Civil Engineering Dimension (E-Journal)
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Contractors Perceptions of Effects of Project Overhead Costs on Building Project Performance in South-South of Nigeria
Get PDFThis study assesses 12 types of project overhead costs, 6 methods of allocation and 15 factors which affect project overhead costs in South-South of Nigeria. The objective is to compare small and medium contractors’ perception of the methods of allocation, factors affecting project overhead costs and the effect of the types of project overhead costs on cost, time and quality of the projects. Data were obtained through 501 structured questionnaires administered to small and medium contractors and analysed using mean item score, and Mann-Whitney U test. The results reveal that contractors perceive that supervision costs, cost of rework, equipment management costs, general field expenses, and temporary works costs were prominent overheads affecting cost, time, and quality performance of projects. There is no difference in the contractors’ perceptions of issues affecting overhead costs. It is recommended that contractors should give adequate priority to significant project overheads and their influencing factors
Motorcycle in the West Java Province, Indonesia: Its Growth and Characteristics
Get PDFMotorcycle provides several positive aspects in providing mobility, but its rapid increase in ownership and usage should be anticipated. The West Java Province has the highest number of population in Indonesia, which is potential to have the highest number of motorcycle. This study aims to develop a prediction model of motorcycle number and to develop a model of motorcycle ownership. Two models are proposed to predict the motorcycle growth in West Java, with gross regional domestic product and number of population as the independent variables. Four ordered probit models are proposed to explain motorcycle ownership in Bandung City based on economic, personal, user’s travel behavior, and motorcycle characteristics. This study explains that the increase of motorcycle ownership was not influenced by economic condition only, but also by travel behavior and their activity. Thus, besides economic aspects, the anticipation should also be based on travel and activity changes of the user
Influence of Inorganic Salts on Soils Liquid and Plastic Limits
Get PDFThis study focused on the influence of inorganic salts on soil liquid limit (LL) and plastic limit (PL). Sodium chloride, NaCl, potassium nitrate KNO3 and calcium sulphate, CaSO4 of various concentrations were added to two subsoils. Their liquid and plastic limits before and after contamination were monitored. Soil cation exchange capacity (CEC), exchangeable cations (sodium, Na+, potassium, K+, and calcium, Ca2+) and exchangeable anions (chloride, Cl-, nitrate, NO3, and sulphate, SO42-) were determined. A set of equations for predicting LL and PL, (with R2 = 0.908 to 0.990) at different levels of chemical interaction with time was developed using multiple regression analysis model. The results showed that both NaCl and KNO3 brought about reduction in LL and PL while CaSO4 addition led to increment in LL and PL. The predictive equations revealed that there is high tendency for the contaminated soils to regain their uncontaminated LL and PL values with time
Experimental Investigations of Effect of Sulphur on Beach Sand–Fly Ash–Asphalt (S-F-A) Paving Mixes
Get PDFThe main components of the flexible pavements are asphalt and aggregates. But in most of the places in India there is shortage of the good quality aggregates (especially coarse aggregates), at the same time beach sand is available in plenty in many regions. Due to relative abundance of beach sand, the studies on the utilities of the beach sand in paving mixes are worth taking up. But beach Sand-Asphalt mix alone is not suitable for pavement construction, because of its low stability and high air voids. In the present study, Sand-Fly ash-Asphalt-Sulphur (S-F-A-S) mixes are being made in different proportions and tested for their properties. Fatigue strength, stability, water sensitivity, stiffness modulus and dynamic modulus tests are carried out at standard test conditions and the results are analyzed for drawing conclusions. This study investigates the potential use of abundant ingredients, which may replace the ones which are scarce in nature
The Optimization Model of Runway and Gate Assignment
Get PDFThis paper is aimed to develop the optimization model of time slot utilization for both runway and apron gate of airport system. The model considers the objectives of airline company to minimize flight-taxiing-time and waiting-time for both landing and take-off. The optimization makes use of Network Representation (NR) in the form of two bipartite networks in order to transform the problem of runway and apron gate assignment into the network flow problem. Maximum Matching and Minimum Cost Flow on NR are the core of the model. An illustrative example is presented. The result shows that the model could increase both runway and apron gate capacities to as close as their theoretical capacities. Compared to the common practice which concerns only; the nearest available runway slot time, behind the scheduled time, and the nearest location of available gates to serve the flight, the model could reduce the total taxiing and waiting time
Client and Contractor Organisations’ Assessment of Design-Bid-Build Procurement Practice in Nigeria
