浙江大学5 Hz空心圆柱仪试样固结变形研究

 目前,国际上研究主应力轴旋转对土体性状影响的较理想仪器主要是空心圆柱仪,浙江大学岩土工程研究所与英国GDS仪器设备有限公司共同研发的5 Hz空心圆柱仪,可进行静态试验及中高频率下轴力、扭矩共同变载试验。准确测定空心圆柱试样的变形是后续应力控制试验的前提及应变测量的基准,而试样在等压固结以后,由于装样操作及气泡的影响很难直接精确地测量。通过对试样内压腔体变、反压腔体变及轴向应变的分析,利用迭代法,推导空心圆柱试样等压固结后内外径计算公式,修正Tastuoka关于试样内外径变化的假设,并与局部传感器实测值进行对比,说明由体变和轴向位移变化计算外径的方法是可行的,用修正后的内径计算结果重新进行试验可以大大提高试验的测试精度和应力控制的可靠性。     

三维激光扫描灰度信息在结构变形场计算中的应用

非接触测量技术是结构测量领域的最新进展之一，这类测量方法无需在被测对象上安装传感器，因而在结构试验以及土木工程现场实测中具有一定的优势。三维激光扫描作为一种非接触测量新技术，可以直接获取目标物表面点密集的三维坐标和灰度值，受测试环境干扰小，因而在土木工程领域的应用日益受到关注。在激光扫描技术的基础上，提出一种同名点的匹配方法，以提高变形场计算的精度。这种方法利用激光扫描的灰度信息，对扫描得到的点云坐标和灰度数据进行像素化处理，然后用相关系数法确定同名点并计算位移场。通过一钢梁试验对该方法进行验证，将结果与导杆位移计以及有限元分析的结果作了比对，结果显示该方法可以提高同名点识别的精度，进而提高结构变形计算的准确性，且可以同时获得构件包括平面内和平面外的变形。     

A wireless structural monitoring system with embedded damage algorithms and decision support system

A wireless structural monitoring system was designed and built to accommodate multiple sensors and provide alerts through a decision support system. In this paper we describe the main features of the system and present the results of its application to a laboratory test. The test was a quarter scale four-span three-pier bridge subjected to gradually increasing earthquake motion with white noise excitations between the strong motions conducted at the University of Nevada, Reno. Autoregressive (AR) models were used to characterise the signals collected from the test and damage was identified through Gaussian mixture models. Damage was quantified using the Mahalanobis distance between undamaged and various damage states of the bridge. The experiment provided a proof of concept for the wireless system and its multitude of features. The analysis of the data demonstrated that the algorithm is capable of identifying the progression of damage and showed good agreement between the measured and observed damage states.     

高轴压比下加芯混凝土框架柱延性与承载力试验研究

通过高轴压比下8个加芯混凝土框架柱和1个普通混凝土框架柱低周往复加载的模型试验,阐述了主要试验现象及破坏形态,对各试件的P-Δ滞回曲线、位移延性系数、极限位移转角、屈服荷载和极限荷载等试验结果进行了研究,分析了加芯混凝土框架柱延性和承载力的影响因素。结果表明:通过对芯柱进行合理设置,加芯混凝土框架柱具有良好的滞回延性和较高的抗震承载力,可明显改善普通混凝土框架柱在高轴压比下的抗震性能,弹塑性变形能力能够满足抗震要求;芯柱的纵筋配筋率、截面面积和体积配箍率是影响加芯混凝土框架柱延性和承载力的主要因素。结合以往的研究成果,本文提出了加芯混凝土框架柱轴压比限值的建议值、正截面承载力计算公式以及相关设计建议。     

Pavement performance assessment using a cost‐effective wireless accelerometer system

Pavement condition monitoring is required to identify pavements in need of maintenance or rehabilitation. Early identification of reduction in pavement's structural resistance and improving the structural resistance by minor repairs can lead to significantly lower maintenance costs for transportation agencies. In this study, a cost‐effective wireless sensor that can be embedded in the road to measure the transient vibrations due to different applied loads was tested to determine its effectiveness in terms of pavement displacement measurements. Test results show that the vibration sensor, combined with the algorithms, can be embedded in new or existing pavements and used as an accurate wireless displacement sensor. The low cost of the sensor system allows the use of these sensors at high densities for monitoring the performance of an entire road network. Outputs from the developed system can be directly used to evaluate the condition and performance of pavement structure (increasing displacement over time indicating increasing pavement damage). In addition, displacement data from the system can be used to backcalculate pavement layer stiffnesses, which can be used to predict long‐term performance of the pavement structure. Reduction in pavement layer stiffness over time can be used to determine long‐term damage accumulation.     

