Resilient performance of self-centering hybrid rocking walls with curved interface under pseudo-static loading

Frame and rocking wall(FRW)structures have excellent resilient performance during earthquakes.However,the concrete at interfacial corners of rocking walls(RWs)is easily crushed due to local extreme compression during the rocking process.An innovative RW with a curved interface is proposed to prevent interfacial corners from producing local damage,enhancing its earthquake resilient performance(ERP).The precast wall panel with a curved interface is assembled into an integral self-centering hybrid rocking wall(SCRW)by two post-tensioned unbonded prestressed tendons.Moreover,two ordinary energy dissipation steel rebars and two shear reinforcements are arranged to increase the energy dissipation capacity and lateral resistance.Two SCRW specimens and one monolithic reinforced concrete(RC)shear wall(SW)were tested under pseudo-static loading to compare the ERPs of the proposed SCRW and the SW,focusing on studying the effect of the curved interface on the SCRW.The key resilient performance of rocking effects,failure modes,and hysteretic properties of the SCRW were explored.The results show that nonlinear deformations of the SCRW are concentrated along the interface between the SCRW and the foundation,avoiding damage within the SCRW.The restoring force provided by the prestressed tendons can effectively realize self-centering capacity with small residual deformation,and the resilient performance of the SCRW is better than that of monolithic SW.In addition,the curved interface of the SCRW makes the rocking center change and move inward,partially relieving the stress concentration and crush of concrete.The rocking range of the rocking center is about 41.4%of the width of the SCRW.

Mathematical treatment of wave propagation in acoustic waveguides with n curved interfaces

There are some curved interfaces in ocean acoustic waveguides. To compute wave propagation along the range with some marching methods, a flattening of the internal interfaces and a transforming equation are needed. In this paper a local orthogonal coordinate transform and an equation transformation are constructed to flatten interfaces and change the Helmholtz equation as a solvable form. For a waveguide with a flat top, a fiat bottom and n curved interfaces, the coefficients of the transformed Helmholtz equation are given in a closed formulation which can be thought of as an extension of the formal work related to the equation transformation with two curved internal interfaces. In the transformed horizontally stratified waveguide, the one-way reformulation based on the Dirichlet-to-Neumann （DtN） map is then used to reduce the boundary value problem to an initial value problem. Numerical implementation of the resulting operator Riccati equation uses a large range step method to discretize the range variable and a truncated local eigenfunction expansion to approximate the operators. This method is particularly useful for solving long range wave propagation problems in slowly varying waveguides. Furthermore, the method can also be applied to wave propagation problems in acoustic waveguides associated with varied density.

Prediction of curved oil–water interface in horizontal pipes using modified model with dynamic contact angle

In this study,interface shapes of horizontal oil–water two-phase flow are predicted by using Young-Laplace equation model and minimum energy model.Meanwhile,the interface shapes of horizontal oil–water twophase flow in a 20 mm inner diameter pipe are measured by a novel conductance parallel-wire array probe(CPAP).It is found that,for flow conditions with low water holdup,there is a large deviation between the model-predicted interface shape and the experimentally measured one.Since the variation of pipe wetting characteristics in the process of fluid flow can lead to the changes of the contact angle between the fluid and the pipe wall,the models mentioned above are modified by considering dynamic contact angle.The results indicate that the interface shapes predicted by the modified models present a good consistence with the ones measured by CPAP.

Measurement of Liquid Concentration Fields Near Interface with Cocurrent Gas-Liquid Flow Absorption Using Holographic Interferometry

Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by ethanol. The influences of the Reynolds number on the measurable interface concentration and on the film thickness were discussed. The results show that CO2 concentration decreases exponentially along the mass transfer direction,and the concentration gradient increases as Reynolds number of either liquid or gas increases. CO2 concentrations fluctuate slightly along the direction of flow; on the whole, there is an increase in CO2 concentration. The investigation also demonstrated that film thickness decreases with the increase of Reynolds number of either of the two phases. Sherwood number representing the mass transfer coefficient was finally correlated as a function of the hydrodynamic parameters and the physical properties.

Interface Mechanical Behavior of Flexible Piles Under Lateral Loads in OWT Systems

This paper investigates the interface mechanical behavior of flexible piles with L_p/D>10 under lateral load and an overturning moment in monotonic loading conditions.To modify the beam-on-Winkler-foundation model of piles in offshore wind farms,the energy-based variational method is used.The soil is treated as a multi-layered elastic continuum with the assumption of three-dimensional displacements,the pile modeled as an Euler-Bernoulli beam.A series of cases using MATLAB programming was conducted to investigate the simplified equations of initial stiffness.The results indicated that the interaction between soil layers and the applied force position should be taken into account in calculating the horizontal soil resistance.Additionally,the distributed moment had a limiting effect on the lateral capacity of a flexible pile.Moreover,to account for the more realistic conditions of OWT systems,field data from the Donghai Bridge offshore wind farm were used.

