철도레일의 파괴 및 피로에 대한 안전도평가 및 잔류수명계산

박용걸 한국산업안전학회 1995 한국안전학회지 Vol.10 No.2

The fatigue failure of rail is a principal source of derailment accidents. The reduction of fatigue failures can be achieved by intensive track maintenance and periodic safety assessments for the railway. For the safety assessments, it is required to have more accurate knowledge for fatigue behavior such as the crack initiation, propagation, crack growth rate and the remaining service life in rail. In this paper, the mean stress effects for the fatigue behavior of rail steel are studied. For this study, the fatigue test is conducted and some equations for fatigue evaluation are applied and compared. From the results, we can see that the fatigue crack growth rate is the more increased as the mean stress is the more increased, the mean stress effect is represented well by the combination of stress intensity factor range and maximum stress intensity factor and Crocker and Range's equation represented by ΔK, K_(max) is the best fit for fatigue evaluation and safety assessment of rail.

외부 후긴장으로 보강한 강철도교에 대한 실험 및 해석적 연구

박용걸 서울産業大學校 2005 논문집 Vol.54 No.4

It analyzed the mechanical behaviors of non-ballasted railway bridge(steel plate girder type) with ballast reinforced on the finite element analysis, field test and laboratory test for the static and dynamic responses. The major objective of this study is to investigate the effects and application of reinforcement for steel plate girder railway bridge by the external post-tensioning method. The reinforcement of non-ballast railway bridge had obviously stable dynamic behaviors due to the additional dead force which was ballast. But in case of static behaviors, static displacements and stresses had increased nearly the allowable values. Therefore we analyzed the mechanical behaviors of non-ballasted railway bridge with ballast reinforced and external post-tensioning reinforced on the finite element analysis and laboratory test for the static and dynamic behavior. As a result, the reinforcement of ballasted railway bridge the external post-tensioning method are obviously effective for the additional dead force which is ballast. The analytical and experimental study are carried out to investigate the post-tension force decrease bending behavior and deflection in composite bridge for serviceability. The servicing railway bridge with ballast reinforced has need of the reasonable reinforcement measures which could be reducing the effect of additional dead load that degradation phenomenon of structure by an unusual stresses and a drop durability.

외부 후 긴장 공법을 이용한 강합성보의 보강에 관한 연구

박용걸,박영훈,이승용,Park, Yong-Gul,Park, Young-Hoon,Lee, Seung-Yong 한국강구조학회 2000 韓國鋼構造學會 論文集 Vol.12 No.5

외부 후 긴장 공법은 설계에 수반되는 구조해석이 비교적 명확하여 강교량 구조물뿐만 아니라 건축구조물 등 그 적용 범위가 매우 넓은 보강방법이다. 본 연구에서는 후 긴장 공법에 있어서 긴장력 도입 과정의 강합성보의 거동을 연구하기 위하여 긴장력 증가에 따른 긴장재, 경간 중앙부 하부 플랜지, 정착단 주형 하부 플랜지의 도입 변형율과 긴장재 절곡 각도에 따른 도입 전단력 및 압축력을 실험 및 해석적으로 분석하였다. 또한 긴장력 도입 후 정적 휨 재하 실험을 수행하여 긴장력 도입 정도에 따른 휨 보강 정도를 분석하였으며, 절곡 각도의 변화에 따른 전단보강 및 휨 보강 양상을 연구하였다. 그 결과 외부 후 긴장력 도입에 따른 휨 보강 효과가 매우 높은 것으로 분석되었으며, 긴장재의 절곡 배치에 의해서는 추가적으로 전단보강 효과까지 나타났다. In strengthening structure, the external post-tensioning method which secure clearness in the structure analysis process is adopted to bridges as well as architecture structure. In this study, to investigate the behavior of composite beam in the process of post-tensioning, the amount of prestress force loss, the amount of prestressed compression stress at the lower flange and the behavior of lower flange connected with anchorage are analyzed by comparing the results of finite element analysis with the measured results of installed strain gauges. After finishing the post-tensioning, the strengthening effect of external post-tensioning method is analyzed by static loading test. It is also investigated that the strengthening effect of shear section in the harped external post-tensioning specimens.

