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The study aims to propose a methodology to predict the fatigue performance of carbon fiber-reinforced polymer (CFRP) bars under the seawater sea-sand concrete (SWSSC) environment. The effects of exposure in SWSSC pore solution on the fatigue damage mechanisms and fatigue performance of CFRP bars are presented. Firstly, the tensile fatigue tests of reference CFRP bars were performed under various stress levels with a constant stress ratio of 0.1. Secondly, the tensile fatigue tests of exposed CFRP bars subject to the simulated SWSSC pore solution were carried out. The tensile failure modes and fatigue damage mechanisms corresponding to different stress levels, were identified using scanning electron microscopy (SEM). Besides, the relationship between fatigue life expectancy and underlying fatigue damage mechanisms was carefully analyzed. Finally, the effective stress level method (ESLM) was proposed to evaluate the residual fatigue life of exposed CFRP bars based on the benchmark S–N curve. Combined with the degradation models (chemical etching/diffusion models) proposed in our previous research, ESLM could bridge corrosion fatigue life prediction of the exposed CFRP bars and the benchmark fatigue data of the non-exposed CFRP reinforcement. The predicted results have good correlations with the experimental data. This method can also provide valuable insight for the corrosion fatigue life prediction of other types of FRP composites. [Display omitted] [ABSTRACT FROM AUTHOR]

This article presents an investigation on the durability of different glass-fibre-reinforced polymer composites when subjected to harsh outdoor conditions, including freeze/thaw cycles, ultraviolet radiation and moisture, as well as when used with seawater sea-sand concrete for construction applications. To achieve this, the effects of a number of parameters, including the environment of exposure, exposure time, profile cross-sectional configuration and orientation of fibres, on the mechanical properties of different glass-fibre-reinforced polymer composites were studied. To investigate the degradation of the mechanical properties, three-point bending, compression and tension tests were conducted on both reference and conditioned samples. Moreover, scanning electron microscopy analyses were performed to examine the contribution of microstructural deterioration to the damage mechanisms of the conditioned composites. Finally, the test results were used to develop empirical regression models to predict the level of retention of mechanical properties of different composites under different environmental conditions. The findings showed the maximum flexural, compressive and tensile strength reductions to be 35%, 48% and 37%, respectively, with regards to the pultruded profiles exposed for 3000 h to freeze/thaw cycles followed by 90 days of seawater sea-sand concrete immersion, while the flexural strength reductions recorded for the vacuum-infused samples subjected to 2000 h of freeze/thaw cycles followed by 90 days of seawater sea-sand concrete immersion were 28%, 72% and 56% for the unidirectional, woven and chopped strand mat laminates, respectively. [ABSTRACT FROM AUTHOR]

This article presents an experimental investigation on the durability behaviour of seawater sea sand concrete and seawater sea sand concrete–filled fibre-reinforced polymer/stainless steel tubular stub columns. Effects of NaCl of seawater on the strength of seawater sea sand concrete and on the deterioration of fibre-reinforced polymer were studied. Accelerated degradation tests were conducted on fibre-reinforced polymer rings exposed to a combined environment of 3.5% NaCl solution and seawater sea sand concrete. Obvious hoop strength reductions were observed in glass fibre-reinforced polymer and basalt fibre-reinforced polymer rings after 6-month exposure at 60°C. Seawater sea sand concrete–filled glass fibre-reinforced polymer tubular stub columns were exposed to an indoor environment (i.e. aged in air at room temperature) for a maximum duration of 2.5 years and no degradation was found by comparing the axial compressive test results from unexposed and exposed specimens. Seawater sea sand concrete–filled stainless steel tubes did not show any deterioration in strength after a 2.5-year exposure to an indoor environment or a 1.5-year immersion in NaCl solution. This study indicated that a hydrothermal environment (e.g. full immersion in solution) is much more aggressive to fibre-reinforced polymer than a dry environment. The reliability of using accelerated degradation test data to estimate the long-term performance of fibre-reinforced polymer–related structures in a real environment may need further research. [ABSTRACT FROM AUTHOR]

The solubilities in the quaternary system K+, NH4+//Cl−, SO42--H2O and its two ternary subsystems NH4Cl-KCl-H2O, (NH4)2SO4-K2SO4-H2O at 80.0 °C were measured using the isothermal dissolution equilibrium method under atmospheric pressure, and the corresponding phase diagrams were plotted. In the phase diagram of the NH4Cl-KCl-H2O system, there are three crystalline zones, which correspond to (K1−m,(NH4)m)Cl, ((NH4)n,K1−n)Cl and the co-existence zone of (K1−m,(NH4)m)Cl and ((NH4)n,K1−n)Cl, respectively. In the phase diagram of the (NH4)2SO4-K2SO4-H2O system, there is only one crystalline zone for (K1−t,(NH4)t)2SO4. In the phase diagram of the K+, NH4+//Cl−, SO42--H2O system, there are three crystal zones, which correspond to (K1−t,(NH4)t)2SO4, (K1−m,(NH4)m)Cl and ((NH4)n,K1−n)Cl, respectively. According to the analysis and the calculations for the phase diagrams of the K+, NH4+//Cl−, SO42--H2O system at 80.0 °C and 50.0 °C, this paper proposes a technological process. In the process, the (K1−t,(NH4)t)2SO4 can be prepared at 80.0 °C and the ((NH4)n,K1−n)Cl can crystallize out at 50.0 °C. The mass fraction of K2SO4 in product L1 (K1−t,(NH4)t)2SO4 (t = 0.1465) is 88.48%. The composition of solid solutions in the K+, NH4+//Cl−, SO42--H2O system was experimentally determined and then theoretical calculations about the process can be carried out. [ABSTRACT FROM AUTHOR]

