317 publications from this institution
CFRP cables are promising to be utilized in bridge engineering, but their effective anchorage remains a challenge for engineers. To solve this problem, novel self-anchored CFRP cables with different anchorage configurations were designed and tested, with main variables including the radius, thickness, and slope of the CFRP loop at the anchorages. The results indicate that the mechanical behavior of the self-anchored cables is mainly determined by the thickness and radius of the CFRP loop and by increasing these characteristics, the cable’s material strength can be fully exploited. With optimized anchorage configurations, the anchor efficiency of the proposed self-anchor CFRP cable system can reach 95% or larger. Additionally, finite element analysis was conducted, with good agreement between the numerical and experimental results. Finally, the influence of the radius and thickness of the CFRP loop on the anchoring capacity and the nominal anchor efficiency was further discussed based on an orthotropic thick-walled cylinder model.
Bolted connections are often used in pultruded glass fiber reinforced polymer (GFRP) structures. Blind bolts, which require installation from one side only, become convenient when access is limited to tighten the ordinary bolts, especially for tubular GFRP sections. This paper presents the results of a comparative study on pultruded GFRP double-lap joints using ordinary bolts and blind bolts. Static experiments were conducted on pultruded GFRP double-lap joints with two columns of bolts, whereas the number of rows varied by one, two, and three. The static behaviors of ordinary bolted and blind bolted joints were compared in terms of load-displacement response, failure modes, and failure load. Then, constant amplitude fatigue tests were carried out on the double-lap joints with two bolts in a row. The maximum fatigue load varied from 30 to 80% of the static failure load of the corresponding joint. The fatigue life of each specimen was recorded and S-N curve was obtained. It was found that the static failure loads of blind bolted joints were lower by a maximum of 21% than those of ordinary bolted joints, whereas the fatigue performance was not much affected by the type of the bolts.
The energy crisis and environmental pollution have promoted the rapid development of renewable solar technology. Building integrated photovoltaics (BIPV) is an important field for the future development of solar energy. This review presents the mechanical property studies of existing BIPV and analyzes its research status to offer advice for engineering applications. By analyzing the types and mechanical characteristics of solar cells in the existing BIPV and determining the load conditions that need to be considered in different application modes, this paper summarizes the relevant existing studies at the photovoltaic material, cell and component levels and offers corresponding suggestions for mechanical research, which consequently results in the proposal of a new BIPV structure. Since the mechanical properties of BIPV have seldom been studied, and research on practical engineering applications is lacking, further comprehensive and in-depth research is needed to promote the safe and reliable application and popularization of photovoltaic building integration.
This study presents an experimental study on the mode I fracture property of pultruded fiber reinforced polymer (FRP) composites along the fiber direction. A quasi-brittle fracture exists for this material. The bilinear softening model is used to describe the constitutive relation in the cohesive fracture zone. Furthermore, a double K fracture criterion is applied to analyze the crack propagation and fracture property. The orthotropic effect on the fracture property of mode I along the fiber direction is rather small and ignored in this study. According to the bilinear softening model, the cohesive fracture energy is divided into two parts, the microcracking fracture energy and the fiber bridging fracture energy. The ratio between the two fracture energies and the model parameters are decided with the test results. For the double K fracture criterion, a cohesive fracture toughness in introduced to calculated the initial cracking fracture toughness. Based on the linear elastic fracture mechanics and the bilinear softening relation, the two fracture toughness of this criterion are obtained with the test results.
