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Zou X.-K.,Arup | Wang Q.,Kal Krishnan Consulting Services Inc. | Li G.,Dalian University of Technology | Chan C.-M.,Hong Kong University of Science and Technology
Journal of Structural Engineering | Year: 2010

This paper presents an effective numerical reliability-based optimization technique for the design of base-isolated concrete building structures under spectrum loading. Attempts have been made to automate the integrated spectrum analysis, reliability analysis, and design optimization procedure and to minimize the total cost of the base-isolated building subjected to multiple design performance criteria in terms of the story drift of the superstructure and lateral displacement of the isolation system or corresponding reliability constraints. In the optimal design formulation, the cost of the superstructure can be expressed in terms of concrete member sizes while assuming all these members to be linear elastic under a specified design earthquake. However, the base isolation is assumed to behave nonlinearly and its cost can be related to the effective horizontal stiffness of each isolator. Based on the principle of virtual work, the drift responses and corresponding reliability indexes can be explicitly formulated and the integrated optimization problem can be solved by an optimality criteria method. The technique is capable of achieving the optimal balance between the costs of the superstructure and isolation systems while the seismic drift performance or corresponding reliability of a building can be simultaneously considered. An illustrative example shows that conventional deterministic design optimization cannot ensure designs with satisfactory reliability levels, whereas the reliability-based design optimization can achieve the objective when uncertainties are considered. It is believed that such an optimization technique provides an effective tool for seismic design of building structures. © 2010 ASCE.

Shi H.,Kal Krishnan Consulting Services Inc. | Salim H.,University of Missouri | Shi Y.,A. Morton Thomas and Associates Inc. | Wei F.,Hohai University
Mechanics Based Design of Structures and Machines | Year: 2015

A formulation of the nonlinear FEM truss element that takes into account both the geometric nonlinearity and material nonlinearity of the structure is derived. The associated iterative algorithm for the application is described. Based on two inelastic material models (isotropic hardening and dynamic hardening), three space truss structures are subjected to static and to dynamic loads in order to illustrate the application of nonlinear FEM. The nonlinear FEM described can accurately trace the complex structural behavior of space truss structures, including snap-through, and buckling. The FEM results match well with the theoretical results. © 2015 Taylor & Francis Group, LLC.

Shi H.,Kal Krishnan Consulting Services Inc. | Wang Q.,Manhattan College | Wei F.,Hohai University | Shen L.,University of Hawaii at Manoa
Structural Engineer | Year: 2013

The combination of FEM and LPA provides a powerful and accurate tool for analysing the load fl ow inside the complex fl oating concrete structure, i.e., the concrete gate. Both the reaction forces at the supports and the internal forces inside the shear walls and decks are fi rst obtained using the FEM software SAP2000. Through the static load equilibrium, the attributed external loads on the front side of the gate can be derived. The loads are then dissipated through the combined interaction of the internal structural members in the form of direct shear forces or bending moments. All the loads eventually go into the support in the rear side of the gate structure, i.e. The abutment wall and the base sill. Interesting observations can also be made in regard to the load transfer pattern inside the fl oating concrete gate structure: • Less than 7% of the unbalanced external load is transferred by the top deck, whereas 38% is transferred through the middle deck and 31% through keel slab • Approx 9% of the total external load is transferred through the two internal walls at the abutment wall locations (at gridlines 2 and 12), and 14% through the two internal walls at gridlines 5 and 9 in the middle of the gate • A total of 34% of the reaction force is along the abutment wall, and the remaining 66% transfers from the base sill to the foundation Through the application of LPA in the concrete gate, the complex load fl ow inside the structure is identifi ed. The methodology introduced in this paper is universal as long as FEM can be conducted for the target structures.

Wang Q.,Kal Krishnan Consulting Services Inc. | Fang H.,University of North Carolina at Charlotte | Zou X.-K.,Arup
Structural and Multidisciplinary Optimization | Year: 2010

Seismic isolation and energy dissipation systems are innovative strategies for seismic design and upgrade or retrofit of bridges. In a retrofit design, base isolation devices can be easily incorporated into existing bridges to replace conventional bearings and to improve the overall structural performance. In this paper, an optimal cost base isolation design or retrofit design method for bridges subject to transient earthquake loads is studied. The goal of this study is to push forward the concept of retrofit design optimization of structures using this isolation design as an example. This is achieved by combining nonlinear time history analyses with an optimization procedure to select base isolators that minimize the cost of the isolation system while satisfying certain design requirements. An improved genetic algorithm (GA), Micro-GA, is employed to search for the optimal solutions for such discrete optimization problems. An example of the optimal design of a highway bridge is presented and the minimum cost expense of the isolation system is achieved with improved structural response under multiple transient earthquake loads. © 2009 Springer-Verlag.

