No description available.

Numerical model usage has substantially increased in many industries. It is the aerospace industry that numerical models play possibly the most important role for development of optimum design. However, numerical models need experimental verification. This experimental verification is used not only for validation, but also updating numerical model parameters. Verified and updated models are used to analyze a vast amount of cases that structure is anticipated to face in real life. In this thesis, structural finite element model updating of a utility helicopter fuselage was performed as a case study. Initially, experimental modal analyses were performed using modal shakers. Modal analysis of test results was carried out using LMS Test.lab software. At the same time, finite element analysis of the helicopter fuselage was performed by MSC.Patran &amp / Nastran software. v Initial updating was processed first for the whole helicopter fuselage then, tail of the helicopter was tried to be updated. Furthermore, a new method was proposed for the optimum node removal location for getting better Modal Assurance Criterion (MAC) matrix. This routine was tried on the helicopter case study and it showed better performance than the Coordinate Modal Assurance Criterion (coMAC) that is often used in such analyses.

No description available.

No description available.

A new modular steel floor system, named FastFloor, is proposed for commercial buildings. The system is conceptualized to be prefabricated at the shop and ready to be installed on a previously erected skeleton frame structure consisting of girders and columns or connected to core shear walls. The system configuration aims to increase the speed of design, fabrication, and erection of a steel project by eliminating concrete pouring and curing times. Other advantages include reducing the weight of the building and its carbon footprint. Several module configurations were considered and evaluated based on a series of interviews with experts in steel fabrication and erection engineering. The selection relied not only on addressing the issues related to fabrication, transportation, and erection but also on satisfying floor vibrations, as it was determined to be the governing limit state of the plate thickness, section sizes, and beam spacing due to the presence of an unstiffened bare plate acting as a slab. Observations were performed regarding fabrication sequence and transportation on the chosen configuration. The dynamic properties of the module are particularly important because DG11 was developed for composite concrete-steel floor systems, and its applicability to all steel-floor systems needs to be evaluated. In parallel, a vibration testing program was conducted to determine the dynamic properties of the module, including natural frequencies and mode shapes. Lastly, the acceptability of the modular system for floor vibrations was evaluated by both a calculation method and a modeling approach. The analysis results suggest that the module will not satisfy floor vibrations criteria, but a modified module with added stiffeners is shown to be acceptable. Upcoming tests, by others, on specimens with a raised access floor will be necessary to refine the predictions and determine if the stiffeners are actually required. / Master of Science / FastFloor is an innovative modular all-steel floor system that aims to revolutionize the construction of commercial buildings, with benefits including enhanced efficiency in design, fabrication, and erection, as well as reduced environmental impact, by eliminating the need for concrete pouring and curing and full prefabrication in shops. Several module configurations were evaluated based on insights from industry experts in steel fabrication and erection engineering. It was observed that the main challenge in the early phases was to address issues related to fabrication, transportation, and erection while ensuring optimal performance in terms of floor vibrations. This thesis project focused on a preliminary assessment of the vibration behavior of the system by conducting dynamic tests and evaluating the compatibility with the analytical and computational procedures in Design Guide 11, which is not calibrated for an all-steel system like FastFloor. Based on the results, it was concluded that the initial configuration did not fully satisfy the floor vibrations criteria. However, through further computational evaluation, a modified module, based on the initial configuration with added stiffeners, was predicted to be satisfactory. Thus, future research will continue to refine the system behavior and predictions and evaluate the contributions of Raised Access Floor to the vibration performance.

Existing methods of evaluating the structural system of a building after a seismic event consist of removing architectural elements such as drywall, cladding, insulation, and fireproofing. This method is destructive and costly in terms of downtime and repairs. This research focuses on removing the guesswork by using forced vibration testing (FVT) to experimentally determine the health of a building. The experimental structure is a one-story, steel, bridge-like structure with removable braces. An engaged brace represents a nominal and undamaged condition; a dis-engaged brace represents a brace that has ruptured thus changing the stiffness of the building. By testing a variety of brace configurations, a set of experimental data is collected that represents potential damage to the building after an earthquake. Additionally, several unknown parameters of the building’s substructure, lateral-force-resisting-system, and roof diaphragm are determined through FVT. A suite of computer models with different levels of damage are then developed. A quantitative analysis procedure compares experimental results to the computer models. Models that show high levels of correlation to experimental brace configurations identify the extent of damage in the experimental structure. No testing or instrumentation of the building is necessary before an earthquake to identify if, and where, damage has occurred.

Design space exploration (DSE) is a tool used to evaluate and compare designs as part of the design selection process. While evaluating every possible design in a design space is infeasible, understanding design behavior and response throughout the design space may be accomplished by evaluating a subset of designs and interpolating between them using surrogate models. Surrogate modeling is a technique that uses low-cost calculations to approximate the outcome of more computationally expensive calculations or analyses, such as finite element analysis (FEA). While surrogates make quick predictions, accuracy is not guaranteed and must be considered. This research addressed the need to improve the accuracy of surrogate predictions in order to improve DSE of structural responses. This was accomplished by performing comparative analyses of linear and nonlinear dimensionality-reduction-based radial basis function (RBF) surrogate models for emulating various FEA nodal results. A total of four dimensionality reduction methods were investigated, namely principal component analysis (PCA), kernel principal component analysis (KPCA), isometric feature mapping (ISOMAP), and locally linear embedding (LLE). These methods were used in conjunction with surrogate modeling to predict nodal stresses and coordinates of a compressor blade. The research showed that using an ISOMAP-based dual-RBF surrogate model for predicting nodal stresses decreased the estimated mean error of the surrogate by 35.7% compared to PCA. Using nonlinear dimensionality-reduction-based surrogates did not reduce surrogate error for predicting nodal coordinates. A new metric, the manifold distance ratio (MDR), was introduced to measure the nonlinearity of the data manifolds. When applied to the stress and coordinate data, the stress space was found to be more nonlinear than the coordinate space for this application. The upfront training cost of the nonlinear dimensionality-reduction-based surrogates was larger than that of their linear counterparts but small enough to remain feasible. After training, all the dual-RBF surrogates were capable of making real-time predictions. This same process was repeated for a separate application involving the nodal displacements of mode shapes obtained from a FEA modal analysis. The modal assurance criterion (MAC) calculation was used to compare the predicted mode shapes, as well as their corresponding true mode shapes obtained from FEA, to a set of reference modes. The research showed that two nonlinear techniques, namely LLE and KPCA, resulted in lower surrogate error in the more complex design spaces. Using a RBF kernel, KPCA achieved the largest average reduction in error of 13.57%. The results also showed that surrogate error was greatly affected by mode shape reversal. Four different approaches of identifying reversed mode shapes were explored, all of which resulted in varying amounts of surrogate error. Together, the methods explored in this research were shown to decrease surrogate error when performing DSE of a turbomachine compressor blade. As surrogate accuracy increases, so does the ability to correctly make engineering decisions and judgements throughout the design process. Ultimately, this will help engineers design better turbomachines.