<p>Carbon fiber reinforced polymer (CFRP) materials have the advantages of a high strength/weight ratio, corrosion resistance. Bridge construction with CFRP cable rather than steel cables has a wider span, better load capacity, and longer life span. Due to the anisotropy of the CFRP materials, achieving effective anchorage for CFRP cables is challenging. To address this problem, a self- anchored integrated CFRP cable has been proposed. Recently, the novel cable was adopted in a truss bridge in Shanghai. The utilization of the novel cable contributed to rapid construction and ensure structure safety, which is quite attractive for future bridge construction.</p>
Prefabricated concrete sandwich panels are crucial components in the construction of prefabricated buildings, providing essential functions such as load-bearing capacity, thermal insulation, and fire resistance. The development of sandwich panels is oriented toward achieving lightweight, high-strength structures with superior thermal insulation properties. This study introduces two types of innovative sandwich panels using TRM rib with FRP composite bolts and FRP pultruded profiles as connectors, respectively. Comprehensive experiments were conducted to evaluate their construction methods and flexural performance with different thicknesses (i.e., 100 mm and 150 mm). The test results indicate that the proposed sandwich panels can be fabricated in large dimensions of 4 m × 3 m and can withstand substantial equivalent wind loads. The different sandwich panels exhibited distinct failure modes and various composite actions of 8.04 %, 28.36 %, 49.56 %, and 85.67 %. Subsequently, this work presents a theoretical analysis model for predicting the initial stiffness, which has achieved favorable accuracy. Comparative analysis with other studies indicates that the sandwich panels investigated are classified as lightweight, high-strength and thin sandwich panels, which demonstrate significant potential for practical applications.
所谓多元化教学是相对于单一的教学模式而言的,是打造新时期高效课堂的重要因素。所以,在新课程改革下,语文教师要更新教育教学观念,要认真研究教材价值,优化教学过程,并将课堂的各个环节走向多元化,这样既可以调动学生的学习积极性,又可以激发学生的学习乐趣,进而为高效课堂的实现打下坚实的基础。
This paper proposes a novel strengthening method for reinforced concrete (RC) beams using prestressed carbon fibre-reinforced polymer (CFRP) plates. In the proposed method, the CFRP plate is stressed by adjusting the position of the mid-span deviators. The strengthening process is fast and easy to apply because there is no need for hydraulic jacks or adhesives. To investigate the behaviour of the strengthened RC beams, a series of tests were conducted on both intact and damaged beams with different strengthening configurations, and the full range behaviours of the beams are reported in detail. According to the test results, the maximum stress of the CFRP plate reached 1500 MPa, and the beam strength was enhanced up to 43%. Some of the strengthening schemes achieved good ductility. As a result, the proposed strengthening method is found to be effective and can be further developed into a pseudoplastic CFRP strengthening system.
FRP（纤维增强复合材料）近年来在混凝土结构加固中得到广泛的应用，并作为一种新型高性能结构材料受到结构工程界的广泛关注，国内外有关研究和工程单位开展了大量的研究和实践应用，该文介绍了结构工程中常用的FRP材料性能和形式，分析了其优点与不足，并介绍了FRP加固结构、FRP配筋和预应力FRP筋混凝土结构、FRP结构与FRP组合结构以及FRP在桥梁结构、大跨空间结构和智能结构中的应用与发展，以期促进我国土建结构工程中对这一新型高性能材料应用和研究工作的开展．
A reinforcing technology using prestressed carbon fiber-reinforced polymer (CFRP) laminates was proposed for reinforcing steel purlins under bending. The reinforcing system can prestress CFRPs without using a hydraulic jack, which enables convenient construction and high reinforcing efficiency. The flexural behavior of the reinforced steel purlins was studied experimentally and theoretically. First, the flexural failure caused by the local buckling or yielding of the upper flange was successfully delayed by the prestressed CFRPs; the flexural capacity and stiffness were improved by 14% to 18% and 28% to 31% in tests, respectively. Then, a calculation method for determining the flexural capacity and corresponding deflection was proposed, which gave accurate results compared with the test. This study provides useful references for reinforcing cold-formed thin-walled steel beams with prestressed CFRPs.
