Soil-rubber mixtures underneath foundations are an eco-sustainable and low-cost Geotechnical Seismic Isolation (GSI) solution. Using rubber grains from end-of-life tyres in the mixtures can provide a ...modern recycling system that reduces the stockpile of scrap tyres worldwide. In recent years, gravel-rubber mixtures (GRMs) properties have been investigated, finding good behaviour in static and dynamic conditions. Laboratory tests on GRMs advantages as GSI in the form of a layer underlying the foundation of a structure are available in the literature. Nevertheless, only one experimental campaign on a full-scale prototype structure resting on GRMs with 0% and 30% rubber content per weight was performed (SOFIA-SERA Research Programme).
This paper presents 3D advanced nonlinear FEM analyses to reproduce and furnish new results about the above-mentioned full-scale test. The calibration of the parameters of the different constitutive models used for modelling the foundation soil and the GRMs was supported by an extensive geotechnical characterization. The developed FEM model was validated by the results from the above-mentioned full-scale test in terms of accelerations and velocities. Then, the dynamic behaviour of the GRMs was studied, also considering the shear strains versus the shear stresses and the horizontal and vertical displacements, quantities not investigated experimentally. Finally, the GRMs static behaviour was also investigated, considering the GRMs axial strains and the GRMs and foundation vertical displacements.
The paper highlights the fundamental role of both experimental tests and numerical modelling, as invaluable tools for coupled analyses of the seismic behaviour of soil-structure systems, including innovative materials, such as GRMs, and the main advantages of using GRMs as GSI.
•Gravel-rubber mixtures (GRMs) are an eco-sustainable and low-cost geotechnical seismic isolation system.•Using end-of-life tyres as rubber grains in GRMs provides a modern recycling system.•3D numerical analyses reproduce and furnish new results about recent tests performed on a full-scale structure on GRMs.•The Authors performed a fine calibration of the advanced HSsmall constitutive model parameters for the investigated GRMs.•GRMs with 30% rubber content per weight significantly mitigate the ground motion.
The presence of karst formations significantly impacts the load-bearing capacity of pile foundations in karst geological environments, posing a challenge to their design. This study investigated the ...bearing characteristics of karst pile foundations using the physical model test and numerical analysis. First, the influence of cave height and span on the bearing capacity of pile foundations is examined using model tests. The results demonstrate that the height of karst caves greatly affects the bearing capacity of karst pile foundations. Subsequently, numerical analysis further explores the bearing characteristics of these foundations. It reveals that as the top load on pile increases, an arch-shaped tensile damage zone forms at the top of karst cave and gradually expands. The rock failure in this area leads to a decrease in adhesion between rock strata and pile foundation, consequently reducing its load-bearing capacity. Finally, experimental results are compared with numerical results to validate consistency and mutual verifiability between physical model tests and numerical analyses. The outcomes of the research provide valuable insights for designing rock-socketed pile foundations in similar karst areas.
Steel shear panel dampers (SPDs) have been widely used in structural seismic design. The low cycle fatigue damage for SPD often occurs close to the welded stiffener, significantly weakening the ...fatigue performance of the damper. A novel steel shear panel damper called a buckling restrained shear panel damper (BRSPD) is proposed in this paper. A BRSPD has two main parts, an energy dissipation plate and two restraining plates. No stiffener is welded to the energy dissipation plate. The two restraining plates clamp the energy dissipation plate with bolts on both sides to prevent out-of-plane buckling. Quasi-static tests of five specimens were carried out to investigate the performance of the BRSPDs. The test focused on the stiffness and strength of the restraining plates and the gaps between them and the energy dissipation plate. The tests showed that the restraining plates with adequate stiffness and strength can effectively restrain the out-of-plane buckling of the energy dissipation plate. Numerical analysis of the BRSPD was conducted using the general finite element program, ABAQUS, to supplement the test results. A design method for the restraining plates and the bolts is suggested based on the test and analysis results.
•The novel shear panel damper call BRSPD is proposed and the physical test is carried out.•No stiffener is welded on the energy dissipation plate.•The gaps between external restraining plates and energy dissipation plate should be no more than 1mm.•The formula for the restoring force of the BRSPD has been derived with the help of finite element analysis.•The stiffness demand of the external restraining plate is derived through the buckling analysis.
