• Structural Engineering and Mechanics
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• v.21 no.5
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• pp.591-620
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• 2005

A general analytical model for thin-walled composite beams with an arbitrary open/(or/and) closed cross section and arbitrary laminate stacking sequence i.e., symmetric, anti-symmetric as well as un-symmetric with respect to the mid plane of the laminate, is developed in the first paper. All the mechanical properties, mechanical centre of gravity and mechanical shear centre of the cross section are defined in the function of the geometry and the material properties of the section. A program "fungen" and "clprop" are developed in Fortran to compute all the mechanical properties and tested for various isotropic sections first and compared with the available results. The locations of mechanical centre of gravity and mechanical shear centre are given with respect to the fibre angle variation in composite beams. Variations of bending and torsional stiffness are shown to vary with respect to the fibre angle orientations.

• Earthquakes and Structures
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• v.13 no.2
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• pp.177-191
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• 2017

In the present study, exterior beam column sub-assemblages are designed in accordance with the codal stipulations prevailed at different times prior to the introduction of modern seismic provisions, viz., i) Gravity load designed with straight bar anchorage (SP1), ii) Gravity load designed with compression anchorage (SP1-D), iii) designed for seismic load but not detailed for ductility (SP2), and iv) designed for seismic load and detailed for ductility (SP3). Comparative seismic performance of these exterior beam-column sub-assemblages are evaluated through experimental investigations carried out under repeated reverse cyclic loading. Seismic performance parameters like load-displacement hysteresis behavior, energy dissipation, strength and stiffness degradation, and joint shear deformation of the specimens are evaluated. It is found from the experimental studies that with the evolution of the design methods, from gravity load designed to non-ductile and then to ductile detailed specimens, a marked improvement in damage resilience is observed. The gravity load designed specimens SP1 and SP1-D respectively dissipated only one-tenth and one-sixth of the energy dissipated by SP3. The specimen SP3 showcased tremendous improvement in the energy dissipation capacity of nearly 2.56 times that of SP2. Irrespective of the level of design and detailing, energy dissipation is finally manifested through the damage in the joint region. The present study underlines the seismic deficiency of beam-column sub-assemblages of different design evolutions and highlights the need for their strengthening/retrofit to make them fit for seismic event.

• Steel and Composite Structures
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• v.28 no.6
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• pp.719-734
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• 2018

Prior to the introduction of modern seismic guidelines, it was a common practice to provide straight bar anchorage for beam bottom reinforcement of gravity load designed building. Exterior joints with straight bar anchorages for beam bottom reinforcements are susceptible to sudden anchorage failure under load reversals and hence require systematic seismic upgradation. Hence in the present study, an attempt is made to upgrade exterior beam-column sub-assemblage of a three storied gravity load designed (GLD) building with single steel haunch. Analytical formulations are presented for evaluating the haunch forces in single steel haunch retrofit. Influence of parameters that affect the efficacy and effectiveness of the single haunch retrofit are also discussed. The effectiveness of the single haunch retrofit for enhancing seismic performance of GLD beam-column specimen is evaluated through experimental investigation under reverse cyclic loading. The single steel haunch retrofit had succeeded in preventing the anchorage failure of beam bottom bars of GLD specimen, delaying the joint shear damage and partially directing the damage towards the beam. A remarkable improvement in the load carrying capacity of the upgraded GLD beam-column sub-assemblage is observed. Further, a tremendous improvement in the energy dissipation of about 2.63 times that of GLD specimen is observed in the case of upgraded GLD specimen. The study also underlines the efficacy of single steel haunch retrofit for seismic upgradation of deficient GLD structures.

• Earthquakes and Structures
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• v.16 no.2
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• pp.235-251
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• 2019

Corrosion of reinforcement is the greatest threat to the safety of existing reinforced concrete (RC) structures. Most of the olden structures are gravity load designed (GLD) and are seismically deficient. In present study, investigations are carried out on corrosion damaged GLD beam-column sub-assemblages under reverse cyclic loading, in order to evaluate their seismic performance. Five GLD beam-column sub-assemblage specimens comprising of i) One uncorroded ii) Two corroded iii) One uncorroded strengthened with steel bracket and haunch iv) One corroded strengthened with steel bracket and haunch, are tested under reverse cyclic loading. The performances of these specimens are assessed in terms of hysteretic behaviour, energy dissipation and strength degradation. It is noted that the nature of corrosion i.e. uniform or pitting corrosion and its location have significant influence on the behaviour of corrosion damaged GLD beam-column sub-assemblages. The corroded specimens with localised corrosion pits showed in-cyclic strength degradation. The study also reveals that external strengthening which provides an alternate force path but depends on the strength of the existing reinforcement bars, is able to mitigate the seismic risk of corroded GLD beam-column sub-assemblages to the level of control uncorroded GLD specimen.

• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.37-43
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• 2006

In 2006, the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) plans to undertake (subject to receiving the necessary approvals) a Pilot program for $CO_2$ storage within a depleted gas reservoir. The Otway Basin Pilot Program (OBPP) aims to demonstrate that subsurface $CO_2$ storage is both economically and environmentally sustainable in Australia. This will be the first $CO_2$ storage program in the world to utilise a depleted gas reservoir and, hence, the experience gained will be a valuable addition to the range of international $CO_2$ storage programs that are underway or being planned. A key component of the OBPP is the design of an appropriate geophysical monitoring strategy that will allow the subsurface migration of the $CO_2$ plume to be tracked and to verify that containment has been successful. This paper presents the results from modelling the predicted gravity response to $CO_2$ injection into the Otway Basin reservoir, where the goal was to determine minimum volumes of $CO_2$ that may be detectable using non-seismic geophysical techniques. Modelling results indicate that gravity measurements at 10 m spacing within the existing observation well and the planned $CO_2$ injection well would provide excellent vertical resolution, even for the smallest $CO_2$ volume modelled (10000 tonnes), but resolving the lateral extent of the plume would not be possible without additional wells at closer spacing.

• Journal of the Korean housing association
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• v.12 no.2
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• pp.151-160
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• 2001

The purpose of this study is for investigating characteristics of changing residential density and relations between housing supply and redistribution of population in Daegu. As a result, the following conclusions could be made. First, land development and housing supply have important effect on distribution of population and changing residential density in Daegu. Second, according to massive site development to meet the housing demand in suburban area, the suburbanization has begun and build-up-area grows faster, so centre of gravity of residential density increasing rate has moved to the suburban. Third, the inner district and the district near urban centre will need remodelling or redevelopment project in the near future.

• Structural Engineering and Mechanics
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• v.48 no.5
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• pp.661-679
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• 2013

In this work, the safety performance of a commercial motorcycle helmet already placed on the market is assessed. The assessed motorcycle helmet is currently homologated by several relevant motorcycle standards. Impacts including translational and rotational motions are accurately simulated through a finite element numerical framework. The developed model was validated against experimental results: firstly, a validation concerning the constitutive model for the expanded polystyrene, the material responsible for energy absorption during impact; secondly, a validation regarding the acceleration measured at the headform's centre of gravity during the linear impacts defined in the ECE R22.05 standard. Both were successfully validated. After model validation, an oblique impact was simulated and the results were compared against head injury thresholds in order to predict the resultant head injuries. From this comparison, it was concluded that brain injuries such as concussion and diffuse axonal injury may occur even with a helmet certified by the majority of the motorcycle helmet standards. Unfortunately, these standards currently do not contemplate rotational components of acceleration. Conclusion points out to a strong recommendation on the necessity of including rotational motion in forthcoming motorcycle helmet standards and improving the current test procedures and head injury criteria used by the standards, to improve the safety between the motorcyclists.

• Korean Journal of Applied Biomechanics
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• v.32 no.1
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• pp.24-30
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• 2022