Shi H.,Kal Krishnan Consulting Services Inc. | Salim H.,University of Missouri | Ma G.,University of Western Australia
International Journal of Protective Structures | Year: 2012

This paper puts forward a simplified method for assessing the failure modes of rigid-plastic beams by solving the governing partial differential equation with defined initial conditions based on five previously developed transverse velocity profiles. It is found that there are twelve different response patterns possible for a rigid-plastic beam subjected to a triangular pulse shape impulsive load. As developed in this paper, the PI diagram is based on the derived deformation pattern such that selected failure criteria can be used to identify and differentiate various failure patterns. The shear-to-bending ratio, the boundary conditions, and the load pulse shape, all influence the response of the rigid-plastic beams, and are discussed in detail. Although the peak pressure and the shear-to-bending ratio together determine the response pattern, it is also found that the combination of peak pressure, impulse, and shear-tobending ratio define the failure type and sequence. Fully clamped beams are relatively resistant to bending failure; however, they are more vulnerable to shear failure at the supports than simply supported beams. Compared with the triangular-shape impulsive load, the rectangularshape impulsive load is more vulnerable in the pressure and impulse combination-controlled zone. The explicit solutions are compared with results obtained by using the Single-Degree-of- Freedom (SDOF) approach and are found to be exactly the same whether the beams have a small shear-to-bending ratio ( > 1) or a large such ratio (? > 1.5). But for beams with medium shear-to-bending ratio (1 >> 1.5), only the presented approach derived solutions.

Gordon G.A.,Kal Krishnan Consulting Services Inc. | Young R.R.,Capital College
2015 Joint Rail Conference, JRC 2015 | Year: 2015

The railroad industry is being challenged by recent state regulations requiring the disclosure of routing information of trains carrying hazardous materials (hazmat) to the general public. While there is a need to know, the dissemination of such information is contrary to both industry practice and Federal Railroad Administration (FRA) rules. The conundrum is that there needs to be disclosure to first responders, law enforcement, fusion centers and the like to ensure the security and safety of the public. This paper addresses the rules regulating the movement and handling of hazmat, to include toxic inhalation hazard (TIH) material; government demands, particularly those at the state level to release the routes, commodities, and quantities to the general public; and the operational impacts and risks that could result. It then explores the security of how hazmat train routing information can be safeguarded while ensuring that first responders and affected communities have what is needed to address the risks and be able to effectively respond to incidents. The overlaps and conflicts found in the rules and regulations of the Transportation Security Administration (TSA) and the Pipeline and Hazardous Material Safety Administration (PHMSA) are also addressed. Copyright © 2015 by ASME.

Bi J.,University of North Carolina at Charlotte | Fang H.,University of North Carolina at Charlotte | Wang Q.,Kal Krishnan Consulting Services Inc. | Ren X.,University of North Carolina at Charlotte
Finite Elements in Analysis and Design | Year: 2010

Thin-walled columns play an important role on passenger safety in vehicular collisions for their progressive deformation patterns and large energy absorptions. A thin-walled column with a large specific energy, i.e., the ratio of energy absorption to its mass, is often desirable to the automotive industry, because such designs could enhance safety and reduce manufacturing cost. Due to the complexity of crash mechanism, obtaining such designs has been a challenge to the trial-and-error approach using physical prototype testing. To this end, combining finite element simulations with optimization methodologies has become the viable means to meet the challenge. In this paper, singleand triple-cell hexagonal columns filled with aluminum foams were optimized for maximum specific energy with simultaneous consideration of section geometry, tube thickness, and foam density. The effects of crushing forces on column designs were analyzed by comparing optimum solutions with and without constraints on the mean crushing forces. The interaction effects between the tube and foam of composite columns and the relative advantages of single- and triple-cell structures were investigated and discussed. © 2010 Elsevier B.V. All rights reserved.

Caspe M.,Kal Krishnan Consulting Services Inc. | Ji J.,Kal Krishnan Consulting Services Inc. | Shen L.,Kal Krishnan Consulting Services Inc. | Wang Q.,Kal Krishnan Consulting Services Inc.
Sea Technology | Year: 2010

A marine barrier (MB) system has been developed to prevent waterborne terrorist attacks. explosives. The major challenges for MB systems are how to detect intrusions of the security perimeter both above and below the water, how to stop or deter such an intrusion to obtain enough time for response, and how to eliminate damage from different attacks. The MB system functions like a window blind with multiple layers of either horizontal or vertical openings that are small enough to block any possible paths for humans or underwater-vehicles to pass through. The MB is composed of a superstructure and substructure, the design of which has been driven by many practical considerations. Each MB superstructure panel uses two rotating-pin connections at the top, which connect to the underside of the deck. The separation of the superstructure and substructure systems is a natural choice to accommodate differential motions between the structure and seabed.

Hassing P.M.,University of North Carolina at Charlotte | Fang H.,University of North Carolina at Charlotte | Wang Q.,Kal Krishnan Consulting Services Inc.
Structural and Multidisciplinary Optimization | Year: 2010

In this paper, an optimization approach is adopted to obtain the 12 material parameters used in McGinty's Model for AL6022 by minimizing the differences between simulation and experimental stress-strain curves. Since the differences between the two stress-strain curves are implicitly related to the change of material parameters, the metamodeling technique is utilized to create explicit, approximate functions of these relationships. Radial basis functions (RBFs), which are shown from previous studies to be effective for both low-and high-order nonlinear responses, are used for the metamodels that are adaptively updated in the optimization work. Two optimization formulation schemes are studied to address the issue of using inaccurate RBF models in optimization. The sampling, metamodeling, and optimization works are performed using the integrated optimization framework HiPPO. © Springer-Verlag 2009.

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