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Xue L.,MMI Engineering Inc. | Widera G.E.O.,Marquette University | Sang Z.,Nanjing University of Technology
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2010

In an earlier paper (2009, "Burst Pressure of Pressurized Cylinders With the Hillside Nozzle," ASME J. Pressure Vessel Technol., 131(4), p. 041204), an elastic-plastic large deflection analysis method was used to determine the burst pressure and fracture location of hillside cylindrical shell intersections by use of nonlinear finite element analysis. To verify the accuracy of the finite element results, experimental burst tests were carried out by pressurizing test vessels with nozzles to burst. Based on the agreement between the numerical simulations and experimental results of Wang et al. (2009, "Burst Pressure of Pressurized Cylinders With the Hillside Nozzle," ASME J. Pressure Vessel Technol., 131(4), p. 041204), a parametric study is now carried out. Its purpose is to develop a correlation equation by investigating the relationship between various geometric parameters (d/D, D/ T, and t/ T) and the burst pressure. Forty-seven configurations, which are deemed to cover most of the practical cases, are chosen to perform this study. In addition, four different materials are employed to verify that the proposed equation can be employed for different materials. The results show that the proposed equation resulting from the parametric analysis can be employed to predict the static burst pressure of cylindrical shell intersections for a wide range of geometric ratios. Copyright © 2010 by ASME.

El-Tawil S.,University of Michigan | Ekiz E.,MMI Engineering Inc. | Goel S.,University of Michigan | Chao S.-H.,University of Texas at Arlington
Journal of Constructional Steel Research | Year: 2011

Carbon fiber-reinforced polymer (CFRP) composites have been shown to be particularly well suited for external strengthening of reinforced concrete members. However, there is limited information about how they can be used to strengthen steel structures that are susceptible to local and global instabilities. This paper discusses test results of full-scale steel flexural specimens subjected to reversed cyclic loading, some of which are wrapped with CFRP in the plastic hinge region. The main variables investigated are lateral bracing, to study the effect of CFRP wrapping on local buckling and lateral torsional buckling, wrapping scheme, and number of layers of fibers. The test results show that application of CFRP in the plastic hinge region of flexural members has substantial benefits. In particular, the CFRP wraps can increase the size of the yielded plastic hinge region, slow down the occurrence of local buckling, and delay lateral torsional buckling. These benefits reduce strain demands in the critical plastic hinge region and substantially improve energy dissipation capacity within the plastic hinge region. © 2010 Elsevier B.V. All rights reserved.

Graf W.P.,ImageCat Inc. | Seligson H.A.,MMI Engineering Inc.
Earthquake Spectra | Year: 2011

The M7.8 San Andreas earthquake scenario for the ShakeOut exercise subjects more than a million wood-framed buildings to loads beyond their elastic capacity. Residential construction from the boom from the 1960's to 1980's relied heavily upon drywall sheathing and stucco for shear walls - more vulnerable than plywood or the gypsum lath and plaster of older buildings. During this same construction boom, many apartment buildings were built with tuck-under parking, and heavy masonry chimneys were prevalent. Based on HAZUS®MH modeling we describe, more than 30,000 (mostly older) wood buildings could be red-tagged or yellow-tagged in the scenario event. More recent wood-frames, engineered using plywood shear walls, should perform well, evenunder the conditions produced by the San Andreas event considered. Cost-effective retrofit measures exist for some of the weaknesses found in older wood construction, but seismic upgrade of wood-framed buildings with structural wood panels remains expensive and intrusive. © 2011, Earthquake Engineering Research Institute.

Alpdogan C.,MMI Engineering Inc. | Dong S.B.,University of California at Los Angeles | Taciroglu E.,University of California at Los Angeles
International Journal of Solids and Structures | Year: 2010

We present a rigorous verification study and an extension to an existing semi-analytical finite element formulation for analysis of end and transition effects in prismatic cylinders. End and transition effects in stressed cylinders are phenomena associated with the difference between results that are predicted by the Saint-Venant solutions and the actual point-wise conditions. These differences manifest themselves as self-equilibrated stress states. Notwithstanding certain well-known exceptions (e.g., restrained torsion of open thin-walled sections), such effects in isotropic cylinders are usually confined to a very small neighborhood of a terminal boundary or transition zone, and are typically neglected. For anisotropy, as in the case of most smart/active and composite material systems, they can persist much further into the interior of the structure, and need to be quantified to design geometry transition zones and to fully understand the delamination effects. In the semi-analytical approach, we first discretize the governing equations within the cross-sectional plane of the cylinder. The end-solution fields satisfy the homogeneous form of the resulting semi-analytical system of ordinary differential equations. This leads to an algebraic eigenvalue problem, and an eigenfunction expansion of the stress and displacement fields due to end effects. Unique to the present study, we formulate a procedure to quantify the transitional effects for end-to-end connected cylinders for which the displacement and stress continuity along the transition interface need to be enforced. The semi-analytical approach has several distinct advantages: (i) It is computationally efficient, as only the cross-sectional geometry is discretized; (ii) it can be applied to arbitrary cross-sectional geometries and the most general form of anisotropy; and (iii) it yields direct measures for the decay lengths (or decay rates) of any end-or transition-solution field. Analytical solutions to end-effect problems are scarce. Those that exist are for simple geometry and material constitution. We use these analytical solutions, as well as solutions obtained using three-dimensional finite element models, to verify our approach and to assess its efficiency. © 2009 Elsevier Ltd. All rights reserved.

Jones T.,MMI Engineering Inc.
Institution of Chemical Engineers Symposium Series | Year: 2015

The understanding of the explosion hazards on fixed and floating offshore facilities is required to be able to demonstrate that risks are ALARP (As Low As Reasonably Practicable). It is becoming increasingly common to adopt a risk based approach whereby overpressures are calculated across a range of frequencies. Such an approach is typically referred to as an Explosion Risk Analysis (ERA). In order to understand the explosion hazards, one of the key aspects is to calculate the range of potential gas cloud sizes that can arise from an accidental release from the different inventories present. This is achieved by conducting dispersion analysis using either empirical or CFD (Computational Fluid Dynamics) methods which are not well validated. The scope of this paper is as follows; • Validate the use of CFD for calculating cloud sizes by comparing the results with experimental data. • Validate the Frozen Cloud concept. © 2015 Amec Foster Wheeler.

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