Dilational Properties Research Articles

Interfacial dilatational and emulsifying properties of ultrasound-treated pea protein

In this study, the structural, interfacial, and emulsifying properties of high-intensity ultrasound (HUS)-treated pea protein isolate (PPIUS) were investigated. HUS at 50% amplitude and 57–60 W·cm−2 for 5 min markedly improved protein solubility (by 132%), surface hydrophobicity (by 173%), and reduced particle size (by 52%). These physicochemical changes in PPIUS led to more rapid protein adsorption at the oil–water interface, improved emulsifying activity (by 18–27%) and capacity (by 11%), and enhanced emulsion physical stability. The multilayer nature, albeit less elastic, of the interfacial membrane formed by PPIUS when compared to control protein (PPIC), based on dilatational testing, contributed to the above results. Moreover, PPIUS-stabilized emulsions exhibited a tendency of being less susceptible to lipid oxidation during storage. Thus, structure-modifying HUS may be a valuable processing technology for the manufacture of pea protein-based emulsion foods.

Surface Dilatational Properties and Foam Performance of Surfactant-Nanoparticle Foaming System under Ultra-High Salinity

Abstract We have studied the surface dilatational properties of aqueous foaming dispersions containing mixtures of silica nanoparticles (Ludox CL) and sulfobetaine (LHSB) in Tahe formation water. The effects of temperature and pH on the surface dilatational modulus and time shift were studied by oscillating drop module (ODM). The ODM results show that the surface dilatational modulus of mixtures of CL and LHSB is large and increases with the decrease of surface area deformation, which results from hydrophobic interaction between adsorbed mixtures. Under test conditions, the Gibbs stability criterion E > σ/2 against foam coarsening is fulfilled. Results of Brewster angle microscopy (BAM) show that an uniform adsorption layer is established at the air-water interface. Temperature and pH-value influence the dilatation modulus of the surface by hydrophobic interaction or adsorption. Time shift has a similar variation trend. This is a surprising feature. It suggests that LHSB adsorbed on CL can respond to surface tension gradient. The time shift difference results from the response of LHSB at different adsorption sites. In addition, sand pack tests show that compared to LHSB, a finer foam was produced by the mixtures CL/LHSB due to the capillary-induced \snap-off". Thus, higher pressure difference and higher oil recovery could be achieved.

Elastoplastic Constitutive Model Describing Dilatancy Behavior of Overconsolidated Clay

Abstract Overconsolidated (OC) clay has a strong dilatancy property, which has a significant effect on ultimate strength and deformation. Compared with normal consolidated (NC) clay, OC clay tends ...

Features of the flow of concentrated suspensions of solid particles

Concentrated suspensions of solids, widely used in the pharmaceutical, cosmetic and food industries, exhibit complex rheology. In the rheometric one-dimensional flows of concentrated suspensions, a smooth or abrupt increase in stresses with a smooth increase in the strain rate intensity can be observed. This is related to the appearance of a first-order phase transition. In our previous work, a phenomenological rheological model of a concentrated suspension of solid particles in a Newtonian dispersion liquid has been developed. This model is characterized by an S-shaped flow curve and describes both continuous and abrupt increases in the stress intensity with a uniform increase in the strain rate intensity. In this work, exact analytical formulas are obtained for the flow velocity profiles of suspensions measured using rotary viscometers. The model proposed before is modified to take into account the non-Newtonian properties of the dispersion medium, which demonstrates pseudoplastic properties at low stress intensities and dilatant properties at high stress intensities. Based on the developed numerical model, the features of the flow of highly concentrated suspensions in plane and axisymmetric channels are analyzed. It is shown that in a flat diffuser, in contrast to Newtonian and pseudoplastic fluids, the longitudinal velocity of the suspension slows down near the walls, where the stresses are maximum, and accelerates in the central part of the channel. Calculations for the submerged jet in the area bounded by the walls show that, with an increase in the average velocity of the incoming pure liquid by more than 0.01 m/s, there occurs a local velocity vortex bounded by a layer with high particle concentration and more viscous medium; particle concentration inside the vortex is minimum.

Dilatational rheology of water-in-diesel fuel interfaces: effect of surfactant concentration and bulk-to-interface exchange.

