Indicate title,volume and number of article(s) required
Quote of the Day
Recent Blog Entries
D.E. Ewa, F.O. Okafor 408-417
Maturity method of estimating in-sit u strength of concrete has not been given serious attention as a quality control tool in the Nigerian construction industry. As a non-destructive test method, the maturity method was used in the study to estimate the time for strength development in concrete cured up to 56 days. Water-cement ratios adopted range from 0.44-0.57. Strength-Maturity-Age (SMA) curves were produced from nonlinear regression analysis performed on the experimental data set. The accuracy of these curves were evaluated by computing average absolute error (AAS), the error of estimate (EoE) and the average absolute error of estimate (Abs EoE) for each concrete mix. These were done based on the actual average experimental strengths to measure how close the predicted values are to the experimental data set. The absolute average error of estimate (Abs. EoE) recorded is within the ±10% tolerance zone for concrete works and the R2 values for each regression line were all greater than 0.95, this satisfies the recommendation of [ASTM C 1074 (2004)]. From the developed maturity curves, concrete maturities and time for strength development were estimated. The time to attain the characteristic strengths for C20, C25, C30 and, C35 concrete were 252 hours (10.5 days), 288 hours (12 days), 480 hours (20 days), 526 hours (21.9 days) and, 264 hours (11 days), 336 hours (14 days), 576 hours (24 days), 540 hours (22.5 days) for medium and high slump mixes respectively. These strengths were achieved in less than the 28-day period for removal of props recommended by the Nigerian General Specification for Roads and Bridges.
Keywords: Concrete; maturity; compressive strength; water-cement ratio; time
Vol. 4, No. 1, 2014
Reliability Design Format for Steel Plate Girder to BS 5950 (2000), pp 330-338
O. A. Ahmed and O. A. Uche
Abstract: The paper presents reliability assessment of deterministic design of steel plate girder considering both ultimate and serviceability limit state in accordance with BS 5950 (2000). The reliability analysis was carried out using First Order Reliability Method (FORM). Design variables such as strength of the material (Py), width of the flange, flange thickness, web thickness as well as the span of the girder were considered random and stochastic. It was shown among the findings that, when the span (L) of the plate girder was kept constant with increase in the magnitude of live-dead load ratio, the safety indices decreases, as deflection criterion was considered. Also, the design of the plate girder in accordance with BS 5950 considering shear and deflection is safe for almost all the range of variables considered. On varying the depth of the plate girder, safety indices increase with increase in depth and decrease with increase in live-dead load ratio, when shear criterion was considered. The deflection is the most critical mode of failure on varying the span and load ratio, with safety index less than the recommended value by JCSS 2000 for structural members with moderate to large consequences of failure of 3.3 to 4.4. Therefore, BS 5950 design result seems unsafe with respect to bending (under high live-dead load ratio) and satisfactory with respect to shear and deflection. It is then, recommended that the design of steel plate girder base on BS 5950 be reviewed to incorporate reliability analysis.
Keywords Reliability design, steel plate girder, safety index, deterministic design
An Empirical Assessment of Causes of Building Collapse in Lagos State, Nigeria, pp 344-352
O. G. Okeola A. A. Okeola and M. G. Ameen
Abstract: The unremitting cases of building collapses in Nigeria have become a source of national and international concern. Many efforts have been directed towards identifying the critical factors responsible for these collapses with the aim of finding appropriate strategies that is proactive and pragmatic in preventing further occurrences. One of the bottlenecks that have clog efforts to determine the causes of collapses is the absence of a comprehensive analysis of records of building collapses. This study gives an empirical assessment of causes of building collapse in an economic hub state of Nigeria by statistically analysing records of building collapses in Lagos state. The findings indicate poor quality materials and workmanship, faulty design/construction methodology and excessive loading as the major factors responsible for building collapses in Lagos state. Based on the findings recommendations to stem the tide in the short and long term were given.
Keywords: Building Collapse, Structural, workmanship, materials, Lagos
Click here to edit text
Vol. 5, No. 1, 2015
Investigation on the Level of Compliance of Sandcrete Blocks in Ibadan, 362-369
- A. Yahya
Abstract: Good design of sandcrete block as a load bearing element requires the provision of adequate effective area for intended load. One of the causes of poor quality sandcrete blocks is non-compliance to standard provisions in relation to adequate size, strength, and quality of structural elements. In this study the level of compliance on standard specification of sizes of sandcrete blocks, by makers of the product was investigated. It was assumed in this study that other quality assurance parameters, except size properties of sandcrete blocks are satisfactory. This study determines factor of safety for area of sandcrete block and recommend such, to validate the design factor of safety of load bearing wall, as specified in BS 8110 and other design codes in Nigeria. Samples of sandcrete blocks were taken from ten different block making industries located in different areas of Ibadan for this study. The sizes of Block samples were measured and their areas determined and compared with specifications by Standard organization of Nigerian in NIS 2007. Statistical analysis was carried out on the measured data and the results indicate that an area factor of safety of 0.94 and 1.19 are suitable for 150mm and 225mm sandcrete block respectively.
