nigerian defence academy
journal of science and engineering (ajse)
A STUDY OF THE TENSILE AND COMPRESSIVE STRENGTHS OF JUTE FIBER REINFORCED CONCRETE
Yusuf Dada Amartey; BilkisuHassanSada and Eunice Folasade Adedibu
This research work was carried out to investigate the behaviour of concrete containing jute fiber of different weight fractions with different curing ages. Tests were carried out on both fresh concrete (slump and compaction factor test) and hardened concrete (compressive and split tensile tests) using different weight fractions of jute fiber at 0, 0.25, 0.5, 0.75, 1.00 and 1.5%; with different curing ages of 3, 7, 14, 21 and 28 days strength. By applying28days curing age strength parameter, the use of 0.5% weight fraction of jute fiber increased slightly the compressive strength of concrete by 10.2% while further increase in the fiber weight fraction reduced the compressive strength when compared with the control at 0%. There was a progressive increase in tensile strength of concrete with an increase in percentage of jute fiber. An average optimum tensile strength value of 68.13% was obtained with fiber content of 0.75%..
AN ASSESSMENT OF A COMPUTER BASED METHOD FOR THE MEASUREMENT OF THE AREA OF SIMPLE LEAVES
Gabriel A. Ajibade, Solomon J. Kazzah and Joseph Appah
The tedious and time consuming classical method of leaf area measurement involving counting of squares over shadowed by the outline of a leaf on graph sheets, was simplified through an Excel program that would accept measurements of the length and breadth of the leaf and convert them into Area of the appropriate component shapes such as triangles, rectangles, semi circles etc best fitting for the leaf and then sum them up to derive the total actual area of the leaf. Results from the computerized leaf area method when compared with that of the manual leaf area method revealed a nonsignificant difference (t = 0.724; 2.571.P>0.5 at 5 df) The computerized method was found to be more economical, saving nearly 61% of the time needed for the manual leaf area calculation. In both area measurement (CV= 87:81) and time taken (CV 40:38), the computerized procedure reflected a marginal advantage in the ability to distinguish peculiarities in the population sampled.
INVESTIGATION OF AGERATUM CONYZOIDES AQUEOUS EXTRACT AS INHIBITOR
FOR HYDROCHLORIC ACID CORROSION OF SX 316 STEEL
Adeyemi, O.O.; Olubomehin O.O and Bello, R.O
The inhibitive effect of the extract of Ageratum conyzoides on corrosion of SX 316 steel in HCl solution was determined using weight loss measurement and galvanostatic polarisation techniques. It was found that the presence of the plant extract reduces markedly the corrosion of steel in acid solution and inhibition efficiency ranged between 94.39 ? 99.15 %. The inhibition efficiency increases as the plant extract concentration was increased. The inhibitive effect of A. conyzoides extract (ACE) was discussed on the basis of adsorption of the components on the metal surface. Negative value of energy of adsorption indicates the spontaneity of the process.
Dynamic Response of Prestressed Tapered Timoshenko Beams to Uniform Partially Distributed Moving Loads
Hamzat Afe Isede and Jacob Abiodun Gbadeyan
The dynamics of a prestressed variable cross-section Timoshenko beam subjected to a moving partially distributed load is investigated. The Finite element method with Lagrange interpolation functions and reduced integration element were used to model the structure. The Newmark numerical method of integration was used to solve the resulting semi-discrete time dependent equations to obtain the desired responses. The effects of the prestress, moving load’s velocity, moving load’s length, and boundary conditions on the dynamic characteristic of the beams were investigated and the results presented graphically.
