Evaluation of MEPDG with TxDOT Rigid Pavement Database (FHWA/TX-09/0-5445-3)

15. Supplementary Notes Project performed in cooperation with the Texas Department of Transportation and the Federal Highway Administration. 16. Abstract TxDOT initiated the rigid pavement database project to collect information on the general performance of portland cement concrete (PCC) pavement as well as to collect project-level information on PCC pavement responses and performance. A total 27 sections were selected statewide and detailed information was collected such as load transfer efficiency at small, medium, and large crack spacing and for two different seasons: summer and winter. Also collected were crack spacing information and slab deflections. Efforts were made to calibrate the punchout model in MEPDG. Review of the punchout model in MEPDG revealed that it is quite sophisticated, with a number of variables involved. It assumes that longitudinal cracking is induced by top-down cracking. The model is more applicable to CRCP with an asphalt shoulder. On the other hand, the model might not be appropriate for the punchout analysis of CRCP with tiedconcrete shoulder. Sensitivity analyses were conducted to investigate the effects of selected input variables on punchouts. Zero-stress temperature (ZST) had quite a large effect, because crack width and LTE depend to a large extent on ZST. The MEPDG equation for crack width tends to over-predict crack width and appropriate calibration constant needs to be determined. The comparison of actual punchout with a predicted value from MEPDG using national calibration constants shows a marked difference. MEPDG over-predicted punchout more than 30 times. When the calibration constant for crack width was reduced from 1 to 0.5, the predicted punchout became more reasonable. It appears that many distresses identified and recorded as punchouts in Texas are not actually punchouts caused by structural deficiency. Rather, most of them are due to imperfections in design details and/or construction/materials quality issues. Horizontal cracking appears to be the major cause of distresses in CRCP in Texas. The interactions between longitudinal steel and concrete in response to dynamic wheel loading applications appear to be the cause of horizontal cracking. Efforts should be made to accurately identify punchout during field evaluations. At this point, the punchout information in TxDOT’s PMIS doesn’t appear to be accurate. Manual for administrator of the database developed in this study is contained in this report. 17.