基于传感器网络的桥梁健康监测系统的研究与设计

本文主要通过传感器网络技术,将温度传感器、应变传感器、位移传感器等与动态称重系统进行系统集成,完成了对桥梁结构的安全监测,及时发现桥梁损伤,为桥梁维护管理提供技术依据,辅助桥梁日常交通管理,确保了桥梁的安全运营。本文主要对系统的整体架构、传感器网络系统、数据采集系统及软件系统的设计进行详尽的阐述。本文的论述,给桥梁工程领域提供了很好的健康监测应用案例,对从事该领域的工程技术人员具有重要的参考意义。     

约束钢柱抗火性能试验研究

介绍了一组约束钢柱抗火试验,包括试验设计、钢柱温度和位移测量结果、钢柱试验后残余变形,以及试验的数值模拟等。试验变化参数为钢柱所受约束的刚度。约束刚度大小对钢柱抗火性能的影响包括:约束刚度比大的钢柱,其屈曲温度和破坏温度均较低;钢柱屈曲后,约束刚度比大的钢柱在变形较小时即可达到新的平衡位置;约束钢柱的破坏温度一般高于其屈曲温度,且随轴向约束刚度比的增大,破坏温度与屈曲温度之差增大。试验结果与有限元分析结果进行了对比,两者吻合较好,有限元方法研究约束钢柱抗火性能具有较高的精度。     

Performance comparison of occupancy count estimation and prediction with common versus dedicated sensors for building model predictive control

Model predictive control is a promising approach to optimize the operation of building systems and provide demand-response functionalities without compromising indoor comfort. The performance of model predictive control relies, among other things, on the quality of weather forecasts and building occupancy predictions. The present study compares the accuracy and computational demand of two occupancy estimation and prediction approaches suitable for building model predictive control: (1) count prediction based on indoor climate modeling and parameter estimation “using common sensors”, (2) count prediction based on data from 3D stereovision camera. The performance of the two approaches was tested in two rooms of a case study building. The results show that the method with dedicated sensors outperforms common sensors. However, if a building is not equipped with dedicated sensors, the present study shows that the common sensor method can be a satisfactory alternative to be used in model predictive control.     

主动式火灾光电探测信号基线漂移滤除和去噪方法研究

针对数据中心机柜的主动式火灾光电探测报警系统降低误报率和提高检测精度的需求,设计极早期火灾探测腔体结构,完成光电检测数字电路硬件,采集光电信号,分别采用集合经验模态分解（EEMD）算法和小波分析算法来滤除低频基线漂移和降低背景白噪声。经过对比计算处理后信号的相关性和信噪比,结果表明,在本文所述数据采集密度下,EEMD 方法的性能明显优于小波分析方法,可有效地降低误报率和提高检测精度,实现对火灾的“极早期”探测和预警。     

Feasibility study of applying SOFO optical fiber sensor to segment of shield tunnel

The feasibility of applying SOFO optical fiber sensor to the segment of shield tunnel is presented in this paper. A concrete beam with two optical fiber sensors is used to simulate the future application in segment of shield tunnel. The concrete deformed behavior during the curing process of steam and water is monitored. After the curing process is completed, a pair of optical fiber sensors are installed on the beam surface at the same distance away from neutral axis the same as the embedded optical fiber sensors. Then the cyclic two points load testing is conducted and two LVDT are used to monitor deflections at two sections. The deformation of surface sensor is smaller than the embedded sensor which can be shown the actual deformation of concrete beam. The theoretical contraction of sensor is very close to the embedded sensor, however, the difference between theoretical extension and sensor measurement is gradually enlarged with loading level. This reflects that the neutral axis moves upwards when concrete tensile stress exceeds strength. The results of LVDT cannot be used as a basis to evaluate the results from optical fiber sensors. According to experimental results, SOFO optical fiber sensor not only can survive in the harsh curing process, and but also can reliably monitor the concrete deformation. The accuracy of strain measurement by SOFO optical fiber sensor is also verified in two points load testing. Besides, the appropriate location at which the optical fiber sensor can be embedded in the segment is evaluated. The finite element method is used to analyze the shield tunnel in the soft clay, hard clay, loose sand as well as dense sand. The bending, hoop and shear stress distributions are evaluated for each soil condition. Based on the length of sensor and the results of numerical analyses, the best location for sensor is at the spline of segment, because the gradient of bending stress at spline is minimum. The application of SOFO optical fiber sensor in shield tunnel for long-term warning system is promising and is adopted in a shield tunneling project now.     

