In order to better assess the condition of existing and new bridge systems it is necessary to und... more In order to better assess the condition of existing and new bridge systems it is necessary to understand how they would behave under loadings beyond elastic ranges. With about 30% of the 600,000 bridges in the country classified as structurally deficient or functionally obsolete, finding an accurate predictive method becomes a must. The main objectives of this study are (1) to demonstrate how the load distribution affects the behavior of each girder as the live load is increased up to the bridge’s ultimate capacity; (2) to understand bridge systems performance in inelastic stages; and (3) to predict the bridge’s ultimate capacity. A bridge was analyzed up to its failure under various loading conditions using a 3D finite element model. It was found that the only accurate method to determine load distribution at ultimate stages is through section moments. It was also found that the current bridge rating method underestimates considerably the analyzed bridge’s strength. These findings can potentially result in saving millions of dollars annually by avoiding unnecessary weight-limiting postings, rehabilitation or decommissioning and replacement.
Computational Modelling of Concrete Structures, 2014
ABSTRACT This paper deals with the constitutive modeling of Recycled Aggregate Concrete (RAC) in ... more ABSTRACT This paper deals with the constitutive modeling of Recycled Aggregate Concrete (RAC) in which natural coarse aggregates are partially or totally replaced by recycled concrete aggregates obtained from crushed hardened concrete. These aggregates, presenting greater porosity than natural ones, cause the degradation in elastic and strength properties of concrete when compared with standard concrete. The proposed constitutive model for RAC constitutes an extension of the Performance Dependent Model (PDM) by Folino and Etse (2012) which is based on the flow theory of plasticity. It depends on the three stress invariants, and includes a non associative flow rule, an anisotropic hardening law, and a fracture-energy based softening law. A key aspect of the PDM is the consideration of the so-called performed parameter, based on fundamental concrete properties, which plays a relevant roll in the strength and ductility features of concrete behavior. This feature turns the PDM particularly suitable to model failure behavior of RAC by performing the appropriated reformulations. After describing the PDM’s main features, an analysis of RAC’s response behavior and failure mechanism is performed, from which some fundamental material parameters are identified. Then, a reformulation of the PDM is presented to model mechanical behavior of RACs. Some comparisons between experimental results and numerical predictions with the proposed model of uniaxial and triaxial compression tests on RAC are presented to show the capabilities of the constitutive formulation in this work. Finally, some numerical tests are performed with the aim of exploring both, RAC’s failure behavior under mixed-mode of fracture, and the differences with that of standard concrete.
It is very challenging to capture the drag effects for the computational fluid dynamics numerical... more It is very challenging to capture the drag effects for the computational fluid dynamics numerical simulations of the urban canopy wind environment. This study proposed a novel canopy drag coefficient model for accurate analysis of the urban wind environment based on a large eddy simulation, where the drag coefficients varied with quantitatively identified canopy parameters along with the height. Four computational parameters, namely the average kinetic energy, turbulent kinetic energy, sub-grid scale turbulent kinetic energy, and sub-grid scale dissipation, were incorporated into the conventional drag coefficient. The Meixi Lake International Community in Changsha, China, was considered as a case study. The inlet boundary conditions were provided by the Weather Research and Forecasting model, and the proposed drag coefficient model was utilized to simulate the wind field characteristics. The results showed that the drag coefficient was relatively large near the ground, and it decrea...
Fiber reinforced polymers (FRP) have become more popular construction materials in the last decad... more Fiber reinforced polymers (FRP) have become more popular construction materials in the last decade due to the reduction of material costs. The installation and performance evaluation of the first FRP-wrapped balsa wood bridge in Louisiana is described in this document. A comprehensive instrumentation and loading test scheme is discussed and details are illustrated. The selected bridge structure in this demonstration project will potentially provide a new approach to enhancing the transportation infrastructure in Louisiana. The test bridge is the Pierre Part Bridge located on route LA 70 in Assumption Parish, Louisiana Department of Transportation and Development (LADOTD) District 61. The instrumentation consisted of regular strain gauges, fiber optic strain and temperature sensors, accelerometers, and acoustic emission sensors. The measured results from each of the gauges are summarized, and comparisons are made between the finite element models of the bridge structure and the field...
