Stephen G. Buonopane

Bayesian analysis of uncertainty for structural engineering applications

There has been recent interest in differentiating aleatory and epistemic uncertainties within the structural engineering context. Aleatory uncertainty, which is related to the inherent physical randomness of a system, has substantially different effects on the analysis and design of structures as compared with epistemic uncertainty, which is knowledge based. Bayesian techniques provide powerful tools for integrating, in a rigorous manner, the two types of uncertainties. In a purely probabilistic viewpoint, the uncertainties merge, resulting in widened probability densities. From the viewpoint of design or experimentation, however, the two types of uncertainties have widely different effects. The purpose of this paper is to develop insight into these effects, using Bayesian-based analytical expressions for the aleatory and epistemic uncertainties. The paper goes beyond standard Bayesian conjugate distributions by incorporating the effects of model uncertainty, where the applicability of two or more analytical models are used to describe the structure of interest. The influence of multiple model uncertainties is explored for two problems: the Bayesian updating process as data is acquired, and the design of simple parallel systems.

Experimental Seismic Response of a Full-Scale Cold-Formed Steel-Framed Building. II: Subsystem-Level Response

AbstractThe objective of this paper is to employ the results from the extensive instrumentation installed on recently tested full-scale cold-formed steel (CFS)-framed buildings to reveal a deeper understanding of the behavior of the building under seismic excitations. In particular, this paper complements a companion paper that focuses on system-level design and response. Here, utilizing strategically located string potentiometers, strain gauges, and accelerometers, the responses of the walls and diaphragms are isolated from the overall building response and studied. The interaction of shear walls along a wall line, as well as across stories is studied through measured data on strains in hold-down anchors, strains on floor-to-floor strap connecting shear-wall chord studs, and displacements across shear-wall sheathing and openings. The behavior of the floor diaphragm is studied through displacements measured perpendicular to the plane of one wall of the building and accelerometers throughout the floor of t...

The Basics of Life Cycle Assessment (LCA) for Structural Engineers

Structural engineers are now expected to consider the environmental impacts of their designs, alongside the more traditional performance measures of strength, safety, serviceability and cost. Life cycle assessment (LCA) is a tool to analyze the environmental impacts of a building, from construction to end-of-life; thereby identifying ways to reduce those impacts. The application of LCA to the complex, inter-related nature of buildings represents a significant challenge and the field continues to develop rapidly. Nevertheless, LCA is becoming an important tool in the building design industry, and structural engineers need to be conversant in the basics of LCA. This paper will introduce fundamental concepts of LCA of buildings allowing structural engineers to become more involved in the sustainable building design process.

The Technical Writings of John A. Roebling and his Contributions to Suspension Bridge Design

John A. Roebling designed some of the longest and most well-known suspension bridges of the 19th century. Roebling developed a hybrid suspension bridge form, combining a suspension cable with inclined stays and a stiffening truss. Roebling’s technical writings reveal his skills as an engineer—proficient with theory, but able to draw on experience and observation. Roebling relied on approximate design methods and possessed a deep understanding of structural behavior. Roebling’s suspension bridges pushed the limits of the 19th century bridge design, and they inspired the development of more exact structural analysis methods. Roebling’s stayed suspension bridge system represents an extremely safe and economical system for long span bridges. Although rarely built after Roebling’s career, variations of the stayed suspension bridge continue to be proposed for very long spans.