An Algorithm for Optimal Bipartite PLA Folding

This paper presents some results of PLA area optimizing by means of its column and row folding. A more restricted type of PLA simple folding is considered. It is introduced by Egan and Liu and called as bipartite folding. An efficient approach is presented which allows finding an optimal bipartite folding without exhaustive computational efforts.

Recovery of glass fibre and carbon fibres from reinforced thermosets by batch pyrolysis and investigation of fibre re-using as reinforcement in LDPE matrix

A semi-batch pyrolysis process was used to recover samples carbon fibre and glass fibre from their respective wastes. The mechanical properties of the recovered fibres were tested and compared to those of virgin fibres, showing good retention of the fibre properties. The recovered fibres were then used to prepare new LDPE composite materials with commercial and laboratory-synthesized compatibilizers. Mild oxidation of the post-pyrolysis recovered fibres and the use of different compatibilizers gave significant improvements in the mechanical properties of the LDPE composites; however some of the manufactured composites made from recovered fibres had properties similar to those made from virgin fibres.

An in vitro comparison of the incorporation, growth, and chondrogenic potential of human bone marrow versus adipose tissue mesenchymal stem cells in clinically relevant cell scaffolds used for cartilage repair

Aim. To compare the incorporation, growth, and chondrogenic potential of bone marrow (BM) and adipose tissue (AT) mesenchymal stem cells (MSCs) in scaffolds used for cartilage repair. Methods. Human BM and AT MSCs were isolated, culture expanded, and characterised using standard protocols, then seeded into 2 different scaffolds, Chondro-Gide or Alpha Chondro Shield. Cell adhesion, incorporation, and viable cell growth were assessed microscopically and following calcein AM/ethidium homodimer (Live/Dead) staining. Cell-seeded scaffolds were treated with chondrogenic inducers for 28 days. Extracellular matrix deposition and soluble glycosaminoglycan (GAG) release into the culture medium was measured at day 28 by histology/immunohistochemistry and dimethylmethylene blue assay, respectively. Results. A greater number of viable MSCs from either source adhered and incorporated into Chondro-Gide than into Alpha Chondro Shield. In both cell scaffolds, this incorporation represented less than 2% of the cells that were seeded. There was a marked proliferation of BM MSCs, but not AT MSCs, in Chondro-Gide. MSCs from both sources underwent chondrogenic differentiation following induction. However, cartilaginous extracellular matrix deposition was most marked in Chondro- Gide seeded with BM MSCs. Soluble GAG secretion increased in chondrogenic versus control conditions. There was no marked difference in GAG secretion by MSCs from either cell source. Conclusion. Chondro-Gide and Alpha Chondro Shield were permissive to the incorporation and chondrogenic differentiation of human BM and AT MSCs. Chondro-Gide seeded with BM MSCs demonstrated the greatest increase in MSC number and deposition of a cartilaginous tissue.

An investigation of primary human cell sources and clinical scaffolds for articular cartilage repair

Damage to articular cartilage of the knee can be debilitating because it lacks the capacity to repair itself and can progress to degenerative disorders such as osteoarthritis. The current gold standard for treating cartilage defects is autologous chondrocyte implantation (ACI). However, one of the major limitations of ACI is the use of chondrocytes, which dedifferentiate when grown in vitro and lose their phenotype. It is not clear whether the dedifferentiated chondrocytes can fully redifferentiate upon in vivo transplantation. Studies have suggested that undifferentiated mesenchymal stem or stromal cells (MSCs) from bone marrow (BM) and adipose tissue (AT) can undergo chondrogenic differentiation. Therefore, the main aim of this thesis was to examine BM and AT as a cell source for chondrogenesis using clinical scaffolds. Initially, freshly isolated cells were compared with culture expanded MSCs from BM and AT in Chondro-Gide®, Alpha Chondro Shield® and Hyalofast™. MSCs were shown to grow better in the three scaffolds compared to freshly isolated cells. BM MSCs in Chondro-Gide® were shown to have increased deposition of cartilage specific extracellular matrix (ECM) compared to AT MSCs. Further, this thesis has sought to examine whether CD271 selected MSCs from AT were more chondrogenic than MSCs selected on the basis of plastic adherence (PA). It was shown that CD271+MSCs may have superior chondrogenic properties in vitro and in vivo in terms of ECM deposition. The repair tissue seen after CD271+MSC transplantation combined with Alpha Chondro Shield® was also less vascularised than that seen after transplantation with PA MSCs in the same scaffold, suggesting antiangiogenic activity. Since articular cartilage is an avascular tissue, CD271+MSCs may be a better suited cell type compared to the PA MSCs. Hence, this study has increased the current understanding of how different cell-scaffold combinations may best be used to promote articular cartilage repair.