Pultruded fiber-reinforced polymer (FRP) composite is expected to be widely applied for civil infrastructures due to its advantages of lightweight, anti-corrosion, and industrial manufacturing. Its long-term performance has attracted increasing attentions from academia and industry. This paper presents a comprehensive review on experimental studies investigating the mechanical performance of pultruded FRP composites subjected to long-term environmental effects, including water/moisture, alkaline solutions, acidic solutions, low/high temperatures, ultraviolet radiation, freeze-thaw cycles, wet-dry cycles, and in situ environments. Over 1900 experimentally determined mechanical properties of FRP materials were collected, including tensile, compressive, flexural and shear strength and moduli. The reported test data were highly dispersed, and no uniform conclusions could be drawn from these data. Exposure to water and water-based solutions (alkaline and acidic solutions) had detrimental impacts on the mechanical properties of pultruded FRP materials, whereas other environmental effects induced various levels of degradation. The degradation mechanisms for each environmental effect were discussed, and the existing design approaches were presented. Based on the findings from this review, recommendations were proposed for future works. The database presented herein, which is the largest in the available literature, enables a comprehensive understanding of the degradation behavior of pultruded FRP composites. Moreover, this work can serve as a foundation for deriving predictive models for pultruded FRP materials exposed to long-term environmental effects.
The comfort of pedestrians on a footbridge is a rather complex problem that has been discussed for a long time. Vibration acceleration is generally accepted as the main controlling factor that influences pedestrian comfort. However, no consensus has been reached regarding which acceleration-based parameters should be used as an index for assessing comfort. Only simple comfort limits, rather than specific relationships between comfort and the corresponding indices, are currently available for assessing the vibration serviceability of a pedestrian bridge. In this study, the vibration acceleration of 21 pedestrian bridges in Beijing, China, were recorded under different service conditions, and questionnaire surveys on pedestrian comfort were conducted. The acquired testing and survey results were utilized to analyze the correlation between pedestrian comfort and bridge vibration. A procedure for assessing the vibration serviceability of pedestrian bridges considering pedestrian comfort is proposed based on the relation between pedestrian comfort and the maximum footbridge acceleration.
A novel composite concrete shear wall with FRP-Confined Concrete Cores (FCCCs) arranged in the boundary elements is proposed. A series of quasi-static tests are performed to evaluate the seismic performance of the proposed composite shear walls. The specimens are subjected to combined constant vertical loading and cyclic lateral loading. The tested variables include the concrete strength of FCCC, the number of FCCC in the boundary elements, and the cross-section of the composite shear wall. Based on the test results, systematic discussions on the seismic behavior of the composite shear walls, including the failure mode, the hysteretic response, the energy dissipation, the stiffness/strength degradation, etc., are presented. It is found that the composite shear walls demonstrate similar lateral load resistance but much better deformability and energy dissipation compared with ordinary RC shear wall. Finally, numerical simulations were performed based on the software OpenSees. The FE results were in good agreement with test results. The influence of various parameters on the seismic behavior of composite shear wall was discussed based on parametric studies.
The yield point is a very critical characteristic of structural performance in design and research of engineering structures, which is the basis of evaluating properties such as ductility, yield-ultimate ratio and so on. However, there is no unified definition and expression for yield point of structures. With the development of new mechanical behavior of emerging structural materials, the existing graphic method, the equivalent energy method, and the residual plastic deformation method are not suitable for them. In this paper, a unified expression of yield point for the typical materials including steel, concrete and fiber reinforced polymer is given based on the original definition of metal yielding under uniaxial tension. Then, for structural members and structures, the definition of the yield point based on the application conditions and the physical reality is proposed, which provides the basis for design of emerging material structures. As examples, this definition is applicable for reinforced concrete beams and short columns. Furthermore, a simplified method named Farthest Point Method is given, which has a specific physical meaning and a wide applicability. This method is more suitable for the computer programming. Based on existing experimental results of members and structures, the rationality of the farthest point method is verified by comparing the yield points defined by farthest point method and the presented definition. Thus, an explicit and unified definition for yield points of materials, members and structures is given in terms of the fundamentals and determination approach.
