Characteristics of viscous debris flow in a drainage channel with an energy dissipation structure

A new type of drainage channel with an energy dissipation structure has been proposed based on previous engineering experiences and practical requirements for hazard mitigation in earthquakeaffected areas.Experimental studies were performed to determine the characteristics of viscous debris flow in a drainage channel of this type with a slope of 15%.The velocity and depth of the viscous debris flow were measured,processed,and subsequently used to characterize the viscous debris flow in the drainage channel.Observations of this experiment showed that the surface of the viscous debris flow in a smooth drainage channel was smoother than that of a similar debris flow passing through the energy dissipation section in a channel of the new type studied here.However,the flow patterns in the two types of channels were similar at other points.These experimental results show that the depth of the viscous debris flow downstream of the energy dissipation structure increased gradually with the length of the energy dissipation structure.In addition,in the smooth channel,the viscous debris-flow velocity downstream of the energy dissipation structure decreased gradually with the length of the energy dissipation structure.Furthermore,theviscous debris-flow depth and velocity were slightly affected by variations in the width of the energy dissipation structure when the channel slope was 15%.Finally,the energy dissipation ratio increased gradually as the length and width of the energy dissipation structure increased;the maximum energy dissipation ratio observed was 62.9%(where B = 0.6m and L/w = 6.0).

Nonequilibrium Thermodynamic and Dissipative Structure Mechanism of Fluidized Beds

Fluidized beds are nonlinear dynamic systems that exchange mass and energy with outside. They are governed not only byfluid dynamics, but by thermodynamics, especially the second law of thermodynamics as well. According to Prigogine's dissipative structure theory, the following have been concluded: (l) a fixed bed is on thermodynamic blanch, and bubbling, turbulent and fast beds areon the dissipatve structure branches. (2) Entropy in fluidized beds is divided into tWo parts: entropy production and entropy flux. The latter increases with gas velocity and decreases with pressure of the systems. That means the entropy of a system may reduce and the systemwith higher gas velocity behaves as dissipative structure characteristics. (3) For a giVen velocity, a fluidized bed operates stably on thewhole, but it is unstable to local gas-solid phases. The unstable phases are described by fluid dynamic equations, While the minimum ofsystem energy function assures whole stability of the system. (4) A transition criterion of a bubbling bed is derived from Prigogine's stability theory.

Response Spectrum Analysis of 7-story Assembled Frame Structure with Energy Dissipation System

Viscoelastic damper is an effective passive damping device,which can reduce the seismic response of the structure by increasing the damping and dissipating the vibration energy of structures.It has a wide application prospect in actual structural vibration control because of simple device and economical material.In view of the poor seismic behaviors of assembled frame structure connections,various energy dissipation devices are proposed to improve the seismic performance.The finite element numerical analysis method is adopted to analyze relevant energy dissipation structural parameters.The response spectrum of a 7-story assembled frame structure combined the ordinary steel support,ordinary viscoelastic damper,and viscoelastic damper with displacement amplification device is analyzed.The analysis results show that the mechanical behavior of assembled frame structure with ordinary steel supports are not significantly different from those without energy dissipation devices.The assembled frame structure with viscoelastic damper has better seismic performance and energy dissipation,especially for the viscoelastic damper with displacement amplification devices.The maximum value of inter-story displacement angle decreases by 32.24%;the maximum floor displacement decreases by 31.91%,and the base shear decreases by 13.62%compared with the assembled frame structures without energy dissipation devices.The results show that the seismic fortification ability of the structure is significantly improved,and the overall structure is more uniformly stressed.The damping structure with viscoelastic damper mainly reduces the dynamic response of the structure by increasing the damping coefficient,rather than by changing the natural vibration period of the structure.This paper provides an effective theoretical basis and reference for improving the energy dissipation system and the seismic performance of assembled frame structures.

