AbstractExisting studies have shown that fiber-reinforced polymer (FRP) jacketing/wrapping is highly effective in strengthening circular concrete columns but is much less effective for ...rectangular/square concrete columns due to the existence of flat sides and sharp corners in the latter. Rounding the corners can enhance the effectiveness of FRP confinement, but its benefit is limited, particularly for large-scale columns, because the corner radius is limited by the presence of internal steel reinforcement. An alternative strengthening technique therefore has been proposed by some researchers, in which the flat sides of a rectangular/square section are modified into slightly curved sides (i.e., curvilinearization) before FRP jacketing/wrapping. This section curvilinearization (SC) method increases the section size by only a limited extent but can substantially enhance the effectiveness of FRP confinement for rectangular/square columns. However, only very limited research has been conducted on curvilinearized rectangular/square columns (CRCs or CSCs), and the few existing studies are limited in scope and were conducted using small specimens. This paper presents the results of a systematic experimental program on the behavior of CSCs, in which 16 small-scale and 10 large-scale FRP-confined square concrete columns with or without section curvilinearization were tested under axial compression. A comparison of the results for columns of the two different sizes indicates that the size effect is very limited in these FRP-confined CSCs. The accuracy of two existing stress–strain models for FRP-confined concrete in CRCs was evaluated using the test results, revealing the need for the development of an improved stress–strain model for use in design.
Many stress–strain models have been developed for fibre-reinforced polymer (FRP)–confined concrete. These models fall into two categories: (a) design-oriented models in simple closed-form expressions ...for direct use in design; and (b) analysis-oriented models in which the stress–strain curve is generated via an incremental process. This paper is concerned with analysis-oriented models, and in particular, those models based on the commonly accepted approach in which a model for actively-confined concrete is used as the base model. The paper first provides a critical review and assessment of existing analysis-oriented models for FRP–confined concrete. For this assessment, a database of 48 recent tests conducted by the authors’ group is presented; this database includes 23 new tests which have not previously been published. This assessment clarifies how each of the key elements forming such a model affects its accuracy and identifies a recent model proposed by the authors’ group as being the most accurate. The paper then presents a refined version of this model, which provides more accurate predictions of the stress–strain behaviour, particularly for weakly-confined concrete.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Personalized cancer treatments using combinations of drugs with a synergistic effect is attractive but proves to be highly challenging. Here we present an approach to uncover the efficacy of drug ...combinations based on the analysis of mono-drug effects. For this we used dose-response data from pharmacogenomic encyclopedias and represent these as a drug atlas. The drug atlas represents the relations between drug effects and allows to identify independent processes for which the tumor might be particularly vulnerable when attacked by two drugs. Our approach enables the prediction of combination-therapy which can be linked to tumor-driving mutations. By using this strategy, we can uncover potential effective drug combinations on a pan-cancer scale. Predicted synergies are provided and have been validated in glioblastoma, breast cancer, melanoma and leukemia mouse-models, resulting in therapeutic synergy in 75% of the tested models. This indicates that we can accurately predict effective drug combinations with translational value.
AbstractFiber-reinforced polymer (FRP) jacketing/wrapping has become a widely accepted technique for strengthening/retrofitting reinforced concrete (RC) columns. Although extensive research has been ...conducted on FRP-confined concrete columns under concentric compression, leading to many stress–strain models, the applicability of these concentric-loading models in the analysis of columns under eccentric loading has not been properly clarified. This paper presents the development and application of a reliable three-dimensional (3D) finite element (FE) approach for an in-depth investigation into this problem. In the proposed FE approach, an accurate plastic-damage model recently developed by the authors’ group for concrete under a general state of multiaxial compression is employed. The accuracy of the proposed FE approach is demonstrated through comparisons with available tests. Numerical results from the verified FE approach are then presented to gain an improved understanding of the behavior of confined concrete in such columns (e.g., distributions of axial stresses and confining pressures), leading to the conclusion that the direct use of a concentric-loading stress–strain model in the analysis of an eccentrically-loaded column may lead to significant errors.
