Sri Sritharan - Profile on Academia.edu (original) (raw)
Papers by Sri Sritharan
A significant portion of the United States bridge infrastructure is rapidly approaching the end o... more A significant portion of the United States bridge infrastructure is rapidly approaching the end of its intended design life, demanding development of new structural members that are durable, faster to construct and increase the longevity of bridges. In response, using Ultra-high performance concrete (UHPC) and prefabrication methods, a tapered, H-shaped, precast UHPC pile was developed at Iowa State University (ISU). The UHPC pile increases the longevity of bridge foundations while reducing their maintenance cost in comparison to steel and concrete piles. This paper will focus on experimental and analytical studies done to facilitate the field implementation of the UHPC pile. A total of four full-scale pile-to-abutment connection subassemblies were tested under combined vertical axial forces and cyclic lateral displacements representing the expected thermal movements in integral abutment bridges. Several variables such as axial load, pile orientation and construction method were investigated. The experimental investigations revealed that the UHPC piles can be installed with connection details similar to those used for steel H-piles in both cast-in-place and precast abutments. Also, an analytical model was developed in OpenSEES to predict the observed lateral load behavior. The test results, observations, measured and calculated response and conclusions are presented in the paper.
Ultra High Performance Concrete (UHPC) on bridges in the United States have typically been joint ... more Ultra High Performance Concrete (UHPC) on bridges in the United States have typically been joint applications with limited deck overlay placements. Iowa Department of Transportation (DOT) let a pilot project for UHPC bridge deck overlay on a 205.5 ft x 44 ft Pretensioned Prestressed Concrete girder bridge on US 18 over the Floyd River in Sheldon, Iowa. The project has sufficient quantity to be the first machine
Third International Interactive Symposium on Ultra-High Performance Concrete
Ultra-high-performance concrete (UHPC), with its superior mechanical characteristics and durabili... more Ultra-high-performance concrete (UHPC), with its superior mechanical characteristics and durability properties, provides opportunities to build sustainable highway infrastructure. To attain desirable properties, the presence of fibers plays an integral part in ultra-high-performance concrete (UHPC) mixes. This paper studies the influence of fiber volume on both the compressive strength and tensile behavior of UHPC. To investigate these fiber dependencies, specimens were cast using UHPC from three suppliers with three fiber volume fractions, i.e., 1%, 2%, and 3%. Cubes of 2 in x 2 in x 2 in. and cylinders with dimensions 3 in. (diameter) x 6 in. (length) were tested for compression strength comparisons at different ages according to ASTM C109/C109M-20b and ASTM C1856/C1856M-17, respectively. At 3% fiber volume, the strength ratio of cylinders to cubes was around 1. However, the strengths of cylinders were higher than cube strengths at lower fiber volumes. The strength ratio remained similar and did not vary with the age of UHPC. AASHTO T397 test procedure was used to quantify the direct tension behavior of UHPC. In addition, longer dog-bone specimens than specified in AASHTO T397 were cast to investigate the effects of change in gauge length on tensile behavior. Varying fiber volume fractions significantly influenced the tensile strength and post-cracking tensile response of UHPC. A higher volume of fibers resulted in higher tensile strength and a more extensive multi-cracking phase. The crack straining phase was dependent on the UHPC type and did not depend on fiber volume. An increase in gauge length indicated reduced residual tensile load-carrying capacities beyond localizations.
The First UHPC Piles Project in Ontario, Canada
Third International Interactive Symposium on Ultra-High Performance Concrete
Third International Interactive Symposium on Ultra-High Performance Concrete
Post-tensioned Box Girder (PTBG) bridges are frequently used when spans range from 100 to 250 ft,... more Post-tensioned Box Girder (PTBG) bridges are frequently used when spans range from 100 to 250 ft, especially in the western US. Due to aging, environmental factors, and increasing traffic load demands, the decks of these bridges are the first elements to show signs of deterioration. Replacing the deck of a PTBG bridge is difficult and costly. This paper summarizes the progress made in a research project using the UHPC deck overlay concept to rehabilitate PTBG bridge decks in California cost-effectively. To confirm the beneficial outcomes of the proposed solution, a large-scale test unit is under construction and will be tested under different loading conditions. In addition to demonstrating the benefits of using UHPC to rehabilitate PTBG bridge decks, the large-scale tests will examine the ultimate-limit state behavior of the decks rehabilitated with thin UHPC layers under positive and negative moments and their punching shear capacity.