Growth and aggregation micromorphology of natural gas hydrate particles near gas-liquid interface under stirring condition

To investigate the morphological evolution of the whole growth and aggregation processes of hydrate crystals near the gas–liquid interface,we used a high-pressure visual reactor with high-speed camera to capture the micromorphology of hydrate particles in a natural gas+pure water system with pressure from 2.6 to 3.6 MPa and sub-cooling from 4.7 to 6.23C.The results showed that under low sub-cooling conditions,the amount and size of particles increased first and then decreased in the range of 0–330 lm,and the small particles always dominated.These particles can be roughly classified into two categories:planar flake particles and polyhedral solid particles.Then,the concept of maximum growth dominant particle size was proposed to distinguish the morphological boundary of growth and aggregation.In addition,the micro model was established to better reflect the effects of particle formation process and evolution mechanism near the gas–liquid interface under stirring condition.The results of this study can provide a guidance for flow assurance in multiphase pipeline.

Measurement of Liquid Concentration Fields Near Interface with Cocurrent Gas-Liquid Flow Absorption Using Holographic Interferometry

Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by ethanol. The influences of the Reynolds number on the measurable interface concentration and on the film thickness were discussed. The results show that CO2 concentration decreases exponentially along the mass transfer direction, and the concentration gradient increases as Reynolds number of either liquid or gas increases. CO2 concentrations fluctuate slightly along the direction of flow; on the whole, there is an increase in CO2 concentration. The investiga- tion also demonstrated that film thickness decreases with the increase of Reynolds number of either of the two phases. Sherwood number representing the mass transfer coefficient was finally correlated as a function of the hy- drodynamic parameters and the physical properties.

A second order isoparametric finite element method for elliptic interface problems

A second order isoparametric finite element method （IPFEM） is proposed for elliptic interface problems. It yields better accuracy than some existing second-order methods, when the coefficients or the flux across the immersed curved interface is discontinuous. Based on an initial Cartesian mesh, a mesh optimization strategy is presented by employing curved boundary elements at the interface, and an incomplete quadratic finite element space is constructed on the optimized mesh. It turns out that the number of curved boundary elements is far less than that of the straight one, and the total degree of freedom is almost the same as the uniform Cartesian mesh. Numerical examples with simple and complicated geometrical interfaces demonstrate the efficiency of the proposed method.

Adsorption structures of frothers at gas–liquid interface using DFT method

Density functional theory (DFT) simulation was performed to investigate the adsorption mechanisms between frothers and gas–liquid interface. In water phase, the polar head group of the frother molecule was connected with water molecules by hydrogen bonding, while the non-polar group showed that hydrophobic property and water molecules around it were repelled away. The adsorption of water molecules on single frother molecule suggests that the complexes of α-terpineol-7H2O, MIBC-7H2O and DF200-13H2O reach their stable structure. The hydration shell affects both the polar head group and the non-polar group. The liquid film drainage rate of DF200 is the lowest, while α-terpineol and MIBC are almost the same. The adsorption layer of frother molecules adsorbed at the gas-liquid interface reveals that the α-terpineol molecules are more neatly arranged and better distributed. The DF200 molecules are arranged much more loosely than MIBC molecules. These results suggest that the α-terpineol molecule layer could better block the diffusion of gas through the liquid film than DF200 and MIBC. The simulation results indicate that the foam stability of α-terpineol is the best, followed by DF200 and MIBC.

Adaptive neuro-fuzzy interface system for gap acceptance behavior of right-turning vehicles at partially controlled T-intersections

Gap acceptance theory is broadly used for evaluating unsignalized intersections in developed coun tries. Intersections with no specific priority to any move ment, known as uncontrolled intersections, are common in India. Limited priority is observed at a few intersections, where priorities are perceived by drivers based on geom etry, traffic volume, and speed on the approaches of intersection. Analyzing such intersections is complex because the overall traffic behavior is the result of drivers, vehicles, and traffic flow characteristics. Fuzzy theory has been widely used to analyze similar situations. This paper describes the application of adaptive neurofuzzy interface system （ANFIS） to the modeling of gap acceptance behavior of rightturning vehicles at limited priority Tintersections （in India, vehicles are driven on the left side of a road）. Field data are collected using video cameras at four Tintersections having limited priority. The data extracted include gap/lag, subject vehicle type, conflicting vehicle type, and driver＇s decision （accepted/rejected）. ANFIS models are developed by using 80 % of the extracted data （total data observations for major road right turning vehicles are 722 and 1,066 for minor road right turning vehicles） and remaining are used for model vali dation. Four different combinations of input variables are considered for major and minor road right turnings sepa rately. Correct prediction by ANFIS models ranges from 75.17 % to 82.16 % for major road right turning and 87.20 % to 88.62 % for minor road right turning. Themodels developed in this paper can be used in the dynamic estimation of gap acceptance in traffic simulation models.

