Analysis of light gage steel shear diaphragms

A method is presented for the elastic analysis of shear diaphragms composed of standard light gage steel panels. A finite element approach is adopted, in which the mechanical properties of the diaphragm components are incorporated in an analytical model of the assemblage, using the direct stiffness method of matrix structural analysis. Results are compared against experimental values

Henri Temianka Correspondence; (nilson)

https://digitalcommons.chapman.edu/temianka_correspondence/2531/thumbnail.jp

Time Spent in Home Care Tasks Related to Ownership and Uses of Home Care Equipment

The data for this research were taken from Utah\u27s contribution to the regional research project An Interstate Comparison of Urban/Rural Families\u27 Time Use. Data were collected between May 1977 and August 1978 from 210 two-parent/ two-child families. This thesis research studied the relationship between ownership and use of nine selected household appliances and time spent on the related housekeeping tasks for 208 of the families studied. Statistical analysis was done using t-tests for comparisons of time spent on the related task by owners and non-owners of each appliance. Analysis of variance was used to compare time spent on combined activities with ownership of differing numbers of appliances . The relationship between frequency of use and time spent on tasks was measured us ing the Pearson Product Moment correlation. The hypotheses tested were: 1. Ownership of home care equipment is not related to the amount of time spent in home care tasks. 2. Reported use of home care equipment is not related to the amount of time spent in home care tasks. Hypothesis Number 1 was accepted for all relationships tested with the exception of the dishwasher and time spent in dishwashing and the sewing machine and time spent in construction of clothing and household linens. The results indicated that the homemakers who owned a dishwasher spent less time in dishwashing than did non-owners. This was not true of the spouses, who spent very little time in dishwashing under either circumstance. The homemakers who owned a sewing machine spent considerably more time in construction of clothing and household linens than non-owners. When families were grouped by the number of appliances owned , no statistically significant relationships were found to exist between the number of appliances owned and the total time spent in home care tasks. Generally, those who owned many or few of the appliances spent more time in home care activities than did owners of four or five of the appliances. Hypothesis Number 2 was rejected for the relationships between dishwasher use and spouse time spent in dishwashing, sewing machine use and homemaker time spent in construction of clothing and household linens and use of power yard equipment and time spent in maintenance of home, yard, car and pets. The number of times the dishwasher was reported to have been used was related to the amount of time spent in dishwashing by spouses although the time was very limited. The lime spent in clothing and household linen construction increased with the number of times the sewing machine was used. This relationship would have been expected. Those who used their power yard equipment more often spent more time in maintenance of home, yard, car and pets. This was true for both the borne makers and the spouses. The assumed relationship between appliance ownership and use and time spent on home care activities was not found to exist for most appliances. The time savings potential of appliances had not been realized. The time spent on most tasks did not differ significantly between owners and non-owners, or by the reported number of times used

Non-linear finite element analysis of light gage steel shear diaphragms

SUMMARY Shear diaphragm action of properly designed light gage steel panels used for floors, roofs, and walls in steel buildings increase the stiffness and strength of such buildings. Considerable savings in weight and cost can be realized if full account of this action is taken in design. To make good use of the diaphragm action, detailed knowledge on diaphragm response to loading is essential. An efficient computer program has been prepared to analyze light gage steel shear diaphragm behavior in the linear and nonlinear ranges of response, up to collapse. The program uses figinite element concepts for analysis, and has routines to deal with the beams, purlins, panels, and connections. Beams and purlins are modeled by conventional flexural elements with three degrees of freedom at each node. Panels are represented by rectangular orthotropic plane-stress plate elements. Two different models for corrugated panels are proposed. One model makes use of an average effective shear modulus along the entire panel length, while in the other two different shear moduli are attributed to the end and central regions of the panel. The connections are modeled by spring elements, and, according to location, several different models utilizing these spring elements are used. The non-linear analysis is based on experimental evidence that, in general, the connections are the only important source of non-linearity up to collapse. For this reason, only the connection behavior is represented by a non-linear function. All other components of the diaphragm assembly are assumed to remain elastic throughout the loading range. The connectors can be either welds, used for heavily-stressed shear diaphragms, or screw fasteners, used for more lightly loaded installations. In both cases, the non-linear force-displacement relation used for the connection is a multi-linear approximation of the load-displacement curve obtained from a shear test of the connection and the small region around it. The program uses a frontal routine for the solution of the stiffness equations. The non-linear analysis is done by the residual force method, which utilizes the original elastic stiffnexx matrix at every stage of the analysis, and which arrives at the correct solution for each load increment through an iterative procedure. A modified Aitken accelerator is used to speed the convergence. In order to reduce the task of preparing input data, a mesh generator has been written. This mesh generator requires only simple basic data for the generation of the complete finite element mesh, for most practical diaphragms. The computer program has been employed to analyze diaphragms for which test results are available. Both linear analyses up to the elastic limit, and non-linear analyses up to and beyond the elastic limit have been conducted. For three of the four diaphragms analyzed, very good agreement between numerical and experimental results have been obtained. For a standard corrugated diaphragm, numerical results in the non-linear range show a more flexible behavior than in test. Detailed analysis indicates that this is most probably due to unavailability of correct connection test data for use in analysis. The force distribution in the diaphragms, overall diaphragm deflections, and seam slips are found at different ranges of response. As a result of the analyses, it is confirmed that connection non-linearity is the most important factor in the nonlinear range of diaphragm response, differences in shear modulus being only of secondary importance. It is concluded that the computer program developed is an efficient and dependable tool for research and design

