Sensitivity analyses of cables to suspen-dome structural system

The construction of the cables is a key step for erecting suspen-dome structures. In practical engineering, it is difficult to ensure that the designed pre-stresses of cables have been exactly introduced into the structures in the site; so it is necessary to evaluate the influence of the variation of the pre-stresses on the structural behavior. In the present work, an orthogonal design method was employed to investigate the pre-stressed cables'sensitivity to the suspen-dome system. The investigation was concentrated on a Kiewitt suspen-dome. Parametric studies were carried out to study the sensitivity of the structure's static behavior, dynamic behavior, and buckling loads when the pre-stresses in the cables varied. The investigation indicated that suspen-dome structures are sensitive to the pre-stresses in all cables; and that the sensitivity depended on the location of the cables and the kind of structural behavior. Useful suggestions are given at the end of the paper.     

Analysis of tensioned membrane structures considering cable sliding

INTRODUCTIONTensionedmembranestructuresaremostsuitableforuseasroofstructureforavarietyofbuildingtypes,astheyprovidealight,elegant,andefficientstructurespanningoveralargeclearspace (Otto,1 973 ) .Examplesincludegymnasi ums,exhibitioncenters ,concertpavilio…     

Analysis of tensioned membrane structures considering cable sliding

In routine design of tensioned membrane st ructures, the membrane is gen erally modeled using space membrane elements and the cables by space cable eleme nts, with no sliding allowed between the membrane and the cables. On the other h and, large deflections are expected and sliding between the membrane and the cab les is inevitable. In the present paper, the general finite element code ABAQUS was employed to investigate the influence of cable sliding on membrane surface o n the structural behavior. Three analysis models were devised to fulfill this pu rpose: (1) The membrane element shares nodes with the cable element; (2) The cab le can slide on the membrane surface freely (without friction) and (3) The cable can slide on the membrane surface, but with friction between the cable and the membrane. The sliding problem is modeled using a surface-based contact algorithm . The results from three analysis models are compared, showing that cable slidin g has only little influence on the structure shape and on the stress distributio ns in the membrane. The main influence of cable sliding may be its effect on the dynamic behavior of tensioned membrane structures.     

Nonlinear dynamic response of stay cables under axial harmonic excitation

This paper proposes a new numerical simulation method for analyzing the parametric vibration of stay cables based on the theory of nonlinear dynamic response of structures under the asynchronous support excitation. The effects of important parameters related to parametric vibration of cables, i.e., characteristics of structure, excitation frequency, excitation amplitude, damping effect of the air and the viscous damping coefficient of the cables, were investigated by using the proposed method for the cables with significant length difference as examples. The analysis results show that nonlinear finite element method is a powerful technique in analyzing the parametric vibration of cables, the behavior of parametric vibration of the two cables with different Irvine parameters has similar properties, the amplitudes of parametric vibration of cables are related to the frequency and amplitude of harmonic support excitations and the effect of distributed viscous damping on parametric vibration of the cables is very small.     

Node shift method for stiffness-based optimization of single-layer reticulated shells简

This paper presents a node shift method to find the optimal distribution of nodes in single-layer reticulated shells. The optimization process searches for the minimum strain energy configuration and this leads to reduced sensitivity in initial imper- fections. Strain energy sensitivity numbers are derived for free shift and restricted shift where nodes can move freely in the 3D space or have to move within a predefmed surface respectively. Numerical examples demonstrate the efficiency of the proposed approach. It was found that optimized structures achieve higher ultimate load and are less sensitive to imperfections than the initial structure. The configuration of the final structure is closely related to factors like the initial structural configuration, spatial conditions, etc. Based on different initial conditions, architects can be provided with diverse reasonable structures. Furthermore, by amending the defined shapes and nodal distributions, it is possible to improve the mechanical behavior of the structures.     

