• Steel and Composite Structures
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• v.30 no.6
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• pp.535-550
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• 2019

Prestressed concrete (PC) bridges using corrugated steel webbing have emerged as one of the most promising forms of steel-concrete composite bridge. However, their long-term behavior is not well understood, especially in the case of large-span bridges. In order to study the time-dependent performance, a large three-span PC bridge with corrugated steel webbing was compared to a similar conventional PC bridge to examine their respective time-dependent characteristics. In addition, a three-dimensional finite element method with step-by-step time integration that takes into account cantilever construction procedures was used to predict long-term behaviors such as deflection, stress distribution and prestressing loss. These predictions were based upon four well-established empirical creep prediction models. PC bridges with a corrugated steel web were observed to have a better long-term performance relative to conventional PC bridges. In particular, it is noted that the pre-cambering for PC bridges with a corrugated steel web could be smaller than that of conventional PC bridges. The ratio of side-to-mid span has great influence on the long-term deformation of PC bridges with a corrugated steel web, and it is suggested that the design value should be between 0.4 and 0.6. However, the different creep prediction models still showed a weak homogeneity, thus, the further experimental research and the development of health monitoring systems are required to further progress our understanding of the long-term behavior of PC bridges with corrugated steel webbing.

• Journal of the Korean Society of Hazard Mitigation
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• v.1 no.2 s.2
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• pp.93-101
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• 2001

The objective of this study is to derive a shrinkage correction formula that considers temperature effect and to develop a methodology for the improved prediction of the long-term behavior of the FCM bridges by considering seasonal temperature variations in-situ. Thereby, current formulation were performed by using the actual experimental shrinkage data including seasonal temperature variation. The investigation of the long-term behavior of the FCM bridge was performed on the construction site in order to decide applicability of the shrinkage formula Numerical results by the general method indicates inaccurate values of total strain when considering real strain, whereas the applied method demonstrates a good agreement in the resultant strain. In consequently, the applied method will improve the prediction of the long-term deformation of the FCM Bridges.

• Journal of the Korean Geosynthetics Society
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• v.10 no.4
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• pp.105-112
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• 2011

This paper presents the numerical modelling technique for modeling the time-dependent behavior of geosynthetic reinforced soil wall under a sustained load. The applicability of power law-based creep models for modeling the creep deformations of geogrid and reinforced soil was first examined. The modeling approach was then used to simulate the long-term performance of a geosynthetic reinforced soil wall used in a bridge abutment. The results indicated that the power law-based models can be effectively used for modelling the long term behavior of geosynthetic reinforced walls under sustained loading. In addition, it was shown that, when using creep deformation susceptible backfill soils, the abutment wall and the sill beam may experience deformations exceeding allowable limits. Practical implications of the findings from this study are discussed in great detail.

• Geomechanics and Engineering
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• v.11 no.4
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• pp.531-552
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• 2016

The greenschist in the Jinping II Hydropower Station in southwest China exhibits continuous creep behaviour because of the geological conditions in the region. This phenomenon illustrates the time-dependent deformation and progressive damage that occurs after excavation. In this study, the responses of greenschist to stress over time were determined in a series of laboratory tests on samples collected from the access tunnel walls at the construction site. The results showed that the greenschist presented time-dependent behaviour under long-term loading. The samples generally experienced two stages: transient creep and steady creep, but no accelerating creep. The periods of transient creep and steady creep increased with increasing stress levels. The long-term strength of the greenschist was identified based on the variation of creep strain and creep rate. The ratio of long-term strength to conventional strength was around 80% and did not vary much with confining pressures. A quantitative method for predicting the failure period of greenschist, based on analysis of the stress-strain curve, is presented and implemented. At a confining pressure of 40 MPa, greenschist was predicted to fail in 5000 days under a stress of 290 MPa and to fail in 85 days under the stress of 320 MPa, indicating that the long-term strength identified by the creep rate and creep strain is a reliable estimate.

