SIDDAIAH YARRA - Academia.edu (original) (raw)
Papers by SIDDAIAH YARRA
Full-scale experimental studies of precast concrete facade were completed in 2011/12 to evaluate ... more Full-scale experimental studies of precast concrete facade were completed in 2011/12 to evaluate the seismic damage of nonstructural building components. Experimental testing of cladding panels with and without glass windows was completed at the nees@berkeley lab facility. Specimens included varied concrete column covers with steel connections to an articulated steel test frame. The static loading protocol compared cyclic loading with increasing amplitude to a seismic loading protocol based upon the nonlinear time history drift of the prototype structure. Scan Station 2 scanner from Leica Geosystems was used to record 3D displacements of both entire panels and individual connections during the testing. The scanner allows for permanent recording of the movement of the entire surface in three-dimensional space. This allows for archiving surfaces, allowing the researchers a wider understanding of the rigid body movement, the warping of the surface, and the concentrated bending of small...
Six full-scale experimental studies of precast concrete facade have been completed in 2011/12 to ... more Six full-scale experimental studies of precast concrete facade have been completed in 2011/12 to evaluate the seismic damage of nonstructural building components. Experimental testing of cladding panels with and without installed windows was completed at the nees@berkeley lab facility. Specimens included full-width, half-width, and return column covers supported by an articulated steel test jig simulating a building structural frame. The static loading protocol compared cyclic loading with increasing amplitude to a seismic loading protocol based upon the nonlinear time history drift of the prototype structure. Maximum inter-story drifts of approximately 0.0600 were applied during the static testing, well above the design intent of these types of systems. Overall performance of the cladding was very good as long as lateral drifts did not exceed the design drift. When lateral displacement well above the design drift was applied, damage events were observed and recorded. The horizontal...
Active and Passive Smart Structures and Integrated Systems IX, 2020
This paper presents a rheological model that was developed to stimulate the experimental behavior... more This paper presents a rheological model that was developed to stimulate the experimental behavior of magnetorheological elastomers (MREs) under varying loading conditions (magnetic field, strain amplitude and frequency). Magnetorheological elastomers (MREs) were fabricated and tested using double lap shear experiment setup under different strain amplitudes, magnetic fields and frequencies. A linear visco-elastic rheological model consists of seven parameters to represent both viscous and elastic behavior of MREs. The parameters under varying loading conditions were identified and optimized using the data recorded from experiments. The experimental results were then compared with model predicted values which demonstrate that the seven-parameter model predicts MRE behavior well.
Journal of Intelligent Material Systems and Structures, 2018
This study presents an experimental investigation on large-strain behavior of natural rubber– and... more This study presents an experimental investigation on large-strain behavior of natural rubber– and silicone-based magnetorheological elastomers within a larger scope of structural vibration mitigation due to wind, traffic and seismic events. Magnetorheological elastomer samples with different weight percentages of iron particles, additives, and elastomer matrix were fabricated. The microstructures of specimens were examined, and their mechanical properties were investigated by a unique electromagnetic double-lap shear experimental setup capable of applying simultaneous compression and shear loads. The experimental results demonstrated that the isotropic natural rubber–based magnetorheological elastomers exhibit about 30% magnetorheological effect under large strains, while they achieve a higher magnetorheological effect under the combined axial and shear loading. The magnetorheological effect was 92% and 33% for 10% and 100% shear strains when 100 psi axial stress was applied. A natu...
Journal of Intelligent Material Systems and Structures, 2018
This study presents an experimental investigation on the magnetorheological effect of a new magne... more This study presents an experimental investigation on the magnetorheological effect of a new magnetorheological elastomer–based adaptive bridge isolation bearing system. Two identical magnetorheological elastomer–based adaptive bridge bearings (isolators) were designed and fabricated. Electromagnets were incorporated to create a closed-loop magnetic path in the magnetorheological elastomer layers. A double-lap shear and compression test setup was utilized to characterize the mechanical properties of the system subjected to scaled structural cyclic forces and strains. Experimental results demonstrated that the effective stiffness of adaptive bridge bearings increases with increased applied magnetic field and a compressive force resulted in larger apparent shear stiffness. Also, increasing loading frequency resulted in larger apparent shear stiffness and lower magnetorheological effect and similarly, however, a compressive force resulted in smaller magnetorheological effects.