Protecting a whole building from critical indoor contamination with optimal sensor network design and source identification methods

To maintain a healthful and secure indoor environment, it is crucial to design an effective indoor air quality (IAQ) sensor network and interpret sensor outputs for prompt IAQ controls. This paper introduces how a probability concept based inverse modeling method – the adjoint probability method – can be used to assist in designing a high-performance IAQ sensor network and identifying potential contaminant source locations for an entire building based on limited sensor outputs. The study proposes a new IAQ sensor network design and optimization method for buildings with one or more compartments on the basis of the probability calculation. With responses from optimized sensors, a two-stage integrated inverse prediction algorithm is developed that is able to identify a potential IAQ source zone (or room) in a building as well as an exact location within the room. The paper demonstrates the design of sensor networks and the application of the source identification algorithms for a residential dwelling. The case study verifies the feasibility, effectiveness and accuracy of the proposed sensor design method and the two-stage algorithm for indoor contaminant control.     

Prediction for lateral deformation capacity of corroded reinforced concrete columns

The deformation capacities of columns, which are the main lateral force‐resisting elements of reinforced concrete (RC) structures, have been the subject of great interest with the development of performance/displacement‐based seismic design. However, deterioration due to chloride‐induced corrosion causes a significant reduction in the seismic performance of RC columns. Although numerous investigations have focused on the deformation capacity of columns with corroded rebars and various strengthening measures have been proposed, little attention was paid to evaluating the contribution of each deformation component to the tip displacement under corrosion (i.e., bending, shear, and longitudinal bar slip at the column footing), which plays an important role in investigating and explaining the failure mechanisms of columns. This paper presents a computational prediction model to estimate the deformation capacity of RC columns with corroded rebars, and the contributions of bending and bar slip at the column footing are mainly considered in this model due to the negligible contribution of the shear deformation component for columns subjected to flexural failure mode. The calculation results obtained by the prediction model are compared with the quasistatic test results of both noncorroded and corroded RC columns. It turns out that the prediction model simulates the deformation capacity of RC columns with corroded rebars reasonably well considering its simplicity and computational efficiency, and it can be used for time‐variant capacity estimates for the lifetime seismic design and fragility assessment of RC columns exposed to corrosion.     

Development of a Cost‐Effective Wireless Vibration Weigh‐In‐Motion System to Estimate Axle Weights of Trucks

Truck weight data plays an important role in weight enforcement and pavement condition assessment. This data is primarily obtained through weigh stations and Weigh‐In‐Motion (WIM) stations which are currently very expensive to install and maintain. This article presents results of the implementation of an inexpensive wireless sensor‐based vibration WIM system. The proposed wireless sensor network (WSN) consists of acceleration sensors that report pavement vibration; vehicle detection sensors that report a vehicle's arrival and departure times; and an access point (AP) that synchronizes all the sensors and records the sensor data. The article also describes a new method for speed compensation, an energy‐efficient algorithm (adaptive sampling method) to increase battery life, and a new modeling procedure to estimate gross vehicle weights. The system deployed near a conventional WIM system on I‐80W in Pinole, CA passed the accuracy standards for WIM systems and outperformed a nearby commercial WIM station, based on conventional technology.     

考虑动力损伤退化的钢筋混凝土柱恢复力模型

基于16根钢筋混凝土柱的静力和动力循环往复加载试验,研究了动力效应对柱抗震性能的影响。依据修正Park-Ang损伤指标建立的静力和动力损伤指标,能够兼顾考虑最大位移与循环加载次数对柱损伤退化指标的影响。分别建立静力和动力加载下性能退化参数与相应位移比、损伤指标之间的关系,并结合建构的动力退化函数,提出能够反映滞回曲线的负刚度段、循环退化效应以及捏缩效应的钢筋混凝土柱动力恢复力模型。与试验数据对比的结果表明,提出的宏观力学模型可以有效模拟静力和动力加载情况下钢筋混凝土柱的滞回特性,且动力恢复力模型相比于静力恢复力模型能够更好地刻画钢筋混凝土柱在地震应变率作用下的力学性能。文中建立的恢复力模型及方法可为钢筋混凝土结构的抗震分析提供理论参考。     

基于粒子群算法的岩体微震源分层定位方法

 针对微震经典定位法速度模型给不准和联合定位法震源位置、发震时间和微震传播速度相互关联,解不唯一的问题,提出一种微震源定位分层处理方法,先对微震信号进行消噪、分波、到时修正和劣质信号剔除等一系列处理,初步获取正确的有效信号;然后以相邻两传感器监测到时之差与计算到时之差的残差平方和最小为目标,利用粒子群算法,识别微震源位置和速度模型;接着,根据识别到的微震源位置和速度模型,以传感器监测到时和计算到时的残差平方和最小为目标,直接求解微震源发震时间的解析解;最后,再次结合矿山实际开采现状反分析有效微震信号选取的正确性和微震源定位的准确性,必要时再次对微震信号进行处理和定位,较好地解决经典法速度模型给不准和联合法解不唯一的问题。与经典法相比提高了微震定位精度,与联合法相比提高收敛速度和解的稳定性;关联性分析表明某些震源坐标在使用分层法定位时和速度具有一定的关联性,并给出震源坐标和速度相互关联的必要条件和相互关联的几个特殊位置;算法性能分析表明为了进一步提高算法的收敛速度、定位精度和解的稳定性,传感器布置要尽量：(1) 使重点关注的区域位于传感器阵列之内,且距离传感器尽量近,(2) 避免可能发生微震的震源处于能使震源坐标和速度相互关联的位置上。现场爆破试验进一步验证微震源分层定位方法的可行性;最后讨论几种速度模型的选取,分析几种速度模型的优劣及工程应用的可能性。     

