算法的GPU平台实现

研究动态模式识别算法在GPU并行计算平台的实现。随着GPGPU(通用计算图形处理器)硬件的发展,基于GPU的大规模并行计算技术将有效地处理动态模式识别算法带来的海量计算问题。文中通过介绍动态模式识别算法,对算法中涉及的巨大计算量进行分析,并针对性地对其中密集计算部分进行并行化分解,移除原算法中在执行中存在的依赖关系,最终得到算法在特定的GPU平台———Jacket上的并行计算实现。实例验证表明,相比于原CPU串行程序,在GPU上运行的并行化程序能实现明显加速,因而具有很好的工程应用价值。