Luciana R. Barroso

Active and Semi‐active Adaptive Control for Undamaged and Damaged Building Structures Under Seismic Load

: During the lifetime of a structural system, many severe events such as earthquakes and strong winds may impact the system and result in potential damage. To mitigate the structural vibration and damage during these extreme events, control devices such as active and semi-active devices have received considerable attention because of their attractive characteristics. Active control devices are adaptable to any change and semi-active devices have the capability of offering the reliability of passive devices and the versatility and adaptability of active devices. In this research, a direct-adaptive-control method is used to control the behavior of an undamaged and a damaged structure using semi-active and active devices. In the adaptive control method, the controlled system is forced to behave like the model system which exhibits the desired behavior. The model of the adaptive control method is defined in a way to optimize the response of the controlled structure. The controller developed using this method can deal with changes that occur in the characteristics of the structure because it can modify its parameters during the control process. A magnetorheological (MR) damper is used as the semi-active device in this study, whereas a hydraulic actuator is utilized as the active device to control the behavior of the structure. The performance of a three-story building from the SAC project for the third generation of the control benchmark problem is studied by performing time–history analyses. The structure is subjected to different earthquakes and controlled by the direct adaptive control method. In the analysis of the structure, some stiffness reduction is assumed as a result of potential damage in the first story of the building. Also, the direct adaptive control strategy is used to optimize the response of the undamaged structure and to mitigate the damage impact on the performance of the controlled structure in the presence of noise for output measurements. The results of adaptive control method are compared with those of other control strategies. It is shown that the performance of the three-story building is improved using the adaptive control method. By assessing the results of different control approaches, it is found that the adaptive control method works more effectively than other methods and semi-active devices can provide reliable results.

Adaptive Control to Mitigate Damage Impact on Structural Response

The use of semi-active devices for natural hazard mitigation is particularly attractive as they do not destabilize the structure and have the ability of adapting to varying usage patterns and loading conditions. However, even in the presence of supplemental control devices, extreme earthquake, wind loads, and deterioration caused by corrosion or fatigue may result in structural damage. Adaptive control approaches are attractive methods to control the structural performance of the structure as it can deal with these changes. In this study, first, the behavior of a 3-story building is controlled by a direct adaptive control approach using active devices, and then, magnetorheological (MR) dampers are controlled by the direct adaptive method. This control approach is used to reduce the impact of damage in the 3-story building. In the analysis of the structure, some stiffness reduction is assumed as a result of potential damage in different stories of the building. The controlled damaged structure responses under different ground motions are presented and compared with the uncontrolled damaged structure behavior. The goal of the adaptive control method in this research is to force the damaged structure to behave like an undamaged structure which performs acceptably. The effectiveness of this method in controlling the MR dampers is then verified.

Stiffness-mass ratios method for baseline determination and damage assessment of a benchmark structure

The benchmark problem on structural health monitoring developed by the ASCE Task Group on Structural Health Monitoring (TGoSHM) is addressed in this paper. This problem is a four-story steel building model created to compare performances of different vibrational damage identification methods. A new method based on ratios between stiffness and mass values from the eigenvalue problem is introduced and applied to the benchmark structure to obtain baseline modal parameters utilizing damaged state information. Next, location and severity of damage is carried out using the damage index method for all six existing damage patterns established by TGoSHM. This research will be of interest to structural engineers and inspection practitioners who deal with structural damage identification problems and who will corroborate the feasibility in terms of easiness of the proposed methodology.

Active demonstrations for enhancing learning

Demonstrations can be very effective at engaging students, generating interest in a topic, and enhancing student learning. A key component to an effective demonstration is active student engagement throughout the entire process. This means students are involved in discussing the purpose of the demo; predicting what will happen during the demo; discussing who developed theories to help us understand what happens during the demo; and comparing observations to predictions, as opposed to simply passively watching a demonstration. Demonstrations can occur at three different stages of a course topic: as an introduction, as a wrap-up and an aid used throughout the class discussion of a topic. Depending on when they occur, different types of learning outcomes are achieved. This paper presents a model for infusing demonstrations into an engineering science class and the use of this model during a semester. Assessment includes components from both faculty and students, as well as from a faculty development professional who is an instructor in a different discipline.

