Full-scale Model Tests Research Articles

Basic Study on the Proposal of New Measures to Improve the Ductility of RC Bridge Pier and Their Effectiveness

To enhance the seismic performance of reinforced concrete (RC) elements, it is essential to consider both strength and ductility post-yielding. This study proposed a novel method to improve the ductility of RC piers by using preformed inward-bending longitudinal reinforcements at the plastic hinges. Two full-scale model tests of standard and ductility-enhanced (DE) RC piers and numerical simulations were conducted. The lateral reversed cyclic loading experiments were conducted to assess the effectiveness of this new approach. The performance was evaluated regarding failure mode, plastic hinge distribution, hysteretic properties, normalized stiffness degradation, normalized energy dissipation capacity, bearing capacity, and ductility. Non-linear finite element method (FEM) analyses were also carried out to investigate the usefulness of the proposed method by DIANA, and simulation was validated against the experiment results by hysteretic curves, skeleton curves, failure mode crack pattern, ductility coefficient, and bearing capacity. The results indicated that the proposed method enhanced bearing capacity, resistance to stiffness degradation, energy dissipation capacity, and ductility. Additionally, it was observed that the preformed positions and curvature of the main steel bars influenced the plastic hinge location and the buckling of longitudinal reinforcements. FEM analysis revealed that it might be reasonable to deduce the other factors that influenced the ductility of the specimens by using the same material parameters and models.

Analysis of damage characteristics of the rectangular steel container under near-earth explosion loading

In this study, the dynamic response of a semi-buried steel vessel under a near-surface explosion shock load was investigated through full-scale model tests. A three-dimensional precise numerical simulation model of the semi-buried steel vessel structure was established, and the dynamic response and damage consequences under different load conditions were analyzed. The influence of the thickness of corrugated steel on the dynamic damage and antiknock properties of the structure was studied. The results show that the weak part of the rectangular steel vessel structure is mainly located at the connection between the blast-facing panel and the beam column under near-surface explosion conditions. The peak stress and displacement of the blasting surface decrease with the increase in the horizontal angle of the incident wave, whilst/while increase with the height of the explosion. Under the same explosive yield, the main failure mode of the structure is the tearing of the plate and beam under plastic deformation. Increasing the thickness of the corrugated steel can significantly restrain the plastic deformation and acceleration of the plate. When the thickness is increased from 2 mm to 6 mm, the antiknock performance is significantly improved. However, when the thickness is increased from 6 mm to 8 mm, the improvement in antiknock performance slows down. Increasing the height of the enclosing soil can also effectively improve the explosion-proof performance of the structure, with full burial providing the best effect. The research results provide a theoretical basis for the application of rectangular steel vessel structures in the field of protection engineering.

Evaluating Partial Safety Factors for Shear Strength in Bearing Capacity Calculations for Cohesionless Soils

Calculating bearing capacity is critical when designing shallow foundations. Many countries use limit state design (LSD) as the standard method for geotechnical design. The paper aims to develop realistic LSD partial factors for bearing capacity calculations of shallow foundations on cohesionless soils based on full-scale model tests. The experimental setup consisted of a hydraulic jack, concrete footing, sand samples, and pressure cells placed in a cylindrical wall. Fifteen sand samples were tested and classified by gradation and relative density. Settlement curves were plotted for each sample under an increasing load. The measured ultimate bearing stresses were found to be higher than theoretical values calculated using traditional methods. This indicates that the traditional approach is conservative. The suggested safety factor for the internal friction angle in cohesionless soils (γtan(ϕ)= 1.10) is notably lower than the values specified in Eurocode 7 at 1.25 and the Egyptian code of practice at 1.30. The proposed LSD partial factors allow for more economical designs than traditional factors while maintaining safety. The full-scale model-testing approach is novel and provides realistic factors directly applicable to Egyptian codes. The results are satisfactory and reasonable for the geotechnical design of shallow foundations on cohesionless soils. Doi: 10.28991/CEJ-2024-010-07-015 Full Text: PDF

Shrinkage separation prediction of concrete-filled steel tube arch bridge: A coupling model concerning multiple factors