Recently, in responding to the resource shortage and steel corrosion, the combination of seawater and sea sand concrete (SWSSC) and fibre reinforced polymer (FRP) bars was proposed to replace the traditional reinforced concrete structures in civil engineering. For FRP bars in the real service condition of concrete structure, the synergistic effect of sustained load and corrosion environment needs to be considered. This paper presents an investigation on the durability of basalt- and glass-fibre reinforced polymer bars exposed to a SWSSC environment under different sustained stress levels. Scanning electron microscopy was employed to study the degradation mechanism of FRP bars. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the thermal properties of alkali-activated slag paste, mortar and concrete utilising seawater and sea sand exposed to elevated temperature. The thermal properties of paste and concrete utilising cement, fresh water and river sand were also investigated for comparison purpose. The samples were heated to different target temperatures up to 1000 °C at a heating rate of 5 °C/min, and tested both under hot and cooled conditions. The thermal properties, including temperature gradient, visual observation, mass loss, thermal strain and mechanical properties (i.e. strength, Young’s modulus and stress-strain curve) were investigated. X-ray CT scanning and scanning electron microscopy (SEM) were conducted to understand the macro/microscopic changes of the paste and concrete in response to heating. Degradation in mechanical properties of slag paste is attributed mainly to the cracks induced by temperature gradient, pore pressure and phase change. The degradation of concrete is caused by thermal mismatch between paste matrix and aggregates regardless of the use of cement or slag, freshwater or seawater, and river sand or sea sand. [ABSTRACT FROM AUTHOR]

Interlaminar shear behaviour has been investigated for basalt-, glass- and carbon fibre reinforced polymer (BFRP/GFRP/GFRP) bars in seawater and sea sand concrete (SWSSC), using an accelerated test. The investigation includes the influence of different short beam shear test methods and the effect of test span-to-diameter ratios on interlaminar shear strength. The degradation mechanism of FRP bars in SWSSC solutions has been characterised using moisture absorption and desorption tests, scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The long-term shear behaviour of BFRP/GFRP/CFRP bars in SWSSC environment has been predicted using Arrhenius theory. [ABSTRACT FROM AUTHOR]

This paper presents a study on the long-term performance of basalt- and glass-fibre reinforced polymer (BFRP/GFRP) bars in seawater and sea sand concrete (SWSSC) environment. Accelerated corrosion tests were conducted using two types of SWSSC solutions at different pH and temperatures, and for different durations. The tensile tests of pre-exposed bars suggested the GFRP bars to be more durable than BFRP bars, while the Young’s modulus of all specimens remained unchanged. Scanning electron microscopy (SEM), X-ray computed tomography (CT) and energy dispersive X-ray spectroscopy (EDS) results were utilized to explain the damage mechanism. The long-term behaviour of BFRP and GFRP bars under the service construction condition was also predicted using Arrhenius degradation theory. [ABSTRACT FROM AUTHOR]

In this research, bone marrow mesenchymal stem cells (BMSCs) were isolated from mouse, and induced differentiation into myocardial cellsin vitroafter overexpression of miR-1a. The results showed that the BMSCs could induce differentiation into myocardial cells under the special condition medium, but when the miR-1a was over-expressed in BMSCs, the differentiation efficiency and induction time of myocardial cells from BMSCs could be promoted. This reason was demonstrated that Delta-like 1 (Dll-1) was a transcriptional repressor of myocardium gene expression during myocardium differentiation, miR-1a reduced Dll-1 levels, leading to the accumulation of myocardium gene mRNA and a dramatic increase in myocardium gene protein. [ABSTRACT FROM PUBLISHER]

This paper presents a study on the hardness and compressive capacity of longitudinally welded very high strength (VHS) steel tubes. VHS tubes, with a nominal yield stress of 1350 MPa and an ultimate tensile strength of 1500 MPa, were welded longitudinally to Grade 300 steel plates using the GTAW welding method. The hardness in the heat affected zone (HAZ) dropped to around 40% of that of the VHS steel without welding. The lowest hardness occurred at a location of about 4 mm from the weld toe. The strength in HAZ of longitudinally welded VHS tubes is about 55% of that of VHS tubes. The newly derived HAZ strength reduction factor is applied to predict the load carrying capacity of VHS tubes longitudinally welded to plates, fabricated sections with VHS tubes as corners and concrete-filled fabricated sections. [ABSTRACT FROM AUTHOR]

Two new diterpenoids, named paecilomycine A ( 1) and paecilomycine B ( 2), including a novel skeleton with a five-membered lactone ring, together with three known labdane diterpenoids, rel-(1 R,3 S,4a S,5 R,8a S)-5-[(3 E)-4-carboxy-3-methylbut-3-en-1-yl]decahydro-3-hydroxy-1,4a-dimethyl-6-methylidenenaphthalene-1-carboxylic acid ( 3), botryosphaerin E ( 4), and agathic acid ( 5), were isolated from solid culture of the insect pathogenic fungi strain Paecilomyces sp. The structures of all compounds were established on the basis of comprehensive spectroscopic studies. The relative configurations of 1 and 2 were determined by single-crystal X-ray diffraction analyses. [ABSTRACT FROM AUTHOR]

This paper presents an assessment on the current yield slenderness limits under axial compression for cold-formed and built-up high strength carbon and stainless steel hollow sections. The definition of high strength steel in this paper refers to the materials with nominal yield strength or 0.2% proof stress which is greater than 700 MPa (Eurocode 3: Part 1-12) for carbon steel and greater than 480 MPa (Eurocode 3: Part 1-4) for stainless steel. A total of 147 stub column experimental results was compiled and assessed. Companion 46 finite element simulations were performed in this study and the results concurred with the experimental observations. The structural performance data showed that the current slenderness limits adopted in Eurocode 3, American and Australian Standards for both carbon and stainless steel under axial compression can be safely adopted for the high strength steel counterparts. New slenderness parameters and limits were also proposed to improve the design efficiency. [ABSTRACT FROM AUTHOR]

