NC-UHPC Composite Structure for Long-Term Creep-Induced Deflection Control in Continuous Box-Girder Bridges

An innovative normal concrete (NC) with partial use of ultrahigh-performance concrete (UHPC) composite structure is proposed in this paper to reduce the long-term creep-induced deflection in continuous box-girder bridges. The creep properties of NC-UHPC composite columns were experimentally investigated, and test results showed that the creep coefficients in NC-UHPC composite columns decreased considerably compared with NC columns. A creep computational model of the NC-UHPC composite was further developed to describe long-term creep behaviors of the composite columns in good agreement with the test results. Based on the proposed creep model, the long-term behaviors of a long-span box-girder bridge, made of the NC-UHPC composite, were evaluated by finite-element analysis (FEA), and the influences of the UHPC area fraction and the length of embedded precast UHPC columns were also discussed. Compared with the traditional prestressed concrete (PC) box girder, the long-term creep-induced deflection at the midspan of the NC-UHPC composite bridge reduced by 54.5%. The NC-UHPC composite is, therefore, conceived to be one of effective solutions for long-term creep-induced deflection control of long-span continuous PC box-girder bridges. (c) 2018 American Society of Civil Engineers.