This thesis presents the results of research on sandwich panel construction, with the aims of developing tools for modelling sandwich panel fire performance and hence to use the tools to aid the development of sandwich panel construction with improved fire resistance. The research focuses on sandwich panels made of thin steel sheeting and a polyisocyanurate (PIR) foam core. For non-loadbearing sandwich panel construction, fire resistance is measured in terms of thermal insulation and integrity only. However, these two parameters are affected by mechanical performance of sandwich panel construction due to the high distortion and large deformation nature of sandwich panel construction under fire attack. Therefore, it is necessary to consider both thermal and mechanical performances of sandwich panels under fire conditions. The work in this thesis includes development of a thermal conductivity model for PIR foam as this thermal property is one of the key values in determining heat transfer through sandwich panels; this thermal conductivity model is based on the effective thermal conductivity of porous foams proposed by Glicksman (1994) and includes the effects of polymer decomposition and increases in foam cell size. It is validated against fire tests carried out on PIR sandwich panels 80mm and 100mm thick with steel facings of thickness 0.5mm. A large 3D sequentially coupled thermal-stress model of a full scale fire test has been developed in the commercial finite element analysis (FEA) software ABAQUS to provide insight into the way sandwich panels behave in a fire resistance test and also to assess different modelling techniques. Aspects and stages of the simulation that agree well with test data are explained. Limitations of the ABAQUS software for simulating sandwich panel fire tests are highlighted; namely, it is not possible to simulate the correct radiation heat transfer through panel joints, as cavity radiation cannot be specified in a fully coupled thermal-stress analysis. Joints are key components of sandwich panel construction. In order to obtain temperature development data for modelling joints, a number of fire tests have been carried out. These fire tests were conducted with different joint configurations and panel thicknesses under realistic fire conditions using timber cribs. The joint fire tests revealed significant ablation of the foam core within the joints of sandwich panels at high temperatures. At the beginning of fire exposure, the joint temperature on the unexposed surface was lower than that on the panel due to the better insulation property of air compared to the foam. However, as the joint gap increased due to ablation of the foam, the joint temperatures became higher than in the panel. A numerical simulation model has been created to investigate this behaviour. Using the aforementioned thermal model, numerical simulations have been carried out to examine the influences of possible changes to sandwich panel design on sandwich panel construction fire performance. It was suggested that if the maximum gap in the joints can be limited to 5mm, for example, by applying intumescent coating strips within the sandwich panel joints to counter the increasing gap formed due to core ablation, then the joint temperature on the unexposed surface would not exceed that of the panel surface, hence the joint would cease to be the weak link. To increase the panel fire resistance, the use of graphite particles in the PIR foam formulation may be considered to lower the contribution of radiative heat transfer within the foam cells by reducing the transmissivity of the cell walls. Graphite particles may offer considerable increases in the thermal resistance of PIR foam at high temperatures by limiting the radiation contribution which dominates heat transfer above 300oC.

