Civil Engineering Dimension (E-Journal)
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Estimating the Distribution of Air Voids in Concrete
Get PDFChord length measurements are used to estimate the volumetric distribution of air voids within hardened concrete samples. The accuracy of the Linear-Traverse method is questionable because chord lengths do not directly represent the actual volumes of the air voids. Using computer simulation, randomly generated concrete samples were analyzed using the Linear-Traverse method to compute the distribution of air voids, the chord length gradation curve, the chord length-to-traverse ratio, and the air void volume gradation curve. The current chord-length approach significantly underestimated the air void content. A method that estimates that air void gradation curve from the chord length gradation curve is presented. The computer simulation results are supported by a conceptual analysis. To obtain the most accurate estimate of the air void content, computer analyses showed that at least 15 traverse lines should be regularly spaced on the concrete sample
Boundary Conditions for 2D Boussinesq-type Wave-Current Interaction Equations
Get PDFThis research focuses on the development of a set of two-dimensional boundary conditions for specific governing equations. The governing equations are existing Boussinesqtype equations which is capable of simulating wave-current interaction. The present boundary conditions consist of for waves only case and for currents only case. To simulate wave-current interaction, the two kinds of the present boundary conditions are then combined. A numerical model based on both the existing governing equations and the present boundary conditions is applied to simulation of currents only and of wave-current interaction propagating over a basin with a submerged shoal. The results of the numerical model show that the present boundary conditions go well with the existing Boussinesq-type wave-current interaction equations
Effect of Specimen Size on the Tensile Strength Behavior of the Plastic Waste Fiber Reinforced Soil – Lime – Rice Husk Ash Mixtures
Get PDFImprovement of tensile strength in fiber reinforced soil is an important research topic. A study has been undertaken to investigate the strength of stabilized clay-soil reinforced with randomly distributed discrete plastic waste fibers by carrying out split tensile strength test. In this study, the clay soil was stabilized with lime and rice husk ash mixtures. The main purpose of this research is to investigate the effect of specimen size to the tensile strength behavior. Testing procedure was formulated using extended ASTM C496 standard. The laboratory investigation results showed that split-tensile strength of reinforced specimens increased with increase in size. The limitations of the dataset indicate that specimen size of 70 mm in diameter is the threshold to produce reasonable representative strengths
CPT-Based Interpretation of Pile Load Tests in Clay-Silt Soil
Get PDFTwo pile axial load tests were performed in a site in Depok, West Java. The soil of the site is predominantly a silt-clay soil, characterized by seven mechanical cone penetration tests (CPTs). The piles were 5.5 m long and 11.5 m long, 250 mm square piles. The results of the static load tests showed that the ultimate capacities were achieved. The axial load tests were subsequently back-analyzed using an axisymmetric finite element model using PLAXIS. In the back-analyses, the soil modulus and shear strength in the model, using the cone penetration resistance as the reference, were adjusted so that the numerical load-settlement curves matched the actual curves. The results of the back-analyses are then synthesized with the results of the CPTs, and are compared with available design guidelines. Some recommendations are then proposed
The Influence of Rock Properties and Size into Strength Criteria: A Proposed Criterion for Soft Rock Masses
Get PDFA new modified strength criterion for soft rock masses is proposed in this paper in order to provide a suitable estimation for soft rock mass strength. The new criterion is based upon the current compression test data of soft materials of over 150 samples, and available published data of soft rock strength. It is shown that the proposed criterion estimates reasonable values of soft rock mass strength. Rock properties and size contribute significantly into the strength, represented by friction angle and unconfined compressive strength. Examples exercised reveal that the structure of soft rock masses takes a dominant part in controlling the strength, which then determines the modelled strength of soft rock masses. The results also show that the strength of the proposed equation could relatively be higher three times than the strength of the Hoek-Brown criterion for a massive soft rock mass
Analysis of Journey to Work Travel Behavior by Car and Bus in the Sydney Metropolitan Region
