Civil Engineering Dimension (E-Journal)
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An Assessment of Practicing Reflection in Teaching the Concepts for Engineering Statics
Get PDFThis paper shares the experience of Dr Ande in practicing reflection in teaching the concepts for Engineering Statics. His constant pursuit of being a reflective practitioner has made him more evolved as an effective teacher and made him more flexible in modifying his practice. It is interesting to learn from Dr. Ande experience
Consideration of Road Management from the View Points of Long- and Short-Distance Road User’s Satisfaction
Get PDFThis study observed long- and short-distance road user satisfaction with national road infrastructure in order to direct future road management strategies. The research was a quantitative research method using questionnaire translated into the Japanese Language. The questionnaires were distributed to 2000 road users of two national roads in Saga, Japan. A five-point Likert scale was used to measure road user satisfaction, then the data were analyzed using stepwise regression. Based on regression model, long- and short-distance road user satisfactions were both affected by two same elements (road surface and road facilities). The availability of sidewalks mostly affected short-distance road user satisfaction. On the other hand, the smoothness of road surface was more considered by long-distance road user. Considering the findings, existing problems of inappropriate-infrastructure quality can be addressed to help satisfy user’s expectations
Application of Buckling Restrained Braces for Seismic Strengthening of Irregular Gravity Load Designed Reinforced Concrete Frame Buildings
Get PDFPast earthquake disasters have shown that irregular gravity load designed (GLD) reinforced concrete (RC) frame buildings were very vulnerable to strong ground shaking. Many of them collapsed and caused loss of human lives as well as materials. Hence, in order to prevent future disasters, this type of buildings needs to be strengthened against earthquake. This paper presents a case study of an innovative approach for seismic strengthening of a typical six story residential building with a soft/weak first story using buckling restrained braces (BRBs). The seismic performance of the original GLD building and the retrofitted one are compared using three dimensional nonlinear dynamic time history analysis in OpenSees. The analysis results show that the innovative seismic strengthening approach for irregular GLD RC frame buildings using BRBs can significantly reduce maximum story drifts as well as building damages which benefits in reducing the risk of building’s collapse during earthquake
Numerical Simulation of Threat-Independent Progressive Collapse
Get PDFA threat-independent approach is usually utilized for progressive collapse analysis of buildings. This approach is referenced in the current guidelines such as “Progressive Collapse Analysis and Design Guidelines for New Federal Office Buildings and Major Modernization Projects” by the U.S. General Service Administration and “Design of Buildings to Resist Progressive Collapse” by the U.S. Department of Defence. However, more studies are required to accurately observe the influence of structural parameters to the response of structures in progressive collapse phenomenon. A parametric study was conducted using advanced nonlinear finite element analysis to assess the utility of the procedures in these documents. The results of the numerical simulations show that a variation of the beam dimensions moderately affects the dynamic load factor. The load factor increases as the beam dimensions increase. Other parameters such as the column dimensions, number of storeys and span lengths, have only negligible effects on the value of the dynamic load factor
Flow Fields in front of a Cylindrical Obstacle
Get PDFAn experimental investigation, conducted in two different flows Reynolds number, was carried out to study the structure of the flow field upstream of a cylindrical obstacle. An Acoustic Doppler Velocity Profiler (ADVP) was used to obtain instantaneously the three directions of the mean velocity. Results of the experiments show the longitudinal velocities, , decrease approaching the cylinder, their distribution becomes more uniform and close to the bed a reverse flow is noticeable with increasing importance. The downward velocity component is clearly shown, continuing with the return flow near the bed, forming a vortex. At positions where the vortex appears upstream from the cylinder, a large increase of the three components of the turbulence intensities is remarked. Approaching the cylinder, one observes the shear stress decreases, having the opposite direction at positions close to the cylinder. A zero value of shear stress should be at the separation point
Estimating Young’s Modulus and Modulus of Rupture of Coconut Logs using Reconstruction Method