The shrinkage separation is one of the key factors restricting the development of concrete-filled steel tube (CFST) arch bridge. In this paper, its mechanism and evaluation method concerning multiple factors, including structure, environment, material and construction were investigated. Firstly, the hydration process of in-tube concrete was simulated using the hydration degree as a basic state parameter. Then with the consideration of energy and mass conservation, as well as the moisture and heat transmission effects, the temperature and relative humidity fields, early-age mechanical properties, basic creep, and total deformation of in-tube concrete were further calculated. On the basis, in accordance with the stress criterion and displacement coordination, a multi-field (hydro-thermo-hygro-constraint) coupling model was finally established, taking the ratio of normal stress to bonding strength at the steel-concrete interface as the shrinkage separation risk index. The simulation results obtained from the model were in good agreements with the full-scale CFST model test.

Experiment and numerical study on the static and fatigue behavior of a novel deck joint

To increase the prestressing efficiency and alleviate the longitudinal cracking in the concrete slab of composite cable-stayed bridges, a novel deck joint was proposed. The joint is composed of epoxy joint and concrete wet joint, which allows to introduce the prestress before the precast deck slabs are connected to the steel girder, therefore significantly increases the prestressing efficiency. Full-scale test models were fabricated and tested under repeated negative bending load, with the main variables being prestress level and fatigue load amplitude, and the evolutions of displacement, strain, crack width and moment distribution were investigated. A numerical study was conducted to investigate the effects of joint geometries and prestress level on the joint strength, the moment distribution and the neutral axes. The failure mechanism of the joint was revealed and a calculation method was recommended. Results show that the failure modes of the test models are rebar fracture in the tension zone, and the prestress has significant benefits on the joint behavior. The moment distribution between the precast and the post-cast sections is affected by the prestress level and the width ratio of epoxy and wet joints. The recommended method can predict the static flexural resistance of the joint with accuracy.

Prediction method for the tension force of support ropes in flexible rockfall barriers based on full-scale experiments and numerical analysis

This paper proposes a prediction method for the tension force of support ropes in flexible rockfall barriers. The method is based on two full-scale model tests with an impact energy of 3000 kJ, as well as 36 set numerical models featuring varying lengths and impact energies. From the results of full scale tests and numerical models, it is inferred that the tension force at the end of the support rope is significantly less than that at the point of impact, exhibiting an approximate Gaussian attenuation distribution with propagation distance. To account for the attenuation of tensile forces in support ropes, a tensile attenuation coefficient is defined. Through comparative analysis of data obtained from 36 models with varying impact energies and propagation distances, the average attenuation coefficient for the upper support rope is determined to be approximately 0.7, while the average coefficient for the lower support rope is around 0.8. Utilizing the least squares method, a prediction method for the tension force of support ropes in flexible rockfall barriers is established. This method takes into account both the propagation distance and impact energy, enabling accurate predictions of the tensile behavior of the ropes under different conditions. This prediction model provides valuable insights for engineers in the design and optimization of these flexible barriers for rockfall mitigation.

Full-Scale Model Tests of Two Box-Type Soil-Steel Structures with Different Crown and Haunch Radii.

Compared with circular, arched, and pipe-arched soil-steel structures, box-type soil-steel structures (BTSSSs) have the advantages of high cross-section utilization and low cover depth. However, the degree of influence of the crown and haunch radii on the mechanical performance of BTSSSs is still unclear. Therefore, two full-scale BTSSS models with a span of 6.6 m and a rise of 3.7 m but with different crown and haunch radii were established, and the mechanical properties during backfilling and under live load were tested. Afterward, 2D finite element models (FEMs) were established using the ABAQUS 2020 software and verified using the test data. The influence of cross-section geometric parameters on mechanical performance was analyzed by using the FEM, and a more accurate formula for calculating the bending moment during backfilling was proposed. The results show that the BTSSS with a smaller crown radius has a stronger soil-steel interaction, which promotes more uniform stress on the structure and makes the structure have smaller relative deformations, bending moments, and earth pressure. The span and arch height greatly influence the bending moment and deformation of the structure. Based on the CHBDC, the crown and haunch radii were included in the revised calculation formula.

