The flexural pile foundation is used in integral abutment jointless bridges (IAJBs) in practical engineering to effectively dissipate the horizontal reciprocating deformation induced by the ambient temperature or earthquake loadings. Various types of flexural piles including the H-shaped steel pile (HP), prestressed concrete pile (PC), prestressed high-strength concrete pile (PHC) as well as the reinforcement concrete pile (RC) have been implemented in IAJBs. However, there is a lack of comprehensive studies on the flexural deformation and seismic performances of these piles. In order to investigate and compare their mechanical behaviors and seismic performances, a low-cycle pseudo-static test on several different types of piles was carried out. The test results indicated that the plastic hinge location of piles moved to a deeper pile depth with the increase of reinforcement ratio, buried pile depth and prestressing level, which led to better pile–soil interaction. The crack resistance of a concrete pile was improved as the reinforcement ratio and prestressing level increased. Moreover, the rectangular pile had a better soil–pile interaction and energy dissipation capacity than the circular pile. The inflection point of the pile deformation shifted deeper as reinforcement ratio, buried pile depth and prestressing level increased, which improved the effective length and horizontal deformation capacity of piles. The H-shaped steel pile showed a better elastic-plastic deformation capacity, ductility and energy dissipation capacity as compared to the concrete pile. Moreover, the pile having a higher bearing ratio sustained larger lateral loads whereas the surrounding soil was subjected to higher loads. Finally, new seismic design criteria of three-stage seismic fortification and five damage level for the concrete piles of IAJBs were proposed.

A reciprocating low-cycle pseudostatic loading test on four prestress high-strength concrete (PHC) pipe piles was performed to study their failure modes and seismic behaviors. The distributions of lateral deformation and soil pressure along the piles as well as their analysis methods were studied. The test results show that with an increase in the embedded depth of pile, the soil pressure around the piles initially increased up to the maximum and then decreased or even reversed slightly at a certain depth. The pressure at shallower soil increased rapidly, up to nearly the ultimate passive earth pressure, while the pressure at the deeper soil increased relatively slowly. The results further indicate that the strain transformation method and m method were only appropriate for calculating the lateral displacements of piles under linear and small deformation but not suitable to calculate lateral displacement of piles under large deformation. Moreover, although the p–y curve method took into account the nonlinearity of soil, the calculated lateral displacement and soil pressure of pile still showed a significant difference with the test results, especially under large deformation. Furthermore, modified calculations of lateral displacement and soil pressure of pile were proposed based on regression analysis on the test results and existing p–y curve methods, respectively, and calculated results showed a good agreement with the test results in terms of lateral displacements and soil pressures. Therefore, they were recommended for analyzing the soil–pile interaction for pile foundations in integral abutments jointless bridges (IAJBs).

Thousands of multi-span, simply supported beam bridges with short or medium spans have been built in China. They often suffer from problems of cracks in the link slabs over piers, and the deterioration and damage of deck expansion joints at abutments. To address these problems, one approach is to retrofit them by converting the simply supported box beams into continuous structures over the piers and jointless bridges over the abutments. This paper discusses the design methodology and details for retrofitting the Jinpu Bridge in Zhangzhou, Fujian, China, from a simply supported bridge into a semi-integral bridge, in which semi-fixed dowel joints are used to connect the superstructure and the substructure, including piers and abutments. Simultaneously, the finite element software is used to calculate the internal forces and displacements of the structure. The analysis reveals an 11.1% reduction in the maximum positive moment at the midspan of the main beam in the semi-integral bridge compared to the simply supported bridge. However, the shear forces at the interior pier increase by 6.4%. According to the response spectrum analysis, the maximum longitudinal displacement of the semi-integral bridge’s main beam is 11.6 mm, reduced by 80.1% compared to the simply supported bridge under a dead load and earthquake effects. The maximum bending moment and shear force on the pier of the semi-integral bridge are 984.7 kN·m and 312.6 kN, respectively, both below their ultimate bearing capacities. The maximum displacement at the top of the pier is 7.7 mm, which is below the allowable 52.4 mm displacement. The calculated results conform to the design requirements specified by the code.

