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.

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.

표준 파괴인성시험편에 대한 탄소성 유한요소해석

박용걸 한국전산구조공학회 1994 한국전산구조공학회논문집 Vol.7 No.4

본 연구의 목적은 표준파괴인장시험편에 대한 탄소성유한요소해석이다. 탄소성파괴역학의 이론과 수치해석을 위한 조건들이 기술되고 균열선단의 특이성을 모형화하기 위한 가능성이 논의된다. 표준파괴인장시험편의 탄소성유한요소해석으로부터 J적분이나 균열개구변위(COD)와 같은 파괴역학계수들과 그들의 상관관계가 계산되고 소성역의 크기와 형태가 구해진다. 실험과 계산결과들이 비교되고 한계하중의 계산이 논의된다. The purpose of this study is elastic plastic finite element analysis for standard fracture toughness specimens. The principles of elastic-plastic fracture mechanics are shortly summarized and the special requirements for computational tools are derived. Possibilities to model the crack tip singularities are mentioned. The relevant fracture parameters like J-Integral and COD and their correlation are evaluated from elastic plastic finite element calculations of standard fracture toughnes specimens. The size and form of the plastic zone are shown. The comparion between experiment and caculation is discussed as well as the application of the limit load analysis.

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.

외부 후긴장에 의한 강합성보의 지간증대

박용걸 서울産業大學校 2001 논문집 Vol.52 No.1

At present, the external post-tensioning method was using as the only method of a reinforcement for the servicing steel plate girder bridge, But in the case of appling the external post-tensioning method in a newly built bridge, because the lengthen of span without increasing the design section area is possible. The higher economical efficient is expected. So, In this study, for investigating the efficiency of span lengthen with appling external post-tensioning method for a newly built single span steel plate girder bridge. The 4-point loaded bending test is carried with changing the external post-tensioning force and span length of specimen. As a result of this study, it is concluded that efficiency of span lengthen by external post-tensioning method is high.

교량점검대의 사용성 및 안전성 연구

박용걸 서울産業大學校 1999 논문집 Vol.50 No.2

This study is for the employment of bridge automatic maintenance trolley. This equipment is more useful than the fixed staging on boom can which is mainly used in the maintenance and reinforcement of bridge. In the result of study, the initial investment of cost is some higher than another maintenance tools. However, it is more efficient to employ this equipment in the bridge which is newly constructed or longer than 400m. In the cost of maintenance or reinforcement, this equipment has also the more advantage as the life term in the longer. As a result, the bridge maintenance trolly has various advantages in the utility, applicability and economic aspects in the maintenance or reinforcement of bridge for the long run.

외부 후긴장후 공법의 적용에 따른 공용중인 판형교 거동의 실험적 연구

박용걸 서울産業大學校 2000 논문집 Vol.51 No.2

The major object of this study is to investigate the strengthening effect and the durability of post external prestressing strengthening method in steel plate girder bridge. After install the strain gaues, O-U gauges, acceleration pick-up at the servicing steel plate girder bridge which have 2 years service period after strengthening by the post external prestressing method, The durability of strengthening effect of steel plate girder bribe is measured during the remove the external prestressing cable. To investigate the behavior difference of steel plate girder brige according to the external prestressing cable, The static field loading test and dynamic field loading test are also carried out before and after removing the external prestressing cable.

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.