Objective: The purpose of this study was to determine the factors of successful and unsuccessful movements through the analysis of kinematics and muscle activity of the Free Aerial Cartwheel on the balance beam. Method: Subjects (Age: 22.8 ± 2.4 yrs., Height: 158.7 ± 5.0 cm, Body mass: 54.1 ± 6.4 kg, Career: 13 ± 2.4 yrs.) who were currently active as female gymnasts participated in the study. They had no history of surgical treatment within 3 months. Subject criteria included more than 10 years of professional experience in college and professional level of gymnastics and the ability to conduct the Free Aerial Cartwheel on the Balance Beam. Each subject performed 10 times of Free Aerial Cartwheel on the balance beam. One successful trial and one unsuccessful trial (failure) among 10 trials were selected for the comparison. Results: It was found that longer time required in case of unsuccessful trial when performing the Free Aerial Cartwheel on the balance beam compared with successful trial. It is expected to be the result of movement in the last landing section (i.e. phase 5). In addition, it was found that the center of gravity of the body descends at a high speed to perform the jump (i.e. phase 2) in order to obtain a sufficient jumping height when the movement is successful while the knee joint is rapidly extended to perform a jump when movement fails. In the single landing section after the jump (i.e. phase 4), if the ankle joint rapidly dorsiflexed after take-off and the hip joint rapidly flexed, so landing was not successful. Conversely, in a successful landing movement, muscle activity of the biceps femoris was greatly activated resulting no shaking in the last landing section (i.e. phase 5). Conclusion: In order to succeed in this movement, it is necessary to perform a strong jump after rapidly descending the center of gravity of the body using the force of the biceps femoris muscle. Further improvement of the skills on the balance beam requires the analysis of the game-like situation with continuous research on kinematic and kinematic analysis of various techniques, jumps, turns, etc.

• Structural Engineering and Mechanics
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• v.73 no.3
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• pp.239-257
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• 2020

In the present study, an innovative steel bracket and haunch hybrid scheme is devised, for retrofitting of earthquake damaged deficient beam-column sub-assemblages. Formulations are presented for evaluating haunch force factor under combined load case of lateral and gravity loads for the design of double haunch retrofit. The strength hierarchies of control and retrofitted beam-column sub-assemblages are established to showcase the efficacy of the retrofit in reversing the undesirable strength hierarchy. Further, the efficacy of the proposed retrofit scheme is demonstrated through experimental investigations carried out on gravity load designed (GLD), non-ductile and ductile detailed beam-column sub-assemblages which were damaged under reverse cyclic loading. The maximum load carried by repaired and retrofitted GLD specimen in positive and negative cycle is 12% and 28% respectively higher than that of the control GLD specimen. Further, the retrofitted GLD specimen sustained load up to drift ratio of 5.88% compared with 2.94% drift sustained by control GLD specimen. Repaired and retrofitted non-ductile specimen, could attain the displacement ductility of three during positive cycle of loading and showed improved ductility well above the expected displacement ductility of three during negative cycle. The hybrid haunch retrofit restored the load carrying capacity of damaged ductile specimen to the original level of control specimen and improved the ductility closer to the expected displacement ductility of five. The total cumulative energy dissipated by repaired and retrofitted GLD, non-ductile and ductile specimens are respectively 6.5 times, 2.31 times, 1.21 times that of the corresponding undamaged control specimens. Further, the damage indices of the repaired and retrofitted specimens are found to be lower than that of the corresponding control specimens. The novel and innovative steel bracket and haunch hybrid retrofit scheme proposed in the present study demonstrated its effectiveness by attaining the required displacement ductility and load carrying capacity and would be an excellent candidate for post-earthquake retrofit of damaged existing RC structures designed according to different design evolutions.

• Journal of The Korean Association For Science Education
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• v.32 no.6
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• pp.1039-1049
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• 2012

The first category of Affective Domain objectives in Bloom's Taxonomy is about "Receiving". In it, the first subdivision listed is "Awareness" (Krathwohl, Bloom & Masia, 1964). Since these categories are intended to be hierarchical in ascending order of internalization, it is important that young learners be given ample opportunities in their learning experiences in class to be aware of positive values and effective life skills. This paper reports a feasibility study on the adoption of an integrative cognitive-affective learning approach in a primary school science lesson. 37 primary six students in a Singapore primary school were taught the concept of centre of gravity, including a hands-on activity to find the centre of gravity of an irregularly shaped cardboard by using a plumbline. After reviewing how a plumbline works, their teacher then led them into a discussion on the question "Who is the plumbline in your life?" a reference to identifying positive role models in their lives. From the transcript of the students' in-class sharing and their written responses to the question, it is clear that the integrative cognitive-affective learning approach did enable students to present their ideas and learning experiences in the affective domain quite readily. This conclusion provides a valuable lead to a follow-up project on whether students who are exposed to such integrative learning approaches will be more capable and more aware of identifying important positive social habits or values. If so, then the teaching of values in schools could take on a whole new dimension, that of borrowing students' learning energy in the cognitive domain to learn values and life skills in the affective domain.