Active and Passive Smart Structures and Integrated Systems 2017, 2017
This study presents the design, development, testing, and performance evaluation of a scaled brid... more This study presents the design, development, testing, and performance evaluation of a scaled bridge bearing utilizing magnetorheological elastomer (MRE) layers as adaptive elements, which allow for a varying stiffness under a magnetic field. The adaptive bridge bearing system incorporates a closed-loop magnetic circuit that results in an enhanced magnetic field in the MRE layers. A new design is introduced and optimized using structural and magnetic finite element analyses. Two bearings and a test setup for applying simultaneous variable shear, constant compression, and a variable magnetic field on the bearing are fabricated. The adaptive bridge bearing results demonstrate the stiffness change of the bearing under different strain levels and loading frequencies, as well as the ability of the bearing to change its stiffness under different applied electric currents, which can be correlated to the applied magnetic field.
SPIE Proceedings, 2016
This study presents an adaptive bridge bearing that can sense structural loads and tune its prope... more This study presents an adaptive bridge bearing that can sense structural loads and tune its properties to mitigate structural vibrations. The bearing utilizes magnetorheological elastomer (MRE) layers which allow for an increased stiffness induced with a magnetic field. The system also features a MRE-based sensing system for sensing the structural wind and traffic load. The sensing system is capable of transmitting data wirelessly to a central logging computer for monitoring bridge performance and sending alerts in the case of a major event. The capability of the MRE-based sensing system for sensing structural loads and wireless transmission of data were investigated. The adaptive bridge bearing incorporates a closed-loop magnetic circuit that results in an enhanced magnetic field in the MRE layers. Results show the sensitivity of the MRE-based sensors and the performance of the wireless system, as well as the design and analysis of the tunable bridge bearing.
Structures Congress 2012, 2012
Two full-scale precast concrete cladding panels were tested in 2011 on a full-scale five-story st... more Two full-scale precast concrete cladding panels were tested in 2011 on a full-scale five-story steel fame building at the E~Defense shake table facility in Japan. The panels were designed according to common U.S. practice. Two issues evaluated were: 1) the effect of acceleration on the cladding panel, and 2) the effectiveness of the current slotted-bolt sliding connection to allow for inter-story earthquake motion. The cladding tests represented one type of standard US cladding facade design where cladding is designed to accommodate inter-story drift though racking of individual panels. Panels were cast in Japan but steel connections were designed and fabricated in the US to accurately simulate the behavior of American cladding construction. A 50 mm vertical seismic joint was installed between the two panels. Two full-height column cover panels were tested, a return cover 3D shape, and a flat panel. Instrumentation measured the acceleration of the panels and the movement of the slotted connections. Findings include the ability of slotted connections to slide while being accelerated in a full scale 3D seismic motion and development of fragility curves relating damage to panel and/or floor acceleration.
Structures Congress 2014, 2014
Six full-scale experimental studies of precast concrete facade have been completed in 2011/12 to ... more Six full-scale experimental studies of precast concrete facade have been completed in 2011/12 to evaluate the seismic performance of nonstructural building components. Experimental testing of cladding panels was completed at the nees@berkeley lab facility. Research findings are particularly relevant to seismic regions of the United States and other countries. The paper is targeted toward engineers directly responsible for facade design as well as the Engineer of Record for a building project. Researchers involved in code development and expansion of Performance Based Earthquake Engineering will also benefit from the paper. Specimens included full-width, half-width, and return column covers supported by an articulated steel test jig simulating a building structural frame. Steel connections between the panels and the supporting frame included slotted connections at the tops of panels and welded connections at the base of panels. The static loading protocol compared cyclic loading with increasing amplitude to a seismic loading protocol based upon the nonlinear time history drift of the prototype structure. The horizontal slotted connection at the top of panels allowed inter-story drift matching the building code requirements to occur with minimal damage to the panels, however once the inter-story drift increased above a point where the slotted connection reached the allowed travel, damage to the panel, in the form of severe cracking at embedded connections occurred. Force-deformation graphs of the global specimen and individual connections quantify the hysteretic behavior. Horizontal slotted connections clearly show minimal resistance to lateral movement while the displacement remains below the maximum allowance of the slot. Once this free clearance is reached, bearing of the slot significantly increases and the connection quickly increases lateral resistance. Welded connections show very little hysteretic behavior due to low levels of relative displacement. The concrete embeds of the weld plates show more pronounced hysteretic behavior as this is the main location of damage and cracking at the base connections. The primary goal of evaluating the connection force-deformation relationships is to develop suitable analytical models for use in nonlinear studies of the facade system. The presentation will clarify performance of modern facade systems and define the analytical modeling input data for researchers exploring holistic building performance.
