http://www.ideals.illinois.edu:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. http://hdl.handle.net/2142/14180 Method of Seismic Reliability Evaluation for Moment Resisting Steel Frames Eliopoulos, D.F. Wen, Y.K. The objective of this study is development of a method for evaluation of performance of moment resisting steel frames under seismic loads. The emphasis is on modeling and quantification of the large uncertainties associated with the excitation, details in design according to current code specifications (UBC) , and the nonlinear inelastic response behavior of the structure. A site-specific seismic hazard.analysis is carried out to identify and quantify the uncertainties associated with· the source, the path and the site condition. Future earthquakes are treated as either characteristic (major event along a well-identified major fault segment) on non-characteristic (local events). Ground motions are modeled as nonstationary random processes with time varying amplitude and frequency content, whose parameters depend on the source, path and site conditions. A strong column - weak beam model is developed for the structural frame and with which response can be obtained with good accuracy and computational efficiency. The response statistics are obtained by method of random vibration based on an equivalent linearization solution procedure and a smooth differential equation model for the hysteretic restoring force. The accuracy of this method is verified by comparison with simulations. A fast integration technique is then used to evaluate the probability of limit state (interstory drift limit being exceeded) considering the uncertainties in the excitation parameters. The robustness of the proposed method is demonstrated in the numerical examples throughout this study. The method can be used in assessing the risk implied in current earthquake resistant design, and in developing reliability-based code procedures. Hysteresis earthquake motions Code and standard http://hdl.handle.net/2142/14179 Approximate Techniques of J Estimation Applicable to Part-Through Surface Cracks Kirk, M.T. Dodds, Jr., R.H. This investigation concerns the accuracy with which three different estimation schemes predict the variation of applied I with applied strain for semi-elliptical surface cracks. The three estimation schemes considered were a weight function technique proposed by Bhandari, a modification of the EPRI estimation scheme proposed by Ainsworth, and Turner's Engineering- I design curve. Each of these techniques is simple enough to employ in design, the most arduous calculation required being that needed to determine the linear elastic stress intensity factor. Accuracy of the estimation schemes was assessed by comparing I predictions to finite element results for three small semi-elliptical surface cracks in a moderately hardening steel loaded in either pure tension or pure bending. The results obtained indicate that, for applied strains up to three times the yield strain, both the weight function and the modified EPRI schemes under estimate applied I by between 23 % and 83 % depending on the applied strain level. Conversely, Turner's Engineering-I design curve provides accurate or conservative (i.e. over) estimates of applied J in both tension and bending provided total crack size is less than 3% of the total cross sectional area and maximum crack depth is less than 25% of the plate thickness. Application to larger and deeper cracks loaded in tension is not recommended as the design curve does not conservatively account for net section yielding in these situations. The design curve can still be applied in bending to cracks of size up to 7% of the total cross sectional area. However, the degree of conservatism inherent in this application may be considered excessive in certain situations. Fracture mechanics finite elements Surface cracks http://hdl.handle.net/2142/14178 An Experimental Setup to Investigate Dynamic Torsional-Translational Response of Reinforced Concrete Keiser, R.L. An experimental test setup is described which permits investigation of the torsional- translational response of reinforced concrete structures to earthquake effects. The main feature of the setup is the uncoupling of material interaction while retaining the effects of dynamic interaction. A two degree-of-freedom system was developed with its movement constrained to rotation about two orthogonal axes. The inertial forces developed during earthquake simulation are resisted by two flexural elements, each resisting motion about one axis. This report describes the specimen material properties, fabrication, erection hardware and instrumentation. Features of the earthquake simulator control and data acquisition system are presented. Reinforced concrete Earthquake engineering earthquake motions http://hdl.handle.net/2142/14177 The Effect of Weld Metal Strength Mismatch on the Deformation and Fracture Behavior of Steel Butt Weldments Kirk, M.T. Dodds, Jr., R.H. Considerable Naval and industrial experience dating from the explosion bulge studies of Pellini and Hartbower in the early 1950s has indicated the engineering utility of using weld metal having strength greater than the plates being joined (overmatching). This practice shields the weld region, which typically has lower toughness than the plate and is often the site of defects, from the high strains that develop during an overload. This practical advantage, coupled with the ease of achieving overmatch in lower strength steel alloys (80 ksi yield strength or less) has led to codification of overmatching as a requirement in most structural design codes and fabrication specifications. However, overmatching has certain economic and technical disadvantages which undermatched (weld metal strength less than plate strength) systems might alleviate. Examples of undermatch benefits discussed in the literature include reduction of the preheat needed to avoid hydrogen cracking and increase of weld metal deposition rate relative to overmatched practice. Such changes could reduce the need to hold electrodes at an elevated temperature prior to use, extend the welder's duty cycle, reduce the lack of fusion / lack of penetration defect rate, reduce restraint stresses, and increase weld metal toughness. This information suggests that overmatched welds, while quite effective for low strength steel construction, may not be as advantageous when fabricating structures from higher strength grades. However, undermatched welds cannot be immediately adopted for use due to the much greater strains that would have to be borne by the weld metal. Undermatched welds will require greater toughness to provide the same safety margin against fracture as overmatched construction. To quantify the toughness / matching combinations which provide acceptable service performance, information regarding how over and under matching influences the stresses and strains in a weld joint is needed. Additionally, procedures for quantifying the fracture toughness of candidate weld metals and their heat affected zones will be required. In support of the further development of such information and procedures, this report reviews investigations concerning the deformation and fracture