This paper theoretically analyzes the symmetrical global buckling behavior of imperfect prestressed carbon fiber-reinforced polymer (CFRP) laminate-reinforced steel columns (PCRSCs) with two hinged supports under axial and eccentric compression loadings. First, the causes of the buckling of the component are revealed; either the steel yields or the CFRP becomes slack. Therefore, four buckling cases are found, and a theoretical calculation method for the buckling capacity is established. On this basis, a theoretical calculation method for the optimal CFRP initial prestressing force and maximum buckling capacity is built from physical explanations. The results of the theoretical method fit well with the test and finite-element results. Finally, a design method of PCRSCs is proposed for engineering applications, followed by a design example, by which the optimal reinforcing efficiency is realized.
Ultrahigh toughness cementitious composites are a kind of high-performance cementitious material with a characteristic of ductile fracture. Based on the continuum damage mechanics theory and flexural fatigue damage model, two damage propagation models of ultrahigh toughness cementitious composites are built. One is a linear bilogarithmic model with J-integral range as its independent variable, while the other one is a linear model on a semilogarithmic scale with fatigue stress level as its independent variable. However, according to former research, the J-integral depends strongly on specimens’ geometry, so the first damage propagation model is deeply influenced by material dimension. As a result, the second damage propagation model is more convenient in application, shows the material fatigue property in comparison with the first model. In order to prove these two models and obtain the parameters, a three-point flexural fatigue experiment on single-edge-notched fracture specimens is carried out. The results shows that the two models fit better with the experimental results, rather than the crack propagation law of ultrahigh toughness cementitious composites.
An experimental program that investigated the seismic performance of concrete-filled square steel tube with fiber-reinforced polymer (FRP)–confined concrete core (FCCC) column (SCFC) was conducted. Fourteen SCFC specimens were fabricated with four parameters of axial compression ratio, strength grade of concrete, thickness of FRP tube, and thickness of steel tube and tested under constant axial compression and reversed-cyclic lateral loading. Examinations of the test data resulted a number of significant conclusions with regard to the influence of the investigated column parameters on the performance of SCFC columns. Of primary importance, SCFC columns exhibit favorable energy dissipation and ductility, even when the columns were subjected to high axial loads. The results also indicate that SCFC columns delivered satisfactory lateral moment-bearing capacity and displacement ductility under high axial compression ratio. In addition, a good level of average stiffness and equivalent viscous damping ratio were examined. Furthermore, the variations of hoop strains along column height, the relationship of axial displacement–lateral drift ratio, and the plastic hinge length were examined to evaluate the seismic performance of SCFC columns.
<p>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.</p>
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.
In reinforced concrete (RC) structures, the sudden failure of a column is likely to cause severe progressive collapse due to the relatively weak tie force from the surrounding elements. Therefore, some effective strengthening measures can be used to improve the progressive collapse behavior of the structures. Fiber reinforced polymer (FRP) has been widely used in retrofitting the RC structures because of its advantages such as high strength, light weight, corrosion resistance, etc. Thereby, in this paper the progressive collapse behaviors of the glass-FRP (GFRP) strengthened RC substructures subject to a column-removal scenario were studied. A quasi-static experimental method was adopted to test the progressive collapse behavior of the substructures including control specimen and strengthened specimens. The influences of the strengthening schemes on the behavior of the tested specimens were studied by comparing all the test results. The experimental results demonstrate that the strengthening technology can enhance the progressive collapse resistance of the RC structures.
Mobile bridges are primarily to make span-crossing and form traffic path flexibly and rapidly. FRP (Fiber-reinforced polymer composite) is suitable for the construction of mobile bridge as its advantages of light-weight and high-strength. In this paper, the ANSYS optimization module is used to optimize the linear of the FRP bridge, in order to lose the weight of the bridge.
随着国家农机购置补贴政策的大力实施,广大农民朋友的购机热情高涨。但由于缺乏足够的专业知识,在选购农机具的过程中,往往变得犹豫不决。特别是大中型农机具的选购,需要花费很大的一笔资金,千万不可以掉以轻心。因此，以下五点可供参考。
No abstract is provided for this article.
No abstract is provided for this article.
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.