Get PDFThis research develops a theory of the so called reconstruction method to estimate the Young’s modulus (E) and modulus of rupture (SR) of coconut logs. The reconstruction method includes among others; flexure test on small-clear specimens, which were taken from locations distributed along the horizontal as well as vertical direction inside the logs. Further, the estimated E and SR were acquired by arranging systematically each of the small clear specimens as if back in the original location in the logs. The estimation was assisted by mechanical theory, statistics (best fit multiple regression equations), mathematics (calculus), and geometry approach. This reconstruction method successfully estimates E and SR of the coconut logs. The average estimated E and SR value as acquired from tree sample number 1 and 2 were 8,118– 8,596 MPa, and 118–124 MPa, respectively. Those two values were still comparable to common US wood species used for construction i.e. 6,660–15,000 MPa (for E); and 58–132 MPa (for SR). Moreover those estimations of E and SR correlated significantly with each other. This again strengthens the reliability and representativeness of the E and SR values for coconut logs as acquired using the proposed reconstruction methods
Ultra Strengthening of Wooden Girders
Get PDFOwing to the natural defects of wood, structural timber is currently used with conservative safety factors. This study investigates the use of Carbon Fiber Reinforced Polymer (CFRP) for improving the strength of structural timber. Four flexural test stages were carried out, the modes of failure of the three specimens in each stage were studied to determine and strengthen the suspected weak zone which caused the failure. It was found that the tensioned fibers of ordinary timber girders normally fail first especially at the sections containing knots. Using a strip of CFRP to strengthen tensioned fibers is a well known technology, but it will not prevent a premature failure due to horizontal shear. A strength increase of 56% was reached by the adaption of shear connectors in the form of screws. After treating tensile and shearing strengths, still testing specimens showed failure at the compressed fibers. By enhancing the compressed fibers with a steel strip, the prototype girders showed a remarkable increase in flexural strength of about 175% compared with the ordinary wooden girders having the same dimensions
Effect of Steel Fibers on the Behavior of Over-Reinforced Beams Subjected to Pure Torsion
Get PDFThe improvement in torsional properties of reinforced concrete (RC) is becoming extremely important in the modern day constructions. Over the years the steel fiber reinforced concrete (SFRC) is being used for improving cracking characteristics of RC. The present paper deals with the behaviour of over reinforced SFRC members subjected to pure torsional loading. Torsion tests on the 15 reinforced steel fiber reinforced concrete beams revealed that, fiber has noticeable effect on the cracking torque and very little effect on the ultimate torsional strength of the member. However fiber inclusion could improve the torsional toughness of the member
Estimating the Influence of Accident Related Factors on Motorcycle Fatal Accidents using Logistic Regression (Case Study: Denpasar-Bali)
Get PDFIn Denpasar the capital of Bali Province, motorcycle accident contributes to about 80% of total road accidents. Out of those motorcycle accidents, 32% are fatal accidents. This study investigates the influence of accident related factors on motorcycle fatal accidents in the city of Denpasar during period 2006-2008 using a logistic regression model. The study found that the fatality of collision with pedestrians and right angle accidents were respectively about 0.44 and 0.40 times lower than collision with other vehicles and accidents due to other factors. In contrast, the odds that a motorcycle accident will be fatal due to collision with heavy and light vehicles were 1.67 times more likely than with other motorcycles. Collision with pedestrians, right angle accidents, and heavy and light vehicles were respectively accounted for 31%, 29%, and 63% of motorcycle fatal accidents
Creep Behaviour of Fly Ash-Based Geopolymer Concrete
Get PDFFly ash-based geopolymer concrete is manufactured using fly ash as its source material and does not use Portland cement at all. Beside fly ash, alkaline solution is also utilized to make geopolymer paste which binds the aggregates to form geopolymer concrete. This paper presents the study of creep behaviour of fly ash-based geopolymer concrete. Four series of specimens with various compressive strengths were prepared to study its creep behaviour for the duration of test up to one year. The test method followed the procedures applied for Ordinary Portland Cement (OPC) concrete. Test results show that fly ash-based geopolymer concrete undergoes low creep which is generally less than that of OPC concrete. After one year of loading, the results for specific creep of fly ash-based geopolymer concrete in this study ranges from 15 to 29 microstrain for concrete compressive strength 67–40 MPa respectively. From the test results, it is also found out that the creep coefficient of fly ash-based geopolymer concrete is about half of that predicted using Gilbert’s Method for OPC concrete