Experimental investigation of the geometry of geocell on the performance of flexible pavement under repeated loading

To evaluate the benefit of geocells of different geometrical configurations for pavement application, full-scale instrumented model tests were performed on pavement sections reinforced with geocells of different geometrical configurations subjected to monotonic and repeated loading. The responses studied were stress distribution in different pavement layers, induced strains in geocell walls, and settlement characteristics. The reinforced sections exhibited a significant reduction in rut depth as well as localized stress concentration compared to the unreinforced section. The reduction in rut depth was found to be influenced by the geocell height as well as weld spacing. The geocell reinforcement was found to distribute the stresses in the subgrade and subbase layers more efficiently, thus reducing the stress concentration in these layers. The strain measurements were found to be higher at the bottom of the geocell walls indicating a higher confinement effect on a lower part of the geocell. In the field, mostly geocells of 356 mm weld spacing and 150 mm height (SW356-H150) are used. However, this study suggests that a geocell of 330 mm weld spacing and 100 mm height (SW330-H100) having approximately 30% lower cost compared to SW356-H150 is as effective in reducing the rut depth and localized vertical stress distribution.

Numerical Analysis of Ground Surcharge Effects on Deformation Characteristics in Shield Tunnel Linings

To investigate the deformation characteristics of shield tunnel linings under ground surcharge, finite element software was employed to create a detailed three-dimensional model of the staggered assembly of the shield tunnel lining. This model includes components such as precast concrete segments, reinforcements, and joints (comprising bent bolts, washers, and bolt sleeves). Additionally, the model accounts for interface frictions between segments and the interactions between different rings. The reliability of the numerical model was verified based on the results of a full-scale model test. Additionally, the model accounts for interface frictions between segments and the interactions between different rings. Changes in tunnel convergence, joint tensioning, bolt stresses, reinforcement stresses, and concrete crack development were systematically analyzed. The results indicate the following: (1) the deformation mode of the lining structure under ground surcharge resembles a “transverse ellipse”. Joints located near the haunch opened along the outer arc, while those near the vault and bottom opened along the inner arc. The restraining effect of the bolts on joints opening in the inner arc was greater than that on the outer arc. Notably, when the opening of the inner arc reached 4.9 mm, the bolt stress escalated to the yield strength of 640 Mpa. (2) Under larger loads, the lining structure’s joints are susceptible to greater deformation, resulting in the tensile yielding of local reinforcement within these joints. (3) Cracks predominantly occur near the haunch, vault, and bottom of the lining structure, with the central angle of crack distribution ranging between 70° and 85°.

Mechanical characteristics and stability analysis of an innovative type of steel–concrete composite support in shallow-buried excavation tunnels

Under the influence of the principle of New Austrain Tunnelling Method (NATM), the initial support structure of shallow-buried tunnels in urban soft rock mainly adopts the forms of section steel arches or lattice girder arches combined with bolt-mesh-shotcrete. In order to solve the problems of tunnel deformation and collapse caused by untimely support or insufficient support strength during the construction process, the concept of “timely and high-strength support” was put forward, the high-strength steel pipe grid (HSPG) arch was innovatively designed, and the steel pipe grid bolt-shotcrete (SPGB) structure was established. Next, the flexural bearing performance and failure modes of the joint component and jointless component of the HSPG arch were analyzed, and the design scheme was also optimized by finite element simulation. Then, the full-scale model test of steel pipe grid concrete component (SPGC) under the pure bending load was conducted to explore the coupling bearing effect in a laboratory. In addition, relying on the underground excavation tunnel project of urban subway, the characteristic curves and stability coefficient of surrounding rock and SPGB structure were given by using the principle of convergence-confinement method. Theoretical calculations and on-sit measurements showed that SPGB structure had good adaptability in weak surrounding rock tunnel. In general, the research results were of great significance for clarifying the bearing mechanism and applicable conditions of SPGB structure, and also provided a reference for its further application in the tunnel and underground engineering.

