Civil Engineering Dimension (E-Journal)
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An Appraisal of Project Procurement Methods in the Nigerian Construction Industry
Get PDFThe aim of every client at the beginning of any project is to have at the end of the day a quality structure delivered on time and within budget. However, researches have shown that in most cases this aim is not met. The aim of the study that formed the basis for this paper was to identify and assess procurement methods in use in the Nigerian construction industry and identify the factors that affect the choice of the variants under the traditional and the non-conventional procurement methods. Data were collected using well-structured questionnaires administered to professionals in Lagos metropolis. Data collected were analyzed using descriptive and inferential statistics. The study reveals that the variants of traditional method of contract procurement are the most adopted in project execution in Nigeria. In making choice of procurement method, the study reveals that project completion at estimated time ranks as the highest factor considered for traditional method, while quality assurance ranks highest with non-conventional method
Behavior of Reinforced Concrete Frames In-Filled with Lightweight Materials Under Seismic Loads
Get PDFThis paper presents an experimental and analytical research conducted to study the in-plane behavior of reinforced concrete (R/C) frames in-filled with lightweight materials. The tests were performed on two single bay, single story in-filled frame specimens with ½ scale models. One of the test specimens was in-filled with lightweight materials, i.e. autoclaved aerated concrete (AAC) blocks, and the other, used as the comparison, was in-filled with clay brick materials. The loading used in the tests was in the form of cyclic in-plane lateral loads, simulating earthquake forces. Behavior of the frame structures was evaluated through the observed strength and deformation characteristics, the measured hysteretic energy dissipation capacity and the measured ductility. The experimental results show that the R/C frame in-filled with AAC blocks exhibited better performance under in-plane lateral loads than that in-filled with conventional clay bricks. In the analytical work, the performance of some analytical models available in the literature was evaluated in simulating the experimental result
A Computer Modeling of Fracture Based Pull-Out of Nylon 600 Embedded in Cementitious Matrix
Get PDFThis paper reports the development of a computer model that represents a pull-out process of nylon 600 embedded in cementitious matrix. The model is based on fracture approach considering the Poisson’s effect and stable crack length. To back up the model four pull out tests of nylon 600 fiber, diameter 1.1 mm, with two fiber embedment lengths, 100 mm and 120 mm are done. The numerical approach is then compared to the experimental results. The computer model is built on Delphi 7 and named “Program Cabut-Serat Fraktur". This study shows that the computer model could represent the fracture phenomenon during the pull-out process
Influence of Plastic Waste Fibers on the Strength of Lime-Rice Husk Ash Stabilized Clay Soil
Get PDFA study has been undertaken to investigate the strength of stabilized clay-soil reinforced with randomly distributed discrete plastic waste fibers by carrying out unconfined compressive strength and tensile-split strength test. In this study, the clay soil was stabilized with lime and rice husk ash mixtures. The effect of the fiber length and content on the compressive and split tensile strength was investigated. The laboratory investigation results show that inclusion of the plastic waste fiber increased significantly both the unconfined compressive strength and tensile-split strength of the stabilized clay soil. The fiber length plays a significant contribution in increasing the soil strength. To contribute for any significant improvement on compression as well as tensile strength, the fiber length should be in range of 20 mm to 40 mm. Fiber reinforcements also reduced soil brittleness by providing smaller loss of post-peak strength
The Effects of Different Curing Methods on the Compressive Strength of Terracrete
Get PDFThis research evaluated the effects of different curing methods on the compressive strength of terracrete. Several tests that included sieve analysis were carried out on constituents of terracrete (granite and laterite) to determine their particle size distribution and performance criteria tests to determine compressive strength of terracrete cubes for 7 to 35 days of curing. Sand, foam-soaked, tank and open methods of curing were used and the study was carried out under controlled temperature. Sixty cubes of 100 × 100 × 100mm sized cubes were cast using a mix ratio of 1 part of cement, 1½ part of latrite, and 3 part of coarse aggregate (granite) proportioned by weight and water – cement ratio of 0.62. The result of the various compressive strengths of the cubes showed that out of the four curing methods, open method of curing was the best because the cubes gained the highest average compressive strength of 10.3N/mm2 by the 35th day
Comparative Study of Equivalent Manning Roughness Coefficient for Channel with Composite Roughness
Get PDFThis paper reviews the applicability of nine selected expressions in determining the equivalent value of the Manning coefficient of roughness. For this purpose, a prismatic 4m-long and 0.05m-wide trapezoidal-shape channel was constructed, namely the homogeneous channel and the composite channel. The homogeneous channel had the same surface lining, whereas the composite channel had two different surface linings. Four different lining materials were considered: plaster, small, medium, and large-sized aggregates. The homogeneous channel showed a reliable Manning coefficient prediction, provided that a uniform flow was achieved. The roughness of the composite channel can be predicted accurately by the nine expressions; the average was 0.96, with standard deviation of 11.13%. Out of the nine expressions, the expression that considers wet-perimeter as its main parameter showed the best estimate. The error was about 2% with standard deviation of 5.15%. This can be actually traced back to the limited width of the test channel, thereby increasing the role of wet perimeter
Seismic Progressive Collapse: Qualitative Point of View
Get PDFProgressive collapse is a catastrophic structural phenomenon that can occur because of human-made and natural hazards. In progressive collapse mechanism, a single local failure may cause a significant deformation which then may lead to collapse of a structure. The current practices in progressive collapse analysis and design method generally focus on preventing progressive collapse due to abnormal gravity and blast loads. Progressive collapse behaviour of structures due to earthquake loads has not received as much attention. This paper presents a brief overview of the current state-of-knowledge, insights, and issues related to progressive collapse behaviour of structures caused by earthquake loading
Wind Affected Density Current Profile in a Small Semi-Enclosed Water Body
Get PDFDensity current is a type of current that occurs when fluid flow enters a fluid body of different density. The density difference introduces stratification state that requires treatment in the parameterization of turbulence. Due to the geometric shape of location of this study, which is considerably small semi-enclosed water body, a Quasi-Equilibrium Turbulent Energy (QETE) model was selected. QETE was selected because of its convenient parameterization of wind induced breaking wave effect on turbulence. Two equations of the model, turbulence kinetic energy and turbulence macro length scale, were discretized and implemented into a three-dimensional hydrodynamic model. Application to density current simulation in the location of study was then carried out using the resulted model. To show how effective formulation of wind induced breaking wave effect would be, three parameterizations of turbulence were considered. They include QETE model with and without breaking wave effect boundary conditions (BC), and constant eddy viscosity turbulence parameterizations. It was clear from the simulation results that wind induced breaking-wave effect on the density current is quite significant