Envisioning Connection detail for Connecting Concrete Filled Tube (CFT) columns to cap beam for High Speed Rail Application

Link to Latest Report: December 2019 Progress Report

Background
AASHTO LRFD Bridge Design Specification, through AASHTO SCOBS T-14 committee (Steel Bridges) have recently developed design provisions for use of Concrete Filled Tube (CFT) columns for bridge elements, such as columns in substructure. In the case of High Speed Rail (HSR), about 60 to 70% of the HSR infrastructure consists of elevated bridge structures. In one recent case in California, a segment of the High-Speed Rail (HSR) consists of elevated bridge structures with spans of about 110 to 150 ft. with columns, ranging in height from very short to as tall as 100 ft. The use of pre-fabricated sub-structure elements could significantly reduce costs and expedite the HSR project delivery. U.S. DOT has identified the use of HSR as a strategic area for addressing mobility challenges.  The development of an efficient substructure system for HSR is therefore urgent and will result in significant savings. The recent adaptation of CFT columns by AASHTO LRFD Bridge Design Specification is the first step. The development of an efficient substructure system for HSR using CFT columns, demands the development of a cap beam system and their connection to CFT columns.

This project is a joint investigation with the University of Washington. The FIU project will concentrate on the development of a connection capable of connecting the cap beam system to the CFT column, while the University of Washington will concentrate on developing a pile cap system that could be utilized in conjunction with CFT columns. Together, these two projects, combined with existing information about CFT columns, will provide an economical substructure alternative system for HSR that will be presented to HSR authority for additional development and implementation.

Objective
The main objective of this project is to develop a sufficient amount of data and proof of concept test, for system(s) that could be used to connect the cap beam to CFT columns. The project will involve numerical, experimental and analytical approaches. California HSR Authority will be asked to serve on the advisory committee of the project and be involved in the project from the outset.

Scope
The following is a brief description of the work to be conducted

  • Task 1 –   Literature Search
    • There is a need to conduct a literature search and comprehend the recent developments in the area of connections to CFT columns. This should assist the research team, to achieve the project objectives on a timely manner
  • Task 2 – Review of Design Provisions for HSR
    • Under this task different design philosophies around the world, especially those practiced in China, Far East and Spain will be examined, to select at least design philosophies that is believed to be reasonable, economical and practical. This will be in addition to the design philosophy currently used CA HSR Authority.  The development of connection details will be within these two design philosophy contexts.
  • Task 3 – Envisioning connection Details
    • Under this task, using primarily numerical modeling, in the form of Non-Linear Finite Element Analysis, connection detail(s) will be developed for connecting CFT columns to cap beam. The numerical model will be calibrated using the experimental work described under task 4.
  • Task 4 – Proof of Concept Experimental Work
    • Under this task, a limited number of experimental work at small or larger scale will be carried out to examine feasibility of using the suggested connection detail(s) and calibrating the numerical models. Using the calibrated numerical model, additional work may be conducted to refine the connection detail, if needed, under task 3.
  • Task 5 – Final Report
    • Final report summarizing the project activities will be developed.

Research Team:
Principal Investigators:  Dr. Atorod Azizinamini
Research Assistant: Sheharyar e Rehmat

Previous Progress Reports: