• Structural Engineering and Mechanics
• /
• 제11권6호
• /
• pp.637-650
• /
• 2001

A structural analysis of cracked R.C. members under instantaneous or sustained loads and imposed displacements is presented. In the first part of the paper the problem of deriving feasible moment-curvature diagrams for a long term analysis of R.C. sections is approached in an exact way by using the Reduced Relaxation Function Method in state I uncracked and the method suggested by CEB in state II cracked. In both states the analysis of the main parameters governing the problem has shown that it is possible to describe the concrete creep behaviour in an approximate way by using the algebraic formulation connected to the Effective Modulus Method. In this way the calculations become quite simple and can be applied in design practice without introducing significant errors. Referring to continuous beams, the structural analysis is then approached in a general way, applying the Force Method and the Principle of Virtual Works. Finally, considering single members, the structural analysis is performed by means of a graphical procedure based on the application of feasible moment-rotation diagrams which allow to easily solve various structural problems and to point out the most interesting aspects of the long term behaviour of cracked R.C. members with rigid or elastically deformable redundant restraints.

• 마케팅과학연구
• /
• 제7권
• /
• pp.147-165
• /
• 2001

인터넷비즈니스 기업이 고객과의 성공적인 관계유지를 위해서는 자신들이 구축한 고객베이스내 고객들간 태도나 구매행동패턴 차이에 대한 정확한 이해가 선행되어야 한다. 이러 한 맥락에서 본 연구는 인터넷 고객의 장기지향성에 영향을 미치는 선행변수와 장기지행성 간의 관계가 거래 특성변수인 거래기간에 따라 어떠한 차이가 있는지를 탐색적으로 살펴보 았다. 탐색적 연구문제를 검증하기 위해 인터넷 쇼핑몰에서 상품구매 경험이 있는 고객을 대상 으로 수집된 자료를 분석하고, 분석결과에 대한 전략적 시사점에 대해 논의하였다.

• Geomechanics and Engineering
• /
• 제2권2호
• /
• pp.107-123
• /
• 2010

Ground settlements and pore pressure changes were monitored around a shallow tunnel constructed in clay till during the excavation and primary lining installation. The settlements above the tunnel continued to develop for up to 100 days after the primary lining installation. Triaxial compression tests were carried out to estimate the short-term and long-term deformation characteristics of the till. Numerical simulation was conducted to history match the field measurements, and thus, to quantify the settlements induced by ground stress relief, consolidation and creep. It was found that the surface settlements due to ground stress relief, consolidation and creep are 17, 12 and 71% of total settlement (about 44 mm), respectively. In addition, early installation of rigid concrete lining could be an effective means to reduce the settlement due to creep.

• Steel and Composite Structures
• /
• 제23권5호
• /
• pp.517-527
• /
• 2017

In this paper, the effect of active confinement on the compressive behaviour of circular steel tube-confined concrete (STCC) and concrete-filled steel tube (CFST) columns is investigated. In STCC columns the axial load is only applied to the concrete core, while in CFST columns the load is carried by the whole composite section. A new method is introduced to apply confining pressure on fresh concrete by laterally prestressing steel tubes. In order to achieve different prestressing levels, short-term and long-term pressures are applied to the fresh concrete. Three groups of STCC and CFST specimens (passive, S-active and L-active groups) are tested under axial loads. The results including stress-strain relationships of composite column components, secant modulus of elasticity, and volumetric strain are presented and discussed. Based on the elastic-plastic theory, the behaviour of the steel tube is also analyzed during elastic, yielding, and strain hardening stages. The results show that using the proposed prestressing method can considerably improve the compressive behaviour of both STCC and CFST specimens, while increasing the prestressing level has insignificant effects. By applying prestressing, the linear range in the stress-strain curve of STCC specimens increases by almost twice as much, while the improvement is negligible in CFST specimens.

• The Journal of Asian Finance, Economics and Business
• /
• 제7권9호
• /
• pp.125-134
• /
• 2020

This study examines the nominal price anomaly in the Vietnamese stock market, that is, whether stocks with low nominal price outperform stocks with high nominal price. Using a sample of all 351 companies listed on the Ho Chi Minh Stock Exchange (HOSE) from June 2009 to March 2018, we confirm our hypothesis and document that cheaper stocks yield higher subsequent abnormal returns. The results are robust after controlling for various stock characteristics that have been documented to be value-relevant in prior literature, including firm size, book-to-market ratio, intermediate-term momentum, short-term reversal, skewness, market risk, idiosyncratic risk, illiquidity and extreme daily returns, using both the portfolio analysis and the Fama-MacBeth cross-sectional regression. The negative effect persists in the long term (i.e., after up to 12 months), implying a slow adjustment of stock prices to their intrinsic value. Further analysis show that the observed nominal price anomaly is mainly driven by mispricing but not a latent risk factor proxied by stock price, thus the observed anomaly reflects a mispricing but not a fundamental risk. The study highlights the irrational behaviour of investors and market inefficiency in the Vietnamese stock market and provides important implication for investors in the market.

