Published Test Data Research Articles

Analysis of Saturated Impulse for Square Plates under Flat Slamming Impact: Experimental and Numerical Investigation

The saturated impulse is a special phenomenon in the dynamic plastic behavior of engineering structures under intensive pulse loading, such as slamming loading. In this study, slamming experiments were performed on steel plates to investigate their slamming pressure and dynamic plastic responses, as well as the saturation phenomenon, and elucidate the effect of the plate thickness and material properties on the dimensionless saturated deflection and saturated impulse in combination with the published test data. The results show that the dimensionless saturated deflection and saturated impulse of the test plates gradually increased as the dimensionless stiffness decreased. After being validated against the experimental results, a numerical method that considered the fluid–structure interaction (FSI) effect was then employed to provide comprehensive insight into the transient plastic responses and saturated impulse of the flat plates under slamming impact. Numerical simulations revealed that the compressed air layer always existed during the effective process of the flat slamming impact. Through the numerical prediction of the dynamic plastic deflection and slamming pulse loading, it was observed that the saturated impulse phenomenon always took place after the time instant of the peak value of the pressure pulse. Furthermore, the analysis of the saturated impulse based on the numerical simulations indicated that the saturation phenomenon was more likely to be achieved as the water impact velocity increased.

Theoretical investigation on elastic property evolutions of low volume fly ash concrete

AbstractToward expanding the application of fly ash in cement‐based materials, this study proposes a comprehensive study on predicting the elastic properties of low‐volume fly ash concrete, with the replacement levels limited to 30% or less. Unlike conventional ordinary Portland cement concrete, the inclusion of fly ash in concrete brings alterations in properties from both chemical and physical perspectives: (1) the presence of fly ash liberates the alkaline solution that consumes calcium hydroxide to generate secondary calcium silicate hydrate gels; (2) unreacted fly ash particles exhibits a refinement effect on the micropore structure and contributes to forming a denser solid matrix. In order to characterize these effects on the mechanical properties of fly ash concrete, this paper conducts qualitative assessment of hydration reactions and quantitative calculations of volumetric compounds in the material. Utilizing the Mori‒Tanaka scheme, a predictive model is then developed to integrate the hierarchical effects of constituents at multiple scales on the modulus of elasticity of low‐volume fly ash concrete. The reliability of the proposed model is validated through a series of mechanical tests involving various mix designs, as well as comparison with other published test data.

Numerical Modeling of Uniaxial Corroded Reinforced Concrete Columns Exposed to Fire

Corroded concrete structures remain at risk of fire damage throughout their lifespan. This study explores the fire resistance of reinforced concrete columns, considering the simultaneous impact of corrosion and high temperatures. Thermal–structural models of the corroded concrete columns are developed using SAFIR software (2022). The numerical results are compared with published test data on temperature distributions and axial displacement–time curves. Then, parametric analyses are conducted to investigate the influence of various factors, such as corrosion degree, concrete compressive strength, cover thickness, and fire exposure models, on the fire performance of the concrete columns. The findings reveal that corrosion significantly undermines fire resistance: notably, columns with severe corrosion exhibited a 47% reduction in fire resistance. Conversely, increased concrete strength can bolster the fire resistance of intact columns, particularly when the concrete cover is minimal. Enhancing the cover thickness proves to be an effective strategy to mitigate the thermal degradation of steel reinforcements, thereby extending the columns’ fire resistance by as much as 23%. The study introduces coefficients to quantify the effects of corrosion, fire exposure, material strength, and cover thickness, culminating in a practical formula to calculate the fire endurance of corroded reinforced concrete columns. This formula could complement existing fire safety regulations.

Web crippling design of cold‐formed ultra‐high strength steel lipped channels under ITF loading: A numerical parametric investigation