Analysis of light gage steel shear diaphragms

INTRODUCTION It has long been recognized by structural engineers, that light gage steel cladding floor and roof decking systems have a considerable stiffening and strengthening effect on building frameworks. The beneficial contribution of these diaphragm systems is most pronounced when the structure as a whole is subjected to loads which result in an in-plane shear action of the cladding. This occurs, for example, when the rigidity of a floor or roof diaphragm acting as a membrane is utilized to transmit lateral forces to stiff end walls. Another example of diaphragm action is found in pitched roof portal sheds under vertical and lateral loads. In such cases the membrane strength and rigidity of the cladding can be used to restrict the tendency of intermediate frames to sway, by transfering the load to end walls and resulting in substantial economy in the design of the frames. Specific utilization of the in-plane shear strength and stiffness of panelling was suggested more than 18 years ago, but unless this effect could be calculated in advance no practical use could be made. In order to take this contribution to stiffness and strength into account in engineering design, it was necessary to develop means for predicting the effective shear rigidity and ultimate strength in shear of the steel panel diaphragm. Because of the complexity of such diaphragm systems, up to now, engineers have relied upon tests of full-scale-panel assemblies, in which the performance of specific combinations of panels, marginal framing members and connections have been studied on a strictly ad hoc basis. While much has been learned using this approach, and valuable design information was obtained, no rational theory to describe and predict structural behavior has resulted. On the other hand, testing of large full scale diaphragm installations is expensive and time consuming, and tests results are applicable only to identical assembly using the same panels as tested, with directly equivalent fastening systems. The need for a general method of analysis is clear

Condensation pressures in small pores: An analytical model based on density functional theory

Adsorption and condensation are critical to many applications of porous materials including filtration, separation, and the storage of gases. Integral methods are used to derive an analytical expression describing fluid condensation pressures in slit pores bounded by parallel plane walls. To obtain this result, the governing equations of Density Functional Theory (DFT) are integrated across the pore width assuming that fluid densities within adsorbed layers are spatially uniform. The thickness, density, and energy of these layers are expressed as composite functions constructed from asymptotic limits applicable to small and large pores. By equating the total energy of the adsorbed layers to that of a liquid-full pore, the authors arrive at a closed-form expression for the condensation pressure in terms of the pore size, surface tension, and Lennard-Jones parameters of the adsorbent and adsorbate molecules. The resulting equation reduces to the Kelvin equation in the large-pore limit. It further reproduces the condensation pressures computed by means of the full DFT equations for all pore sizes in which phase transitions are abrupt. Finally, in the limit of extremely small pores, for which phase transitions may be smooth and continuous, this simple analytical expression provides a good approximation to the apparent condensation pressure indicated by the steepest portion of the adsorption isotherm computed via DFT

Going paperless in student nurse clinical work integrated learning

The development of student nurses’ knowledge and skills in the Murdoch University (MU) undergraduate Bachelor of Nursing (BN) course is assessed against the Nursing and Midwifery Board of Australia [NMBA] (2016) Registered Nurse standards for practice, using the NMBA framework for assessing standards for practice (NMBA, 2015)..

Analysis of light gage steel shear diaphragms

INTRODUCTION: It has long been recognized by structural engineers, that light gage steel cladding floor and roof decking systems have a considerable stiffening and strengthening effect on building frameworks. The beneficial contribution of these diaphragm systems is most pronounced when the structure as a whole is subjected to loads which result in an in-plane shear action of the cladding. This occurs, for example, when the rigidity of a floor or roof diaphragm acting as a membrane is utilized to transmit lateral forces to stiff end walls. Another example of diaphragm action is found in pitched roof portal sheds under vertical and lateral loads. In such cases the membrane strength and rigidity of the cladding can be used to restrict the tendency of intermediate frames to sway, by transfering the load to end walls and resulting in substantial economy in the design of the frames. Specific utilization of the in-plane shear strength and stiffness of panelling was suggested more than 18 years ago, but unless this effect could be calculated in advance no practical use could be made. In order to take this contribution to stiffness and strength into account in engineering design, it was necessary to develop means for predicting the effective shear rigidity and ultimate strength in shear of the steel panel diaphragm. Because of the complexity of such diaphragm systems, up to now, engineers have relied upon tests of full-scale-panel assemblies, in which the performance of specific combinations of panels, marginal framing members and connections have been studied on a strictly ad hoc basis. While much has been learned using this approach, and valuable design information was obtained, no rational theory to describe and predict structural behavior has resulted. On the other hand, testing of large full scale diaphragm installations is expensive and time consuming, and tests results are applicable only to identical assembly using the same panels as tested, with directly equivalent fastening systems. The need for a general method of analysis is clear

The Role of RNA Polymerase II Elongation Control in HIV-1 Gene Expression, Replication, and Latency

HIV-1 usurps the RNA polymerase II elongation control machinery to regulate the expression of its genome during lytic and latent viral stages. After integration into the host genome, the HIV promoter within the long terminal repeat (LTR) is subject to potent downregulation in a postinitiation step of transcription. Once produced, the viral protein Tat commandeers the positive transcription elongation factor, P-TEFb, and brings it to the engaged RNA polymerase II (Pol II), leading to the production of viral proteins and genomic RNA. HIV can also enter a latent phase during which factors that regulate Pol II elongation may play a role in keeping the virus silent. HIV, the causative agent of AIDS, is a worldwide health concern. It is hoped that knowledge of the mechanisms regulating the expression of the HIV genome will lead to treatments and ultimately a cure