This thesis presents the results of an experimental, numerical and analytical study to develop a design method to calculate punching shear resistance for a new shearhead system between tubular steel column and reinforced concrete flat slab. This shearhead system enables two of the most popular structural systems, i.e. reinforced concrete flat slab floor and steel tubular column, to be used to produce efficient structures of low cost and short construction time. This research investigates slabs without and with a service hole adjacent to the column. The new shearhead system should not only possess sufficient punching shear resistance, but should also be efficient for construction. The main methodology for this project was based on numerical finite element simulations verified by two full scale tests. These two tests were carried out in the University of Manchester's Structural Testing Laboratory. The two specimens had the same slab size, thickness and reinforcement ratio, but differed in the column shape (rectangular or circular), central reinforcement arrangement (continuous or discontinuous), shearhead position in the slab thickness and shearhead fabrication arrangement. Recorded load-deflection and load-strain relationships, crack development and critical perimeter were used for detailed validation of using the commercial finite element software ABAQUS. The validated ABAQUS model was used to conduct a comprehensive parametric study to investigate the effects of a number of design parameters, including the effect of varied column size, shearhead arm length, shearhead arm cross section, shearhead arm angle, amount of flexural reinforcement, slab thickness, shearhead positions and hole positions. The main conclusion from the parametric study was that the shearhead system could be treated as an enlarged column in normal flat slab structure. The parametric study enabled pressure distribution below the shearhead arms to be approximated for checking whether the shearhead arms would be sufficient for the enlarged column assumption to be valid. The parametric study results were also used to determine the effective depth of the flat slab and critical punching shear perimeter of the slab with and without a service hole.Using the enlarged column assumption, the punching shear resistance of all structures used in the parametric study were re-calculated using Eurocode 2 (EC2), British stand 8110 (BS8110) and American Concrete Institute code 318 (ACI 318). Comparison of calculation results using these three design methods indicates that both EC2 and BS8110 predicted very close value which reached very good agreement with the ABAQUS simulation (normally within 10%). Among these three design methods, ACI 318 was the only code that explicitly considered shearhead system. ACI 318 was not able to predict the slab critical perimeter length with good accuracy, however, its prediction of slab punching shear resistance achieved reasonably good agreement with numerical analysis results and were on the safe side. Based on these studies, a design method for calculating punching resistance of the proposed shearhead system between reinforced concrete flat slab and steel tubular column has been developed in this thesis.

The invention of mass timber products, including cross laminated timber (CLT), over the past two decades has made tall wood building possible. In CLT structures, angle brackets are commonly used in wall-to-floor connections to transfer the shear in seismic and wind loads. In reality, these connections could experience loads in various directions, as well as multi-directional forces. This research consists of two parts: an experimental study carried out in Part 1, followed by a numerical program completed in Part 2. The research aims to investigate the performance of wall-to-floor CLT angle bracket connections under various loading situations. In Part 1 of the research, a two-phase experimental program consisting of 12 monotonic tests in the first phase, and 24 monotonic and 24 cyclic tests in the second phase was conducted to investigate the behaviour of wall-to-floor CLT angle bracket connections. Connections were assembled using two different sizes of steel angle brackets and four types of fasteners, under uplift, in-plane shear, and out-of-plane shear loads. The performance of the connections was evaluated in terms of strength, stiffness, ductility, energy dissipation capacity, and failure modes. Results show that small diameter fasteners are more desirable for wood-to-wood angle bracket connections in terms of failure modes, load-bearing capacity and stiffness. Specimens exhibited considerable ductile performance under both uplift and in-plane shear loads due to combinations of yielding of brackets and yielding or pull-out of screws. Connections loaded under out-of-plane tension may fail in the splitting of CLT panels. Fully-threaded screws led to higher strength, stiffness and energy dissipation capacity but less ductility compared to partially-threaded screws in angle bracket connections. In Part 2 of the research, a two-phase numerical program was carried out to assess the coupling effect of biaxial loading on the performance of CLT wall-to-floor angle bracket connections. In Phase I, a 3D finite element model of connections was developed using ABAQUS software and verified with the data from experimental tests carried out in Part 1 of the research. In Phase II of the numerical program, the verified model was used to simulate the performance of connections under three biaxial loads, i.e., shear and in-plane uplift, shear and out-of-plane tension, and shear and out-of-plane compression. The coupling effect on the performance of the connections was evaluated in terms of strength, stiffness, ductility, and failure modes under biaxial loads, and compared with the scenario where the connection was only loaded in shear. Results show that the application of biaxial loading may considerably decrease the shear performance of the connections. Additionally, the results confirm the analytical equation suggested by the European Technical Assessment to predict the resistance of angle bracket connections under biaxial loads. / Graduate / 2022-08-04

<p>Results of stability analyses with the commercial finite element program ABAQUS are presented. Buckling and nonlinear analysis of an Euler column and a Von Mises truss are presented. In addition, linear, buckling and nonlinear analyses are carried out on a Varax dome.</p> / Master of Science

