Compressive performance of AFRP reinforced laminated bamboo stub columns

Engineered bamboo construction can be affected by natural defects, insects, corrosion, etc., which will result in damaging the mechanical properties of structural components. However, traditional reinforcement methods such as setting steel supports and increasing the cross-sectional area of components may cost a lot and cause a negative influence on the appearance of building. Many engineering practices and research works show that applying FRP (Fiber Reinforced Polymer/Fiber) sheet is an economical and efficient method for reinforcing and retrofitting building structures. Therefore, the compressive performance of AFRP (Aramid Fiber Reinforced Polymer/Fiber) reinforced laminated bamboo lumber (LBL) stub columns was studied in this paper. Through six groups (three replicates for each group) of stub columns with six different cloth ratios, the influence of AFRP on the failure pattern and mechanical properties of bamboo columns was explored. The test results showed that AFRP could effectively restrain the lateral deformation and improve the mechanical behavior of LBL columns. With the increase in cloth ratio, the ultimate strength and elastic modulus increased linearly in general, while the Poisson’s ratio gradually decreased. The reduced modulus of reinforced columns in the elastoplastic stage increased up to 161.31% compared with normal columns. Although the ductility of LBL columns laterally wrapped by AFRP was greatly improved, the initial stiffness, yield point and turning points between elastoplastic stage and plastic stage basically remained unchanged in contrast to unreinforced columns. Based on the test results, an empirical equation considering the cloth ratio was proposed to calculate the ultimate strength of AFRP reinforced LBL columns, using ‘Lam and Teng’ model. In addition, a simplified equation was also proposed to calculate the compressive strength of reinforced LBL columns derived from Mises yield criterion. The results of this work can be a reference to promote the application of strengthening and retrofitting engineered bamboo structure with FRP

Compressive Creep Behavior of NEXTEL™ 720/Alumina Ceramic Matrix Composite at 1200°C in Air and in Steam Environment

The aerospace community continues to push the envelope in engineering aircraft that fly higher, faster, and safer while operating with a greater degree of efficiency. To meet these operational requirements innovative aerospace components must be designed to operate in aggressive environments. This research will investigate the ultimate compressive strength and the compressive creep behavior of NextelTM 720/Alumina ceramic matrix composite at 1200 °C in air and 100% steam environments. The effects of creep loading history on the tensile and compressive material behavior will also be examined. The primary strengths of the N720/A composite are its oxide/oxide composition which inherently resists oxidation and a porous matrix which enables crack deflection producing enhanced matrix damage tolerance. Mechanical testing showed a significant decrease in the compressive performance of N720/A when exposed to steam environment. Conversely, N720/A specimens tested in compressive creep in air experienced an increase in compressive performance. SEM analysis showed that densification of the alpha-alumina matrix occurred in both test environments. In air densification sinters the matrix resulting in a strengthening effect. Whereas, in steam environment analysis shows the addition of hydrogen induces hydrothermal softening of the matrix resulting in a significant loss of the compressive performance of N720/A

Compressive performance of ECC-concrete encased high strength steel composite columns

The use of high strength steel (HSS) in the construction of concrete encased steel (CES) composite columns is often limited by the strain incompatibility issue between HSS and concrete at peak-load. This study proposes an alternative approach to confine the high strength concrete with Engineered Cementitious Composite (ECC) to improve its compatibility with high strength steel. The main purpose of this study is to experimentally evaluate the axial compressive performance of the proposed composite column cross-section configuration. Behaviours of fifteen short columns including twelve ECC-CES columns are investigated in terms of failure modes, load-deformation curves, ductility and energy absorption capacity. The test parameters included ECC and concrete strengths, ECC cover thickness, steel section shape and column section's aspect ratio. It was found that ECC generally improved the failure behaviour of high strength steel CES columns and increased the deformation and energy absorption capacity. On average ECC-CES columns showed around 12% and 8% higher ductility and toughness than control concrete column, respectively. A detailed 3D nonlinear finite element model was developed and validated against experimental results. Applicability of current design codes to predict the ultimate strength of ECC-CES columns was also evaluated. Finally, a method to calculate the ECC-CES column's capacity considering effective material stresses at peak-load was proposed

Compressive performance of fiber reinforced polymer encased recycled concrete with nanoparticles

Nanomaterials have been used in improving the performance of construction materials due to their compacting micro-structure effect and accelerating cement hydration reaction. Considering the brittle characteristic of fiber reinforced polymer (termed as FRP) tube encased concrete and inferior properties of recycled concrete, nanoparticles were used in FRP tube encased recycled aggregate concrete. The axial compressive performance of FRP tube used in recycled concrete treated with nanoparticles strengthening, termed as FRP-NPRC, were investigated by axial compression experiments and theoretical analysis. Five experimental variables were considered including (1) the dosages and (2) varieties of nanoparticles (i.e. 1% and 2% of nanoSiO2, 1% and 2% of nanoCaCO3), (3) replacement ratios of recycled coarse aggregates (termed as RCAs) (0%, 50%, 70% and 100%) the RCAs were mainly produced from the waste cracked bricks, (4) the number of glass FRP (GFRP) tube layers (2, 4 and 6-layer) and (5) the mixing methods of concrete. Results indicate that the combination of FRP confinement and nanoparticle modification in recycled concrete exhibited up to 76.2% increase in compressive strength and 7.62 times ductility improvement. Furthermore, a design-oriented stress–strain model on the basis of the ultimate condition analysis were executed to evaluate the stress–strain property of this strengthened component

