Fastener-Based Computational Models of Cold-Formed Steel Shear Walls

Cold-formed steel (CFS) combined with wood sheathing, such as oriented strand board (OSB), forms shear walls that can provide lateral resistance to seismic forces. The ability to accurately predict building deformations in damaged states under seismic excitations is a must for modern performance-based seismic design. However, few static or dynamic tests have been conducted on the non-linear behavior of CFS shear walls. Thus, the purpose of this research work is to provide and demonstrate a fastener-based computational model of CFS wall models that incorporates essential nonlinearities that may eventually lead to improvement of the current seismic design requirements. The approach is based on the understanding that complex interaction of the fasteners with the sheathing is an important factor in the non-linear behavior of the shear wall. The computational model consists of beam-column elements for the CFS framing and a rigid diaphragm for the sheathing. The framing and sheathing are connected with non-linear zero-length fastener elements to capture the OSB sheathing damage surrounding the fastener area. Employing computational programs such as OpenSees and MATLAB, 4 ft. x 9 ft., 8 ft. x 9 ft. and 12 ft. x 9 ft. shear wall models are created, and monotonic lateral forces are applied to the computer models. The output data are then compared and analyzed with the available results of physical testing. The results indicate that the OpenSees model can accurately capture the initial stiffness, strength and non-linear behavior of the shear walls.

Exploring Assistance in Sweden and the United States

Few international comparisons of health services are performed using microlevel data. Using such data, this paper compares the need for and receipt of assistance with activities of daily living (ADLs) in comparable samples in the United States and Sweden, a country with a universal system of community-based services.Design and Methods: Data from national surveys of community residents completed at approximately the same time in each nation are used to create comparable measures of need and assistance. Descriptive and logistic regression analyses compare need and assistance patterns across the nations and identify individual factors that explain receipt of assistance and unmet needs.Results:Our results indicate that a simple story of greater use of paid formal services in Sweden and more unpaid informal use in the United States masks a more complex relationship. Assistance with ADLs seems to be more targeted in Sweden; narrow differences in assistance widen considerably when the analysis is limited to those reporting need. Implications:Although these two different health systems result in similar levels of overall ADL assistance, a detailed microlevel comparison reveals key distinctions. Further microlevel comparisons of access, cost, and quality in cross-national data can further aid our understanding of the consequences of health policy.