AbstractIn recent years, there has been a compelling need to adopt cold‐formed ultra‐high‐strength steel (CFUSS) in the construction industry owing to its numerous advantages, such as a higher strength‐to‐weight ratio, flexibility in achieving desired shapes, and adaptability over longer spans. Among the various applications, CFUSS lipped channel sections are commonly used as purlins and joists in steel structural systems. However, these sections are susceptible to different failure modes, particularly web crippling, which presents significant challenges. Currently, the current design rules lack specific guidelines for estimating the web crippling capacity of CFUSS sections. To address this crucial gap, the present study focuses on a comprehensive numerical investigation of the web crippling response of CFUSS lipped channel sections under interior‐two‐flange (ITF) loading conditions. Finite element (FE) models were developed using the ABAQUS package, verified against published test data, and subsequently used in an extensive parametric study. The ultimate web crippling capacity obtained from the parametric study was used to evaluate the accuracy of the current design equations in various design standards. The findings revealed that the existing design equations inadequately predicted the ultimate web crippling capacity of CFUSS lipped channel sections subjected to the ITF loading condition. Consequently, a modified design equation is proposed, utilizing the same approach as the current design standards, and a new direct strength method (DSM) approach is developed and verified through reliability analysis. The proposed modified design equations offer promising solutions to ensure safer and more reliable design practices for CFUSS structures in the construction industry.

A High-Efficiency Theorical Model of Von Karman–Generalized Wagner Model–Modified Logvinovich Model for Solving Water-Impacting Problem of Wedge

The water-impacting behavior of a wedge is often studied in the slamming phenomenon of ships and aircraft. Many scholars have proposed theoretical models for studying the water-impacting problem of a wedge, but these models still have some shortcomings. This study combines Von Karman’s method, the Generalized Wagner Model (GWM), and Modified Logvinovich Model (MLM) to establish a converged theoretical Von Karman-GWM-MLM (VGM) model. The VGM model utilizes added mass to replace the fluid influence, which is derived from the velocity potential and boundary conditions. Considering the influence of impulse, the velocity is determined by the momentum theorem. Subsequently, the pressure, resultant force, and acceleration of the wedge can be calculated. By comparing with the published test data of other scholars, it is found that the velocity, acceleration, pressure, and force of the wedge obtained by the VGM model reached a consensus with experiments. The validity and accuracy of the VGM model are also verified. The efficiency and accuracy of problem-solving are both balanced when using the VGM model. The establishment of the VGM model is significant for solving water-impacting problems related to wedges.

Prediction of Critical Heat Flux in Tube Bundles With Crossflow

Abstract Evaporators and boilers with flow across horizontal tube bundles are widely used in industries including refrigeration and chemical processing. As yet there is a lack of a well-verified correlation for predicting local or average CHF (critical heat flux) in such bundles. The available data and correlations are reviewed. The available methods for predicting bundle mean CHF were found to be too conservative. More realistic values of bundle average CHF are proposed based on published test data. The author's well-verified correlations for CHF on a single tube with the subcooled and saturated flow at zero quality across it are compared with test data for tubes in tube bundles together with other correlations. The author's correlations agree well with all data while the others fail for data other than their own. The results of the comparison are presented and discussed. The needs for further research are identified.

Nonlinear analysis and design of high-strength concrete filled steel tubular columns under nonuniform fires

The main objective of this study is to investigate the behaviour of concrete-filled steel tubular (CFST) columns with ultra-high strength concrete (UHSC) and high strength steel (HSS) under fires through finite element method (FEM). High-strength materials can be used in CFST columns to reduce member dimensions, lowering material consumption and foundation loads. However, their fire behaviour has been insufficiently examined, especially under nonuniform fire exposure. In this study, thermal-structural models of the composite columns are developed using the SAFIR software. The numerical results are compared with published test data on temperature distribution, axial displacement, lateral displacement, failure modes and failure time. Then, parametric analyses are conducted to investigate the influence of various factors such as concrete strength, steel strength, different fire exposures, column length and load ratio on the fire performance of the CFST columns. In addition, the tabular design approach in European code EN1994–1-2 and Australian/New Zealand code AS/NZS 2327:2017 for designing uniformly exposed CFST columns is evaluated. It is observed that the prescribed design values in the table for R30 and R60 fire ratings under load ratio lower than 0.47 appear insufficient for the allowable slenderer columns. The applicability of the tabulated data for a load ratio up to 0.47 is further checked for the columns with UHSC of 120 MPa and HSS of 690 MPa, which is the strength limits recommended in AS/NZS 2327:2017.