Strengthening steel structures using carbon fiber reinforced polymer (CFRP) materials has attracted much attention in recent years owing to their potential for fatigue crack repair and their convenience in construction. However, little is known about the efficiency of this strengthening method when applied to steel plates at different crack propagation stages. An experimental study was carried out on notched steel plates strengthened using CFRP laminates. 20 specimens were tested to evaluate the fatigue performance of the strengthened steel plates with emphasis on various degrees of initial damage, simulated by different lengths of slots, including 2%, 10%, 20%, 30% and 40% of the plate width. The effects of the retrofitted configuration and CFRP stiffness were also investigated. The "beach marking" technique and crack propagation gauges were adopted to monitor the fatigue crack propagation. The experimental results were very encouraging, demonstrating that the CFRP patches could effectively slow crack growth and extend fatigue life, regardless of the initial damage levels. More effective strengthening was found by using ultra-high modulus CFRP laminates, covering the initial cracks with CFRP and repairing at an earlier stage (i.e. smaller damage level). [ABSTRACT FROM AUTHOR]

An iron-based shape memory alloy (Fe-SMA) can be used to conveniently apply prestress strengthening via a heating and cooling procedure. Material-level tests demonstrated that prestress of Fe-SMAs is sensitive to mechanical and thermal loading. Durability of steel structures strengthened by Fe-SMAs when subjected to harsh service conditions, such as coupled thermomechanical cycles is not fully understood. In this study, high-cycle fatigue tests were conducted on damaged steel plates retrofitted with Fe-SMA strips. Four temperature scenarios were adopted: room temperature (RT), a low temperature (LT) of −20°C , a high temperature (HT) of 60°C, and a cyclic temperature (CT) from −20°C to 60°C. Results showed that regardless of temperature variation, the Fe-SMA presented reliable repairing effects on steel plates, of which, the fatigue life was 2.1–3.5 times larger than that of the unstrengthened samples. The difference in coefficients of thermal expansion (CTEs) between the Fe-SMA and steel, as well as loss of prestress of the Fe-SMA due to fatigue and thermal loading, both affected the fatigue performance of the retrofitted specimens. [ABSTRACT FROM AUTHOR]

• Tests on concrete filled stainless steel tubes (CFSST). • Tests on T-stub to CFSST connections with various blind bolt types. • Finite element analysis of CFSST and T-stub to CFSST connections. • Discussion of effects of bolt type, tube thickness and layout of bolts on performance. • Formulas to predict the initial stiffness and capacity of CFSST and T-to-CFSST. Tension zone of a bolted steel beam-to-column connection can be represented by an equivalent T-stub to column connection under tensile load as recommended in Eurocode 3. This paper presents an experimental and theoretical study on equivalent T-stub to concrete filled stainless steel tube connections (T-to-CFSST) and the basic component (CFSSTs). Both stainless steel blind bolts and normal bolts were selected for the connections. Effects of various parameters, including tube thickness, bolt layout, bolt size, bolt type and bolting method, on the performance of T-to-CFSST and CFSST were investigated. Compared to hollow tubes, filling concrete could greatly enhance the stiffness and strength of the connections. Anchorage between bolts and concrete could be improved by setting studs at bolt ends. A finite element (FE) model was developed in this study and its accuracy was validated by the experimental results. Parametrical study was conducted to investigate the effects of parameters that cannot be covered in experiments, such as material type, tube length and T-stub thickness, on the behavior of CFSST and T-to-CFSST. Based on the experimental and numerical results, theoretical models were proposed to estimate the load–displacement curves of CFSSTs and their stiffness, yield capacity and ultimate capacity. By adopting the concept of component method, formulas were also proposed to predict the stiffness, yield capacity and ultimate capacity of T-to-CFSSTs. In general, the prediction matched well with the experimental results of CFSSTs and T-to-CFSSTs. [ABSTRACT FROM AUTHOR]

Abstract: Apolipoprotein B mRNA-editing enzyme catalytic subunit 2 (APOBEC2) plays an important role in regulating and maintaining muscle development in mammals. In this study, we evaluated APOBEC2 mRNA abundance and protein expression and the results indicated that APOBEC2 mRNA was most abundant in skeletal and cardiac muscle, with relatively low expression in the gonads, gizzard and subcutaneous fat tissues of chickens. Immunoreactive APOBEC2 was localized to the cell nucleus of developing myocardium and skeletal myofibers. There were significant differences in mRNA and protein abundance among ages, tissues, and between males and females. In conclusion, APOBEC2 was expressed as the greatest in skeletal muscle and cardiac muscle where it localized to the nucleus. Thus, APOBEC2 may play an important role in muscle development in chickens. [Copyright &y& Elsevier]

Abstract: Fiber reinforced polymer (FRP) materials were used to repair cracked non-load-carrying cruciform welded joints; and both the finite element method and the boundary element method were employed to study the fatigue crack propagation life of specimens repaired with FRP materials. The stress intensity factors (SIFs) were calculated for cracked welded joints that were unrepaired or were repaired with various FRP materials. The reduction of the SIFs for the repaired specimens was evident with the comparison of the control specimens. The fatigue life was then estimated with the NASGRO equation, which is modified from the Paris law. It was observed that the resulting fatigue improvement agreed with existing experimental data, indicating that fatigue strength can be upgraded with composite material repairs. The effects of various repair parameters on fatigue life were also examined. Single-sided repairs on cracked surfaces were more effective than double-sided repairs, due to the shift of the neutral axis. An increased modulus of FRP materials and adhesive achieved better fatigue performance. The use of more patch layers also had a positive effect, while increased adhesive thickness had a negative effect on fatigue life. [Copyright &y& Elsevier]