Full-scale experimental studies of precast concrete facade were completed in 2011/12 to evaluate ... more Full-scale experimental studies of precast concrete facade were completed in 2011/12 to evaluate the seismic damage of nonstructural building components. Experimental testing of cladding panels with and without glass windows was completed at the nees@berkeley lab facility. Specimens included varied concrete column covers with steel connections to an articulated steel test frame. The static loading protocol compared cyclic loading with increasing amplitude to a seismic loading protocol based upon the nonlinear time history drift of the prototype structure. Scan Station 2 scanner from Leica Geosystems was used to record 3D displacements of both entire panels and individual connections during the testing. The scanner allows for permanent recording of the movement of the entire surface in three-dimensional space. This allows for archiving surfaces, allowing the researchers a wider understanding of the rigid body movement, the warping of the surface, and the concentrated bending of small...
Six full-scale experimental studies of precast concrete facade have been completed in 2011/12 to ... more Six full-scale experimental studies of precast concrete facade have been completed in 2011/12 to evaluate the seismic damage of nonstructural building components. Experimental testing of cladding panels with and without installed windows was completed at the nees@berkeley lab facility. Specimens included full-width, half-width, and return column covers supported by an articulated steel test jig simulating a building structural frame. The static loading protocol compared cyclic loading with increasing amplitude to a seismic loading protocol based upon the nonlinear time history drift of the prototype structure. Maximum inter-story drifts of approximately 0.0600 were applied during the static testing, well above the design intent of these types of systems. Overall performance of the cladding was very good as long as lateral drifts did not exceed the design drift. When lateral displacement well above the design drift was applied, damage events were observed and recorded. The horizontal...
Active and Passive Smart Structures and Integrated Systems IX, 2020
This paper presents a rheological model that was developed to stimulate the experimental behavior... more This paper presents a rheological model that was developed to stimulate the experimental behavior of magnetorheological elastomers (MREs) under varying loading conditions (magnetic field, strain amplitude and frequency). Magnetorheological elastomers (MREs) were fabricated and tested using double lap shear experiment setup under different strain amplitudes, magnetic fields and frequencies. A linear visco-elastic rheological model consists of seven parameters to represent both viscous and elastic behavior of MREs. The parameters under varying loading conditions were identified and optimized using the data recorded from experiments. The experimental results were then compared with model predicted values which demonstrate that the seven-parameter model predicts MRE behavior well.
Journal of Intelligent Material Systems and Structures, 2018
This study presents an experimental investigation on large-strain behavior of natural rubber– and... more This study presents an experimental investigation on large-strain behavior of natural rubber– and silicone-based magnetorheological elastomers within a larger scope of structural vibration mitigation due to wind, traffic and seismic events. Magnetorheological elastomer samples with different weight percentages of iron particles, additives, and elastomer matrix were fabricated. The microstructures of specimens were examined, and their mechanical properties were investigated by a unique electromagnetic double-lap shear experimental setup capable of applying simultaneous compression and shear loads. The experimental results demonstrated that the isotropic natural rubber–based magnetorheological elastomers exhibit about 30% magnetorheological effect under large strains, while they achieve a higher magnetorheological effect under the combined axial and shear loading. The magnetorheological effect was 92% and 33% for 10% and 100% shear strains when 100 psi axial stress was applied. A natu...
Journal of Intelligent Material Systems and Structures, 2018
This study presents an experimental investigation on the magnetorheological effect of a new magne... more This study presents an experimental investigation on the magnetorheological effect of a new magnetorheological elastomer–based adaptive bridge isolation bearing system. Two identical magnetorheological elastomer–based adaptive bridge bearings (isolators) were designed and fabricated. Electromagnets were incorporated to create a closed-loop magnetic path in the magnetorheological elastomer layers. A double-lap shear and compression test setup was utilized to characterize the mechanical properties of the system subjected to scaled structural cyclic forces and strains. Experimental results demonstrated that the effective stiffness of adaptive bridge bearings increases with increased applied magnetic field and a compressive force resulted in larger apparent shear stiffness. Also, increasing loading frequency resulted in larger apparent shear stiffness and lower magnetorheological effect and similarly, however, a compressive force resulted in smaller magnetorheological effects.
