Ultra-high Performance Concrete Columns Research Articles

Eccentrically compressed behavior of UHPC columns considering the P-delta effect

Eccentric compression is a critical behavior observed in arches and columns, particularly in structures constructed with ultra-high performance concrete (UHPC). Compared to normal concrete structures, those made with UHPC exhibit distinct behaviors that need to be clearly investigated. This study comprehensively investigates UHPC columns under eccentric compression load through experimental study and theoretical analysis. Various experimental parameters, including slenderness ratio, eccentricity distance, fiber content, and stirrup ratio, were examined across 26 UHPC columns. Failure modes were evaluated using digital image correlation (DIC) methods. The load-displacement responses indicated that slender columns subjected to significant eccentricity exhibited load decreases during yielding stages, whereas short columns experienced load increases. This discrepancy in yielding stages was attributed to P-delta effects. In addition, theoretical models were developed to determine the ultimate bearing capacity of columns experiencing compression-controlled and tension-controlled failures, considering the P-delta effect caused by the different slenderness ratios. The moment magnifying coefficients for UHPC were calibrated based on theoretical analyses of the limit curvature of eccentric compression members. The proposed theoretical models agreed well with the experimental results, with an average ratio of 1.02. The second-order effect for the case of UHPC short column with a slenderness ratio of 5 can be ignored as per Eurocode 2, which is less than 10 % of the corresponding first-order effect.

Comparative impact behaviours of ultra high performance concrete columns reinforced with polypropylene vs steel fibres

Polypropylene (PP) fibres have primarily used to control shrinkage cracks or mitigate explosive spalling in concrete structures exposed to fire or subjected to impact/blast loads, with limited investigations on capacity improvement. This study unveils the possibility of using PP micro-fibres to improve the impact behaviour of fibre-reinforced ultra-high-performance concrete (FRUHPC) columns. Results show that the addition of fibres significantly improves the impact behaviour of FRUHPC columns by shifting the failure mechanism from brittle shear to favourable flexural failure. The addition of steel or PP fibres affected the impact responses differently. Steel fibres considerably increased the peak impact force (up to 18%) while PP micro-fibres slightly increased the peak (3%–4%). FRUHPC significantly reduced the maximum mid-height displacement by up to 30% (under 20° impact) and substantially improved the displacement recovery by up to 100% (under 20° impact). FRUHPC with steel fibres significantly improved the energy absorption while those with PP micro-fibres reduced the energy absorption, which is different from the effect of PP-macro fibre reported in the literature. The optimal fibre content for micro-PP fibres is 1% due to its minimal fibre usage and low peak and residual displacement. This study highlights the potential of FRUHPC as a promising material for impact-resistant structures by creating a more favourable flexural failure mechanism, enhancing ductility and toughness under impact loading, and advancing the understanding of the role of fibres in structural performance.

Slenderness limit for reinforced ultra-high-performance concrete columns

The use of ultra-high-performance concrete (UHPC) allows for much smaller cross-sections compared to conventional reinforced concrete columns, which may make reinforced UHPC (R-UHPC) columns more susceptible to slenderness effects. Currently, there is no guideline in design standards for the slenderness limit of R-UHPC columns. This paper, therefore, attempts to develop a design provision for determining the slenderness limit of R-UHPC columns. Firstly, a numerical analytical model was proposed for predicting the load-deflection of R-UHPC columns under eccentric loading, which was validated by comparing its predictions with available experimental results from the available literature. Based on the validated model, a parametric study was then conducted to determine the key parameters affecting the slenderness limit of R-UHPC columns. It was found that the slenderness limit corresponding to the 5% strength reduction was sensitive to the ultimate compressive strain of UHPC, the tensile strength of UHPC, and the reinforcement ratio. On this basis, a design equation for the slenderness limit of R-UHPC columns in single curvature was statistically derived. Additionally, the slenderness limit for R-UHPC columns in non-sway frames was also proposed in a convenient form for design procedures.