Box concrete-encased, concrete-filled steel tube (CFST) piers have been used in bridges in high-earthquake-intensity regions in China in recent years. They are expected to have higher strength and better ductility than normal box reinforced concrete members owing to the contribution of CFSTs in the corners of the composite box section. However, studies on this type of composite piers are limited. This paper presents an experimental study on the behaviour of box concrete-encased CFST columns under eccentric compression. A total of 14 specimens, including 12 box concrete-encased CFST specimens and two reference box reinforced concrete specimens are tested. The main parameters in the test are height-to-width ratio and load eccentricity. A simplified method is proposed to predict the load capacity of the box concrete-encased CFST columns. [ABSTRACT FROM AUTHOR]

Abstract: Extensive research has been conducted on static bond behaviour between CFRP and steel. However, very limited research is available on the effect of fatigue loading on the bond behaviour between CFRP and steel. This paper attempts to fill the knowledge gap in this area. A series of static and fatigue tests on UHM (ultra high modulus) CFRP plate and steel plate double strap joints were conducted. Five specimens were tensioned to failure under static loading as control specimens. The other 12 specimens were tested under fatigue loading with load ratios ranging from 0.2 to 0.6 (defined as the ratio of the maximum fatigue load to the average static bond strength of control specimens). After going through pre-set number of fatigue cycles, the specimens were tensioned to failure under static loading. The failure modes, residual bond strength and residual bond stiffness of such specimens were compared with those of control specimens, to facilitate the investigation of the effect of fatigue loading on the bond behaviour. Microscopic investigation was also performed to reveal the underlying failure mechanism. [Copyright &y& Elsevier]

The objective of this experiment was to evaluate the effect of dietary lysine concentration on meat quality and carcass traits in 2 chicken lines, SD02 and SD03, and their crosses, both originating from a Chinese native breed, the Erlang Mountainous chicken. The lines were selected for 4 generations by Sichuan Agricultural University (Ya'an, China); for the present study, chickens from the 2 lines and their crosses were randomly assigned at hatch to 1 of 2 dietary groups. One group was offered diets containing 1, 0.85, and 0.70% total lysine, whereas the other was offered diets with 1.15, 1, and 0.85% total lysine from d 1 to 28, d 29 to 49, and d 50 to 70, respectively. In total, 252 chickens were commercially processed at 70 d old. Traits measured included live BW, subcutaneous fat thickness, weight of carcass, eviscerated carcass, semieviscerated carcass, breast muscle (left pectoralis major and minor), leg muscle (boneless left drum plus thigh), heart, gizzard, proventriculus, spleen, liver, comb, and abdominal fat, color parameters lightness, redness, or yellowness (L*, a*, and b*), pH, and breast muscle intramuscular fat content. The results indicated that, although dietary lysine concentration did not affect subcutaneous fat thickness, color parameters, pH, intramuscular fat content, and organ weights, there were effects on feed conversion and muscle and BW (P < 0.05). Males and females displayed major differences in feed conversion, BW, muscle growth, and organ weight. The Line SD02 chickens grew faster and displayed less fat deposition and superior feed conversion compared with Line SD03 and the reciprocal crosses. In conclusion, performance of the chicken stocks evaluated in this study differs substantially in muscle weight and carcass weight [ABSTRACT FROM AUTHOR]

Abstract: The present work investigates an innovated methodology for manufacturing wet lay-up CFRP/steel double-strap joints and characterises their interfacial bond experimentally under infrastructural subzero exposures. A series of tensile tests is carried out on these joints after being conditioned at subzero temperatures ranging from −40°C up to 20°C. Three rheologically different epoxide resins and NM (normal modulus) unidirectional CF (carbon fibre) plies are used for the joints’ fabrication. Failure patterns, joint strength, and strain and LSS (lap-shear stress) distributions for the tested joints are obtained. Useful discussions and conclusions are provided, particularly those related to the influence of subzero temperatures and rheological properties of the current adhesives on the investigated parameters. [Copyright &y& Elsevier]

Abstract: Unidirectional normal modulus CFRP (CF130) and Araldite 420 and MBrace saturant adhesives are now commonly used to strengthen steel and concrete structures. However, there is a lack of understanding regarding their mechanical properties under dynamic tensile loads. This paper focuses on the experimental determination of the tensile mechanical properties of such materials at quasi-static and intermediate strain rates. A drop-mass rig and an impact Instron testing machine were utilised to conduct impact tests of CFRP and epoxy. It was found that the tensile properties of CFRP and the two adhesives are strain rate-dependent, even though their general trends and percentages of enhancement differ. Considerable changes in the failure patterns of CFRP and both adhesives are observed. Empirical equations in terms of strain rates are proposed to estimate the tensile properties of CFRP and both adhesives at any strain rate within the range considered. [Copyright &y& Elsevier]

Advanced carbon fiber reinforced polymer (CFRP) demonstrates promise for the fatigue strengthening of steel structures. By decreasing the stress field at the crack tip, the stress intensity factors (SIFs) can be effectively reduced by CFRP reinforcement. In this paper, the mode I SIF of CFRP-reinforced center-cracked tensile (CCT) steel plate is proposed based on a series of fatigue tests. The selected fatigue tests include experiments conducted by the authors as well as fatigue tests reported in the literature, covering different CFRP systems (low/high modulus, CFRP sheeting/plate) with various CFRP strengthening dimensions. The classical mode I SIF of CCT steel plate without CFRP strengthening is selected as the basis of the proposed solution. Then two reduction factors, similar to the correction factors given in the Japanese Society of Steel Construction (JSSC) standard, are introduced to study the effects of the mechanical properties of CFRP composites and the geometries of the CFRP reinforcement, respectively. Modified SIFs for both single-side CFRP-reinforced and double-side CFRP-reinforced CCT steel plates are proposed. It is found that the experimental SIFs of CFRP-reinforced CCT steel plates can be reasonably captured by the proposed mode I SIF formula. Finally, parametric studies for investigating the sensitivity of SIF to various mechanical and geometric factors are presented. [ABSTRACT FROM AUTHOR]

