Deficiency of the concrete strength in some regions of reinforced concrete (RC) columns in practice may weaken the seismic behaviors of columns. Its effects on RC columns should be well understood. This paper aims to investigate the influences of deteriorated segment on the seismic behaviors of partially deteriorated RC columns and attempts to recover the seismic behaviors of partially deteriorated columns with Carbon Fiber Reinforced Polymer (CFRP) composites. A finite element analysis was carried out to simulate the seismic behaviors of CFRP-confined partially deteriorated RC columns. The numerical results were verified by the laboratory tests of six specimens. Based on the finite element results, the failure location of partially deteriorated columns in an earthquake was predicted, and the effectiveness of CFRP retrofitted on partially deteriorated columns was evaluated.
Super-span, reinforced concrete, T-shaped cross-section beams (T-beams) with a service life of more than 30 years are widely used in highway bridges in China. Most of these beams have been retrofitted with glass fiber-reinforced plastic (GFRP) to prevent performance degradation. However, the actual shear performance, ultimate state, and failure mechanism of the existing retrofitted super-span concrete T-beams are currently unclear for many inextricable problems. To fill these gaps, in this study, one super-span concrete T-beam, in service for 31 years and retrofitted with GFRP, was extracted from a highway bridge to conduct shear experimentation in a structural laboratory. To assess the particularity of the specimen, finite element analysis was also conducted using ABAQUS software as a supplement to the shear tests. The failure procedure of the specimen was investigated, and the influence of the loading mode on the shear performance of a super-long and old T-beam was also studied. It is concluded that the failure of the super-span T-beam begins with small cracks at the bottom of the mid-span, rather than a loading point.
Super-span (20 m) non-prestressed T-section reinforced concrete beams have been in service for more than 30 years and are common in Chinese highway bridges. However, the actual performance of these super-span T-section reinforced concrete (RC) beams that have been reinforced with FRP, including their process of failure from a service state to a failure state, has not been determined. In this study, original RC T-beams, with a 20 m span and retrofitted with FRP, were taken from a highway bridge. Their flexural performance was detected via experiments in a laboratory. The experiments revealed that the sectional strain distribution is more non-uniform. The mid-span ribs clearly play a role in strengthening the section and the bearing reservation was studied based on a subsequent sectional analysis. It became clear that the load-bearing reservation of an old super-span T-beam changes during the entire life of the specimen; not only because of the depression of the resistant capacity and the reinforced measure, but also due to the updates to load codes.
Abstract-Due to frost damage or insufficient vibration during construction, partial deterioration of reinforced concrete (RC) columns commonly exist in practical engineering, which would weaken the seismic behaviors of the structure. The work of strength is needed for the RC columns with deterioration. Thus, in this paper, the seismic behavior of CFRP retrofitted reinforced concrete column with partial deterioration was investigated by numerical and experimental approaches. Firstly, a numerical model was proposed to analyze seismic behavior of partially deteriorated RC columns and CFRP retrofitting columns. Then, the experiment with six specimens was carried out to validate the numerical results. It is found that the proposed numerical model can be used to analysis the seismic behaviors of CFRP retrofitted reinforced concrete column with partial deterioration.
To investigate the changes in soil dynamic response around the tunnel periphery under the vibration loads generated by train operation on curved sections, field measurements were carried out to observe void water pressure, water level, and settlement on the ground. Additionally, simulation modeling using MIDAS was employed to simulate and analyze the soil’s dynamic response under the impact of train loads. Based on the track stress diagram combined with the axle weight of the train, the transverse and vertical loads of the track are calculated. The corresponding parameters are entered into the train dynamic load table in the MIDAS/GTS NX dynamic analysis module, so as to simulate the vibration loads of the tunnel. The results show that the application of vibration load is an important reason for the change in pore water pressure during train operation. During the initial stages of train operation, the pore water pressure exhibits a significant increase, followed by a gradual decrease over time. The overall variation follows a seasonal pattern, with the pore pressure increasing as the depth of burial increases. The response of the soil around the tunnel to the vibration of the train is closely related to the location. The closer to the tunnel, the more sensitive the soil is to the vibration of the train, and the greater the amplitude and rate of pore pressure change and vertical deformation in the soil. The variation trend of groundwater level in soil is basically consistent with that of pore pressure, and the groundwater level is proportional to the depth. The dynamic response of the soil at the bottom of the curved tunnel decreases with the increase in the turning radius. The main influence range of the dynamic response is 0~15 m at the bottom of the tunnel. The excess pore water pressure generated by the soil gradually dissipates, and it can be predicted that the vibration of the train will not cause deformation damage to the surrounding soil.
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