Bridges Structural Health Monitoring and Deterioration Detection Synthesis of Knowledge and Technology

INE/AUTC 10.0

Simulation and Experimental Predictionss for the Structural Response of Satellites

This research investigated the structural response of satellites and space rated payloads. Throughout the work, SolidWorks Simulation was utilized to subject the aforementioned systems to both experimental test loads as well as program specific flight environments. While the methods presented within this document were exclusively employed with the SolidWorks Simulation software, all finite element analysis (FEA) techniques and computer aided design (CAD) best practices discussed are valid for a variety of commercially available CAD packages. Primarily, the programs under investigation were the Low earth Orbiting Navigation Experiment for Spacecraft Testing Autonomous Rendezvous and docking (LONESTAR) and Space-based Telescopes for Actionable Refinement of Ephemeris (STARE) programs. Both investigations studied satellite responses due to free and forced vibrations as well as various thermal environments and loading. Additionally, where experimental data was available, simulation solutions were validated against CAD generated values and evaluates for accuracy. Ultimately, the natural frequency and random vibration responses of four systems are presented as part of this research and the sensitivity of these results, due to various modeling variables, is discussed. The transient and steady state thermal profiles of two satellite flight configurations are also presented in an effort to predict on orbit thermal conditions. The CAD tool was evaluated and deemed appropriate for investigative studies within the laboratory

Mini-mast CSI testbed user's guide

The Mini-Mast testbed is a 20 m generic truss highly representative of future deployable trusses for space applications. It is fully instrumented for system identification and active vibrations control experiments and is used as a ground testbed at NASA-Langley. The facility has actuators and feedback sensors linked via fiber optic cables to the Advanced Real Time Simulation (ARTS) system, where user defined control laws are incorporated into generic controls software. The object of the facility is to conduct comprehensive active vibration control experiments on a dynamically realistic large space structure. A primary goal is to understand the practical effects of simplifying theoretical assumptions. This User's Guide describes the hardware and its primary components, the dynamic characteristics of the test article, the control law implementation process, and the necessary safeguards employed to protect the test article. Suggestions for a strawman controls experiment are also included

Aging concrete structures: a review of mechanics and concepts

The safe and cost-efficient management of our built infrastructure is a challenging task considering the expected service life of at least 50 years. In spite of time-dependent changes in material properties, deterioration processes and changing demand by society, the structures need to satisfy many technical requirements related to serviceability, durability, sustainability and bearing capacity. This review paper summarizes the challenges associated with the safe design and maintenance of aging concrete structures and gives an overview of some concepts and approaches that are being developed to address these challenges

Cooling Load Prediction for Different Building Types and Room Occupancy Detection Using Accelerometers

There are two parts in this thesis: the first part was conducted at UWM, and the second part was conducted at Johnson Controls using the knowledge and skills that I learned throughout my time in the Master’s Degree program. The primary purpose of my time at UWM was to compare different types of buildings with two popular machine learning regression algorithms, artificial neural network (ANN), supported vector machine regression (SVR) algorithms, and lastly to provide the results of my research to better help building managers make more informed decisions in regard to electrical utilities. The major objective is to use algorithms and neural networks to detect the occupancy of a room using real-time data from accelerometers. This data could then be used to enable HVAC systems to be more efficient and intelligent. My research at UWM consists of 6 chapters. The background and related research are shown first in chapter 1 and chapter 2. Chapter 3 focuses on analyzing different building types, which aims to provide an overlook in the feature of the data. The basic concepts of ANN and SVR are included in the Chapter 4. The last chapter is the summary of internship in Johnson Controls during the summer. The project goal, data analysis and results are presented with details. A brief occupancy detection review of the industry as well as the basic knowledge of Wavelet Transform and K-means++ algorithm are also mentioned in Chapter 7. The result of my research at UWM shows that it is necessary to apply different models for different building types if high accuracy is required. Compared to SVR, ANN is more accurate in all the building types. However, the difference of the accuracy depends on the building features. In a hospital, SVR and ANN both show high accuracy, but in restaurants, they are both underperforming. Additionally, using vibration magnitude measured from accelerometers to detect occupancy has proved to be feasible during the first stage. However, more complicated cases and patterns need to be considered and higher resolution sensors will need to be tested in the future work

