Wenshen Pong

Hands-on teaching of embedded systems design using FPGA-Based tPad development kit

Modern embedded systems design relies on heavy use of Intellectual Property (IP) and involves both hardware and software design. Moreover, three is an increasing unitization of a diverse set of I/O ports in embedded systems including video, audio, Ethernet, etc. In order to reflect these trends in education in a hands-on manner, a platform is needed that allows fast integration of hardware and software, rapid prototyping capability, and rich IP library covering processor cores, I/O interface standards, arithmetic and signal processing functions, etc. The t-pad development kit, by Terasic, which is based on the DE2-115 development board, designed around the Alteras Cyclone IV FPGA, provides a suitable platform for hands-on education of modern embedded systems design. We have developed a series of example-driven hands-on tutorials to guide students to a comprehensive embedded system design flow in a bottom-up fashion. These tutorials were developed and verified by summer interns from Cañada College who spent Summer 2011 at San Francisco State University. The tutorials are currently being used in an embedded systems design course at SFSU. A course project realizing a complex embedded system in teams of no more than four students is an integral part of this course. The results show that using this platform not only generates excitement and motivation in students, but also enhances their learning and teaches them skills of modern embedded systems design.

Heuristic design procedure for structures with displacement‐dependent damping devices

Purpose – The use of supplemental damping to dissipate energy is one of the most economical and effective ways to mitigate the effects of earthquake on structures. For practicing engineers, the ideal design procedure for buildings with supplemental damping should not be too complex to implement in practice. Building on the existing theoretical frame, the purpose of this paper is to develop simple and heuristic methods for the above design procedure.Design/methodology/approach – Passive displacement‐dependent devices are considered in this paper. Based on the theoretical results for added damping and added stiffness (ADAS) devices, the paper first analyzes the generated forces and the effects of ADAS devices on structures under seismic impact. We identify design parameters and variables are identified, and present the procedure of how the values of the variables (e.g. column shear force, ductility ratio) are finalized so that the design requirements can be met is presented. A four‐story six‐bay steel build...

Simulation methods for seismic behaviour of buildings in unbounded soil media with radiation damping

Mathematical and computer methods have been used by others to predict the seismic behaviour of viscous damped structures, yet most analyses have not accounted for the influence of an unbounded foundation. In order to better understand the motional behaviour of structures during earthquakes, this study considers the effects of radiation damping and flexibility when characterizing the interaction between damped structures and unbounded soil media. Two numerical methods, the consistent-infinitesimal finite element cell method and a new quiet boundary method, are introduced here. Also, computer simulation is used to demonstrate the effects of radiation damping for far field, unbounded media. The differences in seismic responses of structures with and without consideration of radiation damping are significant. The results also make clear the importance of accounting for such effects when, for example, structural engineers incorporate structural control devices into their designs.

Optimal selection of concrete anchors for connection cost reduction

A proprietary product such as a post‐installed concrete anchor has a unique place in the engineering community that includes product design, manufacturing, testing, evaluation and design for expected service conditions. An economic model in a non‐linear integer programming form is proposed for selection of concrete anchors in order to minimize connection cost. It is shown that the model can be easily incorporated with available computer software packages and generalized when different parameters and constraints are imposed to handle a variety of material selections. The information from recent testing conducted by CEL Consulting for a major engineering, procurement and construction (EPC) contractor is used to provide computational results. The method introduced here adds practical value to these types of industrial problems because it considers points of view from both structural engineers and project managers.

RADAS Device Technology for Retrofitting Damaged Structures in 921 Chi-Chi Earthquake

The 921 Chi-Chi earthquake was the most destructive earthquake for Taiwan in the twentieth century. The earthquake caused severe damage or collapse to residential and public structures. In addition to the use of traditional earthquake-resistant technologies for retrofitting damaged structures, new structural control technologies have been also adopted. The RADAS (Reinforced Added Damping and Stiffness) device is a new type of earthquake-proof technology. The RADAS device has been proved as a very reliable energy-absorbing device for seismic hazard mitigation through shaking table tests. In this paper, we will present the application of RADAS devices to damaged structures in the 921 Chi-Chi earthquake. It is also illustrated in this study that new structures equipped with RADAS Devices can enhance seismic resistibility, even if earthquakes exceed ML 7.3 magnitude on the Richter scale. Therefore, it is a sensible choice to use RADAS devices to retrofit damaged structures and to enhance the earthquake-resistant capacity of new structures.Copyright

The cost of seismic structural damage and preventive action

Purpose – This paper first aims to estimate the economic loss due to an earthquake, such as building‐related losses, the damage of debris generation and fire, and the social impact. Then, it seeks to evaluate the feasibility of retrofit to prevent buildings from seismic structural damages.Design/methodology/approach – The HAZUS software is used for the seismic loss estimation using default demographic data, which were obtained from San Francisco Assessor record. The HAZUS estimates the damage using the earthquake of 6.7 magnitude. Based on the HAZUS report incorporated with probabilistic scenarios of earthquakes, Federal Emergency Management Agency (FEMA) guidelines are used to calculate the cost of structural rehabilitation in San Francisco.Findings – It is recommended that either Options 1 and 3 or Options 2 and 3 provided by FEMA 156 and 157 respectively should be used to calculate the cost of seismic rehabilitation of a structure. The results provide estimated costs of retrofit plans for different typ...

