Seismic design criteria have been heavily improved by the Federal Emergency Management Agency (FEMA) after the Northridge CA earthquake in 1994. Most of the damage observed was caused by brittle failure of moment frame connections. This failure was induced by the formation of the plastic hinge at undesirable locations in the beam and the column near the connection. Using welded flange plate (WFP) connections will force the formation of the plastic hinge away from the face of the column while preventing the brittle failure of the moment connection. FEMA-350 design criteria recommendations for WFP connections suggest that the plastic hinge will form away from the face of the column directly under the cover plate. The purpose of this research is to prove that the plastic hinge will form away from the face of the column, at a distance of approximately half the depth of the beam away from the cover plate. The further away the plastic hinge is from the face of the column the higher the connection demands. Therefore, underestimating the location of the plastic hinge could lead to under designed connections. The modeling and analysis of WFP connections was performed using finite element analysis software. A total of eight models with half beam half column configuration were considered in this study. Each selected section of beam and column was first designed, modeled and analyzed using WFP connections design recommendations from FEMA-350, with calculations modifications to account for the proposed plastic hinge location. Results were computed and comparisons were made in terms of plastic hinge location from the cover plates. Strength obtained for each model using finite element analysis software was also compared with hand calculations. This research also proves that increasing the thickness of the cover plates will generate an increase in the connection capacity and strength.

The design and maintenance of Marine Oil and LNG Terminals is governed by the Marine Oil Terminal Engineering and Maintenance Standards (MOTEMS) which is part of the 2010 Title 24 California Code of Regulations, Part 2, California Building Code, Chapter 31F: Marine Oil Terminals. The purpose of this thesis is to evaluate the current recommendations for the in-ground plastic hinge length and depth for piles in section 7 of MOTEMS for all typical soil properties and pile dimensions found in Marine Oil and LNG Terminals. The pile types considered in this analysis are 24-inch octagonal prestressed concrete piles and 24-, 36-, and 48-inch steel pipe piles in varying soil conditions. Existing recommendations for plastic hinges are incomplete and inadequate. MOTEMS does not have any recommendations for plastic hinge depth, only length, nor does it have any recommendations for in-ground plastic hinge for steel piles. Recommendations for steel piles are however found in the Port of Long Beach Wharf Design Criteria (POLB), but the recommendations in both MOTEMS and POLB have shown to be inadequate for both steel and prestressed concrete piles. MOTEMS also proves to be adequate for Level 2 earthquakes but not for Level 1. The plastic hinge length for Level 1 is much longer than that for Level 2. So the MOTEMS recommendations for Level 1 lead to conservatively small displacement capacity. POLB recommendations are also adequate for Level 2 but not Level 1 for concrete and are overly conservative for steal and therefore, not adequate for either level except in dense and medium sands during a Level 1earthquake. POLB does not take into account different soil characteristics and has one value for all soils, which is inadequate for most cases.

Because of their high strength to weight ratio, stiffened steel plates are often used in light structures where plates are placed into compression. The stability of steel plates stiffened with longitudinal tee-shaped stiffeners and subjected to uniaxial compression or combined axial compression and out-of-plane bending formed the basis for this research project. The research was conducted to develop a simple approach to assess the post-buckling behaviour of stiffened steel plates and provide a limit states design procedure that accounts for the post-buckling stability in the assessment of the resistance factor. The behaviour of stiffened plates was investigated using a finite element model that had been validated through comparison with test results. An exhaustive parametric study, including 1440 finite element analyses, was conducted to investigate the strength and behaviour of stiffened steel plates. A virtual work model was developed to explain the effect of the formation of a plastic hinge mechanism on the post-buckling strength and behaviour. Combined with the numerical results, the theoretical model confirms that the plastic hinge mechanism can cause a sudden loss of capacity. The required lateral deflection for a plastic hinge development can be calculated using the virtual work model for prediction of the unstable behaviour. Based on a better understanding of the behaviour of stiffened steel plates, a set of design equations were developed to calculate the strength of stiffened steel plate subjected to compression in the direction of the stiffener and out-of-plane bending. The proposed design equations were compared with current design guidelines through a comparison of the design approaches with the finite element analysis results. The proposed method showed much better accuracy than the current design approaches. A reliability analysis was conducted to provide appropriate resistance factors for limit states design. Due to the complexity of the design formulas, the Monte Carlo simulation technique was used to generate the statistical distributions of the predicted strength. The second-moment method was used to calculate the resistance factors for different values of safety index. The resistance factor varied from 0.90 to 0.65 for values of safety index from 2.5 to 4.5, respectively. / Structural Engineering

