포스트텐션 조립식 교각의 유효프리스트레스 크기 결정

심창수,Koem, Chandara 한국지진공학회 2016 한국지진공학회논문집 Vol.20 No.3

In this paper, a design concept of post-tensioned precast bridge piers was proposed to improve seismic behavior of the bridge pier. Mild reinforcing bars are placed continuously along the height of the column. Prestressing tendons are also provided to obtain re-centering capability for seismic events. Arrangement of the axial steels to prevent buckling of rebars at plastic hinge region was suggested and enhanced seismic performance was verified by experiments. Moment-curvature analyses were performed to evaluate the effect of effective prestress on seismic behavior after verifying the calculation method by cyclic tests of the precast columns. A real bridge pier was designed to investigate the seismic performance according to different level of effective prestress. Level of effective prestress showed obvious effect on crushing displacement but negligible effect on lateral displacement at fracture of tendons and reinforcements.

Numerical analysis of second-order effects of externally prestressed concrete beams

Tiejiong Lou,Yiqiang Xiang 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.5

A numerical procedure for the geometrical and material nonlinear analysis of concrete beams prestressed with external tendons is described, where the effects of external prestressing are treated as the equivalent loads applied on the concrete beams. The geometrical nonlinearity is considered not only the eccentricity variations of external tendons (second-order effects) but also the large displacement effects of the structure. The numerical method can predict the nonlinear response of externally prestressed concrete beams throughout the entire loading history with considerable accuracy. An evaluation of second-order effects of externally prestressed concrete beams is carried out using the proposed analysis. The analysis shows that the second-order effects have significant influence on the response characteristics of externally prestressed concrete beams. They lead to inferior ultimate load and strength capacities and a lower ultimate stress increase in tendons. Based on the current analysis, it is recommended that, for simplysupported externally prestressed beams with straight horizontal tendons, one deviator at midspan instead of two deviators at one-third span be furnished to minimize these effects.

Numerical analysis of second-order effects of externally prestressed concrete beams

Lou, Tiejiong,Xiang, Yiqiang Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.5

A numerical procedure for the geometrical and material nonlinear analysis of concrete beams prestressed with external tendons is described, where the effects of external prestressing are treated as the equivalent loads applied on the concrete beams. The geometrical nonlinearity is considered not only the eccentricity variations of external tendons (second-order effects) but also the large displacement effects of the structure. The numerical method can predict the nonlinear response of externally prestressed concrete beams throughout the entire loading history with considerable accuracy. An evaluation of second-order effects of externally prestressed concrete beams is carried out using the proposed analysis. The analysis shows that the second-order effects have significant influence on the response characteristics of externally prestressed concrete beams. They lead to inferior ultimate load and strength capacities and a lower ultimate stress increase in tendons. Based on the current analysis, it is recommended that, for simply-supported externally prestressed beams with straight horizontal tendons, one deviator at midspan instead of two deviators at one-third span be furnished to minimize these effects.

Temperature effect on wireless impedance monitoring in tendon anchorage of prestressed concrete girder

Park, Jae-Hyung,Huynh, Thanh-Canh,Kim, Jeong-Tae Techno-Press 2015 Smart Structures and Systems, An International Jou Vol.15 No.4

In this study, the effect of temperature variation on the wireless impedance monitoring is analyzed for the tendon-anchorage connection of the prestressed concrete girder. Firstly, three impedance features, which are peak frequency, root mean square deviation (RMSD) index, and correlation coefficient (CC) index, are selected to estimate the effects of temperature variation and prestress-loss on impedance signatures. Secondly, wireless impedance tests are performed on the tendon-anchorage connection for which a series of temperature variation and prestress-loss events are simulated. Thirdly, the effect of temperature variation on impedance signatures measured from the tendon-anchorage connection is estimated by the three impedance features. Finally, the effect of prestress-loss on impedance signatures is also estimated by the three impedance features. The relative effects of temperature variation and prestress-loss are comparatively examined.

Temperature effect on wireless impedance monitoring in tendon anchorage of prestressed concrete girder

박재형,Thanh-Canh Huynh,김정태 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.15 No.4

In this study, the effect of temperature variation on the wireless impedance monitoring isanalyzed for the tendon-anchorage connection of the prestressed concrete girder. Firstly, three impedancefeatures, which are peak frequency, root mean square deviation (RMSD) index, and correlation coefficient(CC) index, are selected to estimate the effects of temperature variation and prestress-loss on impedancesignatures. Secondly, wireless impedance tests are performed on the tendon-anchorage connection for whicha series of temperature variation and prestress-loss events are simulated. Thirdly, the effect of temperaturevariation on impedance signatures measured from the tendon-anchorage connection is estimated by the threeimpedance features. Finally, the effect of prestress-loss on impedance signatures is also estimated by thethree impedance features. The relative effects of temperature variation and prestress-loss are comparativelyexamined.