構造用鋼의 波勞龜裂成長에 대한 平均應力의 영향

박용걸 大田工業大學 1988 한밭대학교 논문집 Vol.5 No.1

本 硏究에서는 構造用鋼材를 사용하여 CT試驗片을 제작하였으며, 疲勞龜裂成長에 영향을 미 치는 因子中 平均應力의 영향을 살피고자 R= 0.1~0.7의 범위에서 疲勞實驗을 행하여 다음과 같은 사실을 얻을 수 있었다. 平均應力이 증가함에 따라 龜裂成長速度는 점차적으로 증가하며, 破斷時까지의 荷重反複回數 가 감소함을 알 수 있었다. 荷重幅이 커짐에 따라 龜裂成長速度는 현저히 증가함을 알 수 있었다. 또 R < 0.5인 경우 平均應力을 고려한 Elber式이 Paris-Erdogan式보다 龜裂成長速度가 크게 算定됨을 알 수 있었다.

不規則荷重下의 道路橋의 波勞擧動 解析

박용걸 大田工業大學 1989 한밭대학교 논문집 Vol.6 No.1

ABSTRACT The principal object of this study is to evaluate the fatigue behavior of struc- tural steel members subjected to service loading. The main procedures of this study are; 1) A theoretical feasibility study of RMC (Root Mean Cube) model which is in the equivalent stress concept for the fatigue evaluation of structural member under service loading; 2) A messurement and statistical analysis of service stress cycles observed in highway bridge, and a simulation of basic stress range block for fatigue test; 3) A performance of fatigue tests under equivalent load (RMC, RMS), single over load, ascending and descending load, and three types of random load (10 4, 5 x 104, 105 Cycles/Block) which are obtained by transformation of the basic stress range block; 4) An experimental feasibility evaluation of RMC model by the fatigue test results and also a study on the interaction, sequence and block size effects according to the change of random stress ranges on the fatigue behavior. The results of fatigue evaluation and fatigue test under random and ordered loads show that fatigue evaluation by RMC model in equivalent stress concept is good to predict the fatigue behavior (da/dn-ΔK, Nf) of structural members under service loading. Also when the fatigue crack growth exponent, m, is greater than three, the fatigue evaluation by RMC model is desirable. And the interaction, sequ- ence effects according to the change of random stress range do not affect the fatigue life, but the smaller block size is the faster fatigue crack growth rate is. The principal object of this study is to evaluate the fatigue behavior of structural steel members subjected to service loading. The main procedures of this study are; 1) A theoretical feasibility study of RMC (Root Mean Cube) model which is in the equivalent stress concept for the fatigue evaluation of structural member under loading; 2) A measurement and statistical analysis of service stress cycles observed in highway bridge, and a simulation of basic stress range block for fatigue test; 3) A performance of fatigue tests under equivalent load (RMC, RMS), single over load, ascending and descending load, and three types of random load (1^4, 5 × 10^4, 10^5 Cycles/Block) which are obtained by transformation of the basic stress range block; 4) An experimental feasibility evaluation of RMC model by the fatigue lest results and also a study on the interaction, sequence and block size effects according to the change of random stress ranges on the fatigue behavior. The results of fatigue evaluation and fatigue test under random and ordered loads show that fatigue evaluation by RMC model in equivalent stress concept is good to predict the fatigue behavior (da/dn-△K, N_f) of structural members under service loading. Also when the fatigue crack growth exponent, m, is greater than three, the fatigue evaluation by RMC model is desirable. And the interaction, sequence effects according to the change of random stress range do not affect the fatigue life, but the smaller block size is the raster fatigue crack growth rate is.

外的 프리스트레싱 工法을 利用한 鋼構造部材의 補强에 관한 硏究

박용걸 서울産業大學校 2000 논문집 Vol.51 No.2

The major objective of this study is to investigate the effects of reinforcement for the structural steel member by the external post-tensioning method. We analysed the mechanical behaviors of the lower flange, the concrete slab, the anchorage and the amount of prestress loss for tendon on the experimental test are analysed by the finite element analysis. As a result, the reinforcement of structural steel member by the external post-tensioning method. are obviously effective for the bending and shear forces.