Experimental and theoretical study on seismic behavior of a new UHPFRC sandwich wall and wall-wall joint

A new type of precast ultra-high performance concrete (UHPFRC) sandwich wall is proposed in this study. The proposed UHPFRC sandwich wall is composed of the UHPFRC layers, extruded polystyrene foam (XPS) board layer, and short UHPFRC columns connecting the UHPFRC layers. Compared with the traditional reinforced concrete wall, the UHPFRC sandwich wall possesses lower self-weight, less reinforcement, and higher strength. In addition, two types of wall-wall vertical joint connection methods, flexible cable connection and embedded steel plate welding connection, are proposed. The pseudo-static tests on five UHPFRC sandwich wall specimens were conducted to study the effects of UHPFRC layer thickness, reinforcement ratio, and width of edge solid area on the seismic behavior of the wall. Then, the seismic performance of different connection methods was studied by pseudo-static tests on two T-shaped UHPFRC sandwich wall-wall joint specimens. Test results demonstrate that the unreinforced UHPFRC sandwich wall, with 20–30 mm UHPFRC thickness and 150 mm edge solid area, showed excellent cracking resistance and seismic behavior. The cracking loads are more than 50% of the peak loads, and the bottom shear capacity to self-weight ratios are generally more than 35. The seismic behavior of the wall-wall joints connected by the flexible cable and embedded steel plate welding are both reliable. Finally, formulas for cracking and peak load of the UHPFRC sandwich wall are proposed and the fiber model is developed for analysis of the wall-wall joint, which is verified by the test results to be accurate and reasonable.

A review study on axial compression properties of UHPC columns confined by FRP

The failure of ultra-high performance concrete (UHPC) under axial compression has significant brittleness, so it is necessary to use fiber reinforced polymer (FRP) to constrain UHPC for achieving ductile failure. This article mainly summarized the research progress of FRP constrained UHPC columns, analyzed the influence of different variables on the compressive performance of FRP-confined UHPC columns and the coupling effect between variables, compared the axial compressive stress-strain models of FRP-confined UHPC columns proposed by previous scholars, and evaluated the existing models using a large amount of collected experimental data. The evaluation results indicated that the existing models provided relatively accurate predictions for ultimate stress, but further improvement and correction are needed for predicting ultimate strain. Based on the data collected in this study, the models had been modified, resulting in improved accuracy in predicting both ultimate stress and ultimate strain.

Research on Steel Reinforced Stainless Steel Tube Ultra High Performance Concrete Columns

Research on Steel Reinforced Stainless Steel Tube Ultra High Performance Concrete Columns

Continuous surface cap model for ultra-high-performance concrete under static and low strain rate loadings: Calibration, experiment, and simulation

The ultra-high compressive strength and ductile tensile behavior of ultra-high-performance concrete (UHPC) make it promising in the application of civil and crashworthy facilities. Although numerous experimental studies have been conducted to investigate the performance of UHPC, studies on the methods for simulating the behavior of UHPC are few. In this paper, an overview of widely used constitutive models of concrete-like materials in hydrocode was presented first, and then a comprehensive calibration of the continuous cap surface (CSC) model was performed to simulate the mechanical behavior of UHPC under static and low strain rate loadings. Four groups of parameters: (1) failure surface parameters; (2) cap and hardening parameters; (c) damage parameters; and (4) strain rate parameters were systematically calibrated via extensive available material test data of UHPC with uniaxial compressive strength ranging from 101 MPa to 238 MPa. A calculation method was proposed to address the inconsistency of existing conclusions regarding the fracture energy of UHPC, which significantly affects the modeling of UHPC damage. Moreover, a method was proposed to convert the engineering uniaxial tensile strain of UHPC to the true uniaxial tensile strain, and so does the tensile fracture energy of UHPC. To validate the accuracy of the calibrated CSC model in simulating the behavior of UHPC under static loading, uniaxial tension and compression tests of UHPC samples and three-point bending tests of steel-UHPC-steel composite beams were conducted and simulated. Existing triaxial compression tests of UHPC cylinders were simulated to validate the accuracy of the calibrated CSC under confinement. Moreover, low-velocity impact tests of UHPC columns were simulated to further validate the reliability of the calibrated CSC model to capture the structural behavior of UHPC members under low strain rate loading. It was found that the calibrated CSC model showed excellence in simulating the material properties of UHPC and the structural behavior of UHPC members under static and low strain rate loadings.