Energy evolution and structural health monitoring of coal under different failure modes:An experimental study

Structural instability in underground engineering,especially in coal-rock structures,poses significant safety risks.Thus,the development of an accurate monitoring method for the health of coal-rock bodies is crucial.The focus of this work is on understanding energy evolution patterns in coal-rock bodies under complex conditions by using shear,splitting,and uniaxial compression tests.We examine the changes in energy parameters during various loading stages and the effects of various failure modes,resulting in an innovative energy dissipation-based health evaluation technique for coal.Key results show that coal bodies go through transitions between strain hardening and softening mechanisms during loading,indicated by fluctuations in elastic energy and dissipation energy density.For tensile failure,the energy profile of coal shows a pattern of “high dissipation and low accumulation” before peak stress.On the other hand,shear failure is described by “high accumulation and low dissipation” in energy trends.Different failure modes correlate with an accelerated increase in the dissipation energy before destabilization,and a significant positive correlation is present between the energy dissipation rate and the stress state of the coal samples.A novel mathematical and statistical approach is developed,establishing a dissipation energy anomaly index,W,which categorizes the structural health of coal into different danger levels.This method provides a quantitative standard for early warning systems and is adaptable for monitoring structural health in complex underground engineering environments,contributing to the development of structural health monitoring technology.

Experimental study of friction dissipators for seismic protection of building structures

This paper presents the results from unidirectional shaking table tests of two reduced scale steel models of a building frame, with one and two floors, respectively. These frames incorporate friction dissipators at every floor. The inputs are sine-dwells and artificial and registered earthquakes. This study is part of a larger research project aiming to assess the seismic efficiency of friction dissipators by means of an integrated numerical and experimental approach. Inside this framework, the main objectives of these experiments are to： （i） collect a wide range of results to calibrate a numerical model derived within the project, （ii） clarify some of the most controversial issues about friction dissipators （including behavior for inputs containing pulses, capacity to reduce resonance peaks, introduction of high frequencies in the response, and self- generated eccentricities）, （iii） better understand their dynamic behavior, （iv） provide insight on the feasibility and reliability of using simple friction dissipators for seismic protection of building structures and （v） characterize the hysteretic behavior of these devices. Most of these objectives are satisfactorily reached and relevant conclusions are stated.

Energy analysis and criteria for structural failure of rocks

The intrinsic relationships between energy dissipation,energy release,strength and abrupt structural failure are key to understanding the evolution of deformational processes in rocks.Theoretical and experimental studies confirm that energy plays an important role in rock deformation and failure.Dissipated energy from external forces produces damage and irreversible deformation within rock and decreases rock strength over time.Structural failure of rocks is caused by an abrupt release of strain energy that manifests as a catastrophic breakdown of the rock under certain conditions.The strain energy released in the rock volume plays a pivotal role in generating this abrupt structural failure in the rocks.In this paper,we propose criteria governing（1） the deterioration of rock strength based on energy dissipation and（2） the abrupt structural failure of rocks based on energy release.The critical stresses at the time of abrupt structural failure under various stress states can be determined by these criteria.As an example,the criteria have been used to analyze the failure conditions of surrounding rock of a circular tunnel.

Damping characteristics of friction damped braced frame and its effectiveness in the mega-sub controlled structure system

Based on energy dissipation and structural control principle, a new structural configuration, called the megasub controlled structure （MSCS） with friction damped braces （FDBs）, is first presented. Meanwhile, to calculate the damping coefficient in the slipping state a new analytical method is proposed. The damping characteristics of one-storey friction damped braced frame （FDBF） are investigated, and the influence of the structural parameters on the energy dissipation and the practical engineering design are discussed. The nonlinear dynamic equations and the analytical model of the MSCS with FDBs are established. Three building structures with different structural configurations, which were designed with reference to the conventional mega-sub structures such as used in Tokyo City Hall, are comparatively investigated. The results illustrate that the structure presented in the paper has excellent dynamic properties and satisfactory control effectiveness.

Improving Concrete Containment Structures Associated with Fixed-Cone Valves

Fixed-Cone valves are often used to dissipate energy and regulate flow at the low level outlet works of dams. Fixed-Cone valves, also known as Howell-Bunger valves, create an expanding conical jet allowing the energy of the water to dissipate over a large area. However, in many applications constructing the large stilling basin necessary for these valves is either not possible or not feasible. In order to reduce the relative size of the stilling basin, hoods or concrete containment structures have been used in conjunction with Fixed-Cone valves. This paper discusses the use of baffles in concrete containment structures in order to dissipate energy in a considerably confined space. It was determined that using baffles, in place of a deflector ring and end sill (Used in traditional containment structures.), significantly improves the function of containment structures by reducing downstream flow velocities and improving flow patterns and stability. This information will be useful to engineers allowing them to minimize scour and erosion associated with concrete containment structures.

