波浪载荷模型试验开口测量梁设计

为了模拟大开口船舶的剖面特性,以集装箱船为例,根据相似理论设计可以同时满足垂向、水平,以及扭转惯量和剪心与实船相似,并且满足首阶固有频率相似的开口测量梁模型,采用相应的应力分析方法进行相应载荷的分离,数值仿真表明所提出的测量梁设计合理。

杆式天平轴向力元件测量梁夹角优化分析

针对天平轴向力受法向力干扰较大的问题,提出了一种竖直梁轴向力元件的改进结构。通过理论分析和有限元仿真,获得了轴向力/法向力作用下的轴向力元件变形情况;对结构进行受力分析,得到法向力作用下的轴向力测量梁的变形特点及变形原因。提出了一种改进的轴向力元件测量梁结构,测量梁与主梁的连接夹角为不等于90°的优化夹角,该夹角通过仿真结果中的法向力对轴向力的干扰输出与轴向力有效输出之比和该夹角的线性函数关系获得。对改进的天平轴向力元件的有限元仿真结果表明:与传统轴向力元件相比,改进结构的轴向力有效输出仅减小2.77%,但法向力对轴向力的干扰输出减小了99.32%。改进的轴向力元件具有良好的抗法向力干扰的效果,适用于具有大升阻比特性的飞行器风洞模型气动力试验要求。

公路桥梁工程测量技术与测绘技术的应用解析

时代在进步,社会在发展,公路桥梁工程测量技术与测绘技术也有了很大的发展,很大程度上提高了工程勘测整体水准。测量技术与测绘技术作为新兴的勘测技术,快速普及到了建筑领域中的各项工程当中,其中就包括对勘测技术要求较高的公路桥梁工程。文章对公路桥梁工程测量技术与测绘技术进行了简单概述,对公路桥梁工程测量工作与测绘工作现存的问题进行了分析,对公路桥梁工程测量技术与测绘技术的应用进行了解析。

研究跨坐式单轨交通轨道梁定位测量及线形检测方法

本文针对跨坐式单轨交通轨道梁,在明确其定位测量与线形检测重要性的基础上,提出具体的测量与检测方法,旨在为实际的定位测量和线形检测工作提供参考依据,保证最终的测量及检测结果精度,为列车的高速、平稳运行奠定良好的基础。

PFWD与贝克曼梁测量数据相关性分析

对PFWD与贝克曼梁测量数据相关性分析。

集装箱船扭矩及剪力模型试验测量方法

为了更加精确地开展集装箱船模型波浪载荷试验,本文设计了能够真实模拟集装箱船垂向、水平、扭转刚度及剪心的U型测量梁,通过测量船体模型分段处U型测量梁横剖面各个板的剪流得到船体所受到的扭矩、垂向剪力和水平剪力。本文对试验原理进行了详细的理论推导,给出了具体的应变片粘贴方法,对超大型集装箱船的U型测量梁进行了有限元计算和试验标定,验证了试验原理及测量方法的合理性和适用性。

斜拉桥塔梁同步施工测量高塔垂直度控制的数学模型探讨

本文以金桥大道斜拉桥为例,阐述了斜拉桥塔梁同步施工的高塔垂直度的测量控制,主要对其数学模型进行了分析选取和应用,使现场测量工作在准确的条件下更便捷有效。

全站仪在杭州湾跨海大桥箱梁桩基定位中的应用

杭州湾跨海大桥位于杭州湾中部,是目前世界第一跨海长桥。本文介绍了杭州湾跨海大桥控制测量技术,讨论了在近海区利用全站仪对常规打桩船打桩的测量技术和在离海岸较远时利用GPS打桩系统打桩的方法。实践表明,该测量技术对海上架桥打桩工作具有一定的理论和实践指导意义。

浅谈太原北中环桥钢箱梁线性控制技术

作者对太原北中环主桥钢箱梁线性控制进行了研究,太原北中环主桥上部结构为钢箱梁。主桥310米,跨径布置为65+45+90+45+65m。北中环桥采用五跨反对称五拱反对称索面斜拉桥,梁体采用等截面钢箱形式。文章通过简要介绍钢箱梁施工测量方法,重点研究了现场安装线性的控制技术。可为同类型的钢箱梁施工工程提供宝贵经验和技术参考。