Abstract: The efficiency and the adequacy of bonding carbon fibre reinforced polymer (CFRP) composites to strengthen/repair steel elements largely depend on the bond between the steel elements and the CFRP composite. To ensure high performance and safer strengthening/repair procedures, it is important to provide sufficient bond between the patching system and the steel by choosing a suitable adhesive. Although strengthened/repaired structures are more likely to be subjected to dynamic loadings, the effect of different loading rates on the adhesion bond between CFRP sheets and steel has not been examined to date. This paper presents an experimental investigation of the assessment of the adhesive strength between CFRP and steel under various dynamic rates (3.34×10−5, 3.35, 4.43 and 5m/s) by utilising pull-off tests. The values from samples with one CFRP layer are higher than those with three layers for both Araldite 420 and MBrace saturant adhesives due to CFRP delamination. The loading rate affects the failure mode of samples with one CFRP layer for both Araldite 420 and MBrace saturant adhesives and remarkable changes are clearly shown at dynamic compared to static loadings. Conversely, the failure mode does not change for samples with three CFRP layers and remains CFRP delamination at all rates. Overall, the increase in pull-off strength is about 100% on average within the dynamic loading rates tested. [Copyright &y& Elsevier]

Abstract: The efficiency of the application of adhesively-bonded CFRP materials to rehabilitate and/or strengthen steel structures is completely dependent on the bond between the CFRP composites and the steel. As the repaired and/or upgraded structural elements are likely to be exposed to impact tensile loads during service, this necessitates the importance of understanding the bond strength between CFRP materials and steel under dynamic loadings. This paper presents the experimental procedure, the equipment and the test results for double strap joints at four speeds of loading to highlight the effect of loading rate on the bond strength. Two different CFRP layouts with various bond lengths were examined. It was found that the loading rate has significant influence on bond strength and failure modes, although it has little influence on the effective bond length. [Copyright &y& Elsevier]

This paper describes experimental and numerical studies on the fatigue behavior of steel connections under combined loads, including a cyclic load and a static load. The steel connections consist of two steel plates joined together by single-sided girth welds. They were tested to failure under a constant amplitude tensile cyclic load combined with varied tensile static loads, which are perpendicular to the cyclic load. The experimental results reveal that the presence of the tensile static load in the perpendicular direction to the cyclic load is able to reduce the fatigue crack propagation rate and hence extend the fatigue life. Modeling of the steel connections is described in this paper to determine the effect of the magnitude of tensile static load on fatigue propagation life. The Boundary Element Analysis System Software (BEASY) is used. The analyses of these tested specimens are compared with their experimental results. It is proved that the boundary element method through the BEASY software is able to provide a close estimation of the cyclic behavior of steel connections. [ABSTRACT FROM AUTHOR]

Carbon fibre reinforced polymer (CFRP) has shown promise for improving the fatigue performance of steel structures. Previous studies have indicated that increasing the Young's modulus of CFRP can be beneficial for decreasing the stress intensity factor at the fatigue crack tip. In this project, ultra high modulus (UHM) CFRP plates with Young's modulus of 460 GPa were adopted to study their fatigue repair effectiveness. A series of fatigue tension tests was carried out on steel plates with an initial crack in the centre. Five strengthening configurations were used and a constant amplitude fatigue loading was applied to all the specimens. The beach marking technique was utilized to record the fatigue crack propagation. The effects of CFRP bond length, bond width and bond locations on the fatigue performance of cracked steel plates were also studied. The experimental results show that UHM CFRP plates can greatly increase the fatigue life of cracked steel plates by a factor ranging from 3.26 to 7.47. When CFRP plates cover the whole crack surface, the fatigue crack of the steel plate is arrested. The strengthening effectiveness of UHM CFRP plates is also compared with those using high Young's modulus CFRP sheeting and normal Young's modulus CFRP plates with or without prestressing. [ABSTRACT FROM AUTHOR]

Abstract: External bonding of carbon fibre reinforced polymer (CFRP) sheets to the periphery of steel circular hollow sections (CHS) is a relatively new technique for structurally improving such sections. Design of CFRP sheets for strengthening tubular steel sections necessitates the prediction of the capacity of confined steel circular sections. This paper presents a design method for evaluating the capacity of CFRP-strengthened steel CHS subjected to bending. The hoop FRP reduces the effect of local buckling by restraining the tube wall. The influence of hoop CFRP is considered in the proposed method by taking its modulus of elasticity as a proportion of the elastic modulus of longitudinal CFRP. The excitation of the longitudinal CFRP minimises the effect of local buckling in the tube wall, which ultimately increases the local flexural stiffness and strength of the tube. The inclusion of the effects of strengthening parameters in current design rules, notably the Australian Standards AS/NZS 4600 (2005) and AS 4100 (1998) and the European Standard EC 3, is discussed. The strengthening effects considered here are those that arise from varying amount of CFRP, modulus of elasticity of the hoop fibre and steel yield strength. Strength curves for composite CFRP-steel CHS are provided to illustrate the extent of enhancement with the type of the parameter. [Copyright &y& Elsevier]

Cracked cross-beam connections made of thin-walled rectangular hollow sections (RHS) are repaired with carbon fiber-reinforced polymer (CFRP) sheets. Constant amplitude fatigue experiments are conducted on the repaired specimens. A pilot test is conducted on a T-connection of square hollow sections (SHS) to explore the effective method of applying CFRP. Due to the peeling effect at the corner region of the SHS-to-SHS connection, early debonding happens in the pilot test that only results in a slight extension in fatigue life. In the following experiments of repairing RHS-to-RHS cross-beam connections, circumferential or transverse restraining CFRP patches are applied in the corner region that prevents early debonding successfully and leads to significant increase in fatigue life. Finally, an improvement is made with the addition of steel strengthening plates that increase both the flexural stiffness and fatigue life of the cracked specimens significantly. The proposed retrofitting method may be useful for repairing other similar fatigue-cracked welded tubular connections. [ABSTRACT FROM AUTHOR]

Abstract: Concrete filled double skin tubular columns (CFDST) have excellent structural behaviour. They have been used as transmission towers and have potential to be used as building columns and bridge piers. Performance of the CFDST columns under ambient temperature has been well studied, whereas fire resistance of such columns is still a major concern. A summary of a series of fire tests on CFDST columns conducted by the authors is briefly presented in the paper. A finite element numerical model is developed to analyse the fire behaviour of CFDST columns, namely thermal and structural responses under fire exposure. The model is verified by the test results and then used to perform parametric analyses. Parameters which have significant effect on the fire behaviour of CFDST columns are identified. Based on the parametric studies, suggestions on the fire resistance design of such columns are made. Practical design tables are derived for the fire resistance design of some typical CFDST columns. [Copyright &y& Elsevier]

In plants, flowering as a crucial developmental event is highly regulated by both genetic programs and environmental signals. Genetic analysis of flowering time mutants is instrumental in dissecting the regulatory pathways of flowering induction. In this study, we isolated the OsLF gene by its association with the T-DNA insertion in the rice late flowering mutant named A654. The OsLF gene encodes an atypical HLH protein composed of 419 amino acids (aa). Overexpression of the OsLF gene in wild type rice recapitulated the late flowering phenotype of A654, indicating that the OsLF gene negatively regulates flowering. Flowering genes downstream of OsPRR1 such as OsGI and Hd1 were down regulated in the A654 mutant. Yeast two hybrid and colocalization assays revealed that OsLF interacts strongly with OsPIL13 and OsPIL15 that are potentially involved in light signaling. In addition, OsPIL13 and OsPIL15 colocalize with OsPRR1, an ortholog of the Arabidopsis APRR1 gene that controls photoperiodic flowering response through clock function. Together, these results suggest that overexpression of OsLF might repress expression of OsGI and Hd1 by competing with OsPRR1 in interacting with OsPIL13 and OsPIL15 and thus induce late flowering. [Copyright &y& Elsevier]

Abstract: External bonding of fibre reinforced polymer (FRP) composites has emerged as a popular technique for strengthening steel structures in recent years. In this study, the non-linear behaviour of circular hollow steel beams bonded with thin carbon FRP sheets was investigated theoretically by including the effect of the amount of CFRP reinforcement, fibre configuration, fibre and adhesive volume fractions and material non-linearity. This paper presents a cross-sectional analysis for the moment–curvature response of CFRP-reinforced steel tubular beams. Numerical results are presented to illustrate the strengthening effect of fibre composites, and are shown to be in reasonable agreement with previous experimental data. [Copyright &y& Elsevier]

Abstract: This paper presents the design and experimental evaluation of externally bonded carbon fibre-reinforced polymer (CFRP) sheets for strengthening circular steel tubular short columns. In addition to its ease of handling due to its light weight, the high-strength CFRP sheet can provide a degree of restraint to delay buckling of the thin steel wall. Ten short cold-formed steel circular hollow section (CHS) columns, with externally bonded orthogonal (hoop and longitudinal) CFRP sheets, were tested under axial compression. The experimental results indicate that enhancement of the axial section capacity is possible by fibre-reinforcing the steel tube. The design variables investigated to evaluate the strengthening efficiency include the steel yield strength, the modulus of elasticity of the hoop fibre, and the amount and configuration of the fibre reinforcement. Design curves predicting the section capacity of composite steel–CFRP tubular short columns are calculated based on current design guidelines for steel columns. The results highlight the ease of the use of such curves in the FRP strengthening or retrofitting design of tubular columns for section capacity enhancement. [Copyright &y& Elsevier]

Abstract: A concrete-filled double skin tube (CFDST) is an innovative steel and concrete composite construction with the potential to be used as columns in high-rise buildings. Self-consolidating concrete (SCC) can offer convenience for construction and ensure the construction quality of CFDST columns. There is very limited knowledge about the fire performance of CFDST columns, which is a key issue in the application to high-rise buildings. This paper reports an experimental investigation into the fire behaviour of CFDST stub columns filled with SCC and fibre reinforced SCC. The study aims to obtain thermal and structural responses of the stub columns through standard fire testing. Details are given in terms of the failure mode, temperature distribution, critical or limiting temperature and fire resistance. It was found that the added fibre does not affect the temperature distribution whereas the increased concrete thickness and outer tube perimeter reduces the temperature in CFDST specimens. The added steel fibre increases the fire resistance of CFDST stub columns especially for load levels less than 0.6. The critical or limiting temperature for CFDST sections was found to be higher than for CFST (concrete-filled steel tube) or unfilled tubes. [Copyright &y& Elsevier]

Abstract: This paper presents the results of a series of tension tests on CFRP bonded steel plate double strap joints. The main aim of this research is to provide detailed understanding of bond characteristics using experimental and numerical analysis of strengthened double strap joints under tension. A parametric study has been performed by numerical modelling with the variables of CFRP bond lengths, adhesive maximum strain and adhesive layer thicknesses. Finally, bond–slip models are proposed for three different types of adhesives within the range of the parametric study. [Copyright &y& Elsevier]

Abstract: This paper reports a series of tests on CFDST (concrete-filled double skin tube) stub columns subjected to large deformation axial loading. Both the outer and inner tubes are circular hollow sections (CHS) with a diameter-to-thickness ratio ranging from 19 to 96. It was found that CFDST significantly improved the behaviour of CHS in terms of failure modes, load carrying capacity and energy absorption. Multiple folds were formed in CFDST under large deformation axial loading. The load drop during cyclic loading was found to be insignificant (about 20 to 30%). The behaviour after the cyclic loading was influenced by the stage of the cyclic loading and the ratio. [Copyright &y& Elsevier]