Carbon nanotube reinforced aluminum based nanocomposite fabricated by thermal spray forming

The present research concentrates on the fabrication of bulk aluminum matrix nanocomposite structures with carbon nanotube reinforcement. The objective of the work was to fabricate and characterize multi-walled carbon nanotube (MWCNT) reinforced hypereutectic Al-Si (23 wt% Si, 2 wt% Ni, 1 wt% Cu, rest Al) nanocomposite bulk structure with nanocrystalline matrix through thermal spray forming techniques viz. plasma spray forming (PSF) and high velocity oxy-fuel (HVOF) spray forming. This is the first research study, which has shown that thermal spray forming can be successfully used to synthesize carbon nanotube reinforced nanocomposites. Microstructural characterization based on quantitative microscopy, scanning and transmission electron microscopy (SEM and TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy and X ray photoelectron spectroscopy (XPS) confirms (i) retention and macro/sub-macro level homogenous distribution of multiwalled carbon nanotubes in the Al-Si matrix and (ii) evolution of nanostructured grains in the matrix. Formation of ultrathin β-SiC layer on MWCNT surface, due to chemical reaction of Si atoms diffusing from Al-Si alloy and C atoms from the outer walls of MWCNTs has been confirmed theoretically and experimentally. The presence of SiC layer at the interface improves the wettability and the interfacial adhesion between the MWCNT reinforcement and the Al-Si matrix. Sintering of the as-sprayed nanocomposites was carried out in an inert environment for further densification. As-sprayed PSF nanocomposite showed lower microhardness compared to HVOF, due to the higher porosity content and lower residual stress. The hardness of the nanocomposites increased with sintering time due to effective pore removal. Uniaxial tensile test on CNT-bulk nanocomposite was carried out, which is the first ever study of such nature. The tensile test results showed inconsistency in the data attributed to inhomogeneous microstructure and limitation of the test samples geometry. The elastic moduli of nanocomposites were computed using different micromechanics models and compared with experimentally measured values. The elastic moduli of nanocomposites measured by nanoindentation technique, increased gradually with sintering attributed to porosity removal. The experimentally measured values conformed better with theoretically predicted values, particularly in the case of Hashin-Shtrikman bound method.

Development of surface flaw thresholds for pre-cured fiber reinforced polymer and groove size tolerance for near surface mounted fiber reinforced polymer retrofit systems

