• Computers and Concrete
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• 제6권6호
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• pp.451-472
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• 2009

Based on a numerical method to analyse the full-range behaviour of prestressed concrete beams with unbonded tendons, parametric studies are carried out to investigate the influence of 11 parameters on the curvature ductility of unbonded prestressed concrete (UPC) beams. It is found that, among various parameters studied, the depth to prestressing tendons, depth to non-prestressed tension steel, partial prestressing ratio, yield strength of non-prestressed tension steel and concrete compressive strength have substantial effects on the curvature ductility. Although the curvature ductility of UPC beams is affected by a large number of factors, rather simple equations can be formulated for reasonably accurate estimation of curvature ductility. Conversion factors are introduced to cope with the difference in partial safety factors, shapes of equivalent stress blocks and the equations to predict the ultimate tendon stress in BS8110, EC2 and ACI318. The same equations can also be used to provide conservative estimates of ductility of UPC beams with compression steel.

• International Journal of Concrete Structures and Materials
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• 제7권4호
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• pp.265-271
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• 2013

Prestressed concrete cylindrical pipe (PCCP) has been widely used for the distribution of water in communal, industrial, and agricultural systems for a long time. However, as it deteriorates, structural failures have been experienced. Replacing the entire existing PCCP with partial damages is not an economical method. Currently, as a cost effective repairing method, a new approach using fiber reinforced polymer (FRP) has been applied. A new design procedure of this method was proposed considering various kinds of loading condition. However, it is not easy to apply this method for design purpose due to its complex procedures. The objective of this study is to provide a new design criteria and process for PCCP rehabilitation with FRP. Through this method, the appropriate quantities of FRP layers will be decided after examining of limit states of deteriorated PCCP. For this purpose, two deterioration conditions are assumed; fully deteriorated and partially deteriorated. Different limit states for each case are applied to decide the quantities of attached FRP. The concept of "margin of safety" is used to judge whether the design results are within the optimal ranges to satisfy all limit states.

• Steel and Composite Structures
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• 제21권1호
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• pp.195-216
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• 2016

The dynamic characteristics of continuous steel-concrete composite beams considering the effect of interlayer slip were investigated based on Euler Bernoulli's beam theory. A simplified calculation model was presented, in which the Mode Stiffness Matrix (MSM) was developed. The natural frequencies and modes of partial-interaction composite continuous beams can be calculated accurately and easily by the use of MSM. Proceeding from the present method, the natural frequencies of two-span steel-concrete composite continuous beams with different span-ratios (0.53, 0.73, 0.85, 1) and different shear connection stiffnesses on the interface are calculated. The influence pattern of interfacial stiffness on bending vibration frequency was found. With the decrease of shear connection stiffness on the interface, the flexural vibration frequencies decrease obviously. And the influence on low order modes is more obvious while the reduction degree of high order is more sizeable. The real natural frequencies of partial-interaction continuous beams commonly used could have a 20% to 40% reduction compared with the fully-interaction ones. Furthermore, the reduction-ratios of natural frequencies for different span-ratios two-span composite beams with uniform shear connection stiffnesses are totally the same. The span-ratio mainly impacts on the mode shape. Four kinds of shear connection stiffnesses of steel-concrete composite continuous beams are calculated and compared with the experimental data and the FEM results. The calculated results using the proposed method agree well with the experimental and FEM ones on the low order modes which mainly determine the vibration properties.

• Steel and Composite Structures
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• 제2권5호
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• pp.315-330
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• 2002

This paper proposes a model for analysing the non-linear behaviour of steel concrete composite beams prestressed by external slipping cables, taking into account the deformability of the interface shear connection. By assuming a suitable admissible displacement field for the composite beam, the balance condition is obtained by the virtual work principle. The solution is numerically achieved by approximating the unknown displacement functions as series of shape functions according to the Ritz method. The model is applied to real cases by showing the consequences of different connection levels between the concrete slab and the steel beam. Particular attention is focused on the limited ductility of the shear connection that may be the cause of premature failure of the composite girder.

• Composites Research
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• 제25권6호
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• pp.211-216
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• 2012

광섬유센서는 구조물에 매립 또는 부착시 전단응력에 의해 편광이 발생하여 피크가 2개로 갈라질 수 있기 때문에 센서는 보호되고 양 끝단을 고정하는 방법으로 패키징을 하여야 하나, 광섬유의 클래딩 부분을 부착하는 방식으로 고정하면, 변형발생시 광케이블을 구성하는 코어와 클래딩 사이에서 미끄러짐 현상이 발생하기 때문에 이를 방지하기위해 센서의 양 끝단에 고정구를 사용하고 광섬유를 부분탈피하여 부착하여 접점을 만들어 줌으로써 외력에 의해 발생하는 변형을 정확하게 측정이 가능하도록 하였다. 그리고 기존 광섬유격자센서가 자체적으로 압축변형의 측정이 곤란한 점을 개선하기위해 미리 긴장(Pre-Strain)상태를 유지하기 위하여 두 개의 접점사이를 볼트와 너트로 조절하여 프리스트레인 가변이 가능하도록 하여 인장/압축변형 측정을 가능하게 한 광섬유격자센서 패키지를 제작하였다. 이러한 광섬유격자센서패키지를 실제구조물에 적용하여 측정하였으며, 이를 통하여 안전을 감시하는 모니터링시스템에 적용할 수 있도록 하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.797-802
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• 1997

The current study is a part of series o research about the development of new superstructure system to overcome the engineering problems in the design of bridges of 30m to 45m in span length using the existing bridge systems. The basic concept of new system is the continuation of adjacent tow simple spans composed of the precast prestressed concrete U-type sections. The partial post tensioning method is applied to create the continuity. In this study, the new technique was introduced and applied with an example design of tow span of 40m in span length to find the possibility for practical application as the feasibility study. The obtained results show that the new splicing method is expected to offer significant economical and serviceability advantages.

