FACULTY OF TECHNOLOGY
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Item CAUSES OF ROOF FAILURE AND MODELLING OF PITCHED ROOF BLOW -OFF IN SOUTHWESTERN NIGERIA(2011-08) ADESOGAN, SUNDAY OLUFEMIThe increasing incidences of roof failures especially blow-off in recent times in Southwestern Nigeria has become worrisome in view of the damage done to adjacent structures and danger posed to building occupants and owners. There is the urgent need to devise methods to curtail failures and minimize the incidences of blow-off. This study was designed to investigate the causes and patterns of roof failures, recommend curtailment measures and develop a model to predict roof blow-off. Using purposive sampling technique, a survey of 3,780 roofs spread across Ekiti (450), Lagos (450), Ondo (360), Ogun (570), Osun (780) and Oyo (1,170) states was undertaken to establish the causes and patterns of roof failure. During the survey, timber samples at the point of roof construction (780), and those from failed (2000) and unaffected roofs (1000) were collected for moisture content determination in accordance with American Standard for Testing Materials (ASTM) D442 while the common nails used in construction were subjected to corrosion test in accordance with ASTM 1977. The integrity of nail joints was tested in accordance with ASTM 1761. Physical measurements of attic space and ambient temperatures, roof slopes, building dimensions and orientation were taken and combined with topography and courtyard effect to develop aerodynamic model to predict roof blow-off. The model was validated using post-model survey captured data. Data were analysed using descriptive statistics and regression analysis. Causes of roof failures included poor workmanship (30.5%), materials inadequacies (18.6%), design errors (14.8%), roof geometry (14.0%), topographical location (11.8%), age and environment (10.3%). Timber‟s moisture contents were 12.0% to 24.0% during construction. Natural seasoning of these moisture contents to 7.0% in service, induced stresses on roof members. Temperature fluctuations between 20.0oC and 40.0oC promoted moisture condensation and dimensional changes in roofs‟ wooden members. Poorly fitted joints reduced joint load from 103.1 ± 8.3 kg to 82.6 ± 5.1 kg. Nail diameter reduced from 21 ± 0.2 mm to 14.7 ± 0.3 mm within 90 days of exposure to water indicating potential reduction in joint strength. Blow-off occurred when ≤ 0; where MR and MO are resisting and overturning moments respectively. The model revealed that while gable roof could be adequate at the plain, hip roof with pitch angle between 40o and 60o would be appropriate on 5o and 10o slope hills respectively, with coefficient of multiple regression of 0.91 (p < 0.05). The model also revealed that optimum UNIVERSITY OF IBADAN LIBRARY xviii pitch angle was 55o and presence of courtyard reduced the wake and drag effects on roof. There were no statistical differences between the roof blow-off model predictions and post model survey data. The overturning moments for the rest were also greater than the resisting moment but they did not experience blow-off because of adequate anchorage of the sill. Roof failures in Southwestern Nigeria were caused by weakened joints resulting from corroded nails, interface gaps and wind effect. Remedial measures could include appropriate building orientation, proper anchorage, high pitch and adequate openings. Keywords: Roof failure, Blow-off, Pitched Roof, Modeling, Southwestern Nigeria Word Count: 497 wordsItem Finite element modeling of variable membrane thickness for field fabricated spherical (LNG) pressure vessel(Scientific Research, 2013-05) Adeyefa, O.; Oluwole, O. O.This study investigated thickness requirements for field fabricated (large) spherical liquefied natural gas (LNG) pressure vessels using the finite element method. In the FEM modeling, 3-dimenisonal analysis was used to determine thickness requirements at different sections of a 5-m radius spherical vessels based on the allowable stress of the material as given in ASME Section II Part D. Shallow triangular element based on shallow shell formation was employed using area coordinate system which had been proved better than the global coordinate system in an earlier work of the authors applied to shop built vessels. This element has five degrees of freedom at each corner node-five of which are the essential external degrees of freedom excluding nodal degree of freedom associated with in plane shell rotation. Set of equations resulting from Finite Element Analysis were solved with computer programme code written in FORTRAN 90 while the thickness requirements of each section of spherical pressure vessels subjected to different loading conditions were determined. The results showed membrane thickness decreasing from the base upwards for LNG vessels but constant thickness for