Papers by Gilbert Hegemier
Journal of the Structural Division
A method for incorporating interface discontinuities in a finite element analysis of discontinuou... more A method for incorporating interface discontinuities in a finite element analysis of discontinuous media is presented. For computational purposes the procedure is implemented into the nonlinear structural analysis program NONSAP. Several example problems concerning the modeling of concrete masonry mortar joints are presented, and demonstrate the accuracy and efficiency of the algorithm.
Cold-formed steel sheathed shear walls are now emerging as a strategic vertical lateral load resi... more Cold-formed steel sheathed shear walls are now emerging as a strategic vertical lateral load resisting component in seismic design. However, although a number of component cyclic test programs have been conducted in recent years to characterize their hysteretic behavior and guide design, system-level test programs to investigate their performance are so far lacking in the literature. To this end, a unique full-scale CFS-framed mid-rise building shake table test program was conducted to contribute to understanding the behavior of mid-rise cold-formed steel (CFS) wall-braced buildings under a multi-hazard scenario. The centerpiece of this project involved earthquake and live fire testing of a fullscale six-story CFS wall braced building constructed on the Large High Performance Outdoor Shake Table (LHPOST) at UCSD. This paper first provides a brief overview of the test program and summarizes the system-level (global) response of the test building during the shake table tests. Subsequently, a key focus of this paper is comparison of the component-level responses of various shear wall systems of the test building as well as their physical damage.
Journal of Structural Engineering, 2021
AbstractTo advance understanding of the multihazard performance of midrise cold-formed steel (CFS... more AbstractTo advance understanding of the multihazard performance of midrise cold-formed steel (CFS) construction, a unique multidisciplinary experimental program was conducted on the Large High-Perf...
The stability of an infinite-length cylindrical shell subjected to a broad class of axially symme... more The stability of an infinite-length cylindrical shell subjected to a broad class of axially symmetric moving loads with constant velocity is studied by utilizing a large deflection Donnell theory. Special cases of the general loading function include the moving ring, step and decayed step loads. Stability is defined on the basis of the boundedness or divergence of an infinitesimal nonsymmetric disturbed motion about an initial nonlinear steady-state symmetric response. Following the determination of the symmetric response, under this concept of stability, the analysis is reduced to a study of a system of linear partial differential equations or so-called variational equations; these are analyzed by use of a double Laplace transform technique and the original stability problem is replaced by a simpler one of determining the location of the poles of a certain function. A scheme for accomplishing this task is outlined. Extension of the method to include more exact equations of motion a...
: This Technical Report is the product of a series of meetings held by the technical staff and co... more : This Technical Report is the product of a series of meetings held by the technical staff and consultants of The BDM Corporation at the request of, and in cooperation with, representatives of DARPA. The motivation for holding these meetings, and associated technical analyses, was DARPA's interest in large-scale computer calculations of the effects of strong shocks in solids. In addition to related topics, the meetings primarily addressed the subject of improving communication and collaboration between solid mechanics researchers whose principal interest is inelastic constitutive material characterization and numerical analysts whose principal interest is the development and practical use of large computer codes for complex defense related problems.
Innovative Bridge Design Handbook, 2016
Fiber-reinforced polymer (FRP) materials and their integration with reinforced concrete (r.c.) st... more Fiber-reinforced polymer (FRP) materials and their integration with reinforced concrete (r.c.) structural systems represent an important strategy in the design of protective and performance-enhancing technologies for bridges subjected to a variety of extreme loads. This chapter discusses applications of FRPs as retrofits to bridge designs for use in mitigating the negative response and damage from seismic, blast, and other loading events, within the context of large-scale testing performed over three decades at the Powell Structural Research Laboratories at the University of California, San Diego. This overview includes structural elements such as reinforced concrete columns and superstructure elements for bridges. The applications treated include retrofits and repairs of existing structures and for new constructions. The FRP material systems considered consist of carbon, aramid, or glass fibers in epoxy or matrices. The fabrication methods associated with these FRPs include field wet lay-up or spray-up-generated composite overlays using fabrics, strips, and nets. A number of example applications of the FRP technologies are considered and references to code details are included.