Active and Passive Smart Structures and Integrated Systems 2017, 2017
This study presents the design, development, testing, and performance evaluation of a scaled brid... more This study presents the design, development, testing, and performance evaluation of a scaled bridge bearing utilizing magnetorheological elastomer (MRE) layers as adaptive elements, which allow for a varying stiffness under a magnetic field. The adaptive bridge bearing system incorporates a closed-loop magnetic circuit that results in an enhanced magnetic field in the MRE layers. A new design is introduced and optimized using structural and magnetic finite element analyses. Two bearings and a test setup for applying simultaneous variable shear, constant compression, and a variable magnetic field on the bearing are fabricated. The adaptive bridge bearing results demonstrate the stiffness change of the bearing under different strain levels and loading frequencies, as well as the ability of the bearing to change its stiffness under different applied electric currents, which can be correlated to the applied magnetic field.
SPIE Proceedings, 2016
This study presents an adaptive bridge bearing that can sense structural loads and tune its prope... more This study presents an adaptive bridge bearing that can sense structural loads and tune its properties to mitigate structural vibrations. The bearing utilizes magnetorheological elastomer (MRE) layers which allow for an increased stiffness induced with a magnetic field. The system also features a MRE-based sensing system for sensing the structural wind and traffic load. The sensing system is capable of transmitting data wirelessly to a central logging computer for monitoring bridge performance and sending alerts in the case of a major event. The capability of the MRE-based sensing system for sensing structural loads and wireless transmission of data were investigated. The adaptive bridge bearing incorporates a closed-loop magnetic circuit that results in an enhanced magnetic field in the MRE layers. Results show the sensitivity of the MRE-based sensors and the performance of the wireless system, as well as the design and analysis of the tunable bridge bearing.
Structures Congress 2012, 2012
Two full-scale precast concrete cladding panels were tested in 2011 on a full-scale five-story st... more Two full-scale precast concrete cladding panels were tested in 2011 on a full-scale five-story steel fame building at the E~Defense shake table facility in Japan. The panels were designed according to common U.S. practice. Two issues evaluated were: 1) the effect of acceleration on the cladding panel, and 2) the effectiveness of the current slotted-bolt sliding connection to allow for inter-story earthquake motion. The cladding tests represented one type of standard US cladding facade design where cladding is designed to accommodate inter-story drift though racking of individual panels. Panels were cast in Japan but steel connections were designed and fabricated in the US to accurately simulate the behavior of American cladding construction. A 50 mm vertical seismic joint was installed between the two panels. Two full-height column cover panels were tested, a return cover 3D shape, and a flat panel. Instrumentation measured the acceleration of the panels and the movement of the slotted connections. Findings include the ability of slotted connections to slide while being accelerated in a full scale 3D seismic motion and development of fragility curves relating damage to panel and/or floor acceleration.
Structures Congress 2014, 2014
Six full-scale experimental studies of precast concrete facade have been completed in 2011/12 to ... more Six full-scale experimental studies of precast concrete facade have been completed in 2011/12 to evaluate the seismic performance of nonstructural building components. Experimental testing of cladding panels was completed at the nees@berkeley lab facility. Research findings are particularly relevant to seismic regions of the United States and other countries. The paper is targeted toward engineers directly responsible for facade design as well as the Engineer of Record for a building project. Researchers involved in code development and expansion of Performance Based Earthquake Engineering will also benefit from the paper. Specimens included full-width, half-width, and return column covers supported by an articulated steel test jig simulating a building structural frame. Steel connections between the panels and the supporting frame included slotted connections at the tops of panels and welded connections at the base of panels. The static loading protocol compared cyclic loading with increasing amplitude to a seismic loading protocol based upon the nonlinear time history drift of the prototype structure. The horizontal slotted connection at the top of panels allowed inter-story drift matching the building code requirements to occur with minimal damage to the panels, however once the inter-story drift increased above a point where the slotted connection reached the allowed travel, damage to the panel, in the form of severe cracking at embedded connections occurred. Force-deformation graphs of the global specimen and individual connections quantify the hysteretic behavior. Horizontal slotted connections clearly show minimal resistance to lateral movement while the displacement remains below the maximum allowance of the slot. Once this free clearance is reached, bearing of the slot significantly increases and the connection quickly increases lateral resistance. Welded connections show very little hysteretic behavior due to low levels of relative displacement. The concrete embeds of the weld plates show more pronounced hysteretic behavior as this is the main location of damage and cracking at the base connections. The primary goal of evaluating the connection force-deformation relationships is to develop suitable analytical models for use in nonlinear studies of the facade system. The presentation will clarify performance of modern facade systems and define the analytical modeling input data for researchers exploring holistic building performance.