•Results of an experimental study on large-scale FRP-confined rectangular RC columns are presented.•The stress-strain curves of FRP-confined concrete in the test columns generally have a typical ...bilinear shape.•The corner radius ratio and the FRP jacket thickness are found to both have a significant effect on the stress-strain response of FRP-confined concrete.•Five typical stress-strain models are assessed using the test results.
Fiber-reinforced polymer (FRP) jacketing has become an attractive technique for strengthening/retrofitting reinforced concrete (RC) columns. Extensive research has been conducted on FRP-confined rectangular columns under axial compression, leading to a significant number of stress-strain models for FRP-confined concrete in these columns. However, most of these models have been developed based on test results of small-scale columns, so their applicability to large FRP-confined rectangular RC columns has yet to be properly validated. To this end, the present paper first presents the test results of an experimental study consisting of nine large-scale rectangular RC columns, including eight FRP-confined RC columns and one RC column without FRP jacketing as the control specimen, tested under axial compression. The experimental program examined the sectional corner radius and the FRP jacket thickness as the key test variables. Five representative design-oriented stress-strain models for FRP-confined concrete in rectangular columns, identified from critical reviews of the existing literature, are then assessed using the test results to examine their validity for these large-scale columns.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper presents an experimental study on the behaviour of CFRP-to-steel bonded interfaces through the testing of a series of single-lap bonded joints. The parameters examined include the material ...properties and the thickness of the adhesive layer and the axial rigidity of the CFRP plate. The test results demonstrate that the bond strength of such bonded joints depends strongly on the interfacial fracture energy among other factors. Nonlinear adhesives with a lower elastic modulus but a larger strain capacity are shown to possess a much higher interfacial fracture energy than linear adhesives with a similar or even a higher tensile strength. The variation of the interfacial shear stress distribution in a bonded joint as the applied load increases clearly illustrates the existence of an effective bond length. The bond–slip curve is shown to have an approximately triangular shape for a linear adhesive but to have an approximately trapezoidal shape for a nonlinear adhesive, indicating the necessity of developing different forms of bond–slip models for different adhesives.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
AbstractExtensive research has been conducted on FRP (fiber-reinforced polymers)-confined concrete columns under concentric compression, leading to many stress-strain models for such concrete. These ...concentric-loading (CL) stress-strain models have generally been used in the analysis of both concentrically and eccentrically loaded columns. Existing tests, however, have shown that eccentrically loaded FRP-confined concrete columns exhibit some behavioral aspects that cannot be closely predicted using a CL stress-strain model. This paper presents an in-depth investigation into this problem using an advanced three-dimensional (3D) finite element (FE) approach. The stress-strain response of concrete is shown to vary significantly over the section, and the direct use of a single CL stress-strain model for the entire section in the analysis of eccentrically loaded columns may lead to significant errors in the prediction of ultimate displacement/curvature. A stress-strain model for the confined concrete at the extreme compression fiber of the section is also shown to provide a relatively simple and much more accurate option for predicting the ultimate displacement/curvature of eccentrically loaded columns. Based on this conclusion, a so-called eccentricity-dependent (EccD) stress-strain model is proposed based on a comprehensive parametric study using the FE approach. The proposed model can be directly used in a section analysis or a theoretical column model and is proven to provide much more accurate predictions of the ultimate displacement/curvature of test columns than existing CL stress-strain models.
One important application of fibre-reinforced polymer (FRP) composites in construction is as FRP jackets to confine concrete in the seismic retrofit of reinforced concrete (RC) structures, because ...FRP confinement can enhance both the compressive strength and ultimate strain of concrete. For the safe and economic design of FRP jackets, the stress–strain behaviour of FRP-confined concrete under cyclic compression needs to be properly understood and modelled. This paper presents a stress–strain model for FRP-confined concrete under cyclic axial compression. The model consists of the following major components: (a) a monotonic stress–strain model for FRP-confined concrete developed by the authors in a previous study for predicting the envelope curve; (b) new algebraic expressions for predicting unloading and reloading paths; and (c) predictive equations for determining the permanent strain and stress deterioration, with the effect of loading history duly accounted for. The capability and accuracy of the proposed model in predicting the complete stress–strain history of FRP-confined concrete under cyclic axial compression are demonstrated through comparisons between predictions of the proposed model and test results.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
PDF
