This paper investigates the crack and mechanical behavior of CFRP plate-reinforced bridge roof under high temperature with different anchoring measures. Six CFRP-reinforced test beams with different anchoring schemes were designed and constructed. The beam specimens, after the high temperature effects, were tested under four-point bending loads. The crack propagation, beam deflection, mid-span strain and the damage modes were observed and recorded until failure. The stiffness variation and the debonding failure mechanism of the test beams were comparatively investigated. The results indicate that the debonding bearing capacity of the specimens can be improved by the additional anchoring measures. The concrete shrinkage at the crack and the average crack spacing are more effectively reduced, when the additional anchoring measures are placed at the mid-span and the support position. In addition, a theoretical model is proposed for calculating the intermediate crack debonding bearing capacity. Based on the comparative analysis of various models and test results, it is shown that the proposed model could accurately calculate the intermediate crack debonding bearing capacity of the test specimens.

Numerical investigation of mechanical behavior of carbon fiber-reinforced polymer- (CFRP-) reinforced concrete beam after high-temperature action of asphalt paving construction was carried out in this study. The debonding failure of the CFRP plate-concrete interface was simulated by introducing the double debonding criterion. In order to compare with simulation results, specimens with different pavement schemes were tested to obtain experimental data. The load-deflection relationship, CFRP strain distribution, and crack propagation of specimens were compared with the numerical simulation results. The numerical simulation results showed good agreement with the experimental results. Additionally, the interface bonding stress distribution model and the calculation formula of the debonding bearing capacity were proposed. The proposed calculation model was proved to have good accuracy in predicting the strain of intermediate cracking debonding and the debonding bearing capacity of the CFRP-reinforced concrete beam after high-temperature action.

This paper investigates the flexural behavior of CFRP plate-strengthened concrete structures. Specimens of the CFRP plate-reinforced beam were designed and tested by the four-point flexural test. The load-deflection relationship, failure modes, and crack propagation were analyzed. The results showed that the postcracking stiffness and bearing capacity of the test beams can be improved by the additional anchoring measures for CFRP strengthening. The relationship between flexural moment and curvature was analyzed by introducing a MATLAB program. The calculation model between curvature, flexural moment, and stiffness was derived for the CFRP plate-strengthened structure. The recommended calculation model was applied in the analysis of deflection, and the theoretical values were compared with the test results.

This paper investigated the fatigue properties and theoretical research on Carbon-Fiber-Reinforced Polymer (CFRP) RC bridge roof with new deck-pavement material. Two deck pavement schemes of CFRP-reinforced specimens were designed and tested. Four-point flexural fatigue tests were carried out on the specimens. The fatigue crack propagation, the deflection development and the CFRP strain under bridge fatigue load were researched. The test results show that the CFRP plate-reinforced specimens crack resistance performance can be improved and can bear the fatigue test load of two million times. Combined with the characteristics of the crack growth rate and fatigue damage accumulation of CFRP plate-reinforced bridge roof specimens, the fatigue life prediction analytical model for CFRP plate reinforced RC bridge roof was obtained. The fatigue life prediction model agrees well with the experimental results. The model proposed in this paper could be applied to predict the fatigue life of the CFRP plate-reinforced RC bridge roofs.