Strength prediction and stochastic analysis of ultra-high performance concrete columns under the explosive blast load

The performance research based on numerical and experimental studies on ultra-high performance concrete (UHPC) generally considers it as an isotropic material, which is obviously different from what it really is in practical engineering. A database of UHPC compressive strength was investigated, having the same UHPC mix proportion as the field blast experiment, to show how the strength of UHPC varies in compression. It is found that Weibull distribution is the best fit of its probability model. A combination of Monte-Carlo and Finite Element method is used, adopting the available UHPC compressive strength, to reproduce the field blast test on UHPC columns. Both the non-spatial and spatial variability of material properties of the UHPC columns are under consideration to conduct the UHPC column strength prediction under blast loads. The residual loading capacity, damage index and failure mode of UHPC columns with different sizes damaged by different explosion severities are obtained by non-spatial simulation and spatial simulation respectively. It can be concluded that compared with the non-spatial model, the numerical simulation results of the spatial model are closer to the experimental situation. Therefore, inclusion of spatial variability is recommended for reliability-based blast-resistant design for UHPC column.

Experimental Study and Numerical Analysis of the Seismic Performance of Glass-Fiber Reinforced Plastic Tube Ultra-High Performance Concrete Composite Columns.

To investigate the impact of the filament winding angle of glass-fiber reinforced plastic (GFRP) on the seismic behavior of GFRP tube ultra-high performance concrete (UHPC) composite columns, this study designs two types of GFRP tube UHPC composite columns. Quasi-static tests are conducted on the specimens subjected to horizontal reciprocating load and axial force, and the skeleton curve characteristics of the structure are analyzed. Furthermore, a finite element analysis model of the composite column is established to explore the effects of the diameter-thickness ratio, circumferential elastic modulus of confined tubes, and tensile strength of concrete on the seismic performance of the composite column. The analysis includes a review of the skeleton curve, energy dissipation capacity, and stiffness degradation of the structure under different designs. The results indicate that the use of GFRP tubes effectively enhances the seismic performance of UHPC columns. The failure mode, peak load, and peak displacement of the composite columns are improved. The finite element analysis results are in good agreement with the experimental results, validating the effectiveness of the analysis model. Extended analysis reveals that the bearing capacity of the specimen increases while the energy dissipation capacity decreases with a decrease in the diameter-thickness ratio and an increase in the circumferential elastic modulus. Although the tensile strength of concrete has some influence on the seismic performance of the specimen, its effect is relatively small. Through regression analysis, a formula for shear capacity suitable for GFRP tube UHPC composite columns is proposed. This formula provides a theoretical reference for the design and engineering practice of GFRP tube UHPC composite columns.

Compression performance of FRP-steel composite tube-confined ultrahigh-performance concrete (UHPC) columns

A new ultrahigh-performance concrete (UHPC)-filled fibre-reinforced polymer (FRP)-steel composite tube column (UHPCFSCT) was designed. This structure uses not only UHPC with high strength and durability to reduce the section size and improve the stiffness of the column but also FRP–steel composite tubes as confinement tubes to reduce the brittleness of the UHPC. Thirty-two UHPCFSCTs were subjected to monotonic axial compression tests. The key parameters include the number of FRP layers, FRP type, FRP hybrid condition and loading mode. The full-section-loaded specimens mainly exhibit shear failure, while the core-loaded specimens mainly exhibit middle expansion deformation. The stress–strain curves of UHPCFSCTs represent three types of columns with different numbers of FRP layers and FRP types: columns with weak, medium and strong confinements. The weak and medium confinement curves exhibit a softening section after the elastic–plastic stage, and the strong confinement curve shows a bilinear response. With the increase in the number of FRP layers, compared with those of the unconfined UHPC column, the ratios of the increases in peak stress, ultimate stress, and ultimate strain are 1.436∼2.794, 2.046∼4.822 and 0.778∼2.315, respectively. The bearing capacity of the CFRP-confined specimens is stronger, while the deformation capacity of the BFRP-confined specimens is stronger. The ultimate stresses of the core-loaded specimens are 19.6%∼30.6% higher than those of the full-section-loaded specimens. Existing strength models were used to evaluate the test data of UHPCFSCTs, and the Hu et al. model was used to predict the strength of UHPCFSCTs under core loading. Finally, through database regression analysis, a strength model that can be used to predict steel tube-confined UHPC, FRP-confined UHPC and UHPCFSCT strength under full-section loading was proposed.

