Validation Of Finite Element Model Research Articles

Investigation of different infill wall effects on performance of steel frames with shear beam-column connections under progressive collapse

This article examined steel frames with shear beam-column connections to determine the effectiveness of different masonry infill walls under progressive collapse. This research concentrated on the shear connection, which is the most common type of steel beam-column connection in steel buildings. Furthermore, this work experimentally evaluated one-third-scale steel-framed configurations with a single shear beam-column connection and another infilled steel frame wall configuration from the literature to verify the validity of 3D finite element models developed using the program ABAQUS. Finite element models were then used to investigate 16 different kinds of steel frames with infill masonry as well as the influence of multiple frames and the number of stories. In addition, the effects of a fully infilled frame and those of a bare frame and an infilled frame with openings were compared in flexural and catenary action phases. Results revealed that the steel building’s structural strength and energy dissipation against progressive collapse are significantly improved by infill walls.

Mechanical and morphological characterization of BCC - derived unit cells for biomedical devices

3D periodic cellular solids attract great attentions for applications in the biomedical field due to the combination of their mechanical and morphological properties.The mechanical behaviour of two classes of periodic cellular structures has been investigated: the first one is a strut-based structure; the second is a triply periodic minimal surfaces (TPMS) structure. Such structures derived from the body centered cubic (BCC) unit cell and were the G7 strut-based and the IWP sheet-based TPMS structure.The study was aimed at the mechanical and morphological characterization of the above cited cells for their application in biomedical devices. By means of the additive manufacturing Electron Beam Melting (EBM) technology, the G7 microlattice structures have been produced in titanium alloy. Compression tests have been carried out on three different levels of relative density, selected to evaluate the effect of this parameter on the mechanical properties.The correlation between relative density and mechanical properties of the G7 structure was defined by the Gibson-Ashby model. SEM analyses have been performed before the experimental tests in order to detect the morphological features and the matching between designed and real parameters, and after the tests to evaluate the failure mechanism of the structures. The experimental tests results were used for the validation of a non-linear finite element model of both G7 and IWP structures with the application of the Johnson-Cook plasticity model. Different cell configurations were obtained by varying the relative density and the cell diameter, in order to evaluate the cell size effect on the mechanical properties. G7 unit cell meets the mechanical and morphological requirements for the application in the biomechanical field. However, the analysis of the collapse mode showed that an improvement of the mechanical behaviour is required. The numerical analyses performed on the IWP unit cell allowed to assess that the structure is suitable for the production of biomedical devices.

Web crippling of cold-formed steel built-up box sections

This research focused on the experiments, numerical simulations and design of cold-formed steel (CFS) built-up box sections failed by web crippling. The built-up box sections were formed by fastening two equal-sized unlipped channel sections face-to-face by self-tapping screws. Thirty-five web crippling tests are firstly described, which were conducted under Interior-Two-Flange (ITF), End-Two-Flange (ETF), Interior-One-Flange (IOF) and End-One-Flange (EOF) loading cases. The number and location of screws were varied along the channel flange width to study the influences of screw arrangements. The specimens were loaded along the major axis and the minor axis. Numerical simulations were also conducted. The experimental results were used in the development and validation of nonlinear finite element (FE) models. After validation, the validated numerical models were used for a comprehensive parametric investigation accounting for various cross-section dimensions, bearing lengths and screw arrangements. The experimental and numerical data were used to evaluate the design methods provided in the current design codes. Finally, two different design methods were proposed and assessed through the reliability analysis.