• Structural Engineering and Mechanics
• /
• 제40권1호
• /
• pp.105-120
• /
• 2011

The strengthening and rehabilitation of reinforced concrete structures with externally bonded carbon fibre reinforced polymer (FRP) laminates has shown excellent performance and, as a result, this technology is rapidly replacing steel plate bonding techniques. This paper addresses this issue, and presents results deals with the influence of external bonded CFRP-reinforcement on the time-dependent behavior of reinforced concrete beams. A total of eight reinforced concrete beams with cracked and un-cracked section, with and without externally bonded CFRP laminates, were investigated for their creep and shrinkage behavior. All the beams considered in this paper were simply supported and subjected to a uniform sustained loading for the period of six months. The main parameters of this study are two types of sustained load and different degrees of strengthening scheme for both cracked and un-cracked sections of beams. Both analytical and experimental work has been carried out on strengthened beams to investigate the cracking and deflection performance. The applied sustained load was 56% and 38% of the ultimate static capacities of the un-strengthened beams for cracked and un-cracked section respectively. The analytical values based on effective modulus method (EMM) are compared to the experimental results and it is found that the analytical values are in general give conservative estimates of the experimental results. It was concluded that the attachment of CFRP composite laminates has a positive influence on the long term performance of strengthened beams.

• Computers and Concrete
• /
• 제9권5호
• /
• pp.357-374
• /
• 2012

The aim of this paper is to develop a procedure able to calculate the long-term stress and strain patterns in modern prestressed composite structures which are largely influenced by creep and shrinkage and whose final static configuration is the result of many phases of loading and restraints conditions. The introduction of equivalent moduli, depending on the viscous and elastic features of materials, can guarantee a significant simplification of the problem presented above. The proposed calculation model has been used to design the "Quattroquercie Viaduct" located on the highway "A3" Salerno-Reggio Calabria, Italy.

• 한국공간구조학회논문집
• /
• 제15권4호
• /
• pp.73-80
• /
• 2015

The new rotary friction damper was developed using several two-nodal rotary frictional components with different clamping forces. Because of these components, the rotary friction damper can be activated by building movements due to lateral forces such as a wind and earthquake. In this paper, various dependency tests such as displacement amplitude, forcing frequency and long term cyclic loading were carried out to evaluate on the structural performance and the multi-slip mechanism of the new damper. Test results show that the multi-slip mechanism is verified and friction coefficients are dependent on displacement amplitute and forcing frequency except long term cyclic loading.

• 보건행정학회지
• /
• 제20권1호
• /
• pp.19-36
• /
• 2010

Fee for long-term care insurance in Korea are determined in proportion to resources utilized according to severity rather than based on categorization of beneficiaries in consideration of the characteristics of resource utilization. This adoption is based on the assumption that as beneficiaries of long-term care insurance, characteristically, demands social services rather than needs medical treatments, the characteristics of beneficiaries and the quality of utilized resources are comparatively homogenous. Therefore, the proposition is that the size of resource consumed by beneficiaries in the same grade is identical. However, even in the same grade, the level of utilized resources is different depending on the characteristic of beneficiaries. In this regard, this study is to examine whether there are differences in the volumes of utilized resources depending on the characteristics of beneficiaries even in the same grade. We analyzed time study data for 2003, 2005, 2006 which conducted by the Korea Institute for Health and Social Affairs. To look at differences in the volumes of utilized resources, we identified characteristics of beneficiaries that influence utilized resource volumes and categorized services provided by facilities into the rehabilitation treatment category, the problematic behavior category, and the physical malfunction category. Then, we examined each service in consideration of service difficulty levels and wage weights. The result of examination showed that differences in utilized resource volumes exist in all three grades depending on the characteristics of beneficiaries. Especially, in the first grade with a high level of seriousness, utilized resource volumes were different for those three service categories and the problematic behaviour category considered dementia was found to consume the largest volume of resources. Moreover, there was the inversion phenomenon of utilized resources volumes between the grades. This result indicates that utilized resource volumes are different even in the same grade depending on the characteristics of beneficiaries and it is required to consider case-mix for reflection of the volumes of utilized resources depending on the characteristics of beneficiaries.

• 한국구조물진단유지관리공학회 논문집
• /
• 제20권2호
• /
• pp.34-39
• /
• 2016

경부 고속철 40 m 단경간 PSC 교량을 대상으로 38 자유도 KTX 동력차를 주행속도 500 km/h까지 12 단계 불규칙 궤도형상과 상호 작용력을 고려하여 해석하였다. 차량의 윤축하중과 중심회전각을 평가하기 위하여 170 m 일반도상을 교량과 조합하여 횡압과 탈선계수 그리고 윤중감소율을 허용기준과 비교하였다. 단순교와 연속교의 교량받침 최대 변위와 누적이동거리를 주행속도별로 해석하였다. PTFE 마찰판과 DP-mate의 EN-1337-2 기준의 장기마찰시험을 수행하였다. 수행된 장기마찰시험은 차세대 고속철의 증가되는 주행속도를 고려하여 개선 방안을 제안하였다.