GNSS technology (known especially for GPS satellites) for measurement of deflections has proved very efficient and useful in bridge structural monitoring, even for short stiff bridges, especially after the advent of 100 Hz GNSS sensors. Mode computation from dynamic deflections has been proposed as one of the applications of this technology. Apart from formal modal analyses with GNSS input, and from spectral analysis of controlled free attenuating oscillations, it has been argued that simple spectra of deflections can define more than one modal frequencies. To test this scenario, we analyzed 21 controlled excitation events from a certain bridge monitoring survey, focusing on lateral and vertical deflections, recorded both by GNSS and an accelerometer. These events contain a transient and a following oscillation, and they are preceded and followed by intervals of quiescence and ambient vibrations. Spectra for each event, for the lateral and the vertical axis of the bridge, and for and each instrument (GNSS, accelerometer) were computed, normalized to their maximum value, and printed one over the other, in order to produce a single composite spectrum for each of the four sets. In these four sets, there was also marked the true value of modal frequency, derived from free attenuating oscillations. It was found that for high SNR (signal-to-noise ratio) deflections, spectral peaks in both acceleration and displacement spectra differ by up to 0.3 Hz from the true value. For low SNR, defections spectra do not match the true frequency, but acceleration spectra provide a low-precision estimate of the true frequency. This is because various excitation effects (traffic, wind etc.) contribute with numerous peaks in a wide range of frequencies. Reliable estimates of modal frequencies can hence be derived from deflections spectra only if excitation frequencies (mostly traffic and wind) can be filtered along with most measurement noise, on the basis of additional data.
{"title":"Modal frequencies of bridges from GNSS (GPS) monitoring data: Experimental, statistical evidence","authors":"S. Stiros, F. Moschas, P. Triantafyllidis","doi":"10.3233/BRS-210184","DOIUrl":"https://doi.org/10.3233/BRS-210184","url":null,"abstract":"GNSS technology (known especially for GPS satellites) for measurement of deflections has proved very efficient and useful in bridge structural monitoring, even for short stiff bridges, especially after the advent of 100 Hz GNSS sensors. Mode computation from dynamic deflections has been proposed as one of the applications of this technology. Apart from formal modal analyses with GNSS input, and from spectral analysis of controlled free attenuating oscillations, it has been argued that simple spectra of deflections can define more than one modal frequencies. To test this scenario, we analyzed 21 controlled excitation events from a certain bridge monitoring survey, focusing on lateral and vertical deflections, recorded both by GNSS and an accelerometer. These events contain a transient and a following oscillation, and they are preceded and followed by intervals of quiescence and ambient vibrations. Spectra for each event, for the lateral and the vertical axis of the bridge, and for and each instrument (GNSS, accelerometer) were computed, normalized to their maximum value, and printed one over the other, in order to produce a single composite spectrum for each of the four sets. In these four sets, there was also marked the true value of modal frequency, derived from free attenuating oscillations. It was found that for high SNR (signal-to-noise ratio) deflections, spectral peaks in both acceleration and displacement spectra differ by up to 0.3 Hz from the true value. For low SNR, defections spectra do not match the true frequency, but acceleration spectra provide a low-precision estimate of the true frequency. This is because various excitation effects (traffic, wind etc.) contribute with numerous peaks in a wide range of frequencies. Reliable estimates of modal frequencies can hence be derived from deflections spectra only if excitation frequencies (mostly traffic and wind) can be filtered along with most measurement noise, on the basis of additional data.","PeriodicalId":43279,"journal":{"name":"Bridge Structures","volume":"17 1","pages":"3-14"},"PeriodicalIF":0.6,"publicationDate":"2021-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/BRS-210184","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42624705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to study the influence of lateral impact on reinforced concrete piers in marine environment, drop hammer impact tests were carried out on piers with different corrosion rates obtained from drying-wetting cycle and chloride ion corrosion experiment to study the crack propagation process and failure modes of piers. Then by numerical simulation, the influences of impact velocity, impact mass, compressive strength of concrete and impact number on the performance of corroded piers were studied. The results showed that the failure modes of piers with different corrosion rates under lateral impact were different. The non-corrosive and low corrosion rate piers were destroyed by the bending shear which was jointly controlled by the transverse bending crack and oblique shear crack. The medium corrosion rate pier was the bending shear failure caused by oblique shear crack. The high corrosion rate pier was the joint action of bending shear crack and rust expansion crack. The increase of impact velocity, impact mass and impact number will increase the maximum deflection and the damage of the corroded piers, but the increase degrees were different. The increase was largest when the impact number was increased. Increasing impact number from 1 to 5, the maximum deflection increased by 26.3 times and the number of damage element increased by 4.3 times. Increasing the compressive strength of concrete will decrease the damage of pier, but with less degree. Increasing the compressive strength from 25 to 45 MPa, the maximum deflection and number of damage element were decreased by 10.7% and 9.4% respectively.