No description available.

Doctor of Philosophy / Civil Engineering / Asadollah Esmaeily / Accurate and realistic assessment of the performance of columns in general, and those in critical locations that may cause progressive failure of the entire structure, in particular, is significantly important. This performance is affected by the load history, pattern, and intensity. Current design code does not consider the effect of load pattern on the load and displacement capacity of columns. A primary research sponsored by Kansas Department of Transportation (KDOT) was conducted as the initial step of the present study (No. K-TRAN: KSU-11-5). The main goals of the KDOT project were: (1) investigation of new KDOT requirements in terms of the column design procedure and detailing and their consistency with AASHTO provisions; (2) verification of the KDOT assumptions for the plastic hinge regions for columns and bridge piers, (3) provide assessment of the load capacity of the existing columns and bridge piers in the light of the new specifications and using the new load demand as in the new provisions; and finally recommendations for columns and bridge piers that do not meet the new requirements. A conclusion was drawn that there is a need for conducting more studies on the realistic performance of Reinforced Concrete (RC) sections and columns. The studies should have included performance of RC members under various loading scenarios, assessment of columns capacity considering confinement effect provided by lateral reinforcement, and investigation on performance of various monotonic and cyclic material models applied to simulate the realistic performance. In the study reported here, monotonic material models, cyclic rules, and plastic hinge models have been utilized in a fiber-based analytical procedure, and validated against experimental data to simulate behavior of RC section under various loading scenarios. Comparison of the analytical predictions and experimental data, through moment–curvature and force–deflection analyses, confirmed the accuracy and validity of the analytical algorithm and models. The performance of RC columns under various axial and lateral loading patterns was assessed in terms of flexural strength and energy dissipation. FRP application to enhance ductility, flexural strength, and shear capacity of existing deficient concrete structures has increased during the last two decades. Therefore, various aspects of FRP-confined concrete members, specifically monotonic and cyclic behavior of concrete members confined and reinforced by FRP, have been studied in many research programs, suggesting various monotonic models for concrete confined by only FRP. Exploration of existing model performances for predicting the behavior of several tested specimens shows a need for improvement of existing algorithms. The model proposed in the current study is a step in this direction. FRP wrapping is typically used to confine existing concrete members containing conventional lateral steel reinforcement (tie/spiral). The confining effect of lateral steel reinforcement in analytical studies has been uniquely considered in various models. Most models consider confinement due to FRP and ignore the effect of conventional lateral steel reinforcement. Exploration of existing model performances for predicting the behavior of several tested specimens confined by both FRP and lateral steel shows a need for improvement of existing algorithms. A model was proposed in this study which is a step in this direction. Performance of the proposed model and four other representative models from literature was compared to experimental data from four independent databases. In order to fulfill the need for a simple, yet accurate analytical tool for performance assessment of RC columns, a computer program was developed that uses relatively simple analytical methods and material models to accurately predict the performance of RC structures under various loading conditions, including cyclic lateral displacement under a non-proportionally variable axial load (Esmaeily and Xiao 2005, Esmaeily and Peterman 2007). However, it was limited to circular, rectangular, and hollow circular/rectangular sections and uniaxial lateral curvature or displacement. In this regards, a computer program was developed which is the next generation of the aforesaid program with additional functionality and options. Triangulation of the section allows opportunity for cross-sectional geometry. Biaxial lateral curvature/displacement/force combined with any sequence of axial load provides opportunity to analyze the performance of a reinforced concrete column under any load and displacement path. Use of unconventional reinforcement, such as FRP, in lateral as well as longitudinal direction is another feature of this application.