Experimental study on bond behavior of steel bar embedded in thin UHPC

Due to the high compressive strength and excellent tensile properties of UHPC, reinforced UHPC with a thickness of 45 mm–60mm and a concrete cover of 15 mm–19mm has been used in the steel-UHPC lightweight composite deck. However, the researches about the bond behaviors of steel bar in UHPC with the concrete cover less than 20 mm were still limited. This paper aimed to study the bond behaviors of steel bars in UHPC with a thinner concrete cover (≤20 mm) and develop the calculation method for the lower bound of bond strength. A program of pullout test was conducted using the tensile test setup mimicking the tensile stress condition of structural members. The effects of concrete cover (10 mm, 15 mm and 20 mm), steel fiber volume fraction (0.5%, 1% and 2%), steel bar diameter (10 mm, 12 mm, 14 mm and 16 mm), embedment length of steel bar (4db, 6db, 8db, 10db) on the bond behaviors of steel bar in UHPC were investigated through 11 groups of pullout test specimens. The test results showed that most specimens failed in concrete cover splitting and the bond strength was influenced to different degrees by the test variates. The bond strength for steel bar in UHPC with a steel fiber volume fraction of 2% varied from 12.29 MPa to 15.88 MPa, and an embedment length of 8db with a concrete cover of 15 mm could ensure the steel bar with a diameter less than 16 mm reached its nominal yield stress of 400 MPa before the bond failure. On the basis of pullout test results in this study and the published test data, an empirical equation was proposed to predicted the lower bound of bond strength for steel bar in UHPC.

Combined Effects of Stress, Gas Adsorption, and Temperature on the Evolution of Coal Seam Permeability and Slippage Effect.

The complexity of the evolution of the permeability of coal is determined by the reservoir structure. Further, there exists an interaction between the fracture matrix, which further complicates changes in permeability. When the actual mining conditions of a coal mine are considered, a permeability model that considered the combined effects of stress, gas adsorption, and temperature was proposed. Subsequently, the model is verified by published test data. Based on the analysis of permeability, a calculation model of the slip coefficient that considered the combined effects of stress, gas adsorption, and temperature is proposed. With respect to this, any change in the slippage coefficient is only determined by the width of the fracture channel, which affected the flow of coal gas. In the process of a temperature increase, the slip coefficient tends to increase and the larger effective stress corresponds to a larger slip coefficient. In addition, under constant-temperature conditions, we also discuss the evolution of coal permeability and the variation of the coal gas slippage factor under different boundary conditions through the proposed model. This study aims to further the understanding of the seepage characteristics and slippage effects of coalbed methane, which would have a positive impact on the mining of coal.

Numerical investigation on entry of an inclined cylinder into water under uniform current and wind

The entry of a circular cylinder into water represents the problem of the coupling of multiphase flow with highly unsteady and nonlinear dynamics. Few studies have examined the influence of the initial angles of inclination of the object on the evolution of the cavity and the multiphase flow field under impact-induced loads in the presence of currents and wind. In this study, we develop a three-dimensional numerical model in OpenFOAM® to simulate and analyze this entire process. An overset mesh technique was used to reproduce the entire process of the entry of a circular cylinder into water as well as the formation, pinch-off, and collapse of the cavity. A comparison between our numerical results and previously published test data from the laboratory confirmed that the proposed numerical model can accurately simulate the dynamic characteristics of the multiphase flow field. The mode and time series of the closure of the cavity varied with the initial angles of inclination of the cylinder, and in turn influenced its translational and rotational characteristics of motion. The pressure, velocity and vortex structures suggest that the evolution and distribution of multiphase flow field for upstream and downstream water entry cases have varied characteristics.

Structural behaviour of 2D post-tensioned precast beam-column sub-assemblages subjected to column loss scenario

Many previous studies have investigated alternative load path (ALP) mechanisms of 2D reinforced concrete (RC) beam-column sub-assemblages under column removal scenarios. However, how precast and prestressed RC structures respond under a column loss scenario receives far less attention, as evident from a lack of published test data. Herein, five 2D post-tensioned precast RC sub-structures subjected to a middle column loss scenario were tested by multi-point quasi-static loading. In all the specimens, individual precast members such as beams and columns were joined together through wet connection. The study focused on investigating the combined effects of post-tensioned tendon (PT) and wet connection on load-resisting mechanisms and the influence of basic parameters such as unbonded and bonded PT, T-beam effect, and boundary conditions. The test results indicated that both unbonded and bonded parabolic-shaped PT significantly enhanced compressive arch action (CAA) and catenary action (CA) beyond basic flexural capacity, and also changed the plastic hinge mechanism in the precast beams. The specimen with unbonded PT could provide greater residual capacity than bonded PT, but the former was severely damaged by fracture of normal reinforcement and crushing of concrete rather than fracture of the tendon. In addition, the effects of T-beam and boundary conditions are discussed in detail. Finally, new design criteria for precast and post-tensioned concrete structures under column removal scenarios are proposed for structural engineers to take advantage of high-strength tendons and avoid failure at critical locations by precast joints.