Micrometer-sized water droplets dispersed in diesel fuel are stabilized by the fuel's surface-active additives, such as mono-olein and poly(isobutylene)succinimide (PIBSI), making the droplets challenging for coalescing filters to separate. Dynamic material properties found from interfacial rheology are known to influence the behavior of microscale droplets in coalescing filters. In this work, we study the interfacial dilatational properties of water-in-fuel interfaces laden with mono-olein and PIBSI, with a fuel phase of clay-treated ultra-low sulphur diesel (CT ULSD). First, the dynamic interfacial tension (IFT) is measured using pendant drop tensiometry, and a curvature-dependent form of the Ward and Tordai diffusion equation is applied for extracting the diffusivity of the surfactants. Additionally, Langmuir kinetics are applied to the dynamic IFT results to obtain the maximum surface concentration (Γ∞) and ratio of adsorption to desorption rate constants (κ). We then use a capillary pressure microtensiometer to measure the interfacial dilatational modulus, and further extract the characteristic frequency of surfactant exchange (ω0) by fitting a model assuming diffusive exchange between the interface and bulk. In this measurement, 50-100 μm diameter water droplets are pinned at the tip of a glass capillary in contact with the surfactant-containing fuel phase, and small amplitude capillary pressure oscillations over a range of frequencies from 0.45-20 rad s-1 are applied to the interface, inducing changes in interfacial tension and area to yield the dilatational modulus, E*(ω). Over the range of concentrations studied, the dilatational modulus of CT ULSD with either mono-olein or PIBSI increases with a decrease in bulk concentration and plateaus at the lowest concentrations of mono-olein. Characteristic frequency (ω0) values extracted from the fit are compared with those calculated using equilibrium surfactant parameters (κ and Γ∞) derived from pendant drop tensiometry, and good agreement is found between these values. Importantly, the results imply that diffusive exchange models based on the equilibrium relationships between surfactant concentration and interfacial tension can be used to infer the dynamic dilatational behavior of complex surfactant systems, such as the water-in-diesel fuel interfaces in this study.

Rheo-morphological investigation of Reynolds dilatancy and its effect on pumpability of self-consolidating concrete

Reynolds dilatancy is one of the main mechanisms responsible for the lubrication layer (LL) formation during pumping of self-consolidating concrete (SCC). In this study, the effect of morphological characteristics of coarse aggregate on Reynolds dilatancy of 30 different SCC mixtures was investigated. The Reynolds dilatancy measurements were carried out using a coaxial-cylinders tribometer. New methodology to evaluate the morphology of coarse aggregate using 3D image analysis was also proposed. The Reynolds dilatancy values of the investigated SCC mixture were well correlated to both the morphological characteristics of coarse aggregate (>1.25 mm) and visco-elastoplastic properties of the suspending fine mortar (<1.25 mm). The established correlations revealed that higher 3D surface area and roughness, as well as lower mean diameter and elongation of coarse aggregate can lead to higher Reynolds dilatancy.Moreover, the thickness, composition and rheological properties of the LL, as well as the rheological properties of the investigated SCC mixtures were successfully evaluated using the Reynolds dilatancy and morphological measurements. The pumpability of the investigated SCC mixtures were then predicted using the estimated rheological properties of the investigated mixtures and their corresponding LL. The results showed that higher Reynold dilatancy and lower rheological properties of SCC can decrease the pressure loss and facilitate the pumping process. Moreover, the pumpability of SCC was found to be more controlled by the volume of cement paste, concentration, and packing density of coarse aggregate.

Effect of pH on okara protein-carboxymethyl cellulose interactions in aqueous solution and at oil-water interface

The physicochemical and interfacial properties of Okara protein (OP) are susceptible to be affected by various factors. In this respect, the role of inter- and intramolecular interactions between OP and carboxymethyl cellulose (CMC) were explored by in situ experiments. OP/CMC aqueous mixtures, containing 1.0 wt% OP and 0–0.5 wt% CMC, were prepared at pH 7.0 and 4.0. Subsequently, their physicochemical properties, interactions, and interfacial adsorption were comparatively characterized. OP formed larger aggregates at lower pH as confirmed by the visual appearance. The addition of CMC reduced the surface hydrophobicity and increased viscosity of OP/CMC mixtures regardless of pH. CMC increased the hydrodynamic diameter of mixtures at pH 7.0, while it led to more negatively-charged complexes with decreasing size at pH 4.0. Noticeably, the results regarding the interfacial pressure, adsorption kinetics and interfacial dilatational viscoelastic properties presented three remarkable phenomena: Low concentrations of CMC hardly affected the initial interfacial performance of OP at pH 7.0, whereas the latter was greatly reduced at high CMC concentrations. Moreover, high CMC concentrations appropriately reinforced the interfacial performance of OP at pH 4.0.