Mechanical behavior of a shelter system based on cable-strut structures

A shelter system based on cable-strut structures,consisting of compressive struts and high-tensile elements,is described in this paper.The deployment of the shelter is achieved by tightening inclined cables.Lower cables are used to terminate the deployment.The state of self-stress of the cable-strut structures in the fully deployed configuration is given,and the minimum strut length and the maximum load design of the shelter are discussed.The mechanical behavior of the system was studied under symmetrical and asymmetrical load cases.The results show that the shelter in the deployed configuration satisfies the ultimate limit and the serviceability limit state conditions.Finally,the stability of the cable-strut system is investigated,considering the effect of imperfections on the buckling of the shelter.We conclude that the influence of imperfections based on the consistent imperfection mode method is not significant.     

Healing temperature of hybrid structures based on genetic algorithm

The healing temperature of suspen-dome with stacked arches(SDSA)and arch-supported single-layer lattice shell structures was investigated based on the genetic algorithm. The temperature field of arch under solar radiation was derived by FLUENT to investigate the influence of solar radiation on the determination of the healing temperature. Moreover, a multi-scale model was established to apply the complex temperature field under solar radiation. The change in the mechanical response of these two kinds of structures with the healing temperature was discussed. It can be concluded that solar radiation has great influence on the healing temperature, and the genetic algorithm can be effectively used in the optimization of the healing temperature for hybrid structures.     

利用高延性水泥基材料抑制钢/混凝土连接区域的断裂破坏(英文)

为了避免混凝土的脆性断裂破坏,在钢/混凝土连接区域中用高延性水泥基材料(ECC)代替了普通混凝土. 采用剪力键/ECC 的抗剪试验、二维锚固螺栓/ECC 拔出试验和有限元模拟研究了 ECC 材料的延性对于连接区域破坏模式、结构性能的影响. 实验结果表明: 通过微观力学原理设计的 ECC 具有 300 倍于普通混凝土的拉伸延性,从而使钢/混凝土连接区中混凝土断裂破坏模式由脆性转变为延性. 混凝土材料的高延性使结构承载能力和变形性能获得改善,这也同时为有限元模拟结果所验证. 通过改变混凝土材料延性而提高结构性能的理念也可在其他类似的钢/混凝土组合结构中得到应用.     

Beyond Cross-Language Transfer: Reconceptualizing the Impact of Early Bilingualism on Phonological Awareness

This study investigates effects of early bilingualism on phonological awareness that are abstract and beyond cross-language transfer. It extends the scope of previous research by systematically examining hypotheses derived from structural sensitivity theory. The theory postulates that having access to two languages renders structural similarities and differences between languages more salient, thus allowing bilingual children to form representations of language structure at a more abstract level. About 200 bilingual and monolingual kindergartners, first-graders, and second-graders in Taiwan participated in experiments taking into account the syllable structures, the phoneme inventories, and the phonotactics of the bilinguals' two languages. Findings from the study provide empirical support for structural sensitivity theory and indicate the need to reconceptualize the bilingual effect on metalinguistic development beyond cross-language transfer.     

Aggregating concept map data to investigate the knowledge of beginning CS students

Concept maps have a long history in educational settings as a tool for teaching, learning, and assessing. As an assessment tool, they are predominantly used to extract the structural configuration of learners’ knowledge. This article presents an investigation of the knowledge structures of a large group of beginning CS students. The investigation is based on a method that collects, aggregates, and automatically analyzes the concept maps of a group of learners as a whole, to identify common structural configurations and differences in the learners’ knowledge. It shows that those students who have attended CS education in their secondary school life have, on average, configured their knowledge about typical core CS/OOP concepts differently. Also, artifacts of their particular CS curriculum are visible in their externalized knowledge. The data structures and analysis methods necessary for working with concept landscapes have been implemented as a GNU R package that is freely available.     

