Two novel hybrid materials for use in sandwich cores of structural materials are designed, manufactured and mechanically tested. Each material is a hybrid of metal and polymer foam. One set of hybrids is fabricated using an aluminium micro-truss filled with varying densities of polyurethane foam. Increases up to 120% in stiffness, 372% in strength, 740% in resilience and 106% in impact energy over the aluminium micro-truss are obtained from compression and impact testing. Furthermore, the stiffness of these hybrids can be tailored according to the density of the polyurethane foam. Another set of hybrids is fabricated using a rapid prototyped ABS polymer truss that is foamed and electroplated with nanocrystalline nickel. Increases up to 1525% in stiffness, 1165% in strength and 650% in energy absorption over the foamed ABS truss are obtained. Furthermore, the gain in strength, stiffness and energy absorption outweigh the gain in density in these hybrid materials.

Two novel hybrid materials for use in sandwich cores of structural materials are designed, manufactured and mechanically tested. Each material is a hybrid of metal and polymer foam. One set of hybrids is fabricated using an aluminium micro-truss filled with varying densities of polyurethane foam. Increases up to 120% in stiffness, 372% in strength, 740% in resilience and 106% in impact energy over the aluminium micro-truss are obtained from compression and impact testing. Furthermore, the stiffness of these hybrids can be tailored according to the density of the polyurethane foam. Another set of hybrids is fabricated using a rapid prototyped ABS polymer truss that is foamed and electroplated with nanocrystalline nickel. Increases up to 1525% in stiffness, 1165% in strength and 650% in energy absorption over the foamed ABS truss are obtained. Furthermore, the gain in strength, stiffness and energy absorption outweigh the gain in density in these hybrid materials.

This study investigates the possibility of fabricating periodic cellular materials (PCMs) via the lost foam casting (LFC) process using aluminum alloy A356 and magnesium alloy AZ91. This approach combines the structural efficiency of PCM architectures with the processing advantages of near-net-shape LFC. An initial feasibility study fabricated corrugated A356 panels. This was followed by a study of casting variables such as pattern design, vacuum assistance, and alloying additions in order to improve the fillability of the small cross-section struts. Finally, integrated pyramidal sandwich panels having different relative densities were subjected to artificial aging treatments and subsequently tested in uniaxial compression. The A356 PCMs experienced a continuous increase after yielding while the AZ91 PCMs exhibited strut fracture after peak strength. The results showed the compressive yield strengths of this study are comparable with those previously reported PCMs produced by different fabrication methods.

Fibre composite materials are gaining recognition in civil engineering applications as a viable alternative to traditional materials. Their migration from customary automotive, marine, aerospace and military industries into civil engineering has continued to gain momentum over the last three decades as new civil engineering applications develop. The use of fibre composite materials in civil engineering has now evolved from non-structural applications, such as handrails and cladding, into primary structural applications such as building frames, bridge decks and concrete reinforcement. However, there are issues which are slowing the use of fibre composite materials into civil engineering. Issues include high costs, difficulties in realising potential benefits, general lack of civil engineers' familiarity with the material and relatively little standardisation in the composites industry. For composites to truly offer a viable alternative to traditional construction materials in the civil engineering marketplace, it is essential that these issues be addressed. It is proposed that this situation could be improved by demonstrating that potential benefits offered by composites can be achieved with familiar civil engineering forms. These forms must be well suited to fibre composite materials and be able to produce safe and predictable civil engineering structures with existing structural engineering methods. Of the numerous structural forms currently being investigated for civil engineering applications, the truss form appears particularly well suited to fibre composites. The truss is a familiar structural engineering form which possesses certain characteristics that make it well suited to fibre composite materials. In this research a novel monocoque fibre composite truss concept was developed into a working structure and investigated using analytical and experimental methods. To the best of the author's knowledge the research presented in this thesis represents the first doctoral research into a structure of this type. This thesis therefore presents the details of the development of the monocoque fibre composite (MFC) truss concept into a working structure. The developed MFC truss was used as the basis for a detailed investigation of the structural behaviour of the MFC truss elements and the truss as a whole. The static structural behaviour of the principal MFC truss elements (tension members, compression members and joints) was investigated experimentally and analytically. Physical testing required the design and fabrication of a number of novel test rigs. Well established engineering principles were used along with complex finite element models to predict the behaviour of the tested truss elements and trusses. Results of the theoretical analysis were compared with experimental results to determine how accurately their static structural behaviour could be predicted. It was found that the static structural behaviour of all three principal truss elements could be accurately predicted with existing engineering methods and finite element analysis. The knowledge gained from the investigation of the principal truss elements was then used in an investigation of the structural behaviour of the MFC truss. Three full-scale MFC trusses were fabricated in the form of conventional Pratt, Howe and Warren trusses and tested to destruction. The investigation included detailed finite element modelling of the full-scale trusses and the results were compared to the full-scale test results. Results of the investigation demonstrated that the familiar Pratt, Howe and Warren truss forms could be successfully manufactured with locally available fibre composite materials and existing manufacturing technology. The static structural behaviour of these fibre composite truss forms was accurately predicted with well established engineering principles and finite element analysis. A successful marriage between fibre composite materials and a civil engineering structure has been achieved. Monocoque fibre composite trusses have been developed in the familiar Pratt, Howe and Warren truss forms. These structures possess characteristics that make them well suited to applications as primary load bearing structures.