DYNAMIC RESPONSE AND ENERGY DISSIPATION ANALYSIS OF THE WALL WITH HORIZONTAL SHORT KEYWAYS AND LOWRISE SHEARWALL

A new type of ductile lowrise shearwall with many short horizontalkeyways is proposed in this paper in order to improve the earthquake resistant behav-ior of ordinary lowrise shearwall.The behavior of this wall is studied through low-frequency cyclic loading test.Based on the test results,the paper puts forward thedifferent restoring force models for different lowrise shearwalls,and a program fortheir nonlinear dynamic analysis is worked out.Thr(?)h directly inputting earth-quake waves,the paper analyses the dynamic response and energy dissipation of 3types of lowrise shearwalls.The calculation results dem(?)strate that the newly de-vised ductile shearwall has good earthquake resistant behavior.

Estimation of Turbulent Kinetic Energy Dissipation Rate in the Bottom Boundary Layer of the Pearl River Estuary

A structure function approach is applied to estimate the turbulent kinetic energy （TKE） dissipation rate in the bottom boundary layer of the Pearl River Estuary （PRE）. Simultaneous measurements with an acoustic Doppler velocimeter （ADV） supplied independent data for the verification of the structure function method. The results show that, 1） the structure function approach is reliable and successfully applied method to estimate the TKE dissipation rate. The observed dissipation rates range between 8.3 ×10^-4 W/kg and 4.9× 10^-6 W/kg in YM01 and between 3.4×10^-4 W/kg and 4.8×10^-7 W/kg in YM03, respectively, while exhibiting a strong quarter-diurnal variation. 2） The balance between the shear production and viscous dissipation is better achieved in the straight river. This first-order balance is significantly broken in the estuary by non-shear production/dissipation due to wave-induced fluctuations.

Rapid Prediction of Structural Responses of Double-Bottom Structures in Shoal Grounding Scenario

This study presents a simplified analytical model for predicting the structural responses of double-bottom ships in a shoal grounding scenario. This solution is based on a series of analytical models developed from elastic-plastic mechanism theories for different structural components, including bottom girders, floors, bottom plating, and attached stiffeners. We verify this simplified analytical model by numerical simulation, and establish finite element models for a typical tanker hold and a rigid indenter representing seabed obstacles. Employing the LS-DYNA finite element solver, we conduct numerical simulations for shoal-grounding cases with a wide range of slope angles and indentation depths. In comparison with numerical simulations, we verify the proposed simplified analytical model with respect to the total energy dissipation and the horizontal grounding resistance. We also investigate the interaction effect of deformation patterns between bottom structure components. Our results show that the total energy dissipation and resistances predicted by the analytical model agree well with those from numerical simulations.

Assessment of the ballistic response of honeycomb sandwich structures subjected to offset and normal impact

In the present study,experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores.The high velocity impact tests were carried out using a compressed air gun.A sharp conical nosed projectile was impacted normally and with some offset distance(20 mm and 40 mm).The deformation,failure mode and energy dissipation characteristics were obtained for both kinds of loading.Moreover,the explicit solver was run in Abaqus to create the finite element model.The numerically obtained test results were compared with the experimental to check the accuracy of the modelling.The numerical result was further employed to obtain strain energy dissipation in each element by externally running user-defined code in Abaqus.Furthermore,the influence of inscribe circle diameter and cell wall and face sheet thickness on the energy dissipation,deformation and failure mode was examined.The result found that ballistic resistance and deformation were higher against offset impact compared to the normal impact loading.Sandwich panel impacted at 40 mm offset distance required 3 m/s and 1.9 m/s more velocity than 0 and 20 mm offset distance.Also,increasing the face sheet and wall thickness had a positive impact on the ballistic resistance in terms of a higher ballistic limit and energy absorption.However,inscribe circle diameter had a negative influence on the ballistic resistance.Also,the geometrical parameters of the sandwich structure had a significant influence on the energy dissipation in the different deformation directions.The energy dissipation in plastic work was highest for circumferential direction,regardless of impact condition followed by tangential,radial and axial directions.

