Search

Web openings often need to be created in reinforced concrete (RC) beams for the passages of utility ducts and/or pipes. Such web openings reduce the cross-section area of the beam in the affected region, leading to decrease in its load-carrying capacity and stiffness. Therefore, a fibre-reinforced polymer (FRP)-strengthening system generally needs to be applied around the web opening to ensure the safety of the weakened beam. A number of studies have been conducted by researchers all over the world to examine the behaviour of RC beams with FRP-strengthened web opening/web openings, and plenty of useful findings have been generated. This article presents a critical literature review of existing relevant research from three aspects: experimental studies, numerical studies and theoretical studies. The effect of main factors, including the size, shape, location and number of the web opening, the shape and shear span ratio of the beam, the concrete strength, the loading scheme and the FRP-strengthening scheme, on the structural performance of RC beams with FRP-strengthened web opening/web openings have been thoroughly analysed and discussed. Finally, directions for future research based on the gaps which exist in existing studies are pointed out.

Debonding failures of FRP have been frequently observed in laboratory tests of reinforced concrete (RC) beams flexurally-strengthened with near-surface mounted (NSM) fibre-reinforced polymer (FRP). A number of numerical and theoretical studies have been carried out to predict debonding failures in NSM FRP-strengthened beams, and several strength models have also been proposed. The existing studies, however, were all based on the scenario of a simply supported beam tested under one or two-point loading, while the influence of load distribution has not yet been investigated. This paper presents the first ever study into the effect of load distribution on the behaviour of NSM FRP-strengthened RC beams. A series of large-scale RC beams flexurally-strengthened with NSM FRP strips were first tested under different load uniformities; then a finite element (FE) model, which can give close predictions to the behaviour of such strengthened beams, was developed; finally, the proposed FE model was utilized to investigate the influence of bond length of NSM FRP on the load uniformity effect. It was found that the load uniformity has a significant effect on the beam behaviour, and the degree of this effect varies with the bond length of NSM FRP.

This article presents a literature review of existing research on the strong column–weak beam design philosophy, which has been widely adopted in the seismic design of frame structures. A comprehensive review of this design philosophy, including its concept and research history, especially factors affecting the accurate calculation of the flexural capacity of beams [Formula: see text] and the determination of the column-to-beam flexural strength ratio [Formula: see text], is presented first. The development of design provisions of four representative countries for this design philosophy is also reviewed. The implementation of strong column–weak beam hierarchy in real structural design is then discussed, and existing problems are pointed out. Finally, different techniques for the seismic retrofit of existing reinforced concrete frames are reviewed.

Timber-concrete composite panels are commonly used as a sustainable alternative for reinforced concrete floor construction systems. Their performance also continues to advance with new approaches to interfacial shear connection and layer composition, for example as three-layer sandwich panels with a concrete compressive face layer, timber tensile face layer, and a cellular core. Due to significant difference in stiffness of the layers, such sandwich panels demonstrate large transverse shear deformations when subjected to bending. Existing finite element modelling techniques, relying on traditional shell or solid elements, can become computationally expensive when simulating the behaviour of sandwich panels. This paper presents a new composite element for simplified numerical modelling of sandwich panels, greatly reducing the computational effort. The proposed element comprises two face layers connected by an interlayer, with face layers considered as beams and the interlayer considered as springs. A numerical model was developed using the proposed element and was validated against finite element results of linear sandwich beams and experimental results of nonlinear, cellular-cored timber-concrete sandwich panels.

Extensive research has been conducted on the replacement of steel rebars with fibre-reinforced polymer rebars to eliminate the steel corrosion problem in conventional steel bar–reinforced concrete structures. However, as the performance of fibre-reinforced polymer rebars is substantially inferior in compression (due to issues such as fibre micro-buckling) than in tension, their use in concrete columns is generally not recommended; this poses a significant challenge when a steel-free structure is needed. This article presents a novel steel-free hybrid rebar developed at The Hong Kong Polytechnic University that overcomes the above-mentioned problem. Such a hybrid rebar typically consists of a central fibre-reinforced polymer rebar, an external fibre-reinforced polymer confining tube and an annular layer of high-strength cementitious material such as ultrahigh-performance concrete. To demonstrate the performance of these hybrid rebars, results from a series of preliminary tests and associated modelling work are presented in the article. These results indicate that (1) the fibre-reinforced polymer rebar at the centre is well supported against bar buckling and fibre micro-buckling, (2) the compressive strength of the fibre-reinforced polymer material can be fully mobilized and (3) the stress–strain response of hybrid rebars can be designed to resemble an elastic–plastic response with some post-yielding hardening.

