Research Grant for Outstanding Researchers

This paper summarizes the author’s experiences of developing various impact testing equipment and equipment for complex loading for structural research. The equipment include large diameter split Hopkinson pressure bars (SHPB), large-scale drop-weight testing equipment, field-test facility of truck collisions and multi-axes loading equipment. Several forms of building and bridge columns were tested under axial or lateral impact loads, simulating vehicular impact actions, sudden collapse and blasts. For vehicular impact action, a procedure of establishing simulative vehicular frame is proposed, making the vehicular loading tests much easier. Fundamental tests on concrete cylinders and confined concrete cylinders under high-strain rate impacts were also carried using a large-diameter split Hopkinson pressure bar (SHPB) equipment. Large to full-scale reinforced concrete or steel structures were also studied experimentally, using the developed equipment.

Author Bio
Dr. Xiao is a Changjiang/Qianren Distinguished Professor and serves as the Program Director for Energy, Environment and Infrastructure Sciences, in the Zhejiang University – University of Illinois at Urbana Champaign Institute (ZJUI). Dr. Xiao received his Bachelor of Engineering degree from the Tianjin University, China, in 1982, his Master and Doctor of Engineering degrees from the Kyushu University, Japan, in 1986 and 1989, respectively. Prof. Xiao’s professional and academic experiences include research engineer at the Aoki Corporation, Tokyo, Japan, Post-doc, lecturer and assistant research scientist at University of California, San Diego, tenure-track and tenured professor at the University of Southern California. He was a tenured full professor until 2011, and currently is a research Professor in the Sonny Astani Department of Civil and Environmental Engineering, University of Southern California. He was previously the Dean of the Civil Engineering College at the Nanjing Tech University, and the Hunan University. He serves as the associate editors for the American Society of Civil Engineers (ASCE) Journal of Structural Engineering, Journal of Bridge Engineering, and editorial board member of the Journal of Constructional Steel Research. He is an elected fellow of the American Society of Civil Engineers (ASCE) and American Concrete Institute (ACI). He is a registered Professional Engineer in California.

Prof. Xiao is an expert in structural engineering with overall goal towards sustainable development, and has made well known contributions in areas related to confined concrete, hybrid and composite structures, applications of advanced composites, retrofit/repair of structures, impact effects, and large-scale experimentation, etc. His recent research and industrial development efforts are focused on developing modern bamboo structures for buildings and bridges with the goal of promoting environmentally and eco-friendly construction

The corrosion of steel reinforcing bars and tendons in concrete is a principal cause of the observed degradation in the built environment and represents an important contributing factor for estimating and prolonging structural service life. Methods that detect or somehow characterize corrosion processes without damaging the material (NDT) and minimizing disruption to service are therefore important tools in the effort to sustain the concrete infrastructure. NDT methods based on electrochemical measurements, such as corrosion potentials and currents, have long been used to monitor corrosion processes. More recently however other NDT methods, based on a wide range of phenomena, have been studied and applied to characterize corrosion in concrete. In this paper, a brief historical review of electrochemical monitoring methods is presented, followed by a review and evaluation of recent research developments. The evaluated methods are organized by phenomenological bases and type of measured data, distinguishing between methods where the corrosion process itself is measured and those that measure the secondary effects and environments associated with corrosion processes. Methods based on electromagnetics, electric/magnetic fields, mechanical waves, and optics are considered here, but traditional chemical sampling methods are not. The review reveals that emerging NDT methods provide new information about corroding reinforced concrete structures; however more research development is needed to establish the ability to reliably and accurately assess the state of past and current corrosion in reinforced concrete structures.

Author Bio
Dr. John S. Popovics holds B.S. and M.S. degrees (Drexel University 1988 and 1990, respectively) in civil engineering, and a Ph.D. (The Pennsylvania State University 1994) in engineering science and mechanics. He has been on the faculty of the department of Civil and Environmental Engineering at the University of Illinois since January 2002. He has also held the positions of Research Assistant Professor at Northwestern University, Assistant Professor at Drexel University, Guest Scientist at the German Federal Materials Research Institute (BAM-Berlin), Visiting Professor at the Polytechnic University of Valencia in Spain and Visiting Researcher, Laboratoire Centrale des Pont et Chaussées (LCPC) in France.