프리스트레싱 도입에 따른 강판형교 횡분배 거동

박용걸 서울産業大學校 2001 논문집 Vol.52 No.1

The field loading test and analytical study are carried out to investigate the post-tension force transverse distribution behavior in composite plate girder bridge. To develop the FEM model which reflect well the post-tension force transverse distribution behavior of servicing bridge. Two types FEM model are adopted. From this study, It is concluded that the grillage FEM model which is used in general design process underestimate the post-tension transverse distribution behavior. The modified FEM model which slab is modeled with the shell element and girder is modeled with the beam element reflect stiffness ratio effect. The increase of stiffness ratio results in the decrease of post-tension transverse distribution behavior efficiency. So, the charged post-tension force of post-tension girder is increase with the increase of stiffness ratio. The analytical results with the modified FEM model is well agree with the results of filed loading test. With the comparing the results of field loading test which carried out before the post-tensioning with the results of field loading test which carried out after post-tensioning, It is investigated that the static live load transverse distribution behavior of servicing bridge is not effect by the post-tensioning.

변동하중하의 강구조 부재의 피로해석 모델

박용걸 大田工業大學 1991 한밭대학교 논문집 Vol.8 No.1

The object of this study is the investigation of compatibility on RMC model for fatigue evaluation under real loading condition and the programming to apply to the practical structural member. The procedure of this study is to measure stress cycles from the railway bridge, to take statistics and simulate to the probability density function according to the frequency distribution of stress range, and to make to fatigue test on simulated loading model and equivalent loading model (RMC). Especially, when the fatigue test, the number of stress cycle per block was 10^3 reported the most similar to the real loading condition. To make this possible the micro computer connected with fatigue test machine was used, so it could control the irregular stress range automatically. The result was that the faster variation of stress ranges ; velocity of traffic loads on bridge, the more fatigue damage. And the compatible way to evaluate the fatigue behavior of structural steel member under real loads was the RMC model of the equivalent stress concept.

유한요소법을 이용한 수정응력확대계수의 계산

박용걸 大田産業大學校 1993 한밭대학교 논문집 Vol.10 No.1

해석적인 방법으로 임의의 형상과 재료특성, 경계조건 및 균열 등의 결함을 가진 구조부재의 응력확대계수를 계산하는 것은 실제로 불가능하다. 본 논문에서는 이 계산을 용이하게 하기 위하여 유한요소법을 이용한 수정응력학대계의 계산을 시도한다. 이를 위해 가상균열확내법, 변위법, 응력법 그리고 J 직분법과 같은 몇가지 파괴역학 이론이 유한요소법과 연된된다. 사용된 방법들의 결과치는 해석적인 방법의 결과와 비교된다. 이로부터 에너지평형개념을 기초로 한 방법이 상당히 좋은 결과를 준다는 것을 알 수 있으며 결과적으로 유한요소법을이용하여 임의의 구조부재의 응력확대계수를 계산할 수 있다는 것이 판명된다. In fact, it is impossible to calculate the stress intensity factor of strutural member with any shape, material propertier, boundary conditions and cracks by analytical method. In this paper, the author try to calculate the correction stress intensity factor using the finite element method which make it easy to calculate it. For this, some principles of fracture mechanics such as virtual crack extension method, displacement subsitution method, stress substitution method, J Integral, are related the finite element method. All the results of above methods are compared with the analytical ones. From the results, we can see that the global method is satisfactory with a good accuracy. Especially the J integral gives the most accurate result. As a result, it is turned out that the finite element method can be used to calculate the correction stress intensity factors of any structural member.

자갈도상의 노후화에 따른 궤도구조의 동적응답 특성에 관한 연구

박용걸 서울産業大學校 2005 논문집 Vol.54 No.4

The major objective of this study is to investigate the dynamic behaviors of track due to the deterioration characteristics of ballast for servicing tracks by the field test. The durability of ballast plays an important role in the track behaviour. To estimate the deterioration characteristics of ballast, several tests have been carried out by several shcolars. The deterioration characteristics of ballast is one of the most important factor in the dynamic behaviour of track and its life. In this paper abrasion/breakage characteristics of ballast is studied to predict the effect of physical ballast characteristics on ballast track. To reveal deterioration characteristics of ballast, the field test were carried out. The deterioration characteristics, studied in this paper, is applied to the dynamic behaviour of track in various conditions.