• Steel and Composite Structures
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• v.28 no.1
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• pp.39-49
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• 2018

The concrete bridge decks are usually precast and in-situ assembled with steel girders with post-pouring joint in the construction practice of super-wide steel-concrete composite beam. But the difference of concrete age between the precast slabs and the post-pouring joint has been not yet considered for the long-term performance analysis of this kind composite beam. A simply supported precast-assembled T-shaped beam was taken as an example to analyze the long-term performance of steel-concrete composite beam with post-pouring joint. Based on the deformation coordination conditions of the old-new concrete deck and steel girder, a theoretical model for the long-term behavior of precast-assembled composite beam is proposed in this paper according to age-adjusted effective modulus method. Then, the feasibility of the proposed model is verified by the available test data from the Gilbert's composite beams. Parametric studies were preformed to evaluate the influences of the cross-sectional area ratio of the post-pouring joint to the whole bridge deck, as well as the difference of concrete age between the precast slabs and the post-pouring joint, on the long-term performance of the composite beam. The results indicate that the traditional method without considering the age difference would seriously underestimate the effect of creep and shrinkage of concrete bridge decks. The concrete age difference between the precast slabs and the post-pouring joint should be demonstrated for the life cycle design and long-term performance analysis of precast-assembled steel-concrete composite beams.

• Smart Structures and Systems
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• v.33 no.6
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• pp.399-414
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• 2024

This study discusses the long-term deformation monitoring and shape sensing of bridge girder surfaces with an automated extraction scheme for point clouds in the Region Of Interest (ROI), invariant to the position of a Light Detection And Ranging system (LiDAR). Advanced smart construction necessitates continuous monitoring of the deformation and shape of bridge girders during the construction phase. An automated scheme is proposed for reconstructing geometric model of ROI in the presence of noisy non-stationary background. The proposed scheme involves (i) denoising irrelevant background point clouds using dimensions from the design model, (ii) extracting the outer boundaries of the bridge girder by transforming and processing the point cloud data in a two-dimensional image space, (iii) extracting topology of pre-defined targets using the modified Otsu method, (iv) registering the point clouds to a common reference frame or design coordinate using extracted predefined targets placed outside ROI, and (v) defining the bounding box in the point clouds using corresponding dimensional information of the bridge girder and abutments from the design model. The surface-fitted reconstructed geometric model in the ROI is superposed consistently over a long period to monitor bridge shape and derive deflection during the construction phase, which is highly correlated. The proposed scheme of combining 2D-3D with the design model overcomes the sensitivity of 3D point cloud registration to initial match, which often leads to a local extremum.

• Coupled systems mechanics
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• v.3 no.1
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• pp.27-52
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• 2014

For landfill monitoring and aftercare, long-term prognoses of emission and deformation behaviour are required. Landfills may be considered as heterogeneous porous soil-like structures, in which flow and transport processes of gases and liquids interact with local material degradation and mechanical deformation of the solid skeleton. Therefore, in the framework of continuous porous media mechanics a model is developed that permits the investigation of coupled mechanical, hydraulical and biochemical processes in municipal solid waste landfills.

• Geomechanics and Engineering
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• v.2 no.2
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• pp.107-123
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• 2010

Ground settlements and pore pressure changes were monitored around a shallow tunnel constructed in clay till during the excavation and primary lining installation. The settlements above the tunnel continued to develop for up to 100 days after the primary lining installation. Triaxial compression tests were carried out to estimate the short-term and long-term deformation characteristics of the till. Numerical simulation was conducted to history match the field measurements, and thus, to quantify the settlements induced by ground stress relief, consolidation and creep. It was found that the surface settlements due to ground stress relief, consolidation and creep are 17, 12 and 71% of total settlement (about 44 mm), respectively. In addition, early installation of rigid concrete lining could be an effective means to reduce the settlement due to creep.

• Journal of the Korean Graphic Arts Communication Society
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• v.30 no.3
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• pp.77-88
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• 2012

In this report, we performed the measurements of physical properties of optical discs as a long term preservation electronic recording device and showed how to improve the preservation method of them. We collect the 1,993 optical discs from the archives of the National Archives of Korea and tested various measurements. We used DVDT-SD4 equipment to measure the quality of data, deformation of disc, the various writing strategy and manufacturer derives, which can be happened in optical discs by physical factors. We found that th quality of data are closely related with write strategy between discs and drives. This relation gives us information about data quality in optical discs for long term preservation that can be obtained from the state between empty discs and optical drives before recording. Thus, the initial selection of optimal discs and drives is critical for long term recording data preservation and the data quality after long time preservation will not be much different from that of the initial ones.

• Proceedings of the Korean Fiber Society Conference
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• 2007.11a
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• pp.401-402
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• 2007

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