Carmen Andrade, for the research proposal entitled: Reliability Analysis of Reinforcement Corrosion Limit State
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).
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.
Kenichi Soga, for the research proposal entitled: Distributed Fiber Optic Sensing for Monitoring Underground Structures
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.
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.
D.P. Abrams, for the research proposal entitled: Adding Flexibility to Stiff Masonry Shear Walls
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.
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.