Since the introduction of fiber reinforced polymers (FRP) for the repair and retrofit of concrete structures in the 1980’s, considerable research has been devoted to the feasibility of their application and predictive modeling of their performance. However, the effects of flaws present in the constitutive components and the practices in substrate preparation and treatment have not yet been thoroughly studied. This research aims at investigating the effect of surface preparation and treatment for the pre-cured FRP systems and the groove size tolerance for near surface mounted (NSM) FRP systems; and to set thresholds for guaranteed system performance. This study was conducted as part of the National Cooperative Highway Research Program (NCHRP) Project 10-59B to develop construction specifications and process control manual for repair and retrofit of concrete structures using bonded FRP systems. The research included both analytical and experimental components. The experimental program for the pre-cured FRP systems consisted of a total of twenty-four (24) reinforced concrete (RC) T-beams with various surface preparation parameters and surface flaws, including roughness, flatness, voids and cracks (cuts). For the NSM FRP systems, a total of twelve (12) additional RC T-beams were tested with different grooves sizes for FRP bars and strips. The analytical program included developing an elaborate nonlinear finite element model using the general purpose software ANSYS. The bond interface between FRP and concrete was modeled by a series of nonlinear springs. The model was validated against test data from the present study as well as those available from the literature. The model was subsequently used to extend the experimental range of parameters for surface flatness in pre-cured FRP systems and for groove size study in the NSM FRP systems. Test results, confirmed by further analyses, indicated that contrary to the general belief in the industry, the impact of surface roughness on the global performance of pre-cured FRP systems was negligible. The study also verified that threshold limits set for wet lay-up FRP systems can be extended to pre-cured systems. The study showed that larger surface voids and cracks (cuts) can adversely impact both the strength and ductility of pre-cured FRP systems. On the other hand, frequency (or spacing) of surface cracks (cuts) may only affect system ductility rather than its strength. Finally, within the range studied, groove size tolerance of ±1/8 in. does not appear to have an adverse effect on the performance of NSM FRP systems.

Seismic performance of hybrid fiber reinforced polymer-concrete pier frame systems

As an alternative to transverse spiral or hoop steel reinforcement, fiber reinforced polymers (FRPs) were introduced to the construction industry in the 1980’s. The concept of concrete-filled FRP tube (CFFT) has raised great interest amongst researchers in the last decade. FRP tube can act as a pour form, protective jacket, and shear and flexural reinforcement for concrete. However, seismic performance of CFFT bridge substructure has not yet been fully investigated. Experimental work in this study included four two-column bent tests, several component tests and coupon tests. Four 1/6-scale bridge pier frames, consisting of a control reinforced concrete frame (RCF), glass FRP-concrete frame (GFF), carbon FRP-concrete frame (CFF), and hybrid glass/carbon FRP-concrete frame (HFF) were tested under reverse cyclic lateral loading with constant axial loads. Specimen GFF did not show any sign of cracking at a drift ratio as high as 15% with considerable loading capacity, whereas Specimen CFF showed that lowest ductility with similar load capacity as in Specimen GFF. FRP-concrete columns and pier cap beams were then cut from the pier frame specimens, and were tested again in three point flexure under monotonic loading with no axial load. The tests indicated that bonding between FRP and concrete and yielding of steel both affect the flexural strength and ductility of the components. The coupon tests were carried out to establish the tensile strength and elastic modulus of each FRP tube and the FRP mold for the pier cap beam in the two principle directions of loading. A nonlinear analytical model was developed to predict the load-deflection responses of the pier frames. The model was validated against test results. Subsequently, a parametric study was conducted with variables such as frame height to span ratio, steel reinforcement ratio, FRP tube thickness, axial force, and compressive strength of concrete. A typical bridge was also simulated under three different ground acceleration records and damping ratios. Based on the analytical damage index, the RCF bridge was most severely damaged, whereas the GFF bridge only suffered minor repairable damages. Damping ratio was shown to have a pronounced effect on FRP-concrete bridges, just the same as in conventional bridges. This research was part of a multi-university project, which is founded by the National Science Foundation (NSF) - Network for Earthquake Engineering Simulation Research (NEESR) program.

