Abstract: In order to study the difference of bearing capacity between polypropylene fiber reinforced engineered cementitious composite (PP-ECC) bridge pier and ordinary concrete bridge pier under compressive-bending load, the flexural performance of six PP-ECC bridge piers and two ordinary concrete bridge piers were studied by quasi-static test. Combined with the failure process of PP-ECC bridge pier, the characteristic points of compressive-bending failure of PP-ECC bridge pier were determined. Then, based on the simplified constitutive model of PP-ECC material, the theoretical cracking, yield and ultimate load formulas of PP-ECC bridge pier were derived. The characteristic parameters of the simplified PP-ECC constitutive model were determined by uniaxial tensile and uniaxial compression tests of PP-ECC materials. The calculation results were verified by the experimental results, and the differences of flexural bearing capacity and maximum deformation of piers under different axial compression ratios and PP-ECC zone heights were compared. The results show that after PP-ECC bridge pier is cracked, PP-ECC in the tensile zone still work, and cooperates with the tensile steel bar to participate in the section force. When PP-ECC bridge pier reaches the ultimate load, the crack develops steadily, and there is no large area of concrete spalling in the protective layer of ordinary concrete pier. The maximum deformation of PP-ECC bridge piers under ultimate load are larger than that of ordinary concrete piers, and the increase of axial compression ratio will reduce the deformation capacity of piers. Increasing the height of PP-ECC zone at a higher axial compression ratio, the flexural capacity of the pier increases by 8.8%. When using the simplified constitutive model to calculate the flexural bearing capacity of PP-ECC bridge pier feature points, the calculation accuracy reaches 0.86~1.13, and the variance analysis value is small, which has good calculation accuracy.

Key words: polypropylene fiber reinforced engineered cementitious composite (PP-ECC), PP-ECC bridge pier, flexural performance, simplify constitutive model, low-cycle repeated horizontal load