Experimental validation of a micro-CT finite element model of a human cadaveric mandible rehabilitated with short-implant-supported partial dentures

PurposeThis study aimed to address the predictive value of a micro-computed tomography (μCT)-based finite element (μFE) model of a human cadaveric edentulous posterior mandible, rehabilitated by short dental implants. Hereby, three different prosthetic/implant configurations of fixed partial dentures (“Sp”-3 splinted crowns on 3 implants, “Br” – Bridge: 3 splinted crowns on 2 implants, and “Si”- 3 single crowns) were analysed by comparing the computational predictions of the global stiffness with experimental data. MethodsExperimental displacement of the bone/implant/prosthesis system was measured under axial and oblique loads of 100 N using an optical deformation system (GOM Aramis) and the overall movement of the testing machine (Zwick Z030). Together with the measured machine force, an “Aramis” (optical markers) and “Zwick” (test machine) stiffness were calculated. FE models were created based on μCT-scans of the cadaveric mandible sample (n = 1) before and after implantation and using stl-files of the crowns. The same load tests and boundary conditions were simulated on the models and the μFE-results were compared to experimental data using linear regression analysis. ResultsThe regression line through a plot of pooled stiffness values (N/mm) for the optical displacement recording (true local displacement) and the test machine (machine compliance included) had a slope of 0.57 and a correlation coefficient R2 of 0.82. The average pooled correlation of global stiffness between the experiment and FE-analysis (FEA) showed a R2 of 0.80, but the FEA-stiffness was 7.2 times higher. The factor was highly dependent on the test configuration. Sp-configuration showed the largest stiffness followed by Br-configuration (17% difference in experiment and 21% in FEA). ConclusionsThe current study showed good qualitative agreement between the experimental and predicted global stiffness of different short implant configurations. It could be deduced that 1:1 splinting of the short implants by the crowns is most favorable for the stiffness of the implant/prosthesis system. However, in the clinical context, the absolute in silico readings must be interpreted cautiously, as the FEA showed a considerable overestimation of the values.

Crashworthiness capability of thin-walled fibre metal laminate tubes under axial crushing

This study aims to evaluate the crushing behaviour of aluminium-glass fibre reinforced plastic (GFRP) with different layer configurations known as fibre metal laminate (FML) subject to dynamic loading conditions. The tubes were assembled to form 2/1 and 3/2 layout configurations. Resin and braided fiberglass sleeve were introduced as composite layer and sandwiched with two layers of aluminium tubes in forming 2/1 lay-up structure while a layer of composite and aluminium tube is added up alternately for 3/2 lay-up structure. These tubes were tested to evaluate the impact characteristics under low-speed axial impact loading. A finite element (FE) model was also developed and validated against the experimental results. In the numerical evaluation using a validated FE model, the internal energy of an aluminium tube was higher than the internal energy of a GFRP tube when the FML tube was progressively crushed. A series of parametric studies have shown that the increase in aluminium and GFRP wall thickness resulted higher specific energy absorption (SEA). The FML tube fold similar to the crush mode of outer tube material as when it is in its single tube form. All tube configurations were progressively crushed and unlikely to fail under catastrophic failure. FE model founds the aluminium tube layer is more dominant in energy absorption mechanism of the FML tube and increasing the number of tube layers improved crashworthiness significantly. From this discovery, a FML tube could be considered as a suitable lightweight candidate for energy absorbing applications with considerable crashworthiness capability.

Experimental and Numerical Investigation of the Polyurea-Coated Ultra-High-Performance Concrete (UHPC) Column Under Lateral Impact Loading