Dynamic responses of cable-stayed bridges to vehicular loading including the effects of the local vibration of cables

Stay cables, the primary load carrying components of cable-stayed bridges (CSBs), are characterised by high flexibility which increases with the span of the bridge. This makes stay cables vulnerable to local vibrations which may have significant effects on the dynamic responses of long-span CSBs. Hence, it is essential to account for these effects in the assessment of the dynamics CSBs. In this paper, the dynamic responses of CSBs under vehicular loads are studied using the finite element method (FEM), while the local vibration of stay cables is analyzed using the substructure method. A case study of a cable-stayed steel bridge with a center span of 448 m demonstrates that stay cables undergo large displacements in the primary mode of the whole bridge although, in general, a cable’s local vibrations are not obvious. The road surface roughness has significant effects on the interaction force between the deck and vehicle but little effect on the global response of the bridge. Load impact factors of the main girder and tower are small, and the impact factors of the tension of cables are larger than those of the displacements of girders and towers.     

Research News

In secondary schools, subjects dominate teaching and also the organizational structures. Typically, subject department heads perform a middle-management role in secondary schools and often this role is taken-for-granted and unquestioned. In this article, we examine the impact on secondary school culture and the resulting changes to practice when the department middle-management structure and roles are open to revision. We investigate the experiences of two schools that are part of a longitudinal study on reculturing and restructuring in all secondary schools in one school district in Ontario, Canada. Our research indicates that structural change initiated by school level participants is a prerequisite to real change and that structural changes preceded cultural changes. However, it is the process of creating the new structures that is the key consideration as mandating an alternative might not be facilitative of cultural change. The primary research question guiding this article is: what impact does involvement in restructuring a middle-management organizational model have on the culture of a school and the change process experienced by staff members?     

Aerodynamic stability of cable-supported bridges using CFRP cables

To gain understanding of the applicability of carbon fiber reinforced polymer (CFRP) cable in cable-supported bridges, based on the Runyang Bridge and Jinsha Bridge, a suspension bridge using CFRP cables and a cable-stayed bridge using CFRP stay cables are designed, in which the cable’s cross-sectional area is determined by the principle of equivalent axial stiffness. Numerical investigations on the aerodynamic stability of the two bridges are conducted by 3D nonlinear aerodynamic stability analysis. The results showed that as CFRP cables are used in cable-supported bridges, for suspension bridge, its aerodynamic stability is superior to that of the case using steel cables due to the great increase of the torsional frequency; for cable-stayed bridge, its aerodynamic stability is basically the same as that of the case using steel stay cables. Therefore as far as the wind stability is considered, the use of CFRP cables in cable-supported bridges is feasible, and the cable’s cross-sectional area should be deter-mined by the principle of equivalent axial stiffness.     

A tale of two technical cultures: Foreign language teaching

In broad terms this study investigated how the social organization of schools affects and is affected by the structures within which teachers find themselves: in essence how teachers shaped their reality. In particular this investigation was concerned with high school foreign language (FL) teachers' perceptions of their work environment; specifically how FL teachers in differing school contexts defined FL instruction and the manner in which these contextual definitions associated with their classroom behavior. Many previous investigations have focused on the relationship of teachers' classroom behavior and student outcomes. This study instead asked what the organizational antecedents for teachers' classroom practices are by documenting high school FL teachers' technical cultures—the processes designed to accomplish an organization's goals (Lortie, 1975; Rosenholtz, 1989).     

Hypoplasticmodeling of soil-structure interfaces in offshore applications

Cyclic and monotonic loaded offshore structures (e.g. piles, pipelines, cables, and suction-buckets) must be designed and calculated considering the effects of the soil-structure interaction. An advanced constitutive soil model must be used, but a simplified Mohr-Coulomb friction law is applied for the soil-structure interface. The Mohr- Coulomb model is a simple bilinear friction model that cannot take into account monotonic and cyclic interface phenomena. These include hardening, softening, and stiffness degradation under loading. However, we propose two advanced hypoplastic interface models for fine- and coarse-grained soils with intergranular strain concept. The intergranular strain concept has been proven to be an efficient way to model the small-strain deformation and un/reloading behavior of soils. The intergranular strain concept is therefore used to enhance the prediction capabilities of the hypoplastic interface models. Differences of the recent model formulation compared with previous versions are presented and discussed based on simulation. This is followed by an application of different models in finite-element simulations. The new models are used to simulate cyclic direct shear interface tests. Furthermore, the advanced interface model is used for simulation of a torodial penetrometer penetration problem. Several aspects, which are particularly important for offshore structures, are compared with the simple Mohr-Coulomb friction model.     