characteristics of Simple mechanical test specimens containing butt welds, focusing on how the relative strength of the weld deposit and the plate influences these characteristics. Weldments Fracture mechanics http://hdl.handle.net/2142/14176 A Large Strain Plasticity Model for Implicit Finite Element Analyses Dodds, Jr., R.H. Healy, B.E. The theoretical basis and numerical implementation of a plasticity model suitable for finite strains and rotations are described. The constitutive equations governing J2 flow theory are formulated using strainsstresses and their rates defined on the unrotated frame of reference. Unhke models based on the classical Jaumann (or corotational) stress rate, the present model predicts physically acceptable responses for homogeneous deformations of exceedingly large magnitude. The associated numerical algorithms accommodate the large strain increments that arise in finite-element formulations employing an implicit solution of the global equilibrium equations. The resulting computational framework divorces the finite rotation effects on strain-stress rates from integration of the rates to update the material response over a load (time) step. Consequently, all of the numerical refinements developed previously for small-strain plasticity (radial return with subincrementation, plane stress modifications, kinematic hardening, consistent tangent operators) are utilized without modification. Details of the numerical algorithms are provided including the necessary transformation matrices and additional techniques required for finite deformations in plane stress. Several numerical examples are presented to illustrate the realistic responses predicted by the model and the robustness of the numerical procedures. Finite element analysis Plasticity http://hdl.handle.net/2142/14175 Parameter Estimation in Complex Linear Structures Hjelmstad, K.D. Wood, S.L. Clark, S.J. In this work we describe an approach to parameter estimation of complex linear structures which we call the mutual residual energy approach. Our main goal has been to develop a unified approach to the discrete inverse problems describing static equilibrium and free, undamped vibration, with a particular view toward evolving methods which are amenable to large-scale computation. The mutual residual energy method is based on the assumption that the topology and geometry of the structure are known, and that the system matrices can be linearly parameterized in terms of kernel matrices which have a solid physical basis and are easy to assemble. Measured motions of the structure are used (in conjunction with measured loads for the static case) to make estimates of the constitutive parameters. The method is based on a particular statement of the principle of virtual work and yields equations for estimating stiffness and mass parameters of linear structures. If the response of the structure is measured completely, the estimation equations are linear and generally overdetermined. A condensation procedure is presented to deal with the case of incompletely measured systems.The quantity and quality of response measurements required, the consequences of noisy data, and the choice of load form are among the issues important to the success of our parameter estimation scheme. Extensive numerical simulations have been carried out to assess the performance of the algorithms developed. Numerical analysis Paramenter estimation http://hdl.handle.net/2142/14174 Cooperative Calibration and Analysis of Cement Clinker Phases, Report 2 Struble, L.J. A cooperative calibration was carried out by ASTM Task Group C01.23.01 as part of an effort to assess the use of X-ray diffraction analysis for determining the proportion of tricalcium aluminate (cubic and orthorhombic), tetracalcium aluminoferrite, and magnesium oxide in portland cement and clinker. That calibration, including statistical analysis to determine precision and bias, was described in an earlier report. Since that previous rePOI4 some additional data have been submitted and the statistical analysis repeated. The subsequent analysis showed that the calibration precision were improved, though only slightly. With these additional data. Based on this statistical analysis, repeatability and reproducibility levels may be specified for analysis of these 4 phases in unknown mixtures prepared from the same materials. Replicate analyses in the same laboratory should differ by no more than 1.1 % (relative to the total clinker) [the previous level was also 1.1 %]. Replicate analyses in different laboratories should differ by no more than 1.7% (relative to the total clinker) [the previous level was 1.8%]. Overall, analyses should differ from the known value by no more than 1.7% (relative to the total clinker). The measured values differ from the known values by less than the reproducibility standard deviation, so there appears to be no bias in these results. Cement Clinker Phases http://hdl.handle.net/2142/14173 Chapter 5: Cold Comfort (The Cusp of Dreams) Sheets, Diana E. This novel is a dark saga of modern business and the lives of people who struggle in its pursuit. It is the story of the men and women in the trenches who do what they can to close thousand-dollar contracts and who wonder how they are going to pay next-month's rent. They lie, cheat, steal, and, when necessary, attack their co-workers at Amtech. However, their schemes don't work, and their jobs and personal relationships disintegrate. For the men and women living on the cusp, the outcomes are bad or, at best, ambiguous. Perhaps nobody cares, but we should because as the road-warriors' lives collapse our whole society crumbles. Fiction Capitalism Business American Society http://hdl.handle.net/2142/14172 Chapter 4: Fleur-de-Lis (The Cusp of Dreams) Sheets, Diana E. This novel is a dark saga of modern business and the lives of people who struggle in its pursuit. It is the story of the men and women in the trenches who do what they can to close thousand-dollar contracts and who wonder how they are going to pay next-month's rent. They lie, cheat, steal, and, when necessary, attack their co-workers at Amtech. However, their schemes don't work, and their jobs and personal relationships disintegrate. For the men and women living on the cusp, the outcomes are bad or, at best, ambiguous. Perhaps nobody cares, but we should because as the road-warriors' lives collapse our whole society crumbles. Fiction Capitalism Business American society http://hdl.handle.net/2142/14171 Chapter 3: Embers (The Cusp of Dreams) Sheets, Diana E. This novel is a dark saga of modern business and the lives of people who struggle in its pursuit. It is the story of the men and women in the trenches who do what they can to close thousand-dollar contracts and who wonder how they are going to pay next-month's rent. They lie, cheat, steal, and, when necessary, attack their co-workers at Amtech. However, their schemes don't work, and their jobs and personal relationships disintegrate. For the men and women living on the cusp, the outcomes are bad or, at best, ambiguous. Perhaps nobody cares, but we should because as the road-warriors' lives collapse our whole society crumbles. Capitalism Fiction Business American society