It was found that polyurea coating could improve the integrity and the corresponding durability of the structural components. However, the strengthening effect of polyurea coatings for structures built with emerging ultra-high-performance concrete (UHPC) is still unknown due to the lack of studies. Therefore, this paper investigated the effect of the polyurea coating on the lateral impact resistance of UHPC columns through a combined numerical and experimental study. A total of five specimens were fabricated, including two UHPC columns and three UHPC columns with polyurea coating. To better characterize the structural response under dynamic loading, impact cases with different drop weight impact heights and axial force ratios were employed. The results showed that the UHPC column with polyurea coating exhibited superior lateral impact resistance compared to the UHPC column. The presence of the axial force increased the lateral impact stiffness and further reduced the deflection of the specimen. In contrast, the polyurea coating improved the specimen’s ductility and mitigated the peak impact force, thereby maintaining the specimen’s integrity without sudden shear failure. A three-dimensional finite element (FE) model of polyurea-coated UHPC columns under impact loading was then established and confirmed the experimental results. With the validated FE model, an intensive parametric study was conducted to investigate the effects of polyurea thickness, axial force ratio and impact energy on the lateral impact resistance of the UHPC column. The presence of the polyurea coating could significantly improve the lateral impact resistance of the specimen, thereby preventing the shear failure of the UHPC column, and thus, the effective thickness of the polyurea layer for the UHPC column was determined to be 2–6[Formula: see text]mm. The outcome of this research demonstrates the great merits of polyurea coating in improving the ductility and integrity of the UHPC column under lateral impact loading.

Experimental and numerical investigation of normal reinforced concrete panel strengthened with polyurea under near-field explosion

In this paper, field blast tests and numerical simulations were conducted to investigate the strengthening effect of polyurea on the blast resistance of the normal reinforced concrete (NRC) panels under near-field explosion. Five specimens were fabricated and tested, including two NRC panels, and three NRC panels sprayed with polyurea at the rear side. The experimental results showed that polyurea could effectively improve the blast resistance of the NRC panel with less damage and smaller residual displacement. Furthermore, with the existence of the polyurea, the integrity of the specimen could be maintained, and the deadly fragments of the concrete panel were captured, thereby reducing the secondary damage to surrounding personnel and structures. The finite element (FE) model of NRC panels strengthened with polyurea under near-field explosion was established using the Arbitrary-Lagrangian-Eulerian (ALE) method, and validated with the experimental results. Thereafter, the validated FE models were used to investigate the effects of scaled distances and polyurea thickness on the blast resistance of the NRC panel. This research is of direct importance to both practitioners and researchers involved with strengthening design for NRC components against explosion.

Cold-formed ferritic stainless steel perforated tubular stub columns: Behaviour and design

This paper reports the numerical axial behaviour of cold-formed ferritic stainless steel (CFFSS) stub columns with two circular perforations on opposite faces located centrally along the width and height of the column specimens. Numerical models are established using the finite element (FE) package ABAQUS and validated by using the test results of cold-formed carbon steel stub columns with perforations and CFFSS shallow stub columns reported in the literature. The modelling of the material properties and geometric imperfections has carefully been considered in the developed FE models and validated rigorously against the available test results. The validated FE models are adopted to perform a comprehensive parametric analysis by varying the cross-sectional geometries and the diameter-to-width ratio of the circular perforation. The parametric results are used to examine the accuracy of the current direct strength method (DSM) and the DSM proposed by other researchers in the literature on CFFSS tubular stub columns. The comparison of the strengths indicates the need for proposing specified design rules for the compression capacity of the perforated CFFSS stub columns. Accordingly, new design recommendations are proposed for DSM for accurate compression strength predictions for CFFSS tubular stub columns which are verified through reliability analysis.

Stability Evaluation of Different Oblique Lumbar Interbody Fusion Constructs in Normal and Osteoporotic Condition - A Finite Element Based Study.