Utilizing 3D printing for geomembrane fabrication in laboratory-scale geotechnical testing

This research investigates the innovative application of 3D printing technology in the production of geomembranes for laboratory-scale geotechnical experiments. Commonly, geotechnical research relies on the results of model testing. However, due to the high costs and complexity involved, full-scale model testing is rarely carried out. Geomembranes are essential components in various civil engineering projects, particularly in environmental containment and hydraulic barrier systems. In this research, the potential of 3D printing as an innovative method for producing geomembranes is carried out. Using a 3D printer, this research aims to prepare geosynthetic models with accurate geometric scales and tensile properties suitable for laboratory testing. A comparison was made between HDPE geomembranes and 3D printed geomembranes, to highlight their performance in a geotechnical laboratory environment. The research results show that 3D printed geomembranes show potential for applications in geotechnical research.

Full-scale model test for the performance of DDS prestressed composite lining with SCC-NC of high internal pressure shield tunnel

To meet the requirements of structure design for high internal pressure with large diameter tunnel and long-distance concrete pouring, a Double-layered and Double-looped Steel-strand(DDS) prestressed composite lining with Self-Compacting Concrete (SCC) and Normal Concrete (NC) was presented. A series of SCC and NC properties tests were conducted to prepare optimal DDS prestressed concrete, followed by a standing full-scale loading test to demonstrate the features of deformation and bearing capacity for the composite lining. The results showed that the DDS combined bearing structure has good bearing capacity to internal pressure, where the bearing process was divided into three stages. In the elastic stage, there was no cracks appeared and the structure began to show a tensile trend with the increase of internal pressure. The structure entered the inelastic stage when the internal pressure reached 1.1 MPa, the cracks were found to initiate. As the internal pressure was increased to 1.3 MPa, the structure entered the crack propagation stage, where the expansion of cracks in the inner lining would lead to a stress redistribution. For the internal pressure from 0 to 1.45 MPa, the average proportion of internal pressure borne by the inner lining decreases from 80 % to 70 %, while the one by the outer lining increases from 20 % to 30 %. Our findings demonstrate the mechanical behavior of the optimized bearing structures and provide guidance for the design and construction in related tunnel engineering.

Thickness regression for backfill grouting of shield tunnels based on GPR data and CatBoost & BO-TPE: A full-scale model test study

Ground penetrating radar (GPR) is a vital non-destructive testing (NDT) technology that can be employed for detecting the backfill grouting of shield tunnels. To achieve intelligent analysis of GPR data and overcome the subjectivity of traditional data processing methods, the CatBoost & BO-TPE model was constructed for regressing the grouting thickness based on GPR waveforms. A full-scale model test and corresponding numerical simulations were carried out to collect GPR data at 400 and 900 MHz, with known backfill grouting thickness. The model test helps address the limitation of not knowing the grout body condition in actual field detection. The data were then used to create machine learning datasets. The method of feature selection was proposed based on the analysis of feature importance and the electromagnetic (EM) propagation law in mediums. The research shows that: (1) the CatBoost & BO-TPE model exhibited outstanding performance in both experimental and numerical data, achieving R2 values of 0.9760, 0.8971, 0.8808, and 0.5437 for numerical data and test data at 400 and 900 MHz. It outperformed extreme gradient boosting (XGBoost) and random forest (RF) in terms of performance in the backfill grouting thickness regression; (2) compared with the full-waveform GPR data, the feature selection method proposed in this paper can promote the performance of the model. The selected features within the 5–30 ns of the A-scan can yield the best performance for the model; (3) compared to GPR data at 900 MHz, GPR data at 400 MHz exhibited better performance in the CatBoost & BO-TPE model. This indicates that the results of the machine learning model can provide feedback for the selection of GPR parameters; (4) the application results of the trained CatBoost & BO-TPE model in engineering are in line with the patterns observed through traditional processing methods, yet they demonstrate a more quantitative and objective nature compared to the traditional method.

