Publications

材料、构件、结构的“屈服点”定义与讨论

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.

Sanders III、IV型跟骨骨折18例观察

目的：探讨塑性跟骨钛板治疗Sanders Ⅲ、Ⅳ型跟骨骨折的疗效。材料与方法：自2001年2月至2008年6月，对18例23足Sanders Ⅲ、Ⅳ型跟骨骨折，采用塑性跟骨钛板加自体髂骨植骨进行复位内固定治疗。结果：本组病例随访6～36个月，平均随访时间18．5个月。按Maryland足部评分标准评价，优8足，良11足，中3足，差2足，优良率78．2％。结论：本方法治疗SandersⅢ、Ⅳ型跟骨骨折复位满意，固定牢靠，术中自体髂骨植骨，术后早期关节功能锻炼，疗效肯定，是一种目前治疗Sanders Ⅲ、Ⅳ型跟骨骨折的较好方法。

Comparative Study on Static and Fatigue Performances of Pultruded GFRP Joints Using Ordinary and Blind Bolts

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.

Vibration Serviceability Assessment of Pedestrian Bridges Based on Comfort Level

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.

An ultra-lightweight CFRP beam-string structure

In this work, an ultra-lightweight beam string structure made of carbon fiber reinforced polymer (CFRP) composites was designed, optimized, fabricated and tested. ANSYS APDL was adopted to optimize the design of the structure. A four-point bending test was carried out to investigate the structural behavior. Despite of being a non-full-scale structure, an exceptionally high structural efficiency, 56 N/g, was successfully achieved. Additionally, finite element analysis was conducted to investigate the effect of prestressing force in tension string. The added prestressing was identified to be able to increase the flexural strength of the structure by up to 15%. Moreover, with the thickened tension string, for instance for the 2.0-mm-thick string, 3% prestressing was able to provide a significant increase of the flexural strength and stiffness by up to 28% and 115%, respectively. The increased flexural strength was attributed to the improved stress distribution of compression beam. The proposed CFRP beam string structure, having an ultra-lightweight and a high load-carrying capacity, has a great potential to be widely adopted in conceptual developments and practical applications, particularly when high structural efficiency is required.

Study on Dynamic Characteristics of Light-Weight FRP Footbridge

No abstract is provided for this article.

A Novel Approach for Martian Base Construction Using In-Situ Resources

<p indent="0mm">As the most similar exoplanet in the solar system, Mars is very important in the perspective of strategic value and significance. With the completion of the three missions of “orbiting, landing and patrolling” of Mars at one time, the Martian base construction has become the next important goal to promote our deep space exploration process. Through the investigation of the existing literature on the environment and resource conditions of Mars, comparing them with those on the moon and the Earth, a series of unique problems to be solved in the construction of Mars are put forward. Based on the investigation of technologies suitable for Mars construction, including excavation construction, chemical vapor deposition forming, fused deposition forming, and Martian regolith bonding forming, etc., a new scheme of automatic construction of Martian base based on in-situ resources is proposed, called “China Dome”, which components include an inflatable bag, carbon fiber skeleton, sulfur concrete cladding and hatches. This provides a new way to build a Martian base.

Experimental study on GFRP pipes under axial compression

No abstract is provided for this article.

Experimental Study on Mechanical Properties of Bamboo Culms and Joints Reinforced with GFRP Sheets

No abstract is provided for this article.