Aerodynamic load characteristics evaluation and tri-axial performance testing on fiber reinforced polymer connections and metal fasteners to promote hurricane damage mitigation

Damages during extreme wind events highlight the weaknesses of mechanical fasteners at the roof-to-wall connections in residential timber frame buildings. The allowable capacity of the metal fasteners is based on results of unidirectional component testing that do not simulate realistic tri-axial aerodynamic loading effects. The first objective of this research was to simulate hurricane effects and study hurricane-structure interaction at full-scale, facilitating better understanding of the combined impacts of wind, rain, and debris on inter-component connections at spatial and temporal scales. The second objective was to evaluate the performance of a non-intrusive roof-to-wall connection system using fiber reinforced polymer (FRP) materials and compare its load capacity to the capacity of an existing metal fastener under simulated aerodynamic loads. ^ The Wall of Wind (WoW) testing performed using FRP connections on a one-story gable-roof timber structure instrumented with a variety of sensors, was used to create a database on aerodynamic and aero-hydrodynamic loading on roof-to-wall connections tested under several parameters: angles of attack, wind-turbulence content, internal pressure conditions, with and without effects of rain. Based on the aerodynamic loading results obtained from WoW tests, sets of three force components (tri-axial mean loads) were combined into a series of resultant mean forces, which were used to test the FRP and metal connections in the structures laboratory up to failure. A new component testing system and test protocol were developed for testing fasteners under simulated triaxial loading as opposed to uni-axial loading. The tri-axial and uni-axial test results were compared for hurricane clips. Also, comparison was made between tri-axial load capacity of FRP and metal connections. ^ The research findings demonstrate that the FRP connection is a viable option for use in timber roof-to-wall connection system. Findings also confirm that current testing methods of mechanical fasteners tend to overestimate the actual load capacities of a connector. Additionally, the research also contributes to the development a new testing protocol for fasteners using tri-axial simultaneous loads based on the aerodynamic database obtained from the WoW testing. ^

Seismic performance of hybrid fiber reinforced polymer-concrete pier columns

As part of a multi-university research program funded by NSF, a comprehensive experimental and analytical study of seismic behavior of hybrid fiber reinforced polymer (FRP)-concrete column is presented in this dissertation. Experimental investigation includes cyclic tests of six large-scale concrete-filled FRP tube (CFFT) and RC columns followed by monotonic flexural tests, a nondestructive evaluation of damage using ultrasonic pulse velocity in between the two test sets and tension tests of sixty-five FRP coupons. Two analytical models using ANSYS and OpenSees were developed and favorably verified against both cyclic and monotonic flexural tests. The results of the two methods were compared. A parametric study was also carried out to investigate the effect of three main parameters on primary seismic response measures. The responses of typical CFFT columns to three representative earthquake records were also investigated. The study shows that only specimens with carbon FRP cracked, whereas specimens with glass or hybrid FRP did not show any visible cracks throughout cyclic tests. Further monotonic flexural tests showed that carbon specimens both experienced flexural cracks in tension and crumpling in compression. Glass or hybrid specimens, on the other hand, all showed local buckling of FRP tubes. Compared with conventional RC columns, CFFT column possesses higher flexural strength and energy dissipation with an extended plastic hinge region. Among all CFFT columns, the hybrid lay-up demonstrated the highest flexural strength and initial stiffness, mainly because of its high reinforcement index and FRP/concrete stiffness ratio, respectively. Moreover, at the same drift ratio, the hybrid lay-up was also considered as the best in term of energy dissipation. Specimens with glassfiber tubes, on the other hand, exhibited the highest ductility due to better flexibility of glass FRP composites. Furthermore, ductility of CFFTs showed a strong correlation with the rupture strain of FRP. Parametric study further showed that different FRP architecture and rebar types may lead to different failure modes for CFFT columns. Transient analysis of strong ground motions showed that the column with off-axis nonlinear filament-wound glass FRP tube exhibited a superior seismic performance to all other CFFTs. Moreover, higher FRP reinforcement ratios may lead to a brittle system failure, while a well-engineered FRP reinforcement configuration may significantly enhance the seismic performance of CFFT columns.