Data-driven ultimate condition prediction of UHPC columns subjected lateral confinement using Artificial Neural Network (ANN) approach

Despite the superior mechanical properties of Ultra-High Performance Concrete (UHPC) in comparison to conventional concrete, UHPC is still not widely used in the construction industry due to the lack of design standards. This research mainly focuses on using advanced computational tools for the prediction of ultimate stress and its corresponding strain for confined UHPC columns, to facilitate the process of analysis and design, and to support further development of standards. Characteristic parameters of confined UHPC column samples were extracted from available literature as the input, and the corresponding ultimate stress and strain as the output. Artificial Neural Network (ANN) technique was adopted to process the input parameters in order to train and predict the output. In the regression analysis, the trained networks exhibited the coefficients of determination (R2) of 0.995 and 0.964 for the prediction of ultimate stress and corresponding strain respectively. The weights and biases within the best performance ANN from the k-fold cross validation can be extracted to perform mathematical solutions for the prediction in design.

Seismic behavior of ultra-high performance concrete columns with GFRP bars under different loading directions

The combination of ultra-high performance concrete (UHPC) and glass fiber reinforced polymer (GFRP) bars offers a promising and viable design option for future infrastructure in the extremely harsh environment. However, studies carried out on this kind of structure are rather limited, especially for its seismic behavior under non-principal bending. This paper presents an experimental program on eight columns (four UHPC-GFRP hybrid columns, three UHPC columns and one reinforced concrete column) tested under lateral displacements with loading angles of 0° and 45°. Other changes of interest include types of concrete, types of reinforcement, and longitudinal reinforcement ratios. The seismic responses of specimens were discussed and analyzed in detail from various aspects, including cracking patterns, failure modes, hysteretic responses, and strain profiles. The experiment results reveal that the introduction of GFRP bars is effective in restricting the development of cracks while having limited negative influence on the seismic performance of UHPC columns, demonstrating the practicability of the UHPC-GFRP hybrid column. Furthermore, in contrast to reinforced concrete columns, it has been observed that UHPC specimens exhibit a low sensitivity to the direction of lateral loading with regard to cracking patterns and energy dissipation capacity.

Experimental investigation on seismic behavior of Ultra-high performance concrete columns reinforced with GFRP bars

Owing to its outstanding mechanical and structural properties, ultra-high performance concrete (UHPC) has triggered rapidly increasing interest among both construction industry and research community. Numerous studies have been conducted at the structural level to explore the benefits brought by UHPC. Nonetheless, currently there is hardly any published studies on the seismic performance of UHPC columns reinforced with glass fiber reinforced polymer (GFRP) bars. This paper presents an experimental campaign carried out on seven UHPC columns subjected to simulated seismic loading. The variables include the type of reinforcement, the type of concrete, the cross-sectional area, and the transverse reinforcement. The seismic performance of specimens was thoroughly assessed in terms of cracking patterns, failure modes, hysteretic responses and strain profiles. The results show that specimens cast with UHPC have superior seismic performance, especially in terms of lateral load capacity and energy dissipation capacity. Moreover, it is found that the adoption of GFRP bars effectively prevents the formation of cracks while having limited adverse impacts on the seismic performance of UHPC columns. Therefore, the hybrid of UHPC and GFRP bars provides a new design opportunity for columns in a harsh environment.

Behavior of UHPC columns confined by high-strength transverse reinforcement under eccentric compression

This paper presents the experimental and analytical studies on the compressive behavior of ultra-high performance concrete (UHPC) columns confined by high-strength transverse reinforcement under eccentric compression. Nine columns including test variables of spacing, strength and arrangement type of transverse reinforcements, steel fiber content and eccentricity were tested to analyze the load-lateral deflection behavior, failure modes and carrying capacity. The experiment results showed that the deformation capacity, peak load and residual carrying capacity of UHPC columns confined by high-strength transverse reinforcement under eccentric loading were significantly better than those of ordinary-strength transverse reinforcement. Reducing the spacing of transverse reinforcement and increasing the volume fraction of steel fiber could also improve the ductility and carrying capacity of UHPC columns. Then, a mesoscale model was proposed to characterize the tensile behavior of UHPC which considered the fiber inclination, fiber-matrix interface bonding and fiber embedded length. Based on the proposed tensile model, a simplified method for calculating the carrying capacity of UHPC columns under large eccentric compression was developed, where the tensile behavior of UHPC and the confinement effect of transverse reinforcements were considered. The errors between the theoretical and test values were within 10%, indicating that this method can be used to guide the design of UHPC columns.

