Application of Hygrothermal Modeling Tool to Assess Moisture Response of Exterior Walls

The moisture design of exterior walls in a building envelope is an important task that needs to be carried out systematically to generate a sustainable and healthy built environment. Many conventional methods or practice guidelines are available for this purpose, based primarily on local traditions and with limited performance assessment records. In recent years, with the rapid development of global free trade and economy, new wall systems and unconventional materials have been introduced in every part of the world for reasons such as aesthetic appeal, cost effectiveness and so on. However, neither the long-term moisture management performance of these new wall systems nor the uses of unconventional materials have been assessed in a systematic way. The primary reason for this lack of assessment is the absence of a design-oriented methodology to perform the task. This paper presents selected results from a recently completed research project that demonstrate that it is indeed possible to assess the moisture management performance of exterior walls in a systematic way, using a hygrothermal modeling tool together with key inputs from a limited number of laboratory and field investigations. In this project the hygrothermal responses of exterior walls and their components were assessed with a novel moisture response indicator, called the RHT index, which is derived from relative humidity and temperature data over a time period. The results and discussion presented in this paper clearly show the need and usefulness of the application of hygrothermal simulation tool for the optimum moisture design of exterior wall systems in various geographic locations, when sufficient information is available from laboratory and field experiments.     

Experimental Investigation of the Influence of Moisture on the Bond Behavior of FRP to Concrete Interfaces

The effects of moisture on the initial and long-term bonding behavior of fiber reinforced polymer (FRP) sheets to concrete interfaces have been investigated by means of a two-year experimental exposure program. The research is focused on the effects of (1) moisture at the time of FRP installation, in this paper termed “construction moisture,” consisting of concrete substratum surface moisture and external air moisture; and (2) moisture, in this paper termed “service moisture,” which normally varies throughout the service life of concrete. Concrete beams with FRP bonded to their soffits were prepared. Before bonding, concrete substrates were preconditioned with different moisture contents and treated with different primers. The FRP bonded concrete beams were then cured under different humidity conditions before being subjected to combined wet/dry (WD) and thermal cycling regimes to accelerate the exposure effects. Adhesives with different elastic moduli were used to investigate the long-term durability of each adhesive when subjected to accelerated WD cycling. Pull-off tests and bending tests were conducted at the beginning of the cycling and then again after 8 months, 14 months, and 2 years of exposure so as to evaluate the tensile and shear performance of the FRP-to-concrete interfaces. It was found that the effect of the concrete substrate moisture content on short-term interfacial bond performance could be eliminated if an appropriate primer was used. All FRP-to-concrete bonded joints failed at the interface between the primer and concrete after exposure while those not exposed usually failed within the concrete substrate. After exposure to an environment of accelerated WD cycles, it was also found that the interfacial tensile bond strength degraded asymptotically with the exposure time while the flexural capacity of the FRP sheet bonded plain concrete beams even increased. The mechanism behind the above, which is an apparently contradictory phenomenon, is discussed.     

Exposure to Condensation Moisture of Sheathing in Retrofitted Leaky Wall Assemblies

Exfiltration of moist indoor air during winter conditions may lead to the gradual wetting of the sheathing of wall assemblies that are not airtight. In this study, seven full-scale wood-frame wall specimens were tested to evaluate the impact of both the geometry of the air leakage path and the addition of rigid insulation on the warm side or the cold side of the assembly on the hygrothermal response of wall assemblies. Walls were exposed to 72?days of steady-state winter conditions and 47?days of steady-state late spring conditions. The position of the added rigid insulation and the geometry of the air leakage paths were different in each wall specimen. The moisture content of the fiberboard sheathing was monitored, and the results are presented. The evolution over time of the moisture distribution across the plane of the sheathing is also presented. The duration of exposure to moisture content above 19 and 28% is examined, allowing a comparison of the performance of the specimens. Leaky assemblies with vapor-tight insulation board added on their cold side were exposed to high moisture content longer than the assemblies not reinsulated or reinsulated on their warm side because the assemblies without insulation on the cold side of the sheathing were exposed to a buildup of frost that prevented moisture to be absorbed by the sheathing.     

Study of the Effect of Near-Source Vertical Ground Motion on Seismic Design of Precast Concrete Cladding Panels

This paper is an attempt to determine the effect of vertical ground motion on design of precast concrete cladding panels in seismic regions, particularly in near-source areas. A spandrel-type precast concrete cladding panel is chosen for detailed study and assumed attached to a building in San Francisco. The seismic provisions of International Building Code 2000 and Uniform Building Code 1997 are used to determine the design forces on the cladding panel, which was originally designed as an example in a PCI publication. The provisions of the two codes are compared in light of their requirements related to vertical ground motion consideration and near-source effects. Results of recent research on the relation between vertical and horizontal ground acceleration components as a function of source-to-site distance are also used to illustrate an example of incorporating vertical spectral acceleration effects directly in load combinations. Finally, finite-element modeling and frequency analysis results of the spandrel and floor-to-floor types of cladding panel are discussed. This study shows that the effects of vertical ground motion will cause an increase in the design forces for connections of heavy cladding panels, especially in near-source regions, with the magnitude of the increase dependent on the source-to-site distance.     