首都博物馆新馆工程现浇混凝土椭圆斜筒测量

介绍了现浇混凝土椭圆斜筒的概况，以及测量定位放线所用到的方程，探讨了首都博物馆新馆工程现浇混凝土椭圆斜筒的测量方法，从而使工程质量得到控制。

Train-induced vibration on elevated railway station

Results of in-situ vibration measurement carried out at Tianjin West Elevated Railway Station which has the trains running on the station structure were reported. The main excitation source is the train passing through the station. Vibration measurements were recorded in the vertical direction of the supporting track beam, the platform and the steel truss beam of the waiting hall, as well as in the vertical, longitudinal and transverse directions of the roof arch base of the station. Acceleration time responses were obtained. The maximum value, vibration level and one-third octave band RMS spectra of the measured accelerations were studied. The propagation of vibration in different structural floors was discussed. The influence of train speed, distance to the vibration source and the type of train on the structural vibration were analyzed. Results show that the vibration level increases with the train speed, while it attenuates with the distance to the track. Furthermore, the vibration responses of different structural floors were compared, and it is noted that the vertical vibration of the bottom slab of the platform is most severe and the transverse vibration of the roof arch base is the smallest. The results provide reference on the vibration characteristics and vibration energy distribution of this type of "Train on building frame" system used as an elevated railway station.

Estimating extreme temperature differences in steel box girder using long-term measurement data

The extreme temperature differences in fiat steel box girder of a cable-stayed bridge were studied.Firstly,by using the long-term measurement data collected by the structural health monitoring system installed on the Runyang Cable-stayed Bridge,the daily variations as well as seasonal ones of measured temperature differences in the box girder cross-section area were summarized.The probability distribution models of temperature differences were further established and the extreme temperature differences were estimated with a return period of 100 years.Finally,the temperature difference models in cross-section area were proposed for bridge thermal design.The results show that horizontal temperature differences in top plate and vertical temperature differences between top plate and bottom plate are considerable.All the positive and negative temperature differences can be described by the weighted sum of two Weibull distributions.The maximum positive and negative horizontal temperature differences in top plate are 10.30 ℃ and -13.80 ℃,respectively.And the maximum positive and negative vertical temperature differences between top plate and bottom plate are 17.30 ℃ and-3.70 ℃,respectively.For bridge thermal design,there are two vertical temperature difference models between top plate and bottom plate,and six horizontal temperature difference models in top plate.

A Statistical Analysis of the Modulus of Elasticity and Compressive Strength of Concrete C45/55 for Pre-stressed Precast Beams

Random behavior of concrete C45/55 XF2 used for prefabricated pre-stressed bridge beams is described on the basis of evaluating a vast set of measurements. A detailed statistical analysis is carried out on 133 test results of cylinders 150 ~ 300 mm in size. The tests have been running in laboratories of the Klokner Institute. A single worker took all specimens throughout the period, and the subsequent measurements of the static modulus of elasticity and the compressive strength of the concrete were performed. The measurements were made at the age of 28 days after specimens casting, and only one testing machine with the same capping method was used. Suitable theoretical models of division are determined on the basis of tests in good congruence, with the use of Z2 and the Bernstein criterion. A set of concrete compressive strength （carried out on 133 test results of cylinders 150 ~ 300 mm after test of static modulus of elasticity） shows relatively high skewness in this specific case. This cause that limited beta distribution is better than generally recommended theoretical distribution for strength the normal or lognormal. The modulus of elasticity is not significantly affected due to skewness because the design value is based on mean value.

A Teaching Experiment in Modelling through Scale Reduction Methods： A Bridge to Later Trigonometric Methods

In a teaching experiment, Japanese Grade 9 students investigated how to measure the height of an aerial balloon using different models involving angles and distances, and also to evaluate the models they developed. As novices to mathematical modelling, they needed to decide which of several possible models were both valid and practicable, and the errors in measurement that are likely to arise. Opportunities to construct and use paper models, as scale reductions of the real situation, and discussing their results in small groups were effective in moving forward the thinking of many students on the dimensions mentioned above. While students were less able to identify different sources of errors, many came to appreciate the need to learn trigonometric techniques that are more suitable in dealing with problems of this kind.

Dynamic Response on Free-Free Beam in Driving Point and Transfer Mobility Measurement under Bending Load

This paper aims to present the experimental result obtained from dynamic response on flee-flee beam in driving point and transfer mobility analysis using impact test method using hammer tips that are steel, plastic and rubber. The 8630C accelerometer and analyzer is used for data logging and for the analysis, the plastic hammer tip is chosen. The analytical and the experimental value then are compared for the free-free beam natural frequency, damping ratio, and stiffness value. As a result, the highest percentage error for natural frequency is approximated to 2.7%, the damping ratio is approximated to 3.115 × 10^-3 and the stiffness value gives the major different between the experiment value and theoretical value. Finally, this method can be used to determine the properties of a structure such as natural frequency, mode shapes, damping ration and stiffness, respectively.