A numerical study of blast resistance of fire damaged ultra-high performance concrete columns

Concrete structures may experience fire and blast during their service life as a result of accidental explosions or vehicular collisions. Both fire and blast can cause severe damage that threatens the structural safety. In the present study, reinforced concrete columns fabricated by ultra-high performance concrete (UHPC) are investigated under coupled fire and blast loads. Strength degradation and damage of UHPC and steel reinforcement after exposure to elevated temperature (up to 800 °C) were established based on the experimental data. In addition to the detrimental effect on individual material, bond-slip behaviour between the UHPC and reinforcement affected by the elevated temperature was considered. The findings revealed that material strength degradation and damage owing to elevated temperature significantly influenced the structural blast resistance, and the degraded bond-slip behaviour had varying impact on the structural response depending on the structural damage mode. Up to 10% mid-span displacement differences were noted in columns with/without the consideration of bond-slip behaviour. Different failure mechanisms pre- and post-fire damage were observed in the numerical simulations. To quickly assess blast induced damage on UHPC columns, Pressure-Impulse (P-I) diagrams of the UHPC columns before and after elevated temperature were established and empirical formulae were proposed to generate the P-I diagrams.

Influence of Tie Configuration on Seismic Behaviour of Ultra High Performance Concrete Columns

Ultra-High-Performance Concrete (UHPC) is one of the latest advances in concrete technology as it overcomes the shortcomings of conventional concrete such as low strength to weight ratio, high permeability, low tensile strength, low ductility, and volume instability. Confinement is capable of increasing capacity of the concrete structure to sustain large deformation without a substantial strength loss. The present study discusses the influence of tie configuration, percentage of longitudinal reinforcement and tie spacing in improving the confinement and behaviour of UHPC columns. In order to determine the behaviour of UHPC column, half scaled specimens of original short column with four different tie configurations were used. The configurations considered for the study included a double legged ties (A), welded ties with bars running centrally across the length and width (B), ties with inclined bars connecting two adjacent mid-points (C) and ties with bars connecting two adjacent sides at one-third distances (D). For the same tie configuration, the transverse reinforcement ratios are varied by changing the diameter of the ties. The specimens were tested under quasi static reverse cyclic loading under a constant axial load. The test results were represented and compared in terms of load-deflection envelope, ductility and cracking patterns. Tie configuration C exhibited better performance in stiffness and ductility, when compared with other configurations. For same parameters, “B” and “D” configuration displayed better behaviour than “A” configuration. This variation in performance was due to increase in transverse reinforcement percentage and the consequent effectiveness of core confinement. Transverse reinforcement percentage of “B” and “C” configurations is less than “D” configuration. The enhancements of properties of “B” and “C” configurations are better than “D” configuration. It was due to the effective core confinement of “B” and “C” configuration. For the same tie configuration, ultimate load, initial stiffness and relative ductility increases with increase in transverse reinforcement percentage. UHPC columns with “C” type tie configuration can effectively use in moderate and high seismic areas and its performance can be improved by increasing the transverse reinforcement ratio.

Prediction of ultimate conditions and stress–strain behaviour of steel-confined ultra-high-performance concrete using sequential deep feed-forward neural network modelling strategy

Recognising that ultra-high-performance concrete (UHPC) is gaining momentum in structural applications, providing an accurate confinement model is essential to developing a reliable design of UHPC structural members. However, very limited number of models are currently available and these models were empirically formulated and calibrated upon limited test data obtained by the originators of the models. The significant cost associated with comprehensive experimental testing motivates the exploration of cheaper and more efficient data-driven based machine learning approach. This study proposes a sequential artificial neural network (ANN) framework to develop such a data-driven confinement model, incorporating a comprehensive database of 228 axially loaded UHPC columns compiled from available literature. Three deep feed-forward neural network models were established to predict the ultimate stress, ultimate strain and stress–strain behaviour of confined UHPC. The results show that the proposed ANN-based ultimate condition models provide a more robust prediction results compared to the existing design-oriented models for confined UHPC. The stress–strain behaviour, predicted using the proposed ANN model, shows high accuracy levels in capturing different types of stress–strain curves as well as reasonably matching results with those experimentally measured responses. The encouraging outcomes in this study suggest that the proposed models are capable of providing rapid prediction tools that will help to facilitate the on-demand design of UHPC structural components and systems.