Engineering better projects

The requirements for a successful career in the 21st century are completely different than they were in the 20th century. With the ever changing technological advances and new problems being identified daily, we must prepare students for jobs and challenges that possibly do not even exist today. Therefore, students must be equipped with problem-solving skills that enable them to systematically find solutions regardless of the specific problem they face. In addition, the Internet has made information easily and quickly accessible, which has caused a shift from the need for memorization to learning how to acquire valid information and create new information based on observations and analysis. Machines have also decreased the need for unskilled labor, making it vital that our students know how to apply concepts instead of merely understanding concepts. These new demands are the reason engineering, Project-Based Learning (PBL), and the design process are now a focus in 21st century curricula.

Utilizing reflection in projects for increased metacognition and enhanced learning

Active and project-based learning (PBL) strategies provide a great means for students to enhance their learning and further develop critical engineering skills. In order to guide students to a higher level of learning, a critical reflection process has been incorporated into upper level and graduate civil engineering classes that utilize PBL. This paper presents a model for classroom practice for enhancing student skill development through critical reflection as part of PBL that is based on existing theory on learning.

Incorporating peer review of course term project in structural analysis course

Students frequently find their junior year challenging as those courses provide the transition between lower-level courses where fundamentals are emphasized and upper-level design courses where instructors assume prior knowledge. Project-based learning provides a great instrument for students to enhance their learning and further develop critical engineering skills. However, students still struggle when not given exact procedural steps and want the reassurance they are ‘doing the correct thing.’ This paper presents the implementation of a peer-review cycle into the team course project of a structural analysis course. The peer review process asks students to evaluate and provide feedback on both the analytical content as well as the written presentation of the project. This process allows students to see different approaches, both in analysis and in presentation, to the same problem. Their familiarity with the problem allows them to provide constructive feedback, while reviewing the work of another group allows them an objectivity they cannot yet apply to their own work. The peer review cycle not only enhances the learning of the material for the course, but it is also a critical engineering skill for students.

Effects of structural modeling on seismic performance estimation of controlled steel structures

The determination of seismic demands on a structure are based on several assumptions concerning the structural parameters and modeling. The response of any structure depends on careful selection of those parameters so as to capture the significant effects of the structure. The focus of the study is to evaluate the effect of selected parameters on the demand estimation of a controlled structure under severe seismic demands. The parameters investigated here are: 1) the level of nonlinear modeling and analyses of the structure, 2) the initial stiffness of the structure, and 3) the strain-hardening assumptions in force-deformation relationships of the elements.

Implementing reflection in technical courses

Students do not necessarily learn from an experience, particularly if they do not think about it or do not take responsibility for it. Reflective learning is a mechanism to address this issue and has been demonstrated to aide in the development of critical thinking, self-awareness and analytical skills, all critical to engineering education. This paper presents the experiences of the authors in incorporating reflections into a range of analytical engineering courses, from undergraduate to graduate level. The reflections target specific activities as well as reflecting on the whole-course experience.

Classroom demonstrations with multiple modes: Virtual + reality = enhanced learning

Demonstrations can be very effective at engaging students, generating interest in a topic, and enhancing student learning. Demonstrations can occur at three different stages of a course topic: as an introduction, as a wrap-up and an aid used throughout the class discussion of a topic. A key component to an effective demonstration is active student engagement throughout the entire process. This means students are involved in discussing the purpose of the demo; predicting what will happen during the demo; discussing who developed theories to help us understand what happens during the demo; and comparing observations to predictions, as opposed to simply passively watching a demonstration. This paper presents a model for infusing demonstrations into an engineering science class and the use of this model during a semester. Demonstrations in this class incorporate both software simulation and physical models of dynamic systems. While physical models provide a concrete example, computer simulations allow the exploration of ldquowhat-ifrdquo scenarios and greater meta-cognitive activities. Assessment includes components from both faculty and students.