Machine Learning-Based Prediction of Compressive Performance in Circular Concrete Columns Confined with FRP

This article presents a comprehensive investigation, focusing on the prediction and formulation of the design equation of compressive strength of circular concrete columns confined with Fiber Reinforced Polymer (FRP) using advanced machine learning models. Through an extensive analysis of 170 experimental data specimens, the study examines the effects of six key parameters, including concrete cylinder diameter, concrete cylinder-FRP thickness, compressive strength of concrete without FRP, initial compressive strain of concrete without FRP, elastic modulus and tensile strength of FRP, on the compressive strength of the circular concrete columns confined with FRP. The predictive model and design equation of compressive strength is developed using a machine learning technique, specifically the artificial neural networks (ANN) model. The results demonstrates strong correlations between the compressive strength of the circular concrete columns confined with FRP and certain factors, such as the compressive strength of the concrete and compressive strain of the concrete column without FRP, elastic modulus of FRP, and tensile strength of FRP. The ANN model specifically developed using Neural Designer, exhibits superior predictive accuracy compared to other constitutive models, showcasing its potential for practical implementation. The study's findings contribute valuable insights into accurately predicting the compressive performance of circular concrete columns confined with FRP, which can aid in optimizing and designing civil engineering structures for enhanced performance and efficiency

Improvement of compression performance of fiber reinforced polymer（繊維強化複合材料の圧縮特性の向上）

信州大学(Shinshu university)博士（工学）ThesisRUAN FANGTAO. Improvement of compression performance of fiber reinforced polymer（繊維強化複合材料の圧縮特性の向上）. 信州大学, 2015, 博士論文. 博士（工学）, 甲第646号, 平成28年03月20日授与.doctoral thesi

Experimental axial-compressive behaviour of bare cold-formed-steel studs with semirigid-track and ideal-hinged boundary-conditions

Studs are the primary load-bearing components in cold-formed steel (CFS) wall panels, connected to tracks at both ends with self-tapping screws, forming a semirigid boundary condition (BCT). Most existing tests on the axial compressive behaviour of bare CFS studs are based on either theoretically-hinged (BCH) or fully-fixed boundary conditions. Previous researchers have employed BCT only on sheathed stud-wall panels. However, practicing engineers and current design codes, e.g., Eurocode 3, follow an all-steel design. Therefore, this research experimentally investigated bare-CFS-studs' axial compressive behaviour with BCT, considering, for the first time, the combined effect of the tracks' warping rigidity, stud-to-track gap, non-linear connection stiffness, and bare studs' various cross-sectional slenderness. Forty-two industry-standard lipped channel sections (studs) of five thicknesses (1.2-3 mm), three depths (75–125 mm), and two heights (1.2 & 1.5 m) were tested under static-concentric axial compressive loading with BCT. Another fourteen studs were tested with BCH, a comparator to BCT. Results demonstrated that the studs' global failure mechanisms were flexural-torsional in BCT instead of flexural in BCH. Studs' axial stiffness was two-phased in BCT due to the stud-to-track gap, compared to single-phased stiffness in BCH. >1.8 mm stud-to-track gap caused stud-to-track connections' failure and studs' sudden capacity reduction during gap closure. Studs achieved 1.22 times higher axial-compressive strength, 2.3 times more axial-shortening, 0.7 times lower axial stiffness, and 58% lower axial-compressive strain at the web-midheight under BCT-PhaseII than BCH. Tested strengths were compared with EC3 design strength, and an effective-length-factor of 0.65 was suggested for efficient design of studs with BCT

Mechanical Enhancement of UHMWPE Fibers by Coating with Carbon Nanoparticles

Fiber-reinforced plastic (FRP) is composed of reinforced fibers and matrix resin, and has high specific strength and low-density materials. Because of the orientation of the fibers within them, FRPs are prone to buckling damage when under compression along the axial direction of the fiber, especially flexible organic ones. The compressive performance of FRP is largely dependent on fiber properties. the buckling load of FRP will increase with the increasing of fiber's. In this study, we developed a way to improve the compressive and bending strength of ultra-high molecular weight polyethylene (UHMWPE) fibers. Carbon nanotubes (CNTs) and vapor-grown carbon fibers (VGCFs) were coated on the surface of UHMWPE fibers by pyrrole vapor deposition. The transverse compressive strength and bending strength of single UHMWPE fibers were determined by microcompression and single fiber bending measurements, respectively. The experiment result showed that coating UHMWPE fibers with CNTs and VGCFs increased both their transverse compressive strength and bending strength. It is excepted that the improved fiber would applied in FRP for better compressive performance.ArticleFIBERS AND POLYMERS. 15(4):723-728 (2014)journal articl