UIDB/EMS/00667/2020 Nowadays, the use of the Digital Image Correlation (DIC) technique has spread and it is being used in several engineering areas to measure displacements. The available data obtained from the DIC measurement to evaluate the bond performance between a Carbon fibre Reinforced Polymer (CFRP) externally bonded to a timber substrate is scarce. From the existing data obtained with other materials, this contactless technique revealed to be quite useful but its accuracy with other well-established techniques, such as the use of electric strain gauges is not well understood yet. Therefore, the current work aims to study the accuracy of 2D DIC measurements with the measurements obtained from the use of strain gauges within a low-cost perspective. To that end, several CFRP-to-timber bonded joints were tested under the single-lap shear test and different bonding techniques were considered as well. Some flaws intrinsically derived from the DIC measurements that complicate the bond assessment, such as the fluctuations in the generated displacements field, are identified, and to bypass this problem a new methodology is proposed. This new methodology is based on two different closed-form solutions that, after defining the local and global bond behaviours of different CFRP-to-timber bonded joints, allowed to eliminate the fluctuations found from the DIC measurements, facilitating the estimation and the comprehension of the full debonding process of the CFRP-to-timber joints, which was achieved with a good proximity to the homologous debonding process derived from the strain gauge measurements. publishersversion published

The strong column-weak beam hierarchy, which is now widely accepted in the design of reinforced concrete (RC) frames to achieve good seismic performance , is violated in many existing RC frames designed according to inadequate design codes (generally previous codes). Against this background, a novel seismic retrofit method based on the flexural weakening-shear strengthening (FWSS) technique was proposed by the authors’ group to achieve the strong column-weak beam hierarchy in such frames. This technique involves the creation of an opening in the web of a T-section beam (or an alternative feature with a similar effect) for a reduction in the flexural capacity of the beam and the use of local FRP strengthening to avoid shear failure of the post-weakening beam to ensure a ductile failure process. To confirm/demonstrate the effectiveness of the FWSS technique, an experimental study consisting of a total of 8 full-scale RC beams was carried out. Test results presented in this paper show that a sizable web opening can effectively reduce the flexural capacity of a T-section beam and the FRP strengthening system is needed to avoid shear failure of the beam and confine the web chord created by the opening to ensure a ductile response.

The near-surface mounted (NSM) FRP strengthening technique has attracted worldwide attention as an effective alternative to the externally bonded (EB) FRP strengthening technique. In the NSM FRP strengthening method, grooves are first cut in the concrete cover of a concrete member for the FRP reinforcement to be inserted and embedded using an adhesive. The NSM FRP method has many advantages over the EB FRP method, including a higher bonding efficiency and a better protection of the FRP reinforcement. Existing experimental studies have shown that FRP strips owned a better bond efficiency compared with other section shapes (e.g. round bars and square bars), due to the fact that they had a larger perimeter-to-cross-sectional area ratio. This paper presents a state-of-the-art review, particularly on the flexural strengthening of RC beams with NSM CFRP strips. The observed failure modes in laboratory experiments of such FRP-strengthened RC beams are classified and the existing strength models are examined along with the failure mechanisms behind. The main knowledge gaps to be bridged in future studies are also identified. This review partially formed the basis of the development of design provisions on the NSM strengthening technique in the relevant Hong Kong design guideline.

FRP-confined concrete-encased cross-shaped steel columns (FCCSCs) are a new form of hybrid columns recently developed at the University of Wollongong. An FCCSC consists of a square FRP outer tube, a cross-shaped steel section and concrete filled in between. This sectional configuration ensures that the concrete is very effectively confined despite the square shape of the column. In addition, the cross-shaped steel section serves as the ductile longitudinal reinforcement for loads in the two lateral directions and its possible buckling is constrained by the FRP outer tube and the concrete, leading to a column that is highly ductile. In this paper, results from a series of stub column tests are presented to demonstrate the concept of the new column form. The experimental program involved the testing of FCCSC specimens as well as four types of similar column forms, namely, square FRP-confined plain concrete columns (SFCPCs), circular FRP-confined plain concrete columns (CFCPCs), concrete-encased cross-shaped steel columns and square plain concrete columns. The test results confirmed the excellent performance of FCCSCs. The test results also showed that compared with the concrete in SFCPCs and that in CFCPCs, the concrete in FCCSCs has a much larger ultimate axial strain and a larger compressive strength, when the same FRP tube is used.

In the strengthening of existing deficient structures using the near-surface mounted (NSM) FRP method, a group of parallel NSM FRP strips are usually needed to meet the capacity enhancement requirement. When the groove spacing (i.e., the net distance between grooves) is relatively small, the bond behaviour of each NSM FRP strip is detrimentally influenced by the adjacent grooves/FRP strips, and such detrimental effect should be taken into account for a safe design of the NSM FRP strengthening system. All the existing models, however, have been proposed for NSM bonded joints with a single FRP strip and thus cannot consider the effect of groove spacing on the bond behaviour, due to the insufficiency of data from tests or numerical simulations. Against this background, a numerical parametric study, was conducted to clarify the effect of groove spacing on the bond strength of such bonded joints; the numerical parametric study involved the use of a three-dimensional meso-scale finite element model developed in the present study for NSM bonded joints with two FPP strips separately embedded in two parallel grooves. Based on the results from the parametric study, a reduction factor to account for the detrimental effect of insufficient groove spacing on the bond strength is proposed and extended to NSM bonded joints with three or more evenly-spaced FRP strips. By combining the proposed reduction factor and the bond strength model previously developed by the authors for NSM bonded joints with a single FRP strip, a bond strength model for NSM bonded joints with multiple FRP strips is proposed and the accuracy of the proposed model is verified with test results.

Fibre-reinforced polymer–concrete–steel hybrid multi-tube concrete columns are a new form of columns recently proposed at the University of Wollongong. An multi-tube concrete column consists of an external fibre-reinforced polymer tube and a number of circular internal steel tubes, with the space inside all the tubes filled with concrete. This article presents the first ever experimental study on square multi-tube concrete columns. The experimental program included a total of 14 stub column specimens tested under axial compression, with the test variables being the thickness of the external fibre-reinforced polymer tube, and the dimensions and configuration of the internal steel tubes. The test results demonstrated that the concrete in the square multi-tube concrete columns was very effectively confined by the multiple tubes, and that the buckling of the internal steel tubes was completely prevented, leading to full structural utilization of the materials and a very ductile response. The test results also showed that the behaviour of the concrete in the square multi-tube concrete columns was significantly superior to that in the corresponding square concrete-filled fibre-reinforced polymer tubes, in terms of the compressive strength, the ultimate axial strain and the stiffness of the second branch of the stress–strain curve. A simple analytical model proposed for the axial load-axial strain curve of square multi-tube concrete columns is also presented and is shown to provide reasonable and conservative predictions of the test results.

FRP-confined concrete-encased cross-shaped steel columns (FCCSCs) are an emerging form of hybrid columns, consisting of a square FRP outer tube, a cross-shaped steel section and a concrete infill. The steel section in FCCSCs serves as ductile longitudinal reinforcement, and its buckling is well constrained by the concrete and the FRP tube. In addition, the steel section provides confinement to the concrete together with the FRP tube, so that the concrete in FCCSCs is effectively confined despite their square cross section. This paper presents a systematic experimental study on FCCSCs. The test variables included the flange width, flange thickness and web thickness of the steel section, and the thickness of FRP tube. It is shown that the various steel sections in the tested FCCSCs all provided substantial confinement to the concrete, while the effect of the steel confinement is less pronounced for FCCSCs with a thicker FRP tube. The test results show that the variation of the cross-sectional dimensions of the steel section, within a reasonably wide practical range, has marginal effects on the behaviour of the concrete in FCCSCs. In addition, a simple method has been proposed to predict the axial load capacity and ultimate axial strain of FCCSCs.

In order to realize the strong column-weak beam hierarchy in existing reinforced concrete (RC) frames, a novel seismic retrofit technique (i.e., beam opening technique or BO technique) was proposed. The BO technique involves the cutting of a web opening in the RC T-section beam to weaken its flexural capacity , in combination with the installation of a fibre-reinforced polymer (FRP) strengthening system around the opening to offset the loss in shear capacity caused by the opening. While extensive experimental studies have verified the effectiveness of the BO technique, this paper presents a finite element (FE) study on the structural behaviour of RC beams with an FRP-strengthened web opening, for a more comprehensive and in-depth understanding of the performance of such beams. Two constitutive models of concrete were investigated, namely, the concrete damaged plasticity (DP) model and the brittle cracking (BC) model. Through detailed comparisons, it was found that for specimens failing in a flexural mode, the DP model is more appropriate; while for specimens failing in a shear mode, the BC model with the secant modulus of concrete adopted provides better predictions. A simple method for the selection of a proper FE approach is finally proposed.

A hybrid fiber-reinforced polymer (FRP)-concrete-steel double-skin tubular column (DSTC) consists of an outer FRP tube and an inner steel tube, with the space in between filled with concrete. This paper presents results from the first ever experimental study on hybrid DSTCs with a large rupture strain (LRS) FRP tube, namely, polyethylene terephthalate (PET) FRP tube. The experimental program involved the testing of 12 hybrid DSTC specimens with or without additional concrete inside the inner steel tube. The test results confirmed the ample ductility of hybrid DSTCs with a PET-FRP tube despite the severe local buckling of the inner steel tube at large axial deformations. The test results also suggested that the diameter-to-thickness ratio of the inner steel tube is a more critical parameter in such DSTCs than in DSTCs with a glass, carbon or aramid FRP outer tube.

Reinforced concrete cantilever slabs are among structures that are most likely to develop structural integrity problems, as they are statically determinate and often exposed to the outdoor environment. This article presents an experimental study on the strengthening of reinforced concrete cantilever slabs where the anchorage of the top steel reinforcing bars into the adjacent wall was insufficient. The experimental study involved the use of a fibre-reinforced polymer strengthening system and fibre Bragg grating sensors for strain monitoring. The fibre-reinforced polymer strengthening system consisted of glass fibre–reinforced polymer sheets and glass fibre–reinforced polymer spike anchors which connected the glass fibre–reinforced polymer sheets to the adjacent concrete wall. The test results showed that the fibre-reinforced polymer strengthening system was effective in improving the load-carrying capacity of reinforced concrete cantilever slabs and the fibre Bragg grating sensors worked efficiently and reliably for strain monitoring. The debonding in glass fibre–reinforced polymer sheet/glass fibre–reinforced polymer anchor-to-concrete bonded joints was found to be a progressive process associated with an increasing load. The fibre-reinforced polymer strengthening system examined in this study is thus a potential ductile solution for deficient cantilever slabs.

