Civil Engineering Dimension (E-Journal)
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Recycling Billet Scales as Fine Aggregate in Concrete Production
Get PDFBillet scales are by-products from steel rolling mills in Nigeria that presently constitute environmental pollution. This paper reports studies carried out using these solid wastes as a partial replacement for sand in the production of concrete. Various percentages of billet scales were used in a concrete mixture of 1: 2: 4 by weight to cast concrete specimens. The compressive and tensile strengths developed were tested after 7, 14, 21, and 28 days of curing. The result of the compressive and splitting tensile strengths tests indicated that concrete strength increased with curing age. The compressive strength of 0%, and 15% replacement of sand with billet scales as obtained at 28 days are 26.0N/mm2, 26.2N/mm2. 15% optimal replacement of sand with billet scales had similar results as the control mixture of 0%, which could be used in reinforced concrete structures. Other replacements could be useful as mass concrete for non-structural construction applications
Proposed Site-Specific Response Spectra for Surabaya-Madura Bridge
Get PDFThis paper presents a site-specific seismic hazard study to determine the recommended seismic design criteria for Suramadu Bridge. The study is performed using probabilistic seismic hazard approach to determine maximum acceleration and response spectra at bedrock and followed by local site effect analysis to determine maximum acceleration and response spectra at ground surface. The probabilistic seismic hazard analysis (PSHA) is carried out using 3-dimension (3-D) seismic source models (fault source model). Two hazard levels are analysed to represent 150 and 3,300 years return period of ground motion around site location. The local site effect analysis is performed using 1-dimension (1-D) shear wave propagation theory to obtain peak ground acceleration and response spectra at ground surface. Finally, the site-specific surface response spectra with 5 percent damping are developed based on the mean plus one standard deviation concept from the result of local site effect analysis
Fractional Critical Shear Stress at Incipient Motion in a Bimodal Sediment
Get PDFThe objective of this research was to examine and to quantify the stability of mixed grain sediment beds previously exposed to different time length of uniform antecedent flow hydrograph. The assessment of bed stability was carried out based on the observation of temporal pattern of eroded sediment during two identical stability tests with time varying flow and higher peak discharge. This was linked to the movement of individual sediment fractions to obtain fractional critical shear stress in a bimodal sediment mixture. The stability tests suggest a considerable increased in the stability of individual grain. Longer exposure time by antecedent flow clearly had an influence in the increasing stability of the bed. The increased rate of fractional critical shear stress during stability tests varied between 16 % and 35 % in the coarse mode whilst in the fine mode the rate of increase varied between 27 % and 39 %
CAPACITY FACTOR BASED COST MODELS FOR BUILDINGS OF VARIOUS FUNCTIONS
Get PDFThe desired accuracy level of an estimate heavily relies on the availability of data and information at the time of preparing the estimate. However, an estimate often must be made when data and information are not complete. At earlier stages of project implementation at which data and information are minimal, a client is often required to prepare a cost estimate. This paper discusses the capacity factor-based cost models for buildings with total areas serving as the proxy of capacity. A total of four cost models for different building functions are presented in this paper. Based on the models, most building functions with the exception of housings, exhibit decreasing return to scale, meaning that the unit measure of cost expressed by cost per square meter declines as the size of capacity increases. The cost models are then applied to estimate the development unit cost for different demographical unit measures
Review and Recommendation of Cold Asphalt Emulsion Mixtures Caems Design
Get PDFNote from the Editor
Cold Asphalt Emulsion Mixture (CAEM) is a mixture of aggregates and asphalt emulsion that is mixed at room temperature. It is relatively simple to produce, but the design procedure provided by the Asphalt Institute and the Ministry of Public Work of Indonesia pose some problems in its practical application. This Technical Note discusses limitations of the current design procedures and presents a simpler and more practicable design procedur
Evaluation Of Finite Element Mesh Arrangements And Stress Intensity Factor Calculation Methods For Opening Mode Fracture Of Cracked-Cemented Materials