Advanced aerostatic analysis of long-span suspension bridges

INTRODUCTION Two examples of the great progress achieved inrecent decades in the design and construction oflong-span suspension bridges are the Akashi KaikyoBridge (1990 m) in Japan and the Great Belt Bridge(1624 m) in Denmark. Into the 21st century, longersuspension bridges are being planned, such as theMessina strait bridge in Italy (3300 m), and the Gi-braltar bridge between Spain and Morocco (5000 m)(Astiz, 1998), etc. In China, five large strait crossingprojects have been planne…     

预应力钢结构微尺模型实验技术

为研究微尺模型中预应力拉索的相关实验技术,以竖向预应力钢结构体系中2个典型结构为对象进行了试验,主要阐述微尺试验模型的设计、预应力的施加与测定方法、外荷载的施加方法,并着重分析了这些方法的优缺点。结果表明,螺杆拧张法施加预应力能够较好地模拟拉索只受拉不受压的受力特点,但存在系统误差,与该法配套宜采用传感器测试拉索力;丝扣拧张法施加预应力相对比较精确,但不便于更换拉索,与该法配套宜采用应变片测试拉索力。     

Adolescent boys' and girls' block constructions differ in structural balance: A block-building characteristic related to math achievement

Two studies were conducted on block building in adolescents, assessing middle school (Study 1) and high school students (Study 2). Students were asked to build something interesting with blocks. In both samples, the same pattern of gender differences were found; boys built taller structures than girls, and balanced a larger number of blocks on a small base of upright blocks (a new measure developed for this study). Gender differences in the height of structures were fully mediated by this measure of structural balance. These findings suggest that balance elements are key to understanding gender differences in block building. In Study 2, high-school students were given a second task, requiring them to apply structural balance principles (only four upright blocks were provided on which to build), and instructing them to build a tall, complex, well-balanced structure. Gender differences again were found, suggesting that gender differences in block building may be skill-based as well as stylistic. A separate question was whether block-building characteristics at this age have any relevance to math achievement. In both studies, the measure of structural balance was the only block-building characteristic that predicted math achievement. Additional research is needed to understand the cognitive underpinnings of this new spatial measure, how malleable it is, and its further practical significance for adolescent learners.     

Protective and vulnerability factors for physically abused children: effects of ethnicity and parenting context

OBJECTIVE: Although social maladjustment appears to be common among abused children, negative outcomes are not inevitable. This investigation was designed to determine whether ethnicity and features of the parenting context predicted children's social adjustment, and whether the strength and direction of these relations differed for abused and nonabused children. METHOD: Participants included 78 physically abused and 75 demographically matched nonabused children and one of their parents. Observations of parenting were used to measure parental sensitivity, and parent self-reports of depression were obtained using the SCL-90-R. Children's peer social adjustment was measured by teacher report. RESULTS: Using regression analysis, we tested whether each potential protective or vulnerability factor interacted with abuse status in prediction of social adjustment. Results indicated main effects of ethnicity and sensitivity for prosocial behavior, and a main effect of sensitivity for aggression. In addition, there was a significant interaction of ethnicity and abuse status for aggression such that there was a significant difference between abused and nonabused European American children but not between abused and nonabused African American children. CONCLUSIONS: Findings indicate that risk for aggressive behavior among abused children might be culturally specific rather than universal. In addition, results point to beneficial effects of parental sensitivity for maltreated children.