Eric Kjolsing Archives

News & Views, Volume 47 | Aircraft Impact Assessments for NUSCALE Power

March 3, 2020/in Critical Structures, Eric Kjolsing, News and Views, Structural Assessments/by Structural Integrity

By: Eric Kjolsing, Ph.D., PE

From 2015 to 2019 Structural Integrity Associates, Inc. (SI) worked with NuScale Power,LLC. to develop structural details for and perform aircraft impact assessments of NuScale’s SMR Reactor Building. The assessments were based on finite element analyses of various strike scenarios stemming from NEI 07-13 guidance. ANACAP, a proprietary SI concrete constitutive model, was used in the finite element analyses. Among other capabilities, the ANACAP model can capture multi-axial tensile cracking, compressive crushing with strain softening, and crack dependent shear stiffness.

News & Views, Volume 46 | Identifying Failure Mechanisms of Typical I-Section Floodwalls

July 1, 2019/in Critical Structures, Dan Parker, Eric Kjolsing, Hydroelectric Power, News and Views/by Structural Integrity

By: Eric Kjolsing and Dan Parker

News & View, Volume 46 | Identifying Failure Mechanisms of Typical I-Section Floodwalls In 2018, Structural Integrity Associates, Inc. (SI) supported the United States Army Corp of Engineers (USACE) in the structural assessment of the concrete-to-steel connection in typical I-Section flood walls. A representative flood wall section is shown in Figure 1. This effort was part of a broader scope of work in which the USACE is revising their guidance for the design of flood and retaining walls, EM 1110-2-6066. The purpose of the structural assessment was to better understand the mechanics of load transfer from the reinforced concrete section to the embedded sheet pile. Three-dimensional finite element models of the connection were developed employing non-linear constitutive properties for the concrete, structural steel and reinforcement to achieve this goal. A total of nine different I-Wall configurations with varying wall geometry, sheet pile embedment depth, and connection details were analyzed. Hydrostatic load was applied incrementally to simulate the actual load distribution due to a rising water level.

News & Views, Volume 46 | Assessing Prestress Losses in a Nuclear Containment Structure for License Renewal

July 1, 2019/in Critical Structures, Eric Kjolsing, News and Views, Nuclear Asset Integrity, Nuclear Energy/by Structural Integrity

By: Eric Kjolsing

Nuclear power plants around the world are approaching the end of their original 40-year design life. Efforts are underway to extend the operating license for these plants to 60 years or beyond. As part of the license extension, it must be demonstrated that the reactor containment building remains able to safely perform its intended functions for the extended duration of operation. Many of these containment buildings utilize a post-tensioned concrete design where the tendons are grouted after tensioning. Since these grouted tendons cannot be re-tensioned, an assessment for the loss in prestress beyond the original design life must be performed.

This article describes a methodology to assess the structural performance of a containment structure over time as a function of confidence in the tendon losses and is split into three parts:

A description of the methodology
A representative probabilistic assessment
Representative analysis results

News & Views, Volume 46 | Adding Value Through Test Informed Modeling: Hydro Structures

July 1, 2019/in Critical Structures, Dan Parker, Eric Kjolsing, Hydroelectric Power, News and Views, Structural Assessments/by Structural Integrity

By: Eric Kjolsing and Dan Parker

In 2018, Structural Integrity Associates (SI) supported a utility in the structural assessment of a submerged concrete intake tower. The tower is nearly a century old and was investigated as part of the utility’s periodic maintenance program.

The assessment required the generation of an analysis model that accounted for both the structure and the surrounding water. When accounting for fluid effects, a typical analysis approach is to develop a fluid-structure interaction (FSI) model that explicitly accounts for the interaction between the surrounding water and concrete tower. However, this modeling approach is expensive both in terms of (a) cost, due to the increased effort needed in generating the model and (b) schedule, due to the increased analysis run time. In lieu of developing an FSI model, SI implemented an alternative numerical approach to model the effects of the water and justified the approach through physical testing of the in-situ structure.