// Song Xue 1 , Shu Xiao-Hong 1 , Sha Lin 2 , Bian Jie 2 , Wang Li-Li 1 , Gu Jia-Yao 1 , Shi Shun 1 , Li Pei-Nan 3 , Wu Mo-Li 1 , Wang Qian 1 , Chen Xiao-Yan 1 , Kong Qing-You 1 , Zhang Peng 1 , Li Hong 1 , Liu Jia 1 1 Liaoning Laboratory of Cancer Genomics and Department of Cell Biology, College of Basic Medical Sciences, Dalian Medical University, Dalian 116044, China 2 Department of Radiology, Second Affiliated Hospital of Dalian Medical University, Dalian 116023, China 3 Department of Orthopedics, Second Affiliated Hospital of Dalian Medical University, Dalian 116023, China Correspondence to: Hong Li, email: lihongmcn@dlmedu.edu.cn Jia Liu, email: jialiudl@aliyun.com Keywords: resveratrol, orthotopic rat glioblastoma, lumbar puncture, STAT3 signaling, cell death Received: April 07, 2016 Accepted: September 20, 2016 Published: October 3, 2016 ABSTRACT Trans-resveratrol suppresses glioblastoma growth in vitro , but its effects on intracranial glioblastomas remain untested. Resveratrol crosses the blood–brain barrier, and lumbar puncture (LP) greatly increases its bioavailability in rat brains; therefore, we investigated the effectiveness of LP-administered resveratrol on orthotopic rat glioblastomas. Twenty-four tumor-bearing rats were separated into two groups: Group 1 receiving 100 μl saline containing 0.3% DMSO and Group 2 receiving 100 μl resveratrol (300 μM). Treatments started 3 days after transplantation in 2-day intervals until death. Intracranial drug availabilities, tumor sizes, average life spans and the impacts on STAT3 signaling, apoptosis and autophagy rates were evaluated. MRI imaging revealed that average tumor size in the LP group (495.8 ± 22.3 mm 2 ) was smaller than the control groups (810.3 ± 56.4 mm 2 ; P

FRP-confined concrete-encased steel I-section columns (FCSCs) are an emerging form of hybrid columns. An FCSC consists of an outer FRP tube, an encased steel section and a concrete infill. The FCSCs possess many advantages over conventional reinforced concrete columns, including the excellent corrosion resistance, excellent ductility and ease for construction. Existing studies on FCSCs, however, have been rather limited. This paper presents a combined experimental and theoretical study on the behavior of FCSCs under concentric and eccentric compression. The experimental program included the testing of a total of 14 specimens, with the main variables being the section configuration, the thickness of the FRP tube and the loading scheme. The theoretical part included the development of a model for section analysis based on the so-called fiber element approach. The test results showed that the buckling of steel section was well constrained and the concrete was effectively confined in FCSCs, leading to a very ductile response under both concentric and eccentric compression. The theoretical model was shown to provide reasonably accurate predictions of the test results.

Based on the survey of 105 new agricultural business entities in Santai County of Sichuan Province, we found that the demands of financial services for new agricultural business entities in Santai County mainly include credit services, settlement services, agricultural insurance services and mortgage and guarantee services. And different types of new agricultural operators have different demand for financial services. Finally, this paper puts forward some suggestions to further promote rural financial services by exploring the reasons for insufficient supply of rural financial services in Santai County.

For the passage of utility ducts and/or pipes, openings often need to be created in the web of a reinforced concrete (RC) beam. Such a web opening can lead to a significant decrease in the ultimate load (i.e., strength) of the beam due to the reduced cross-sectional area and/or the severing of some of the existing steel reinforcement (particularly stirrups). In such cases, an externally-bonded fibre-reinforced polymer (FRP) strengthening system may be installed around the web opening to ensure the safety of the weakened beam. While existing experimental and numerical studies have provided useful information on the structural behaviour of RC beams with an FRP-strengthened web opening, this paper presents a theoretical study on the strength of such beams. First, a relatively simple, iterative numerical procedure (referred to as the iterative method) based on the static method of plastic limit analysis for predicting the plastic limit load (i.e., strength) of RC beams with an FRP-strengthened web opening is proposed, and then a closed-form, algebraic strength equation (referred to as the strength model) for such beams is established as a simplified approach of the iterative method. The accuracy of the proposed iterative method and strength model is verified with test results.

This paper presents a study on circular fibre-reinforced polymer (FRP)-concrete-steel hybrid multitube concrete columns (MTCCs), which consists of an outer FRP tube, a number of inner small steel tubes to form a “steel wall” and concrete filled in the remaining spaces. The advantages of MTCCs include excellent axial load and deformation capacities, ease of construction, elimination/mitigation of difficulties in transporting and installing large steel tubes, and possibility of optimising the arrangement of the small steel tubes to improve structural performance. A total of 7 pairs of MTCCs, 4 pairs of concrete-filled FRP tubes (CFFTs), 4 pairs of concrete-filled steel walls (CFSWs) and 3 pairs of concrete-filled steel tubes (CFSTs) were tested in the present study, with the investigated parameters covering the thickness of FRP tube, the number and type of steel inner tubes, the type of concrete and status of the steel inner tubes. The test results lead to an in-depth understanding of the behaviour of MTCCs under axial compression. Furthermore, a comparison between the test results and predictions by a model previously proposed by the authors shows that the model can reasonably well predict the axial load–strain behaviour of MTCCs but largely underestimates the ultimate strain of the specimen. This model may be used for conservative design, while further investigation is needed for the development of a more accurate model.

The near-surface mounted (NSM) fibre-reinforced polymer (FRP) strengthening technique has become a viable strengthening method for reinforced concrete (RC) beams. Premature debonding failure of the NSM FRP strips is a common failure mode though that severely limits the effectiveness of the FRP intervention that results in reduced beam strength and deformability. The application of FRP U-jackets near the ends of the NSM strips offers a potential solution to the debonding problem. This paper presents the first systematic experimental investigation on the use of FRP U-jackets for delaying or preventing debonding failure in RC beams strengthened in flexure with tension face NSM FRP strips. A total of 11 large-scale RC beams were tested, with the investigated parameters being (i) arrangement of NSM carbon FRP (CFRP) strips, (ii) U-jacket material type, (iii) layout, width and inclination angle of FRP U-jackets. Failure modes, load-deflection and strain distribution responses of all tested beams were recorded. The test results bring clarity and understanding to the tested parameters and they also demonstrate the effectiveness of the U-jacket intervention.

