• Advances in concrete construction
• /
• 제5권5호
• /
• pp.469-479
• /
• 2017

Balanced cantilever construction is extensively used in the construction of prestressed concrete (PSC) box-girder bridges. Shear-lag effect is usually considered in finished bridges, while the cumulative shear-lag effect in bridges during balanced cantilever construction is considered only rarely. In this paper, based on the balanced cantilever construction sequences of large-span PSC box-girder bridges, the difference method is employed to analyze the cumulative shear-lag effect of box girders with varying depth under the concrete segments' own weight. During cantilever construction, no negative shear-lag effect is generated, and the cumulative shear-lag effect under the balanced construction procedure is greater than the instantaneous shear-lag effect in which the full dead weight is applied to the entire cantilever. Three cross-sections of Jianjiang Bridge were chosen for the experimental observation of shear-lag effect, and the experimental results are in keeping with the theoretical results of cumulative shear-lag effect. The research indicates that only calculating the instantaneous shear-lag effect is not sufficiently safe for practical engineering purposes.

• Structural Engineering and Mechanics
• /
• 제28권2호
• /
• pp.207-220
• /
• 2008

The shear lag has been studied for many years. Nevertheless, existing research gives a variety of stress concentration factors. Unlike the elementary beam theory, the application of load is not unique in reality. For example, concentrated load can be applied as point load or distributed load along the height of the web. This non-uniqueness may be a reason for the discrepancy of the stress concentration factors in the existing studies. The finite element method has been often employed for studying the effect of the shear lag. However, not many researches have taken into account the influence of the finite element mesh on the shear lag phenomenon, although stress concentration can be quite sensitive to the mesh employed in the finite element analysis. This may be another source for the discrepancy of the stress concentration factors. It also needs to be noted that much less studies seem to have been conducted for the shear lag effect on deflection while some design codes have formulas. The present study investigates the shear lag effect in a simply supported box girder by the three-dimensional finite element method using shell elements. The whole girder is modeled by shell elements, and extensive parametric study with respect to the geometry of a box girder is carried out. Not only stress concentration but also deflection is computed. The effect of the way load is applied and the dependency of finite element mesh on the shear lag are carefully treated. Based on the numerical results thus obtained, empirical formulas are proposed to compute stress concentration and deflection that includes the shear lag effect.

• Structural Engineering and Mechanics
• /
• 제29권1호
• /
• pp.77-89
• /
• 2008

Presence of high degree of orthotropy enhances shear lag phenomenon in laminated composite box-beams and it persists till failure. In this paper three key parameters governing shear lag behavior of laminated composite box beams are identified and defined by simple expressions. Uniqueness of the identified key parameters is proved with the help of finite element method (FEM) based studies. In addition to this, for the sake of generalization of prediction of shear lag effect in symmetrical laminated composite box beams a feed forward back propagation neural network (BPNN) model is developed. The network is trained and tested using the data base generated by extensive FEM studies carried out for various b/D, b/tF, tF/tW and laminate configurations. An optimum network architecture has been established which can effectively learn the pattern. Computational efficiency of the developed ANN makes it suitable for use in optimum design of laminated composite box-beams.

• Structural Engineering and Mechanics
• /
• 제73권2호
• /
• pp.167-179
• /
• 2020

This study provides a simplified method for the evaluation of shear lag stress in rectangular box T-joints. The occurrence of shear lag phenomenon in the box T-joint generates stress concentration localized at both web-flange junctions of the beam, which leads to cracking or failure in the weld region of the joint. To prevent such critical circumstance, peak stress at the weld region is required to be checked during a preliminary design stage. In this paper, the shear lag stresses in the T-joints were evaluated using least-work solution in which the longitudinal displacements of the beam flange and web were presumed. The evaluation process considered particularly the effect of column flange flexibility, which was represented by an axial spring model, on the shear lag stress distribution. A simplified method for stress evaluation was provided to avoid solving complex mathematical problems using a stress modification factor β_s from a parametric study. The results showed that the proposed method was valid for predicting the shear lag stress in the box T-joints manually, as well compared with finite element results. The results are further summarized, discussed, and clarified that more flexible column flange caused higher stress concentration.

• 기술혁신학회지
• /
• 제19권4호
• /
• pp.687-710
• /
• 2016

본 연구의 목적은 국가연구개발사업을 대상으로 각 연구단계별 연구개발 지출과 논문 성과 간의 시차구조를 분석하는 것이다. 이에 본 연구는 6T(IT, BT, NT, ST, ET, CT) 기술로 범주화 된 104개 기술의 횡단면 자료와 2007년부터 2014년까지의 시계열로 구성된 패널자료를 분석 자료로서 활용하였으며, 일반적인 시차분포모형을 통해 회귀분석을 실시할 경우 다중공선성이 내포된 분석결과가 도출될 가능성이 크기 때문에 다항시차분포모형을 통해 시차효과를 분석하였다. 그 결과 기초연구의 경우 4년 간 비교적 고른 분포를 보이는 것으로 나타났고, 응용연구와 개발연구의 경우 각각 3년, 2년간 투자효과가 유효한 것으로 확인되었다. 이러한 결과로 보건대, 국가연구개발사업의 논문 성과를 진단함에 있어 각 연구개발단계별 시차적 특성을 감안한 분석 및 평가가 신중하게 고려될 필요가 있을 것이다.