News & Views, Volume 45 | Improved Asset Management Through Test Informed Analysis

January 1, 2019/in Complex Loadings, Critical Structures, Eric Kjolsing, Hydroelectric Power, News and Views, Structural Assessments/by Structural Integrity

By: Eri Kjolsing

Introduction
Structures may experience unforeseen operating environments or site-specific hazards leading to changes in the structure’s performance, safety, and longevity. These changes often prompt asset owners to undertake analysis efforts to ensure satisfactory structural performance for the updated conditions. However, conventional analyses that fail to capture the true behavior of a structure can lead to inaccurate analysis results, causing owners to make less than ideal asset management decisions. Structural Integrity (SI) is uniquely positioned to pair our dynamic characterization and advanced structural analysis capabilities to generate a better structural model. SI vibration experts use impact testing, forced vibration, or ambient excitation sources, along with proprietary signal processing software, to non-destructively characterize the dynamic behavior of structural systems. This characterization is used to inform advanced structural analyses by SI analysis experts to provide more accurate results related to operational improvements, damage location, and retrofits.

News & View, Volume 43 | Perforation, Scabbing, and Reinforcement Optimization in an Aircraft Impact Analysis (AIA)

News & Views, Volume 43 | Perforation, Scabbing, and Reinforcement Optimization in an Aircraft Impact Analysis (AIA)

October 5, 2017/in Complex Loadings, Critical Structures, Eric Kjolsing, News and Views/by Structural Integrity

By: Eric Kjolsing

Background
A 2016 project utilized a variety of Structural Integrity competencies to analyze a beyond design basis threat at an overseas nuclear power plant. The client was assessing a plant design and approached Structural Integrity to investigate local perforation and scabbing of a reinforced concrete wall due to hard missile impact. Perforation occurs when a missile fully penetrates and passes through a target while scabbing occurs when material is ejected from the back face of a target, potentially striking personnel and equipment inside the facility. The client also sought to reduce the volume of wall reinforcement, a potentially large cost savings, while still meeting the facility’s strict design criteria. The project is best described in four stages and took advantage of our AIA experience, finite element (FE) modeling expertise, and proprietary concrete constitutive model ANACAP.

News & Views, Volume 43 | Advanced Structural Analysis

October 5, 2017/in Complex Loadings, Critical Structures, Eric Kjolsing, Hydroelectric Power, News and Views, Structural Assessments/by Structural Integrity

By: Eric Kjolsing & Philip Voegtle

The sophistication of structural analysis has evolved side-by-side with computing and graphics technology. Structural engineers have at their fingertips very powerful software analysis tools that assist them in evaluating very large and complex structures for stability, suitability, and code adequacy. The tools themselves vary in complexity in proportion with the engineering analysis required of them – the most complex and unique engineering problems requiring the most advanced analysis tools. Structural Integrity is a leader in advanced structural analysis (ASA), utilizing state-of-the-art software and material science expertise to solve an array of structural and mechanical problems.

Structural analysis, in its most basic definition, is the prediction of the structural performance of a given structure, system, or component to prescribed loads, displacements, and changes in temperature. Common performance characteristics include material stresses, strains, forces, moments, displacements and support reactions. The results from a structural analysis are typically compared to acceptable values found in design codes. Meeting the design code acceptance criteria ensures a design that protects the public’s health, safety, and welfare.

ASA extends this basic definition of structural analysis to one-of-a-kind problems where the acceptance criteria may not be well defined. Since loads, material behavior, or the structure itself can go beyond the scope of basic design codes, ASA requires an in-depth understanding of modeling techniques, software limitations, and non-linear material behavior. In ASA, sophisticated finite element analysis solvers are utilized to gain a detailed understanding of a system’s non-linear mechanical behavior, providing a full three-dimensional view of the critical stresses and strains in a loaded system.