The beam opening (BO) technique, which involves (1) the creation of a web opening in the beam to weaken its flexural capacity and (2) the fibre-reinforced polymer (FRP) shear strengthening around the opening to avoid shear failure of the beam, was proposed to realize the strong column-weak beam hierarchy in existing reinforced concrete (RC) frames, which were designed using previous codes and thus violated such hierarchy. In the present study, six large-scale T-section beams with a web opening of different sizes and made by different methods (pre-formed and post-cut) were tested to assess the effectiveness of BO technique and the test results are presented. The experimental study shows that the post-cutting method is feasible for making web openings in existing RC beams, the BO technique can effectively reduce the flexural capacity of the beam to the desired value if the size of web opening is appropriate, and the FRP strengthening can well compensate the loss of shear capacity and ductility of the beam caused by the creation of web opening. The present study provides a basis for the safe use of BO technique to achieve the strong column-weak beam hierarchy in existing RC frames.

Fibre-reinforced polymer (FRP)-confined concrete-encased cross-shaped steel columns (FCCSCs) consist of a square FRP outer tube with round corners, a cross-shaped inner steel section and concrete filled in the between. The unique configuration of FCCSCs ensures that the concrete in the columns is well confined despite the square column shape, as demonstrated by the relevant existing research. The existing work on FCCSCs, however, has been limited to the behavior of short FCCSCs under axial compression. With their optimal configuration, the use of FCCSCs means that considerably reduced section dimensions may be adopted for the same load demand, leading to relatively slender columns in practice. In addition, the load eccentricity is an important parameter to consider in the column design. This paper presents the first-ever experimental study on the behaviour of slender FCCSCs. The test variables in this study included the load eccentricity, the slenderness ratio of the column and the thickness of FRP tube. The test results confirm the excellent structural performance of slender FCCSCs, and show that the load capacity of FCCSCs decreases with the slenderness ratio and the load eccentricity. Nevertheless, the confinement effects on the behavior of FCCSCs were found to be remarkable even when the column slenderness ratio and load eccentricity are large.

The use of near-surface mounted (NSM) FRP composites for strengthening RC beams in flexure has become increasingly popular in the last decade. Compared to the externally bonded (EB) FRP strengthening method, the bond between FRP and concrete is much stronger when the NSM FRP strengthening method is used. However, debonding is still a likely failure mode in RC members strengthened with NSM FRP bars. The debonding in an NSM FRP-strengthened beam may initiate from either of the two ends of an NSM bar (i.e. end debonding) in the form of interfacial debonding or concrete cover separation, both of which are closely related to the existence of large localized interaction forces between the NSM bar and concrete near the bar ends in such beams. This paper presents an analytical solution for the interaction forces in RC beams strengthened with NSM FRP round bars, which are one of the most popular types of FRP bars used for NSM strengthening. The key elements of the proposed analytical solution are two interfacial stiffness parameters (i.e. tangential interfacial stiffness and normal interfacial stiffness). The validity of the proposed analytical solution is also verified using a sophisticated 3D FE model of a RC beam strengthened with a NSM round bar.

Making web openings in reinforced concrete (RC) beams is frequently required for the passage of utility ducts and/or pipes. Such web opening(s) leads to reduction of the strength and stiffness of the beam. To ensure the safety of the beam, a strengthening system applied around the web opening is needed. Existing experimental studies have confirmed the feasibility of using externally bonded FRP to compensate for the strength loss of the beams caused by the creation of web openings, while there have been very limited finite element (FE) approaches for predicting the behavior of such RC beams. Against this background, three alternative FE models developed using ABAQUS for the simulation of RC beams with an FRP-strengthened rectangular web opening are presented in this paper, including two models based on the brittle cracking model of concrete and one model based on the concrete damaged plasticity model. By comparing their predictions with test results collected from the published literature, the most proper FE approach is identified. By using this FE approach, parametric studies are conducted for the design of the FRP-strengthening system for a typical web opening-weakened RC beam, and a reliable FRP-strengthening system is recommended for use in practice.

The flexural performance of RC beams can be improved using externally bonded (EB) or near-surface mounted (NSM) fiber-reinforced polymer (FRP) reinforcement. One of the commonly observed failure modes of such FRP-strengthened RC beams is the end cover separation failure mode which involves the detachment of the bonded FRP reinforcement together with the cover concrete along the level of the longitudinal steel reinforcement. This paper presents a simplified 2-D (plane stress) nonlinear finite element (FE) approach for end cover separation failure in RC beams strengthened in flexure with either EB or NSM FRP reinforcement. In this simplified FE approach, only the part of the RC beam between the two cracks near the critical end of the FRP reinforcement is considered. This approach leads to the determination of the FRP debonding strain at the cracked section in the strengthened region adjacent to the crack at the end of the FRP reinforcement, which can then be used to determine the moment acting on this cracked section at debonding failure through conventional section analysis. The validity of the proposed simplified FE approach is demonstrated through comparisons with results from the full 2-D (plane stress) nonlinear FE approach and laboratory tests.