Change of the mode of failure by interface friction and width-to-height ratio of coal specimens

Bumps in coal mines have been recognized as a major hazard for many years. These sudden and violent failures around mine openings have compromised safety, ventilation and access to mine workings.Previous studies showed that the violence of coal specimen failure depends on both the interface friction and width-to-height（W/H） ratio of coal specimen. The mode of failure for a uniaxially loaded coal specimen or a coal pillar is a combination of both shear failure along the interface and compressive failure in the coal. The shear failure along the interface triggered the compressive failure in coal. The compressive failure of a coal specimen or a coal pillar can be controlled by changing its W/H ratio. As the W/H ratio increases, the ultimate strength increases. Hence, with a proper combination of interface friction and the W/H ratio of pillar or coal specimen, the mode of failure will change from sudden violent failure which is brittle failure to non-violent failure which is ductile failure. The main objective of this paper is to determine at what W/H ratio and interface friction the mode of failure changes from violent to non-violent. In this research, coal specimens of W/H ratio ranging from 1 to 10 were uniaxially tested under two interface frictions of 0.1 and 0.25, and the results are presented and discussed.

Experimental study on the shear behavior of the interface between cushion materials and the concrete raft

Cushion is a layer of granular materials between the raft and the ground. The shear behavior of the interface between the cushion and the raft may influence the seismic performance of the superstructure. In order to quantify such influences, horizontal shear tests on the interfaces between different cushion materials and concrete raft under monotonic and cyclic loading were carried out. The vertical pressure P_v, material type and cushion thickness h_c were taken as variables. Conclusions include： 1） under monotonic loading, P_v is the most significant factor; the shear resistance P_（hmax） increases as P_v increases, but the normalized factor of resistance μ_n has an opposite tendency; 2） for the materials used in this study, μ_n varies from 0.40 to 0.70, the interface friction angle δ_s varies from 20° to 35°, while u_（max） varies from 3 mm to 15 mm; 3） under cyclic loading, the interface behavior can be abstracted as a ＂three-segment＂ back-bone curve, the main parameters include μ_n, the displacement u_1 and stiffness K_1 of the elastic stage, the displacement u_2 and stiffness K_2 of the plastic stage; 4） by observation and statistical analysis, the significance of different factors, together with values of K_1, K_2 and μ_n have been obtained.

拉压段长度变化对复合锚杆锚固性能影响研究

抗浮是深基坑施工所面临的重要工程问题之一,目前多使用抗浮锚杆平衡地下水对构筑物产生的浮力。但拉力锚杆具有局部应力集中、临界锚固深度浅等问题。因此研究设计了一种新型拉压分散型复合锚杆。通过现场试验,分析复合锚杆拉压段长度变化与锚杆锚固性能相关关系,并与拉力锚杆进行对比。结果表明:复合锚杆可以有效防止锚杆第一界面发生剪切破坏;随着承拉段与承压段长度比值降低(比值分别为5、2、1),锚杆极限承载力逐渐提高,分别为传统拉力型锚杆的1.17倍、1.22倍和1.44倍,且荷载位移曲线陡降性逐渐消失,结构延性更好;一定范围内增加承压段长度,可以更有效地调用锚固段下部土层强度,锚杆临界锚固深度下移,侧摩阻力发挥程度更高。

含聚合物防水膜的隧道衬砌界面剪切-滑移力学特性试验研究

为研究隧道衬砌结构中密贴型防水层界面的力学特性,根据隧道喷膜防水衬砌结构的特点,采用粘结强度试验和压剪试验探讨聚合物防水膜复合试件的界面剪切-滑移力学行为和特性。通过粘结强度试验绘制3种类型防水膜的拉伸应力-位移曲线,通过压剪试验绘制界面剪切应力-位移曲线,基于试验结果曲线计算得到防水层的界面参数,包括剪切强度、残余剪切强度、剪切模量、剪切滑移能量和剪切失效位移,并讨论防水材料性能和法向压应力对这些参数的影响。结果表明,防水层界面的剪切-滑移特性主要受防水材料特性和法向压应力的影响,防水材料特性对界面剪切强度和剪切模量的影响较大,而残余剪切强度、剪切滑移能量和剪切失效位移则受到法向压应力的影响更多。

Bond behavior of the interface between concrete and basalt fiber reinforced polymer bar after freeze–thaw cycles

