Date of Award

5-2026

Degree Name

Doctor of Philosophy

Department

Civil and Construction Engineering

First Advisor

Upul Attanayake, Ph.D., P.E.

Second Advisor

Haluk Aktan, Ph.D., P.E.

Third Advisor

Purushotham Pakala, Ph.D., P.E.

Keywords

Finite element modeling (LARSA 4D Abaqus), post-tensioned concrete tie girders, seasonal strain and temperature effects, skewed unbraced network tied-arch bridge, structural health monitoring (SHM)

Abstract

This dissertation work investigated the structural performance of the 2nd Avenue Bridge in Detroit, Michigan, the first skewed, unbraced network tied-arch bridge in the U.S. The 245-ft long, 96.5-ft wide bridge features an 18-degree skew. The bridge was constructed using accelerated bridge construction (ABC) techniques, including off-site fabrication at a bridge staging area (BSA) and installation via self-propelled modular transporters (SPMTs) and lateral launching, enabling the completion of construction with minimal disruptions to I-94 traffic and improved safety.

Given the unique structural configuration of the bridge, the use of innovative construction techniques, and differences observed in structural responses predicted by three independent finite element models, this work was initiated to: (i) evaluate structural performance during construction from the data acquired during construction, (ii) conduct load testing to establish an operational baseline for the structure, (iii) establish structural response under intrinsic and live loads, and (iv) evaluate the performance of the structure during seasonal changes.

An instrumentation system consisting of 96 vibrating wire (VW) strain gauges and 16 VW strandmeters was designed and installed on the bridge to monitor strains and temperatures. Approximately two years of data were collected from the complete bridge, from September 28, 2023, to December 2, 2025.

The results show that construction staging, including post‑tensioning, the SPMT move, lateral launch, and lowering onto permanent bearings, produced significant but controlled stresses in the post‑tensioned tie girders, knuckles, and end diaphragms, with the final state of stress remaining within design limits. Seasonal monitoring revealed that both strain and temperature exhibit periodic variations resembling a sinusoidal function with a phase shift, and that thermal effects dominate the long‑term response of the post-tensioned (PT) frame. A diagnostic static load test, conducted approximately ten months after opening using eight tandem trucks (about 416 kips, or 50% of the HL‑93 Mod design load) placed in six configurations, produced small strain changes on the order of 20 με at instrumented sections, indicating high stiffness and low sensitivity to live loads under the tested conditions.

To interpret the measured behavior and evaluate design assumptions, global and refined finite element models of the bridge were developed in LARSA 4D and Abaqus, respectively. The LARSA 4D model incorporated staged construction, time‑dependent concrete behavior based on fib Model Code 2010, and tendon and hanger modeling consistent with the construction sequence, and was validated against load‑test responses. The refined Abaqus model captured three‑dimensional stress distributions in critical regions such as the tapered knuckles and tie girder–knuckle transitions and reproduced time‑dependent strain histories at key sections with good agreement in magnitude and trends.

By superimposing construction‑stage stresses and design thermal ranges, stress‑based operational limits were established for the PT frame and knuckles, showing that total stresses under in‑service conditions remain below the additional stresses required to reach design tensile and compressive limits as long as temperatures remain within the design range. Therefore, the structure can operate safely as long as the temperature remains within the design limits. Collectively, the monitoring data, operational baseline, and calibrated FE models provide a framework for assessing the performance of the 2nd Avenue Bridge over time and offer practical guidance for the design, analysis, and structural health monitoring of future skewed, unbraced network tied‑arch bridges.

Access Setting

Dissertation-Open Access

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