Review and Evaluation of the Prediction Methods for Voids in the Mineral Aggregate in Asphalt Mixtures

The percentage of voids in mineral aggregates (VMA) is an important consideration in the design of asphalt mixtures. Accurate and precise prediction of VMA is critical in pavement engineering. This study reviewed and evaluated current VMA prediction methods. From the perspective of treating aggregate gradation, the methods were classified into four categories: the overall gradation prediction method (OGPM), gradual gradation prediction method (GGPM), indirect parameter prediction method (IPPM), and theoretical derivation method (TDM). Fifty-four groups of published test data from previous studies were used to evaluate the prediction results of the models, and the precision and accuracy of the prediction results were compared. From the perspective of the completeness of the modeling parameters and the theoretical foundation, the reasons for the differences in prediction results with different methods were analyzed. It was concluded that the TMD has a solid theoretical basis, especially the Yu method in TMD exhibited the best prediction precision and accuracy. Some modifications to the current methods were suggested, such as incorporating other factors affecting VMA and optimizing the particle shape indicators.

Shear performance of reinforced concrete beams containing stirrups with lower bend defects

The reactive expansion caused by alkali-aggregate reactions and severe corrosion in a saline environment may both lead to fracture or complete section loss at the lower bends of stirrups and localized debonding of side-legs nearby. The effects of such bend fracture and the debonded length on the shear performance of a reinforced concrete beam were explored in laboratory experiments and through a finite element simulation. Bend-defects in the stirrups reduced the beam’s shear strength, and the reduction increased with the debonded length. And a parametric analysis indicated that the nominal shear stress carried by the stirrups with a given defect severity increased with section size, and the size effect of shear strength became less significant with increasing defect severity. An approach for predicting the shear strength of such defective beams was proposed based on a transparent and well-understood mechanical and physical model, and published test data confirm its accuracy and safety was confirmed by published test data on 35 beams of various sizes.

Correlation for CHF during subcooled flow across a single cylinder

A correlation is presented for prediction of CHF (critical heat flux) during upward flow of subcooled liquids across single cylinders. The correlation was verified against all available published test data. It includes five fluids (water, R-12, R-113, isopropanol, FC-72), tube diameter 0.25 – 19.1 mm, reduced pressure 0.0046 – 0.3554, liquid velocities 0.01 – 6.8 m/s, CHF 0.14 – 28.7 MW/m2, and quality −0.001 to −0.34. The new correlation predicts 496 data points from 28 data sets from 12 sources with mean absolute deviation (MAD) of 16.4%. The same data were also compared to other published correlations; their MAD ranged from 47% to 319.0%.

Study on Reinforcement Mechanism and Reinforcement Effect of Saturated Soil with a Weak Layer by DC

This paper presents a numerical investigation on the improvement mechanism of dynamic compaction (DC) in saturated soil of a weak layer with high levels of groundwater, using an improved fluid–solid coupling method with a Drucker–Prager–Cap soil model. The numerical model is verified by comparing with published test data at first, which show that the dual-phase coupling method can approximately reflect the development law of excess pore water pressure and the improvement effect of layered saturated soil foundation under DC. Then, based on the numerical model, the influences of the thickness and depth of the weak layer as well as tamping energy on the development and dissipation of excess pore water pressure, effective stress, and the relative degree of reinforcement during DC were investigated. The results showed that the embedment depth and thickness of the weak interlayer may greatly affect the effective reinforcement depth of DC. Meanwhile, the tamping energy and the groundwater table also play a great role in the improvement of the layered saturated soil under DC. The groundwater table should be lowered by dewatering or adding a drainage layer to achieve a better compaction effect during DC.