Assessing the Interfacial Activity of Insoluble Asphaltene Layers: Interfacial Rheology versus Interfacial Tension

Asphaltenes have been suggested to play an important role in the remarkable stability of some water-in-crude oil emulsions, although the precise mechanisms by which they act are not yet fully understood. Being one of the more polar fractions in crude oils, asphaltenes are surface active and strongly adsorb at the oil/water interface, and as the interface becomes densely packed, solid-like mechanical properties emerge, which influence many typical interfacial experiments. The present work focuses on purposefully measuring the rheology in the limit of an insoluble, spread Langmuir monolayer in the absence of adsorption/desorption phenomena. Moreover, the changes in surface tension are deconvoluted from the purely mechanical contribution to the surface stress by experiments with precise interfacial kinematics. Compression "isotherms" are combined with the measurement of both shear and dilatational rheological properties to evaluate the relative contributions of mechanical versus thermodynamic aspects, i.e., to evaluate the "interfacial rheological" versus the standard interfacial activity. The experimental results suggest that asphaltene nanoaggregates are not very efficient in lowering interfacial tension but rather impart significant mechanical stresses. Interestingly, physical aging effects are not observed in the spread layers, contrary to results for adsorbed layers. By further studying asphaltene fractions of different polarity, we investigate whether mere packing effects or strong interactions determine the mechanical response of the dense asphaltene systems as either soft glassy or gel-like responses have been reported. The compressional and rheological data reflect the dense packing, and the behavior is captured well by the soft glassy rheology model, but a more complicated multilayer structure may develop as coverage is increased. Potential implications of the experimental observations on these model and insoluble interfaces for water-in-crude oil emulsion stability are briefly discussed.

Impact of Adsorption Layer Properties on Drainage Behavior of Microscopic Foam Films: The Case of Cationic/Nonionic Surfactant Mixtures

Aqueous mixtures of cationic hexadecyltrimethylammonium chloride (CTAC) and nonionic pentaethyleneglycol monododecyl ether (C12E5) are investigated. Adsorption layer properties are systematically studied within a wide concentration range for a 1:1 molar ratio of the surfactants. Surface tension and dilatational rheology measurements are conducted by profile analysis tensiometry. The interfacial data are juxtaposed to drainage kinetics and stability results for microscopic foam films, investigated by microinterferometric thin liquid film instrumentation. The obtained results give experimental evidence of synergistic interactions in the studied solutions, as compared to the corresponding single surfactant systems. Specific runs of dynamic and equilibrium surface tension curves are registered against the total surfactant quantity; the surface dilatational elasticities for the mixtures are systematically higher. A clear correlation is established between adsorption layer performance and foam film characteristics. The maxima of the film lifetimes are well outlined, and the respective values are shifted towards lower overall concentrations. The reported results substantiate the key role of the adsorption layers, and the surface dilatational properties in particular, for foam film drainage kinetics and stability. The well-expressed synergy observed in adsorption layer and foam film properties suggests the substantial benefits of using mixed surfactant systems in the design and fine-tuning of foam systems for innovative applications.

Lignosulfonates in Crude Oil Processing: Interactions with Asphaltenes at the Oil/Water Interface and Screening of Potential Applications.

The goal of this article is to test the potential application of lignosulfonates (LSs) in crude oil production and processing. Three LS samples of varying hydrophobicity and average molecular weight were considered. First, the interfacial tension between brine and xylene and interfacial dilational rheology properties of LS samples were measured. It was found that the most surface-active LS sample has the lowest molecular weight in agreement with the results from the literature. In the presence of asphaltenes, all three LS samples were able to compete with asphaltenes, the most polar crude oil component, at the interface and form mixed LS–asphaltene interfaces. However, only the most surface-active LS sample among the three tested could fully desorb asphaltenes at the highest tested LS concentration (500 ppm). Second, three possible applications were screened. LSs were tested to prevent the formation of w/o crude oil emulsions or to break these. However, the opposite effect was observed, that is, stabilization of water-in-crude oil emulsions. The potential application of LS in produced water (PW) clarification was furthermore considered. The kinetics of PW clarification was found unaffected by the presence of LS, even at very high concentrations (1000 ppm). Finally, the potential of LS for enhanced oil recovery was assessed. The LS flood changed the surface wettability toward water wetness for one of the samples, yet LS injection did not recover additional oil beyond brine recovery. It was concluded that LS has interesting properties, such as the potential to compete with crude oil indigenous components at the oil/water interface. The stabilization action of LS was dominant over any destabilization effect, which led to the conclusion that LSs are more efficient for stabilizing emulsions rather than destabilizing.