Dr. Popovics is a member of the Acoustical Society of America, the American Society of Civil Engineers, the American Academy of Mechanics, and he is a named Fellow of the American Concrete Institute and the American Society for Nondestructive Testing. He participates as a voting member in five technical committees and currently serves as chair in two committees in these societies. He serves as associate editor of the Journal of Nondestructive Testing. He is affiliated with the Center for Advanced Cement-Based Materials (ACBM). Dr. Popovics was the recipient of the National Science Foundation’s CAREER award (1999), the American Society of Nondestructive Testing Fellowship Award 2012 and several teaching and advising awards from the University of Illinois.

A key point for cultural heritage protection in many modern cities is to prevent damaging of historical monuments from urbanization disturbances, such as road and subway traffic vibrations. A typical dilemma is whether to focus on the effects of short-term vibrations due to construction activities or on the consequences of long-term traffic-induced vibrations. Both cases present practical difficulties in both monitoring and data analysis procedures. Besides, specific standards do not provide indications neither on how to extract meaningful features from data, nor on how to identify proper strategic decisions for an effective maintenance of monuments.

In this paper, an example of state-of-the-art monitoring system is presented with its application to the continuous trigger-free dynamic monitoring of the Flavian Amphitheater, widely known as the Colosseum, in Rome, Italy. The installation of the monitoring system, composed of wireless accelerometers located on the top portion of the North façade of the Monument, has allowed to study all the features of recorded vibrations, beyond the usually considered peaks. The system architecture, the wireless protocol and the processing of the data are described in detail in this paper. A discussion on the data collected during a full year of monitoring is presented, with focus on statistical representations of the dynamic response, such as fractiles of the peak accelerations, which are meaningful and synthetic indicators of the effects induced on the Monument by external actions of both natural and man-made nature.

Author Bio
Giorgio Monti was born in Roma, Italy, in 1961. He has graduated in Civil Engineering in 1986 at the University of Roma La Sapienza, then he has obtained a Master of Science at the University of California at Berkeley in 1993, and a PhD at the University of Roma La Sapienza in 1994 in Structural Engineering.

Since 2001 he has been Full Professor at the Sapienza University of Roma and visiting professor at the University of California at Davis, USA, and at the Hunan University and the Technical University of Nanjing, China. At Sapienza University he is the Director of the Master Course on “Advanced Structural Design according to Eurocodes”.

He is currently Associate Editor of the ASCE Journal of Structural Engineering.

He is Expert Member of the Ministry of Infrastructures and Transportations of Italy and serves in several EU pre-normative Committees. Since 2005 he has been National Coordinator of a Civil Protection program in Italy on “Assessment and Risk Reduction of Reinforced Concrete Buildings”.

His scientific activity addresses the topics of: modeling and analysis of reinforced concrete structures under seismic excitation, risk assessment of existing structures in reinforced concrete and masonry, reliability analysis of structures and infrastructures in seismic zones and code calibration, use of sustainable materials and dry prefabrication in constructions, strategies for seismic protection of buildings, including base isolation, strategies for the preservation of cultural heritage, advanced solutions and techniques for structural strengthening.

In these fields, he has so far produced more than 320 publications, of which more than 70 in peer-reviewed international journals, and 6 books.