Safety is an important aspect when designing bridges and roads. One aspect among others to consider is the road restraint systems. The focus of this study was centered to safety barriers which are the vehicle parapets/guardrails. The parapet must meet certain requirements specified in European Standard in order to obtain a CE-marking, indicating the acceptance of use. Full-scale test must be performed for a proposed parapet to evaluate the performance. Often several full-scale tests are performed in order to achieve CE-marking, making it an expensive process. The primary objective of this master thesis was to investigate if Abaqus/Explicit could be used as the finite element software for simulation of crashes. Secondary objective was to investigate how well a performed full-scale crash could be simulated in Abaqus/Explicit. A full-scale test was conducted and the parapet installation and vehicle used was modeled. Same conditions as in the full-scale were used in the simulation. The results indicated that it is possible to simulate the full-scale crash using Abaqus/Explicit. However, the behavior of the full-scale test was not completely captured. The maximum dynamic and permanent horizontal deflection of the tabular thrie beam in the full-scale test was 582 mm and 515 mm, corresponding value from the simulation was 703 mm and 643 mm. The conclusion from the results is that Abaqus/Explicit is a suitable finite element software for simulating crashes. The differences between the full-scale test and the simulations in this master thesis were due to the simplifications and assumptions used when modeling the parapet, bridge deck and the vehicle. The overall global behavior of the full-scale test was not captured, however the simulation results were not far from the full-scale test even though rough simplifications and assumptions were used in the modeling. We believe that with more care to details in modeling, it should be possible to have better convergence between simulation and the full-scale test.

This thesis examines the influences of five factors on the strain energy at failure of metallic alloy plates during a shock wave impact. The five factors are material type, initial damage, boundary conditions, plate thickness, and plate temperature. The finite element simulation matrix was developed using a statistical design of experiments (DOE) technique. The Eulerian hydrocode CTH was used to develop the pressure histories that were input into the finite element code Abaqus/Explicit, which implemented the Mississippi State University internal state variable (ISV) plasticity-damage model (DMG). The DMG model is based on the Bammann-Chiesa-Johnson (BCJ) ISV plasticity formulation with the addition of porosity and the void nucleation, growth, and coalescence rate equations that admit heterogeneous microstructures. Material type and thickness were the primary influences on the strain energy at failure, and the materials studied, magnesium and aluminum, showed two different failure mechanisms, tearing at the boundaries and spalling, respectively.

Most studies on blast explosion focus on a single technique or software. This Thesis directly compares several methods of simulating blast loads using LS-DYNA, ABAQUS and CTH software. The techniques appraised in this thesis include; Jones-Wilkins-Lee (JWL) equation of state (EOS), spherical incident wave formulation, and a direct planar blast load application. In the first section of this study, we analyzed a free air-blast generated by detonating 100 g of composition-4 (C-4). Next, we placed and examined the lower extremity model under the same blast parameters in different coupled and uncoupled scenarios. In the free air-blast study, all three codes gave similar results. The peak over pressure from ABAQUS was the closest in value to the experimentally measured data. In the second section, the JWL EOS method consistently produced higher-pressure response in the lower extremity elements compared to the other methods implemented.

Sheet trimming is an important forming operation in stamping industry. However, trimming of automotive magnesium sheet materials is not well understood. The objective of present study was to investigate the trimming behavior of AZ31 and ZEK100 automotive magnesium sheet materials using a laboratory-based experimental set-up and complementary finite element (FE) simulations of the lab-based experiments. The effects of the trimming process parameters that included tool setup configuration, punch speed, clearance, sheet thickness and sheet orientation (rolling and transverse directions) on the quality of trimmed edge were analyzed. Experimental results indicated that the trimmed edge quality depended strongly on the trimming conditions. The optimal trimming parameters for AZ31 and ZEK100 sheets were experimentally obtained. Interrupted trimming experiments were conducted to examine crack initiation and development, the mechanism of fracture, and the generation of the fracture profile of the trimmed edges. The R-value as a measure of material anisotropy and fracture strain of both materials were measured using uniaxial tension and plane strain tests and incorporated in the FE model. General purpose Finite Element software ABAQUS/Explicit was employed to simulate the trimming process where five different fracture criteria and element deletion method were used to predict profile of trimmed edge and the fracture initiation and development during the trimming process. Good general agreement was observed between experiments and FE simulations. However, some discrepancies were also observed. These are presented and discussed in the thesis. / Thesis / Master of Applied Science (MASc)