Proquest Dissertations and Theses Thesis University of California San Diego 1998 Publication Number Aai9835372 Isbn 9780591888171 Source Dissertation Abstracts International Volume 59 05 Section B Page 2329 240 P, Nov 1, 1998
Design of bladder expulsion device subjected to constraints such as cycle life, chemical inertnes... more Design of bladder expulsion device subjected to constraints such as cycle life, chemical inertness, and storability
An experimental study of the behavior of various structural elements subjected to repeated dynami... more An experimental study of the behavior of various structural elements subjected to repeated dynamic loadings is reported. The purpose of the investigation was to provide experimental evidence leading to a fuller understanding of the behavior of building structures which are exposed more than once to the blast waves of a nuclear explosion. The specimens tested include pinned and fixed-base rigid frames and portal-frame knee connections. All loadings, both static and dynamic, were applied by the atomic blast simulator at the U. S. Naval Civil Engineering Laboratory. The test results are presented and a comparison is made with analytical calculations based on a simple structural theory. It was concluded from this comparison that the elementary theoretical procedures employed are adequate when applied to damage assessment studies. (auth)
Optimization in Structural Design, 1975
General Remarks. The optimal design of continuous or pieeewise continuous structural systems can ... more General Remarks. The optimal design of continuous or pieeewise continuous structural systems can be approached along two avenues. On one hand the system can be discretized at the outset and a sequence of problems involving refined domains may be studied in an effort to extract an approximate optimal solution. On the other hand, the continuous nature of the problem may be recognized and optimality criteria for the continua sought directly.
Journal of Applied Mechanics, 1974
A hierarchy of approximate elastodynamic plate theories is deduced from the three-dimensional equ... more A hierarchy of approximate elastodynamic plate theories is deduced from the three-dimensional equations of elasticity. The derivation is based upon asymptotic expansions in a parameter viewed as the ratio of plate half thickness to a dominant signal wavelength of motion. Approximate theories of any desired order of accuracy are contained in a single compact set of partial differential equations with the order of approximation determined by the order of truncation of the differential operators appearing in the equations. As examples, particular cases of free extensional and forced flexural vibrations are studied. Lower-order theories for these cases are compared to some existing approximate theories of the same order.
Accession Number : AD0725745. Title : Optimal Structural Design. Descriptive Note : Final rept. O... more Accession Number : AD0725745. Title : Optimal Structural Design. Descriptive Note : Final rept. Oct 69-Oct 70,. Corporate Author : BELL AEROSPACE CO BUFFALO NY. Personal Author(s) : Gellatly,Ronald A. ; Berke,Laszlo. Report Date : APR 1971. ...
Journal of Hydronautics, 1979
The dynamic stability of faired, heterogeneous underwater cables subject to small perturbations f... more The dynamic stability of faired, heterogeneous underwater cables subject to small perturbations from a planar towing configuration is considered. Sufficient conditions for freedom from flutter and divergence are obtained using the velocity component strip theory. These conditions are given in the form of constraints on the locations of shear center, center of tension, hydrodynamic center, and center of gravity of the cable cross section.
AIAA Journal, 1977
A large deformation, small-strain theory is presented for heterogeneous, transverse isotropic, el... more A large deformation, small-strain theory is presented for heterogeneous, transverse isotropic, elastic rods with pre-twist. The theory is applicable to practical problems related to the dynamics of cable systems, helicopter blades, space antennae, and similar structures. Two elementary examples are included: reduction of the general theory to particular differential equations governing the planar, steady-state towing of cables, and the steadystate motion of helicopter rotor blades.
: The objective of the research is to develop a new and advanced approach to modeling the constit... more : The objective of the research is to develop a new and advanced approach to modeling the constitutive behavior of reinforced concrete that provides substantial improvement over existing approaches, especially in the nonlinear response regime. To accomplish this, the research has been partitioned into two major tasks, which are being pursued concurrently. One task consists of formulating a procedure (mixture theory) for analytically mixing reinforcing steel and plain concrete, so that the interaction between the two is properly modeled. The other task consists of developing a model of plain concrete, which accurately portrays its nonlinear, multiaxial behavior and is also computationally feasible for use in conjunction with the mixture theory. The mixture theory is designed to synthesize the global constitutive properties of reinforced concrete from the properties of plain concrete, steel, interfaces and reinforced geometry. The progress made during the first year's effort towar...
International Journal of Solids and Structures, 1980
ABSTRACT A nonlinear mixture theory with microstructure is constructed for quasi-one-dimensional ... more ABSTRACT A nonlinear mixture theory with microstructure is constructed for quasi-one-dimensional heat conduction in fiber-reinforced composites. The nonlinearities considered result from temperature dependent thermal properties. In an attempt to infer the accuracy of the mixture theory, an initial boundary-value problem is selected and a finite difference solution of the mixture equations is compared with a finite element solution of the original equations. Excellent agreement is found between the two solutions for both global and micro-temperature fields. System sensitivity to nonlinearities is examined via numerical treatment of the mixture equations for Graphite/Epoxy and Carbon/Carbon composites. The results imply that variations of thermal properties with temperature can lead to significant differences between linear and nonlinear solutions.
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Papers by Gilbert Hegemier