Applied Mechanics and Materials Vols. 256-259

Abstract: This paper presents the experimental results of the wood columns externally strengthened with fiber reinforced polymer (FRP) subjected to axial compressive loading. In total, 14 square short wood columns were made, which were reinforced by FRP in two reinforcing arrangements. The main parameters studied in the test were (1) the strengthening materials, i.e. carbon FRP (CFRP), basalt FRP (BFRP) and aramid FRP (AFRP); (2) the reinforcing arrangements, i.e. the full wrapping of FRP and the partial reinforcing arrangement; (3) the layers of FRP sheets applied, i.e. one, two and three. The ultimate strength, load-axial displacements curves, load-strain relationships, and the failure modes of all the columns were presented. The test results show that both types of the reinforcing arrangements could increase the ultimate strength and stiffness of the columns tested greatly. The columns strengthened with two layers of FRP sheets gave higher load carrying capacities when compared to the columns strengthened with one or three layers of FRP sheets. The result confirms that the more layers of FRP sheets, the higher of load carrying capacity; however, the adverse results were shown when three layers of FRP sheets applied. Finally, the result also showed that the full wrapping reinforcing arrangement is more effective than the partial one in enhancing the stiffness.

Abstract: In order to investigate the strengthen effect of different embedment lengths of the NSM strip on different damage levels. A series of tests were conducted on damaged reinforced concrete (RC) beams in flexure strengthened with near surface mounted (NSM) carbon- fiber-reinforced polymer (CFRP) strips, and initial cracking load, ultimate capacity, loading-deflection curves, and failure modes are examined and analyzed in the paper. The results showed that not only the initial cracking loads and ultimate capacities of the beams are significantly increased，but also the flexural stiffness of the beams in the yield and ultimate behavior stages are improved by using NSM-CFRP strips. The strengthen effect on lower damage level RC beams has no obvious difference with that on non-damaged RC beams. Anchoring of the strip end can increase the ultimate load capacities and decrease the ductility of RC beams. Debonding was found to be the primary failure mode in all cases.

Abstract: There is a high-rise building whose main structure is framework - core tube. In order to meet the requirements for architectural features, the distance between the outer frame and the exterior wall of core tube is relatively small, therefore the floor structure program adopts a thick plate and wide flat beam floor system, and part floors of the upper structure adopt a thick plate and dark beam system. As wide flat beams (dark beams) have a small height and cannot form effective support for the floor, special analysis has been made on floors from the security point of view without considering the role of wide flat beams (dark beams). The floor system of this high-rise building has been analyzed and discussed with regard to bearing capacity, deformation, comfort and other aspects.

Abstract: Trend prediction is virtually modeling process for dynamic data. The key to prediction is to establish a model in accordance with actual status, then use the model to predict the trend of object, and infer its behavior in future. Two prediction methods are researched to predict the trend on the observed points of the structure in this paper, which are regression prediction method and grey prediction method. The continuous time strain value of a measured point on Tianxingzhou Yangtze River Bridge is used as data sample for researching. The method of regression analysis is applied for predicting the trend of short-term data, and the method of grey model prediction for predicting long-term data. Regression prediction can assess the health status of the structure and obtain the alarm information effectively by comparing the actual monitoring data with the range of forecast interval. Grey prediction method has great advantages when dealing with poor information. By engineering example this study shows the pros and cons of these two methods, and proves that the method of grey model prediction is more suitable of predicting the trend of object in the structural health monitoring system.

Abstract: The objective of this study is to calculate, design and evaluate support structure safety of regional wind system engineering. First of all, wind loading was calculated based on the building structure norm. Secondly, support structures of regional wind system engineering were designed using CAD. Finally, structure safety of regional wind system engineering was analyzed with finite element ANSYS software. The results showed that the wind system engineering structure is away from harmful fluctuating. Wind load cycle does not match resonance phenomenon. Under fluctuating wind loads, the engineering windbreak structure displacement and stress were dynamic amplification effect. It was concluded that this method can keep safety in support structure design of regional wind system engineering.

Abstract: The calculation for flexural capacity of beam end and column end were carried out, with the strength effect of slab bar being included. The results for traditional joint specified in design code and that for the joint retrofitted with hybridized CFRP were compared. The results presented the efficiency of flexural strength improvement in beam. It is also shown that for the joint retrofitted with hybridized CFRP, the stress in the reinforce bar for column will increase significantly, while the plastic pivot of column appears later, which tend to exhibit a failure type closer to the beam-pivot or ductile mode.

Abstract: This article introduces a novel buckling restrained brace (BRB) whose core members are restrained by transverse restraints which consists of two lines of parallel square tubes at both sides of the core member. Three different types of BRB are cyclically loaded in the investigation, using different restraining mode and steel types for the core members. Results of the experiment indicate that the transverse rib restraining mode is able to achieve expected effects. BRB specimens with LYP160 core member exhibit relatively better hysteresis performance than specimens with Q235 core member.

Abstract: Taking 1 year return period wave data statistics of Cheng Dao sea area as an example, the wave-current flow hydrodynamic load acting on submarine flexible pipe was analyzed. According to the actual structure of submarine flexible pipe, ANSYS numerical model was established. Under the combined effect of internal operating pressure and transverse wave-current flow hydrodynamic load, the results calculated by numerical model shows that with the increase of transverse load, the bending deformation of flexible pipe increases linearly, and the stress of flexible pipe is almost constant.

Abstract: Soil suction is one of the most important parameters for unsaturated soils. An experimental program was carried out to measure the maric suction of soil specimens of a residual soil in Xiamen by filter paper method. Initial water content, soil structure, and stress state were taken into account to investigate the hysteresis loop of SWCC. The air-entry value of test soil is about 140kPa and residual saturation is about 18%. The soil specimen at wet of optimum has the largest hysteresis loop for a relatively uniform pore-size distribution. However, the soil specimen at dry of optimum has the smallest hysteresis loop. The soil specimen at optimum lies between them. For specimens subjected to different stress states under various applied loads, the higher the applied load on the specimen, the smaller the size of hysteresis loop. In drying or wetting process, there is a significant difference in matric suction though soil specimens are at same water content. Therefore, for this kind of soil, it should be attention that the shear strength may be greatly reduced during rainstorms.

Abstract: High speed camera system is used to record crack propagation on rock surface during the lab rocburst experiment. This paper presents the specific analytical method of crack propagation with high speed images. Crack propagation types and directions are briefly described, and the lengths, growth rate and fractal dimension of cracks are calculated. The results show that the crack grows mainly along the horizontal line on the unloading surface, at a low speed before rockburst and reaches a very high speed abruptly near the burst point. The fractal dimensions demonstrated that the crack turns to be rough when rockburst happens. The study on the crack propagation is benefit to the understanding on the mechanism of rockburst.