compressed gas vessels. The obtained results were validated using values obtained from ASME Section VIII Part UG. The results showed no significant difference (P > 0.05) with values obtained through ASME Section VIII Part UG.Item Finite element modeling of heat transfer in salt bath furnaces(2009) Oluwole, O. O.; Atanda, P. O.; Imasogie, B. I."Heat flow patterns in two salt bath furnaces were studied in this work using finite element(FE) analysis. The implications of the heat flows on long term stability of furnace performance were evaluated. One design had a purely silica brick back-up after the embedded heating element with asbestos and glass-wool fiber insulation just before the outer steel shell. The other had an additional air-gap insulation formed by cylindrical steel belts with spacers placed after the silica back-up. It was observed that the design with additional air-gap insulation had tremendous insulation effect, necessitating a drastic thinning down of the silica brick thickness and glass wool fiber. "Item Engineering research for self-reliance-modeling and simulation perspective(2009) Oluwole, O. O."Engineering research is a sine-qua-non for development of new products, new production processes, hence production lines in the quest for self reliance in any economy. Modeling and simulation is a veritable tool for such research and development. This paper presents the multifaceted use of modeling and simulation as decision tools for engineering facet of an economy drawing examples from two different engineering disciplines- Metallurgical and Civil. "Item CAUSES OF ROOF FAILURE AND MODELLING OF PITCHED ROOF BLOW -OFF IN SOUTHWESTERN NIGERIA(2011-08) ADESOGAN, S. O.The increasing incidences of roof failures especially blow-off in recent times in Southwestern Nigeria has become worrisome in view of the damage done to adjacent structures and danger posed to building occupants and owners. There is the urgent need to devise methods to curtail failures and minimize the incidences of blow-off. This study was designed to investigate the causes and patterns of roof failures, recommend curtailment measures and develop a model to predict roof blow-off. Using purposive sampling technique, a survey of 3,780 roofs spread across Ekiti (450), Lagos (450), Ondo (360), Ogun (570), Osun (780) and Oyo (1,170) states was undertaken to establish the causes and patterns of roof failure. During the survey, timber samples at the point of roof construction (780), and those from failed (2000) and unaffected roofs (1000) were collected for moisture content determination in accordance with American Standard for Testing Materials (ASTM) D442 while the common nails used in construction were subjected to corrosion test in accordance with ASTM 1977. The integrity of nail joints was tested in accordance with ASTM 1761. Physical measurements of attic space and ambient temperatures, roof slopes, building dimensions and orientation were taken and combined with topography and courtyard effect to develop aerodynamic model to predict roof blow-off. The model was validated using post-model survey captured data. Data were analysed using descriptive statistics and regression analysis. Causes of roof failures included poor workmanship (30.5%), materials inadequacies (18.6%), design errors (14.8%), roof geometry (14.0%), topographical location (11.8%), age and environment (10.3%). Timber’s moisture contents were 12.0% to 24.0% during construction. Natural seasoning of these moisture contents to 7.0% in service, induced stresses on roof members. Temperature fluctuations between 20.0oC and 40.0oC promoted moisture condensation and dimensional changes in roofs’ wooden members. Poorly fitted joints reduced joint load from 103.1 ± 8.3 kg to 82.6 ± 5.1 kg. Nail diameter reduced from 21 ± 0.2 mm to 14.7 ± 0.3 mm within 90 days of exposure to water indicating potential reduction in joint strength. Blow-off occurred when ≤ 0; where MR and MO are resisting and overturning moments respectively. The model revealed that while gable roof could be adequate at the plain, hip roof with pitch angle between 40o and 60o would be appropriate on 5o and 10o slope hills respectively, with coefficient of multiple regression of 0.91 (p < 0.05). The model also revealed that optimum pitch angle was 55o and presence of courtyard reduced the wake and drag effects on roof. There were no statistical differences between the roof blow-off model predictions and post model survey data. The overturning moments for the rest were also greater than the resisting moment but they did not experience blow-off because of adequate anchorage of the sill. Roof failures in Southwestern Nigeria were caused by weakened joints resulting from corroded nails, interface gaps and wind effect. Remedial measures could include appropriate building orientation, proper anchorage, high pitch and adequate openings.