Keywords; Sandcrete blocks, compliance, factor of safety, size, effective area, specification
Optimization of Project Construction Management for Client Involvement in Nigeria, 370-379A. Adedeji, O. A. Lawal and O. I. Ojetade
Abstract: In order to optimize client involvement in the design stage of a project, the client has to increase their involvement with all the stake holders involve in the execution of a construction project. This is necessary since the more detailed clients definition of the scope of his project to the designers, the better the degree of pre planning and investigation, which will reduce the incidence of cost and time overrun of the project. The study has been conducted in two states on Nigeria, where designed questionnaires were administered to the party involved in construction. The study has shown that the client level of involvement stands at 45%, in the construction stage of a project. The construction phase of a project is where 2/3 of the bulk of expenses on a project is incurred, it is also at this stage of a project that cost and time overrun and poor quality of project is more pronounced owing largely to the improper implementation of project management practices by the contractors. Clients level of participation from the existing 45% to 74% would improve the output of a project. Project owners must be aware that the decisions that are made in the initial stages of planning and design are difficult and costly to change once construction begins, there is therefore the need for the owners to play active part in the various phases of a project particularly the design phase in order to ensure quality of project at a reduced cost and time. It is recommended that the client gives all relevant information required by the designers and make his brief concise in the design phase of a project to avoid significant problems which may arise in the successive stages of the project such as redesign and rebuild.
Keywords: client, construction, project, optimisation, genetic algorithms, excel solver
Structural Behaviour of Plastered Strawbale Reinforced with Chicken Wire and Diamond Lath under Compression Tests, 380-389
- M. Matanmi
Keywords, Diamond lath, chicken wire, compressive tests
Comparism of Physical Properties of Palm Kernel Shells and Conventional Light-weight Aggregates, 390-395
Abstract:The physical properties of palm kernel shells were compared with that of conventional light-weight aggregates used in lightweight concrete works to examine the light-weightiness of palm kernel shells relative to conventional light-weight aggregates. Results obtained from the physical properties tests were compared with specified range of standard values of the various characteristics of conventional normal and light-weight aggregates gotten from ASTM 127 and www.constructionZ.com. The results of the specific gravity, fineness modulus, average moisture content and aggregate crushing value of the palm kernel shells obtained were less than that of normal weight aggregate but within the specified range of values for light weight aggregates classifying palm kernel shells concrete as lightweight aggregate. The palm kernel shell has bulk density of 580kg/m3 and aggregate impact value of 16.19% which is an indication that palm kernel shells can conveniently be used for structural light weight constructions as light weight aggregate. The particle size distribution shows that palm kernel shell has a maximum grain size within the range 16.0mm and 17.0mm, although this is less than that of normal weight aggregates; Palm kernel shell can be used conveniently in light weight concrete works.
Keywords Physical properties, palm kernel shells, light-weight aggregates.
A Review on the Properties of Concrete incorporated with Waste Glass as a Substitute for Cement, 396-407
K L Okeke and A. A. Adedeji
Abstract: Researches have shown that it is possible to use recycled materials to replace some of the traditional mixture components in concrete products and produce a more sustainable building material. One common material that can be recycled and have the possibility of use in concrete applications is waste plain glass. Waste glass is not really a waste but a resource. Its use in the construction industry is gradually gaining some ground. Waste glass has diverse application in the industry such as a building materials, concrete ingredient and paving applications, in place of sand and other natural resources. When used in construction applications, waste glass must be pulverized to very fine particle size. Today many researches are ongoing into the use of Portland cement replacements, using many waste materials like pulverized fly ash (PFA) and ground granulated blast furnace slag (GGBS). Like PFA and GGBS, waste glass powder (GLP) is also used as a binder with partial replacement of cement which take some part of reaction at the time of hydration, also it is act as a filler material. The presence of silica in cement is the binding property for the concrete, the strength of the concrete mainly depends upon the binding property of cement. In glass silica is rich. Waste glass can be used as pozzolanic material in concrete production, and has demonstrated significant influence in improving the mechanical and durability properties of concrete as shown by the results of several researchers. Waste glass undergoes beneficial pozzolanic reactions in the concrete and could replace up to 30% of cement in some concrete mixes with satisfactory strength development. This paper presents an overview of the works carried out on the use of waste glass powder as partial replacement of cement concrete.
Keywords: Recycled material, waste glass, cement, concrete, concrete strength