Natural environment has a great impact on the performance of bridge structures, such as the ambient temperature, solar radiation, climate extremes and so on. Due to the lack of regional pertinence in the provisions of the existing specifications on the temperature load standard, and the lack of verification of its adaptability of hollow slab beam bridge in the reconstruction and expansion project, it is necessary to study the temperature load of the beam based on the temperature data of the area where the bridge site is located. Based on the measured meteorological data, the cross-section temperature distribution characteristics of the hollow slab beam and the temperature load effect were investigated. The vertical temperature load model of the short and medium-span hollow slab beam was proposed according to the simplified temperature curve. Firstly, based on the annual measured meteorological data, the plane model was established to analyze the temperature distribution characteristics of the hollow slab beam. Secondly, according to the temperature field distribution of the beam cross-section, the solid model of 16 m hollow slab beam was established to analyze the distribution of the temperature load effect. Finally, based on the preliminarily proposed temperature curve, vertical temperature load models were proposed by introducing the theory of extreme value extrapolation. The studies have shown that the temperature of the hollow slab beam is approximately horizontal distributed, and temperature extreme value appear at the location of the beam web. The roof and floor of the hollow slab beam are compressed and the webs are tensioned in the positive temperature difference state, the stress condition is opposite under the negative temperature difference state. The positive and negative temperature load models can meet the extrapolation requirements of the bridge design reference period. This study innovatively proposed a temperature load model based on the temperature curve corresponding to the most unfavorable effect of the beam. The extrapolation idea in the derivation of vehicle load model is introduced as well. And a temperature load model suitable for the extension of hollow slab bridges in Guangdong is established in this study.

The interfacial stress in a carbon fiber-reinforced polymer (CFRP) plate for strengthening the top flange of a box-girder bridge was theoretically investigated. According to the force analysis results of the box-girder structure, the most unfavorable force area was selected for modeling analysis. Using the simplified beam model, a CFRP plate-concrete interfacial-stress calculation model was derived, and the closed-form solution of the calculation model was obtained. Equivalent simplified test specimens were designed according to the box-girder structure to verify the reliability of the theoretical model. Then, four-point bending tests of the sample were performed. In these tests, the debonding failure modes and strain in the CFRP plate were examined. The CFRP plate-concrete interfacial stress was calculated according to the strain data of the CFRP plate in the experimental tests. Then compared the experimental results with the theoretical results. Furthermore, the corresponding interfacial stresses were calculated and compared according to the different load levels specified in the code. A series of theoretical and experimental comparisons were performed to verify the reliability of the proposed CFRP-concrete interfacial stress closed-form solution model.

For the purpose of splicing widening bridges without interrupting traffic in expressway reconstruction and extension projects, different types of anti-differential disturbance concrete (ADC) were developed. This paper experimentally investigated the mechanical performance of ADC under the influence of traffic–vehicle coupling vibration. The experimental device, with one end fixed and the other end vertically vibrated, was designed to simulate vehicle–bridge coupling vibration on an existing old bridge. Different disturbance degrees were simulated by adopting specimens made with standard molds and integral plate molds. The compressive strength and other performances of normal-type ADC (NADC) and high-performance ADC (HPADC) were tested. Owing to the differential disturbance, the compressive strength of the NADC increased by 10~20%, and that of the HPADC was almost unaffected. The flexural tensile strengths of the NADC and the HPADC were decreased to some extent. NADC and HPADC can both meet the requirement of widening bridge splicing, and the anti-differential disturbance performance of HPADC is superior to that of NADC.

Without interrupting the traffic on the old bridge, the connection of the widening bridge will cause disturbance to the concrete in the splicing position. In order to study the anti-disturbance performance of concrete material, the Normal Concrete (NC) material and the Ultra-High-Performance Concrete (UHPC) material were experimentally investigated by the vertical shaking table and X-ray computed tomography scanning. It can be learnt from tests that the compressive strength of NC and UHPC can be increased by about 10% to 20% after disturbance, while the flexural tensile strength and splitting tensile strength of both NC and UHPC can be reduced by about 20% to 25% and 10% to 20%, respectively. The elastic modulus of UHPC is not significantly affected by the vibration disturbance, and that of NC can be increased by about 20%. The setting time difference of the proposed NC material can be controlled within 100 min, and it can improve its anti-disturbance performance. Excessive vibration disturbance affects the internal structure of NC, while it has little effect on the distribution of steel fiber in UHPC. Due to the high cost of UHPC materials, it is recommended to analyze the joint performance requirements before the selection of splicing materials. If the stress requirement is not particularly high, it is still recommended to apply the proposed NC material for the splicing of widening bridge.