Research | Arjun Jayaprakash

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Projects

Direct Displacement-based Seismic Design of Steel Substructures with External Socket Connections

External sockets that connect steel piles/columns to their cap-element in bridges provide a simple and elegant way of relocating plastic hinge formation to the columns. This mechanism is imperative to a successful performance of these bridges under earthquakes. However, there have not been any studies that provide guidelines/recommendations for the seismic design of such systems. What is unique to these systems with external sockets is the mechanism of socket action that introduces additional flexibility, which in-turn results in underprediction of structural displacements via. conventional methods. From the perspective of displacement-based seismic design (DDBD), it is crucial that these extra displacement components be accounted for. This study proposes a simple model that can be invoked by hand calculations to perform DDBD of steel substructures with socket connections. To learn more regarding the seismic design of these systems, click here…

Structural Consequences of the Grouted Shear Stud Connection

The grouted shear stud (GSS) connection is a steel bridge column to cap-beam connection developed as an alternative to conventional directly welded connections. The directly welded connections have been shown to fail prematurely in a brittle fashion which is undesirable for seismic design. The GSS connection eliminates any failure at the weld interface by relocating failure on to the columns. This failure is ductile. To learn more on the long term behavior of this connection, click here…

Characterizing Earthquake Loading History - A Pilot Study History

Current earthquake hazard intensity measures such as peak ground accelerations, spectral accelerations, spectral displacements etc. do not capture the load history characteristics of real ground motions. A new parameter called “Opposite Peak Ratio” that captures peak spectral response displacements on either side of equilibrium position is investigated for potential utility as an input parameter in state-of-the-art limit state models. To learn more, click here…

Sensitivity of NLTH Analysis of MDOF Bridges to Choice of Viscous Damping Models

There has been a rising interest among engineers to conduct non-linear time history (NLTH) analysis as part of the seismic design procedure for bridges. Strength and stiffness in dynamic analyses are well understood but the viscous damping model that is mostly being used in commercial analysis programs, namely initial stiffness proportional Rayleigh damping, is questionable. This study investigated the impact of using different viscous damping models to perform NLTH analysis on bridges. 42 NLTH analysis were performed on MDOF bridge fiber based models, each analysis having a different combination of specified variables. The variables were classified based on bridge geometry (2 models), ground motion intensity (3 intensities), abutment fixity conditions (2 conditions) and viscous damping models (4 models). The results were used to assess the sensitivity of response prediction to use of different viscous damping models. It was found that the responses are sensitive to the choice of damping models. To learn more, click here…

Durability of Cementitious Grouts in Cold Climate

The grouted shear stud (GSS) connection for steel bridge substructures was developed as a ductile alternative to directly welded column-to-cap-beam connections. During an earthquake, the GSS connection relocates the plastic hinge to the bridge column and eliminates brittle cracking at the weld region thereby providing full strength and ductility capacity. However, the grout material used for fabrication of the GSS connection is susceptible to damage through years of exposure, especially to extreme cold climates. We evaluated the durability of the grout material in cold-climates. A series of experiments was performed to ascertain the durability of commonly available high-strength cementitious grouts. While there were grouts that exhibited good durability, inconsistencies within the material were observed. Find out more in this article…

Presentations

“Predicting the Complete Non-Linear Response of Two-Column Steel Bridge Piers with Socket Connections”. Structural Engineering and Mechanics Symposium at NC State University, Raleigh, NC, USA, February 28, 2020. (PDF)
“Structural Consequences of Grout Deterioration in the GSS Connection”. Structural Engineering and Mechanics Symposium at NC State University, Raleigh, NC, USA, March 1, 2019. (PDF)
“Durability of Cementitious Grouts in Cold Climate”. Research Workshop at Alaska Department of Transportation and Public Facilities, Juneau, AK, USA, May 6-8, 2019. (PDF)
“Structural Performance of the GSS Connection”. Research Workshop at Alaska Department of Transportation and Public Facilities, Juneau, AK, USA, May 6-8, 2019. (PDF)
“Characterizing Seismic Load History for Performance Based Design”. 12th Canadian Conference on Earthquake Engineering (CCEE 2019), Quebec City, QC, Canada, June 17-20, 2019. (PDF)
“Is the Grouted Shear Stud Connection Durable in Cold Climates?”. Bridge Engineering Institute Conference 2019 (BEI 2019), Honolulu, HI, USA, July 22-25, 2019. (PDF)

Dissertation

Posters

Seismic Performance Limit-States of Steel Bridge Piers with Socket-type Connections. (PDF)
Durability of the Grouted Shear Stud Connection in Cold Climate. (PDF)