The scouring process excavates and carries away materials from the bed and banks of streams, and ... more The scouring process excavates and carries away materials from the bed and banks of streams, and from around the piers and abutments of bridges. Scour undermines bridges and may cause bridge failures due to structural instability. In the last 30 years, more than 1,000 bridges collapsed in the U.S. and about 60% of the failures are related to the scour of bridge foundations. Due to the difficulty in inspecting bridge scour, scour-induced failures tend to occur suddenly without prior warning or signs of distress to the structures. Owing to the threat of hurricane-induced flooding and the fact that there are a significant number of coastal and river/bayou bridges in Louisiana, a more reliable inspection and monitoring procedure for bridge scour is needed. This proposed study is to develop bridge scour monitoring techniques using fiber optic sensors. Based on theoretical and numerical studies, a few mechanisms were proposed for foundation scour monitoring and verified in laboratory test...
A discussion of a technical note with the aforementioned title by U. Starossek, published in this... more A discussion of a technical note with the aforementioned title by U. Starossek, published in this journal (Volume 124, Number 8, August 1998), is presented. In the discussers' opinion, when comparing real-number and complex-number expressions of aerodynamic forces for flutter analysis, the choice of using a real or complex number format should depend on whether the flutter derivatives or complex coefficients are more conveniently measured or predicted, since the discussers see no significant differences between them in terms of compactness and computation efficiency. Discussion is followed by closure from the author.
The traditional curing method of concrete members in China is through manual water curing based o... more The traditional curing method of concrete members in China is through manual water curing based on the experience of engineers and at an arbitrary time. This method, however, may induce early-age cracks and reduce durability of materials. In this paper, an automated curing system is proposed, which can decrease and even eliminate the early-age cracks by controlling the relative humidity and temperature of the concrete. More specifically, (1) the interval time of curing spray, calculated based on the cement hydration and real-time monitored data, is automatically identified by a programmable logic controller; and (2) the fog spray curing is operated under a constant water pressure by a variable frequency technology. A field test was conducted on 20 box-section beams to evaluate the performance of the proposed system based on the temperature evolution, humidity variation, and compressive strength of the concrete. Compared with the traditional manual water curing, the concrete beams cured by the automated system show higher early-age compressive strength, better appearance without 2 water stains, and no early-age cracks.
AbstractThis study investigates the effects of inhomogeneous wind fields on the aerostatic stabil... more AbstractThis study investigates the effects of inhomogeneous wind fields on the aerostatic stability of a long-span cable-stayed bridge, which straddles a typical mountain-gorge terrain. Inhomogene...
AbstractWind tunnel tests were conducted to investigate the wind pressure characteristics of sawt... more AbstractWind tunnel tests were conducted to investigate the wind pressure characteristics of sawtooth roofs in a simulated open country wind field with relatively low turbulence intensity. Models o...
Weigh-in-motion technology is an effective tool that has been extensively used to monitor traffic... more Weigh-in-motion technology is an effective tool that has been extensively used to monitor traffic on highways. Pavement-based weigh-in-motion systems usually have poor durability and will cause traffic interruption during their installation and maintenance process. The recently developed bridge weigh-in-motion technology provides a more convenient and cost-effective alternative to the pavement-based weigh-in-motion technology. Bridge weigh-in-motion systems can be installed without interrupting the traffic. Also, bridge weigh-in-motion systems have the potential to deliver better accuracy than pavement-based weigh-in-motion systems. Due to these significant advantages, the bridge weigh-in-motion technology has been playing an increasingly important role in bridge health monitoring and overweight truck enforcement, and many studies have been conducted to continuously improve the bridge weigh-in-motion technology. In this review, the common algorithms for bridge weigh-in-motion are di...
h i g h l i g h t s 28 specimens were tested to study the behavior of NSM FRP-to-concrete bonded ... more h i g h l i g h t s 28 specimens were tested to study the behavior of NSM FRP-to-concrete bonded joint. The bond performance of the interface increased with increasing concrete strength. The bond capacity of the interface increases with bond length until rupture of CFRP. The bond at the bonded joint degraded with a decrease in the edge distance. A residual friction stress exists at the bonded joint after debonding failure.
