Research Project Statement 16-33
FY 2016 Annual Program
Form ProjStat
(Rev. 5/2013)
(RTI)
Title:
The Problem:
Technical
Objectives:
Non-Contact Splices at Drilled Shaft to Bridge Column Interfaces
The interface between drilled shaft foundations and bridge columns typically requires a construction joint and splicing of reinforcing steel. The design of such connections is very straightforward for columns and drilled shafts with circular cross-sections, and for cases involving a footing as a transition element.
However, if the drilled shaft to column connection involves a square or rectangular column cross-section framed directly with a circular drilled shaft, there are a number of issues where design guidance is not clear and may require advanced modelling validated by testing to ensure desired structural behavior. This geometric interface will likely have a reinforcing steel splicing arrangement with non-contact lap splices, which has limited guidance cited in the AASHTO LRFD Bridge Design Specifications, Section 5.11.5.2.1.
These requirements were based on limited scope tests published in WSDOT-TRAC Report WA-RD 417.1
“Noncontact Lap Splices in Bridge Column-Shaft Connections.” This research only examined the case of round columns with a diameter smaller than the supporting drilled shaft.
The frequency of conditions of non-circular columns interfacing directly with drilled shafts is increasing for the following reasons:

A desire for more aesthetic rectangular or more complex column cross-sections compared to round columns that frame with drilled shafts.

Limited room for construction due to maintenance of traffic requirements and a desire for fewer construction steps (which equates to faster construction), making the solution of multiple foundations and an intermediate footing undesirable.
A better understanding of behavior and design guidance is needed, especially for bridge substructures with columns that experience significant flexural or tensile demand. This will ensure the target level of safety associated with these structures.
This research will focus on expanding the design criteria of the interface between drilled shaft foundations and bridge columns. In the course of this research, some important aspects will be considered:

Influence of distance that may vary between non-contact spliced bars on the splice development length and confinement required, considering these interface geometries.

Since columns can have significant flexural demand in specific situations, definition of demand-to-capacity limits or other appropriate criteria where columns with these types of interfaces may require the maximum 6-inch non-contact splice spacing limits dictated for
“flexural members” per AASHTO LRFD 5.11.5.2.1, or other limits developed by the researchers.

Present code language is vague and can lead to the conclusion that large spacing for noncontact splices is allowed in drilled shafts even though the flexural demand can be higher in the upper reaches of these members.

Influence of termination details for non-continuous column and drilled shaft reinforcing.
 For common “in-board” dowel arrangements, analytical methods validated with physical testing to account for possible local reduced stiffness.

Focusing on the most representative column to drilled shaft connections and most important variables, such as relative member dimensions, reinforcing steel ratios, reinforcing plan arrangement, confinement steel, reinforcing steel lengths, non-contact areas above and/or below column/drilled shaft interface.
Current code provisions were based on tests that only tested Grade 60 reinforcing. This research needs to provide guidance for both Grade 60 and Grade 100 reinforcing.
Project Statement 16-33

Form ProjStat
(Rev. 5/2013)
(RTI)
Desired
Deliverables:
The research products should include:
 Value of Research (VoR) as a that includes both qualitative and economic benefits.

Monthly progress reports.

Report documenting results of literature survey, analytical studies, and physical testing.

Half-day workshop describing the research work and demonstrating design examples and any required modelling for the design of these connections.
Proposal
Requirements:
1.
Utilize the deliverable based templates (see the appendices provided or in the University
Handbook).
2.
Proposals will be considered non-responsive and will not be accepted for technical evaluation if they are not received by the deadline or do not meet the requirements stated in RTI’s University
Handbook.
3.
Proposals should be submitted in PDF format, 1 PDF file per proposal. File name should include project name and university abbreviation.
Pre-Proposal
Meeting
Information:
Friday, September 11, 2015 9:00 – 12:00
Austin Riverside Campus
118 E. Riverside Dr.
ENV Conference Room, 1st Floor, 1B1A
Webex Information:
Join the online meeting:
Go to:
Teleconference information;
Provide your phone number when you join the meeting to receive a call back. Alternatively, you can call:
Call-in toll-free number: 1-866-6371408 (US)
Conference Code: 199 125 9183
Proposal
Deadline:
Proposals are due to RTI by 4:00 p.m. Central Time, October 12, 2015. Email submissions should be sent to rtimain@txdot.gov.
Project Statement 16-33