Pages vi, 34, 68, 158, 208 and 226 are blank and therefore omitted. / <p> To assess the ductility of shear walls under earthquake loading, more experimental evidence is strongly needed. Ductile response can be achieved through the development of a flexural plastic hinge at the base characterized by yielding of the vertical reinforcement. The length of the plastic hinge and the ultimate curvatures within this region are the essential parameters affecting the ductility and ultimate displacements of reinforced masonry shear walls. The discrepancies in existing information regarding the length of plastic hinges and ultimate curvature may be attributed to the effects of many shear wall parameters such as distribution and amount of vertical and horizontal steel, level of axial load, and wall aspect ratio. </p> <p> The focus of this study was to evaluate the effect of different parameters on plastic hinge length, energy dissipation, and on general ductility of masonry shear walls. To address the aforementioned goal, six fully grouted reinforced masonry walls were tested under fully reversed cyclic lateral loading. All walls were designed to experience ductile flexural failure. The test matrix was chosen to investigate the effects of the amount and distribution of vertical reinforcement and the level of applied axial load on the lateral loading response and ductility of reinforced masonry shear walls. To examine the effects of these parameters, measurements of the applied loads, vertical and horizontal displacements as well as strains in the reinforcing bars were used to analyze the behaviour of the walls. Also, from these measurements, other quantities used in analysis were determined, including displacement ductilities, curvature profiles, energy dissipation and equivalent plastic hinge length. </p> <p> The results show high ductile capability in the plastic hinge region and very little degradation of strength for cyclic loading. High levels of energy dissipation in the reinforced concrete masonry shear walls were achieved by flexural yielding of the vertical reinforcement. All walls showed increasing hysteretic damping ratios with increase in displacement. Results showed that displacement ductility and energy dissipation were highly sensitive to increases in amount of vertical reinforcement but were less dependent on the level of applied axial stress. The results of this study also showed that the measured plastic zone length decreases with increase of the amount of reinforcement while it is almost the same for the different levels of axial stress. Based on the test results, it was shown that reinforced concrete masonry shear walls may be utilized in high intensity seismic areas with performance meeting or exceeding current expectations. </p> / Thesis / Master of Applied Science (MASc)

No description available.

Considering the deficiencies frequently observed in the existing reinforced concrete buildings, detailed assessment and rehabilitation must be conducted to avoid significant life and value loss in seismic zones. In this sense, performance based evaluation methods suggested in the regulations and codes must be examined and revised through experimental and analytical research to provide safe and economical rehabilitation solutions. In this study, seismic behavior of three reinforced concrete frames built and tested in Middle East Technical University Structural Mechanics Laboratory is examined. The specimens are extracted from a typical interior frame of 3-story 3-bay reinforced concrete structure. One of the specimens has compliant design according to Turkish Earthquake Code (2007) and each of the other two specimens represents different types of deficiencies in terms of material strength and detailing. The test specimens were modeled using different modeling approaches and nonlinear dynamic analyses were conducted on the numerical models. Results of continuous pseudo-dynamic testing of three ground motions are presented and compared with the numerical simulations on models. Calibrated finite element models were used for evaluation of performance assessment procedure of Turkish Earthquake Code (2007) and further investigation on local deformation components in light of experimental findings and observations. Deformation sources of columns and joints were studied in terms of their interaction and contributions to the total drift. Estimated plastic hinge lengths of columns were compared with the experimental observations and the proposed expressions in the literature.

Made available in DSpace on 2015-03-26T13:28:05Z (GMT). No. of bitstreams: 1 texto completo.pdf: 3306173 bytes, checksum: 78f6502185ffad0df1f3c37bb1c66aad (MD5) Previous issue date: 2011-07-15 / Alveolar beams are usually made from rolled shapes cut in half in a zigzag way, displaced and welded again to obtain profiles with greater height and same weight. This work presents the results of a non-linear numerical analysis performed with alveolar steel beams using the software ABAQUS. The main focus of this work was to study the formation of plastic hinges. The experimental test results obtained by Toprac e Cooke (1959) were used to validate the numerical models. The results of numerical analysis were also used in the validation of analytical models presented in this work. In design of alveolar steel beams few studies in literature presented consistent analytical models as Delesques (1968.1969) and Cimadevila (2000). But these works were proposed for a single castellation standard. In this work analytical models have been adapted for various types of holes. Considerations were also made as to the total yielding of the cross section of the webpost, which allowed a closer approximation to the results of numerical models. The study represents a contribution to the establishment of criteria for design of alveolar steel beams according to the standards of design and calculation of structures. / Vigas alveolares são normalmente obtidas a partir de perfis laminados cortados ao meio em zigue-zague, deslocadas e soldadas novamente de forma a obter perfis com maior altura e mesmo peso. Neste trabalho são apresentados os resultados de uma análise numérica não-linear realizada com vigas alveolares de aço utilizando o programa ABAQUS. O enfoque principal do trabalho foi o estudo da formação de rótulas plásticas. A validação dos modelos numéricos foi realizada com resultados experimentais obtidos por Toprac e Cooke (1959). Os resultados da análise numérica também foram utilizados na validação de modelos analíticos apresentados nesse trabalho. Poucos trabalhos na literatura apresentaram modelos analíticos tão consistentes como os de Delesques (1968, 1969) e Cimadevila (2000) para o dimensionamento de vigas alveolares. Porém esses trabalhos foram propostos para apenas um único padrão de castelação. Neste trabalho os modelos analíticos foram adaptados para diversos tipos de aberturas. Também foram feitas considerações quanto à plastificação total da seção transversal do montante de alma, o que permitiu uma aproximação maior com os resultados dos modelos numéricos. O estudo representa uma contribuição para o estabelecimento de critérios de dimensionamento de vigas alveolares de acordo com as normas vigentes de projeto e cálculo de estruturas metálicas.

Thanks to the advancement of additive manufacturing, periodic metallic lattice structures are gaining more and more attention. A major attraction of them is that their design can be tailored to specific applications by changing the basic repetitive pattern of the lattice, called the unit cell. This may involve the selection of optimal strut diameters and orientations, as well as the connectivity and strut lengths. Numerical simulation plays a vital role in understanding the mechanical behavior of metallic lattices and it enables the optimization of design parameters. However, conventional numerical modeling strategies in which each strut is represented by one or more beam finite elements yield prohibitively time­ consuming simulations for metallic lattices in engineering­ scale applications. The reasons are that millions of struts are involved, as well as that geometrical and material nonlinearities at the strut level need to be incorporated. The aim of this thesis is the development of multi­scale quasicontinuum (QC) frameworks to substantially reduce the simulation time of nonlinear mechanical models of metallic lattices. For this purpose, this thesis generalizes the QC method by a multi­-field interpolation enabling amongst others the representation of varying diameters in the struts’ axial directions (as a consequence of the manufacturing process). The efficiency is further increased by a new adaptive scheme that automatically adjusts the model reduction whilst controlling the (elastic or elastoplastic) model’s accuracy. The capabilities of the proposed methodology are demonstrated using numerical examples, such as indentation tests and scratch tests, in which the lattice is modeled using geometrically nonlinear elastic and elastoplastic beam finite elements. They show that the multi­scale framework combines a high accuracy with substantial model reduction that are out of reach of direct numerical simulations. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished