Civil Engineering

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ANALYSIS OF PRE-CAST WAFFLE SLABS USING YIELD LINE AND RANKINE GRASHOFF THEORIES
(2012-09) AKINYELE, J. O.
Failure in pre-cast waffle slabs can be attributed to factors like analytical error, poor handling during transportation and placement which factors often lead to partial/total failure of slabs. The conventional method of analysing waffle slabs focuses on the ribs, while the slab portions at the top are avoided. This has led to under reinforcement and subsequent failure of the slab portions that are usually in direct contact with loads. In this study, a method that incorporates both the slab and rib portions in the analysis of pre-cast waffle slabs was therefore developed. Yield Line and Rankine Grashoff Theories (YLRGT) were combined for the analysis of pre-cast waffle slab. Six physical models of waffle slab were developed, each having five replicates, with the following dimensions: W1 (1353 x 430 x 58 mm), W2 (900 x 300 x 50 mm), W3 (1085 x 430 x 58 mm), W4 (407 x 364 x 50 mm), W5 (1312 x 300 x 58 mm) and W6 (860 x 360 x 50mm). Solid slabs of the same size and number designated S1, S2, S3, S4, S5 and S6 served as control. These models were validated using the slabs by testing for failure loads, deflections and crack width. Each slab was subjected to incremental load of 1.0 kN until failure occurred. Maximum bending moments were obtained for slab and rib portions using YLRGT, a finite element based method called ETABS was also used to analyse the slabs and results obtained were subjected to statistical analysis using ANOVA at p= 0.05. The YLRGT analysis of the various physical models (slab portion, transverse and longitudinal ribs) yielded the following bending moments: W1 (5526.0, 34.5, 918.3) Nm, W2 (1122.0, 279.2, 36.5) Nm, W3 (2880.0, 27.2, 619.9) Nm, W4 (590.0, 171.9, 160.9) Nm, W5 (947.0, 37.0, 4.4) Nm and W6 (1276.0, 90.4, 36.2) Nm respectively. The ETABS combined both slab and ribs giving W1 (4729.0) Nm, W2 (581.0) Nm, W3 (3338.0) Nm, W4 (733.0) Nm, W5 (851.0) Nm and W6 (686.0) Nm. Deflections at failure for waffle slab were smaller compared to solid slabs: (W1 = 1.19 and S1 =3.56) mm, (W2 = 3.64 and S2 =9.28) mm, (W3 = 3.90 and S3 =7.44) mm, (W5 = 8.17 and S5 =12.18) mm, (W6 = 3.29 and S6 =3.89) mm with the exception of W4 (6.60 mm) and S4 (6.44mm), where deflection of waffle slab was higher than that of solid slab. Mean deflection of S1 was significantly higher than W1, while S2 was significantly higher than W2. Average crack width for waffle (0.48 mm) and solid slabs (0.99 mm) were significantly different. High crack width in solid slab indicated lower shear strength. The Yield Line and Rankine Grashoff Theories have facilitated the accurate analysis of pre-cast waffle slabs by separating the slab and rib portions.
ANALYSIS OF PRE-CAST WAFFLE SLABS USING YIELD LINE AND RANKINE GASHOFF THEORIES
(2012-09) AKINYELE, J.o
Failure in pre-cast waffle slabs can be attributed to factors like analytical error, poor handling during transportation and placement which factors often lead to partial/total failure of slabs. The conventional method of analyzing waffle slabs focuses on the ribs, while the slab portions at the top are avoided. This has led to under reinforcement and subsequent failure of the slab portions that are usually in direct contact with loads. In this study, a method that incorporates both the slab and rib portions in the analysis of pre-cast waffle slabs was therefore developed. Yield Line and Rankine Grashoff Theories (YLRGT) were combined for the analysis of pre-cast waffle slab. Six physical models of waffle slab were developed, each having five replicates, with the following dimensions: W1 (1353 x 430 x 58 mm), W2 (900 x 300 x 50 mm), W3 (1085 x 430 x 58 mm), W4 (407 x 364 x 50 mm), W5 (1312 x 300 x 58 mm) and W6 (860 x 360 x 50mm). Solid slabs of the same size and number designated S1, S2, S3, S4, S5 and S6 served as control. These models were validated using the slabs by testing for failure loads, deflections and crack width. Each slab was subjected to incremental load of 1.0 kN until failure occurred. Maximum bending moments were obtained for slab and rib portions using YLRGT, a finite element based method called ETABS was also used to analyse the slabs and results obtained were subjected to statistical analysis using ANOVA at p= 0.05. The YLRGT analysis of the various physical models (slab portion, transverse and longitudinal ribs) yielded the following bending moments: W1 (5526.0, 34.5, 918.3) Nm, W2 (1122.0, 279.2, 36.5) Nm, W3 (2880.0, 27.2, 619.9) Nm, W4 (590.0, 171.9, 160.9) Nm, W5 (947.0, 37.0, 4.4) Nm and W6 (1276.0, 90.4, 36.2) Nm respectively. The ETABS combined both slab and ribs giving W1 (4729.0) Nm, W2 (581.0) Nm, W3 (3338.0) Nm, W4 (733.0) Nm, W5 (851.0) Nm and W6 (686.0) Nm. Deflections at failure for waffle slab were smaller compared to solid slabs: (W1 = 1.19 and S1 =3.56) mm, (W2 = 3.64 and S2 =9.28) mm, (W3 = 3.90 and S3 =7.44) mm, (W5 = 8.17 and S5 =12.18) mm, (W6 = 3.29 and S6 =3.89) mm with the exception of W4 (6.60 mm) and S4 (6.44mm), where deflection of waffle slab was higher than that of solid slab. Mean deflection of S1 was significantly higher than W1, while S2 was significantly higher than W2. Average crack width for waffle (0.48 mm) and solid slabs (0.99 mm) were significantly different. High crack width in solid slab indicated lower shear strength. The Yield Line and Rankine Grashoff Theories have facilitated the accurate analysis of pre-cast waffle slabs by separating the slab and rib portions.
ANALYSIS OF TRAFFIC FLOW ON SELECTED TWO-LANE HIGHWAYS IN IBADAN METROPOLIS
(2011-09) AKINTAYO, F.O.
Traffic congestion is a common feature on highways in many cities of theworld, including Ibadan, Nigeria. Previous studies have shown that several mathematical traffic flow models developed to analyse congestion cannot be easily generalised or adapted to varying situations. In addition, validation errors of some models are as high as 60.0 %. In pursuit of the objective of minimising traffic congestion in parts of the Ibadan metropolis, headway simulation models were developed for the analysis of flow on some selected two-lane highways characterised by heavy traffic. Traffic survey was conducted on three purposively selected heavily-trafficked two-lane highways (Total Garden-Agodi Gate, J Allen-Oke Bola and Odo Ona-Apata) in the Ibadan metropolis. Headway modelling approach incorporating the prevailing mroadway, traffic and control conditions was developed. Field data were captured on the three roads with a camcorder between 7.00 a.m. and 6.00 p.m. for a period of six months as specified in the Highway Capacity Manual. Comparison of the modelling result and field headway data were carried out using Kolmogorov-Smirnov (KS) test (p = 0.05). A traffic flow simulator was developed to simulate the different congestion scenarios by varying the minimum and maximum headways. Capacity analysis and validation of the results were carried out using ANOVA methods. Average vehicular flow of 715 ± 3, 970 ± 5 and 1118 ± 9 vph per lane on Total Garden-Agodi Gate, J Allen-Oke Bola and Odo Ona-Apata roads respectively. Eighteen hyperbolic headway scenarios were produced and the highest coefficient of correlation (R2 = 0.92) was recorded at 90 percentile while 0.18, 0.36, 0.50, 0.71, 0.82, and 0.79 were obtained at 1, 10, 30, 50, 70, and 100 percentiles respectively. There was no significant difference between theoretical and field data using Kolmogorov- Smirnov (KS) test (p < 0.05). Also, a total number of 171 congestion scenarios were generated using the traffic flow simulator. Traffic flow varied between 204 and 2376 pcu per lane while headways varied between 1 and 18 seconds. The capacity analysis produced approximated maximum flow rates of 1850, 2865 and 2881 pcu in the two directions of travel for Total Garden-Agodi Gate, J Allen-Oke Bola and Odo Ona- Apata roads respectively. The capacity of Total Garden-Agodi Gate was within the recommended maximum value of 2800 pcu in the two directions of travel for two-lane highways. The results for J Allen-Oke Bola and Odo Ona-Apata roads showed that an additional lane will be required in each direction of travel. The validation of the models on the dualised J Allen-Oke Bola road showed that congestion can be reduced by about 55.0 %. A maximum validation error of 35.0 % was obtained. The traffic flow simulator developed successfully simulated the traffic situations on the selected highways. The analysis of the flow yielded results that could ameliorate traffic congestion on the selected two-lane highways in the Ibadan metropolis.
ASSESSMENT OF CARBON DIOXIDE EXTRACTION IN A SOLID WASTE MANAGEMENT FACILITY, AKURE, NIGERIA
(2016-09) ELEMILE, O. O.
Carbon dioxide (CO2) emissions from solid wastes is a major contributor to the acceleration of global warming. In Nigeria, CO2 capture has been limited to the energy sector only. There is need to explore the reduction of CO2 emissions from solid wastes through appropriate technologies. This study, therefore was designed to assess CO2 extraction by adsorbents in a Municipal Solid Waste (MSW) management facility in Akure, Nigeria. An exploratory study design with an intervention component was adopted. For a year, wastes brought to the MSW facility from three locations viz: markets, residences and roadside, were characterised and quantified monthly. Chemical characteristics of the wastes were determined using standard methods. Carbon-dioxide emissions were estimated from the MSW composition using the Intergovernmental Panel on Climate Change tools. Air CO2 levels were monitored during the dry and wet seasons using a P-Sense Plus CO2 meter AZ-7755(PSPCM) and seasonal variations computed. A CO2 extractor which uses adsorbents consisting of Sawdust + Potassium Hydroxide (SKH), Sawdust + Sodium Hydroxide (SSH) and Sawdust + Calcium Hydroxide (SCH), all at ratio1:1, was designed and fabricated. The adsorbents were integrated into the equipment to capture CO2 from 5 kg samples of solid wastes burnt under controlled conditions with five replicates for each adsorbents during each test. The potential CO2 in the solid wastes was determined by ultimate analysis, while the concentration of CO2 adsorbed was obtained by finding the difference between the concentration of the CO2 at the inlet and outlet chambers of the extractor measured with the PSPCM. The effectiveness of the extractor combined with the adsorbents was determined by comparing the adsorbed CO2 with the potential CO2. Data were analysed using descriptive statistics and ANOVA at The mean monthly wastes generation from the three locations were 1,004,130.8+742,394.6 kg (biodegradable wastes), 1,322,831.0+810,634.9 kg (plastics) and 1,330,813.5+400,412.4 kg (paper). The mean values for the chemical constituents of these wastes for the three locations, residential, roadside and market respectively were Nitrogen 2.7+0.6, 2.1+0.8 and 3.4+0.7%; Phosphorus 0.10+0.03, 0.10+0.03 and 0.10+0.04% and Carbon 53.2+1.4, 53.1+1.8 and 53.1+1.5%, with no significant difference within the groups. The estimated CO2 emissions was 1.2 Gg/Yr. The ambient CO2 levels ranged between 438.0+7.2 and 630.0+124.5 ppm in the dry season, and 407.3+11.3 and 506.9+71.1 ppm for the wet season. The mean potential CO2 in the solid wastes was 160.0+ 42.0 ppm. The mean CO2 adsorbed were 99.0+24.0 ppm, 45.0+24.1 ppm and 30.0+13.0 ppm for SKH, SSH and SCH respectively. The effectiveness of SKH in the capture of CO2 was 61.9 % as against 20.8 % and 18.8 % by SSH and SCH, respectively. The selected adsorbents were effective in capturing carbon dioxide. Incorporation of Sawdust + Potassium Hydroxide improves the effectiveness of carbon dioxide extraction in the solid waste management facility.
EFFECT OF CRUDE OIL CONTAMINATED SAND ON THE ENGINEERING PROPERTIES OF CONCRETE
(2013-01) AJAGBE, W. O.