Practice Periodical on Structural Design and Construction, 2016
AbstractIn this paper, the solitary wave forces on a typical coastal bridge deck are evaluated nu... more AbstractIn this paper, the solitary wave forces on a typical coastal bridge deck are evaluated numerically based on a component level assessment, and the countermeasure of the air venting holes is investigated. At first, a wave model based on the second-order solitary wave theory is presented to represent the incident waves in tsunami events. The shear stress transport (SST) k-ω model is used as the turbulence closure for the Reynolds-averaged Navier-Stokes (RANS) equations. Then, the characteristics of the wave forces (the horizontal force, the vertical force, and the moment) considering three different still-water levels (SWLs) and four wave heights for each SWL are investigated, and the effects of the SWLs and wave heights are demonstrated. In addition, a component level–based assessment of the wave loadings, especially the overturning moment, varying along the wave propagation is conducted to enhance the understanding of the force distribution on the bridge deck. Finally, the countermeasure of the air...
One of the major drawbacks with most bridge weigh-in-motion (BWIM) methods that adopt the Moses a... more One of the major drawbacks with most bridge weigh-in-motion (BWIM) methods that adopt the Moses algorithm is the need for acquisition of vehicle speed and axle spacing by using additional devices, such as free-of-axle detectors. This study presents a novel virtual simply supported beam (VSSB) method, which uses weighing sensors to directly identify the speed and the axle spacing of passing vehicles on bridges, making it very desirable for commercial BWIM systems. Numerical simulations and model tests are carried out to study the effectiveness and accuracy of the proposed method. The results show that the proposed method can successfully identify the vehicle speed and axle spacing with good accuracy. The proposed method also proves reliable under noisy conditions.
AbstractBridge scour is a major cause of bridge failures and has emerged as a significant concern... more AbstractBridge scour is a major cause of bridge failures and has emerged as a significant concern for bridge engineers. Most studies focus on the scour mechanism, modeling, detecting and monitoring, and countermeasures. To detect or monitor the scour, the scour effect on the response and feature change of the bridge structure should be studied first to choose an effective measurement. Currently, very few studies have been performed on the scour consequences. Therefore, the present study investigated the scour effect on the responses of the entire bridge, including the superstructure and substructure, and even the responses of vehicles traveling on the bridge, which in turn could be used to detect or monitor the scour of foundations. A field bridge with scour history was adopted, and the bridge–vehicle–wave interaction was considered. First, the soil model, scour model, and wave loads were created. The free vibrations and dynamic analyses under wave loads were then conducted on a single pile and pile group...
All rights reserved. No part of this publication may be reproduced in any form or by any means, w... more All rights reserved. No part of this publication may be reproduced in any form or by any means, without the prior written permission of the Prestressed Concrete Institute. N ineteen seventy-nine was the 25-year Silver Jubilee of the founding of the Prestressed Concrete Institute. CONTENTS Part 6-Early History of Prestressed 163 Concrete in Colorado 'Ed Thwaits is now 85 years old and fives quietly in Denver, Colorado.
... Transportation Research Board Annual Meeting 2007 Paper #07-3492. Abstract: In order to bette... more ... Transportation Research Board Annual Meeting 2007 Paper #07-3492. Abstract: In order to better assess the condition of existing and new bridge systems it is necessary to understand how they would behave under loadings beyond elastic ranges. ... 15p. Authors: Araujo, Marcio. ...
Transportation Research Record: Journal of the Transportation Research Board, 2003
Stiffness and ultimate load-carrying capacities of glass fiber-reinforced polymer honeycomb sandw... more Stiffness and ultimate load-carrying capacities of glass fiber-reinforced polymer honeycomb sandwich panels used in bridge applications were evaluated. Eleven full-scale panels with cross-section depths ranging from 6 to 31.5 in. (152 to 800 mm) have been tested to date. The effect of width-to-depth ratio on unit stiffness was found to be insignificant for panels with a width-to-depth ratio between 1 and 5. The effect of this ratio on the ultimate flexural capacity is uncertain because of the erratic nature of core-face bond failures. A simple analytical formula for bending and shear stiffness, based on material properties and geometry of transformed sections, was found to predict service-load deflections within 15% accuracy. Although some factors influencing the ultimate load-carrying capacity were clearly identified in this study, a reliable analytical prediction of the ultimate flexural capacity was not attained. This is because failures occur in the bond material between the out...