Introduction: In developed countries, the age structure of the population is currently undergoing an upward shift, resulting a decrease in general bone quality and surgical durability. Over the past decade, oblique lumbar interbody fusion (OLIF) has been globally accepted as a minimally invasive surgical technique. There are several stabilization options available for OLIF cage fixation such as self-anchored stand-alone (SSA), lateral plate-screw (LPS), and bilateral pedicle screw (BPS) systems. The constructs’ stability are crucial for the immediate and long-term success of the surgery. The aim of this study is to investigate the biomechanical effect of the aforementioned constructs, using finite element analysis with different bone qualities (osteoporotic and normal). Method: A bi-segmental (L2–L4) finite element (FE) model was created, using a CT scan of a 24-year-old healthy male. After the FE model validation, CAD geometries of the implants were inserted into the L3–L4 motion segment during a virtual surgery. For the simulations, a 150 N follower load was applied on the models, then 10 Nm of torque was used in six general directions (flexion, extension, right/left bending, and right/left rotation), with different bone material properties. Results: The smallest segmental (L3–L4) ROM (range of motion) was observed in the BPS system, except for right bending. Osteoporosis increased ROMs in all constructs, especially in the LPS system (right bending increase: 140.26%). Osteoporosis also increased the caudal displacement of the implanted cage in all models (healthy bone: 0.06 ± 0.03 mm, osteoporosis: 0.106 ± 0.07 mm), particularly with right bending, where the displacement doubled in SSA and LPS constructs. The displacement of the screws inside the L4 vertebra increased by 59% on average (59.33 ± 21.53%) due to osteoporosis (100% in LPS, rotation). BPS-L4 screw displacements were the least affected by osteoporosis. Conclusions: The investigated constructs provide different levels of stability to the spine depending on the quality of the bone, which can affect the outcome of the surgery. In our model, the BPS system was found to be the most stable construct in osteoporosis. The presented model, after further development, has the potential to help the surgeon in planning a particular spinal surgery by adjusting the stabilization type to the patient’s bone quality.

Shear behavior of short headed studs in Steel-ECC composite structure

Engineering cementitious composite (ECC) is a promising candidate as the overlay material of orthotropic steel bridge deck (OSBD), to improve the durability and extend the service life. The mechanical performance of short headed stud connectors in steel-ECC composite structure has been limited studied. This study investigated the shear behavior of short headed studs embedded in ECC through experimental push-out tests and validated finite element (FE) analysis. The experimental and analytical results were analyzed accordingly in terms of shear strength, shear stiffness and failure mode. The push-out testing results showed that the existence of natural interfacial bond was beneficial for improving the initial stiffness of the specimen. The FE simulation results agreed well with the experimental ones. Base on the validated FE model, a parametric analysis was then conducted to investigate the influence of the stud diameter, stud height, stud strength, corrosion of stud, and compressive strength of ECC on the shear capacity of short headed studs. The analysis indicated that the diameter and tensile strength of headed stud had a significant improvement on the shear strength of headed studs, while the stud height and compressive strength of ECC exhibited the opposite trend. The corrosion of stud drastically reduced the shear performance of headed studs in terms of shear strength and ductility. It was also observed that AASHTO LRFD specification overestimated the shear strength of short headed studs embedded in ECC, while the Eurocode 4 and Chinese code were relatively conservative.

Experimental and numerical analysis on rectangular concrete-filled steel tubular columns with T-shaped stiffeners

Rectangular concrete-filled steel tubular (RCFST) columns are widely used in mega frame-core tube-outrigger truss super high-rise buildings, yet the local buckling of the steel tube may cause a large amount of waste on the steel material. In order to resolve this problem, this paper investigates the axial compression behavior of giant RCFST columns with T-shaped stiffeners by means of experimental and numerical analysis. Firstly, axial compression tests on 12 RCFST columns are conducted. The experimental results indicate that T-shaped stiffeners can improve the ultimate bearing capacity of RCFST columns, and the effect is more significant with the increase of the width-to-thickness ratio of the steel tube. However, T-shaped stiffeners have little effect on improving the ductility of axial compression members. Secondly, finite element (FE) models are established using ABAQUS and are verified against the experimental results. Subsequently, detailed parametric analysis and theoretical derivation are conducted based on the validated FE models. The results reveal the variation law of critical buckling stress and failure mode with respect to stiffness ratio. Finally, the design equations and procedures of T-shaped stiffeners in RCFST columns are obtained, by which the cross-section size of T-shaped stiffeners can be optimized, leading to a more economical design.