The development of a numerical modelling approach for carbon bre reinforced plastic energy absorbing structures designed for crash events using Abaqus/CZone is described within this master thesis. Several crash tube series have been designed, manufactured, and tested with a rather unconventional cross-sectional geometry. The squared cross-sectional geometry consisted of "curved" at sections, and double flanges for adhering two halves together. The crash tube halves contain carbon bre epoxy UD laminates, and are manufactured using a hot-press machine. Adjustments for experimental tests were made in the geometry, laminate denition, and impact velocity. Numerical simulations were focused on geometry, laminate definition, impact velocity, flange geometry, material model, laminate thickness, and crush properties. The numerical model consisted of two parts, namely a 3D discrete rigid planar shell as impactor plate without material properties, and a 3D shell crash tube with an imported geometry from Dassault Systems CATIA V5. Material, and cohesive properties were assigned to the crash tube using the Abaqus Ply Fabric material model, and CZone. Mesh seed length was smaller than the critical mesh seed length. An initial clearance between the impactor and crash tube has been implemented within the assembly. Step size was set to 0.05 s, and dynamic explicit step type was selected. General contact was defined using default settings. A qualitative good agreement between numerical and experimental test results is achieved for V100, V500, V600, and V700 series with c.o.v. values for stroke length of 2.2%, 7.0%, 5.3%, and 4.1%,respectively. V500-V700 series are only tested once, whilst the V100 series has been tested five times. The V200 and V300 series with modified geometries achieved c.o.v. values within a complete different order of magnitude for stroke length, namely 14% for V200 series, and 15% for V300 series. Although only three specimens have been tested for the V200, and V300 series, it is not the main reason for this mismatch. The starting deceleration at the linear increasing segment is much lower than observed in experiments, and causes this major difference. Elevated impact velocities for the V1502, and V1503 series tend to have a positive influence on the numerical results, and ensure a higher initial starting deceleration at the linear increasing segment. Numerical results show that increased taper ratios result in decreased decelerations. A flange geometry study showed that implementing a double flange suppresses debonding, and increases the deceleration, as the geometrical stiffness is increased. Not having a flange results in lower decelerations, and larger stroke lengths, as the geometrical cross-section provides less stiffness. A bonded single flange will be debonded, independent of bonding properties, as even extremely high bonding properties have shown direct debonding under impact load. Stiffer laminates result in higher decelerations and shorter stroke lengths. This statement is tested in three different ways, namely by changing the laminate denitions, laminate thickness's, and the crush properties. Three different material models have been tested. Abaqus Ply Fabric has proven to be easiest in usage, and showing a qualitative good agreement with the experimental results. Abaqus Ply Fabric does over predict the stroke length, whereas Hashin, and Tsai-Wu achieve a more accurate stroke length prediction. However, it is safer to over predict the stroke length. No material model is capable of capturing the initial peek decelerations.

Seismic pressures on displacing or rigid retaining or basement walls have been derived based on the original work of Mononobe and Okabe, who used a shake table to calculate dynamic pressures of displacing retaining walls existing in cohesionless soils. Since this original work was done over eighty years ago, the results of Mononobe and Okabe, colloquially known as M-O theory, have been applied to different conditions, including non-displacing basement walls, as well as changes in soil properties. Since the original work of M-O, there have been numerous studies completed to verify the accuracy of the original calculation, most notably the work of Seed and Whitman (1970), Wood (1973), Sitar (Various), and Ostadan (2005). This has resulted in varying opinions for the accuracy of M-O theory, whether it is grossly unconservative or conservative, as well as its effectiveness for situations where the wall does not displace enough to engage active soil conditions. This study examines (3) different wall cases, a cantilever retaining wall, gravity retaining wall, and rigid basement wall, through an implcit finite element analysis, under simple sinusoidal boundary accelerations. The soil is modeled using the Drucker-Prager model for elastic-plastic properties. The dynamic pressure increment is observed for different driving frequencies, with the anticipation that an in-phase and out of phase response between the soil and structure will be achieved, resulting in both lower and higher than M-O pressure values.