Experimental and numerical study of π-shaped hybrid bridge piers with steel cap beam and innovative joint designs

Abstract

To address the transportation and hoisting difficulties caused by excessive self-weights of traditional concrete cap beams, π-shaped hybrid piers with prefabricated steel cap beams and concrete columns were proposed. Moreover, two innovative cap beam–column joint designs using the flange-rebar-ultra high performance concrete (UHPC) connection and the rebar-concrete connection, were developed. Two large-scale (1:4) specimens of hybrid piers with different joint configurations were tested. Both specimens failed due to local buckling at the web and bottom plates of steel cap beams, while the joints and concrete columns remained integrity. They exhibited ultimate bearing capacities of 1023 and 878 kN, with maximum vertical displacements of 59.8 and 21.5 mm at the cantilever beam ends, respectively. Finite element (FE) models well simulated the behavior of hybrid piers and indicated that structural details of steel cap beams, such as stiffeners and discontinuity conditions, affected the ultimate bearing capacity. FE analysis further assessed the influence of construction sequences. Combining an innovative construction method of hinged to rigid with the flange-rebar-UHPC joint, optimized the tensile stress of concrete columns by 49%, mitigating concrete cracking issues. The new hybrid piers demonstrated safety factors greater than 2.4, and have been successfully applied in the background project.

Graphical abstract

Keywords

urban viaduct / hybrid pier / steel-concrete connection / hinged to rigid construction method / large-scale tests / finite element analysis

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