Numerical study on the flexural performance of RC beams with externally bonded CFRP sheets

The numerical investigations on the structural performance of reinforced concrete (RC) beam strengthened with externally bonded carbon fiber-reinforced polymer (CFRP) sheets are presented. The nonlinear characteristics of materials (i.e., stress-strain relationships of steel reinforcement, concrete, CFRP, and CFRP/concrete bond stress-slip behavior) were adopted in three-dimensional finite element (FE) models. The validation of FE models was conducted by comparing the laboratory works carried out on two RC beam specimens with 2000 mm length, 300 mm height, and 120 mm width. The numerical results show a good correlation with the experimental results of the beam specimens, such as load-displacement curves, crack patterns, and failure modes. They allow confirming the capability of the developed FE model to predict the flexural performance of strengthened beams considering CFRP/concrete interfacial behavior. Furthermore, parametric investigations were performed to determine the effect of flexural strengthening schemes, CFRP length with or without U-wraps, and multiple CFRP layers on the flexural performance of strengthened beams.

Failure analysis of metal-polymer-metal sandwich panels with wire mesh interlayers: Finite element modeling and experimental validation

Vacuum hot pressing of a thermoplastic core and metal skin sheets resistance welded to wire meshes is used to fabricate high interface strength metal-polymer-metal sandwich panels. The wire mesh strongly bonds with polymer core from material interlocking and it bonds with metal skin from welding. A finite element (FE) model is developed for characterizing the deformation behavior and failure of fabricated sandwich panels. While, a continuum ductile damage model is used to characterize failure of layers in stretching, a cohesive zone model is used to characterize interface failure. The FE model is validated using tensile tests, peel tests, double lap shear tests, and V-bending experiments. Good match is seen between simulations and experiments. In V-bending, spring back as well as debonding is correctly predicted. Sandwich panels fabricated in this work form an attractive alternative to adhesively bonded panels. The developed finite element model can be used for forming analysis of developed sandwich panels and for optimizing the panel architecture.

Finite element model for analysis of vibration damping characteristics of isotropic surface structures

In this paper, a finite element (FE) model was developed to predict the vibration response of isotropic beams, involving several modes of resonance. The cantilever beam model was employed in the FE model in line with Timoshenko’s bending theory. The FE analysis has been carried out using the modal analysis and harmonic analysis tools of Ansys R19.0. The FE model was subjected to a grid independence study to minimize the computational time without sacrificing accuracy. The resonant frequencies were utilized to compute the damping modulus of the material for both the FE and experimental results. The frequency response functions from the finite element analysis were compared with the experimental results of the cantilever beam subjected to impulse hammer excitation. Aluminium alloy AA6061-T6 was taken up as the homogeneous and isotropic beam material for both the experimental and the FE model. The effect of the magnitude and location of the excitation load, the geometry of the FE model on the vibration response was analyzed in detail. The FE model validation with the experimental results shows that the FE model is effective in predicting the damping response of any isotropic material.

Study on explosion-resistance performance of concrete-filled steel tubular columns considering the influence of elevated temperatures

Fire and explosion often occur together that seriously threatens the safety of engineering structures. In order to investigate the explosion resistance of concrete-filled steel tubular (CFST) columns at elevated temperatures, the finite element (FE) model of explosion resistance performance for circular CFST columns at elevated temperatures was established using the ABAQUS software. The fire and blast loads were simulated using ISO 834 standard fire and ConWep model, respectively. In the model, the static implicit and dynamic explicit analysis was coupled using “Restart” and “Import” commands and the strain-rate effect was considered. The experiment results of related literatures, including the temperature field, fire resistance duration and explosion resistance of CFST columns, were used to verify the feasibility of the method. Based on the validated FE models, the explosion mechanism of CFST columns subjected to standard fire was analyzed, including the failure modes, full-range analysis, development of stress and strain, interaction between steel tube and concrete and energy consumption. The influence of duration time, material strength, steel ratio and explosion equivalent on the explosion resistance were studied. The maximum mid-span deflection (Δpeak) was employed to quantitatively analyze the explosion-resistance performance of the CFST columns. The results show that shear failure firstly occurs at both fixed ends, and then the whole column presents flexural failure mode when subjected to explosion load under fire condition. With the increase of duration time, the proportion of energy consumption of steel tube decreases, and plastic deformation of concrete gradually becomes the main energy consumption mechanism. The concrete strength, explosion equivalent and axial load ratio have significant influence on the explosion resistance of CFST at high temperatures. After 0 min and 90 min fire duration, the explosion resistance is improved by approximately 21% and 42% respectively when the concrete cubic compressive strength increases from 30 MPa to 50 MPa.