Novel hybrid columns made of ultra-high performance concrete and fiber reinforced polymers

The application of advanced materials in infrastructure has grown rapidly in recent years mainly because of their potential to ease the construction, extend the service life, and improve the performance of structures. Ultra-high performance concrete (UHPC) is one such material considered as a novel alternative to conventional concrete. The material microstructure in UHPC is optimized to significantly improve its material properties including compressive and tensile strength, modulus of elasticity, durability, and damage tolerance. Fiber-reinforced polymer (FRP) composite is another novel construction material with excellent properties such as high strength-to-weight and stiffness-to-weight ratios and good corrosion resistance. Considering the exceptional properties of UHPC and FRP, many advantages can result from the combined application of these two advanced materials, which is the subject of this research. The confinement behavior of UHPC was studied for the first time in this research. The stress-strain behavior of a series of UHPC-filled fiber-reinforced polymer (FRP) tubes with different fiber types and thicknesses were tested under uniaxial compression. The FRP confinement was shown to significantly enhance both the ultimate strength and strain of UHPC. It was also shown that existing confinement models are incapable of predicting the behavior of FRP-confined UHPC. Therefore, new stress-strain models for FRP-confined UHPC were developed through an analytical study. In the other part of this research, a novel steel-free UHPC-filled FRP tube (UHPCFFT) column system was developed and its cyclic behavior was studied. The proposed steel-free UHPCFFT column showed much higher strength and stiffness, with a reasonable ductility, as compared to its conventional reinforced concrete (RC) counterpart. Using the results of the first phase of column tests, a second series of UHPCFFT columns were made and studied under pseudo-static loading to study the effect of column parameters on the cyclic behavior of UHPCFFT columns. Strong correlations were noted between the initial stiffness and the stiffness index, and between the moment capacity and the reinforcement index. Finally, a thorough analytical study was carried out to investigate the seismic response of the proposed steel-free UHPCFFT columns, which showed their superior earthquake resistance, as compared to their RC counterparts.

An analytical investigation into shear wall and slab interconnections between reinforced concrete modules for high -rise buildings utilising modular construction under extreme seismic and wind loading

This research investigates a new structural system utilising modular construction. Five-sided boxes are cast on-site and stacked together to form a building. An analytical model was created of a typical building in each of two different analysis programs utilising the finite element method (Robot Millennium and ETABS). The pros and cons of both Robot Millennium and ETABS are listed at several key stages in the development of an analytical model utilising this structural system. Robot Millennium was initially utilised but created an analytical model too large to be successfully run. The computation requirements were too large for conventional computers. Therefore Robot Millennium was abandoned in favour of ETABS, whose more simplistic algorithms and assumptions permitted running this large computation model. Tips are provided as well as pitfalls signalled throughout the process of modelling such complex buildings of this type. ^ The building under high seismic loading required a new horizontal shear mechanism. This dissertation has proposed to create a secondary floor that ties to the modular box through the use of gunwales, and roughened surfaces with epoxy coatings. In addition, vertical connections necessitated a new type of shear wall. These shear walls consisted of waffled external walls tied through both reinforcement and a secondary concrete pour. ^ This structural system has generated a new building which was found to be very rigid compared to a conventional structure. The proposed modular building exhibited a period of 1.27 seconds, which is about one-fifth of a conventional building. The maximum lateral drift occurs under seismic loading with a magnitude of 6.14 inches which is one-quarter of a conventional building's drift. The deflected shape and pattern of the interstorey drifts are consistent with those of a coupled shear wall building. In conclusion, the computer analysis indicate that this new structure exceeds current code requirements for both hurricane winds and high seismic loads, and concomitantly provides a shortened construction time with reduced funding. ^

Development of thresholds for surface preparation in repair systems with wet lay -up fiber reinforced polymers