Utilization of IDRIZI Wall System on Building Structures-Characteristic Study Case

Perhaps the best way to demonstrate the gained improvements in seismic performance of buildings, integrated with IDRIZI infill walls, is to analyse typical building structures subjected to real case earthquake scenarios. This paper presents obtained analytical results for a characteristic 2D frame structure which （besides the self-weight, superimposed dead loads and live loads） is subjected to real earthquake ground motions. This study case treats three story planar RC （reinforced concrete） frame opened on the ground story while its upper stories are infilled with classical masonry walls. The purpose of this study case is to demonstrate ＂quantitatively＂ the seismic performance of this frame structure and, more importantly, to estimate the level of seismic response improvements of the frame when at its ground story is utilized IDRIZI infill wall with door opening. The seismic action considered for this study case is a representation of the 1979 Tivari earthquake, Montenegro. Ultimately, this study demonstrates the remarkable benefits the structure gains （in terms of seismic performance and safety） by the use of IDRIZI wall system as a constitutive part of the 2D frame structure.

Seismic design of low-rise steel building frames with self-centering hybrid damping connections

This paper develops a practice-oriented seismic design procedure for an emerging lateral force resisting system.The system combines the favorable re-centering feature with the attractive hybrid damping capacity.The system overcomes the detrimental frame expansion effect that occurs in conventional self-centering building frames without the cost of building space.Following the proposed design procedure,multiple designs with different parameters to achieve performance objectives were performed for a representative three-story building in which the considered lateral force resisting system is used to resist the seismic forces.Nonlinear response history analyses were performed for the designs to evaluate the applicability and adequacy of the proposed design approach.Based on the analyses conducted in this research,it was found that the considered system designed using the proposed approach can meet both transient and residual inter-story drift requirements specified for the selected performance objectives.While an initial design per the proposed design approach may be inadequate,the re-design strategy recommended can help transform the design to an acceptable one after only one round of modification.Moreover,the composition of hybrid damping may affect the maximum floor acceleration responses.In this study,the maximum floor acceleration can be reduced 12.75%at most by replacing hysteretic damping with viscous damping.This should be included in design consideration in the proposed approach through adjusting the hybrid damping composition.

Hierarchical Voronoi Structure Inspired by Cat Paw Pads Substantially Enhances Landing Impact Energy Dissipation

When a human lands from a high drop,there is a high risk of serious injury to the lower limbs.On the other hand,cats can withstand jumps and falls from heights without being fatally wounded,largely due to their impact-resistant paw pads.The aim of the present study was to investigate the biomechanism of impact resistance in cat paw pads,propose an optimal hierarchical Voronoi structure inspired by the paw pads,and apply the structure to bionic cushioning shoes to reduce the impact force of landing for humans.The microstructure of cat paw pads was observed via tissue section staining,and a simulation model was reconstructed based on CT to verify and optimize the structural cushioning capacity.The distribution pattern,wall thickness of compartments,thickness ratio of epidermis and dermis,and number of compartments in the model were changed and simulated to achieve an optimal composed structure.A bionic sole was 3D-printed,and its performance was evaluated via compression test and a jumping-landing experiment.The results show that cat paw pads are a spherical cap structure,divided from the outside to the inside into the epidermis,dermis,and compartments,each with different cushioning capacities.A finite element simulation of different cushioning structures was conducted in a cylinder with a diameter of 20 mm and a height of 10 mm,featuring a three-layer structure.The optimal configuration of the three layers should have a uniform distribution with 0.3–0.5 mm wall thickness,a 1:1–2 thickness ratio of epidermis and dermis,and 100–150 compartments.A bionic sole with an optimized structure can reduce the peak impact force and delay the peak arrival time.Its energy absorption rate is about 4 times that of standard sole.When jumping 80,100,and 120 cm,the normalized ground reaction force is also reduced by 8.7%,12.6%and 15.1%compared with standard shoes.This study provides theoretical and technical support for effective protection against human lower limb landing injuries.