Master of Science / Department of Civil Engineering / Hani G. Melhem / The Abilene & Smoky Valley Railroad Association offers train excursions to sightseers wishing to see historic Abilene and natural Kansas scenery. Currently, a diesel powered ALCO locomotive is used to pull the passenger cars. They wish to use a 1919 Baldwin steam locomotive in the future. Part of the excursion includes a slow crossing of the Smoky Hill River over a two-span steel truss bridge. The company approached the Kansas State University Civil Engineering Department with the task of performing a structural check of the bridge. By using the Baldwin locomotive, the bridge is required to support much larger loads than when the diesel engine is used. First, a basic visual inspection and site visit of the bridge was performed. The inspection was not thorough, but was used to familiarize the team with the bridge and its components. Using the inspection and data supplied, a structural analysis was performed using the software, RISA. After completion of the analysis for both loading situations, the resulting stress increases were calculated. Other calculations performed include buckling loads of the compression members, deflections of the bottom chord and stresses in some of the connections. After completion of the analysis and calculations, large increases in member stress were found. For most of the members, the increase of live loads stress was between 80% and 100%. The largest stress found due to the dead and live load, which was under 15 ksi, occurred in the bottom chord for the steam locomotive loading situation. Some truss members experienced stress reversal, but relatively low values were noted. Deflection calculations for the two loading situations yielded similar results to the stress calculations. Again, an increase in deflection between 80% and 100% was found for the joints located on the bottom chord. It is recommended that a more detailed inspection and a more thorough analysis of the connections, supports, piers, and foundations be performed before the heavier locomotive is used.

An arched structure provides an effective load carrying system for large span structures. When it comes to long span roof structures, timber arches are one of the best solutions from both structural and aesthetical point of view. Glulam arched structures are often designed using slender elements due to economic consideration. Such slender cross-section shape increases the risk of instability. Instability analysis of straight members such as beam and column are explicitly defined in Eurocode. However, for instability of curved members no analytical approach is provided in the code, thus some numerical method is required. Nonetheless, an approximation is frequently used to obtain the effective buckling length for the arched structures in the plane of arches. In this master thesis a linear buckling analysis is carried out in Abaqus to obtain an optimal effective buckling length both in-plane and out-of-plane for circular glulam arched structures. The elastic springs are used to simulate the overall stiffness of the bracing system. The results obtained by the FE simulations are compared with a simple approximation method. Besides, the forces acting on the bracings system is obtained based on 3D geometric nonlinear stress analysis of the timber trusses. Our findings conclude that the approximation method overestimates the effective buckling length for the circular glulam arched structures. In addition, the study indicates that the position of the lateral supports along the length of the arch is an important design aspect for buckling behaviour of the arched structures. Moreover, in order to acquire an effective structure lateral supports are needed both in extrados and intrados. Furthermore, instead of using elastic spring elements to simulate the overall stiffness of the bracing system, a full 3D simulation of two parallel arches was performed. It was shown that the springs are stronger than the real bracing system for the studied arch.

The subject of the master thesis is the design and assessment of the supporting roof steel structure on the building, which will be used for various sports events in Znojmo. The building has a rectangular floor plan with dimensions of 50 x 60 m. The height at the top is 15 m. The trusses are articulated on concrete columns. Structure stability ensures system of bracings. The work contains a static calculation of the main load-bearing elements, including the relevant joints. The roof and cladding consist of sandwich panels.

The subject of this thesis is the conversion and alternative proposal to the existing steel structure roofing the winter stadium in Jindrichuv Hradec. The building has a rectangular plan with dimensions of 80 x 52 m. The roof structure consists of lattice trusses and purlins, plotted using lattice steel columns. The other possibilities are parabolic lattice trusses and purlin with fly bracing that were designed and evaluated in accordance with applicable standards. The solution using parabolic trusses is designed on the original footprint of the structure. The distance of each bond is 8 m.

Historic truss bridges are examined in this thesis through material characterization of wrought iron and structural evaluation of an early 20th century pony truss bridge. The mechanical properties of wrought iron from six 19th century truss bridges were evaluated through mechanical testing that includes hardness and tension tests. The main findings of this work are: 1) That hardness is a poor predictor of yield and ultimate stress but has some ability in screening iron for iron with low ductility, 2) there is a statistically significant difference in the distribution of yield and ultimate stresses between material samples from different bridges, and 3) that a size effect is present in the material that results in lower yield and ultimate stresses for larger members. Load tests were conducted on an early 20th century pony truss bridge where member axial strains and truss deflections are measured, which were then simulated in computer models. The key observations are: 1) that connection type between truss members has little effect on computer model results, 2) that a significant difference was observed between measured axial forces and those predicted in the computer models for certain members, and 3) that although the bridge response is best modeled with a pin-roller support condition, compressive forces measured in the bottom chord members from temperature change indicate the supports have some lateral resistance, thus are not a true pin-roller.

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