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., Technical papers, Published. Received February 23, 2005; Accepted May 05, 2006; Published online December 01, 2006.
In many mechanical systems, the tendency of sliding components to intermittently stick and slip leads to undesirable performance, vibration, and control behaviors. Computer simulations of mechanical systems with friction are difficult because of the strongly nonlinear behavior of the friction force near zero sliding velocity. In this paper, two improved friction models are proposed. One model is based on the force-balance method and the other model uses a spring-damper during sticking. The models are tested on hundreds of lumped mass-spring-damper systems with time-varying excitation and normal contact forces for both one-dimensional and two-dimensional stick-slip motions on a planar surface. Piece-wise continuous analytical solutions are compared with solutions using other published force-balance and spring-damper friction models. A method has been developed to set the size of the velocity window for Karnopp’s friction model. The extensive test results show that the new force-balance algorithm gives much lower sticking velocity errors compared to the original method and that the new spring-damper algorithm exhibits no spikes at the beginning of sticking. Weibull distributions of the sticking velocity errors enable maximum errors to be estimated a priori., Technical papers, Published. Received February 03, 2000; Revised August 17, 2000.
It is essential to design and operate buildings with good indoor air quality because people spend most of their time indoors, and their productivity, comfort, and health depend on the quality of the indoor air. In addition to other indoor-air-quality parameters, the indoor humidity and temperature need to be controlled and maintained within acceptable ranges. Elevated indoor humidity creates favorable conditions for mold growth and building-envelope damage. To minimize such problems, it is important that designers have insight into the level of indoor humidity that will be expected in a building operating under a set of conditions and weather variation. In this paper, the results of monitoring the indoor temperature and humidity of four apartment suites with different occupancy levels are reported. Along with the indoor-air conditions, the local outdoor temperature and relative humidity were continuously measured for 17 months. The indoor humidities in the suites were correlated with the outdoor air temperature and humidity and compared with the European indoor climate class model. Moreover, the indoor-temperature and relative-humidity ranges in the four suites during the winter, spring, summer, and fall seasons and the temperature and humidity distributions within the suites are reported., Technical papers, Published. Received: September 22, 2014. Accepted: February 03, 2015. Published online: April 21, 2015.