Practice Periodical on Structural Design and Construction, 2003
The paper discusses a few issues related to capacity rating of existing bridges using field test ... more The paper discusses a few issues related to capacity rating of existing bridges using field test results. The principles of proof and diagnostic load tests for capacity evaluation are presented through discussing the rating formulas for both tests. The proof load rating is proven a lower bound method. The diagnostic rating is proven the same as linear extrapolation, meaning an upper bound approach in nature. Two different methods used in the literature in calculating load distribution factors are discussed. The two methods are proven theoretically equal in an ideal case, but could be significantly different for field bridges due to the effects of many field factors. To distinguish the two methods, one is defined as load distribution factor ͑LDF͒ and the other as girder distribution factor ͑GDF͒. An example is used to demonstrate the discussions. The results indicate that, on one hand, the measured LDF, though calculated from measured strains, cannot fully reflect the capacity conditions of field bridges. It reflects only a relative load distribution among girders. On the other hand, the GDF approach may overestimate the bridge capacity, because it includes all the beneficial effects. Some beneficial effects may not be reliable for ultimate capacity and thus need to be removed from the capacity rating.
Although traditional mechanical dampers can help reduce cable vibrations, they are not the most e... more Although traditional mechanical dampers can help reduce cable vibrations, they are not the most effective solution due to their position restrictions. Tuned mass dampers ͑TMDs͒ were proposed to overcome this limitation and have been proven effective for cable vibration mitigation according to previous research. However, the effectiveness of TMDs is very sensitive to the vibration frequency, which implies that TMDs designed for a specific vibration frequency may not be efficient for other frequencies. A new type of mechanical damper named the TMD magnetorheological ͑MR͒ damper system is proposed in the present study to address this problem. The feature of this proposed damper is the combination of the position flexibility of TMDs and the adjustability of MR dampers. The proposed damper system is attached to a 7.16-m-long cable to investigate its vibration reduction effectiveness and the dynamic properties of the combined cable-damper system. Experimental results show good vibration reduction effects of the TMD-MR system. The present study focuses on a conceptual exploration of the TMD-MR damper system for cable vibration mitigation through an experimental approach.
In order to better assess the condition of existing and new bridge systems it is necessary to und... more In order to better assess the condition of existing and new bridge systems it is necessary to understand how they would behave under loadings beyond elastic ranges. With about 30% of the 600,000 bridges in the country classified as structurally deficient or functionally obsolete, finding an accurate predictive method becomes a must. The main objectives of this study are (1) to demonstrate how the load distribution affects the behavior of each girder as the live load is increased up to the bridge’s ultimate capacity; (2) to understand bridge systems performance in inelastic stages; and (3) to predict the bridge’s ultimate capacity. A bridge was analyzed up to its failure under various loading conditions using a 3D finite element model. It was found that the only accurate method to determine load distribution at ultimate stages is through section moments. It was also found that the current bridge rating method underestimates considerably the analyzed bridge’s strength. These findings can potentially result in saving millions of dollars annually by avoiding unnecessary weight-limiting postings, rehabilitation or decommissioning and replacement.
Computational Modelling of Concrete Structures, 2014
ABSTRACT This paper deals with the constitutive modeling of Recycled Aggregate Concrete (RAC) in ... more ABSTRACT This paper deals with the constitutive modeling of Recycled Aggregate Concrete (RAC) in which natural coarse aggregates are partially or totally replaced by recycled concrete aggregates obtained from crushed hardened concrete. These aggregates, presenting greater porosity than natural ones, cause the degradation in elastic and strength properties of concrete when compared with standard concrete. The proposed constitutive model for RAC constitutes an extension of the Performance Dependent Model (PDM) by Folino and Etse (2012) which is based on the flow theory of plasticity. It depends on the three stress invariants, and includes a non associative flow rule, an anisotropic hardening law, and a fracture-energy based softening law. A key aspect of the PDM is the consideration of the so-called performed parameter, based on fundamental concrete properties, which plays a relevant roll in the strength and ductility features of concrete behavior. This feature turns the PDM particularly suitable to model failure behavior of RAC by performing the appropriated reformulations. After describing the PDM’s main features, an analysis of RAC’s response behavior and failure mechanism is performed, from which some fundamental material parameters are identified. Then, a reformulation of the PDM is presented to model mechanical behavior of RACs. Some comparisons between experimental results and numerical predictions with the proposed model of uniaxial and triaxial compression tests on RAC are presented to show the capabilities of the constitutive formulation in this work. Finally, some numerical tests are performed with the aim of exploring both, RAC’s failure behavior under mixed-mode of fracture, and the differences with that of standard concrete.