Macro-microscopic dynamic characteristics of the ballast bed induced by the variation of moisture content

Due to the excellent drainage performance of the ballast, existing studies mainly focus on the dynamic response of ballast under field capacity or saturation. Attention has rarely been paid to dynamic changes in moisture content and potential influences. In this article, we firstly conduct a model test to determine the variation of ballast moisture content under artificial rainfall. After that, a full-scale model test with cyclic loading is carried out to study the effect of moisture content variation on the macro-microscopic response of the ballast bed, where several wireless particle sensors are installed to obtain ballast motion characteristics at strategic locations. The results show that the moisture content increases gradually and stabilizes at a flat peak under rainfall, despite the excellent drainage performance of ballast bed. After halting rainfall, the moisture content drops back to field capacity, which indicates dynamic flowing surface water on ballast particles under rainfall. Such flowing surface water brings changes to the original dynamic equilibrium of ballast bed: macroscopically, the deformation rate of stabilized ballast bed increases significantly, reaching a local peak under field capacity; microscopically, the x- and z-angular accelerations of the ballast show positive correlation with rainfall intensity. The multiscale responses indicate that field capacity is a critical moisture content.

Shear behavior of gypsum boards sheathed CFS framed shear walls with enlarged edge members

This study investigates the influence of nonshear components on the shear performance of cold-formed steel (CFS) framed shear walls. Regarding the connection fields between nonshear components and shear walls as reinforced edge members (REMs), full-scale model tests of six gypsum board sheathed CFS framed shear walls were conducted with a focus on investigating the shear behavior of CFS framed shear walls with enlarged edge members. A numerical simulation method for predicting the shear performance of CFS framed shear walls with enlarged edge members was established and verified. The results show that, (1) After the “diaphragm effect” was weakened or even eliminated, the REMs still had the ability to resist the bending moment and shear force, preventing CFS structures from collapse. (2) The REMs (containing wing walls) changed the mechanical feature of CFS framed shear walls that depended only on the “diaphragm effect” to resist the shear force and transformed the wall’s plastic development mechanism, improving the energy dissipation capacity of the walls over four times. Such a “wing wall effect” should be considered when estimating the influence of nonshear components. (3) The recommended response modification factor should be increased by at least 1.3 times due to the REMs. (4) The relative errors between the simulated and test results were within 8%.

Full-Scale Model Test of Subway Contact Channel under Mechanical Construction

The mechanical construction method for a subway contact channel has the advantages of a short construction period and high safety, and is more and more being applied in coastal soft-soil areas. In order to explore the suitability of this method in inland areas, a full-scale model test platform is used to simulate the shield-cutting construction process of the subway contact channel. The convergence deformation of the segments and the strain of the reinforcement and concrete are tested, so as to analyze the internal force and deformation law of the tunnel structure during cutting construction. The influence of the steel ring on the deformation of the subway contact channel is also studied. It is found that the segment convergence at the top is less than that at the waist position, and the convergence deformation of the waist is less than 30 mm; the internal force of the segment redistributes and the axial force mainly decreases during the cutting process; the stress state may change from compression to tension. The segment structure of the main tunnel, the supporting structure in the tunnel, and the stiffness of the steel-ring-lined composite pipe segment have little influence on the cutting force of the contact channel. The research results provide the corresponding technical indexes for the construction of a contact channel by the mechanical method, as well as a reference for the design and optimization of a steel-ring-lined composite pipe segment.

Mechanical Properties of Composite Track Beam for Medium and Low Speed Maglev Transit

Traditional medium-low speed Maglev track separated beam structures have drawbacks such as large structural height and neglect of F-type rail stiffness. This study proposes a new integrated track beam for medium-low speed maglev transportation. Finite element analysis is employed to compare the strength, stiffness, and natural frequencies of the integrated track beam with the existing separated track beam. The influence of beam height on the overall mechanical performance of the integrated track beam is analyzed. The ultimate bearing capacity of the steel-concrete composite joint in the integrated track beam is investigated through full-scale model testing. The results demonstrate that the proposed integrated track beam exhibits a 28% increase in flexural stiffness. The mid-span deflection is reduced by 19.9% under static and live loads. The first-order vertical natural frequency increases by 13.6%. The main factor governing the minimum beam height of the integrated track beam is the deflection limit under static and live loads. The beam height can be optimized from 2.1 m to 1.6 m. The model testing reveals that the F-type rail is controlled by torsional stiffness and can withstand 1.3 times the design load. The ultimate bearing capacity of the steel-concrete composite joint is 4.5 times the design load, providing sufficient load reserves.