{"title":"Influence of lateral impact on reinforced concrete piers under drying-wetting cycle and chloride ion corrosion environment","authors":"W. Dong, C. Fang, S. Yang","doi":"10.3233/BRS-210186","DOIUrl":"https://doi.org/10.3233/BRS-210186","url":null,"abstract":"In order to study the influence of lateral impact on reinforced concrete piers in marine environment, drop hammer impact tests were carried out on piers with different corrosion rates obtained from drying-wetting cycle and chloride ion corrosion experiment to study the crack propagation process and failure modes of piers. Then by numerical simulation, the influences of impact velocity, impact mass, compressive strength of concrete and impact number on the performance of corroded piers were studied. The results showed that the failure modes of piers with different corrosion rates under lateral impact were different. The non-corrosive and low corrosion rate piers were destroyed by the bending shear which was jointly controlled by the transverse bending crack and oblique shear crack. The medium corrosion rate pier was the bending shear failure caused by oblique shear crack. The high corrosion rate pier was the joint action of bending shear crack and rust expansion crack. The increase of impact velocity, impact mass and impact number will increase the maximum deflection and the damage of the corroded piers, but the increase degrees were different. The increase was largest when the impact number was increased. Increasing impact number from 1 to 5, the maximum deflection increased by 26.3 times and the number of damage element increased by 4.3 times. Increasing the compressive strength of concrete will decrease the damage of pier, but with less degree. Increasing the compressive strength from 25 to 45 MPa, the maximum deflection and number of damage element were decreased by 10.7% and 9.4% respectively.","PeriodicalId":43279,"journal":{"name":"Bridge Structures","volume":"17 1","pages":"51-64"},"PeriodicalIF":0.6,"publicationDate":"2021-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/BRS-210186","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41828116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The case-study of a steel bowstring bridge set in a marine environment and highly damaged by corrosion is presented. The bridge was built in 2004 and was repainted for corrosion protection in 2010. Despite the recent construction and the maintenance interventions, many structural elements like hangers are highly damaged by corrosion with decreasing performance in terms of serviceability and ultimate limit states. A deep investigation was carried out in order to assess the bridge and to establish the necessary retrofit actions to be carried out in the near future. In-situ tests reveal the reduced performance of the original steel in terms of strength and corrosion protection, together with the inefficiency of the successive maintenance interventions. The paper presents assessment of the bridge and retrofit measures, including replacement of the hangers and galvanization through thermal spray coating technology, in order to increase its service life. The results of the investigations and the intervention measures are outlined and discussed.
