Theodor Krauthammer

Thin Plates and Shells : Theory: Analysis, and Applications

Part 1 Thin plates: introduction the fundamentals of the small-deflection plate bending theory rectangular plates circular plates bending of plates of various shapes plate bending by approximate and numerical methods advanced topics buckling of plates vibration of plates. Part 2 Thin shells: introduction to the general linear shell theory geometry of the middle surface the general linear theory of thin shells the membrane theory of shells applications of the membrane theory to the analysis of shell structures moment theory of circular cylindrical shells the moment theory of shells of revolution approximate theories of shell analysis and their application advanced topics buckling of shells vibration of shells. Appendices: some reference data Fourier series expansion verification of relations of the theory of surfaces derivation of the strain-displacement relations verification of equilibrium equations.

Negative phase blast effects on glass panels

The main focus of this study has been the assessment of blast waves negative phase effects on glass panels. An approximate numerical model for the dynamic response simulation of glass panels subjected to blast loading has been developed, including stochastic considerations of the glass flaw characteristics. A parametric study was conducted and the results showed that glass panels would exhibit different responses at different scaled ranges, and for different charge sizes.

Blast-resistant structural concrete and steel connections

A series of numerical studies were conducted on the behavior of structural concrete and structural steel connection subjected to blast loads. These studies gradually enhanced the understanding of the role that structural details play in affecting the behavior. Observations from those studies highlighted possible safety concerns with current blast design procedures. Conclusions and recommendations are provided for correcting the observed problems.

Analysis of impulsively loaded reinforced concrete structural elements. I: Theory

Abstract A computational approach is presented for the analysis of reinforced concrete beams and slabs under the effects of transient uniformly distributed loads. This approach is based on the Timoshenko beam formulation with non-ideal support conditions. In addition, non-linear material properties, strain are effects, load-reversals, and rational structural behavior models have been included. The solution is achieved by implementing an explicit finite difference formulation. The numerical aspects of the problem are treated and the issue of stability and convergence are addressed.

Response of structural concrete elements to severe impulsive loads

Abstract The behavior and response of structural concrete elements under severe short duration dynamic loads was investigated numerically. The analytical approach utilized the Timoshenko beam theory for the analysis of reinforced concrete beams and one-way slabs. Nonlinear material models were used to derive the flexural and shear resistances, and the differential equations of the Timoshenko beam theory were solved numerically by applying the finite difference technique. A simplified approach was developed for estimating the strain rate in structural concrete members, and the corresponding strain rate effects on the strength of the steel and concrete were incorporated into the analysis. Detailed failure criteria were established for predicting the collapse of structural concrete members. Five cases subjected to localized impact loads and eleven cases subjected to distributed explosive loads were analyzed, and the results were compared to experimental data obtained by other investigators.

ASSESSMENT OF NUMERICAL SIMULATION CAPABILITIES FOR MEDIUM-STRUCTURE INTERACTION SYSTEMS UNDER EXPLOSIVE LOADS

Abstract This study was aimed at assessing the capabilities to numerically simulate a dynamic medium-structure interaction system composed of geologic backfills, a shock insulation material, an explosive charge, and a partially-buried structure. Conventional high explosive charges were detonated at the same depth, but at various stand off distances from the structure. The finite element code DYNA3D was employed for estimating the relationships between the physical parameters of the problem and the behavior of the system. The results of the finite element analysis were then compared to test data gathered from field experiments and predictions from simpler computational methods.

Mesh, gravity and load effects on finite element simulations of blast loaded reinforced concrete structures

Abstract The behavior and design of reinforced concrete blast resistant structures are supported by intensive numerical simulations, and the effects of various parameters on the results is of great interest. Finite element simulations were performed in the nonlinear dynamic domain with modified concrete and steel constitutive models. Ten different cases were implemented, each with different reinforcement details. In addition, each case included both a coarse mesh and a fine mesh to determine the effects of mesh resolution on the numerical simulations. Gravity and loading conditions were altered to investigate their influences on the results. Deformations and stress distributions in both the concrete and steel were examined to determine the composite structural behavior and the extent of predicted damage for the various cases. The observations from these analyses highlighted relationships between the simulation parameters and the corresponding outcome. Conclusions and recommendations are presented that could assist in the development of efficient numerical simulations in this general area.

Analysis of impulsively loaded reinforced concrete structural elements—II. Implementation

Abstract The theoretical/numerical approach presented in part I of this paper is implemented for the response analysis of roof slabs in reinforced concrete box-type structures tested at the U.S. Army Waterways Experiment Station. The assumptions, and the specific cases are discussed prior to the analyses. For each test element, the sequence of events that lead to the post-test conditions have been investigated. These analyses provided complete dynamic deflection profiles for the structures, dynamic shear distributions, and dynamic moment distributions along the span of the roof slab. Comparisons with previous numerical findings are presented when applicable.

A hybrid computational approach for the analysis of blast resistant connections

The behavior, response and role of reinforcing bars in structural concrete knee-joints under explosive opening loads has been studied numerically. A hybrid finite element (FE)-finite difference (FD) approach was developed for this purpose, in which the connection region was simulated by the FD part of the approach and the adjoining members were represented with the FE code DYNA3D. Nonlinear material models for concrete and steel were employed, and the effect of bar size and location in the connection were studied. The proposed approach is described, and findings, conclusions and recommendations are presented.

An UNDEX response validation methodology

Abstract The assessment of the response of naval vessels to underwater shock creates a need for tools that can analyze and design such systems to withstand underwater explosions (UNDEX). This paper describes a preliminary attempt to develop a methodology for the assessment of structural systems to UNDEX effects. A methodology is proposed by which the response of a simplified structural component to UNDEX can be validated through the use of precision impact testing and numerical simulations. An iterative process was used where an UNDEX response, determined through previous results, preliminary UNDEX simulations, and impact simulations, provided the parameters necessary for a precision impact test that generates an equivalent response. Precision impact tests were performed, and the results correlated with the impact simulated data. The results from an UNDEX test were compared with the predictions from the validated numerical code. The structural component in both the tests and simulations was simplified to a flat rectangular panel. The numerical simulations were solved explicitly, and included either the impact loading environment—a hybrid impactor with an initial velocity—or the UNDEX loading environment—a plane shock wave applied to the surface of the target structure. Since close-in and early time UNDEX-related phenomena, such as gas bubble effects, are localized and very complicated, they were ignored in this preliminary phase of the study. Although the proposed methodology could require multiple iterations, the limited scope of this study only included one set of precision-impact tests on each type of material, one UNDEX test against an aluminum panel, and two UNDEX tests against composite panels. Once the methodology using precision shock testing and numerical simulations to validate the UNDEX response had been developed, it was used to develop a “design-for-shock” procedure.