Concrete maintains the steel passivated unless a chloride proportion above the threshold or the carbonation front reach rebar position. When corrosion develops, several key aspects of the composite bar-concrete composite action are affected which compromises the structural stability and safety. The relative premature failure by steel corrosion of structures has increased the interest to incorporate to the standards for the calculation of the time to corrosion. These models in general identify the end of service life with the starting of bar corrosion, either by chlorides or by carbonation. Additionally, from the publications of the project Duracrete, funded by the EU, probabilistic treatments have been applied to steel depasivation which is associated to a serviceability limit state, SLS. Thus, fib Model Code (MC2010) recommends a probability of failure of 10% for the calculation of the time to corrosion. However, this recommendation leads to incoherences because, on one hand, the chloride threshold is not a fixed value and the carbonation front affects first to the external face of the bar developing a progressive perimetral damage and, on the other hand, the consideration of the limit state as a SLS, with so low fixed failure probability, introduces some degree of contradiction with the classical definition of the SLS. This is because, while the SLS is defined as the not fulfilling of the design prescriptions, any structural design performance changes just at the moment of steel depassivation. Additionally, no treatment on how to consider the damaged section or corrosion propagation model is usually given in the MC2010 or other standard and then, how to verify the classical SLS and ULS is undefined. Present work introduces new perspectives from a probabilistic point of view on the subject by, 1) first treating statistically the depassivation step, 2) second by introducing a corrosion propagation model and quantifying the corrosion limit states and 3) by the calculation of the depassivation probability which results dependent on the rate of the deterioration process itself. The whole exercise stresses the need to not consider a fixed value (10%) associated to a SLS the probability of corrosion, but to consider it a limit state of “corrosion initiation” following ISO 2394. The value of the adequate probability of corrosion would be dependent on the consequences of the failure and on the rates of chloride ingress, of carbonation or of steel corrosion. Associating a steel corrosion rate to the chloride diffusion coefficient or the carbonation ingress, the probability of depassivation can be calculated for a limit state of cover cracking of around 0.3 mm of crack width (corresponding to a bar diameter loss of 100 mm).

Author Bio
C. Andrade is Research Professor of the CSIC at the institute of Construction sciences “Eduardo Torroja”. Her “h” Index is 41. She has received several international awards in recognition of her research and training work (R. N. Whitney Prize 2013 by NACE and Robert L’Hermite Medal 1987 to young scientists from RILEM and “Manuel Rocha” of the Presidency of Portugal” among other).
She was appointed in 2003 Doctor Honoris Causa by the University of Trondheim, Norway, in 2006 from the University of Alicante. She is the author of about 300 papers in journals indexed and 160 in national magazines. She has presented over 250 communications to national conferences and more than 650 International.

She has published over 150 book chapters and has awarded several national and international patents and registered trademarks. She is co-author of 14 patents having 5 in exploitation and has participated in around 250 industrial contracts. In 2013 she promoted with other partners a start-up called “safety and Durability Engineering”. She was Principal Investigator of the Project Consolider-SEDUREC (Safety and Durability of Structures) in collaboration with the Polytechnic University of Madrid and the Center for Numerical Methods (CIMNE) of Barcelona approved within the Ingenio-2010 Spanish Research Program. Also has organized courses and seminars and lectured in Spain and several foreign countries, among which can be mentioned the Chair SEDUREC with 8 editions in South America.

She was Director of the Institute of Construction Sciences Eduardo Torroja (CSIC) for the periods 1985-1988 and 1993-2003; has participated in Standarization Committees at national, European and International level and has been President of several international organizations related to her specialty (UEAtc, RILEM, WFTAO and Liaison Committee which brings together the Associations: CIB, FIB, IABSE, IASS, RILEM and ECCE). She has also been Vice-chairman of the Promotion Area for the Industrial Development of the Iberoamerican Program CYTED. In the field of training she has supervised 31 doctoral theses and supervises another 10 that are in progress and about 31 Masters (or equivalent) Degrees.

She is Honour Director of “Advanced Courses of IETcc” organized annually by her Institute and is Coordinator of the official Master SEDUREC of CSIC-UIMP (International University Menendez Pelayo) approved by the ANECA (Agency of University Evaluation and Accreditation) of Spain. She is a member of several editorial boards of journals included in the SCI. She was member two years of the Jury of the Price “Principe de Asturias” on Science and Technology. From 2006-2008 she was Director General of Technological Policy at the Ministry of Education and Science of Spain. From 2008-2012 she was Adviser to the Secretary of State for Universities, Secretary of State for Research and to the Secretary General for Universities.

