UHPC connection for SDCL steel bridge system

Link to the Latest: September 2020 Progress Report

Background:

SDCL steel bridge system has been investigated thoroughly for non-seismic and seismic areas. SDCL bridge system provides a solution for ABC application of steel bridges. The current detail uses a cast-in-place concrete diaphragm over the middle pier to connect the steel girder and make them continuous (Figure 1). Application of an SDCL steel bridge system has many advantages including eliminating field splices, eliminating expansion joints, reduced negative moment over the pier, and minimized traffic interruption. Further, encasing the ends of the girder in concrete protects the girder ends and results in enhanced service life and lower inspection and maintenance costs if compared to conventional continuous steel bridge systems.

The current system has shortcomings that can be addressed by taking advantage of new advanced materials such as UHPC. By using the current SDCL detail, although the resulting closure time for the facility carried by structure is reduced if compared to the conventional methods of steel construction, but it might exceed the weekend closure time limits that is usually available for high traffic roadways. The reason is that normal strength concrete usually reaches its minimum required strength in more than a couple of days. Another issue with the current SDCL detail is the tight tolerances for steel fabrication. As the steel girders are placed on adjacent spans in this system the end detail of the girders (steel blocks) should be touching to prevent concrete diaphragm from crushing.

UHPC has been recently widely considered for ABC applications due to its superior mechanical properties, durability and also high early strength as compared to normal concrete. However, this material is more expensive than conventional concrete so it should be utilized strategically. In this research, the use of UHPC as diaphragm material is proposed that results in decreasing construction time for the facility carried, increasing the tolerances and simplifying the cast-in-place detail of the concrete diaphragm.

Objective:

1-        Developing finite element models capable of modeling the new proposed system;

2-        Studying the effect of connection parameters and details when the diaphragm is made of UHPC, therefore there are opportunities to simplify the end girder details;

3-        Developing tentative design guidelines for UHPC connection; and

4-        Developing a research plan and road map to experimentally evaluate the proposed connection.

Scope:

An overview of the study tasks is given below.

Task 1 –  Conducting a literature review on the current practice of SDCL steel bridge system and UHPC

In this task, a comprehensive literature review will be conducted including the current construction of steel bridges and SDCL bridge system, especially for ABC applications. Also, the developments in the material technologies and UHPC will be reviewed to accurately model the UHPC material properties in the numerical study.

Task 2– Validating the numerical models

In this task, a set of models will be developed to match the experiments performed for the development of SDCL system. This assumptions in the models will be used later for other tasks.

Task 3– Performing a parametric study  

In this task, based on the developed validated models, UHPC will be modeled and a parametric study will be performed to understand the behavior of the connection in various loading conditions.

Task 4–  Developing design recommendations and experimental research plan 

In this task, based on the findings of the numerical study tentative design guidelines will be developed and proof of concept experiments will be designed.

Task 5 –  Final Report

In this Task, Full assessment of the findings from Task 1 throughout Task 4 will be conducted and a report will be published including design recommendations and experimental research plan for proof of concept.

 

Research Team:

Principal Investigator:  Dr. Atorod Azizinamini

Research Assistant: Amir Sadeghnejad

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