Nonlinear and Probabilistic Theory for Concrete Creep
{'Code': '07030000', 'Directorate': {'Abbreviation': 'ENG', 'LongName': 'Directorate For Engineering'}, 'Division': {'Abbreviation': 'CMMI', 'LongName': 'Div Of Civil, Mechanical, & Manufact Inn'}}
{'SignBlockName': 'Ken Chong', 'PO_EMAI': None, 'PO_PHON': None}
The linear modeling of concrete creep with aging has matured, and               it is now appropriate to develop a nonlinear theory.  This                      research will establish such a theory, based on micromechanics                  analysis of the solidification process of portland cement and                   nonlinearities due to strain-hardening and development of                       backstress.  The model will first be developed for basic creep at               constant humidity and temperature, and is then generalized to                   include the effects of variable humidity and temperature.  This                 model is based on the hypothesis that the rate of bond ruptures                 (which is the source of creep) depends on the microdiffusion flux               of water molecules in cement gel.  The model will be extended to                include probabilistic aspects of materials parameter uncertainty,               including correlation of random parameters, and fluctuation of                  environmental conditions.  Random effects of environment are                    handled by a new sampling scheme based on spectral approximations               and approximate solutions from diffusion theory.  A numerical                   algorithm for step-by-step integration in time in finite element                programs will also be developed.  Creep experiments will be                     conducted with a novel large triaxial-torsional testing machine                 with temperature control.  Hollow test cylinders will be                        subjected to triaxial loading at various temperatures with                      confining pressure which prevent cracking or simultaneous strain-               softening due to drying or temperature change.  The results will                improve creep predictions for radioactive waste storage, large                  span bridges nuclear reactor accidents, concrete shells and                     tanks, buildings and other concrete structures.
{'FirstName': 'Zdenek', 'LastName': 'Bazant', 'PI_MID_INIT': 'P', 'PI_SUFX_NAME': None, 'PI_FULL_NAME': 'Zdenek P Bazant', 'EmailAddress': 'z-bazant@northwestern.edu', 'NSF_ID': '000467578', 'StartDate': '01/01/1989', 'EndDate': None, 'RoleCode': 'Principal Investigator'}
{'Name': 'Northwestern University', 'CityName': 'EVANSTON', 'ZipCode': '602080001', 'PhoneNumber': '3125037955', 'StreetAddress': '633 CLARK ST', 'StreetAddress2': None, 'CountryName': 'United States', 'StateName': 'Illinois', 'StateCode': 'IL', 'CONGRESSDISTRICT': '09', 'CONGRESS_DISTRICT_ORG': 'IL09', 'ORG_UEI_NUM': 'EXZVPWZBLUE8', 'ORG_LGL_BUS_NAME': 'NORTHWESTERN UNIVERSITY', 'ORG_PRNT_UEI_NUM': None}
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[{'Code': '1442', 'Text': 'CONSTRUCTION AND INFRASTRUCTUR'}, {'Code': '9120', 'Text': 'CROSS-DIRECTORATE PROGRAMS'}]
{'url': 'https://www.nsf.gov/awardsearch/download?DownloadFileName=1988&All=true', 'xml': '8815166.xml'}