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On the basis of the existing test data of high temperature mechanical properties of 1860 grade steel strands, a regression model of high temperature performance of steel strands that can be used for theoretical analysis and numerical calculation is obtained. Based on the non-stationary temperature field model in the fire of tall and large space buildings, the non-linear finite element numerical analysis method considering the time integral effect is used to establish the fire resistance numerical model of the large-span prestressed steel structure. Through the fire-resistance calculation example of Beam String Structure, the influence of different fire source positions on the fire-resistance of prestressed steel structures is discussed.

Order to investigate the failure effect of textile reinforced concrete (TRC) plate under bending load, the corresponding finite element model is established. By comparing the numerical simulation results with the experimental results, the rationality and feasibility of the finite element model are verified, and then the crack extension of TRC and the ultimate strain of carbon textile are analyzed. The failure mode of the slab under bending load is obtained, and it is found that the carbon textile concrete slab has better reinforcement effect, which greatly improves the safety performance of concrete members.

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. THE CRACK HEIGHT OF THE REINFORCED SPECIMEN INCREASES AS THE FATIGUE LOAD VALUE INCREASES. THE CRACK HEIGHT OF THE REINFORCED SPECIMEN CAN BE MAINTAINED AT A CONSTANT VALUE IN THE FINAL STAGE OF FATIGUE FAILURE. IN ADDITION, THE BEARING CAPACITY AND FATIGUE LIFE OF CFRP-REINFORCED SPECIMENS WERE IMPROVED. 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.

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.

The bond-slip relationship of Carbon Fiber Reinforced Polymer (CFRP) plate-concrete after the influence of high temperature action of Stone Mastic Asphalt (SMA) paving was investigated in this article. Two groups of double shear specimens with different bonding length were designed and tested. Based on the test results, the failure modes of specimens, the strain distribution and the shear stress of CFRP-concrete interface were analyzed. Considering the influence of high temperature, the interfacial bond-slip constitutive model of CFRP plate and concrete after high temperature action of SMA paving construction was proposed. The proposed model can reflect the nonlinearity and interface softening behaviour of the CFRP plate-concrete interface constitutive relationship under special environment. Through the comparative study of exixting constitutive models, the interface bond-slip constitutive model proposed in this paper considers the effect of high temperature and has good agreement with the test results.

As a common prestressed member, the steel strand has a wide range of applications. Its bearing capacity affects the safety of the whole structure. Once it is damaged, the whole structure will be damaged or even collapsed. As a single tension bearing member, the transverse behavior of steel strand is often ignored. However, in recent years, the impact fracture accidents of steel strand occur frequently, and the research on transverse impact resistance of steel strand is very important. At present, there is no reliable evaluation standard for the mechanical properties of steel strand subjected to impact. The strand is made of several independent wires. Under the action of external load, the stress of each strand is different, and the stress distribution inside the strand is more complex. Under the action of transverse impact, the fracture position and quantity of strands are different, and the failure modes caused by different impact conditions are also different. In order to understand the mechanical performance of steel strand under transverse impact and provide evaluation basis to improve the structural safety, this paper carried out relevant research through test and finite element simulation method.

In view of the high cost and self-importance of traditional explosion-proof walls, a fiber composite material cavity protective board made of UHMWPE as a matrix is proposed to protect the walls of general civil buildings to achieve rapid enhancement in response to sudden terrorist attacks. Based on LS-DYNA finite element analysis, the response of the protective board and wall under the impact of the explosion is analyzed. By setting different key parameters such as equivalent weight, burst distance, presence or absence of protective structure, the damage to the wall, the protective effect of the protective board and its own performance characteristics are discussed. The results show that the externally arranged composite material protection board can effectively attenuate and absorb the overpressure and energy generated by the explosion shock wave, and significantly reduce the displacement and deformation of the wall, and it also has excellent performance in its own energy absorption and deformation resistance. But there is a certain safety protection distance under different equivalents.

Concrete structures are easy to produce cracks which seriously affect the safety of the structures. Rayleigh based distributed optical fiber sensing technique has been used to measure the strain field evolution associated with crack initiation and growth in concrete structures. A reinforced concrete beam has been tested under four-point loading test with optical fibers both pasted on the surface and embedded as the distributed sensors. Experimental results indicate that cracks can be detected at sharp peaks of the measured strain distributions, which can be utilized to effectively capture the number of cracks and locate multiple cracks. The abilities of using optical frequency domain reflectometry (OFDR) technology to detect hairline cracks and distinguish neighboring cracks are also discussed. Single crack opening displacement is determined through fitting process which taken the influence of intermediate layers into consideration, the widening and propagation of cracks in the overall concrete beam were detected.

The abrupt fracture of prestressed steel strand will form a great unloading impact force, which will influence the displacement and internal force of the remaining structure. Shock response spectrum method can reduce the computation and ensure the accuracy. In order to obtain the shock response spectrum of the steel strand at the moment of failure, this paper proposes to solve the dynamic response of a single degree of freedom structure after cable break through programming under the premise of knowing the failure time of the strand and the corresponding cable tensioning. We select several unloading curves that are the closest to the test, and solve the response spectrum of the broken cable under different failure time and damping, finally, the response spectrum method is compared with the finite element method by numerical simulation. It can be found that the dynamic coefficient will show different trends due to the change of unloading methods. In the same unloading method, the failure time has little impact on the shock response spectrum, but the impact of damping on the shock response spectrum is very obvious.