Third International Interactive Symposium on Ultra-High Performance Concrete
Various Accelerated Bridge Construction (ABC) techniques, such as structural precast elements or ... more Various Accelerated Bridge Construction (ABC) techniques, such as structural precast elements or complete modular bridge systems, are being developed and implemented throughout the United States to reduce on-site construction time and improve mobility. One of the major constraints of ABC is that precast elements can be very large and need to be broken into transportable pieces. In addition, larger cranes are required for assembly on-site. In this work, bridge components fabricated using ultra-high-performance concrete (UHPC) are investigated to overcome these challenges. The ordinary standard bridge seat type abutment, typical of the Caltrans inventory, is used as a prototype. By using UHPC, the sectional sizes have been reduced, making it possible for the abutment to be transported as a single piece. Two different concepts have been explored. The first one uses stay-in form shells while the second concept relies on a hollow section with a wall thickness of 6 inches and corbels to provide a seat width of 36 inches which exceeds the Caltrans Seismic Design Criteria (SDC) requirement. The precast abutment cap will be designed with corrugated metal pipe sockets, which shall be filled with in-situ closure pours to ensure fixed connections with steel H piles. The investigation evaluates the performance of the new abutment under service, strength, and extreme loads. The performance of the new system and its components will be validated by a half-scale experimental test unit. It is anticipated that Caltrans will implement this detail in constructing two-lane standard ordinary bridges of two or three spans.
Iowa State University. Institute for Transportation, Mar 1, 2020
March 2020 6. Performing Organization Code 7. Author(s) Zhao Cheng (), Sri Sritharan (orcid.org/0... more March 2020 6. Performing Organization Code 7. Author(s) Zhao Cheng (), Sri Sritharan (orcid.org/0000-0001-9941-8156), and Jeramy Ashlock (orcid.org/0000-0003-0677-9900) 8. Performing Organization Report No. InTrans Project 14-495 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)
Lessons Learned from Reinforced Concrete Wall Tests
SP-313 Proceedings of the First ACI & JCI Joint Seminar: Design of Concrete Structures Against Earthquake and Tsunami Damage, 2017
Considering a limited seismic gap around a seismically isolated building, in combination with a v... more Considering a limited seismic gap around a seismically isolated building, in combination with a very strong earthquake excitation, there is always the possibility of poundings either with the surrounding moat wall or with the neighboring buildings. In order to investigate the influence of the impacts on the overall structural response, seismically isolated buildings in series with adjacent structures have been simulated and analyzed numerically under strong earthquake excitations. The effects of certain parameters, such as the size of the separation distance, the earthquake characteristics and the structural properties of the adjacent buildings, have been investigated parametrically using a specially developed software application.
Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016), 2016
A simple analytical model for simulating a controlled rocking system consisting of a Precast Wall... more A simple analytical model for simulating a controlled rocking system consisting of a Precast Wall with End Columns (named as PreWEC) has been developed and compared against experimental results. The wall panel and end columns are secured to the foundation using prestressing, allowing PreWECs to experience rocking motions. The proposed model accounts for its predominant rotational degree of freedom formulation based on existing knowledge and adds new features to accurately capture the measured responses. They include a migrating rotation center that recognizes the variation in the contact length and its effect on the elongation in the post-tensioned tendons. Supplemental energy dissipation in PreWEC is provided by steel O-connectors, which horizontally join the wall panel to the end columns. These connectors are modelled using a system of nonlinear springs. Two different experiments were used to demonstrate the accuracy of the model validation, which include: a) a 5/18-scale PreWEC subjected to shake table motions; and b) a 1/5-scale PreWEC subjected to free vibration motions. It is shown that rotation responses and associated peaks experienced by the PreWEC rocking system can be accurately predicted using a simplified model.
Connection Details and Field Implementation of UHPC Piles – Phase II
Next-Gen Monitoring and Evaluation of California Bridges
An Experimental Study of a Socket Connection Designed for Using Precast Columns in Bridges
Transportation Research Board 97th Annual MeetingTransportation Research Board, 2018
Effects of vertical ground acceleration on the seismic moment demand of bridge superstructure connections
Engineering Structures, 2022
Behavior of a Pile Group Supporting a Precast Pile Cap under Combined Vertical and Lateral Loads
Journal of Geotechnical and Geoenvironmental Engineering, 2021
AbstractA half-scale field test was conducted on a pile group installed at a stiff clay site. The... more AbstractA half-scale field test was conducted on a pile group installed at a stiff clay site. The pile group consisted of eight steel H-piles, with a battered pile at each corner, and connected to ...