Abstract: In recent years, there has been an increased use of concrete-filled composite tubular joints in bridge construction. The reliability of these joints under fatigue therefore need to be investigated to avoid any catastrophic failures. In this paper, hollow section T-joints made up of square hollow section (SHS) chords and braces are investigated. The chords of the SHS–SHS T-joints were concrete-filled thereby forming welded composite tubular T-joints. The SHS–SHS T-joints with concrete-filled chords were strain gauged and tested under static loading to determine stress concentration factors (SCFs) at hot spot locations, where cracks are likely to propagate. Fatigue tests of the welded composite joints were also carried out under cyclic in-plane bending in the brace to obtain stress range vs. number of cycles (S–N) data. The maximum stress concentration factor (SCF) at hot spot locations in a welded composite tubular T-joint was found to be generally lower than the maximum SCF in an empty (or called unfilled) hollow section SHS–SHS T-joint. Fatigue failure in welded composite tubular T-joints occurred through the initiation and propagation of cracks at weld toes in either the chord or brace member, with the majority of tests exhibiting the first visual crack at weld toes in the chord. The welded composite tubular T-joints were found to have better fatigue strength compared to the empty hollow section SHS–SHS T-joints. Design rules are recommended for the SHS–SHS T-joints with concrete-filled chords through analysis of fatigue test data using the hot spot stress method. [Copyright &y& Elsevier]

Abstract: We selected useful antibody fragments against rabies virus from a human single chain variable fragment (scFv) gene library using ribosome display technique. The recombinant rabies virus glycoprotein (RVGp) was used as an antigen to isolate specific scFvs. After five rounds of selection, the analysis demonstrated that scFv–ribosome–mRNA complexes were specifically selected against RVGp. Sequence analysis showed that mutations were introduced at random by PCR among the rounds of selection and variants with high affinity were isolated. The obtained scFvs with high affinity could recognize RVGp specifically and showed binding activity to rabies virus. These scFvs were potential for inclusion in a combination of several human monoclonal antibodies (MAbs) aimed for application in rabies post-exposure prophylaxis. Ribosome display technology is a robust tool for rapid isolation of human antibody fragments, and has exceptional strength in affinity maturation and molecular evolution in vitro. [Copyright &y& Elsevier]

Abstract: This paper expands the studies on the fatigue behaviour of CFRP-sheet reinforced steel plates using the numerical method of boundary element analysis. The numerical software program BEASY was adopted in calculating stress intensity factors, crack propagation and fatigue lives. The composite patch and the cracked steel plate were simulated using surface elements, whereas the adhesive layer was simulated as interface elements to connect the patch and steel plate. This method was validated by the good agreement between the numerical and experimental results. The influences of bond length, bond width, patch configuration, CFRP layer number, the modulus of the composite patch and adhesive shear modulus on the stress intensity factors and their fatigue lives were then evaluated using the boundary element method. [Copyright &y& Elsevier]

Abstract: This paper reports an investigation into the behaviour of high strength SCC (self-consolidating concrete) filled steel tubular stub columns exposed to standard fire. A series of tests were carried out to obtain the temperature distribution, axial deformation, limiting temperature of steel and fire endurance of the SCC filled steel tubular stub columns. In addition, a finite element analysis (FEA) model was proposed and used to simulate the fire behaviour of the columns. In the FEA modeling, a sensitivity study was conducted to determine the concrete fracture energy and the contact property of the steel and concrete interface. The verified FEA model was used to analyse the structural behaviour of the columns under fire exposure, such as strain, stress, the load sharing between the steel tube and concrete and local buckling of the steel tube, to gain an insight into the failure mechanism of the columns. [Copyright &y& Elsevier]

Abstract: This study was conducted to explore the modulation of GTPs on cognitive performances in psychological stress rats. Wistar rats were randomly assigned to five groups as follows: control group, stress group, and three stress groups with low, medium and high-doses of GTPs modulation respectively. The changes of cognitive performances were examined by open-field test, water maze and step-through test. Results demonstrated that serum levels of cortisol were all increased obviously in four stress groups. The cognitive performances of stress group were changed evidently. And these changes were improved in stress medium and high-doses of GTPs modulation groups. In addition, plasma levels of IL-6 and IL-2 were increased in four stress groups, serum norepinephrine and dopamine were decreased dramatically in stress group and stress low-dose GTPs modulation group. The serum norepinephrine and dopamine levels in stress medium and high-doses of GTPs modulation groups were increased in contrast to that of stress group. Furthermore, the changes of anti-oxidative capacity in brain tissue were also measured. Except superoxide dismutase, the changes of malondialdehyde, reactive oxidative species and total anti-oxidative capacity of stress group were significantly different from that of control group. These changes in stress medium and high-doses of GTPs modulation groups were improved. Our results suggested that psychological stress impaired body''s cognitive performances, and moderate GTPs modulation could improve these abnormal changes. To our knowledge, this is the first report showing the improving effects of GTPs on cognitive dysfunctions induced by psychological stress. [Copyright &y& Elsevier]