{"title":"Effects of corrosion on a steel bowstring bridge in marine environment: A case-study of assessment and retrofit","authors":"M. Granata","doi":"10.3233/BRS-200178","DOIUrl":"https://doi.org/10.3233/BRS-200178","url":null,"abstract":"The case-study of a steel bowstring bridge set in a marine environment and highly damaged by corrosion is presented. The bridge was built in 2004 and was repainted for corrosion protection in 2010. Despite the recent construction and the maintenance interventions, many structural elements like hangers are highly damaged by corrosion with decreasing performance in terms of serviceability and ultimate limit states. A deep investigation was carried out in order to assess the bridge and to establish the necessary retrofit actions to be carried out in the near future. In-situ tests reveal the reduced performance of the original steel in terms of strength and corrosion protection, together with the inefficiency of the successive maintenance interventions. The paper presents assessment of the bridge and retrofit measures, including replacement of the hangers and galvanization through thermal spray coating technology, in order to increase its service life. The results of the investigations and the intervention measures are outlined and discussed.","PeriodicalId":43279,"journal":{"name":"Bridge Structures","volume":"16 1","pages":"121-137"},"PeriodicalIF":0.6,"publicationDate":"2021-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/BRS-200178","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44392335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to improve the application effect of steel fiber reinforced concrete (SFRC) in road bridge construction, the mechanical properties of SFRC with different fiber content were analyzed. The SFRC specimens with 0%, 0.5%, 1%, 1.5% and 2% fiber content were designed, and the mechanical properties were tested. The results showed that the compressive strength first increased and then decreased with the increase of fiber content, and the maximum compressive strength of SFRC1.5 reached 40.86 MPa, increasing by 7.19%; the increase amplitude of tensile strength of SFRC1.5 was 73.04%, which was the most obvious; the flexural strength of SFRC increased with the increase of fiber content, and the flexural strength of SFRC2 was 9.78 MPa, increasing by 94.43%. It is concluded from the experimental results of a case study that SFRC1.5 presents the optimal overall mechanical properties and is more suitable for road bridge construction.
{"title":"Mechanical properties of steel fiber reinforced concrete material in construction of road bridge deck","authors":"Xiaohu Luo","doi":"10.3233/BRS-200180","DOIUrl":"https://doi.org/10.3233/BRS-200180","url":null,"abstract":"In order to improve the application effect of steel fiber reinforced concrete (SFRC) in road bridge construction, the mechanical properties of SFRC with different fiber content were analyzed. The SFRC specimens with 0%, 0.5%, 1%, 1.5% and 2% fiber content were designed, and the mechanical properties were tested. The results showed that the compressive strength first increased and then decreased with the increase of fiber content, and the maximum compressive strength of SFRC1.5 reached 40.86 MPa, increasing by 7.19%; the increase amplitude of tensile strength of SFRC1.5 was 73.04%, which was the most obvious; the flexural strength of SFRC increased with the increase of fiber content, and the flexural strength of SFRC2 was 9.78 MPa, increasing by 94.43%. It is concluded from the experimental results of a case study that SFRC1.5 presents the optimal overall mechanical properties and is more suitable for road bridge construction.","PeriodicalId":43279,"journal":{"name":"Bridge Structures","volume":"16 1","pages":"169-176"},"PeriodicalIF":0.6,"publicationDate":"2021-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/BRS-200180","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45842741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The reliability of condition assessment of bridges obtained from analysis of visual inspection data is always a big concern among structural engineers. It has been known that the condition grading of a bridge is very subjective and can convey limited information to the end user. To finalize and verify the reported condition grading, inspectors and bridge owners have mainly been relying on images. It has been known that the image observation may not be sufficient to address all kinds of problems associated with visual condition grading. The integration of practical supplemental measurements into condition grading as proposed in this paper will contribute to minimize the errors in visual inspection. Measurement of vehicle induced vibrations through wireless accelerometers can be used to determine the natural frequencies of the bridge that can be reported at each inspection. The change in frequencies can be an indication of deterioration in stiffness of bridge over the years. Taking concrete samples by chipping at the inspection site and analyzing them under scanning electron microscope (SEM) at the laboratory can be used to identify the current problems with concrete degradation. In this scope, the regular bridge inspection procedure with the proposed enhancements has been performed on field inspection of highway bridges in Turkey to determine the practicality of the quick supplemental measurements and to analyze the difference in grading of the three different inspectors with different level of experiences.