PCI Journal, 2019
Original manuscripts and discussion on published papers are accepted on review in accordance with... more Original manuscripts and discussion on published papers are accepted on review in accordance with the Precast/Prestressed Concrete Institute's peer-review process. No payment is o ered.
Second International Interactive Symposium on UHPC, 2019
With superior mechanical and durability properties, Ultra High-Performance Concrete (UHPC) is an ... more With superior mechanical and durability properties, Ultra High-Performance Concrete (UHPC) is an ideal choice for shallow depth, long span beams in parking and commercial buildings. However, such an application has not been realized due to significantly high material cost. UHPC volume reduction is thus critical and hence the need for an optimal design solution for long span beams. This paper explores the possibility of developing precast, prestressed UHPC Double Tee beams-a concept that has been successfully used with concrete precast, prestressed concrete. This paper presents a suitable design approach after a discussion on the concept of UHPC Double Tee beams. A time-dependent analysis program to calculate long term deflections using different shrinkage and creep properties for UHPC as well as a non-linear strain-compatibility section analysis program have been developed to formulate the design approach. UHPC Double Tees are compared against post-tensioned beams and steel beams in terms of depth and weight.
Lateral rce resisting systems
Challenges in the Regional Calibration of Resistance Factors for Deep Foundation Design
Second International Interactive Symposium on UHPC, 2019
The use of UHPC continues to grow rapidly and a great deal of present-day research focuses on und... more The use of UHPC continues to grow rapidly and a great deal of present-day research focuses on understanding and fine tuning of this material composition. This work is aimed at understanding the effects of size on the tensile behavior of UHPC in relation to the fiber percentage. The paper also discusses the variation in the stress-strain responses based on the chosen gauge length for the tension characterization. Several UHPC dog bone shaped specimens have been tested in the laboratory under the displacement controlled mode. The size effect is assessed by comparing the results of the specimens with cross sections of 2 in. x 2 in., 2 in. x 4 in., and 4 in. x 4 in. The response of the specimens was measured with LVDT and a 3D optical tracking system. The LEDs for the optical tracking measurements were placed at 1 in. interval over a length of 14 in. in the critical zone of the specimen where failure was anticipated. The results show that the effect of size on the stress-strain curves i...
A significant portion of the United States bridge infrastructure is rapidly approaching the end o... more A significant portion of the United States bridge infrastructure is rapidly approaching the end of its intended design life, demanding development of new structural members that are durable, faster to construct and increase the longevity of bridges. In response, using Ultra-high performance concrete (UHPC) and prefabrication methods, a tapered, H-shaped, precast UHPC pile was developed at Iowa State University (ISU). The UHPC pile increases the longevity of bridge foundations while reducing their maintenance cost in comparison to steel and concrete piles. This paper will focus on experimental and analytical studies done to facilitate the field implementation of the UHPC pile. A total of four full-scale pile-to-abutment connection subassemblies were tested under combined vertical axial forces and cyclic lateral displacements representing the expected thermal movements in integral abutment bridges. Several variables such as axial load, pile orientation and construction method were investigated. The experimental investigations revealed that the UHPC piles can be installed with connection details similar to those used for steel H-piles in both cast-in-place and precast abutments. Also, an analytical model was developed in OpenSEES to predict the observed lateral load behavior. The test results, observations, measured and calculated response and conclusions are presented in the paper.
