Browsing by Subject "Cracking"

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Crack-based damage assessment of in-service reinforced concrete bridge members
(2017-08-09) Zaborac, Jarrod; Hrynyk, Trevor; Bayrak, Oguzhan
Reinforced concrete bridge infrastructure is typically evaluated based on visually observed cracking/damage. However, traditional inspection procedures typically provide little-to-no insight into the remaining capacity of the inspected member. Although more rigorous methods have been proposed in the literature that offer quantitative insight into a structure’s health (with various levels of success), no procedure has been widely adopted. Furthermore, many of these proposed procedures have not been validated by experimental data. Experimental visual crack data were collected into a database to provide researchers and practitioners a means of developing and evaluating crack-based shear strength assessment procedures. The database has an emphasis on members which are similar in detail or scale to typical bridge elements. The database was subsequently used to evaluate a proposed mechanics-based damage assessment procedure based on an inverse solution of the modified compression field theory. In addition to visually observed crack characteristics (e.g., crack width and inclination), the proposed procedure relies upon basic material properties and design details. Average load proportions are estimated as a part of the procedure, therefore actual loading conditions (e.g., M/V∙d ratio for a beam) need not be known to calculate an estimate of an element’s residual capacity. Results from 420 analyses on beams from three experimental programs carried-out with the procedure show the potential of a mechanics-based procedure for the crack-based shear strength assessment of reinforced concrete bridge members. The average predicted-to-experimental ratio for normalized shear strength (i.e., capacity-in-use) was reasonable for two of the experimental series (0.98 – 1.17); however, results from the third group of beams trended much more conservatively (average predicted-to-experiment ratio of 1.43). Overall, the procedure is relatively simple and general in its application and shows promise as an evaluation tool.
Designing for deck stress over precast panels in negative moment regions
(2017-10-27) Munsterman, Keaton; Helwig, Todd Aaron, 1965-
One of the leading causes of structural deficiencies in the United States Bridge Inventory is related to deterioration and durability problems with concrete bridge decks (NCHRP 2004). The primary issue with bridge decks is related to cracking of the concrete that provides a direct conduit for moisture and other corrosion agents to permeate and attack the reinforcing steel. Adequate reinforcing steel is needed in the deck to minimize crack widths and therefore limit corrosion of reinforcing steel. A particular case of interest occurs when the bridge deck is constructed using partial-depth precast concrete deck panels (PCP) with cast-in-place (CIP) concrete topping. When this type of deck construction is used over the negative moment region of continuous steel or concrete girders, the amount of reinforcing steel that should be placed within the CIP concrete topping to provide adequate crack control is not currently well understood. This thesis is part of a larger study being conducted for the Texas Department of Transportation that is examining this issue. In the study reported in this thesis, two newly constructed bridges were instrumented to monitor the behavior of the bridge deck. These bridges did not use continuous girders, but rather had simply supported prestressed concrete girders, with a bridge deck constructed using a “poor-boy” construction joint detail over interior bents. Each bridge utilized three different reinforcement layouts centered over an interior bent within the poor-boy joint detail. Strain gages in each portion provided constant readings to display the distribution of strain across the bridge deck. Each bridge was monitored over a period from when the deck was cast until when the bridge was opened to traffic. Live load tests were also conducted to provide data on strains induced by heavy trucks. Based on the field data, no clear correlation was found between the amount of steel added and the strain measured. However, based on the measured data combined with field observations of cracking, the current standard reinforcement appears to be adequate in controlling the crack widths for the poor-boy deck detail. While the poor-boy deck joint detail is different from deck details used over negative moment regions of continuous girders, this data provides useful insights in to bridge deck behavior that will help guide future phases of the larger study.
Measurements of intact and cracked concrete structural elements by the SASW method
(1994) Kalinski, Michael E. (Michael Edward), 1963-; Stokoe, Kenneth H.
Research was conducted to apply the Spectral-Analysis-of-Surface-Waves (SASW) method to the identification of internal cracking in concrete structural elements such as beams and columns. The SASW method is a nondestructive technique which involves the propagation of surface stress waves along the exposed face of a structural element. By yielding the relationship between wave velocity and wavelength of the surface wave energy, the SASW method provides information about how the stiffness of a material varies with depth. SASW measurements were made on intact and cracked concrete structural elements. Surface waves propagated through cracked concrete at consistently lower velocities. These velocity reductions corresponded to the presence of visibly detectable cracking and, in some cases, occurred in the absence of visible cracking. This result demonstrated the ability of the SASW method to detect otherwise hidden damage. When the cracks were reclosed by the application of a compressive load, the surface waves propagated at velocities comparable to those of uncracked concrete. In addition to performing velocity measurements, material damping measurements were made on intact and cracked concrete structural elements. These measurements revealed that the presence of cracking can be qualitatively assessed through an increase in observed surface wave material damping, with material damping ratios ranging from less than 1% in undamaged concrete to around 3% in damaged concrete
Structural assessment of reinforced concrete infrastructure
(2023-05-01) Zaborac, Jarrod; Bayrak, Oguzhan, 1969-; Hrynyk, Trevor; Williamson, Eric; Murcia-Delso, Juan; Calvi, Paolo
The assessment of reinforced concrete infrastructure is a growing challenge facing the structural engineering community. Traditional strategies for assigning bridge condition states rely on subjective experience and qualitative methods. There is a demand for more advanced methods that can provide quantitative, objective insight into the implications of measured cracking distress to address the evolving needs of the infrastructure renewal community. Three methods for determining the severity/impact of observed cracking are presented. These three methods represent novel extensions of basic reinforced concrete mechanics theory and provide quantitative output that can assist in infrastructure renewal decision-making processes. Two complementary/accompanying experimental studies are also presented. These experimental studies resulted in the unique testing of previously in-service structures, as well as a substantial contribution to the database of well-documented crack data.