Get PDFCar dependence is a fundamental problem in the sustainability of cities with low-density suburban sprawl. Increasing the use of public transport is one of the policy objectives commonly adopted to overcome this problem. It is essential to study journey to work travel behavior by car and bus. This paper applied preference function to analyze travel behavior and Moran’s I spatial statistic to evaluate the spatial association. The results indicated that the commuting preferences of residents have moved towards distance maximization. In general, bus was preferred for shorter distance trips whilst car was preferred for longer distance trips. Unlike car, by increasing distances from the Central Business District, residents tended to use bus for shorter distance trip. A significant positive spatial association was identified for both the slope preferences by car and bus where zones with a preference towards longer or shorter trips tended to travel to zones with similar preferences
Kriging-Based Timoshenko Beam Element for Static and Free Vibration Analyses
Get PDFAn enhancement of the finite element method using Kriging interpolation (K-FEM) has been recently proposed and applied to solve one- and two- dimensional linear elasticity problems. The key advantage of this innovative method is that the polynomial refinement can be performed without adding nodes or changing the element connectivity. This paper presents the development of the K-FEM for static and free vibration analyses of Timoshenko beams. The transverse displacement and the rotation of the beam are independently approximated using Kriging interpolation. For each element, the interpolation function is constructed from a set of nodes within a prescribed domain of influence comprising the element and its several layers of neighbouring elements. In an attempt to eliminate the shear locking, the selective-reduced integration technique is utilized. The developed beam element is tested to several static and free vibration problems. The results demonstrate the excellent performance of the developed element
Shear Response of Fibrous High Strength Concrete Beams without Web Reinforcement
Get PDFThe use of steel fibers to improve the mechanical properties of concrete has been the ongoing interest in the research work. This paper deals with one such improvement in the mechanical property of concrete, which is the shear strength. In this paper an attempt has been made to study the improvement of shear strength of high strength concrete beams (70 MPa) with different shear span to depth ratios (a/d = 1, 2, 3, and 4) and various dosages of fibers (0.4%, 0.8%, and 1.2% by volume of concrete), without shear reinforcement. The experimental work revealed that steel fiber volume has different influence at different shear span to depth ratios (a/d). The test results indicated an increase in the cracking shear resistance noticeably and ultimate shear strength moderately
Beam to Column Timber Joints with Pretensioned Bolts
Get PDFThe effects of pretension in bolts on hysteretic response of timber joints exposed to a bending had been reported by the authors, but the cyclic tests were carried out at small displacement level which might not be applicable for earthquake-resistance design. In this study, similar cyclic tests but at large displacement levels were conducted. Beam to column timber joints with steel side plates were fabricated and continuously loaded until failure. At connection, the bolts were pretension in four different magnitudes: 0 kN, 5 kN, 10 kN and 15 kN. The results showed that frictional action between the steel side plates and wood member as a result of bolt pretensioning significantly increased the (frictional) hysteretic damping and the equivalent viscous damping ratio. It is obvious from the test results that the pretension force in bolts has no influence on the maximum joint resistance but decreases the joint rotational deformation
Model Development of Rainwater Management for Agriculture Decision Support System in Semi Arid Area
Get PDFLand cultivation for agricultural purposes in semiarid area is usually carried out only once a year specifically during the rainy season. The condition is even worse since it is not without the risk of failure because of dry-spell or water-logging. To cope with this situation, the researchers developed a model of Rainwater Management for Agriculture Decision Supporting System (RMA-DSS). The objective of this RMA-DSS is to facilitate the decision making to build water infrastructure. Using this program it is hoped that sufficient water supply for specific crops with correct planting time can be guaranteed, which in turn will optimize harvest. The model consists of three parts, namely, rainfall-runoff-infiltration model, crop water requirement-irrigation-drainage model and rainwater management for agriculture model. The Models are designed using Microsoft Excel’s Macro Visual Basic and finalized with Visual Basic language program for operating spatial database of map object and non spatial database