Durable UHPC Columns with High-Strength Steel

Latest Progress Report: December 2017 Progress Report

 

Background:
Rapid deterioration of bridge substructures has been one of the major reasons for the current need of rebuilding the nation’s infrastructure. Older bridges are originally designed for a 50-year service life, but ongoing repairs/retrofits and newer construction aim at extending service life to 75 or 100 years. Moreover, bridge substructures in harsh aggressive environments are even suffering faster deterioration. Thus, protecting and building durable bridge substructures is of national interest. Using durable materials with very low porosity such as ultra-high performance concrete (UHPC) is one way to achieve such goal. In addition, the exceptional mechanical properties of UHPC will lead to compact substructure elements and provide a plausible solution for ABC construction where lighter and easier-to-handle and transport bridge components can be pre-fabricated and shipped to the site. Currently, most of the UHPC applications are limited to bridge deck joints and ABC connections. Only few studies considered UHPC at the full structural elements, and no previous studies properly focused on design optimization using UHPC. Using high-strength steel (e.g. Grade 100) with UHPC can further reduce bridge elements size and promote durable and sustainable ABC, which is the goal of this project.

Objective:
The objectives of the research are:

  1. Provide the knowledge needed to optimize the seismic design of pre-fabricated bridge columns using UHPC and high-strength steel.
  2. Study the confinement behavior of UHPC for proper seismic detailing and design.
  3. Conduct large-scale tests to verify and investigate the seismic performance (e.g. plastic hinge behavior) of UHPC columns with high-strength steel.

Scope:

  • Task 1 – Literature Review:  An extensive literature search will be conducted to comprehensively summarize the different applications of UHPC and high-strength steel in conventional and ABC bridges. The review will also focus on structural and seismic performance of full UHPC bridge components.
  • Task 2 – Pre-test analysis to design the experimental program and specimens:  Three-dimensional finite element modeling and analysis will be used to preliminary investigate the effect of longitudinal and transverse reinforcement detailing on structural and seismic response of UHPC columns. This is to finalize the test specimens design and parameters for the experimental program.
  • Task 3 – Conduct UHPC confinement tests:  Existing concrete confinement model (e.g. Mander model) have not been verified for UHPC. In this task, unconfined and confined UHPC cylinders will be tested and the obtained stress-strain relationships will be checked against existing confinement models.
  • Task 4 – Construct UHPC test specimens, and conduct quasi-static cyclic tests:  This task is the main core of the study and aims at testing several reduced-scale UHPC columns with high-strength longitudinal reinforcement under combined axial and unidirectional lateral quasi-static (cyclic) loading. Test parameters are varying longitudinal and transverse reinforcement details and using A706 Grade 100 steel in lieu of significantly increasing the reinforcement ratios for UHPC design optimization.
  • Task 5 – Process and interpret tests results:  The tests data will be evaluated to interpret and explain the structural and seismic response of UHPC columns with high-strength steel along with the effect of transverse reinforcement on confinement behavior and column capacity. This knowledge will be used to develop preliminary optimization and design guidelines for high performance durable UHPC columns with high-strength steel.
  • Task 6 – Final report:  A final report describing the details of different tasks and preliminary design guidelines for UHPC columns with high-strength steel will be prepared and submitted to the ABC-UTC steering committee and made widely available for dissemination.

Research Team:
Principal Investigator:  Mohamed Moustafa, Ahmad Itani
Research Assistant:  Negar Naeimi

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