Validation of Analytical Multiparameter Homogenization Models for Out-of-Plane Loaded Masonry Walls by Means of the Finite Element Method

The linear elastic analysis of in-plane and out-of-plane loaded masonry walls is still significant under service loads and is required by codes of practice, therefore the knowledge of the homogenized mechanical properties of masonry is of relevant interest. The aim of this paper is to discuss the problem of the out-of-plane loaded masonry walls in detail and to assess the accuracy and reliability of different homogenization approaches presented in the technical literature, with particular interest in recent explicit formulas obtained through an asymptotic model (as reported by Cecchi and Sab in 2002). Several meaningful comparisons are presented for different types of new and historical masonry structures currently employed in Italy. The validation of the analytical models is carried out by means of a three-dimensional (3D) finite-element (FE) out-of-plane homogenization. A final structural comparison among analytical models, FE out-of-plane homogenization, and a computationally expensive heterogeneous 3D FE model is discussed for a simply supported square panel laterally loaded.     

Elastic Anisotropic Viscoplastic Modeling of the Strain-Rate-Dependent Stress–Strain Behavior of K0-Consolidated Natural Marine Clays in Triaxial Shear Tests

This paper presents a new three-dimensional (3D) anisotropic elastic viscoplastic (EVP) model for the time-dependent stress–strain behavior of K0-consolidated marine clays. A nonlinear creep function with a limit for the creep volumetric strain under an isotropic or odometer K0-consolidated stressing condition and a nonsymmetrical elliptical loading locus are incorporated in the 3D anisotropic EVP model. An α-line defines the inclination of the nonsymmetrical elliptical loading locus in the p′-q plane and is commonly used for natural soils. All model parameters are determined from the results of one set of consolidated undrained compression tests and an isotropic consolidation/creep test. With the parameters determined, the 3D anisotropic EVP model is used to simulate the behavior of K0-consolidation tests and the strain-rate-dependent stress–strain behaviors of the K0-consolidated triaxial compression and extension tests on natural Hong Kong marine deposit clay specimens. These triaxial K0-consolidated specimens were sheared at step-changed axial strain rates from +2?to?+0.2, +20, ?2 (unloading) and +2%/h (reloading) for compression tests; or from ?2?to??0.2, ?20, +2 (unloading), and ?2%/h (reloading) for extension tests, all in an undrained condition. The simulation results of all these tests are compared with the test results. The validation and limitations of the model are then evaluated and discussed.     

E-Society Portal: Integrating Urban Highway Construction Projects into the Knowledge City

Community involvement is an important factor for sustainable highway construction. Information and communication technologies provide a new and more effective approach to facilitate community involvement. However, there are too many parameters with conflicting and subjective definitions related to sustainability and too many stakeholders with varying degrees of interest and sophistication. There is a need for an effective tool to communicate project impacts on sustainability to local communities. This paper presents an ontology for stakeholder management and sustainability in highway construction. An ontology is a conceptual semantic model that attempts to capture human knowledge (both explicit and tacit) in a consistent manner. Ontologies include three main elements: a taxonomy (common vocabulary presented in concept trees), set of relationships (linking concepts across trees), and axioms (limitation/constraints on the behavior of concepts). The ontology was used to develop a portal for broadcasting highway design features to local communities. By browsing through the portal, a user can learn about project elements, the impacts of each element on sustainability issues, who is sponsoring such element, and what efforts have been made to reduce any impacts of such elements on local communities.     

Observations of Aggressive Children During Peer Provocation and With a Best Friend.

Observational methods were used to examine aggressive children's peer relations in 2 contexts: when being teased by a peer and when interacting with a best friend. Because aggressive children may have more difficulty than nonaggressive children in both peer contexts, the authors also examined whether relations between behaviors across contexts varied as a function of aggression. Results indicated that aggression was related to children's behavior when provoked. Children's behavior when provoked was associated with fewer positive and more negative interactions with their best friend, particularly for aggressive children. Results are discussed with respect to social norms in middle childhood and informing interventions for aggressive children. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reciprocal Associations Between Adolescent Sexual Activity and Quality of Youth-Parent Interactions.

