Deflection Calculation of FRP Reinforced Concrete Beams Based on Modifications to the Existing Branson Equation

Fundamental concepts of tension stiffening are used to explain why Branson’s equation for the effective moment of inertia Ie does not predict deflection well for fiber reinforced polymer (FRP) reinforced concrete beams. The tension stiffening component in Branson’s equation is shown to depend on the ratio of gross-to-cracked moment of inertia (Ig/Icr), and gives too much tension stiffening for beams with an Ig/Icr ratio greater than 3. FRP beams typically have an Ig/Icr ratio greater than 5, leading to a much stiffer response and underprediction of computed deflections as observed by others in the past. One common approach to computing deflection of FRP reinforced concrete beams has been to use a modified form of the Branson equation. This paper presents a rational development of appropriate modification factors needed to reduce the tension stiffening component in Branson’s original expression to realistic levels. Computed deflections using this approach give reasonable results with the right modification factor, and compare well with a more general unified approach that incorporates a realistic tension stiffening model. Comparison is made with the existing and past correction factors recommended by ACI 440 for predicting deflection of FRP beams. The method presently used by ACI 440 gives reasonable estimates of deflection for glass and carbon FRP reinforced beams. However, this method underestimates deflection of aramid FRP reinforced beams and is restricted to rectangular sections. A proposal is made for adoption of a simple modification factor that works well for all types of FRP bar and beam cross-sectional shape.     

Proposed Design of a CFRP Flange-to-Flange Connection for Precast Prestressed Double Tee Systems

The current methods of connecting the flanges of precast double tee members, and their respective short comings in specific situations, are described. A new carbon fiber-reinforced polymer (CFRP) flange-to-flange connection is proposed to eliminate the problems associated with repair requirements for the current connections. Design expressions for the currently used mechanical anchorage and the proposed CFRP connection are presented. A comparative calculation for the two systems is given.     

Eye movements of young and older adults during reading.

The eye movements of young and older adults were tracked as they read sentences varying in syntactic complexity. In Experiment 1, cleft object and object relative clause sentences were more difficult to process than cleft subject and subject relative clause sentences; however, older adults made many more regressions, resulting in increased regression path fixation times and total fixation times, than young adults while processing cleft object and object relative clause sentences. In Experiment 2, older adults experienced more difficulty than young adults while reading cleft and relative clause sentences with temporary syntactic ambiguities created by deleting the that complementizers. Regression analyses indicated that readers with smaller working memories need more regressions and longer fixation times to process cleft object and object relative clause sentences. These results suggest that age-associated declines in working memory do affect syntactic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Beyond Boundary Objects: Collaborative Reuse in Aircraft Technical Support

Boundary objects are a critical, but understudied, theoretical construct in CSCW. Through a field study of aircraft technical support, we examined the role of boundary objects in the practical achievement of safety by service engineers. Their resolution of repair requests was preserved in the organization’s memory via three compound boundary objects. These crystallizations did not manifest a static interpretation, but instead were continually reinterpreted in light of meta-negotiations. This suggests design implications for organizational memory systems which can more fluidly represent the meta-negotiations surrounding boundary objects.     

用保形样条方法求解非定常对流扩散方程

在欧拉-拉格朗日分裂方法的基础上,本文发展了一种固定网格上的欧拉-拉格朗日分裂方法.保形样条方法(SPSM)被用来解决倒特征线插值问题.通过求解几个有精确解的例子,说明SPSM方法的解是单调无振荡的,并且数值耗散也是比较小的.     

聚合物复合材料填充剂的改性

在前人研究的基础之上，归纳总结了聚合物复合材料填充剂的种类，综述了对其进行表面改性的目的、条件、方法、工艺以及对改性结果的表征等。文章还分析了影响填充聚合物复合材料性能的因素，指出了今后发展的方向。     

机床工具产品色彩造型初探

本文针对我国机床工具产品色彩设计的现状,结合具体实例,对色彩造型的实质做了初步的探讨。分析了色彩造型和色彩装饰两种设计观和实践效果;以色彩与形状关系及作用的论证为引,论述色彩造型的三大功能作用。并提出可供机床工具产品色彩设计参考的具体设计方法和手段。