Experimental investigation on UHPC shrinkage of full-scale steel-UHPC composite bridge deck

Three full-scale composite bridge deck segments with various steel-to-UHPC area ratios, as well as free shrinkage specimens, were tested to investigate the restrained shrinkage and cracking behaviors. Based on the measured UHPC strain and temperature, the variations in shrinkage strain were analyzed, and a time-varying analysis theory for calculating elastic modulus and shrinkage stress during UHPC curing process was proposed. The results revealed that UHPC free shrinkage strain (after 30 days) was within 700–750 με. The variation trend in UHPC elastic modulus and shrinkage stress were basically consistent the development of shrinkage strain. The shrinkage tensile stress at UHPC upper surface was approximately 2 MPa, equaling to the difference between cracking stress and axial tensile strength. Based on the free and restrained strains, a time-dependent equivalent stress method was found to be effective for calculating UHPC elastic modulus and shrinkage stress in the composite deck.