| This purpose of this project is to investigate the serviceability behavior of discontinuity regions using the strut and tie modeling method. To accomplish this objective, the following aims are targeted:(1) to investigate the serviceability behavior of concrete in terms of maximum crack width and tie strain estimated in representative STM;(2) to investigate the serviceability behavior of concrete in terms of total crack area and strain energy estimated in representative STM and;(3) to recommend a procedure for distinguishing a 'good' strut and tie model from a 'bad' model. A secondary goal of this project is to refine existing methods for processing digital images in the collection of crack width, crack area and displacement data. This effort is accomplished by testing twelve concrete deep beams with a 10x20 in. cross-section. Experimental variables include web reinforcement ratio and spacing, shear span-to-depth ratio, and configuration of the primary tension reinforcement. An extensive amount of data are collected to establish serviceability behavior including, maximum crack width, area of cracked surface, and displacement of targets placed on a 3-inch grid on beam surfaces. Findings indicate a strong correlation between crack area and strain energy in a representative strut-and-tie model for beams with an a/d of one. For beams with an a/d of two, the correlation is offered more strongly by modeling assumptions and alternate load paths. It is recommended to limit the estimated strain within the ties of a strut-and-tie model to achieve acceptable serviceability performance and predictable crack widths. This study represents an improved design approach for estimating the serviceability performance of reinforced discontinuity regions. |