Axial compressive behavior of engineered cementitious composite confined by fiber-reinforced polymer

A novel hybrid member made from two kinds of composite materials, ductile engineered cementitious composite (ECC) as the core material and linear elastic fiber-reinforced polymer (FRP) as the confining material was proposed for application. A series of axial compressive experiments on FRP-confined ECC cylinders were carried out. The test results indicated that FRP-confined ECC specimens exhibited similar compression hardening behavior in the axial stress-strain curve to FRP-confined normal concrete specimens. Moreover, the “self-confinement” effect of ECC and the confinement stiffness of FRP had significant influence on the stress-strain response and failure mode. Based on the FRP strain distribution, a failure mechanism was proposed for FRP-confined cement-based materials under compression. FRP-confined ECC cylinders underwent three distinct stages under compression: formation of microcracks, formation of multiple cracks, and formation and propagation of major cracks. A qualitative model for FRP confined ECC was developed, which illustrates the effects of different tensile properties of cement-based materials on the failure mode and explains why the hoop rupture strain is lower than the ultimate tensile strain of FRP. In addition, fitting equations were proposed for predicting the compressive strength and ultimate strain of FRP-confined ECC cylinders at the ultimate state.

Novel self-anchored CFRP cable system: Concept and anchorage behavior

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.

Superior durability of high-performance pultruded GFRP composites subjected to coupled environmental effect of hygrothermal aging and solar radiation

Seismic performance of composite shear walls with embedded FCCCs in boundary elements

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.

An Experimental Study of Self-anchored Combined CFRP Cables

&lt;p&gt;Carbon Fiber Reinforced Polymer (CFRP) is an advanced material known for its lightweight, high strength, corrosion resistance, and fatigue durability, making it an ideal choice for cables in structural engineering. However, being an anisotropic material, CFRP faces challenges in anchoring due to its lower transverse mechanical properties compared to its tensile strength. In response to this issue, this paper designs and tests a self-anchored combined CFRP cable with variations in anchorage type, joint type, and CFRP plate thickness. The results reveal that interface shear stress causes delamination failure in the anchorage, leading to lower- than-expected load-bearing capacity. Through improved design and processing methods, interface damage in the anchorage is reduced, enhancing load-bearing capacity and achieving an ideal failure mode of cable body rupture.&lt;/p&gt;

Flexural behavior of light steel purlins reinforced by prestressed CFRP laminates

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.

Long-term bolt preload relaxation and contact pressure distribution in clamping anchorages for CFRP plates

Clamping anchorages are commonly used to anchor carbon fiber reinforced polymer (CFRP) plates, and the anchoring performance is significantly impacted by bolt preload. This research presents experimental and numerical investigations of long-term bolt preload relaxation in clamping anchorages for CFRP plates. First, a compression test was conducted to obtain the elastic modulus in the thickness direction of CFRP plates. Subsequently, four types of relaxation tests (single bolt, planar and curved anchorage, external load effect, and thickened anchorage) were conducted, considering the effects of the number of CFRP plates, anchorage type, external load, and initial preload. The elastic interaction during the tightening process was also investigated. The contact pressure distribution was simulated through the finite element method, which is in good agreement with the experimental results obtained from pressure papers. To fit relaxation test results and predict million-hour relaxation, different theoretical models were employed. The results indicate that the number of CFRP plates is crucial to preload relaxation, and the presence of CFRP plates introduces strong elastic interactions between bolts in the anchorage. Preload relaxation also increases under external loads and with the increase in initial preload. Curved anchorage has less bolt preload relaxation in the long term under external loads. Additionally, thickened anchorages have a more uniform contact pressure distribution due to the improved pressure diffusion mechanism.

Beam-column joints of FRP pultruded profiles: State-of-the-art review, performance evaluation and design method

A binary resin system of epoxy and phenol-formaldehyde for improving the thermo-mechanical behavior of FRP composites

A binary resin system combing epoxy and phenol–formaldehyde is proposed for improving the thermo-mechanical behavior of FRP composites. Five types of FRP plates with varying resin recipes were fabricated through compression molding process. Thermo-mechanical tests were conducted at various temperatures to evaluate the glass transition temperature and the mechanical properties of FRP plates. Owing to the cross-linking occurred between epoxy and phenol–formaldehyde, proposed binary resin system is able to increase the glass transition temperature as well as to improve the mechanical properties of FRPs. Predictive models are recommended to assist the practical design of FRPs with binary resin system.