The critical deterioration of civil infrastructure has driven the search for new methods of rehabilitation and repair by incorporating sensors and developing remote systems that would allow monitoring and diagnosis of possible problems occurring. It is envisaged that structures will eventually be able to monitor themselves and inform owners of their state. These smart structures have unusual abilities: they can sense a change in temperature, pressure, or strain; diagnose a problem; and initiate an appropriate action in order to preserve structural integrity and continue to perform their intended functions. Sensors measure the state of the actual ambient conditions. If the sensor signals differ from the nominal conditions, the rehabilitation action can be taken. The application of smart structures for buildings is a rapidly growing area of research. There are a number of benefits to smart structural technologies; the most obvious one is the increased safety levels they can provide to cope with adjacent new constructions and with natural disasters such as climate change, flood warnings and earthquakes. Furthermore, these technologies will also be able to reduce costs associated with end-of-life structures. However, in order to exploit this technology, there is a need to know how load develops, how it is distributed and what factors need to be understood in case of changes in the loading conditions.

There has been a rapid development in the area of smart structures over the last decade thanks to innovation in sensor/actuator design and fabrication, fiber optics, micro-electro-mechanical sensors (MEMS) and other electronic devices, signal processing and control, and wireless sensors and sensor networks. Structural integration of fiber optic sensing systems represents a new branch of engineering which involves the unique marriage of: fiber optics, optoelectronics and composite material science. Optical fiber sensors have a number of advantages over their electrical counterparts. The transmission of light down an optical fiber is an established technique in optical communications for carrying information and is the primary candidate for resident sensing systems. Fiber optic sensing techniques have been developed as part of aerospace research because of its use in monitoring aeronautical and space structures composed of advanced materials. This technology can be transferred to the field of civil engineering to provide new opportunities in sensing and smart structures.

Design limits are frequently based on strain developing in the structure. Although strain measurement is well established, current practice has until recently been restricted to measurement of point-wise strains by means of vibrating wire (VWSG) or metal foil strain gauges and more recently by fiber optics utilizing Fiber Bragg Grating (FBG) technology. When instrumenting building components such as columns or beams where the strain distribution is merely a function of the end conditions and applied loading, point sensors are suitable to define the complete strain profile. However, where structures interact with soil (e.g. underground infrastructure such as foundations, tunnels or pipelines) or indeed in the case of a soil structure (road or dam embankments), the state of the structure is not fully understood unless the complete in situ strain regime is known. In the context of monitoring strain in underground structures, capturing the continuous strain profile is often invaluable to pinpoint localized problem areas such as joint rotations, deformations and non-uniformly distributed soil-structure interaction loads. In this paper, cases that utilized distributed fiber optic sensing for monitoring the performance of underground structures are presented. The novel aspects of this technology lies in the fact that tens of kilometers of fiber can be sensed at once for continuous distributed strain measurement, providing relatively cheap but highly effective monitoring systems. The system utilizes standard low cost fiber optics and the strain resolution can go down to 2 micro strains. The distributed measurement nature of this technology clearly differentiates from the other discrete point-wise strain measurement technologies. The aim of this paper is to demonstrate the importance of distributed strain measurements to monitor the performance of underground structures. Using the distributed strain data, the performance of underground structures that require rehabilitation, repair and reuse is shown.

Author Bio
Kenichi Soga is Chancellor’s Professor at the University of California, Berkeley. He obtained his BEng and MEng from Kyoto University in Japan and PhD from the University of California at Berkeley. He was Professor of Civil Engineering at the University of Cambridge before joining UC Berkeley in 2016. He has published more than 350 journal and conference papers and is co-author of “Fundamentals of Soil Behavior, 3rd edition” with Professor James K Mitchell.

His current research activities are Infrastructure sensing, Performance based design and maintenance of underground structures, Energy geotechnics, and Geotechnics from micro to macro. He is a founding member of the Cambridge Centre for Smart Infrastructure and Construction (CSIC) at the University of Cambridge and led the sensor and data analysis group. He is a Fellow of the UK Royal Academy of Engineering and a Fellow of the Institution of Civil Engineers. He is recipient of awards including George Stephenson Medal and Telford Gold Medal from the Institution of Civil Engineers and Walter L. Huber Civil Engineering Research Prize from the American Society of Civil Engineers.