Get PDFFracture mechanics is a branch of mechanics, which deals with the cracked body. Every construction material that currently in use inevitably is not flawless. The pre-existing crack may grow to cause structure failure due to low stress, which acts to a structure. Stress intensity factor (K) is a single parameter in fracture mechanics, which can be used to examine if a crack, would propagate in a cracked structure under particular loading condition. Finite element method is used to analyze the cracked body to provide the displacements data around the crack tip (at quarter point elements) due to load prescribed, for stress intensity factor determination. Two methods of stress intensity factor calculation, Quarter Point Displacement Technique (QPDT) and Displacement Correlation Technique (DCT), were evaluated. A series of standard fracture testing were undertaken to provide the fracture load data (Pf), which coupled with the stress intensity factor analytical formula to calculate fracture toughness. The results showed that under a particular mesh arrangement, the result of finite element analysis could deviate from the analytical formula calculation result. The QPDT method is suitable for compact tension specimen but DCT seemed to be not. For cracked beam analysis, the QPDT and DCT calculations were in good agreement with the analytical formula as long as coupled with the appropriate mesh arrangement around the crack tip
EFFECTS OF VARYING CURING AGE AND WATER/CEMENT RATIO ON THE ELASTIC PROPERTIES OF LATERIZED CONCRETE
Get PDFThis paper reports the results of investigations carried out on the effect of varying curing age and water/cement ratio on the modulus of elasticity and modulus of deformability of laterized concrete. The test specimens were made with sieved samples of selected grain size ranges of laterite used as fine aggregates to replace sand in normal concrete. Batching was by weight. Three mix ratios of (1:1½:3), (1:2:4) and (1:3:6) were used. Water/cement ratio of 0.5, 0.6, 0.7 and 0.75 were used for each of the mix ratios. The specimens were tested at curing ages of seven to 28 days. The results showed that there was a corresponding increase in both modulus of elasticity and modulus of deformability of laterized concrete due to increase in curing ages. The mix proportion, compressive strength and water/cement ratio were found to have significant effects on both modulus of elasticity and modulus of deformability of laterized concrete
PERFORMANCE EVALUATION OF ADVANCED TRAFFIC CONTROL SYSTEMS AT SIGNALISED INTERSECTIONS FAR FROM ADJACENT INTERSECTIONS
Get PDFAdvanced Traffic Control Systems (ATCS) have been recognised as one of the most direct methods for relieving urban traffic congestion. However, the applications of the systems in large cities in developing countries are unique because road networks in these cities face more severe transportation problems than those in developed countries. Furthermore, some of signalised intersections lie close, but others far from adjacent intersections. The aim of this paper is to evaluate the performance of ATCS at intersections with far distance to adjacent intersections and to recommend how to improve traffic performance with given constraints of severe transportation problems. Road network in Bandung, Indonesia was used as a case study. Microscopic traffic simulation was conducted to evaluate the performance of ATCS. It is shown that on average, traffic performance measures under Fixed Time traffic control system were similar or better than those under ATCS. In conclusion, the application of ATCS at intersections far from adjacent intersections is not effective
SEISMIC RISK ASSESSMENT OF LEVEES
Get PDFA seismic risk assessment procedure for earth embankments and levees is presented. The procedure consists of three major elements: (1) probability of ground motion at the site, (2) probability of levee failure given a level of ground motion has occurred and (3) expected loss resulting from the failure. This paper discusses the first two elements of the risk assessment. The third element, which includes economic losses and human casualty, will not be presented herein. The ground motions for risk assessment are developed using a probabilistic seismic hazard analysis. A two-dimensional finite element analysis is performed to estimate the dynamic responses of levee, and the probability of levee failure is calculated using the levee fragility curve. The overall objective of the assessment is to develop an analytical tool for assessing the failure risk and the effectiveness of various levee strengthening alternatives for risk reduction. An example of the procedure, as it applies to a levee built along the perimeter of an island for flood protection and water storage, is presented. Variations in earthquake ground motion and soil and water conditions at the site are incorporated in the risk assessment. The effects of liquefaction in the foundation soils are also considered
The Uniaxial Compressive Strength of Soft Rock
Get PDFSoft rock is a term that usually refers to a rock material with a uniaxial compressive strength (UCS) less than 20 MPa. This low strength range might be influenced by physical characteristics, such as size, saturation, weathering and mineral content. A number of uniaxial compression tests have been conducted onto soft rock samples. The results showed that the strength reduced significantly in saturation. The reduction was also caused by weathering, the strength of distinctly weathered rocks were lower than that of partially weathered rocks. In conjunction with the uniaxial compression test, point load strength index tests, IS(50), have also been conducted in order to obtain a correlation between the UCS and the point load strength index IS(50). The results showed that the IS(50) could well be correlated with the UCS. A conversion factor of 14 is proposed for soft rock materials