{"title":"Integration of practical supplemental measurements into bridge condition visual inspection grading","authors":"Nefize Shabana, Ö. Avşar, A. Caner","doi":"10.3233/BRS-200179","DOIUrl":"https://doi.org/10.3233/BRS-200179","url":null,"abstract":"The reliability of condition assessment of bridges obtained from analysis of visual inspection data is always a big concern among structural engineers. It has been known that the condition grading of a bridge is very subjective and can convey limited information to the end user. To finalize and verify the reported condition grading, inspectors and bridge owners have mainly been relying on images. It has been known that the image observation may not be sufficient to address all kinds of problems associated with visual condition grading. The integration of practical supplemental measurements into condition grading as proposed in this paper will contribute to minimize the errors in visual inspection. Measurement of vehicle induced vibrations through wireless accelerometers can be used to determine the natural frequencies of the bridge that can be reported at each inspection. The change in frequencies can be an indication of deterioration in stiffness of bridge over the years. Taking concrete samples by chipping at the inspection site and analyzing them under scanning electron microscope (SEM) at the laboratory can be used to identify the current problems with concrete degradation. In this scope, the regular bridge inspection procedure with the proposed enhancements has been performed on field inspection of highway bridges in Turkey to determine the practicality of the quick supplemental measurements and to analyze the difference in grading of the three different inspectors with different level of experiences.","PeriodicalId":43279,"journal":{"name":"Bridge Structures","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2021-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/BRS-200179","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46630034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Autonomous truck platoons shall soon be traveling our highway system with greater frequency. The objective of the presented study is to conduct a high-level evaluation of the Texas concrete bridge inventory when subjected to potential truck platoon loading. The National Bridge Inventory (NBI) database is utilized to the greatest extent possible. In addition, a significant literature review is performed to make assumptions allowing estimated load rating calculations for the prestressed concrete bridges likely to support future platoons (nearly 3,000 bridges). The truck platoon load ratings, combined with the NBI structural evaluation condition ratings, are utilized to prioritize each bridge. As a result, bridges are identified for more detailed evaluation prior to future truck platoon implementation. Data analysis was also performed to further understand the impact of various parameters on the load rating and prioritization results. Conclusions were drawn regarding the sensitivity of the (1) original design methodology, (2) bridge span length, (3) truck type, (4) truck spacing and (5) number of trucks within a platoon. In addition, a secondary benefit of the study is a presented framework for other bridge owners to prioritize their bridges that may be subjected to truck platoon or other heavy vehicle loading.
{"title":"Prioritization of Texas prestressed concrete bridges for future truck platoon loading","authors":"Nandhu Pillay Thulaseedharan, M. Yarnold","doi":"10.3233/BRS-210181","DOIUrl":"https://doi.org/10.3233/BRS-210181","url":null,"abstract":"Autonomous truck platoons shall soon be traveling our highway system with greater frequency. The objective of the presented study is to conduct a high-level evaluation of the Texas concrete bridge inventory when subjected to potential truck platoon loading. The National Bridge Inventory (NBI) database is utilized to the greatest extent possible. In addition, a significant literature review is performed to make assumptions allowing estimated load rating calculations for the prestressed concrete bridges likely to support future platoons (nearly 3,000 bridges). The truck platoon load ratings, combined with the NBI structural evaluation condition ratings, are utilized to prioritize each bridge. As a result, bridges are identified for more detailed evaluation prior to future truck platoon implementation. Data analysis was also performed to further understand the impact of various parameters on the load rating and prioritization results. Conclusions were drawn regarding the sensitivity of the (1) original design methodology, (2) bridge span length, (3) truck type, (4) truck spacing and (5) number of trucks within a platoon. In addition, a secondary benefit of the study is a presented framework for other bridge owners to prioritize their bridges that may be subjected to truck platoon or other heavy vehicle loading.","PeriodicalId":43279,"journal":{"name":"Bridge Structures","volume":"16 1","pages":"155-167"},"PeriodicalIF":0.6,"publicationDate":"2021-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/BRS-210181","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48053975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A super lightweight deck can enhance load rating and functionality of a bridge, especially those identified as structurally deficient. This study was aimed to develop and experimentally validate a novel bridge deck as an ultra-lightweight low-profile waffle slab of ultra-high-performance concrete (UHPC) with either carbon fiber reinforced polymer (CFRP) or high strength steel (HSS) reinforcement. The proposed system lends itself to accelerated bridge construction, rapid deck replacement in bridges with load restrictions, and bridge widening applications without the need to replace girders. Performance and failure modes of the proposed deck were initially assessed through extensive lab experiments and finite element analysis, which together confirmed that the proposed deck panel meets the AASHTO LRFD requirements. The proposed deck system is not susceptible to punching shear of its thin slab and fails in a rather ductile manner. To evaluate its long-term performance, the system was further tested under the dynamic impact of wheel load at the Accelerated Pavement Testing (APT) facility of the Florida Department of Transportation using a Heavy Vehicle Simulator (HVS).