Bonded repair of concrete structures with fiber reinforced polymer (FRP) systems is increasingly being accepted as a cost-efficient and structurally viable method of rapid rehabilitation of concrete structures. However, the relationships between long-term performance attributes, service-life, and details of the installation process are not easy to quantify. Accordingly, there is currently a lack of generally accepted construction specifications, making it difficult for the field engineer to certify the adequacy of the construction process. ^ The objective of the present study, as part of the National Cooperative Highway Research Program (NCHRP) Project 10-59B, was to investigate the effect of surface preparation on the behavior of wet lay-up FRP repair systems and consequently develop rational thresholds that provide sufficient performance. ^ The research program was comprised of both experimental and analytical work for wet lay-up FRP applications. The experimental work included flexure testing of sixty-seven (67) reinforced concrete beams and bond testing of ten (10) reinforced concrete blocks. Four different parameters were studied: surface roughness, surface flatness, surface voids and bug holes, and surface cracks/cuts. The findings were analyzed from various aspects and compared with the data available in the literature. As part of the analytical work, finite element models of the flexural specimens with surface flaws were developed using ANSYS. The purpose of this part was to extend the parametric study on the effects of concrete surface flaws and verify the experimental results based on nonlinear finite element analysis. ^ Test results showed that surface roughness does not appear to have a significant influence on the overall performance of the wet lay-up FRP systems with or without adequate anchorage, and whether failure was by debonding or rupture of FRP. Both experimental and analytical results for surface flatness proved that peaks on concrete surface, in the range studied, do not have a significant effect on the performance of wet lay-up FRP systems. However, valleys of particular size could reduce the strength of wet lay-up FRP systems. Test results regarding surface voids and surface cracks/cuts revealed that previously suggested thresholds for these flaws appear to be conservative, as also confirmed by analytical study. ^

Fiber Scaffolds of Poly (glycerol-dodecanedioate) and its Derivative via Electrospinning for Neural Tissue Engineering

Peripheral nerves have demonstrated the ability to bridge gaps of up to 6 mm. Peripheral Nerve System injury sites beyond this range need autograft or allograft surgery. Central Nerve System cells do not allow spontaneous regeneration due to the intrinsic environmental inhibition. Although stem cell therapy seems to be a promising approach towards nerve repair, it is essential to use the distinct three-dimensional architecture of a cell scaffold with proper biomolecule embedding in order to ensure that the local environment can be controlled well enough for growth and survival. Many approaches have been developed for the fabrication of 3D scaffolds, and more recently, fiber-based scaffolds produced via the electrospinning have been garnering increasing interest, as it offers the opportunity for control over fiber composition, as well as fiber mesh porosity using a relatively simple experimental setup. All these attributes make electrospun fibers a new class of promising scaffolds for neural tissue engineering. Therefore, the purpose of this doctoral study is to investigate the use of the novel material PGD and its derivative PGDF for obtaining fiber scaffolds using the electrospinning. The performance of these scaffolds, combined with neural lineage cells derived from ESCs, was evaluated by the dissolvability test, Raman spectroscopy, cell viability assay, real time PCR, Immunocytochemistry, extracellular electrophysiology, etc. The newly designed collector makes it possible to easily obtain fibers with adequate length and integrity. The utilization of a solvent like ethanol and water for electrospinning of fibrous scaffolds provides a potentially less toxic and more biocompatible fabrication method. Cell viability testing demonstrated that the addition of gelatin leads to significant improvement of cell proliferation on the scaffolds. Both real time PCR and Immunocytochemistry analysis indicated that motor neuron differentiation was achieved through the high motor neuron gene expression using the metabolites approach. The addition of Fumaric acid into fiber scaffolds further promoted the differentiation. Based on the results, this newly fabricated electrospun fiber scaffold, combined with neural lineage cells, provides a potential alternate strategy for nerve injury repair.

