Neil C. Mickleborough

Optimal Sensor Placement Methodology for Identification with Unmeasured Excitation

A methodology is presented for designing cost-effective optimal sensor configurations for structural model updating and health monitoring purposes. The optimal sensor configuration is selected such that the resulting measured data are most informative about the condition of the structure. This selection is based on an information entropy measure of the uncertainty in the model parameter estimates obtained using a statistical system identification method. The methodology is developed for the uncertain excitation case encountered in practical applications for which data are to be taken either from ambient vibration tests or from other uncertain excitations such as earthquake and wind. Important issues related to robustness of the optimal sensor configuration to uncertainties in the structural model are addressed. The theoretical developments are illustrated by designing the optimal configuration for a simple 8-DOF chain-like model of a structure subjected to an unmeasured base excitation and a 40-DOF truss model subjected to wind/earthquake excitation. @DOI: 10.1115/1.1410929#

Shear Strength of Joints in Precast Concrete Segmental Bridges

The behavior of precast concrete segmental box girder bridges at both serviceability and ultimate strength conditions is dependent on the behavior of the joints between the segments. To accurately predict the bridge response throughout the complete range of loading. knowledge of joint behavior is essential. In this study, a series of full-scale joints, flat and keyed, dry and epoxied, single-keyed and multiple-keyed, have been tested under different confining stress levels and epoxy thicknesses. The shear behavior shear capacity, and shear transfer mechanisms of these different kinds of joints have been studied. It was determined that the shear capacity of joints increased as confining pressure increased, and epoxied joints had consistently higher shear strength than dry joints; however; the failure was more brittle than dry joints. The average shear strength for a key in multiple-keyed dry joints was always found to be less than those in single-keyed dry joints due to imperfections in fitting of keys. The shear strength of keys in multiple-keyed epoxied joints, flowever was similar to those in single-keyed joints, indicating epoxy mitigated the fixing imperfections and permitted the shear load to be uniformly distributed. The experimental results obtained in these tests were compared with the AASHTO and other design criterion. It was seen that these relationships tended to underestimate the shear strength of single-keyed joints and multiple-keyed epoxied joints by a value up to 40%, but they always greatly overestimated the shear capacity of dry multiple-keyed joints. Hence, the results indicate that some strength reduction factors should be introduced to the design relationships when applied to multiple-keyed dry joints.

Lateral stiffness characteristics of tall reinforced concrete buildings under service loads

This paper presents an analytical method for quantitatively predicting the effects of cracking on the lateral deflection and stiffness characteristics of tall reinforced concrete buildings under service loads. The effects of cracking in tall reinforced concrete buildings can be considered using an element stiffness reduction model. This model determines the probability of cracking occurrence by dividing the area of the moment diagram, Scr, where the working moment exceeds the cracking moment by the total area of the moment diagram, S. A practical cracking analysis method can be established by integrating the proposed stiffness reduction model with an iterative algorithm and commercial linear finite element analysis package. The proposed method has been validated by good agreement of results between the numerical computation and experimental testing of large-scale rigid-frame and wall-frame structural sub-assemblages. The effectiveness of the numerical analysis method is also illustrated through a practical 40-storey reinforced concrete building example. The cracking effects on the lateral deflection and stiffness characteristics of this building were analysed both explicitly and quantitatively. Copyright

Modal identification of a vibrating structure in the time domain

Abstract This paper presents a general time domain method for the identification of modal parameters of a linear vibrating structure. The vibrating structure is represented by a multivariate autoregressive and moving-average (ARMA) model and the modal parameters are related to the coefficient matrices of the ARMA model. Using multiple excitation and multiple response data the modal parameters are identified through an estimate of the coefficient matrices of the ARMA model. The modal parameters, which include highly coupled and pseudo-repeated modes, can be identified with good accuracy. This method can also be reduced to the least square complex exponential method, the poly reference time domain method, the Ibrahim time domain method and the mathematical model method. The free decay response or impulse response data can also be used with the present method.