{"title":"Accelerated testing of super lightweight UHPC waffle deck under heavy vehicle simulator","authors":"S. Ghasemi, A. Mirmiran, Yulin Xiao, K. Mackie","doi":"10.3233/BRS-200176","DOIUrl":"https://doi.org/10.3233/BRS-200176","url":null,"abstract":"A super lightweight deck can enhance load rating and functionality of a bridge, especially those identified as structurally deficient. This study was aimed to develop and experimentally validate a novel bridge deck as an ultra-lightweight low-profile waffle slab of ultra-high-performance concrete (UHPC) with either carbon fiber reinforced polymer (CFRP) or high strength steel (HSS) reinforcement. The proposed system lends itself to accelerated bridge construction, rapid deck replacement in bridges with load restrictions, and bridge widening applications without the need to replace girders. Performance and failure modes of the proposed deck were initially assessed through extensive lab experiments and finite element analysis, which together confirmed that the proposed deck panel meets the AASHTO LRFD requirements. The proposed deck system is not susceptible to punching shear of its thin slab and fails in a rather ductile manner. To evaluate its long-term performance, the system was further tested under the dynamic impact of wheel load at the Accelerated Pavement Testing (APT) facility of the Florida Department of Transportation using a Heavy Vehicle Simulator (HVS).","PeriodicalId":43279,"journal":{"name":"Bridge Structures","volume":"16 1","pages":"61-74"},"PeriodicalIF":0.6,"publicationDate":"2021-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/BRS-200176","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41663201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effects of combinations of different types of irregularities have not been studied in details in the past and current seismic design codes do not address this issue appropriately. In this research, 76 regular and irregular bridges with irregularities in both superstructure and substructure were designed and evaluated to investigate the impact of combinations of irregularities on the seismic ductility demands. The irregularity parameters considered in this study include irregularities in span arrangement, different lengths of columns, different abutments support conditions and different stiffness of superstructure. The bridges were designed and checked according to AASHTO provisions. Inelastic time history analysis was conducted using OpenSees software and ductility demands in bridge columns for different bridge configurations were predicted. Predictions of ductility demands were based on the mean responses obtained using a number of ground motion records. Finally, the effect of considering displacement directions in predicting the mean bridge response (i.e., using different methods for predicting the mean response) for irregular and regular bridges was investigated. The results indicate that the combinations of irregularities can significantly increase the ductility demands in some cases compared to the case of regular bridges.
{"title":"Investigating the effects of combinations of irregularities on seismic ductility demands and mean response for four-span RC bridges considering displacement direction","authors":"M. Sajed, P. Tehrani","doi":"10.3233/BRS-200173","DOIUrl":"https://doi.org/10.3233/BRS-200173","url":null,"abstract":"The effects of combinations of different types of irregularities have not been studied in details in the past and current seismic design codes do not address this issue appropriately. In this research, 76 regular and irregular bridges with irregularities in both superstructure and substructure were designed and evaluated to investigate the impact of combinations of irregularities on the seismic ductility demands. The irregularity parameters considered in this study include irregularities in span arrangement, different lengths of columns, different abutments support conditions and different stiffness of superstructure. The bridges were designed and checked according to AASHTO provisions. Inelastic time history analysis was conducted using OpenSees software and ductility demands in bridge columns for different bridge configurations were predicted. Predictions of ductility demands were based on the mean responses obtained using a number of ground motion records. Finally, the effect of considering displacement directions in predicting the mean bridge response (i.e., using different methods for predicting the mean response) for irregular and regular bridges was investigated. The results indicate that the combinations of irregularities can significantly increase the ductility demands in some cases compared to the case of regular bridges.","PeriodicalId":43279,"journal":{"name":"Bridge Structures","volume":"16 1","pages":"105-117"},"PeriodicalIF":0.6,"publicationDate":"2021-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/BRS-200173","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44620663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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