RELIABILITY ESTIMATE OF STRENGTH CHARACTERISTICS OF BLACK COTTON SOIL PAVEMENT SUB-BASE STABILIZED WITH LOCUST BEAN WASTE ASH AND CEMENT KILN DUST
K. J. Osinubi, G. Moses and J. E. Sani
Reliability estimates of strength characteristic values for compacted locust bean waste ash treated black cotton soil using cement kiln dust (CKD) as an activator for road sub-base material were generated from laboratory results for specimens compacted at the energy levels of British Standard Light (BSL), West African Standard (WAS) and British Standard Heavy (BSH). A Model was developed by incorporating data obtained from unconfined compressive strength (UCS) test obtained from the laboratory test to produce a predictive model. Data obtained were incorporated into a FORTRAN-based first-order reliability program to obtain reliability index values. Variable factors such as optimum moisture content (OMC), hydraulic modulus (HM), locust bean waste ash (LBWA) content, cement kiln dust (CKD) content, Di-calcium silicate (C2S), Tetra Calcium Alumino-Ferrite (C4AF), and maximum dry density (MDD) produced acceptable safety index value of 1.0 at the energy levels of WAS and BSH compactive effort and they were achieved at coefficient of variation (COV) ranges of 10-100%. Observed trends indicate that the CKD content, OMC and MDD is greatly influenced by the COV and therefore must be strictly controlled in CKD/LBWA treated black cotton soil for use as sub-base material in road pavements. Stochastically, WAS and BSH compactive efforts are the only energy levels that can be used to model the 7 days unconfined compressive strength of compacted CKD/LBWA treated black cotton soil for use as sub-base material in road pavement at the variable ranges of COV of 40-100% and 10-100% at WAS and BSH energy levels respectively.
NON-DERANGEMENTS IN ORIENTATION REVERSING MAPPINGS IN THE DIHEDRAL GROUP
EFFECT OF EMBEDDED BAR LENGTH ON THE PULL-OUT FORCE OF STEEL - CONCRETE BOND Ikponmwosa, E.E., Olonade K.A. and Abimbola O.O.
This paper investigated the effect of embedded bar length on the steel-concrete bond with a view to proposing a regression model to predict ultimate pull-out force. Concrete of mix proportion 1:2:4 (cement: sand: granite) was prepared using water-cement ratio of 0.5. Concrete cubes of sizes 150 mm were cast and cured in water for 7, 14, 21 and 28 days. Another set of concrete cubes of sizes 400 mm were cast and reinforcing steel bars were embedded up to 100, 200 and 300 mm depth at the centre of the cubes. Slump and compacting factor of the fresh concrete were determined, so also the compressive strength. The force required to pull out the bar from the concrete cube was measured at expiration of curing ages. The results showed that the concrete was of normal weight with 28-day compressive strength of 24.33 N/mm2. Pull-out tests showed that pull-out forces (initial and ultimate) increased with increase in embedded length of the bars, the pattern was that the initial pull-out force increases about 17 – 22% while the ultimate pull-out force increases by about 25-32% for every 100 mm increase in the bar length. Strength relationship between compressive strength and ultimate pull-out force was linear, but not proportional. A regression model was proposed to predict the ultimate pull-out force using the age of the concrete and the embedded length of the bar as variables.
MODIFICATION OF SOFTWARE CONSTRUCTIVE COST MODEL II (COCOMO II) TO SUITE NIGERIAN DEVELOPMENT ENVIRONMENT.
P. O. Odion and E. A. Onibere
ABSTRACTConstructive Cost Model II (COCOMO II) by Barry Boehm is a model that allows one to estimate the cost, effort, and duration, when planning a new software development activity. COCOMO II is the latest major extension to the original COCOMO model calibrated in 1981. It consists of three sub models called which are the applications composition, early design, and post-architecture design. One of the findings made was that 90% of software developers in Nigeria use non-parametric methods for software development estimation, which usually lead to under-budgeting or over-budgeting. The Visual Basic programming language was used to code the modified model, because of its graphical interfaces. Sample results show a minimal difference between what was obtained in COCOMO II and the new model in order to ascertain the accuracy of the derived model. The comparison shows that the new model is environmentally friendly and can be adopted in any environment with little modification.