Emulsion stability and dilatational rheological properties of soy/whey protein isolate complexes at the oil-water interface: Influence of pH

The effects of pH (2.0–11.0) on the interaction of soy protein isolate (SPI) and whey protein isolate (WPI) at the oil-water interface and the stability of SPI-WPI emulsions were studied by analyzing their interfacial tension, dilatational and steady-state rheological behaviors, particle size, and creaming stability. Within a pH range of 2.0–8.0, the SPI-WPI emulsions were very viscous, exhibiting extensive droplet flocculation (3405.00 ± 202.40 nm at pH 4.0) and poor creaming stability (73.58 ± 0.94% at pH 4.0), thereby indicating an unstable emulsion. The enhanced viscoelasticity and decreased interface pressure between SPI and WPI at the interface indicated a fine interface behavior. This behavior may be due to the strong electrostatic attraction interaction between the SPI and WPI at the interface. This co-adsorption at the interface increases the amount of adsorbed proteins, leading to increased viscoelasticity of the emulsion. However, at pH 8.0 to 11.0, the weaker droplet flocculation (288.50 ± 0.26 nm at pH 11.0) and fine creaming stability (no stratification) indicated that a stable emulsion was formed. This may be attributed to electrostatic repulsion between the SPI and WPI at a pH above the isoelectric point (pI) of the proteins, which inhibits droplet flocculation. This study offers a basis for the selection of pH treatment of SPI-WPI composite emulsions with different stabilities and rheological behaviors, as well as a potential application for bioactive compound delivery systems.

Noncommutative maximal ergodic inequalities associated with doubling conditions

In this paper, we establish the one-sided maximal ergodic inequalities for a large subclass of positive operators on noncommutative $L_p$-spaces for a fixed $1<p<\infty$, which particularly applies to positive isometries and general positive Lamperti contractions or power bounded doubly Lamperti operators; moreover, it is known that this subclass recovers all positive contractions on the classical Lebesgue spaces $L_p([0,1])$. Our study falls into neither the category of positive contractions considered by Junge-Xu nor the class of power bounded positive invertible operators considered by Hong-Liao-Wang. Our strategy essentially relies on various structural characterizations and dilation properties associated with Lamperti operators, which are of independent interest. More precisely, we give a structural description of Lamperti operators in the noncommutative setting, and obtain a simultaneous dilation theorem for Lamperti contractions. As a consequence we establish the maximal ergodic theorem for the strong closure of the convex hull of corresponding family of positive contractions. Moreover, in conjunction with a newly-built structural theorem, we also obtain the maximal ergodic inequalities for positive power bounded doubly Lamperti operators. We also observe that the concrete examples of positive contractions without Akcoglu's dilation, which were constructed by Junge-Le Merdy, still satisfy the maximal ergodic inequalities. We also discuss some other examples, showing sharp contrast to the classical situation.

Dynamics of interfacial layers for sodium dodecylbenzene sulfonate solutions at different salinities

This study investigates the adsorption mechanisms and the dilational surface rheology of the anionic surfactant sodium dodecylbenzene sulfonate (SDBS) at the air–liquid interface, in the presence and absence of NaCl over a wide range of SDBS concentrations. We also evaluate the Langmuir and Frumkin models in order to predict the dynamic adsorption of SDBS solutions. Our results reveal that the equilibrium surface tension of SDBS solutions is a monotonically decreasing function of NaCl concentration. However, the dilational viscoelastic properties of SDBS solutions are found to be a non-monotonic function of NaCl concentration. NaCl manifests opposing effects on the dilational viscoelastic moduli of the gas–liquid interface, depending on the frequency of surface oscillation and surfactant bulk concentration. Our measured dilational surface elasticity and viscosity data show a shift in the surfactant transition concentration, at which the viscoelastic moduli reach their maximum values, towards smaller surfactant bulk concentrations with increasing salt concentration. It is attributed to suppressing the electrostatic repulsion between the hydrophilic head groups of surfactant molecules in the presence of electrolytes. The maximum viscoelastic moduli at different NaCl concentrations is found to be the reflection of the relative impact of enhanced adsorption and increased diffusion exchange between bulk and interface.