Measurement and numerical analysis of influence of key stratum breakage on mine pressure in top-coal caving face with super great mining height

To analyze the influence of movement in shallow-buried working faces with large mining heights on mine pressure manifestation, the key stratum at a working face was categorised using the 1313 top-coal caving face with super great mining height under cover as a case study. The research combined theoretical analysis, field measurement, and numerical simulation to analyze the influencing mechanism of key stratum. Moreover, the research results were verified by numerical simulation and indicate that the sub-key stratum is prone to be broken to form a "cantilever beam" structure rather than a stable hinged structure during the excavation of working faces with super great mining heights. When the "cantilever beam" structure is unstable, a low pressure will occur on the working face, and the overlying strata will subside simultaneously with the sub-key stratum to induce the breakage of the primary key stratum: the breakage will further trigger the periodic breakage of sub-key stratum, causing a greater load on the working face. Finally, steps, and strength of weighting in the working face vary to be great or small alternatively. This is the main reason explaining why the 1313 working face shows strong mine pressure manifestation. The results provide theoretical and practical experience for forecasting and controlling mine pressure manifestation.

Measuring the thermal conductivity and interfacial thermal resistance of suspended MoS2 using electron beam self-heating technique

Establishment of a new technique or extension of an existing technique for thermal and thermoelectric measurements to a more challenging system is an important task to explore the thermal and thermoelectric properties of various materials and systems. The bottleneck lies in the challenges in measuring the thermal contact resistance. In this work, we applied electron beam self-heating technique to derive the intrinsic thermal conductivity of suspended Molybdenum Disulfide （MoS2） ribbons and the thermal contact resistance, with which the interracial thermal resistance between few-layer MoS2 and Pt electrodes was calculated. The measured room temperature thermal conductivity of MoS2 is around -30 W/（m K）, while the estimated interracial thermal resistance is around -2 × 10 -6 m-2 K/W. Our experiments extend a useful branch in application of this technique for studying thermal properties of suspended layered ribbons and have potential application in investigating the interracial thermal resistance of different twodimensional （2D） heterojunctions.

Fuzzy finite element model updating of bridges by considering the uncertainty of the measured modal parameters

It is significant to consider the effect of uncertainty of the measured modal parameters on the updated finite element(FE) model,especially for updating the FE model of practical bridges,since the uncertainty of the measured modal parameters cannot be ignored owing to the application of output-only identification method and the existence of the measured noise.A reasonable method is to define the objective of the FE model updating as the statistical property of the measured modal parameters obtained by conducting couples of identical modal tests,however,it is usually impossible to implement repeated modal test due to the limit of practical situation and economic reason.In this study,a method based on fuzzy finite element(FFM) was proposed in order to consider the effect of the uncertainty of the measured modal parameters on the updated FE model by using the results of a single modal test.The updating parameters of bridges were deemed as fuzzy variables,and then the fuzzification of objective of the FE model updating was proposed to consider the uncertainty of the measured modal parameters.Finally,the effectiveness of the proposed method was verified by updating the FE model of a practical bridge with the measured modal parameters.

Design and realization of high precision FBG rain gauge based on triangle cantilever beam and its performance research

A novel fiber Bragg grating （FBG） rain gauge is proposed in this paper to achieve high precision rainfall measurement. One core sensitive FBG, a temperature compensation FBG and a mechanical transition system construct this novel FBG rain gauge. Sensing principle of this FBG rain gauge is explained in detail, and its theoretical calculation model is also established, which shows that the relationship between center wavelength of sensitive FBG and external rainfall has very good linearity. To verify its detection performance, the calibration experiment on one prototype of this FBG rain gauge is carried out. After experiment data analysis, the detection precision of this FBG rain gauge is 15.4/.tm which is almost two orders of magnitude higher than that of the existing rainfall measurement device. The experimental data confirm that this FBG rain gauge can achieve rainfall measurement with high precision.

Mass Flow Prediction of the Coriolis Meter using C^0 Continuous Beam Elements

A three node C^0 continuous isoparametric beam element is formulated to model the curved pipe conveying fluid in three dimensional configuration.The equations of motion for the combined structure and fluid domain including added mass effect,Coriolis effect,centrifugal effect and the effect of pressure on the walls of pipe have been developed by Paidoussis.This equation is converted to finite element formulation using Galerkin technique and is validated with the results available from literature.