It is very challenging to capture the drag effects for the computational fluid dynamics numerical... more It is very challenging to capture the drag effects for the computational fluid dynamics numerical simulations of the urban canopy wind environment. This study proposed a novel canopy drag coefficient model for accurate analysis of the urban wind environment based on a large eddy simulation, where the drag coefficients varied with quantitatively identified canopy parameters along with the height. Four computational parameters, namely the average kinetic energy, turbulent kinetic energy, sub-grid scale turbulent kinetic energy, and sub-grid scale dissipation, were incorporated into the conventional drag coefficient. The Meixi Lake International Community in Changsha, China, was considered as a case study. The inlet boundary conditions were provided by the Weather Research and Forecasting model, and the proposed drag coefficient model was utilized to simulate the wind field characteristics. The results showed that the drag coefficient was relatively large near the ground, and it decrea...
Fiber reinforced polymers (FRP) have become more popular construction materials in the last decad... more Fiber reinforced polymers (FRP) have become more popular construction materials in the last decade due to the reduction of material costs. The installation and performance evaluation of the first FRP-wrapped balsa wood bridge in Louisiana is described in this document. A comprehensive instrumentation and loading test scheme is discussed and details are illustrated. The selected bridge structure in this demonstration project will potentially provide a new approach to enhancing the transportation infrastructure in Louisiana. The test bridge is the Pierre Part Bridge located on route LA 70 in Assumption Parish, Louisiana Department of Transportation and Development (LADOTD) District 61. The instrumentation consisted of regular strain gauges, fiber optic strain and temperature sensors, accelerometers, and acoustic emission sensors. The measured results from each of the gauges are summarized, and comparisons are made between the finite element models of the bridge structure and the field...
The scouring process excavates and carries away materials from the bed and banks of streams, and ... more The scouring process excavates and carries away materials from the bed and banks of streams, and from around the piers and abutments of bridges. Scour undermines bridges and may cause bridge failures due to structural instability. In the last 30 years, more than 1,000 bridges collapsed in the U.S. and about 60% of the failures are related to the scour of bridge foundations. Due to the difficulty in inspecting bridge scour, scour-induced failures tend to occur suddenly without prior warning or signs of distress to the structures. Owing to the threat of hurricane-induced flooding and the fact that there are a significant number of coastal and river/bayou bridges in Louisiana, a more reliable inspection and monitoring procedure for bridge scour is needed. This proposed study is to develop bridge scour monitoring techniques using fiber optic sensors. Based on theoretical and numerical studies, a few mechanisms were proposed for foundation scour monitoring and verified in laboratory test...
A discussion of a technical note with the aforementioned title by U. Starossek, published in this... more A discussion of a technical note with the aforementioned title by U. Starossek, published in this journal (Volume 124, Number 8, August 1998), is presented. In the discussers' opinion, when comparing real-number and complex-number expressions of aerodynamic forces for flutter analysis, the choice of using a real or complex number format should depend on whether the flutter derivatives or complex coefficients are more conveniently measured or predicted, since the discussers see no significant differences between them in terms of compactness and computation efficiency. Discussion is followed by closure from the author.
The traditional curing method of concrete members in China is through manual water curing based o... more The traditional curing method of concrete members in China is through manual water curing based on the experience of engineers and at an arbitrary time. This method, however, may induce early-age cracks and reduce durability of materials. In this paper, an automated curing system is proposed, which can decrease and even eliminate the early-age cracks by controlling the relative humidity and temperature of the concrete. More specifically, (1) the interval time of curing spray, calculated based on the cement hydration and real-time monitored data, is automatically identified by a programmable logic controller; and (2) the fog spray curing is operated under a constant water pressure by a variable frequency technology. A field test was conducted on 20 box-section beams to evaluate the performance of the proposed system based on the temperature evolution, humidity variation, and compressive strength of the concrete. Compared with the traditional manual water curing, the concrete beams cured by the automated system show higher early-age compressive strength, better appearance without 2 water stains, and no early-age cracks.