The use of externally-bonded (EB) or near-surface mounted (NSM) FRP reinforcement in the strengthening of reinforced concrete (RC) beams in flexure has become increasingly popular in recent years. Such beams are likely to fail by end cover separation in which a major crack in the concrete initiates at a cut-off point of the FRP reinforcement and propagates along the level of steel tension bars, leading to the detachment of the FRP reinforcement together with the cover concrete. Due to the complexity of this failure mode, no reliable finite element (FE) approach for its accurate prediction has been published despite many previous experimental and theoretical studies on the problem. This paper presents a novel FE approach for predicting end cover separation failures in RC beams strengthened in flexure with either externally bonded or near-surface mounted FRP reinforcement. In the proposed FE approach, careful consideration is given to the constitutive modelling of concrete and interfaces. Furthermore, the critical debonding plane at the level of steel tension bars is given special attention: the radial stresses exerted by the steel tension bars onto the surrounding concrete are identified to be an important factor for the first time ever and are properly included in the FE approach. The proposed FE approach is shown to provide accurate predictions of test results, including load–deflection curves, failure loads and crack patterns.

A kind of design of 6-DOF transportation vibration platform was introduced. Based on the principle of Space Mechanism, the kinematics model of 6-DOF transportation vibration platform was described and the design of position servo-control system was presented. With a motion simulation experimental, the comparison results of Output/Input data in different directions were obtained. The results show that the vibration data are reproduced very well on the platform within the main frequency range in six directions.

Basic on the problem that the electromagnetic environment in vehicles which formed at the moment of ignition will cause interference to the stability and reliability of vehicle safety system, the paper takes vehicle fire protection system as the research object, and analyzes the interference mechanism and harmfulness through the simulation experiments. Finally uses the related software design and some prevention measures for electromagnetic interference such as shielding, grounding to protect the system, then through experiment to verify that it’s scientific and reasonable.

The movement and deposition of particulates play an important role under normal and abnormal operation conditions in nuclear power plants.The background, connotation and importance of the particulates influence on nuclear power plants security are analyzed. The basic characteristics, force and force models, and motion deposition models of particulates and the medium are summarized. The particulates distribution types of nuclear power plants in normal operation condition, design basis accidents and severe accidents conditions are given. The numerical simulation methods, program calculation methods and experimental methods for analyzing particulates motion characteristics at home and abroad are compared. It is concluded that the numerical simulation and the program calculation methods have the advantages of short period, low cost, and the experimental method is closer to the real situation. The three methods can complement and verify each other. The trend of numerical simulation and program calculation are in good agreement with the experimental results. The study on the motion characteristics of particulates in nuclear power system is still in its infancy, and it is necessary to understand its motion characteristics so as to minimize the hazards of particulates. The direction of future analysis methods for the movement of nuclear power particles is pointed out. It provides a theoretical basis for the study of the movement and deposition of particulates under normal operation and accident conditions in nuclear power plants.

A relatively recent method for the strengthening of concrete structures involves the embedding of fiber reinforced polymer (FRP) bars/strips into pre-cut, adhesive-filled grooves in the cover concrete. This paper presents a finite element (FE) study into the bond behavior of NSM CFRP strip-to-concrete bonded joints using a three-dimensional (3-D) meso-scale FE model developed by the authors. The effects of various parameters on the bond behavior of NSM CFRP strips are first clarified with the assistance of FE results, leading to the identification of the groove height-to-width ratio and the concrete strength as the two important parameters for the bond behavior. Based on the results of a FE parametric study on the effects of these two parameters, an analytical bond–slip model is proposed.

Vehicle-mounted shaft generator system with constant frequency and voltage under variable speed condition can adapt to a large speed range of working condition while the vehicle is moving. Its key technologies are a process of rectification-inversion and a composite staggered parallel DC converter. Test research shows that electrical performance of the shaft generator system meets the first kind electric power plant requirements according to GJB 5785-2006 of China, which indicates that the shaft generator system can provide uninterrupted high quality electric power to current general on-board electrical equipment on vehicles under all speed conditions.

The flexural performance of a reinforced concrete (RC) beam can be improved using the near-surface mounted (NSM) FRP strengthening technique. In the NSM technique, grooves are first cut in the concrete cover, and FRP bars are then placed in the grooves using a suitable bonding adhesive. In such an FRP-strengthened RC beam, debonding failure at the two bar ends may occur due to local high interaction forces in the bar-end regions between the RC beam and the FRP bars. This paper presents a theoretical investigation into these interaction forces in RC beams strengthened with NSM FRP rectangular bars (including FRP strips with a narrow rectangular section as a special case). By introducing and defining two interfacial stiffness parameters, an analytical solution for the tangential and the normal interaction forces between the beam and the NSM bars is first obtained based on the analytical solution developed by Smith and Teng for beams strengthened with an externally bonded FRP plate. The accuracy of the analytical solution is demonstrated by comparing its predictions with those from a 3-D linear elastic finite element (FE) model. The numerical results from both the analytical solution and the 3-D FE model confirms the existence of high interaction forces in the bar-end regions as the cause for bar-end debonding failure which has been commonly observed in tests. While the present paper is focused on RC beams strengthened with NSM rectangular bars, the proposed approach is general and is applicable to a range of similar problems such as RC beams strengthened with NSM bars of other cross-sectional shapes (e.g. circular and elliptical shapes) as well as timber beams strengthened with NSM bars.