Get PDFThis study sought to investigate the assessment of client and contractor organizations on the use of the design-bid-build method for project delivery in Nigeria. One hundred fifty seven questionnaires were administered purposively on contracting and client organizations in Nigeria. Sixty seven organisations responded to the questionnaire. The responses were analysed through the use of descriptive and inferential statistical tools. Of the twenty issues used for the assessment, ‘individual participants are exploitative of loopholes in contract documents’ ranked first on aggregation for the two groups. ‘Relationships among participants breed mistrust’ ranked least. On the average, contractors and clients disagree with the twenty issues or criticisms about the traditional procurement practice. The results of the analysis further indicate that there are no significant differences in perceptions on the issues between the two groups. It is recommended that the homogeneity of perceptions can be a launching pad for further investigation and intervention efforts for procurement improvement in Nigeria
Performance of Periwinkle Shell Ash Blended Cement Concrete Exposed to Magnesium Sulphate
Get PDFThe study examined the compressive strength of periwinkle shell ash (PSA) blended cement concrete in magnesium sulphate medium. Specimens were prepared from designed characteristics strength of 25 MPa. The cement replacement with PSA ranged between 0 and 40% by volume. A total of 180 cube specimens were cast and cured in water. At 28 days curing, 45 specimens each were transferred into magnesium sulphate of 1%, 3%, and 5% solution, while others were continuously cured in water and tested at 62, 92, and 152 days. The results revealed a higher loss in compressive strength with the control mix, and that it increases with increased in MgSO4 concentration and exposure period, whereas, the attack on the PSA blended cement concrete was less and the least value recorded by 10% PSA content. Therefore, the study concluded that the optimum percentage replacement of cement with 10% PSA could mitigate magnesium sulphate attack
Influence of Rainfall Patterns on the Instability of Slopes
Get PDFThe assessment of rainstorm-induced shallow landslides is still a research topic of wide concern for scientists and engineers. This paper examined the effect of rainfall intensity distribution on shallow landslides. Four synthetic rainfall distributions comprising uniformed, delayed, centralized, and advanced, were selected to examine the effect of rainstorm patterns on slope failure. The infiltration was modeled using Green-Ampt equation, while an infinite slope was selected to model the shallow landslide. Monte Carlo Simulation was applied to analyze the failure probability of the slopes. Two landslide cases were selected to examine the proposed model. The results indicated that among the four representative rainstorm patterns, the advanced rainfall pattern caused worst slope stability. The advanced rainfall pattern resulted in the shortest rainfall duration threshold for landslide occurrence, followed by the central, uniform, and then delayed rainfall pattern. The probabilistic analysis method was suitable to estimate the time of failure for the evaluated landslide cases
Compressive Strength Prediction of Square Concrete Columns Retrofitted with External Steel Collars
Get PDFTransverse confining stress in concrete members, commonly provided by transverse reinforcement, has been recognized to enhance strength and ductility. Nowadays, the confining method has been further developed to external confinement approach. This type of confinement can be used for retrofitting existing concrete columns. Many external confining techniques have been proven to be successful in retrofitting circular columns. However, for square or rectangular columns, providing effective confining stress by external retrofitting method is not a simple task due to high stress concentration at column’s corners. This paper proposes an analytical model to predict the peak strength of square concrete columns confined by external steel collars. Comparison with the experimental results showed that the model can predict the peak strength reasonably well. However, it should be noted that relatively larger amount of steel is needed to achieve comparable column strength enhancement when it is compared with those of conve tional internally-confined columns
Evaluating Functional and Structural Condition Based Maintenances of Airfield Pavements
Get PDFThis study evaluates airfield pavements’ functional- and structural-condition to determine the most economical maintenance method. As a part of the analysis, Pavement Condition Index (PCI) for several runways, taxiways, and aprons has been determined by MicroPAVER. Structural evaluation of airport pavements has been performed by Falling Weight Deflectometer (FWD) test. Evaluation of Layer Moduli and Overlay Design (ELMOD) also determines the required overlay thickness based on the E-values, i.e. FWD data analysis. Damage analysis determines the time of repeated overlay application. In addition, functional parameters have been included to determine the time of functional maintenance. Maintenance and rehabilitation alternatives have been selected to develop different program strategies. Life Cycle Cost Analysis (LCCA) has been performed to determine the maintenance cost. Structural condition based maintenance cost is compared to functional condition based maintenance cost. Comparison shows that structural condition based approach yields cheaper maintenance strategies than functional condition based maintenance approach