AbstractThis study investigates the effects of inhomogeneous wind fields on the aerostatic stabil... more AbstractThis study investigates the effects of inhomogeneous wind fields on the aerostatic stability of a long-span cable-stayed bridge, which straddles a typical mountain-gorge terrain. Inhomogene...
AbstractWind tunnel tests were conducted to investigate the wind pressure characteristics of sawt... more AbstractWind tunnel tests were conducted to investigate the wind pressure characteristics of sawtooth roofs in a simulated open country wind field with relatively low turbulence intensity. Models o...
Weigh-in-motion technology is an effective tool that has been extensively used to monitor traffic... more Weigh-in-motion technology is an effective tool that has been extensively used to monitor traffic on highways. Pavement-based weigh-in-motion systems usually have poor durability and will cause traffic interruption during their installation and maintenance process. The recently developed bridge weigh-in-motion technology provides a more convenient and cost-effective alternative to the pavement-based weigh-in-motion technology. Bridge weigh-in-motion systems can be installed without interrupting the traffic. Also, bridge weigh-in-motion systems have the potential to deliver better accuracy than pavement-based weigh-in-motion systems. Due to these significant advantages, the bridge weigh-in-motion technology has been playing an increasingly important role in bridge health monitoring and overweight truck enforcement, and many studies have been conducted to continuously improve the bridge weigh-in-motion technology. In this review, the common algorithms for bridge weigh-in-motion are di...
h i g h l i g h t s 28 specimens were tested to study the behavior of NSM FRP-to-concrete bonded ... more h i g h l i g h t s 28 specimens were tested to study the behavior of NSM FRP-to-concrete bonded joint. The bond performance of the interface increased with increasing concrete strength. The bond capacity of the interface increases with bond length until rupture of CFRP. The bond at the bonded joint degraded with a decrease in the edge distance. A residual friction stress exists at the bonded joint after debonding failure.
Practice Periodical on Structural Design and Construction, 2016
AbstractIn this paper, the solitary wave forces on a typical coastal bridge deck are evaluated nu... more AbstractIn this paper, the solitary wave forces on a typical coastal bridge deck are evaluated numerically based on a component level assessment, and the countermeasure of the air venting holes is investigated. At first, a wave model based on the second-order solitary wave theory is presented to represent the incident waves in tsunami events. The shear stress transport (SST) k-ω model is used as the turbulence closure for the Reynolds-averaged Navier-Stokes (RANS) equations. Then, the characteristics of the wave forces (the horizontal force, the vertical force, and the moment) considering three different still-water levels (SWLs) and four wave heights for each SWL are investigated, and the effects of the SWLs and wave heights are demonstrated. In addition, a component level–based assessment of the wave loadings, especially the overturning moment, varying along the wave propagation is conducted to enhance the understanding of the force distribution on the bridge deck. Finally, the countermeasure of the air...
One of the major drawbacks with most bridge weigh-in-motion (BWIM) methods that adopt the Moses a... more One of the major drawbacks with most bridge weigh-in-motion (BWIM) methods that adopt the Moses algorithm is the need for acquisition of vehicle speed and axle spacing by using additional devices, such as free-of-axle detectors. This study presents a novel virtual simply supported beam (VSSB) method, which uses weighing sensors to directly identify the speed and the axle spacing of passing vehicles on bridges, making it very desirable for commercial BWIM systems. Numerical simulations and model tests are carried out to study the effectiveness and accuracy of the proposed method. The results show that the proposed method can successfully identify the vehicle speed and axle spacing with good accuracy. The proposed method also proves reliable under noisy conditions.
AbstractBridge scour is a major cause of bridge failures and has emerged as a significant concern... more AbstractBridge scour is a major cause of bridge failures and has emerged as a significant concern for bridge engineers. Most studies focus on the scour mechanism, modeling, detecting and monitoring, and countermeasures. To detect or monitor the scour, the scour effect on the response and feature change of the bridge structure should be studied first to choose an effective measurement. Currently, very few studies have been performed on the scour consequences. Therefore, the present study investigated the scour effect on the responses of the entire bridge, including the superstructure and substructure, and even the responses of vehicles traveling on the bridge, which in turn could be used to detect or monitor the scour of foundations. A field bridge with scour history was adopted, and the bridge–vehicle–wave interaction was considered. First, the soil model, scour model, and wave loads were created. The free vibrations and dynamic analyses under wave loads were then conducted on a single pile and pile group...