PCA-based filtering of temperature effect on impedance monitoring in prestressed tendon anchorage

Huynh, Thanh-Canh,Dang, Ngoc-Loi,Kim, Jeong-Tae Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.22 No.1

For the long-term structural health monitoring of civil structures, the effect of ambient temperature variation has been regarded as one of the critical issues. In this study, a principal component analysis (PCA)-based algorithm is proposed to filter out temperature effects on electromechanical impedance (EMI) monitoring of prestressed tendon anchorages. Firstly, the EMI monitoring via a piezoelectric interface device is described for prestress-loss detection in the tendon anchorage system. Secondly, the PCA-based temperature filtering algorithm tailored to the EMI monitoring of the prestressed tendon anchorage is outlined. The proposed algorithm utilizes the damage-sensitive features obtained from sub-ranges of the EMI data to establish the PCA-based filter model. Finally, the feasibility of the PCA-based algorithm is experimentally evaluated by distinguishing temperature changes from prestress-loss events in a prestressed concrete girder. The accuracy of the prestress-loss detection results is discussed with respect to the EMI features before and after the temperature filtering.

Compensation of temperature effect on impedance responses of PZT interface for prestress-loss monitoring in PSC girders

Thanh-Canh Huynh,Jeong-Tae Kim 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.17 No.6

In this study, a method to compensate the effect of temperature variation on impedance responses which are used for prestress-loss monitoring in prestressed concrete (PSC) girders is presented. Firstly, an impedance-based technique using a mountable lead-zirconate-titanate (PZT) interface is presented for prestress-loss monitoring in the local tendon-anchorage member. Secondly, a cross-correlation-based algorithm to compensate the effect of temperature variation in the impedance signatures is outlined. Thirdly, lab-scale experiments are performed on a PSC girder instrumented with a mountable PZT interface at the tendon-anchorage. A series of temperature variation and prestress-loss events are simulated for the lab-scale PSC girder. Finally, the feasibility of the proposed method is experimentally verified for prestress-loss monitoring in the PSC girder under temperature-varying conditions and prestress-loss events.

PCA-based filtering of temperature effect on impedance monitoring in prestressed tendon anchorage

Thanh-Canh Huynh,Ngoc-Loi Dang,Jeong-Tae Kim 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.22 No.1

For the long-term structural health monitoring of civil structures, the effect of ambient temperature variation has been regarded as one of the critical issues. In this study, a principal component analysis (PCA)-based algorithm is proposed to filter out temperature effects on electromechanical impedance (EMI) monitoring of prestressed tendon anchorages. Firstly, the EMI monitoring via a piezoelectric interface device is described for prestress-loss detection in the tendon anchorage system. Secondly, the PCA-based temperature filtering algorithm tailored to the EMI monitoring of the prestressed tendon anchorage is outlined. The proposed algorithm utilizes the damage-sensitive features obtained from sub-ranges of the EMI data to establish the PCA-based filter model. Finally, the feasibility of the PCA-based algorithm is experimentally evaluated by distinguishing temperature changes from prestress-loss events in a prestressed concrete girder. The accuracy of the prestress-loss detection results is discussed with respect to the EMI features before and after the temperature filtering.

Shear-lag behavior of prestressed concrete box-girder bridges during balanced cantilever construction

Zhong, Xingu,Zhang, Tianyu,Shu, Xiaojuan,Xu, Hongliang Techno-Press 2017 Advances in concrete construction Vol.5 No.5

Balanced cantilever construction is extensively used in the construction of prestressed concrete (PSC) box-girder bridges. Shear-lag effect is usually considered in finished bridges, while the cumulative shear-lag effect in bridges during balanced cantilever construction is considered only rarely. In this paper, based on the balanced cantilever construction sequences of large-span PSC box-girder bridges, the difference method is employed to analyze the cumulative shear-lag effect of box girders with varying depth under the concrete segments' own weight. During cantilever construction, no negative shear-lag effect is generated, and the cumulative shear-lag effect under the balanced construction procedure is greater than the instantaneous shear-lag effect in which the full dead weight is applied to the entire cantilever. Three cross-sections of Jianjiang Bridge were chosen for the experimental observation of shear-lag effect, and the experimental results are in keeping with the theoretical results of cumulative shear-lag effect. The research indicates that only calculating the instantaneous shear-lag effect is not sufficiently safe for practical engineering purposes.

포스트텐션 조립식 교각의 유효프리스트레스 크기 결정

심창수,코엠찬다라 한국지진공학회 2016 한국지진공학회논문집 Vol.20 No.3

In this paper, a design concept of post-tensioned precast bridge piers was proposed to improve seismic behavior of the bridge pier. Mild reinforcing bars are placed continuously along the height of the column. Prestressing tendons are also provided to obtain re-centering capability for seismic events. Arrangement of the axial steels to prevent buckling of rebars at plastic hinge region was suggested and enhanced seismic performance was verified by experiments. Moment-curvature analyses were performed to evaluate the effect of effective prestress on seismic behavior after verifying the calculation method by cyclic tests of the precast columns. A real bridge pier was designed to investigate the seismic performance according to different level of effective prestress. Level of effective prestress showed obvious effect on crushing displacement but negligible effect on lateral displacement at fracture of tendons and reinforcements.