The paper presents the results of 3D coupled cyclic time history numerical analyses of a monopile supporting a 12 MW Offshore Wind Turbine, installed in dense cohesionless soils and subjected to a ...600-s load history corresponding to the high phase of a 35-h design storm. The goal of the study is to investigate the governing mechanisms and gauge potential conservatisms or uncertainties in approaches for monopile analysis used in practice. The Ta-Ger constitutive model, implemented in FLAC3D and calibrated against site-specific cyclic tests, is used to model the complex soil response. Emphasis is placed on the effect of drainage conditions, an aspect typically overlooked in practice, although often stated as critical. Analyses show that the drainage of the system can substantially affect the response. In low-permeability soils (e.g., cohesionless soils with low-plasticity fines) widespread liquefaction may occur inducing high rotations above allowable limits. On the contrary, systems that can drain effectively within each cycle, develop moderate excess pore pressures which do not jeopardize performance. Current design procedures are often unable to accurately capture these effects possibly leading to either conservative or unconservative outcomes. Suitably validated advanced numerical analyses can be used as complementary tools to standard methods to assess these uncertainties.
•Advanced numerical methodology for cyclic time history analysis of monopiles.•Use of Ta-Ger constitutive model for complex soil response.•Validation against centrifuge tests.•Drainage conditions can have a substantial effect on the response.•Current design methodologies may be unable to capture drainage effects.
•Shear was found to have significant impact on the LTB resistances.•3344 cases were investigated with eigenvalue and large-displacement analyses.•Stiffened and unstiffened beams with a large variety ...of load were investigated.•Design equations were proposed for shear effects in singly-symmetric I-beams.•Proposed equations can achieve much better accuracy than Winter's approach.
This paper presents an investigation on the negative effects of shear on the lateral torsional buckling (LTB) of singly-symmetric I-shaped beams due to web distortion associated with shear. Results from a parametric FEA study including eigenvalue buckling analyses and large-displacement analyses were utilized considering both stiffened and unstiffened webs to consider the impact of shear on the LTB resistance. Moment gradients caused by constant shear and a shear gradient were considered. The FEA solutions demonstrate that shear can significantly reduce the lateral-torsional buckling resistance. The FEA results were used to develop design equations that account for the reduction in the LTB capacity from shear. The solutions were compared with conventional methods proposed by Winter to account for the effects of web distortion on girders with slender webs. Results from the study show that (i) the average flange area should be used to account for the effects of shear of singly-symmetric beams; (ii) post-buckling strength has limited impact on the shear effects with regards to the LTB resistance; and, (iii) compared to Winter's approach, the proposed method can capture the variation of the moment reduction factor with the shear force in the unbraced length, and is able to predict moment resistances with reasonable accuracy compared to refined FEA solutions using both eigenvalue analysis and large-displacement analysis. Design examples are provided to demonstrate the calculation procedure.
•A sub-sized short bend beam configuration was designed for mixed mode fracture toughness studies.•All mode I and II mixities can be covered by the short bend beam specimen.•The short bend beam ...specimen was utilized for mixed mode I/II bone fracture toughness testing.•Mode II fracture toughness of tested bone was significantly less than its KIc value.•The experimental results were predicted using both GMTS and EMTSN criteria.
In this paper an angled edge cracked short beam specimen subjected to symmetric three-point bend loading was designed and examined for conducting mixed-mode I + II fracture toughness experiments. This specimen is suitable for being used in those experimental crack growth studies in which a very limited amount of raw material is available for the preparation of the test specimen. By conducting several finite element analyses, it was shown that the short bend beam specimen is able to produce full modes I and II mixities if the affecting parameters such as the crack length ratio, loading span ratio and crack inclination angle are set in suitable ranges. The practical ability of the short bend beam specimen was investigated for obtaining the mixed-mode I + II fracture toughness of bovine bone and the corresponding values of KIc and KIIc were determined for different mode mixities. While a significant discrepancy was observed between the experimental results and predictions of the conventional singular based fracture theories, it was demonstrated that the two-parameter (K &T) based fracture models such as GMTS and EMTSN criteria can provide significantly improved predictions for the fracture behavior of tested short bend beam specimen made of bone material.