Emulsification and dilatational surface rheology of ultrasonicated milk fat globule membrane (MFGM) materials

Herein milk fat model emulsions (MFMEs) of infant formulas were prepared with ultrasonication-processed milk fat globule membrane (MFGM) materials (as well as MFGM/Lecithin blend and lecithin). The emulsion stability during storage was determined with a turbiscan. The microstructure of MFMEs was examined with confocal laser scanning microscopy (CLSM) at different pH values. Besides, the adsorption kinetics and linear/nonlinear dilatational rheological properties of oil/water interfaces were measured with a droplet tensiometer. After ultrasonication process, the average particle size of MFGM fragments decreased from 800 ± 100 nm to 230 ± 10 nm. The surface tension (at 100 s) of MFGM-stabilized interfaces was 17.4 mN/m (0.5 g/L), 12.9 mN/m (1.0 g/L and 2.0 g/L) and 11.0 mN/m (4.0 g/L), indicating a good emulsifying capacity of ultrasonicated MFGM materials. At neutral and acidic pH, MFMEs stabilized with MFGM dispersions or MFGM/Lecithin (1:1) at a total concentration of 4.0 g/L showed strong resistance against coalescence (CLSM). MFGM dispersions exhibited different surface rheological behaviour from pure phospholipids, proteins or a simple phospholipid/protein mixture, which suggested a heterogeneous structure of MFGM-stabilized interfaces, mainly consisting of MFGM fragment particles, interspersed with free phospholipids and proteins. These findings could provide a better understanding of emulsifying properties of MFGM materials.

Interfacial interactions between oleic acid and betaine molecules at decane-water interface: A study of dilational rheology

The interfacial interactions between organic acid and betaine molecules play an important role in reducing interfacial tension (IFT). To deeply detect the arrangements of organic acid and betaine molecules at the interface, the dilational rheological properties of mixed adsorption films formed by oleic acid and octadecyl carboxyl betaine (18PC) or octadecyl sulfobetaine (18PS) were investigated using drop shape analysis method at the decane-water interface. The influences of aging time, oscillation frequency and surfactants concentration were detected. The experimental results show that the properties of 18PC and 18PS adsorption film are controlled by both the fast diffusion-exchange process between the bulk and the interface and the slow re-arrangement process in the interface. 18PC film is tighter than that of 18PS because the size of carboxyl is small than sulfonyl. Oleic acid and betaine surfactants can form mixed adsorption films with less strength caused by the rapid transfer of oleic acid between the bulk and the interface, but more elastic due to the enhancement of the intermolecular interaction. In this case, the oleic acid molecules are easier to insert into the spaces between 18PS molecules on the interface, which results in a more tight mixed film than oleic acid/18PC film.

Dynamic surface properties and dilational rheology of acidic and lactonic sophorolipids at the air-water interface

This study analyzes the equilibrium and dynamic surface tension curves of acidic and lactonic sophorolipids (SLs). It also investigates the dilational properties of the surface adsorptive film. Given their high hydrophobicity, lactonic SLs have lower surface tension and critical micelle concentration (CMC) than acidic SLs. As cNaCl increases, the CMC values and the corresponding surface tension (γcmc) of acidic and lactonic SLs decrease gradually. For dynamic surface properties, lactonic SLs have a high diffusive rate from the bulk phase to the subsurface. At 0.05 CMC, the initial adsorption of acidic and lactonic SLs is diffusion-controlled. As csurfactant increases, the values of diffusion coefficient (D) show a downward trend, and the mechanism is mixed kinetic diffusion. Adding NaCl increases the D values of acidic and lactonic SLs, and the influence degree for acidic SLs is more considerable than that for lactonic SLs.As frequency (ω) increases (0.005∼0.5 Hz), the dilational elasticity increases, and the phase angle decrease. The dilational elasticity of acidic and lactonic SLs shows a low-frequency dependence. Compared with acidic SLs, lactonic SLs have better dynamic surface properties, which decrease the gradient of interfacial tension because of the interface deformation. Consequently, the lactonic SLs exhibit a relatively small dilational elasticity. At 0.1 Hz, the dilational elasticity of acidic and lactonic SLs reaches the maximum values at 0.05CMC and 0.075CMC, respectively. When csurfactant rises near CMC, the phase angle increases obviously, and the dilational elasticity further decreases. This result is attributed to the fast exchange of surfactant molecules between the interface and the micelles.