Numerical investigation on RC T-beams strengthened in the negative moment region using NSM FRP rods at various depth of embedment

The application of Near Surface Mounted (NSM) method to strengthen reinforced concrete (RC) members in flexure through the use of Fiber Reinforced Polymer (FRP) rods has become a subject of interest to designers and researchers over the past few years. This technique has been extensively applied, and there is still a need for more experiments, analytical, and numerical studies to determine the effects of their parameters on the flexural performance of RC members. Therefore, a detailed 3D nonlinear finite element (FE) numerical model was developed in this study to predict the load-carrying capacity and the response of RC T-beams strengthened in the negative moment region accurately through the use of NSM FRP rods at different depth of embedment which are placed under three-point bending loading. The model was, however, designed with due consideration for the nonlinear constitutive material properties of concrete, yielding of steel reinforcement, NSM rods, and cohesive behaviors to simulate the contact between two neighboring materials. Moreover, the findings of the numerical simulations were compared with those from the experiments by other investigators which involve two specimens strengthened with NSM FRP rods added to one unstrengthened control specimen. The results, however, showed that the mid-span deflection responses of the predicted FE were in line with the corresponding data from the experiment for all the flexural loading stages. This was followed by the use of the validated FE models to analyze the effect of several properties of the FRP materials to provide more information than the limited experimental data available. It was discovered that the FE model developed is appropriate to be applied practically and economically with more focus on the parametric studies based on design to precisely model and analyze flexural negative moment strengthening for the RC members through the use of NSM FRP rods.

Accurate prediction of cyclic hysteresis behaviour of RBS connections using Deep Learning Neural Networks

Reduced Beam Section (RBS) connections have been widely used to improve the seismic performance of steel framed buildings by providing a seismic fuse mechanism. While in general the modified-Ibarra–Krawinkler (mIK) model can reliably capture the cyclic hysteresis behaviour of fully welded RBS connections, there is currently no reliable or accurate method available to predict the parameters which define this model without appropriate experimental or finite element (FE) tests of full scale models of the RBS connection for calibration purposes. This paper presents, for the first time, an accurate method of predicting the mIK parameters using a number of different deep learning Neural Networks through a logical process to provide accurate predictions of the required parameters based on the geometrical dimensions of the steel beam and RBS. The proposed networks are trained based on the database of 1480 experimentally validated FE models. First, the cyclic moment–rotation-hysteresis results from the selected database are calibrated with simple equivalent beam representations in the OpenSees software. Then a number of different deep learning Neural Networks are developed to predict each of the seven key parameters which define the mIK spring model. Finally, a Matlab toolbox is developed to predict the mIK parameters for any steel beam and RBS geometry without the need for complex and time consuming full scale cyclic experimental tests or FE analyses. It is shown that the developed tool box provides over 96% accuracy in predicting the key design parameters and therefore should prove useful in the preliminary design and assessment of steel RBS frames.