均匀设计方法在304H钢力学性能试验中的应用

 采用均匀设计方法模拟操作工况开停机过程,以加热温度、反复加热冷却次数、冷却方式以及高温停留时间为指标,通过对比钢材的屈服强度、伸长率、抗拉强度、冲击韧性和硬度,分析了不同工艺因素对304H钢力学性能的影响,结果表明：在620~750 ℃范围内,材料晶界上析出大量的相及二次碳化物,冲击韧性及屈服强度分别下降8%和12%,此结果对材料的设计与应用均具有参考意义。     

Failure Resistance of the Historic Stone Bridge Structure of Charles Bridge. I: Susceptibility to Nonstress Effects

The monitoring of deformations of the stone structure of Charles Bridge in Prague proved the gravity and relevance of nonstress effects (temperature, moisture content) on cyclic deformations and permanent strain accompanied by a gradual disintegration of its stone masonry, growing tilt of the breast walls, and development of cracks in the masonry of the stone bridge structure. Each deformation cycle is accompanied by a gradual growth in permanent deformations. The “unmanifested” primary deformation due to, e.g., a temperature change causes a mechanical state of tension, and it is mainly the tensile stresses thus arising that contribute to the development of tensile cracks in the stone masonry.     

Simplified Method to Include Cumulative Damage in the Seismic Response of Single-Degree-of-Freedom Systems

In this paper a consistent method including damage criteria in the seismic response of single-degree-of-freedom systems is proposed. The method allows the determination of suitably modified strength or displacement inelastic spectra through the introduction of an equivalent damage factor pdam that accounts for earthquake damage potential; analogously capacity spectra could be obtained. Three types of damage indices are considered (Park and Ang index DP&A, energy index DE, and low-cycle fatigue index DF) and derivation of pdam is pursued for all these cases. Moreover approximate simplified expressions in the function of Cosenza and Manfredi seismological ID index, which accounts for cyclic damage potential of an earthquake, are also proposed. In this way damage capacity spectra are obtained to improve the seismic assessment of existing structures including damage effect.     

抛落冲击力及其对球磨机筒体结构损伤的分析

湿式球磨机运行时矿石和钢球沿筒体内壁上升,到一定高度而抛落下来,对筒体产生冲击。但在筒体结构强度设计计算中此项冲击力是忽略不计的。根据理论分析和实际观察结果对此项抛落冲击力及其对筒体结构的损伤进行了初步探讨。并认为,必须考虑抛落冲击力对筒体结构强度的影响。最后,提出了防止抛落冲击力对筒体结构损伤的实际措施。     

一种测量塑料橡胶类材料声衰减的脉冲回波方法

利用两次脉冲回波试验中测量的延迟块自由底面回波、延迟块/测试样品界面回波以及橡胶试样底面回波共3个信号的傅立叶变换幅度谱,能够求取试样在一定频率范围内的声衰减值。与国标GB/T18022-2000中的方法相比,该方法具有装置简单、操作便捷的特点,并且能够用于测试试样的横波衰减。     

Application of the Viscoelastic Continuum Damage Model to the Indirect Tension Test at a Single Temperature

The viscoelastic continuum damage model, developed based on Schapery’s correspondence principle and the continuum damage mechanics, has received a great deal of attention because of its mathematical soundness and effectiveness in describing damage growth in viscoelastic media and has been used to make reliable estimations on the fatigue lives of asphalt mixtures. Its applications to field mixtures, however, have been limited because the model requires performing the uniaxial tension test. As an alternative, this study developed an analytical methodology for applying the model to the indirect tension test, which has been successfully used in testing both laboratory-made and field-cored mixtures. From the results of the indirect tension tests conducted on asphalt mixture at three different crosshead-controlled rates, it was found that the stress-pseudostrain curves could be superimposed onto one equality line in the linear viscoelastic range of the given mixture, and its rate dependency was successfully eliminated in the C1 and S1 plots. This indicates that the methodology developed for the indirect tension test has a capability of evaluating damage development in asphalt mixtures through the viscoelastic continuum damage model. It would be potentially of great benefit to pavement engineers who want to estimate the remaining lives of field mixtures.     

原子吸收分光光度法测定铅精矿中镉量

采用在盐酸介质(5％)中用原子吸收分光光度法于228．8nm波长测定铅精矿中镉量。用该方法,杂质元素不干扰试验,而且保证了精密度和回收率满足国家标准要求。方法简单、准确、易于掌握。     

将“承载能力法”引入吊钩设计计算的尝试

介绍了“承载能力法”的计算原理,通过应用此原理对天钢集团第二炼钢厂现有46t龙门钩进行校核及为榆次钢厂25t龙门钩的设计可以看出,此方法的引入对合理利用材料的承载能力,减轻吊钩重量具有十分重要的意义。     

A Clinical Trial to Test the Feasibility of a Telehealth Psychoeducational Intervention for Persons With Schizophrenia and Their Families: Intervention and 3-Month Findings.

Objective: To evaluate the feasibility of a telehealth psychoeducation intervention for persons with schizophrenia and their family members. Study Design: Randomized controlled trial. Participants: 30 persons with schizophrenia and 21 family members or other informal support persons. Interventions: Web-based psychoeducation program that provided online group therapy and education. Main Outcome Measures: Measures for persons with schizophrenia included perceived stress and perceived social support; for family members, they included disease-related distress and perceived social support. Results: At 3 months, participants with schizophrenia in the intervention group reported lower perceived stress (p = .04) and showed a trend for a higher perceived level of social support (p = .06). Conclusions: The findings demonstrate the feasibility and impact of providing telehealth-based psychosocial treatments, including online therapy groups, to persons with schizophrenia and their families. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

400kA电解槽降低壳头包结包率方式的研究

壳头包对铝电解正常生产有较大的危害,也会造成操作员劳动强度的增加。其形成的原因主要是电解质成分的剧烈变化、电解质黏度过大、打壳锤头在电解质中停留时间过长和两次打壳之间间隔过短。本文从改变电解槽大壳下料的方式来研究是否可以降低电解槽壳头包结包率,降低工人劳动强度,以及对工艺指标、技术指标有何影响。