The authors examined differences in adolescents' relationships with their parents before and after adolescent first sexual activity. Participants were 13,570 members of the core sample of the National Longitudinal Survey of Adolescent Health (Add Health) Waves 1 and 2. Path analyses examined changes in parent-adolescent closeness, shared activities, and problem-focused interactions associated with changes in sexual activity separately for sons and daughters and for mothers and fathers. Race, religion, age, urbanicity, and parents' education were controls. Results confirm that increased problem-focused interactions and decreased parental closeness and shared activities both precede and follow adolescent sexual activity. Maintaining positive parental relations after adolescent first sexual activity is discussed as a means to reduce risks associated with sex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

平均应变对0Cr18Ni10Ti钢随机循环应力-应变关系的影响规律

试验研究了平均应变对0Cr18Ni10Ti管道钢随机循环应力．应变关系的影响规律从节约试样和试验费用角度，提出了改进的极大似然疲劳试验法，以应变比分别为-1、-0．52、-0．22、0．029．0．18和0．48完成了104个试样的应变控制疲劳试验。揭示出材料具有Masing行为和完全平均应力松弛特征，现有平均应变理论无法表征其影响。因此．首先基于Ramberg-Osgood方程，应用广义极大似然法有效地测定出各应变比的材料随机循环应力-应变关系。通过比较各应变比的循环应力幅均值、循环应力幅均方差和概率循环应力幅，揭示出高可靠性管理时．平均应变具有降低循环应力幅作用，应变比接近0时最显著．偏离逐渐减弱，说明了研究平均应变效应．仅考虑均值．可能给出错误评价；必须综合考虑均值、均方差和样本量3因素才能给出合理评价。     

矢量法机构运动分析

矢量法机构运动分析是通过建立机构位移矢量关系进行机构运动分析的一种方法，它具有运动方程建立直观简单的特点。矢量法给出的是运动关系的函数表达式，这给机构运动全过程分析及计算机辅助分析机构运动提供了便利。     

New design relations for 2-DOF PID-like control systems

Self-regulating processes can be controlled by internal model control systems where the usual three-parameter model of the process is transformed into a rational model via a parametrized first-order approximant of the apparent dead time. Using feedback and feedforward compensators leads to 2-DOF PID controllers whose time constants cancel that of the rational model. To obtain the desired sensitivity of the actual control loop, the model adaptation parameter and a gain tuning factor in the control system are determined by functions of the normalized dead time. The response to setpoint changes is selected by means of the feedforward compensator or via a prefilter. Plots of the sensitivity and the simulation of step responses to changes in the controller setpoint or to disturbances, show the validity of these design relations for transfer functions representative of typical industrial processes.     

Direction relations and two-dimensional range queries: optimisation techniques

This paper defines direction relations (e.g., north, northeast) between two-dimensional objects and shows how they can be efficiently retrieved using B-, KDB- and R- tree-based data structures. Essentially, our work studies optimisation techniques for 2D range queries that arise during the processing of direction relations. We test the efficiency of alternative indexing methods through extensive experimentation and present analytical models that estimate their performance. The analytical estimates are shown to be very close to the actual results and can be used by spatial query optimizers in order to predict the retrieval cost. In addition, we implement modifications of the existing structures that yield better performance for certain queries. We conclude the paper by discussing the most suitable method depending on the type of the range and the properties of the data.     

Stress Dilatancy and Fabric Dependencies on Sand Behavior

A stress dilatancy model with embedded microstructural information, originally developed by the writers, is used to illustrate the pivotal importance of dilatancy and fabric on the behavior of sand. Fabric, as a second-order tensor, enters into the stress dilatancy equation obtained from a microscopic analysis of an ensemble of rigid particles. Model simulations of sand behavior are carried out in triaxial stress conditions along strain paths with varying degrees of controlled dilation (or compaction) including isochoric deformations as a particular case. Under particular strain paths and fabric conditions, it is shown that a relatively dense sand can succumb to instability or liquefaction under other than isochoric (undrained) conditions. This phenomenon is in accord with laboratory experiments in which dilation or compaction is controlled by modulating the amount of water flowing in or out of a sand specimen during shearing. Mixed drained–undrained loading paths are also simulated with particular reference to fabric dependence at a fixed void ratio. Model simulations capture most of the observed characteristics of sand response, such as instability and asymptotic behavior under various conditions.