OPERATIONAL MODEL ANALYSIS AND FINITE ELEMENT MODEL UPDATE USING AMBIENT VIBRATION DATA FOR AL-SINYAR TOWER

Buildings in Qatar rely on minimum structural code requirements implemented by design consultants’ offices. Qatar 2030 vision considers increasing of structures’ sustainability and serviceability as a high priority, which require testing structures under real full scale modeling. The process of monitoring structures’ behavior over time for aerospace, civil and mechanical engineering infrastructure is referred to as structural health monitoring (SHM). In Qatar, most high-rise building stability design is based on wind loading. According to Uniform Building Code3 1997 (UBC1997) which classifies seismic zones on a scale of zero to four, Qatar’s seismic classification on the scale is zero which is the minimum seismic risk value. Qatar Meteorological data on wind speeds enabled analysis of extreme winds to be undertaken in structural designs. This study aims to identify dynamic properties of the structural by using wired and wireless accelerometers in order to assess structural performance to update Finite Element Model (FEM). By updating FEM, engineers are enabled to support clients to make quick and correct decisions in extreme emergency situations in the case of boundary conditions changes and loads such as seismic vibration and wind pressure changes, during a structure’s life. The objective of this research is to apply and evaluate a single output-only procedure on a reinforced concrete tower building, Al Sinyar Tower, which consists of 2B+G+52 floors in Al Dafna Area in Qatar, with a total built up area of 74,747 sqm and is the tallest residential building in Qatar with a total height of 230 m . A Finite Element model using Sap2000 program was used to model and analyze building values in order to compare results with the real test results. The different forms of response data from ambient vibration were scrutinized to evaluate structure performance. Mode shapes, natural frequencies, modal damping ratios were studied, while the results of tests carried under ambient conditions were used to update the Finite Element model based on modules of elasticity, density and also connections fixity. The thesis concluded that wired sensors are not practical to use for low frequencies measurements in high rise buildings and that it is tremendously challenging and difficult to deal with more than 1000 meter long cables, especially with a very sensitive devices. Frequencies values from wired sensors could not been captured, whereas wireless connection provided more reasonable values. Ambient vibration results based on as-built environment provided higher frequency values in comparison to FEM because the stiffness provided by cladding, façade and walls eventually increased the system’s stiffness, which cannot be revealed in FEM based on structural drawings only. The foremost concept of Model Updating is to have an ideal simulation of structure that can represent real structure behavior. The Final Updated model results founded satisfactory according to modal assurance criterion (MAC) value with 98.9% and frequency deference errors average of 7.6%

Aeronautical Engineering: A continuing bibliography, supplement 120

This bibliography contains abstracts for 297 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980

Identification and proposed control of helicopter transmission noise at the source

Helicopter cabin interiors require noise treatment which is expensive and adds weight. The gears inside the main power transmission are major sources of cabin noise. Work conducted by the NASA Lewis Research Center in measuring cabin interior noise and in relating the noise spectrum to the gear vibration of the Army OH-58 helicopter is described. Flight test data indicate that the planetary gear train is a major source of cabin noise and that other low frequency sources are present that could dominate the cabin noise. Companion vibration measurements were made in a transmission test stand, revealing that the single largest contributor to the transmission vibration was the spiral bevel gear mesh. The current understanding of the nature and causes of gear and transmission noise is discussed. It is believed that the kinematical errors of the gear mesh have a strong influence on that noise. The completed NASA/Army sponsored research that applies to transmission noise reduction is summarized. The continuing research program is also reviewed