Assessment of Post Fire Structural Strengths of Normal Strength Concrete Subjected to Cyclic Thermal Loadings

Concrete is a composite construction material consisting basically of a binder, aggregates, water and with or without admixture to modify either or both its physical and chemical properties. The rate at which concrete structures especially buildings are gutted by fire hazards is on the increase and this has adverse effect on the strength, hence, the need to  assess the post fire structural strengths of Normal Strength Concrete(NSC). NSC of grade 50 was produced and cast into specimens of sizes 150mm cubes and 100mm x 100mm x 500mm reinforced concrete beams. The concrete cubes and beams were subjected to elevated cyclic thermal loadings after 7, 14 and 28 days of curing, while the rate of heating was maintained at 1oC/min until the target temperature of (100, 130, 160, 200 and 250)o C where attained and this was maintained for one hour and then allowed to cool at 1oC/min to room temperature of 32oC.         Unstressed Residual Uniaxial Compressive Test (URUCT and Flexural Strength Test (FST) were conducted on the cubes and reinforced concrete beams, respectively. Direct Tensile Strength Test (DTST) was performed on the high yield (460N/mm2) steel reinforcement. The result showed that the residual compressive strengths of concrete cubes decreases with increase thermal loadings. The expected strengths of 0.69 and 0.97 of the 28 days strength for 7 and 14 days respectively were met. The flexural strengths decrease with increase in thermal loadings. The flexural strength of the concrete beams at 28 days of 15.25N/mm2 at thermal loading of 32oC was reduced to 8.16/mm2 at thermal loading of 160oC; while the strength at 14 days of 12.19 N/mm2 at thermal loading of 32oC was reduced to 7.62N/mm2 at thermal loading of 160oC and finally, the strength at 7 days of 10.13N/mm2 at thermal loading of 32oC was reduced to 5.82N/mm2 at thermal loading of 160oC. All the results met the specification for high yield steel of 12% elongation at fracture. It was concluded that within the thermal loading range adopted, the tensile strength of the reinforcement was not impaired beyond the limit specified by the code. Keyword: Normal Strength Concrete, Thermal loadings, Unstressed Residual  Strength Test, Fire hazard

Assessment of Post Fire Structural Strengths of Normal Strength Concrete Subjected to Cyclic Thermal Loadings

Concrete is a composite construction material consisting basically of a binder, aggregates, water and with or without admixture to modify either or both its physical and chemical properties. The rate at which concrete structures especially buildings are gutted by fire hazards is on the increase and this has adverse effect on the strength, hence, the need to assess the post fire structural strengths of Normal Strength Concrete(NSC). NSC of grade 50 was produced and cast into specimens of sizes 150mm cubes and 100mm x 100mm x 500mm reinforced concrete beams. The concrete cubes and beams were subjected to elevated cyclic thermal loadings after 7, 14 and 28 days of curing, while the rate of heating was maintained at 1oC/min until the target temperature of (100, 130, 160, 200 and 250)o C where attained and this was maintained for one hour and then allowed to cool at 1oC/min to room temperature of 32oC. Unstressed Residual Uniaxial Compressive Test (URUCT and Flexural Strength Test (FST) were conducted on the cubes and reinforced concrete beams, respectively. Direct Tensile Strength Test (DTST) was performed on the high yield (460N/mm2) steel reinforcement. The result showed that the residual compressive strengths of concrete cubes decreases with increase thermal loadings. The expected strengths of 0.69 and 0.97 of the 28 days strength for 7 and 14 days respectively were met. The flexural strengths decrease with increase in thermal loadings. The flexural strength of the concrete beams at 28 days of 15.25N/mm2 at thermal loading of 32oC was reduced to 8.16/mm2 at thermal loading of 160oC; while the strength at 14 days of 12.19 N/mm2 at thermal loading of 32oC was reduced to 7.62N/mm2 at thermal loading of 160oC and finally, the strength at 7 days of 10.13N/mm2 at thermal loading of 32oC was reduced to 5.82N/mm2 at thermal loading of 160oC. All the results met the specification for high yield steel of 12% elongation at fracture. It was concluded that within the thermal loading range adopted, the tensile strength of the reinforcement was not impaired beyond the limit specified by the code

Trip pattern of low density residential area in semi urban industrial cluster: predictive modeling

This research elucidates the trip pattern of the low-density residential zone in a semi-urban industrial cluster of southwestern Nigeria. These sets of dwellers are often times neglected in the transportation planning process. To achieve the aim of this research, domiciliary information gathering procedure was employed with 0.82 return rates. It was backed up with the focus group discussion method. Data on frequency of trips, per capita trip, modal choice, and socioeconomic and demographic data were collected, collated, and analysed. Accordingly, a predictive model was formulated for the trip pattern of the low-density area. This was achieved with the aid of statistical software SPSS version 21.Consequently, the results of the multiple regression models showed that both monthly income and car ownership had a significant positive influence on the work trip while only car ownership positively influences non-work trip. R2 values of 0.729 and 0.739 were obtained for the descriptive model at 95% confidence level. This established the robustness of the model, the analysis showed that monthly income and car ownership had a significant positive influence on the work trip with an Rsquare value of 0.729 and 0.739 for work and non-work trip respectively. This indicated that household will embark on more trips with an increase in car ownership and monthly income. However, effective transportation planning and traffic infrastructural development were recommended to meet the demands of the increased number of trips daily