Design Implications of Structural Irregularity

Irregular building designs present special problems to the structural engineer due to their uneven distributions of mass, stiffness, and strength. Because of these factors, irregular structures may have significantly different dynamic performance than a regular structure, which can lead to unanticipated force concentrations, deflections, and subsequent stresses on building members. Irregular building designs, while often more visually and architecturally interesting, are significantly more challenging to engineer for seismic loads. Discontinuities and irregularities in mass, configuration, and form can create many unwanted and unexpected effects when a structure is subjected to seismic forces. The Uniform Building Code (UBC) 1997 edition has addressed this concern by requiring dynamic analysis of irregular building designs greater than five stories in areas with greater seismic activity (seismic zones 3 and 4). The UBC’s requirement of a dynamic lateral force analysis, along with the requirement of a higher base shear force for irregular building designs (regular buildings are given a 10% base shear reduction bonus when dynamic analysis is performed), has made irregular building designs unattractive to structural engineers. Some structural engineers may question whether the UBC provisions are unnecessarily punitive to irregular building analysis, particularly for smaller buildings. To test this hypothesis, this study compares the results of using much simpler static seismic loading analysis with the results obtained from a dynamic analysis on two steel-frame six-story irregular building designs. The first building is irregular due to a type 3 vertical geometric irregularity (specifically a 3-story tower asymmetrically located above the remaining 3 stories). The second building is irregular due to a plan structural irregularity (a large central courtyard which creates diaphragm discontinuities in the top three stories). Both buildings are considered to be located in seismic zone 4, with a forcing input based on the 1997 UBC figure 16-3 used for the dynamic analysis. This study aims to present the design implications of structural irregularity. It seeks to investigate the differences in the calculated seismic forces, deflections, and stresses due to the two different methods of analysis.Copyright

Delay Estimation for Reliability Interpretation of Real-Time Hybrid Simulation Involving Viscous Dampers Towards Seismic Hazard Mitigation

Laboratory experiments play a critical role in earthquake engineering research for seismic safety evaluation of civil engineering structures. Servo-hydraulic actuators play a vital role to maintain the compatibility on boundaries between the analytical and experimental substructures in a real-time hybrid simulation. Previous study has indicated that actuator delay could significantly affect the accuracy of real-time hybrid simulation involving viscous dampers. Identifying the amount of actuator delay therefore is critical for reliability assessment of experimental results to properly interpret the performance of viscous dampers for seismic hazard mitigation. In this study a frequency domain based approach is applied for real-time hybrid simulation of viscous dampers with the presence of actuator delay. Computational simulations are conducted to assess the accuracy of the approach for estimating the delay when the substructures develop nonlinear behavior for reliability interpretation of real-time hybrid simulation.Copyright

Real-Time Hybrid Simulation of Viscous Dampers for Seismic Hazard Mitigation

Laboratory experiments play a critical role in earthquake engineering research for seismic safety evaluation of civil engineering structures. Real-time hybrid simulation provides a viable alternative for shake table testing to evaluate seismic performances of structures with rate-dependent seismic devices. Servo-hydraulic actuators play a vital role in a real-time hybrid simulation to maintain the boundary condition between the analytical and experimental substructures. Compensation of actuator delay is critical to minimize synchronization error from actuator delay and to achieve a successful real-time hybrid simulation. Research on how actuator delay can affect the real-time hybrid simulation involving viscous fluid damper is presented in this study. It is demonstrated that although the viscous fluid damper can help stabilize the real-time hybrid simulation with actuator delay, the experimental results need to be interpreted appropriately to evaluate the performance of viscous fluid damper for seismic hazard mitigation.© 2014 ASME

Engaging undergraduate students in nano-scale circuit research using summer internship

Semiconductor technology has been scaling at a steady pace following Moores law. The current generations of the technology have reached dimensions well below 100nm where nano-scale phenomena are prominent. Transistors in such a small scale behave very differently than the classic long channel devices taught in most undergraduate level textbooks. Moreover, there are new challenges in nano-scale circuit design, such as process variations and reliability issues that are not taught in undergraduate level courses. Working on latest technology issues is typically an opportunity available only to graduate level students working on related research projects. To address this gap, using a NASA Curriculum Improvements Partnership Award for the Integration of Research (CIPAIR) grant, we have created a summer internship program that engages community college students in research projects on the latest challenges of circuit design in nano-scale semiconductor technology. Through this program, four community college students were mentored by two graduate students in a research project to analyze performance degradation of integrated circuits due to transistor aging effects in nano-scale. In this research, analysis of transistor breakdown was performed through computer simulations to understand effects on circuit power and performance. A ring oscillator circuit was utilized as a generic logic circuit for this research. The breakdown was modeled by resistors placed between the transistor terminals. The value of the resistor represents the severity of the breakdown; large resistors represent fresh transistors, whereas low resistors represent a fully broken transistor. In addition to computer simulations, real ICs were studied by taking power measurements experimentally. This research aims to offer better insight into the impact of transistor breakdown and to improve IC design in nano-scale. Through this internship program, the undergraduate students not only contributed to research and discovery, but also gained valuable experience and knowledge of nano-scale circuits that could have not been achieved in traditional educational methods.