型钢-钢纤维混凝土局部组合梁受力性能

为解决型钢混凝土结构的施工困难,充分发挥各部分材料的性能优势,将钢筋笼离散化为随机分布的钢纤维,并将钢纤维混凝土集中应用于受压区,形成型钢-钢纤维混凝土局部组合梁。对18根不同钢纤维体积率(ρ_(sf))、剪跨比(λ)、型钢受压翼缘上下部混凝土保护层厚度(C_(ss)、C_(sv))和型钢规格(I_(s))的组合梁试件进行四点弯试验。分析试验参数对破坏模式、荷载-挠度曲线以及破坏对称性的影响。结果表明:增大ρ_(sf)对小剪跨比试件(λ为1.5或1.7)的界面黏结性能具有积极改善作用,试件破坏模式由界面破坏转为弯扭破坏;混凝土保护层厚度须随I_(s)同步增大,确保混凝土保护层对型钢提供足够的“握裹效应”,避免或削弱弯扭变形的不利影响。通过高斯分布拟合,得到试件整体性能开始出现严重退化时的挠度退化系数,进而对构件整体性能开始出现严重退化时的挠度进行预测。

多目标协同建筑结构消能减震技术研究进展

消能减震技术是提升建筑结构抗震性能的有效手段。随着城乡建设的发展,以“最大层间位移角”作为主要控制目标的传统消能减震技术,逐渐难以满足更综合性、系统性的结构地震安全需求,催生了多目标协同减震技术。该文重点介绍和总结课题组在多目标协同减震技术领域的研究工作,以“结构最大响应与损伤集中协同控制”、“多地震水准响应协同控制”和“结构刚度与耗能能力的协同控制”三种协同减震策略为例,逐一阐述分析协同控制的需求,概括介绍团队提出的协同控制思路和研究进展,并展望多目标协同减震技术未来的发展方向。

Engineering practice of seismic isolation and energy dissipation structures in China

The concepts of seismic isolation and energy dissipation structures emerged in the early 1970s.In China,the first seismic isolation structure was finished in 1993,and the first energy dissipation structure was built at about the same time.Up to 2007,China had more than 600 seismic isolation and about 100 energy dissipation building structures.In 2008,the huge Wenchuan earthquake hit the southwest of China,which triggered a bloom of new seismic isolation and energy dissipation structures.This paper presents the development history and representative applications of seismic isolation and energy dissipation structures in China,reviews the state-of-the-practice of Chinese design,and discusses the challenges in the future applications.Major findings are as follows:Basic design procedures are becoming standardized after more than ten years of experiences,which mainly involve determination of design earthquake forces,selection of ground motions,modeling and time-history analyses,and performance criteria.Nonlinear time-history analyses using multiple ground motions are the characteristic of the design of seismic isolation and energy dissipation structures.Regulations,standardization and quality control of devices,balance between performance and cost,comparison with real responses,and regular inspection are identified as the issues that should be improved to further promote the application of seismic isolation and energy dissipation structures in China.

Recent advances in structural control research and applications in China mainland

The recent developments of theoretical research, model tests and engineering applications of structural control in China's Mainland are reviewed in this paper. It includes seismic isolation, passive energy dissipation, active and semi-active control, smart materials and smart structural systems. It can be seen that passive control methods, such as seismic isolation and energy dissipation methods, have developed into the mature stage in China. At the same time, great progress has been made in active and semi-active control, and smart actuators or smart dampers and smart structural systems. Finally, some future research initiatives for structural control in civil engineering are suggested. Keywords state-of-the-art review - structural control - seismic isolation - passive energy dissipation - active and semi-active control - smart material and smart structure Supported by : National Natural Science Foundation of China (Grant No. 50025821)

合肥新桥国际机场T2航站楼结构设计

新建合肥新桥国际机场T2航站楼采用下部为混凝土结构、顶部屋盖为大跨钢结构的结构形式,结构设计基于建筑特点和场地条件展开。介绍了基于场地表面起伏较大、需进行大面积回填条件下的桩基选型过程和桩基施工流程,详细阐述了基于建筑结构一体化理念的大跨屋盖结构体系及其支承结构的确定过程。根据航站楼的功能特点,通过比选确定主楼采用速度型减震装置的消能减震方案,提高结构的耗能能力并实现良好的抗震性能。通过抗连续倒塌分析和抗火分析确定钢屋盖及其支撑柱的防护方法,对钢管混凝土柱与下部钢筋混凝土柱等截面的连接节点进行了数值分析,最后对屋盖钢桁架的管-管相交节点确定原则进行了介绍。结果表明:该航站楼结构设计可靠,满足各项要求。