Multi-objective analysis design of spiral groove conical bearing considering cavitation effects

As the element of rotary motion, the evaluation of hydrodynamic behavior for spiral groove conical bearing (SGCB) is related with the stability of multibody systems and the influence of cavitation on the lubrication performance of SGCB is an important concern. This work presents a computational method for design of groove in the different operation conditions, considering multi-objective analysis. With the cavitation effects taken into account, the hydrodynamic behavior of SGCB is calculated with multiphase flow model accounting for phase transition process and cavitation phenomenon. Moreover, the numerical results are compared with the published test data and the maximum deviation between simulation and experiment is 6.63%, which demonstrates the validity of proposed model. Then, the detailed analysis of hydrodynamic response for SGCB is conducted, which represents that a suitable design of groove parameters would provide a better lubrication performance of SGTB.

General correlation for critical heat flux during saturated flow across a cylinder

A correlation is presented for prediction of CHF (critical heat flux) during upward flow of saturated liquids across single cylinders. The correlation was verified against all available published test data. It includes six fluids (water, R-12, R-113, methanol, isopropanol, acetone), tube diameter 0.26 - 19.1 mm, reduced pressure 0.0046 - 0.3554, liquid velocities 0.01 - 10.7 m/s, and CHF 0.14 – 10.7 MW/m2. The new correlation predicts 558 data points from 62 data sets from 15 sources with mean absolute deviation of 18.0%. The same data were also compared to seven other published correlations; their MAD ranged from 24.1% to 287.0%.

RGB image-based hybrid model for automatic prediction of flashover in compartment fires

This paper proposes a novel hybrid model for flashover prediction in a compartment fire based on visual information from RGB images that are the same as those captured by regular vision cameras. The proposed model was developed as a research tool to study the feasibility of predicting flashover based on RGB vision data. This model consists of sub-modules with data-based methods using Deep Neural Networks and knowledge-based methods using fire safety science and mathematical model. One of the crucial features of the proposed model is enabled by a novel Dual-Attention Generative Adversarial Network that is developed in this study for the vision-to-infrared conversion process. The model and the overall procedure were validated against published test data from a compartment fire. Results show that the proposed model achieved promising performance, which also shows the potential to monitor the constant changes in a room fire through continuous processing images of flame and smoke.

Fracture toughness prediction of hydrogen-embrittled materials using small punch test data in Hydrogen

In this paper, we propose a numerical methodology to predict the effect of hydrogen concentration on fracture toughness by using small punch (SP) test data in hydrogen. The proposed method performs finite element (FE) damage analysis, with the multi-axial fracture strain damage model based on. First, a damage model is derived from the tensile and fracture toughness test data obtained in air. Then, by simulating the SP test in hydrogen, the hydrogen-embrittlement constant is determined. Finally, fracture toughness of hydrogen-embrittled material is predicted using the determined damage model and hydrogen-embrittlement constant. To validate the proposed methodology, published test data of API X70 steel in hydrogen and air (or nitrogen) atmosphere are used. In terms of hydrogen concentration, the predicted fracture toughness agrees well with the fracture toughness test data obtained in hydrogen environment.

Design of circular steel flange plates subjected to tension loads – yield line approach

The use of circular steel flange plates with circular bolts pattern connections is common in tubular structures used in different applications such as transmission and communication structures. Several published literatures include methods for the design of these connections under tension loads. These methods are not widely used in the industry as they are either complex or yielding results that are not always consistent with published test data. Therefore, there is still a need for a simplified, yet accurate, method for designing these connections when subjected to tension loads.This paper presents a numerical study performed on circular flanged connections subjected to concentric axial tension loads. The analysis part of the study is conducted using the Finite Element (FE) package ADINA considering one common geometrical flange plate configuration, ring configuration, while considering contact surface separation. The results obtained from the FE analyses are compared with published experimental data from which it is concluded that the FE model can predict the behaviour of these connections with a high degree of accuracy.Parametric investigation is then conducted to numerically expand the experimental data to gain more insight into the behaviour of these flange plate connections and to use this data later in this work to validate the proposed design method. The varying parameters considered in the numerical investigation include base plate thickness; number of bolts; bolt circle diameter and plate diameter.A simple design approach based on yield line theory is then introduced and a comparison between yield loads predicted using the proposed model and the finite element results is presented. The yield loads resulting from proposed design method show good agreement with the finite element results with 10% maximum difference.