This paper presents an experimental study on blind bolted T-stub to square hollow section (SHS) connections made by stainless steel. Experiments were conducted to investigate the structural behaviour (e.g., failure mode, load–displacement curve and load-carrying capacity) of T-to-SHS connections and their basic components, including bolts, T-stubs and SHSs. The effects of key parameters, such as bolt types, bolt layouts, tube thicknesses and specimen configurations, on the performance of T-to-SHS connections and the components were identified. Design formulas were proposed to estimate the load-carrying capacities of T-stubs and SHSs, which agree well with the experimental results. The experimental results on connections between T-stub and steel hollow sections will provide a basis for verifying numerical simulations and theoretical analysis to derive design equations for such stainless-steel connections. • Tested stainless steel bolts, T-stubs and steel hollow sections. • Tested stainless steel blind bolted T-stub to square hollow section connections. • Discussed effects of bolt type, tube thickness and layout of bolts on performance. • Conducted theoretical analysis on T-stub and steel hollow sections. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes an experimental investigation of the cyclic inelastic flexural behaviour of concrete-filled tubes (CFT). Controlled-rotation, symmetrical cyclic bending tests were performed using a variable amplitude loading history on different sizes of CFT with different section slenderness. The CFT beams exhibited stable hysteresis behaviour up to local buckling and then showed considerable degradation in strength and ductility depending on the ratio. Seismic capacity parameters are presented including strength, hysteresis curves and modes of failure for the specimens. Peak moments obtained in the cyclic tests were compared with design moments predicted using a number of steel and concrete specifications. New section slenderness limits suitable for design and construction of seismic resisting structural systems were determined. A comparison is made between these seismic slenderness limits and the limits available in the design codes. [Copyright &y& Elsevier]

Abstract: The use of FRP (Fibre Reinforced Polymer) to strengthen steel structures has become an attractive option which may produce confident retrofitting of existing structures. This paper reviews the following areas that have received only small coverage in previous review articles, but have developed rapidly: the bond between steel and FRP, the strengthening of steel hollow section members, and fatigue crack propagation in the FRP–Steel system. Future research topics have also been identified, such as the as bond–slip relationship, the stability of CFRP strengthened steel members, and fatigue crack propagation modeling. [Copyright &y& Elsevier]

This paper clarifies the terminologies used to describe the size effect on fatigue behavior of welded joints. It summarizes the existing research on size effect in the perspective of newly defined terminologies. It identifies knowledge gaps in designing tubular joints using the hot spot stress method, i.e. thin-walled tubular joints with wall thickness less than 4 mm and thick-walled tubular joints with wall thickness larger than 50 mm, or diameter to thickness ratio less than 24. It is the thin-walled tubular joints that are addressed in this paper. It is found that thin-walled tube-plate T-joints do not follow the conventional trend: the thinner the section is, the higher the fatigue life. It is also found that simple extrapolation of existing fatigue design curves may result in unsafe design of thin-walled tube–tube T-joints. The effect of chord stiffness on fatigue behavior of thin-walled tubular T-joints is also discussed. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a plastic mechanism analysis to predict the complete load-shortening behaviour of fabricated square and triangular section (FSTS) stub columns. Very high strength (VHS) circular steel tubes with a nominal yield stress of 1350MPa are placed at each corner of the section and welded to Grade 350 steel plates to form a FSTS. Three stages are considered in the analysis: (1) both the VHS tube and steel plate are elastic, (2) plastic mechanism starts to form in steel plates while the VHS tube remains elastic (3) plastic mechanism occurs in both steel plates and the VHS tubes. Discussions are made on the factors affecting the types of mechanism (“flip-disc” versus “roof-type”) in steel plates and the effect of initial geometrical imperfection of the plates on the analysis. Simplified formulae were given for an easy application of the theory developed. The predicted load-axial shortening curves are in good agreement with those obtained by experiments. The predicted ultimate load carrying capacity is about 6% to 8% lower on average than the experimental capacity. [Copyright &y& Elsevier]

Abstract: This paper reports the improved web crippling behaviour of RHS (rectangular hollow section) strengthened by CFRP (Carbon Fibre Reinforced Polymer). Several types of strengthening were adopted, such as wrapping CFRP sheeting outside the RHS or applying CFRP plates outside or/and inside the RHS. It was found that the CFRP strengthening significantly increases the web crippling capacity especially for those with large web depth-to-thickness ratio. Design models are proposed to predict the increased capacity for CFRP strengthened RHS subjected to transverse end bearing force. [Copyright &y& Elsevier]

Abstract: This paper describes an experimental investigation of the cyclic inelastic flexural behaviour of cold-formed circular hollow section (CHS) beams. Controlled-rotation, symmetrical cyclic bending tests were performed using a variable amplitude loading history on different sizes of compact CHS with diameter-to-thickness ratios ranging from 20 to 40. The CHS beams exhibited stable hysteresis behaviour up to local buckling and then showed considerable degradation in strength and ductility depending on the ratio. Seismic capacity parameters are presented including strength, stiffness, hysteresis loops and modes of failure for each specimen. Peak moments obtained in the cyclic tests were compared with those obtained in monotonic and cyclic tests published previously and also with design moments predicted using a number of steel specifications. New section slenderness limits suitable for the design and construction of seismic resisting structural systems were determined. A comparison is made between these seismic slenderness limits and the limits available in the design codes. The effect of the number of cycles on ductility and energy absorption is examined. [Copyright &y& Elsevier]

Abstract: Welded thin-walled (t<4mm) tube-to-plate T-joints made up of cold-formed circular hollow sections welded onto a plate to form a moment resistant connection are used in the road transport and agricultural industry to manufacture equipment and other structural systems. Fatigue design of these joints is not available in current standards. An understanding of the stress concentrations and failure in these connections is therefore necessary as a step towards understanding the fatigue behaviour of these connections. Stress concentration factors (SCFs) of welded thin-walled (t<4mm) circular hollow section (CHS)-to-plate T-joints are determined at different locations along the weld toes on the tubular brace. The distribution of SCFs along the weld toes shows that the highest SCF occurs at the weld toes in the circular brace at the 0° line. The ratio of the end of test fatigue life (N4) to the through-thickness fatigue life (N3) in the thin CHS-plate T-joints is found to fall within the range of N4/N3 found in previous research of both thick and thin-walled joints. Surface crack growth monitoring is used to obtain an approximation of the length of surface crack at the point of occurrence of a through-thickness crack. The relationship between surface crack length and the occurrence of a through-thickness crack is important in that it can be used as a measure of the criticality of a surface crack during structural health monitoring of equipment or structures. [Copyright &y& Elsevier]