We present a simulating experimental method used for studying the influence of impact mass on damping performance of impact dampers. The free mass in the impact damper had equal total mass but different size individual. We tested the damping effect of the damper under the same external force separately. The main results obtained in the experiments indicated that the impact damper had a good damping effect in the resonance region of the main system. The mass value of the free mass participating in vibro-impact was variable. In addition, the damping of the main system was related to the size of the free mass. In the conditions of equal total mass and same material, the size of the free mass was smaller, the effect of the vibration control was better.

Aimed at the problem of power supply protection on vehicles as the special project platform, making use of the surplus reserve power of vehicles and installing moving shaft generator system is introduced. Dynamics model of vehicle with shaft generator system is established, the impact of shaft generator system to the vehicle is analyzed, and compared with the dynamics of prototype vehicle, the dynamics matching method of vehicle with moving shaft generator system is obtained.

In this paper, the sulfation failure mechanism on negative plates of lead-acid batteries and the pulse-repairing technology are analyzed, and an online automatic maintenance device based-on the Boost converter is designed. The device uses ATmega16 microcontroller as its controller. The test results show that by adjusting the hardware devices and programs the frequency and amplitude of charge-and-discharge pulses can be changed. And when the battery voltage is too low the device can generate sound and light alarm. The device meets the design requirements.

As an alternative to externally bonded FRP reinforcement, near-surface mounted (NSM) FRP reinforcement can be used to effectively improve the flexural performance of RC beams. In such FRP-strengthened RC beams, end cover separation failure is one of the common failure modes. This failure mode involves the detachment of the NSM FRP reinforcement together with the concrete cover along the level of the tension steel reinforcement. This paper presents a new strength model for end cover separation failure in RC beams strengthened in flexure with NSM FRP strips (i.e. rectangular FRP bars with a sectional height-to-thickness ratio not less than 5), which was formulated on the basis of extensive numerical results from a parametric study undertaken using an efficient finite element approach. The proposed strength model consists of an approximate equation for the debonding strain of the FRP reinforcement at the critical cracked section and a conventional section analysis to relate this debonding strain to the moment acting on the same section (i.e. the debonding strain). Once the debonding strain is known, the load level at end cover separation of an FRP-strengthened RC beam can be easily determined for a given load distribution. Predictions from the proposed strength model are compared with those of two existing strength models of the same type and available test results, which shows that the proposed strength model is in close agreement with test results and is far more accurate than the existing strength models.

Design and implementation of six freedom transportation vibration spectrum collection system is presented in this paper. The Attitude and Heading Reference System (AHRS) is used to capture signals including x, y, z, direction linear acceleration, angular rates around Z-axis and pitch, roll degree. The software’s architecture and modules for host computer is designed with object-oriented analysis and design techniques, and the software is implemented with VC++6.0. The test results show that the system was able to collect vehicular vibration information on time and the collection data was replayed on the vibration platform.

In order to study the influence upper equipment load spectrum from upper spring mass, six freedom vibration signals on the vehicle was measured in a Chinese PG. The signals were the acceleration-time histories. Test was made under 3 loads conditions, which represent 3 types of upper spring mass. After filtering, rainflow counting, fatigue damage caused by the load spectrum was got. Result shows there were great difference in distributions between different direction load spectrums; spring upper load made small influences for the character of load spectrum at the same direction. The upper spring mass became larger, the equipment suffers more damage.

Based on the principle of Space Mechanism, the kinematics model of 6-DOF transportation vibration platform is described, and system kinematics analysis and calculation are finished. With an example, the displacement of actuator is solved according to the position and orientation of moving platform. The kinematics analysis is the basis of deciding system motion parameters, motion trajectory planning and system dynamics analysis.

A compact,low cost,stable noncollinear optical parametric chirped pulse amplification system is studied,which is seeded by an Yb3+-doped self-starting passive mode-locked stacking pulse fiber laser centered at 1 053 nm.A gain higher than 1.1×107,single pulse energy exceeding 11 mJ with fluctuations less than 2% rms,8 nm amplified signal spectrum are achieved.Different pulse durations of amplified signal are obtained by adjusting the stacker of the Yb3+-doped self-starting passive mode-locked stacking pulse fiber laser.

Bending fatigue is one of the main failure modes of gears. The method of gear fatigue design was discussed in many papers. Most of them are based on GB/T3480-83.But study shows that the method current widely used only fits for the single side loaded gear. For double sides loaded gear, only a mean stress modification coefficient is concerned compared to single side loaded gear. A new formula based on fatigue theory is given to modify the mean stress in consideration of the load character of doubled sides loaded gear. The method given in the paper is an addition to the traditional gear design method.

One of the biggest problems to predict the bending fatigue life of gear is lack of S-N data from the standard gear specimen. It is expensive and long time to spend to do the specimen tests. The bending fatigue property data from database is not enough to fulfill the engineering needs. To solve the problem, multiaxial methods are used to predict the bending fatigue life of gears and FEA method is used to analyze the stress of gear teeth root. Result shows that McDiarmid model, Findley model and Maximum shear stress model fulfill the engineering needs and McDiarmid method is the most accurate.