Ultra High Performance Concrete (UHPC) on bridges in the United States have typically been joint ... more Ultra High Performance Concrete (UHPC) on bridges in the United States have typically been joint applications with limited deck overlay placements. Iowa Department of Transportation (DOT) let a pilot project for UHPC bridge deck overlay on a 205.5 ft x 44 ft Pretensioned Prestressed Concrete girder bridge on US 18 over the Floyd River in Sheldon, Iowa. The project has sufficient quantity to be the first machine
Third International Interactive Symposium on Ultra-High Performance Concrete
Ultra-high-performance concrete (UHPC), with its superior mechanical characteristics and durabili... more Ultra-high-performance concrete (UHPC), with its superior mechanical characteristics and durability properties, provides opportunities to build sustainable highway infrastructure. To attain desirable properties, the presence of fibers plays an integral part in ultra-high-performance concrete (UHPC) mixes. This paper studies the influence of fiber volume on both the compressive strength and tensile behavior of UHPC. To investigate these fiber dependencies, specimens were cast using UHPC from three suppliers with three fiber volume fractions, i.e., 1%, 2%, and 3%. Cubes of 2 in x 2 in x 2 in. and cylinders with dimensions 3 in. (diameter) x 6 in. (length) were tested for compression strength comparisons at different ages according to ASTM C109/C109M-20b and ASTM C1856/C1856M-17, respectively. At 3% fiber volume, the strength ratio of cylinders to cubes was around 1. However, the strengths of cylinders were higher than cube strengths at lower fiber volumes. The strength ratio remained similar and did not vary with the age of UHPC. AASHTO T397 test procedure was used to quantify the direct tension behavior of UHPC. In addition, longer dog-bone specimens than specified in AASHTO T397 were cast to investigate the effects of change in gauge length on tensile behavior. Varying fiber volume fractions significantly influenced the tensile strength and post-cracking tensile response of UHPC. A higher volume of fibers resulted in higher tensile strength and a more extensive multi-cracking phase. The crack straining phase was dependent on the UHPC type and did not depend on fiber volume. An increase in gauge length indicated reduced residual tensile load-carrying capacities beyond localizations.
The First UHPC Piles Project in Ontario, Canada
Third International Interactive Symposium on Ultra-High Performance Concrete
Third International Interactive Symposium on Ultra-High Performance Concrete
Post-tensioned Box Girder (PTBG) bridges are frequently used when spans range from 100 to 250 ft,... more Post-tensioned Box Girder (PTBG) bridges are frequently used when spans range from 100 to 250 ft, especially in the western US. Due to aging, environmental factors, and increasing traffic load demands, the decks of these bridges are the first elements to show signs of deterioration. Replacing the deck of a PTBG bridge is difficult and costly. This paper summarizes the progress made in a research project using the UHPC deck overlay concept to rehabilitate PTBG bridge decks in California cost-effectively. To confirm the beneficial outcomes of the proposed solution, a large-scale test unit is under construction and will be tested under different loading conditions. In addition to demonstrating the benefits of using UHPC to rehabilitate PTBG bridge decks, the large-scale tests will examine the ultimate-limit state behavior of the decks rehabilitated with thin UHPC layers under positive and negative moments and their punching shear capacity.
Third International Interactive Symposium on Ultra-High Performance Concrete
Various Accelerated Bridge Construction (ABC) techniques, such as structural precast elements or ... more Various Accelerated Bridge Construction (ABC) techniques, such as structural precast elements or complete modular bridge systems, are being developed and implemented throughout the United States to reduce on-site construction time and improve mobility. One of the major constraints of ABC is that precast elements can be very large and need to be broken into transportable pieces. In addition, larger cranes are required for assembly on-site. In this work, bridge components fabricated using ultra-high-performance concrete (UHPC) are investigated to overcome these challenges. The ordinary standard bridge seat type abutment, typical of the Caltrans inventory, is used as a prototype. By using UHPC, the sectional sizes have been reduced, making it possible for the abutment to be transported as a single piece. Two different concepts have been explored. The first one uses stay-in form shells while the second concept relies on a hollow section with a wall thickness of 6 inches and corbels to provide a seat width of 36 inches which exceeds the Caltrans Seismic Design Criteria (SDC) requirement. The precast abutment cap will be designed with corrugated metal pipe sockets, which shall be filled with in-situ closure pours to ensure fixed connections with steel H piles. The investigation evaluates the performance of the new abutment under service, strength, and extreme loads. The performance of the new system and its components will be validated by a half-scale experimental test unit. It is anticipated that Caltrans will implement this detail in constructing two-lane standard ordinary bridges of two or three spans.
Iowa State University. Institute for Transportation, Mar 1, 2020
March 2020 6. Performing Organization Code 7. Author(s) Zhao Cheng (), Sri Sritharan (orcid.org/0... more March 2020 6. Performing Organization Code 7. Author(s) Zhao Cheng (), Sri Sritharan (orcid.org/0000-0001-9941-8156), and Jeramy Ashlock (orcid.org/0000-0003-0677-9900) 8. Performing Organization Report No. InTrans Project 14-495 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)
Lessons Learned from Reinforced Concrete Wall Tests
SP-313 Proceedings of the First ACI & JCI Joint Seminar: Design of Concrete Structures Against Earthquake and Tsunami Damage, 2017
Considering a limited seismic gap around a seismically isolated building, in combination with a v... more Considering a limited seismic gap around a seismically isolated building, in combination with a very strong earthquake excitation, there is always the possibility of poundings either with the surrounding moat wall or with the neighboring buildings. In order to investigate the influence of the impacts on the overall structural response, seismically isolated buildings in series with adjacent structures have been simulated and analyzed numerically under strong earthquake excitations. The effects of certain parameters, such as the size of the separation distance, the earthquake characteristics and the structural properties of the adjacent buildings, have been investigated parametrically using a specially developed software application.
Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016), 2016
A simple analytical model for simulating a controlled rocking system consisting of a Precast Wall... more A simple analytical model for simulating a controlled rocking system consisting of a Precast Wall with End Columns (named as PreWEC) has been developed and compared against experimental results. The wall panel and end columns are secured to the foundation using prestressing, allowing PreWECs to experience rocking motions. The proposed model accounts for its predominant rotational degree of freedom formulation based on existing knowledge and adds new features to accurately capture the measured responses. They include a migrating rotation center that recognizes the variation in the contact length and its effect on the elongation in the post-tensioned tendons. Supplemental energy dissipation in PreWEC is provided by steel O-connectors, which horizontally join the wall panel to the end columns. These connectors are modelled using a system of nonlinear springs. Two different experiments were used to demonstrate the accuracy of the model validation, which include: a) a 5/18-scale PreWEC subjected to shake table motions; and b) a 1/5-scale PreWEC subjected to free vibration motions. It is shown that rotation responses and associated peaks experienced by the PreWEC rocking system can be accurately predicted using a simplified model.
Connection Details and Field Implementation of UHPC Piles – Phase II
Next-Gen Monitoring and Evaluation of California Bridges
An Experimental Study of a Socket Connection Designed for Using Precast Columns in Bridges
Transportation Research Board 97th Annual MeetingTransportation Research Board, 2018
Effects of vertical ground acceleration on the seismic moment demand of bridge superstructure connections
Engineering Structures, 2022
Behavior of a Pile Group Supporting a Precast Pile Cap under Combined Vertical and Lateral Loads
Journal of Geotechnical and Geoenvironmental Engineering, 2021
AbstractA half-scale field test was conducted on a pile group installed at a stiff clay site. The... more AbstractA half-scale field test was conducted on a pile group installed at a stiff clay site. The pile group consisted of eight steel H-piles, with a battered pile at each corner, and connected to ...
PCI Journal, 2019
Original manuscripts and discussion on published papers are accepted on review in accordance with... more Original manuscripts and discussion on published papers are accepted on review in accordance with the Precast/Prestressed Concrete Institute's peer-review process. No payment is o ered.
Second International Interactive Symposium on UHPC, 2019
With superior mechanical and durability properties, Ultra High-Performance Concrete (UHPC) is an ... more With superior mechanical and durability properties, Ultra High-Performance Concrete (UHPC) is an ideal choice for shallow depth, long span beams in parking and commercial buildings. However, such an application has not been realized due to significantly high material cost. UHPC volume reduction is thus critical and hence the need for an optimal design solution for long span beams. This paper explores the possibility of developing precast, prestressed UHPC Double Tee beams-a concept that has been successfully used with concrete precast, prestressed concrete. This paper presents a suitable design approach after a discussion on the concept of UHPC Double Tee beams. A time-dependent analysis program to calculate long term deflections using different shrinkage and creep properties for UHPC as well as a non-linear strain-compatibility section analysis program have been developed to formulate the design approach. UHPC Double Tees are compared against post-tensioned beams and steel beams in terms of depth and weight.
Lateral rce resisting systems
Challenges in the Regional Calibration of Resistance Factors for Deep Foundation Design
Second International Interactive Symposium on UHPC, 2019
The use of UHPC continues to grow rapidly and a great deal of present-day research focuses on und... more The use of UHPC continues to grow rapidly and a great deal of present-day research focuses on understanding and fine tuning of this material composition. This work is aimed at understanding the effects of size on the tensile behavior of UHPC in relation to the fiber percentage. The paper also discusses the variation in the stress-strain responses based on the chosen gauge length for the tension characterization. Several UHPC dog bone shaped specimens have been tested in the laboratory under the displacement controlled mode. The size effect is assessed by comparing the results of the specimens with cross sections of 2 in. x 2 in., 2 in. x 4 in., and 4 in. x 4 in. The response of the specimens was measured with LVDT and a 3D optical tracking system. The LEDs for the optical tracking measurements were placed at 1 in. interval over a length of 14 in. in the critical zone of the specimen where failure was anticipated. The results show that the effect of size on the stress-strain curves i...