• Title/Summary/Keyword: existing structures

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Safety factor calibration for bridge concrete girders

  • Silva, Rita C.;Cremona, Christian
    • Structural Engineering and Mechanics
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    • v.49 no.2
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    • pp.163-182
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    • 2014
  • Safety factors proposed in codes CEB, B.A.E.L 91 and EUROCODE 1 cover a great number of uncertainties; making them inadequate for the assessment of existing structures. Suitable safety factors are established using a probabilistic assessment, once real dimensions, materials strength and existing structures deterioration mechanisms are taken into account. This paper presents a calibration method for safety factors using a typical set of RC bridges in France. It considers the principal stages of corrosion provoked by $CO_2$ and $Cl^-$ penetration and threshold indexes (${\beta}_0$) for existing structures. Reliability indexes are determined by the FORM method in the calibration method.

Damage Assessment of Existing Structures by System Identification (SI법에 의한 기설구조물의 손상평가)

  • Lee, Hee-Up;Yang, Chang-Hyun;Park, Moon-Suk
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.3 no.1
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    • pp.179-184
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    • 1999
  • In this study, a method for damage assessment of existing structures is suggested using system identification approach. The natural frequencies of damaged structures are utilized to determine the size of damage. The SUMT algorithm is used to minimize error of the criterion function. The structural analysis is performed by using finite element method. Numerical examples are carried out to verify the validity of the proposed method and its computational procedures. And damage estimation of PSC beam is performed to demonstrate the effectiveness of the proposed method. From the results, it is found that the proposed SI method can be applied to estimate damage in existing structures accurately and rapidly.

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Particle filter for model updating and reliability estimation of existing structures

  • Yoshida, Ikumasa;Akiyama, Mitsuyoshi
    • Smart Structures and Systems
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    • v.11 no.1
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    • pp.103-122
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    • 2013
  • It is essential to update the model with reflecting observation or inspection data for reliability estimation of existing structures. Authors proposed updated reliability analysis by using Particle Filter. We discuss how to apply the proposed method through numerical examples on reinforced concrete structures after verification of the method with hypothetical linear Gaussian problem. Reinforced concrete structures in a marine environment deteriorate with time due to chloride-induced corrosion of reinforcing bars. In the case of existing structures, it is essential to monitor the current condition such as chloride-induced corrosion and to reflect it to rational maintenance with consideration of the uncertainty. In this context, updated reliability estimation of a structure provides useful information for the rational decision. Accuracy estimation is also one of the important issues when Monte Carlo approach such as Particle Filter is adopted. Especially Particle Filter approach has a problem known as degeneracy. Effective sample size is introduced to predict the covariance of variance of limit state exceeding probabilities calculated by Particle Filter. Its validity is shown by the numerical experiments.

Non-linear performance analysis of existing and concentric braced steel structures

  • Erdem, R. Tugrul
    • Steel and Composite Structures
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    • v.19 no.1
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    • pp.59-74
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    • 2015
  • Since there are several places located in active seismic zones in the world, serious damages and losses have happened due to major scaled earthquakes. Especially, structures having different irregularities have been severely damaged or collapsed during these seismic events. Behavior of existing structures under several loading conditions is not completely determined due to some uncertainties. This situation reveals the importance of design and analysis of structures under seismic effects. Several non-linear static procedures have been developed in recent years. Determination of the seismic safety of the existing structures and strengthening techniques are significant civil engineering problems Non-linear methods are defined in codes to determine the performance levels of structures more accurately. However, displacement based ones give more realistic results. These methods provide more reliable evaluation possibilities for existing structures with developing computer technology. In this study, non-linear performance analysis of existing and strengthened steel structures by X shaped bracing members with 3, 5 and 7 stories which have soft story irregularity is performed according to FEMA-356 and Turkish Earthquake Code-2007. Damage ratios of the structural members and global performance levels are determined as well as modal properties and story drift ratios after non-linear finite elements analysis for each structure.

An Experimental Study on the Increase of the Bearing Capacity on Sandy Ground due to Micropile Reinforcement (마이크로파일로 보강된 모래지반의 지지력 증가효과에 관한 실험적 연구)

  • 김정동;임종철;이태형
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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    • pp.411-416
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    • 2003
  • As rapid industrialization continues in these days, construction in the down town areas increases. Since constructions are performed around old and existing structures, the need to provide reinforcements to protect the existing structures from collapse and damage arises. Furthermore, if the construction is to take place in the down town area, difficult work space and damage caused by noise, vibration and collapse of structure can't be ignored. Among the remedial measures available today, micropile reinforcement is considered the best method to remedy these problems. But up to the present the characteristics of micropiles and ground behaviour has not been proven and no standard design is not yet available. Therefore, most design are performed based on previous experiences. In this study, the difference in the bearing capacity with changing reinforcement angle, space and sphere around foundation was monitored. These results were induced to broaden heighten the limits of micropile application.

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A Study on the Strength Characteristics of Concrete Cores (콘크리트 코어의 강도특성에 관한 연구)

  • 권영웅;이성용;신정식;전익찬;김민수;박송철
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.10a
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    • pp.85-90
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    • 2002
  • This paper concerns the within test strength of concrete cured under different conditions. Those conditions are water curing, field curing and cores drilled from the existing structures. The test factors are not only above cured conditions but also concrete ages of 3, 7, 14 and 28 days and concrete strength of 202, 252 and 650kgf/$\textrm{cm}^2$. The test results are as follows; (1) In spite of within test results, concrete strength is very different from curing states of concrete (2) The strength of cores drilled from existing structures are smaller than the strength of concrete cured in water by 3~4% and larger than that of concrete cured in field by 8~17% (3) Core strength is largely dependant on the curing state of top surface of concrete.

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