• Structural Engineering and Mechanics
• /
• 제74권3호
• /
• pp.445-455
• /
• 2020

Shear lag phenomenon has long been taken into consideration in various structural codes; however, the AISC provisions have not proposed any specific equation to calculate the shear lag ratio in some cases such as fillet-welded connections of front-to-front double channel sections. Moreover, those equations and formulas proposed by structural codes are based on the studies that were conducted on riveted and bolted connections, and can be applied to single channel sections whilst using them for fillet-welded double channels would be extremely conservative due to the symmetrical shape and the fact that bending moments will not develop in the gusset plate, resulting in less stress concentration. Numerical models are used in the present study to focus on parametric investigation of the shear lag effect on fillet-welded tension connection of double channel section to a gusset plate. The connection length, the eccentricity of axial load, the free length and the thickness of gusset plate are considered as the key factors in this study. The results are then compared to the estimates driven from the AISC-LRFD provisions and alternative equations are proposed.

• Asia Pacific Journal of Business Review
• /
• 제6권2호
• /
• pp.61-76
• /
• 2022

Based on the concept of advertising expenditure, manufacturing firm performance, and enterprise life cycle, this research conducts the listed Chinese manufacturing listed in 2016-2018 as the research sampling and divides these listed companies into three periods: growth, maturity, and decline. Next, this paper conducts empirical research from three aspects: advertising expenditure or investment and manufacturing firm performance, lag effect of advertising expenditure, and outcome effect and lag effect of advertising investment. It is found that in different stages of manufacturing enterprises, different advertising expenditures will have different impacts on the performance of manufacturing enterprises. In the growth stage, the advertising investment of manufacturing enterprises will significantly affect the performance results of the current period, and there will be the long-term lag effect. In contrast, the mature stage of enterprises' advertising investment has a shorter period of lag effect, while in the recession stage, the mature stage of manufacturing enterprises' advertising investment will have a shorter period of lag effect. The empirical results are not significant. This study provides a reference for manufacturing enterprises in different stages in the decision-making of advertising investment.

• 방재기술
• /
• 통권15호
• /
• pp.11-21
• /
• 1993

This report is announced about thermal lag of painted heat detectors. Thermal lag is forecast result from painting the part of heat receiving. Test is simulated that heat detector is painted by synthetic resin emulsion paint according to the cricumstance of installation, corrosion, temperature, dust.

• 기술혁신연구
• /
• 제22권1호
• /
• pp.1-22
• /
• 2014

R&D 투자는 투입 시점과 산출 시점 사이에 시차(time lag)가 존재한다. 따라서 기업의 R&D 투자와 성과와의 관계를 분석할 때 R&D 투입의 시차효과를 정확히 반영하지 않을 경우 분석에 심각한 오류가 발생할 수 있기 때문에 본 연구는 기업 R&D 투자의 시차 효과의 추정을 목적으로 한다. 시차분포모형의 하나인 Almon 모형을 사용하여 기업의 R&D 투자의 투입 시점과 산출 시점 사이의 시차를 측정하였다. 이를 위해 2002년부터 2009년까지의 기업 패널 데이터를 구축하였다. R&D 투자는 기업의 R&D 투자 금액으로, R&D 성과는 특허 출원 건수로 정의하여 분석을 실시하였고 '투자-산출' 프로세스에 소요되는 시차의 길이를 추정하였다. 분석 결과 전체 기술 영역에서 R&D 투자와 특허 출원 사이의 시차는 1~2년으로 분석되었다. 화학, 금속 및 금속 가공, 전기 및 전자, 정밀 과학, 기계 제조의 다섯 개 산업군에 대해 각각 시차의 길이를 추정하였으며 산업군별로 추정된 시차의 길이에 차이가 존재하였다.

• 산업기술연구
• /
• 제21권B호
• /
• pp.273-280
• /
• 2001

In this study, a driver model based on the lead-lag controller for stable maneuver of a highly nonlinear, multi-dimensional, numerically stiff multibody vehicle model according to the various handling test requirements such as steady-state cornering, double lange change, etc. is presented The lead-lag controller is developed with lead and lag compensation. which use the transfer function with cross-over frequency by frequency response method. The proposed driver model is applied to a vehicle model in steady-state and slalom maneuver to verify its effectiveness and validity. The results show that the proposed path control strategy is excellent both in pursuing the desired course and stability of the vehicle.