A considerable fraction of sand in Niger Delta Area of Nigeria is contaminated with crude oil. The contaminated sand is largely utilised by local contractors for the production of concrete. However, there is need to establish its suitability in concreting. Previous works have centered on hardened uncontaminated concrete in crude oil environment but not on concrete made with Crude Oil Contaminated Sand (COCS). This research was designed to evaluate the effect of COCS on some engineering properties of fresh and hardened COCS concrete. Levels of crude oil contamination were determined using gravimetry method of Total Petroleum Hydrocarbon (TPH) test on nine sand samples randomly collected from some oil spill sites in Rivers State. Based on the test results, seven types of artificially contaminated sand were prepared with crude oil levels of 0.0, 2.5, 5.0, 10.0, 15.0, 20.0 and 25.0%. Workability (slump, compacting factor and flow), compressive strength, linear shrinkage, water absorption, and fire resistance were determined using concrete cubes, flexural strength using concrete beams, and surface resistivity using concrete cylinders in accordance with standard methods. Data obtained were analysed using ANOVA at p = 0.05. Eight models were developed using historic response surface methodology to predict the engineering properties of COCS concrete at water-cement ratio (w/c) of 0.5. Also, COCS concrete design mixes with contamination level and w/c ratio suitable for reinforced concrete were formulated. The TPH varied from 8.6 ± 0.2 to 14.1 ± 1.3%. The workability of concrete was improved by the presence of COCS. Slump, compacting factor and flow of the fresh concrete increased with increase in contamination from 30.0 to 200.0 mm, 0.5 to 0.9 and 15.0 to 85.0%, respectively. Compressive strength, flexural strength, linear shrinkage and water absorption of the hardened concrete reduced with levels of contamination from 31.5 ± 2.3 to 3.5 ± 0.0 N/mm2, 5.9 ± 0.8 to 0.1 ± 0.0 N/mm2, 0.1 ± 0.0 to 0.0 cm and 0.2 to 0.0 kg respectively. At a temperature of 200.0˚C, the percentage strength reduction increased from 18.4 to 94.8% for 2.5 to 25.0% contamination. Surface resistivity ranged from 25.1 ± 0.2 to 32.3 ± 0.2 kΩ-cm. The compressive and flexural strengths of COCS concrete were reduced by more than 50.0% at crude oil contamination level greater than 10.0%. The water absorption and surface resistivity values indicated that COCS concrete exhibited greater resistance to water and chloride penetration respectively, it shrank less when compared with the uncontaminated concrete, but exhibited poor fire resistance. Coefficient of determination, R2, of the models developed ranged from 0.823 to 0.999. Concrete design mix ratio of 1part of cement to1.6 part of COCS (10.0% crude oil) to 2.4 part of coarse aggregate was found to be appropriate at 0.45 w/c. This mix gave minimum compressive strength of 21.0 N/mm2 which is acceptable for reinforced concrete structures. Concretes produced with sand contaminated with less than ten percent crude oil were found suitable for use in low strength structures. Mix re-design using lower w/c improved the strength of the concrete.
EFFECTS OF LEAD LEVELS ON INDOOR AND BUILT OYO STATE NIGERIA ENVIRONMENT IN IBADAN
(2014-08) ADEBAMOWO, E. O.
Environmental exposure to lead, a highly toxic heavy metal, is a significant cause of human morbidity and mortality. However, the determination of lead levels in homes and built environment have not been well investigated in Nigeria. This study was designed to evaluate the lead levels in dust, paint, paint chips, soil and water; and to ascertain the geotechnical properties of soil in the home environment in Ibadan. Four Focus Group Discussions (FGDs) were conducted and six hundred questionnaires randomly administered to evaluate knowledge about lead exposure in Ibadan. Responses were compared using Wilcoxon rank-sum tests for continuous variables and χ2 for categorical variables at p = 0.05. Lead levels in paint from twenty-five samples obtained from five manufacturers were measured. Three-hundred samples from urban areas were taken randomly from dust from door step of the house entrances and window sills, paint chips from walls, soil at 2000mm from fence wall and 300mm depth from front and back of the houses and portable water from taps and their lead levels measured. Atomic Absorption Spectroscopy was used to determine the lead levels in these samples. Geotechnical engineering tests were carried out to determine the Maximum Dry Density (MDD), Optimum Moisture Content (OMC), Liquid Limit (LL), Plastic Limit (PL), and California Bearing Ratio (CBR) of the sampled soil. Most respondents (86%) from the FGDs and the questionnaires (86%) had no knowledge about lead exposure in home environment. Twenty-four (96%) from the twenty-five paint samples exceeded the recommended lead level in paint of 90 ppm. Yellow paint had the highest lead level of 50,000 ppm; indicating high risk and white paint had the lowest lead level of 84 ppm. Dust lead levels from door steps of house entrances have average of 115.1 ± 1 12.9 ppm and dust lead levels from window sills have average of 83.3 ± 13.3 ppm; due to lack of proper regular cleaning. Paint chips lead levels from walls have average of 2,894.6 ± 79.5 ppm; due to flaking old paint that emits lead. Soil lead levels in front of houses have average of 135.3 ± 4.5 ppm and soil lead levels from back of the houses have average of 69.4 ± 5.9 ppm; due to lack of landscaping to cover exposed soil surfaces. Potable water lead levels have average of 0.21 ± 0.02 ppm, against recommended value of 0.01 ppm due to usage of lead water pipes. The values of the geotechnical parameters obtained ranged from 1.8 – 2.0 g/cm3 (MDD), 8.5 - 13.8% (OMC), 17.8 – 29.6% (LL), 14.2 – 23.4% (PL), and 59 - 95% (CBR); all within normal recommended values. The indoor and built environments in Ibadan are highly affected by high lead levels. Lead levels in paint used in homes should be reduced to minimize human morbidity and mortality. The usage of non-lead water pipes is highly recommended. Lead levels in soil in the home environment do not affect the geotechnical characteristics of soil.