The semi-fixed dowel joint studied in this paper consists of a steel dowel with rubber sleeves and a rubber pad to connect the superstructure and the substructure and to support the main beam. This type of joint is suitably used in retrofitting a jointed bridge with high-stiffness substructure into a semi-integral bridge. This study aimed to investigate the nonlinear stiffness of the joint, which is the key parameter in the retrofitting design. Taking the real joint in a retrofitted semi-integral bridge as a prototype, tests on full-scale models were carried out, in which the wall thickness of the rubber sleeve and the thickness of the rubber pad were taken as parameters. The test results show that the wall thickness of the rubber sleeve is the main factor affecting the radial stiffness and the flexural stiffness of the semi-fixed dowel joint. With the decrease of the wall thickness of the rubber sleeve, the radial stiffness decreases while the flexural stiffness increases. However, the thickness of the rubber pad has little influence on both the radial and flexural stiffness of the joint, and its main role is only vertical loading-bearing. If the longitudinal deformation of the main beam of a bridge under maximum temperature variation is 10 mm as the allowance value of engineering design, the wall thickness of the rubber sleeve for this joint should not be less than 40 mm. At last, on the basis of experimental research and theoretical analysis, the formulas of radial stiffness and flexural stiffness are fitted; it can be used as reference for practical engineering application, or for formulation of relevant specifications.

Thousands of multi-span, simply supported, beam bridges with short or medium spans have been built in China. They often suffer from problems of cracks in the link slabs over piers, and deterioration and damage of deck expansion joints at abutments. To address these problems, one approach is to retrofit them by converting the simply supported box beams into continuous structures over the piers and jointless bridges over the abutments. This paper discusses the design methodology and details for retrofitting the Jinpu Bridge in Zhangzhou, Fujian, China, from a simply supported bridge into a semi-integral bridge, in which semi-fixed dowel joints are used to connect the superstructure and the substructure, including piers and abutments. Simultaneously, the finite element software is used to calculate the internal forces and displacements of the structure. The analysis reveals an 11.1% reduction in the maximum positive moment at the midspan of the main beam in the semi-integral bridge compared to the simply supported bridge. However, the shear forces at the interior pier increase by 6.4%. According to the response spectrum analysis, the maximum longitudinal displacement of the semi-integral bridge's main beam is 11.6 mm, reduced by 80.1% compared to the simply supported bridge under dead load and earthquake effects. The maximum bending moment and shear force on the pier of the semi-integral bridge are 984.7 kN·m and 312.6kN, respectively, both below their ultimate bearing capacities. The maximum displacement at the top of the pier is 7.7 mm, below the allowable 52.4 mm displacement. The calculated results conform to the design requirements specified by the code.

Leaning-type arch bridges are attractive for wide-deck urban applications, but their elastic global buckling mechanisms and parameter sensitivities remain insufficiently quantified. This study investigates a leaning-type steel box arch bridge using a three-dimensional finite element model validated against field-measured arch deflections and hanger forces. Linear elastic eigenvalue buckling analyses examine the structural system, rise-to-span ratio, arch stiffness, leaning-arch inclining angle, and transverse-bracing characteristics, together with the coupled effect of rise-to-span ratio and main-arch stiffness. Within the investigated bridge configuration, the integrated leaning-arch–transverse-bracing system increases the stability coefficient by approximately 71% relative to the unbraced main-arch system. A relatively favorable main-arch rise-to-span ratio of approximately 1/7–1/4.5 is identified. Main-arch bending stiffness has a pronounced influence, and its quantitative effect depends on the rise-to-span ratio. Variations in leaning-arch inclining angle produce relatively limited net changes, while further increases in bracing stiffness yield diminishing improvements. For a fixed bracing quantity, balanced spatial distribution over the arch span is more effective than concentrating bracings within a limited region. These findings provide a quantitative basis for comparative stability assessment and preliminary design of similar bridge systems.