Experimental study on optimization of continuous steel box girder bridge deck

ABSTRACT In order to accurately optimize the structural parameters of steel bridge deck(OSD), an optimal design method of continuous steel box girder bridge deck based on response surface method is proposed. Optimization design process includes full scale model test, finite element analysis, response surface function fitting and design parameter optimization. The orthotropic steel bridge deck’s deck thickness, stiffener thickness, diaphragm thickness, stiffener height, and diaphragm opening form are chosen as independent variables, and the internal forces of important structural components discovered are used as dependent variables. Design-Expert software created a five-factor, three-level response surface test. A multivariate quadratic response surface regression model between structural parameters and target response values was developed after the objective function and constraint criteria were identified. Numerical theory’s variance analysis was used to find the best combination, and Design Expert software was used to confirm it to make sure the design value was accurate. The findings indicate that optimized structural parameters are trustworthy because the difference between the predicted value and the theoretical value is less than 5%. An orthotropic steel bridge deck’s structural parameters can be optimized using the response surface approach. It serves as a reference for subsequent steel bridge deck design and construction.

Simulation Study on Static Characteristics of Qing-style ‘One Bucket Three Liters’ Column-cap Dou-Gong Bracket

The Dou-Gong bracket is a key transition component between the roof and the column in ancient Chinese wooden structures. In this paper, the static structural behavior of Qing-style ‘one bucket three liters’ Column-cap Dou-Gong Bracket (third-class material) full-scale test model was studied by simulation. The simulation of monotonic static loading was carried out in the vertical (Z-axis) direction, and the simulation of quasi-static loading under horizontal low-cycle reciprocating load was carried out in the horizontal direction (Y-axis, X-axis). The material of the simulation was P. sylvestris, and the setting of its material parameters referred to the results obtained from the material property tests. An anisotropic constitutive model suitable for the properties of wood materials was selected, and the elastoplasticity of wood in the simulation was defined by the Hill yield rule. The static structural behavior of the component in the Z-axis could be described by the variable stiffness linear elastic mechanical model. The static structural behavior of the component in the Y-axis and X-axis could be described by a multi-linear restoring force model. According to the simulation results, the key mechanical indexes of Dou-Gong bracket component in the Z, Y, and X axes were calculated from three aspects of strength, deformation, and energy.

A Machine-Learning-Based Method for Ship Propulsion Power Prediction in Ice

In recent years, safety issues respecting polar ship navigation in the presence of ice have become a research hotspot. The accurate prediction of propulsion power plays an important role in ensuring safe ship navigation and evaluating ship navigation ability, and deep learning has been widely applied in the field of shipping, of which the artificial neural network (ANN) is a common method. This study combines the scientific problems of ice resistance and propulsion power for polar ship design, focusing on the design of an ANN model for predicting the propulsion power of polar ships. Reference is made to the traditional propulsion power requirements of various classification societies, as well as ship model test and full-scale test data, to select appropriate input features and a training dataset. Three prediction methods are considered: building a radial basis function–particle swarm optimization algorithm (RBF-PSO) model to directly predict the propulsion power; based on the full-scale test and model test data, calculating the propulsion power using the Finnish–Swedish Ice Class Rules (FSICR) formula; using an ice resistance artificial neural network model (ANN-IR) to predict the ice resistance and calculate the propulsion power using the FSICR formula. Prediction errors are determined, and a sensitivity analysis is carried out with respect to the relevant parameters of propulsion power based on the above methods. This study shows that the RBF-PSO model based on nine feature inputs has a reasonable generalization effect. Compared with the data of the ship model test and full-scale test, the average error is about 14%, which shows that the method has high accuracy and can be used as a propulsion power prediction tool.