Development of Surface Flaw Thresholds for Pre-Cured Fiber Reinforced Polymer and Groove Size Tolerance for Near Surface Mounted Fiber Reinforced Polymer Retrofit Systems

Since the introduction of fiber reinforced polymers (FRP) for the repair and retrofit of concrete structures in the 1980’s, considerable research has been devoted to the feasibility of their application and predictive modeling of their performance. However, the effects of flaws present in the constitutive components and the practices in substrate preparation and treatment have not yet been thoroughly studied. This research aims at investigating the effect of surface preparation and treatment for the pre-cured FRP systems and the groove size tolerance for near surface mounted (NSM) FRP systems; and to set thresholds for guaranteed system performance. The research included both analytical and experimental components. The experimental program for the pre-cured FRP systems consisted of a total of twenty-four (24) reinforced concrete (RC) T-beams with various surface preparation parameters and surface flaws, including roughness, flatness, voids and cracks (cuts). For the NSM FRP systems, a total of twelve (12) additional RC T-beams were tested with different grooves sizes for FRP bars and strips. The analytical program included developing an elaborate nonlinear finite element model using the general purpose software ANSYS. The model was subsequently used to extend the experimental range of parameters for surface flatness in pre-cured FRP systems, and for groove size study in the NSM FRP systems. Test results, confirmed by further analyses, indicated that contrary to the general belief in the industry, the impact of surface roughness on the global performance of pre-cured FRP systems was negligible. The study also verified that threshold limits set for wet lay-up FRP systems can be extended to pre-cured systems. The study showed that larger surface voids and cracks (cuts) can adversely impact both the strength and ductility of pre-cured FRP systems. On the other hand, frequency (or spacing) of surface cracks (cuts) may only affect system ductility rather than its strength. Finally, within the range studied, groove size tolerance of +1/8 in. does not appear to have an adverse effect on the performance of NSM FRP systems.

Seismic Performance of Hybrid Fiber Reinforced Polymer-Concrete Pier Columns

As part of a multi-university research program funded by NSF, a comprehensive experimental and analytical study of seismic behavior of hybrid fiber reinforced polymer (FRP)-concrete column is presented in this dissertation. Experimental investigation includes cyclic tests of six large-scale concrete-filled FRP tube (CFFT) and RC columns followed by monotonic flexural tests, a nondestructive evaluation of damage using ultrasonic pulse velocity in between the two test sets and tension tests of sixty-five FRP coupons. Two analytical models using ANSYS and OpenSees were developed and favorably verified against both cyclic and monotonic flexural tests. The results of the two methods were compared. A parametric study was also carried out to investigate the effect of three main parameters on primary seismic response measures. The responses of typical CFFT columns to three representative earthquake records were also investigated. The study shows that only specimens with carbon FRP cracked, whereas specimens with glass or hybrid FRP did not show any visible cracks throughout cyclic tests. Further monotonic flexural tests showed that carbon specimens both experienced flexural cracks in tension and crumpling in compression. Glass or hybrid specimens, on the other hand, all showed local buckling of FRP tubes. Compared with conventional RC columns, CFFT column possesses higher flexural strength and energy dissipation with an extended plastic hinge region. Among all CFFT columns, the hybrid lay-up demonstrated the highest flexural strength and initial stiffness, mainly because of its high reinforcement index and FRP/concrete stiffness ratio, respectively. Moreover, at the same drift ratio, the hybrid lay-up was also considered as the best in term of energy dissipation. Specimens with glassfiber tubes, on the other hand, exhibited the highest ductility due to better flexibility of glass FRP composites. Furthermore, ductility of CFFTs showed a strong correlation with the rupture strain of FRP. Parametric study further showed that different FRP architecture and rebar types may lead to different failure modes for CFFT columns. Transient analysis of strong ground motions showed that the column with off-axis nonlinear filament-wound glass FRP tube exhibited a superior seismic performance to all other CFFTs. Moreover, higher FRP reinforcement ratios may lead to a brittle system failure, while a well-engineered FRP reinforcement configuration may significantly enhance the seismic performance of CFFT columns.