Promoting collaborative problem-solving skills in a course on engineering grand challenges

The ability to solve problems with people of diverse backgrounds is essential for engineering graduates. A course on engineering grand challenges was designed to promote collaborative problem-solving (CPS) skills. One unique component is that students need to work both within their own team and collaborate with the other team to tackle engineering challenges. It is found that the course facilitates the development in CPS skills and that the process, in which two teams develop arguments and integrate the initial ideas to generate a final solution, is a critical component. The value of CPS skills in tackling engineering problems has also been demonstrated. Appropriate scaffolding, explicit training and constant feedback on collaborative processes are found as important for the skill development.

Students as learning experience designers: the effect of student-driven approaches in a Hong Kong study

Abstract Student-driven approaches have generated positive results in student development. This study reports a Students as Learning Experience Designers (Student-LED) Project as one example of employing student-driven approaches to develop learning abilities, leadership skills and reflective habits, in the context of the new senior secondary curriculum reform in Hong Kong. In such reform, schools are encouraged to offer other learning experiences (OLE) to facilitate students’ all-round development. This Student-LED project can be seen as pioneering in its cultural context and for the target participants. Students in Hong Kong were traditionally described as lacking independence, which seemed to contradict the premise of student-driven approaches. The present study as a pilot shows that Hong Kong secondary school students could potentially benefit from a student-driven approach. Sense of autonomy and positional leadership opportunities were found to be important factors to student learning. The concerns of students and teachers during the process were also identified through reflective statements. This study provided some insights into the use of student-driven approaches with Hong Kong learners.

Dynamic Characteristics of Tsing Ma Suspension Bridge

Numerical simulation was carried out to determine the dynamic properties of the Tsing Ma Suspension Bridge. Both the structure as a whole and individual subcomponents were modeled. Classical analytical solutions for simplified models from the available literature were compared with the results obtained from a finite-element code. Quantitative results for static deflection, natural frequencies, and mode shapes were compared with analytical solutions from linear theory. Out-of-plane modes were shown to be dominant. For in-plane antisymmetric and symmetric bending modes, in which the suspension cable and bridge deck vibrate in the same direction, the natural frequency of the main span of the bridge is determined to be approximately equal to the square root of the sum of the squares of the frequencies of the cable and bridge deck.

Service Leadership Community: A Seedbed of Nurturing Service Leadership Mindset in Student Learning

The service leadership mindset, unlike academic subjects, has proven difficult to “teach”. To seed this mindset of service leadership in students, The Hong Kong University of Science and Technology (HKUST) strategizes the creation of a cultural environment where students understand the need to serve, and more importantly, service occurs naturally – a Service Leadership Community (SLC). The Community provides various approaches for students to achieve three different levels of service leadership learning (i.e., Service Leaders, Service Leadership Practitioners, and Service Leadership Apprentices). To help students become service leaders, two types of courses are designed for them so that they can later take an active role as learning experience designers in service leadership. For the practitioner level of learning, a peer mentoring program and a service learning course are available to engage students with an interest in services and practicing service leadership. To serve as a scaffold for average students to have an apprentice level of learning about service leadership in their university life, a well-designed leadership corner located at the Engineering Commons has been set up to raise their awareness on service leadership. This three-level design of learning is intended to sustainably nurture the service leadership mindset in students. Several components of the SLC are evaluated and some recommendations are given to enhance the influence of SLC on student learning.

Why Is Service Leadership Important in Higher Education

Service leadership is a skill set with which people present a more active and proactive attitude towards study, work, and life. The development and application of service leadership is not restricted by disciplines, space, or time. It is a positive perception that people living in the modern society should possess in order to make them more competitive and serve others more effectively. This study examines the different definitions of service, leadership, servant leadership, service leadership, and service-learning and points out that people should possess service leadership skills no matter what their job is, where they live, or when they are requested to offer service, which strengthens the necessity and importance of service leadership training in higher education.