Spatial dispersion patterns of trees at different life stages are an important aspect to investigate in understanding the mechanisms that facilitate species co-existence. In this paper, Ripley’s univariate L(r) and bivariate L 12(r) functions were used to analyze spatial distribution patterns and spatial associations across different life stages of 131 tree species in a 20-ha plot of a tropical rainforest in Xishuangbanna, southwest China. Our results show that: (1) Saplings of 109 (83.2%) species have a significant clumped distribution, which confirms the ubiquity of clumped spatial distributions among tropical tree species. (2) Adults of 126 (96.2%) species have a random distribution suggesting that density-dependent mortality can make the spatial pattern of tropical trees more regular with time. (3) At small scales (0–10 m), 95 (72.5%) species have a neutral or negative sapling-adult association, implying that there is recruitment limitation within the vicinity of their conspecific adults. The reduction in spatial clumping in going from younger to older life stages and the neutral or negative sapling-adult association imply density-dependent mortality in the vicinity of adult trees. In accordance with the Janzen–Connell hypothesis, such density-dependent mortality can free up space for other species to colonize, contributing to the maintenance of species diversity.

Generally, it is relatively easy to obtain a high joint strength with most modern bonding systems if these are cured under ideal factory conditions. However, civil engineering construction joints are cured on site and are required to last the lifetime of the structural member in harsh environmental conditions. This implies that site joints might not be constructed and cured as well as those fabricated in the factory. The paper compares two possible methods for bonding an FRP composite patch/plate to a steel adherend suitable for construction sites. The first method utilises the accepted technique of bonding two dissimilar materials using a two-part cold cure adhesive. The second method employs a pre-impregnated FRP composite plate in conjunction with a compatible film adhesive; these comparisons are undertaken by examining the results of double-strap butt joint tests. A possible site technique using the pre-impregnated FRP composite to upgrade a steel beam whilst it is under a low frequency vibration load is investigated; this represents the repair of a steel bridge constantly under traversing traffic. The butt joint test results show that on average, the pre-impregnated composite in conjunction with the film adhesive leads to a failure load which is 15% higher than that of the cold setting adhesive technique. The results of the rehabilitated beam tests show that the bonded joint between the pre-impregnated CFRP composite and the steel adherend did not suffer any significant damage from the low frequency vibrations imposed upon the steel beam during the cure period.

Objective: To investigate prognostic impact of histopathologic response induced by neoadjuvant chemotherapy in patients with stage IIIA non-small cell lung cancer (NSCLC). Methods: Forty patients with stage IIIA NSCLC underwent two cycles of neoadjuvant chemotherapy with mitomycin, vindosine, and cisplatin followed by surgery. Histopathologic response in resection of the tumor was examined after surgery. Tumor regression was classified as grade IV, grade III, grade II, and grade I according to the extent of tumor necrosis and the extent of the vital tumor tissues. The tumor regression grading was correlated with the survival time of the patients. Results: After two cycles of chemotherapy, 19 (47.5%) of 40 patients had objective response (2 complete and 17 partial response). In 40 resected tumor specimens, 2 (5%) were classified as regression grade IV, 16 (40%) as regression grade III, 18 (45%) as regression grade II, and 4 (10%) as regression grade I. The rate of complete surgical resection was significantly higher in patients with tumor regression grade III-IV (

This paper is concerned with the development of an accurate bond strength model for carbon-fiber-reinforced polymer (CFRP) strips near-surface mounted (NSM) to concrete where debonding occurs as a result of cohesion failure in the adjacent concrete. Based on an existing analytical solution and the fracture energy equation recently developed by the authors, a bond strength equation is first proposed for NSM CFRP strip-to-concrete bonded joints with a sufficient bond length (i.e., the bond length exceeds a threshold value referred to as the effective bond length). The influence of an insufficient bond length on the bond strength is next examined through a parametric study conducted using a beam-spring numerical model in which a bond-slip model recently proposed by the authors is incorporated. Based on the numerical results, expressions are formulated for the effective bond length and the bond-strength reduction factor for insufficient bond lengths. The combination of these equations leads to a new b...

A review of the literature on various structural characteristics of reinforced concrete strongly suggests that, despite extensive research which dates back to the late 1960s, many unresolved problems still remain in the field. The purpose of the present paper is twofold. Firstly, for the simpler case when full bond may be assumed between the reinforced concrete beam and externally bonded plate up to ultimate load when the plate yields, a non-linear finite element method in conjunction with large scale test data from another source is used to throw some light on the influence of certain design variables such as the ratio of plate area to embedded steel reinforcement area on the beam's ultimate strength plus the effect of plate area on ductility at failure, and to investigate increases in the beam's overall stiffness in the presence of external plate in the case of both under- and over-reinforced designs. In the latter part of the paper, an improved version of a previously reported simple theoretical model for predicting the premature (ie peeling) failure of plates will be presented in some detail. This model extends the range of applicability to cases when the portion of the plate within the critical shear span (where it terminates) can be as long as is desired and unlike the previous model, which (for short enough lengths of plates within the shear span) assumed a uniform state of shear stresses at the plate/concrete interface, the present version can handle cases when non-uniform variations of shear stresses can exist. Most importantly it is argued that the plate peeling phenomenon is controlled by the spacings of the stabilized flexural cracks in the concrete cover, and, owing to large variations (by a factor of, say, two) in spacings of flexural cracks in practice, wide scatter is to be expected in the test data from even closely controlled experiments. (A)