Numerical Investigation of the Impact of Vertical Ground Motions on ABC Girder-to-Cap Connections in the Near-Field

Project Information 

Link to Latest Report: Coming Soon

Background:

State-of-the-art research on the impact of vertical motion effects on ordinary highway bridges and evidence from past earthquakes have revealed the potential for a significant increase of the demands at the girder-to-cap face. While this is not of major concern for ordinary bridges whose moment capacity at the face of the bent cap is typically adequate to resist the increased demands due to vertical effects, the impact of vertical ground motions on ABC connections is yet to be thoroughly investigated. Very few studies have been carried out to characterize the shear and moment capacity of girder-to-cap connections. Experimental works have primarily looked at the seismic response of precast concrete girder-to-cap connections subject to horizontal excitation, while numerical studies have utilized only conventional simplified approaches for vertical ground motions estimates and modeling. This project will perform a comprehensive series of numerical simulations to assess the seismic performance of bridge systems that incorporate typical ABC girder-to-cap connections. This will be accomplished by utilizing validated 3-D arrays of near-field motions generated from physics-based wave propagation models.

Objective:

The proposed research will be exclusively based on detailed modeling and advanced numerical simulations of the nonlinear dynamic response of bridge structures that incorporate ABC connections. The structural modelling part will be addressed with a two-level approach.

Scope:

In the following is a summary of the research activities proposed in this project organized in 6 separate tasks.

Task 1 – The objective of Task 1 is to conduct a comprehensive literature review on the girder to-cap ABC connections currently utilized in design practice to identify a specific prototype of ABC connection that will be utilized for conducting the numerical investigation proposed in this study. In parallel, a separate state-of-the-art literature review will be conducted to identify representative bridge pier columns that have been experimentally tested and that can be utilized to conduct the validation and sensitivity study on the reduced-order model built in OpenSees.

Task 2 – The objective of Task 2 is to develop a detailed model of the ABC connection identified in Task 1 and conduct a series of static and dynamic tests under different load patterns. This activity will be aimed at identifying the connection global constitutive relationship, as detailed in the previous section.

Task 3 – The objective of this task is to construct a reduced-order model of the ABC connection in the OpenSees environment that is able to capture the main aspects of the global response as characterized in Task 2.

Task 4 – The objective of this task is to build a reduced-order model of the full bridge with the use of OpenSees that incorporates the ABC connection model developed in Task 3.

Task 5 – The objective of this task is to identify a statistically significant suite of arrays of nearfield motions and perform nonlinear dynamic analyses by adopting a multi-support load pattern.

Task 6 – The objective of this task is to provide an extensive analysis of the simulation results that can constitute the basis for the development of guidelines for the incorporation of spatially varying vertical ground motions effects in the design of ABC girder-to-cap connections. Simplified measures to advance current design methods in the framework of the capacity design will be proposed. A comprehensive comparison of the demand posed to the girder-to-cap connections as obtained from a statistically significant population of arrays of near-field simulated records and state-of-the-art methods will be provided.

Research Team:
Principal Investigator: Floriana Petrone
Co-Principal Investigator: Mohamed Moustafa