Nondestructive evaluation of in-place cement mortar compressive strength using spectral analysis of surface waves

This paper presents a modified experimental SASW method for nondestructive evaluation of the cement mortar compressive strength in in-place single-layer mortar slabs with a rather finite thickness. The tests were conducted on 3′ × 3′ × 4″ (91.44 × 91.44 × 10.16 cm) cement mortar slab specimens using steel balls as the impact source to generate surface waves at various frequencies. The boundary reflection effects were removed in this study by collecting only the wave forms before the time when the reflected compressive waves reach the receivers. The correlation between the surface wave velocity and the compressive strength was obtained by conducting the SASW tests at different ages of the slab specimens. The results can be applied to the quality control of early age concrete during the construction phase.     

利用瑞利波频谱分析法无损检测混凝土结构

本文系统的阐述了瑞利渡频谱分析法的原理、试验设备、试验方法和检测混凝土结构的优越性，通过对瑞利波特性的分析表明瑞利波频谱分析法在检测大体积、层状混凝土结构质量和确定结构中半闭合或充有水的裂缝的深度比其他（冲击回波法和超声脉冲法）检测方法具有较高的精度。     

非规则隔震结构考虑楼板变形影响的动力性能

针对非规则结构中两种典型的需要考虑楼板变形的情况，进行了隔震前后的动力时程分析计算及分析。指出时程分析方法力学概念明确、简单，计算结果可靠，为进一步研究考虑楼板变形的非规则隔震结构奠定了基础。     

Geometric non-linear analysis of thin plate structures using the harmonic coupled finite strip method

The paper describes a modified finite strip method embracing the harmonic coupled Fourier series treatment. The well known uncoupled formulation, first developed in the context of thin plate bending analysis, represents a semi-analytical finite element process. As far as linear analysis is concerned, it takes advantage of the orthogonality properties of harmonic functions in the stiffness matrix formulation. However in the case of the geometric stiffness matrix calculation, the integral expressions contain the products of trigonometric functions with higher-order exponents, and here the orthogonality characteristics are no longer valid. All harmonics are coupled, and the stiffness matrix order and bandwidth are proportional to the number of harmonics used.     

频域分析在反射波法中的应用

阐述了反射波法中频域分析的基本原理及分析过程,并结合工程实例揭示了频域分析与时域分析的互补验证关系,最后指出在实际检测过程中,尽量做到时、频域分析结果相吻合,以确保分析结果的准确性和可靠性。     

A new method to investigate the energy absorption characteristics of thin-walled metal circular tube using finite element analysis

A numerical study is made to investigate the energy absorbing rule of thin-walled metal circular tube made of three different materials (steel, copper, aluminum) by using response surface methodology (RSM). At the same time, the application prospect of RSM in terms of the research on the energy absorption rule of energy absorption structure can be explored. The test result shows that, the compression process of thin-walled metal circular tube can be divided into three stages: elastic stage, yielding plateau stage, compact stage; To get the greatest value of average plateau force (APF) , a tube with a shorter height and thicker wall should be adopted; To get the greatest length energy absorption (LEA), a tube with thicker wall should be adopted and the ratio of its height and diameter should be as big as possible; To get the greatest specific energy absorption (SEA), a tube with a thicker wall should be adopted and the ratio between its height and diameter should be as big as possible. Thus, it can be seen that, RSM is an advanced experiment design method, and it can be widely used in the research on the energy absorption characteristics of thin-walled metal circular tube and has a promising application prospect in the development of new energy absorbing material and structure.     

Stability analysis of slopes using the finite element method and limiting equilibrium approach

The limit equilibrium method is commonly used for slope stability analysis, being relatively simple compared with finite element analysis. Both methods were used to analyse homogeneous and inhomogeneous slopes, taking into account the rapid drawdown condition, the undrained clay soils and the presence of tension cracks. The analyses were carried out using PLAXIS 8.0 (finite element method) and SAS-MCT 4.0 (limit equilibrium approach). The safety factor and location of the critical slip surface obtained from the two methods are compared.      