Lateral-force resistance for low-rise buildings is often provided by structural masonry shear walls which may serve a dual function as an enclosure of stair and elevator shafts, and/or satisfy architectural needs to provide a building envelope. Because of the relatively large area of masonry walls relative to the floor area, such walls are commonly much stiffer than needed to meet serviceability constraints. This can be undesirable with respect to the attraction of lateral seismic forces since the natural period of vibration of the building system will be relatively short, resulting in high seismic accelerations. Because of this, seismic demand forces can be unnecessarily large relative to lateral-force capacity of shear walls, and damage may be likely in the event of a moderate or strong earthquake motion.

A novel structural engineering design approach is described in this paper where flexibility can be added to a masonry shear wall system with the use of a series of steel connector plates that transfer seismic story shear forces to individual masonry wall panels. This innovative form of building construction is termed “hybrid masonry” since structural steel frames resist gravity and lateral forces with engineered structural masonry panels. The steel connector plates are undersized to have considerable flexibility and a relatively low flexural strength. Acting as fuses, these connectors will not only reduce the overall lateral stiffness of a building system, but also dissipate seismic energy through hysteresis. In so doing, the integrity of the structural system to withstand earthquake motions is enhanced. As well, repair costs will be minimized since masonry damage can be circumvented. Replacement of fuse connectors represents a small cost in terms of materials, labor and interruption of building function. Thus, maintenance issues associated with costly seismic repairs can be avoided.

Results of computations will be given that show how lateral flexibility and seismic demand forces can be reduced. A simple two-story, one-bay steel frame with reinforced masonry panels will be used as an example to demonstrate load sharing between the frame and panels when connector strength and stiffness is varied. This test-bed structure has the same configuration as a series of large-scale test structures that were tested at the MUST-SIM facility at the University of Illinois at Urbana-Champaign. Computational models will be calibrated with measured results from large-scale experiments, and then used to examine sensitivities of seismic design parameters to various combinations of connector plate and steel frame stiffnesses.

The paper will highlight the need for adding flexibility to otherwise stiff masonry shear wall structures by making reference to the recent earthquake in Italy (August 2016) where numerous stiff, but weak, masonry buildings were severely damaged. The need to enhance deformation capacity of such structures will be emphasized as well as the overall design objective to reduce the potential for demolition following a destructive earthquake. In general, the paper will promote new innovations in structural design where structural steel and structural masonry are paired to result in a new standard of structural integrity that exceeds the sum of the parts. 

Author Bio
Daniel P. Abrams is Donald Biggar Willett Professor at the University of Illinois at Urbana-Champaign. He holds a B.S. (Illinois Institute of Technology 1970), a M.S. (University of Illinois at Urbana-Champaign 1974), and a Ph.D. (University of Illinois at Urbana-Champaign 1979), all in civil engineering. He has been on the faculty of the department of Civil and Environmental Engineering at the University of Illinois at Urbana Champaign since 1985.
He is a licensed professional engineer, has worked as a practicing structural engineer in Chicago and San Francisco, and continues to take part in consulting assignments with industry.  Dr. Abrams teaches graduate and undergraduate courses in structural engineering.  He has written over 180 papers or reports on seismic response of concrete or masonry buildings.  He was responsible for writing the masonry chapter of the NEHRP Guidelines for Seismic Rehabilitation of Buildings (FEMA 273/356), and has chaired the Building Seismic Safety Council’s Technical Subcommittee 5 on Masonry Structures.

He is also a past chair of the EERI Experimental Research Committee and the TMS Research Committee, and currently serves on TMS.  He is a former President of The Masonry Society (TMS), recipient of the TMS Scalzi and Presidents Awards, an Honorary Member of TMS, and a Fellow of TMS, ACI and SEI.