Mechanistic understanding of precast UHPC segmental beams with external tendons and epoxy joints subject to combined bending and shear

Research on numerical model for flexural behaviors analysis of precast concrete segmental box girders

A model considering slip and shear-lag for the dynamic analysis of a coupled steel-concrete composite bridge-train system is proposed in this paper, based on the finite element method and Euler-Bernoulli theory. The stiffness matrix, damping matrix, mass matrix, wheel-rail contact force matrix and the equations of motion of the coupled system considering slip and shear-lag are derived based on energy theory. In addition, a solver for dynamic analysis of the coupled system considering slip and shear-lag is compiled by using the Newmark-β method. To verify the rationality of the dynamic analysis model, field-test data for this type of coupled system from literature is compared with the data calculated by the improved model, and good agreement is found. The influence of slip and shear-lag on the dynamic response of the coupled system is studied in detail through a case study. The analysis proves that these factors (slip and shear-lag) substantially affect the dynamic response of the coupled system. This model proposed in this paper provides an efficient tool to analyze of the influence of slip and shear-lag on the dynamic response of coupled steel-concrete composite bridge-train systems.

Dynamic analysis of a coupled steel-concrete composite box girder bridge-train system considering slip and shear-lag

Experimental study on prefabricated composite box girder bridge with corrugated steel webs

Concrete-filled steel tubes (CFST) are economical for arch bridges because of their high compressive strength and efficiency in construction. Compared to the traditional concrete arches, the CFST arches usually have a large slenderness ratio, which makes the arches more prone to buckling. Despite this, limited experimental investigations have been performed on the buckling behaviour of CFST arches. In this study, a buckling test was performed on two 9 m long CFST parabolic fixed arches having a single circular cross-section with one arch subjected to a central concentrated tilting load and the other to half-span three-point tilting loads. Finite element (FE) models using solid elements were built and validated against the test results, with which the influences of the residual stress on the buckling behaviour of the composite arches were analysed and the confining pressure distribution was obtained. The FE models using beam elements were then built to investigate the confinement effects on the buckling behaviour of the CFST arches. Relatively significant confinement effects were found on the arches and were considered in the FE modelling. The residual stress had a fairly limited influence on the load-carrying capacity of the arches and was ignored in the FE models. Both the built FE models using solid and beam elements performed well in predicting the buckling behaviour of the CFST arches. • Buckling test on 9 m long slender CFST arches subjected to tilting loads. • Significant confinement effects on buckling behaviour of CFST arches. • Influence of residual stress on the buckling behaviour of CFST arches. 

Experimental and numerical study on slender concrete-filled steel tubular arches subjected to tilting loads

Concrete-filled steel tubular arch (CFSTA) bridges have been widely used in the past few decades. As the service time of the arch rib increases, the mechanical performance degrades due to the time-deterioration properties of infilled concrete. In order to study the influence of the long-term effects on the ultimate bearing capacity of arch ribs, four CFSTAs totally with two different fly ash replacement ratios were designed and tested to failure after a one-year sustained loading test. Test results showed that the in-plane bearing capacity of the post-creep CFSTAs was obviously reduced compared to that without long-term loading cases. A stepwise approach for considering the long-term behaviour of concrete was elaborated on and numerically implemented in ABAQUS, and the proposed finite element (FE) model was verified against the results yielded from the experiment. The study found that the age-adjusted effective modulus method may not accurately capture the in-plane behaviour of the post-creep coupons. FE results showed that the influence level of long-term effects on the capacity was negatively correlated with the stiffness of the arch rib. For CFSTA bridges within engineering applications, the capacity reduction caused by shrinkage and creep effects can be more than 10% after ten years.

Experimental and numerical study on the in-plane behaviour of concrete-filled steel tubular arches with long-term effects

This paper proposes a one-dimensional fiber beam element model taking account of materially non-linear behavior, benefiting the highly efficient elastic-plastic analysis of girders with shear-lag effects. Based on the displacement-based fiber beam-column element, two additional degrees of freedom (DOFs) are added into the proposed model to consider the shear-lag warping deformations of the slabs. The new finite element (FE) formulations of the tangent stiffness matrix and resisting force vector are deduced with the variational principle of the minimum potential energy. Then the proposed element is implemented in the OpenSees computational framework as a newly developed element, and the full Newton iteration method is adopted for an iterative solution. The typical materially non-linear behaviors, including the cracking and crushing of concrete, as well as the plasticity of the reinforcement and steel girder, are all considered in the model. The proposed model is applied to several test cases under elastic or plastic loading states and compared with the solutions of theoretical models, tests, and shell/solid refined FE models. The results of these comparisons indicate the accuracy and applicability of the proposed model for the analysis of both concrete box girders and steel-concrete composite girders, under either elastic or plastic states.

A fiber beam element model for elastic-plastic analysis of girders with shear lag effects

Stress is one of the most important physical indexes reflecting the mechanical behavior of concrete structures. In general, stress in structures cannot be directly monitored and can only be estimated through an established model of stress and strain. The accuracy of the estimated stress depends on the rationality of the established model for stress and strain. As the strain measured by sensors contains creep, shrinkage, and elastic strain, it is difficult to establish an analytical model for strain and stress. In this paper, a statistical inverse method was utilized to estimate the stress in continuously pre-stressed concrete beams based on the monitored strain. Stress in the beams and the model uncertainty factors were treated as model parameters. A linear-simplified method was adopted to determine the prior distribution of the stresses. The posterior distribution of the stresses at different locations during bridge construction can be obtained by the proposed method. A continuously pre-stressed concrete beam bridge was taken as the case study to verify the effectiveness of the proposed method. Additionally, the constitution of the total strain in the different construction stages was calculated. It was concluded that the creep strain is the dominant part of the total strain.

Wutong Yan

Papers

Research on numerical model for flexural behaviors analysis of precast concrete segmental box girders

Experimental and numerical study on the in-plane behaviour of concrete-filled steel tubular arches with long-term effects

A fiber beam element model for elastic-plastic analysis of girders with shear lag effects

Statistical Inversion Approach for Stress Estimation Based on Strain Monitoring in Continuously Pre-Stressed Concrete Beams