Strain-path-dependent stress–strain model for ultrahigh-performance concrete columns constrained by stirrups

The incorporation of steel fibers improves the microscopic ductility of ultrahigh-performance concrete (UHPC) materials, and their macroscopic ductility can also be improved by the restraining effect of composite stirrups. Two defects can be found in the stress–strain model of UHPC restrained by stirrups based on the design-oriented method: the restraint coefficient of the stirrup is the effective restraint coefficient at the peak state of the specimen, while the variation in the restraint stress of the stirrup with the axial–hoop strain relationship (strain path) is ignored. In this study, a strain-path-dependent stress–strain model for UHPC constrained by stirrups and fibers is proposed through a database with 10 sets of test results on UHPC columns, which alleviates the shortcomings of the design-oriented model. (1) On the basis of the axial–hoop strain relationship curve in the test results, an axial–hoop strain model of UHPC restrained by stirrups is established. (2) The variation in the restraint stress of the stirrup with strain path is considered. (3) On the basis of the stress–strain model of actively constrained concrete, an iterative method of subsections is adopted, and a UHPC stress–strain model restrained by stirrup based on strain path is established. Results show that the established axial–hoop strain equation can better predict the hoop strain of UHPC restrained by stirrups and steel fibers, the calculated value of peak stress of UHPC constrained by stirrups based on strain path is in good agreement with the test results, and the outcomes of the path-dependent stress–strain model are in better agreement with the experimental results than those of the design-oriented stress–strain model.

Axial compressive behavior of concrete-filled steel tubes with GFRP-confined UHPC cores

The steel–concrete-GFRP-UHPC (SCGU) composite column is a new type of column consisting of steel, concrete, ultra-high performance concrete (UHPC) and glass fiber reinforced polymer (GFRP). The sectional form of the SCGU column is a circular steel tube as the outer layer, a GFRP-wrapped UHPC column as the core, and concrete between the core column and the steel tube. In this paper, axial compression tests were conducted on twenty-four SCGU composite columns, and their damage morphology, load–strain curves and influencing factors were analyzed. The results show that the damage modes of the specimens present multiple convex curves of the external steel tube, corresponding to the fragmentation of its plain internal concrete, the fracture of GFRP and the large axial crack of the UHPC core column; that the load–displacement curves of the composite columns can be roughly simplified to elastic, elastoplastic and plastic flow stages; that the composite columns still have high residual bearing capacity after compression damage; and that effect of tube thickness, number of GFRP layers and UHPC core column diameter of the specimen on the load bearing capacity and ductility of composite columns. Based on the mechanical analysis of each component of the SCGU composite column, a formula of axial compression bearing capacity of the SCGU composite column was presented, and agreement between the formula predicted results and the experimental results was obtained. In addition, finite element (FE) models that can simulate the SCGU composite column are developed.

Compressive behavior and strength prediction of ultra-high performance concrete confined by normal and high strength steel hoops

Ultra-high performance concrete (UHPC) confined by steel hoops exhibits obvious performance advantages under high temperature or corrosive environment compared with the external steel or fiber-reinforced polymer (FRP) jackets, due to protection to the confinement component by UHPC cover. However, some fundamental knowledge gaps need to be filled to promote the application of this type of composite column, including the compressive behavior of UHPC confined by high-strength steel hoops, influence of UHPC cover on the axial load carrying capacity as well as lack of acceptable strength model for predicting the load carrying capacity of steel hoop-confined UHPC column. Therefore, a series of axial compression tests on 78 UHPC stub columns confined by normal- and high-strength steel hoops were tested, with varying lateral confining levels and thicknesses of UHPC cove. The experimental results show that using high-strength steel hoops as lateral confining component can more effectively improve the post-peak behavior of confined UHPC column than its ascending behavior, compared with the UHPC confined by normal-strength hoops. The UHPC cover can directly carry a considerable share of peak axial load, thus cannot be ignored for evaluating the load carrying capacity of the confined UHPC column. A special strength model is proposed for UHPC columns confined by normal- and high-strength steel hoops to predict the axial load carrying capacity, and it is validated with experimental data derived from this investigation and opened literature.