数据融合算法在苏通大桥群桩基础 安全性评价中的应用

 位于潮汐河段的苏通大桥采用大直径、超长钻孔灌注群桩基础,而且需要考虑钢护筒的共同作用。为此采用广角度监测技术,跟踪观测钢护筒、桩身钢筋和混凝土的应力响应。但不同类型和处于不同部位的传感器,由于工作原理、精度、安装埋设方式以及影响因素的不同,而导致实测数据的类型和特性存在较大差异。故需采用多传感器信息融合技术,以过滤异常测值、提取特征信息、形成融合决策。但原型观测数据包含有强烈的、来源于潮汐等环境因素产生的噪声,从而严重干扰对数据的分析和预测。而且这类噪声使观测数据产生异常过程和异常群,很难利用冗余信息和数据的时空对比进行检出。故需在采用数据融合理论检出并剔除粗差的基础上,进一步采用小波阈值消噪法分层剥离单个传感器的环境噪声,并根据不同类型传感器观测结果的可信度和重要性,利用基于权最优分配原则的数据融合算法,对消噪后的多个传感器实测数据进行融合。研究结果表明,小波分层消噪技术能够有效分离不同的环境噪声,数据融合技术能够较好地将各传感器的观测数据协调地组合起来,形成对群桩基础应力响应和环境实况更可靠地判断。     

建筑施工中的传感器应用与发展

传感器是信息化施工中实现信息自动采集与录入的基础 ,为项目决策和控制提供基础数据。文章总结了温度、位移、光、压力、光纤和视觉传感器等技术在工程施工中的应用 ,形成了建筑施工传感器系统 ,并论述了其发展。     

钢管高性能混凝土柱抗震性能试验研究

对 4个钢管高性能混凝土柱和 2个钢筋高性能混凝土柱进行了抗震试验。试验发现 ,钢管径厚比和支座约束等是钢管高性能混凝土柱抗震性能的主要影响因素 ,特别是对钢管高性能混凝土柱的滞回特性、位移延性和极限相对位移的影响明显 ;钢管内埋并配置一定数量的抗剪钢筋是一种有效的支座嵌固 ;在柱截面尺寸及用钢量相同的条件下 ,钢管高性能混凝土柱的抗震性能比钢筋高性能混凝土柱好得多     

Multi‐objective Optimization of Sensor and Excitation Layouts for Frequency Response Function‐Based Structural Damage Identification

Abstract: The accuracy of many damage identification methods depends significantly on the quality of measurements collected by sensors, such as accelerometers, concerning the response characteristics of a structure. Often the number of sensors used to collect measurements is limited due to available funds, equipment, and access. In addition, the excitation location can significantly affect a sensor's ability to collect quality measurement information. Therefore, both the location and number of sensors and the location of the excitation must be optimized to maximize the quality of information collected. A multi‐objective optimization approach is presented that minimizes the number of sensors specified while maximizing the sensitivity of the frequency response functions (FRFs) collected at each specified sensor location with respect to all possible damaged structural elements. The multiple Pareto‐optimal sensor/excitation layouts obtained aid in determining the number of sensors required to obtain an effective level of measurement information. The benefit of using Pareto‐optimal sensor/excitation layouts is investigated by using the optimized layouts to collect measurement information for a FRF‐based structural damage identification method. Trial results confirm that an increase in damage identification accuracy and efficiency is achieved when Pareto‐optimal sensor/excitation layouts are used instead of nonoptimal layouts. In addition, the Pareto‐optimal layouts improved damage identification accuracy in noisy measurement environments due to increasing the quality of measurements collected.     

考虑柱间相互作用的阶形柱计算长度系数

柱间相互作用对阶形柱的稳定性有很大的影响,而我国现行规范及已有文献所给出的阶形柱计算长度系数的计算方法不能准确考虑该作用。利用等截面压杆的转角 位移方程得到阶形柱的刚度矩阵,由此推导了轴力对阶形柱刚度削弱的表达式,并构建了可考虑柱间相互作用的阶形柱计算长度系数的计算式。研究表明该计算长度系数计算式具有较高的精度,使用方便,可用于多跨框架的计算,同时也适用于柱高不等的情况。对钢梁起坡的山形门式刚架,给出了实用的计算方法,参数分析表明采用该方法计算得到的柱计算长度系数具有良好的精度,可满足设计需要。