Research Seminars @ Illinois

Load Rating and Repair of Precast Prestressed Concrete Bridge Deck Beams with Transverse Cracks

Advisor: Professor Bassem Andrawes

Abstract

This Ph.D. research aimed to investigate the effects of transverse cracks on the behavior and state of stress

in precast prestressed concrete (PPC) bridge deck beams and to develop efficient repair methods to improve

their load-carrying capacity. PPC deck beams are commonly used for short to medium span bridges and

account for about 9.7% of all the bridges in the U.S. The primary concern with PPC beams is their

susceptibility to cracking-related durability and performance issues. Since the early 21st century, extensive

research has been conducted on the effects and mitigation measures for longitudinal cracks in PPC deck

beam bridges. Yet there is a lack of knowledge on the impact of transverse cracking on the structural

integrity of these bridges.

Transverse cracks are a recent issue observed in older PPC deck beam bridges constructed before the 1990s.

These cracks occur at the soffit of the beam and are formed when the flexural tensile demand due to loading

is higher than the tensile strength of the concrete. These cracks could lead to a notable reduction in the

beam's capacity, buildup of stresses at the crack, and localized bond failures, thereby affecting the beam's

capacity and serviceability. There is a need to quantify the effect of transverse cracks on the performance

of these beams by relating the crack width to the loss in section capacity and the built-up stresses in the

beam components.

For transversely cracked beams, performing repair measures could extend their service life and improve

their load rating. External prestressing is a common repair technique, especially for prestressed concrete

elements. Nevertheless, conventional external prestressing methods have several drawbacks, including the

need for expensive equipment to prestress and anchor the strands, the requirement for sufficient space for

bulky steering blocks, instruments, and anchorage systems. These factors can deter bridge owners from

adopting these methods. Thus, innovative repair strategies are needed to overcome the limitations of

traditional external prestressing repair methods.

To address the identified issues, this dissertation focused on three main objectives: (1) Investigate the effect

of transverse cracks on beam behavior, stresses, and load rating. (2) Study the influence of variations in

material and geometric behavior on the relation between the width of the transverse crack and the residual

capacity, built-up stresses, and load rating of the cracked beams. (3) Propose and assess external prestressing

repair methods using shape memory alloys (SMA) to overcome practical issues associated with

conventional repair methods. To fulfil these objectives, three in-service PPC deck beams were extracted

from two existing bridges in Illinois and used in this research. The beams were experimentally and

numerically studied to understand the effect of transverse cracks on their behavior and load rating.

Parametric studies were conducted to assess how variations in material and geometric properties affect the

behavior of damaged beams. The results of the parametric studies were used to develop guidelines for

conducting load rating analysis on transversely cracked PPC deck beams with rectangular and circular

voids. Furthermore, two external prestressing repair strategies using SMAs were investigated

experimentally and numerically: Voided Shape Memory Alloy-Precast Prestressing Plate (SMA-PPP) and

Shape Memory Alloy-Coupled Prestressing Plates (SMA-CPP). Both external prestressing methods utilize

the shape memory effect of SMA, allowing deformed SMA bars and wires to shrink and recover their

original shape upon heating. The proposed repair methods do not require external anchorage or fastening

systems, nor do they involve in-situ mechanical stressing with hydraulic jacking equipment.