Normalized vertebral-level specific range of motion corridors for female spines in rear impact

Objective It is well known that the biomechanical responses of female and male spines are different in rear impacts. Female-specific finite element models are being developed as improvements over generic models. Such advancements need female-specific segmental responses for validation. The objectives of the study were to develop vertebral level-specific range of motion corridors from female human cadaver head-neck complexes exposed to rear impact loading. Methods Previously conducted experiments from five human cadaver head-neck complexes were used in this analysis-based study. Briefly, the female head-neck complexes were isolated at the second thoracic vertebral level from the whole body such that the skin and the surrounding tissues of the osteoligamentous complex were intact. The distal end was fixed to the platform of a min-sled testing device. The anterior angulation of T1 was at 25 degrees with respect to the horizontal axis to simulate the normal driver posture. The occipital condyles were directly superior to the T1 body, and the Frankfort plane was horizontal. Rear impact loading were applied at a velocity of 2.6 m/s. The range of motion was defined as the inter-segmental angle at each level of the subaxial spinal column, and it was obtained by tracking the motion of the retroreflective targets that were secured on vertebral bodies and lateral masses of C2 through C7 vertebrae. Data were normalized with respect to the fifth percentile female total body mass, and corridors were developed using the equal stress equal velocity approach and expressed as mean ± 1 standard deviation corridors for each segment. Results The segmental motions of the subaxial cervical spinal column were such that the upper regions responded with flexion while the lower regions responded with extension during the initial accelerative loading phase of the impact, resulting in a non-physiological curvature. During the later phase, all segments were in extension. individual corridors are presented as temporal responses in the body of the manuscript. A comparison of the mean temporal responses at each segment are presented to depict the angulation motion differences within the spinal column. Conclusions The present corridors are unique to the female spines. Because female spines have significantly (p < 0.05) different biomechanical responses when compared to male spines, local anatomical differences exist between male and female spines, and field data and clinical studies show female bias to whiplash associated disorders under the rear impact of loading, the present set of corridors serve as a fundamental dataset for the validation of female-specific finite element models. Current computational models can also use these corridors for improved validation to add confidence in their outputs.

Intracranial Displacement Measurements Within Targeted Anatomical Regions of a Postmortem Human Surrogate Brain Subjected to Impact

The dynamic response of the human brain subjected to impulsive loading conditions is of fundamental importance to the understanding of traumatic brain injuries. Due to the complexity of such measurements, the existing experimental datasets available to researchers are sparse. However, these measurements are used extensively in the validation of complex finite element models used in the design of protective equipment and the development of injury mitigation strategies. The primary objective of this study was to develop a comprehensive methodology to measure displacement in specific anatomical regions of the brain. A state-of-the-art high-speed cineradiography system was used to capture brain motion in post-mortem human surrogate specimens at a rate of 7500fps. This paper describes the methodology used to capture these data and presents measurements from these tests. Two-dimensional displacement fields are presented and analyzed based on anatomical regions of the brain. These data demonstrated a multi-modal displacement response in several regions of the brain. The full response of the brain consisted of an elastic superposition of a series of bulk rotations of the brain about its centre of gravity. The displacement field could be linked directly to specific anatomical regions. The methods presented mark an improvement in temporal and spatial resolution of data collection, which has implications for our developing understanding of brain trauma.

Behavior of screw connections in sheathed cold-formed steel walls

This paper presents a study on the behavior of screw connections in sheathed cold-formed steel (CFS) walls. A finite element (FE) model with solid elements was developed to investigate different failure modes. Suitable solution techniques, element types, mesh sizes, screw modeling, and geometric and material non-linearity were considered in model development. Since the behavior of the sheathing boards is similar to that of other quasi-brittle materials, the Concrete Damage Plasticity (CDP) model was used to model the material behavior using both classical plasticity and continuum damage mechanics. Uniaxial experimental tests were performed on fiber-cement board samples to define material parameters used in the CDP model. The load displacement behavior, ultimate strength, and failure modes obtained from the developed FE model were validated against available experimental results on walls sheathed with cement or gypsum boards. The validated FE model was then used to perform parametric study to investigate the effect of different design parameters on the connection behavior. These parameters are: board type and thickness, CFS profile thickness, screw diameter, screw length, and edge distance. The results of the parametric study were used to develop a design equation for the screw connection strength using nonlinear regression analysis.