The construction of twin tunnels is a mandatory guideline and a prevailing practice in either conventional or mechanized tunneling. Nevertheless, most of the design methods for calculating the tunnel ...loads focus on single tunnels, neglecting thus the potential interaction between neighboring tunnels. The effect of such interaction can be significant, especially for closely-spaced twin tunnels. In this context, this paper investigates via parametric 3D finite element analyses the interaction between deep, parallel-twin, circular and non-circular tunnels excavated with a conventional (i.e., non-TBM) method and supported with shotcrete lining. The numerical investigation focuses on the axial forces acting on the primary support of the tunnels by examining the effect of a wide range of geometrical (pillar width, overburden height, tunnel diameter and section (shape), lagging distance), geotechnical (strength and deformability of the surrounding rockmass, horizontal stress ratio), structural (thickness and deformability of the shotcrete lining) and construction parameters (full- or partial- face excavation and support of the tunnels). The results of the analyses indicate that the construction of the subsequent tunnel influences the loads of the precedent. The stress state of the single tunnel is used as the reference for the quantification of the interaction effect. The output is presented in normalized design charts of the quantified interaction effect on the axial forces versus key geomaterial and geometry parameters to facilitate preliminary estimations of primary support requirements for twin tunnels. Furthermore, nomographs are provided for preliminary assessments of the optimum pillar width (spacing) between twin tunnels, which practically eliminates the interaction effect.
This work investigates the dynamic response of a Rugby union protective headgear under frontal impact. The model used in the numerical analyses was developed based on commercially available products, ...and consisted of a shell padded with prismatic elements. The material model used for the padding consisted of a hyperfoam formulation and was calibrated based on experimental procedures carried out on specimens cut from protective helmets. In order to assess the effectiveness of the protective equipment, simulations of the impact of the head-helmet assembly with a rigid surface utilizing different kinetic energies were performed.
This study was conducted to examine the behavior of steel-reinforced ultra-high performance concrete-filled stainless steel tubular (SRUHPCFSST) intermediate columns under eccentric loads. There were ...nine columns tested in the test program, all of which were subjected to static eccentric loading with consideration given to the effects of the eccentricity, diameter-to-thickness ratio, steel ratio, and eccentric direction. The columns were evaluated to determine their performance characteristics such as ductility, load-displacement relationships, load-strain relationships, and failure modes. The intermediate SRUHPCFSST columns demonstrated good load-carrying and deformation capacity as well as a clear instability failure under eccentric compression after reaching their maximum load. The ultimate bearing strength of the columns decreased significantly with the increase of the diameter-to-thickness ratio and eccentricity, and the increase of the steel ratio or loading in the major axis of the steel skeletons effectively improved the ultimate bearing strength and ductility of the columns. The numerical simulation of the eccentric compression on the SRUHPCFSST was carried out with the finite element software ABAQUS, and the effects of the L/D ratio, concrete strength, steel skeleton strength, and large eccentricities on its eccentric bearing strength were expanded and analyzed. The eccentric bearing strength of the SRUHPCFSST intermediate columns was calculated using a formula derived from the test data and the numerical analyses. The results of the equation correlated well with the experimental data and can serve as a reference for future research in this area.
•UHPC, stainless steel tubes and embedded steel skeleton can improve the eccentric bearing strength of composite columns•The formula derived from the study can predict the eccentric bearing strength of composite columns more accurately•Eccentricity, radius-thickness ratio and L/D ratio have a large impact on the eccentric bearing strength of composite columns•UHPC, stainless steel tube and embedded steel skeleton have great cooperative effect under eccentric loads
The current study aimed to evaluate the mechanical behavior of two different maxillary prosthetic rehabilitations according to the framework design using the Finite Element Analysis. An ...implant-supported full-arch fixed dental prosthesis was developed using a modeling software. Two conditions were modeled: a conventional casted framework and an experimental prosthesis with customized milled framework. The geometries of bone, prostheses, implants and abutments were modeled. The mechanical properties and friction coefficient for each isotropic and homogeneous material were simulated. A load of 100 N load was applied on the external surface of the prosthesis at 30° and the results were analyzed in terms of von Mises stress, microstrains and displacements. In the experimental design, a decrease of prosthesis displacement, bone strain and stresses in the metallic structures was observed, except for the abutment screw that showed a stress increase of 19.01%. The conventional design exhibited the highest stress values located on the prosthesis framework (29.65 MPa) between the anterior implants, in comparison with the experimental design (13.27 MPa in the same region). An alternative design of a stronger framework with lower stress concentration was reported. The current study represents an important step in the design and analysis of implant-supported full-arch fixed dental prosthesis with limited occlusal vertical dimension.
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