• 콘크리트학회논문집
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• 제12권6호
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• pp.43-50
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• 2000

In this paper, a new splicing method was applied to design the girder section of bridges with the span length of 25m, 30m, 35m, 40m and 45m. A U-type precast prestressed section was also determined for each bridge. Additionally, the sectional area, beam depth and Guyon's efficiency factor of the spliced U-type sections in each span were analyzed in comparison with the present I-type PSC bridges. As a result, in spite of an increase of 31%∼50% in the sectional areas compared with the I-type precast girders, the spliced U-type the beam depth of the spliced U-type girder was designed as 2,050 mm compared with the I-type precast girder of 2,600mm in a 40m span bridge. The sectional efficiency factors of the spliced U-type sections were analyzed as 0.76∼0.99. It shows that the spliced U-type sections ar of a superior structural efficiency in contrast to the average sectional efficiency factor of 0.66 value in the I-type girders.

• Smart Structures and Systems
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• 제31권3호
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• pp.229-245
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• 2023

The absence of excitation measurements may pose a big challenge in the application of structural damage identification owing to the fact that substantial effort is needed to reconstruct or identify unknown input force. To address this issue, in this paper, an iterative strategy, a synergy of Tikhonov regularization method for force identification and modified Jaya algorithm (M-Jaya) for stiffness parameter identification, is developed for damage identification with partial output-only responses. On the one hand, the probabilistic clustering learning technique and nonlinear updating equation are introduced to improve the performance of standard Jaya algorithm. On the other hand, to deal with the difficulty of selection the appropriate regularization parameters in traditional Tikhonov regularization, an improved L-curve method based on B-spline interpolation function is presented. The applicability and effectiveness of the iterative strategy for simultaneous identification of structural damages and unknown input excitation is validated by numerical simulation on a 21-bar truss structure subjected to ambient excitation under noise free and contaminated measurements cases, as well as a series of experimental tests on a five-floor steel frame structure excited by sinusoidal force. The results from these numerical and experimental studies demonstrate that the proposed identification strategy can accurately and effectively identify damage locations and extents without the requirement of force measurements. The proposed M-Jaya algorithm provides more satisfactory performance than genetic algorithm, Gaussian bare-bones artificial bee colony and Jaya algorithm.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표대회 논문집(III)
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• pp.656-661
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• 1998

This paper presents a method of statistical analysis and sensitivity analysis of creep and shrinkage effects in PSC box girder bridges. The statistical and sensitivity analyses are performed by using the numerical simulation of Latin Hypercube sampling. For each sample, the time-dependent structural analysis is performed to produce response data, which are then statistically analyzed. The probabilistic prediction of the confidence limits on long-term effects of creep and shrinkage is then expressed. Three measures are examined to quantify the sensitivity of the outputs to each of the input variables. These are rank correlation coefficient(RCC), partial rank correlation coefficient(PRCC) and standardized rank regression coefficient(SRRC) computed on the ranks of the observations. Probability band widens with time, which indicates an increase of prediction uncertainty with time. The creep model uncertainty factor and the relative humidity appear as the most dominant factors with regard to the model output uncertainty.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.309-312
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• 2008

철근콘크리트구조(RC)는 경제성이 뛰어나 가장 널리 사용되고 있지만, 인장응력에 취약하고 콘크리트의 자중이 커서 처짐 제어가 어렵다는 단점이 있다. 프리스트레스트콘크리트구조는 이를 극복할 수 있는 가장 효율적인 방법으로 이미 오래전부터 알려져 있지만 국내에서는 건축 현장 여건 때문에 적용사례가 매우 드물다. 특히, 대부분 부정정 구조물인 건축물에 적합하면서 일체성을 확보할 수 있는 포스트텐션(PT) 공법은 국내에서는 최근에서야 비로소 몇몇 건축 현장에 도입하기 시작하였다. 그러나 전구간 포스트텐션 공법을 적용하는 것에는 현장여건상 여전히 많은 엔지니어들이 부담을 가지고 있는 것이 현실이다. 따라서 본 연구에서는 RC구조의 처짐억제 효율성을 높이면서도 현장 실무자들에게 부담을 최소화 할 수 있는 현실적 대안으로 부분 구간에만 PT공법을 적용시키는 방법을 제안하고 거동 특성을 분석하였다. 본 연구에서는 부분 구간PT공법의 적용성을 높이기 위하여 상향긴장방식을 적용하였으며, 실제 현장적용을 통하여 얻은 계측값과 해석결과의 비교를 통하여 거동 특성을 분석하였다.