Adsorption properties of N-tetradecyl-N,N-dimethyl-N-(2,3-epoxy propyl) ammonium chloride with inorganic salts at air/water

A series of N-alkyl-N,N-dimethyl-N-(2,3-epoxy propyl) ammonium chloride (C n EAC, n = 10, 12, 14, 16) with alkyl of decyl, dodecyl, tetradecyl, and hexadecyl were synthesized. The adsorption properties of C n EAC under the different temperatures, concentrations, interfacial oscillation frequencies as well as the inorganic salts (NaCl and Na2CO3) at air/water interface were investigated by interfacial dilatational rheology. The dilatational properties of C n EAC solutions including complex moduli, elastic moduli and viscosity moduli increased with oscillation frequency. The elastic moduli were higher than those of viscosity ones. With different hydrogen carbon length, the complex moduli of C n EAC showed different changing role with their concentration and temperature. Inorganic salts compressed the oppositely charges on C n EAC micelle surface and induced the decrease of both complex and viscosity moduli.

Soy glycinin-soyasaponin mixtures at oil–water interface: Interfacial behavior and O/W emulsion stability

Soy glycinin (11S) was mixed with soyasaponin (Ssa) to elucidate the mechanism(s) involved in the stabilization of emulsions by mixed systems based on dynamic interfacial tension and dilatational rheology at the oil–water interface. The short/long-term properties of oil-in-water emulsions stabilized by 11S–Ssa mixtures included droplet-size distribution, droplet ζ-potential, microstructure, and Turbiscan stability index. The combination of Ssa (0.05%) with 11S significantly affected the interfacial dilatational and emulsion properties although the interfacial properties were still dominated by the protein. Higher concentrations (0.1% and 0.2%) of Ssa combined with 11S synergistically decreased the interfacial tension, which was attributed to the interaction between 11S and Ssa. Using high Ssa concentrations (0.25%–0.5%) enhanced the long-term stability of emulsions (in response to external deformations) after 42 d. These results will aid the basic understanding of protein–Ssa interfacial adsorption during emulsion formation and can help prepare natural food additives for designing emulsions.

Surface and foaming properties of potato proteins: Impact of protein concentration, pH value and ionic strength

Using a multiscale approach, potato protein isolate was characterized holistically in terms of its solubility and surface charge, surface activity and surface dilatational properties as well foaming properties and bubble structural attributes. By means of varying protein concentration (0.1–10.0%), pH (3.0–10.0) and NaCl concentration (0–200 mM), it was aimed to establish a better mechanistic understanding of potato protein functionality. Overall, surface activity was found to be rather unaffected by a modification of protein concentration and pH, whereas pH had a clear effect on surface dilatational elasticity. Likewise, foam stability was affected by pH, yielding a maximum around the isoelectric point, which is due to an enhanced network formation at the air/water interface imparting an increased surface film stability. Coarsening exponents were found to reflect the results on foam stability. By comparison, NaCl presence clearly had an enhancing effect on surface activity and led to increased protein-protein interactions within the surface film. More compact surface films in turn resulted in a better foamability and foam stability as well as lower coarsening exponents. Comparison of findings to mechanisms known for β-lactoglobulin-stabilized surfaces revealed their principal applicability also to potato proteins’ functional properties. Overall, by means of the obtained knowledge, foam structures based on potato proteins can be controlled more specifically.

Axial compressive behavior of partially CFRP confined seawater sea-sand concrete in circular columns – Part II: A new analysis-oriented model

For the comprehensive analysis of the mechanical performance of concrete structures wrapped with partial FRP strips, the development of an accurate and versatile axial stress-strain model is of significant importance. No research, however, has been conducted to present a satisfactory analysis-oriented stress-strain model for partially FRP confined concrete. To this end, this paper firstly investigates the performance of several existing analysis-oriented models in assessing the FRP partially wrapped columns. The results show that all selected models cannot provide reasonable predictions for the test specimens, especially for the specimens possessing strain-softening stress-strain relationships. Therefore, the dilation properties and the peak axial strength expressions of active-confinement base models were both revised based on the test observations and a new analysis-oriented model was proposed for partially FRP confined concrete. Finally, a large database of CFRP partially wrapped columns was assembled through an extensive literature review to evaluate the accuracy of models. By comparing the test results with the predicted calculations, the proposed model can provide accurate and reasonable predictions both for the ultimate conditions and the complete axial stress-strain relationships, which were obviously superior to the other existing models.