Finite element reliability and sensitivity analysis of structures using the multiplicative dimensional reduction method

Finite element reliability analysis (FERA) has been used to evaluate the reliability of structures. In FERA, approximate methods are commonly used to estimate the mean and variance of the structural response, while its probability distribution is primarily derived based on the Monte Carlo simulation (MCS) method. This paper advances FERA by combining it with the multiplicative dimensional reduction method (M-DRM). The proposed M-DRM allows fairly accurate estimation of the statistical moments, as well as the probability distribution of the structural response. The distribution of the response is obtained using fractional moments, which are calculated from the M-DRM, along with the maximum entropy principle. The variance of the response, based on global sensitivity measures, is obtained as a by-product of the analysis. The proposed approach is integrated with the OpenSees software and is illustrated through examples of nonlinear finite element analyses of reinforced concrete and steel frames. The paper shows that the proposed approach is an accurate and efficient alternative for FERA.     

考虑破坏面转移和垃圾坝作用的边坡稳定分析

垃圾坝是山谷型填埋场和横向扩建填埋场中常采用的增稳措施;破坏面在衬里结构不同界面间发生转移也是被证实的规律,考虑破坏面转移和垃圾坝作用的垃圾体边坡稳定分析方法尚未见报道。通过将衬里结构中破坏面转移点作为分界点,将滑动垃圾体分成5个楔体,利用极限平衡条件建立了五楔体边坡稳定分析方法。研究结果表明,五楔体极限平衡分析方法能够分析考虑破坏面转移和垃圾坝影响的填埋体稳定性;考虑破坏面转移计算得到的安全系数低于不考虑考虑破坏面转移的计算结果,考虑破坏面转移的计算方法能够发现更危险的情况;填埋场安全系数随垃圾坝高度的增大而增大;垃圾坝的背坡有一最优坡度,垃圾坝的背坡小于这一坡度时,发生“坝背破坏”模式;垃圾坝的背坡大于这一坡度时,发生“坝底破坏”模式;最危险破坏面通过填埋场的背坡和底坡的衬里,再通过垃圾坝的坝背衬里界面或坝底。     

预拌泵送混凝土板面裂缝分析与控制

由于预拌泵送混凝土配料和制作的特殊性，使得它的裂缝概率高于非泵送混凝土。在详尽分析板面裂缝增多原因的基础上，有针对性地提出了消除混凝土裂缝控制的办法。如：严把原材料质量关，掺入膨胀剂，啬抗裂钢筋网，采用二次振捣等等。通过采取以上方法，对施工质量严格加以控制，可大大降低裂缝的出现。     

用因果分析法分析混凝土的施工质量控制

首先分析了混凝土质量的控制目标，在此基础上将混凝土施工质量影响因素归纳为人、法、机、料、环五大主因，由此对五大主因的具体内容进行了详细分析，并讨论了对各因素进行有效控制的方法，从而提高混凝土施工质量。     

厚松散层重复开采地表移动变形特征比较与分析

根据某矿厚松散层、大采深、长工作面、机械化采煤条件下2个初采和1个重复开采工作面观测站实测资料,通过移动变形计算和规律分析,获取了基于概率积分法的地表移动变形预计参数,从地表移动持续时间、下沉状态、地表移动盆地特征、概率积分法参数等方面总结了重复开采与初采时地表移动变形规律的差异,为类似地质采矿条件下的重复开采地表移动变形规律分析提供参考。     

免棱镜全站仪测量拱圈线形及其精度分析

为解决既有拱桥评定时拱圈线形测量的难题,提出了一种在拱桥侧面架设免棱镜全站仪测量拱圈线形的新方法,并给出了详细的操作步骤;分析了该方法的X和Z坐标测量误差的主要来源,根据误差传播定律,推导了X和Z坐标测量中误差的计算公式,并通过模拟试验和工程实例对测量精度进行了验证.研究结果表明,免棱镜全站仪测量拱圈线形具有测量精度高...