All rights reserved. No part of this publication may be reproduced in any form or by any means, w... more All rights reserved. No part of this publication may be reproduced in any form or by any means, without the prior written permission of the Prestressed Concrete Institute. N ineteen seventy-nine was the 25-year Silver Jubilee of the founding of the Prestressed Concrete Institute. CONTENTS Part 6-Early History of Prestressed 163 Concrete in Colorado 'Ed Thwaits is now 85 years old and fives quietly in Denver, Colorado.
... Transportation Research Board Annual Meeting 2007 Paper #07-3492. Abstract: In order to bette... more ... Transportation Research Board Annual Meeting 2007 Paper #07-3492. Abstract: In order to better assess the condition of existing and new bridge systems it is necessary to understand how they would behave under loadings beyond elastic ranges. ... 15p. Authors: Araujo, Marcio. ...
Transportation Research Record: Journal of the Transportation Research Board, 2003
Stiffness and ultimate load-carrying capacities of glass fiber-reinforced polymer honeycomb sandw... more Stiffness and ultimate load-carrying capacities of glass fiber-reinforced polymer honeycomb sandwich panels used in bridge applications were evaluated. Eleven full-scale panels with cross-section depths ranging from 6 to 31.5 in. (152 to 800 mm) have been tested to date. The effect of width-to-depth ratio on unit stiffness was found to be insignificant for panels with a width-to-depth ratio between 1 and 5. The effect of this ratio on the ultimate flexural capacity is uncertain because of the erratic nature of core-face bond failures. A simple analytical formula for bending and shear stiffness, based on material properties and geometry of transformed sections, was found to predict service-load deflections within 15% accuracy. Although some factors influencing the ultimate load-carrying capacity were clearly identified in this study, a reliable analytical prediction of the ultimate flexural capacity was not attained. This is because failures occur in the bond material between the out...
Practice Periodical on Structural Design and Construction, 2003
The paper discusses a few issues related to capacity rating of existing bridges using field test ... more The paper discusses a few issues related to capacity rating of existing bridges using field test results. The principles of proof and diagnostic load tests for capacity evaluation are presented through discussing the rating formulas for both tests. The proof load rating is proven a lower bound method. The diagnostic rating is proven the same as linear extrapolation, meaning an upper bound approach in nature. Two different methods used in the literature in calculating load distribution factors are discussed. The two methods are proven theoretically equal in an ideal case, but could be significantly different for field bridges due to the effects of many field factors. To distinguish the two methods, one is defined as load distribution factor ͑LDF͒ and the other as girder distribution factor ͑GDF͒. An example is used to demonstrate the discussions. The results indicate that, on one hand, the measured LDF, though calculated from measured strains, cannot fully reflect the capacity conditions of field bridges. It reflects only a relative load distribution among girders. On the other hand, the GDF approach may overestimate the bridge capacity, because it includes all the beneficial effects. Some beneficial effects may not be reliable for ultimate capacity and thus need to be removed from the capacity rating.
Although traditional mechanical dampers can help reduce cable vibrations, they are not the most e... more Although traditional mechanical dampers can help reduce cable vibrations, they are not the most effective solution due to their position restrictions. Tuned mass dampers ͑TMDs͒ were proposed to overcome this limitation and have been proven effective for cable vibration mitigation according to previous research. However, the effectiveness of TMDs is very sensitive to the vibration frequency, which implies that TMDs designed for a specific vibration frequency may not be efficient for other frequencies. A new type of mechanical damper named the TMD magnetorheological ͑MR͒ damper system is proposed in the present study to address this problem. The feature of this proposed damper is the combination of the position flexibility of TMDs and the adjustability of MR dampers. The proposed damper system is attached to a 7.16-m-long cable to investigate its vibration reduction effectiveness and the dynamic properties of the combined cable-damper system. Experimental results show good vibration reduction effects of the TMD-MR system. The present study focuses on a conceptual exploration of the TMD-MR damper system for cable vibration mitigation through an experimental approach.
Uploads
Papers by C.S. Cai