The shear bond of interface between concrete and basalt fiber reinforced polymer(BFRP)bars during freeze–thaw(F–T)cycles is crucial for the application of BFRP bar-reinforced concrete structures in cold regions.In this study,48 groups of pull-out specimens were designed to test the shear bond of the BFRP-concrete interface subjected to F–T cycles.The effects of concrete strength,diameter,and embedment length of BFRP rebar were investigated under numerous F–T cycles.Test results showed that a larger diameter or longer embedment length of BFRP rebar resulted in lower interfacial shear bond behavior,such as interfacial bond strength,initial stiffness,and energy absorption,after the interface goes through F–T cycles.However,higher concrete strength and fewer F–T cycles were beneficial for enhancing the interfacial bond behavior.Subsequently,a three-dimensional(3D)interfacial model based on the finite element method was developed,and the interfacial bond behavior of the specimens was analyzed in-depth.Finally,a degradation bond strength subjected to F–T cycles was predicted by a proposed mechanical model.The predictions were fully consistent with the tested results.The model demonstrated accuracy in describing the shear bond behavior of the interface under numerous F–T cycles.

GFRP-轻木断芯梁界面剥离静力及疲劳试验

以工程适用的玻璃纤维增强复合材料(GFRP)-轻木夹芯结构为研究对象,设计了含界面和芯材裂纹的“断芯梁”试件;通过三点弯静力及疲劳试验研究了GFRP-轻木夹芯结构界面剥离破坏的规律,获得了不同跨高比、应力比及荷载等级下试件的a-N曲线,分析了不同参数对界面疲劳剥离破坏的影响;基于帕里斯理论建立了疲劳裂纹扩展速率模型。结果表明:所设计的断芯梁试件能够获得稳定的界面裂纹扩展;疲劳试验中,界面剥离破坏出现明显的“三阶段”特征,疲劳裂纹剥离速率分别随应力比减小、荷载等级增大呈现增加趋势;以应变能释放率变程为控制参量的疲劳裂纹扩展速率模型可较好地描述界面剥离过程。

微动技术在登科地区深部找矿中的应用效果研究

为开拓深部找矿新方法,特引入地球物理探测新技术-微动,并探索分析其应用效果。首先介绍微动探测方法原理和数据采集与处理,其次在CSAMT推测的建议钻孔位置开展微动勘探工作,分析单点频散曲线特征,识别深部地层界面;最后根据钻孔验证结果,综合对比CSAMT和微动勘探在深部重点地层界面识别效果。结果显示,微动勘探识别深部层界面效果明显,CSAMT联合微动技术可以提高物探解译的精准度。

The Mechanism of Interfacial Mass Transfer in Gas Absorption Process

Based on the method of molecular thermodynamics, the mass transfer mechanism at gas-liquid interface is studied theoretically, and a new mathematical model is proposed. Using laser holographic interference technique, the hydrodynamics and mass transfer characteristics of CO2 absorption are measured. It is shown that the calculated results are in good agreement with the experimental data.

An analytical p-y curve method based on compressive soil pressure model in sand soil

With the high-quality development of urban buildings,higher requirements are come up with for lateral bearing capacity of laterally loaded piles.Consequently,a more accurate analysis to predict the lateral response of the pile within an allowable displacement is an important issue.However,the current p-y curve methods cannot fully take into account the pile-soil interaction,which will lead to a large calculation difference.In this paper,a new analytical p-y curve is established and a finite difference method for determining the lateral response of pile is proposed,which can consider the separation effect of pile-soil interface and the coefficient of circumferential friction resistance.In particular,an analytical expression is developed to determine the compressive soil pressure by dividing the compressive soil pressure into two parts:initial compressive soil pressure and increment of compressive soil pressure.In addition,the relationship between compressive soil pressure and horizontal displacement of the pile is established based on the reasonable assumption.The correctness of the proposed method is verified through four examples.Based on the verified method,a parametric analysis is also conducted to investigate the influences of factors on lateral response of the pile,including internal friction angle,pile length and elastic modulus of pile.

水力压裂煤体相位频谱曲线试验研究

为探明水力压裂前后煤体内部结构改变引起的复电阻率变化规律,在实验室开展加载围压下煤体水力压裂试验,测量压裂前后煤体相位和振幅频谱曲线。结果表明:(1)压裂前后干燥煤体相位频谱曲线均为“U”型,压裂后相位频谱曲线移动明显;(2)含蒸馏水的压裂煤体相位频谱曲线呈“W”型;(3)压裂煤体中,“W”型曲线是由于未充分填充的含水次生裂隙和原有裂隙的不充分界面极化共同所致,这与水力压裂对煤体破坏的不均匀性有关;(4)采用等效电路的方法,用不同电容器代替煤体不同频率界面极化,模拟相位频谱曲线从“W”型变为“U”型的过程发现,未充分填充的含水次生裂隙和原生裂隙在不同频率下的不充分界面极化是产生“W”型曲线的原因。