Modelling of the performance of asphalt pavement using response surface methodology

Response surface methodology (RSM) is a practical and useful statistical procedure to develop empirical models for predicting asphalt pavement properties. In this work three empirical models were developed to predict the load and the flow resistance increment (ΔL and ΔF, respectively) according to ASTM D 5581 [Annual Book of ASTM Standards, Section 4, Construction, vol. 04.03, Roads and Paving Material; Vehicle-pavement Systems] and the “volatilised material” (VM) according to ASTM D 1188 [Annual Book of ASTM Standards, Section 4, Construction, vol. 04.03, Roads and Paving Material; Vehicle-pavement Systems] via RSM using the obtained properties of the specimens placed in a conventional oven for laboratory aging. In addition a mechanistic–empirical (M–E) model was proposed to describe the increment and decrement in surface course properties due to aging (A). The adequacy of the predicted properties by the models was demonstrated with the cores properties extracted from a pilot road.     

基于果蝇优化算法的GRNN模型在边坡稳定预测中的应用

鉴于边坡系统是一个复杂的多因素影响的非线性系统,综合考虑边坡的物理状态和环境因素,采用了一种基于果蝇优化算法(FOA)的广义回归神经网络(GRNN)模型(FOAGRNN)预测边坡的稳定状态,并与BP神经网络预测模型结果进行比较。结果表明,FOAGRNN预测的精度较高,基本反映了边坡稳定的真实状态。     

Thermo-elastic Stresses in a Functional Graded Material Under Thermal Loading,Pure Bending and Thermo-mechanical Coupling

Analytical expressions have been derived for the through thickness stresses of a Functional graded materials (FGMs) thin plate subjected to thermal loading, pure bending and thermo-mechanical coupling, respectively. The structure is comprised of a metallic layer, a ceramic layer and a functional graded layer. Continuous gradation of the volume fraction in the FGM layer is modeled in the form of an "m" power polynomial of the coordinate axis in thickness direction of the plate. Numerical scheme of discretizing the continuous FGM layer with different graded distributions such as linear (m=1), quadratic (m=2) and square root (m=0.5) has been developed by the averaging technique of composites. Solutions for the stress distributions have been derived for the system under thermal loading, pure bending and thermo-mechanical coupling, respectively.     

形状记忆合金在复合材料损伤监测中的应用

复合材料的损伤会对结构的可靠性和安全性造成威胁,近年来引起国内外专家和学者的广泛关注.本文将形状记忆合金(SMA)埋入复合材料试件中,通过对SMA电阻变化与复合材料应变之间的关系进行讨论,建立不同监测条件下复合材料的损伤监测理论模型.基于该模型讨论了不同初始状态下SMA材料的损伤监测行为.研究结果表明:复合材料的损伤与...     

基于弹性波理论的土石混填地基压实质量评价研究

为了准确、高效地评价土石混填地基的压实质量,提出了一种基于弹性波理论的压实质量评价新方法。通过理论与试验分析,建立了土石混合料的剪切波速模型,实现了由土石混合料宏观剪切波速推定出其中石料间细粒土的压实度,并以此来表征混合料整体压实质量。通过室内大型振动压实试验,得到在不同含石量与含水率时,混合料中细粒土所能达到的最大干密度(或压实度),以此作为土石混合料表征压实度评价的参考标准。研究了土石混合料剪切波速与瑞雷面波波速的关系,使得利用现场瞬态面波测试所得到的频散曲线来反演计算剪切波速成为可能。最后通过对某机场跑道填筑工程土石混填地基压实质量的评价,验证了评价方法的可行性。     

Behaviour of welded beam-to-column joints with beams of unequal depth

The objective of the current paper is to characterise the behaviour of internal asymmetric joints, which corresponds to a node configuration that is not yet covered in the EN 1993-1-8 design rules.For this purpose, a research programme was established that encompasses five different types of joints. Numerical models were prepared and calibrated with results from experimental tests on full scale models of the joints. The analyses of the results allowed the identification of the main features that influence the behaviour of asymmetric joints. This information was used to establish a behavioural model consistent with the component method philosophy.Furthermore, the analytical method supporting the component method was investigated, and the information gathered about the behaviour of the new configuration was used to tailor the reference model for the design of asymmetric joints.The modified analytical model was implemented for the asymmetric joints studied. The results were compared with those of the homologous calibrated numerical models. The quality of the adjustment was established in terms of the parameters representing the moment rotation curve for a joint, within the framework of the component method, and a quite reasonable adjustment is observed.     

Influences of different prior heat treatments on the microstructural and mechanical properties of Cu-Fe filamentary composites

Cu-6 wt.% Fe and Cu-12 wt.% Fe filamentary composites were prepared by casting and cold drawing. And a different heat treatment of quenching and aging or homogenizing was introduced before cold drawing process, respectively. The microstructure was observed and the tensile strength measured for the composites at different drawing strains. The quenching and aging or homogenizing prior to drawing deformation refine the as-cast microstructure and result in the increase in interface density in the drawn microstructure. The drawn alloys with the homogenizing treatment show smaller filament spacing than those with the quenching and aging treatment because homogenizing results in smaller and more dispersive primary Fe dendrites before drawing deformation. The heat treatments can improve the strength of the composites by increasing precipitation strengthening and interface strengthening levels. With the reduction in filament spacing during drawing deformation, the strength of the alloys with smaller initial size of Fe dendrites increases more obviously.     

声波透射法桩基检测中声测管弯斜小波分析

为消除声测管弯斜对桩基检测结果准确性的影响,根据一维小波分析原理,在深入分析声波透射法测管弯斜时检测信号特点的基础上,运用一维小波分析原理通过计算机模拟得到了弯斜识别效果最优的小波函数。建立了声测管弯斜修正模型,利用修正模型对实际工程中某桥梁桩基声测管发生弯斜的检测数据予以修正,修正后的数据不仅能够消除声测管弯斜对检测数据的影响,且保留了检测信号中有用的高频信息,取得了较好的修正效果。     

SRB对航煤输送管道X70碳钢的腐蚀影响

通过宏观形貌分析、金相分析、pH值分析、硫含量分析及失重法等综合手段对不同条件下硫酸盐还原菌(SRB)对航煤管道X70碳钢的腐蚀程度进行研究。结果表明:SRB可以促进X70碳钢腐蚀,且腐蚀以点蚀为主;SRB可以导致航空煤油中的硫含量增加,温度越高,SRB浓度越大,增加的越明显,尤其是第一周增加的幅度最大;SRB可以导致航空煤油中的pH值下降,第一周下降的最为明显,以后下降的较为平缓,渐渐的趋近于某一数值。     

残冰检测中飞机图像特征点精确提取算法

传统角点检测算法无法精确提取感兴趣的特征点。为此,提出一种新的特征点提取算法。通过曲率角点检测算法提取飞机图像的特征点,并作为待匹配图像,采用像素相关性匹配算法进行特征点提取,利用飞机机身固定结构约束匹配算法去除误匹配对。实验结果表明,该算法具有较好的适应性,能够精确提取特征点。