Learning from failures in an emblematic building in Valencia, Spain

[EN] On many occasions advances have been made in science and engineering thanks to the knowledge gained from failures. In the particular case of structural engineering, the study of actual failures makes it possible to advance and define new theories, concepts and designs. Some examples are the changes and improvements that appeared after some of the "classical" failures such as the Ronan Point building, Quebec Bridge, Murrah Federal Building, Tacoma Narrows Bridge and the World Trade Center. This paper describes a teaching method used with structural engineering students at the Universitat Politecnica de Valencia based on the study of cases of damage to buildings in Valencia, Spain. Due to its special characteristics, one of the buildings studied is the Principe Felipe Science Museum. Some of its main characteristics are: 1) it is one of Valencia's emblematic buildings, 2) its considerable dimensions required huge quantities of concrete, 3) it has a complex structure and an innovative architectural design, 4) the wide variation in the type of damage detected, which make it a particularly valuable teaching aid. The most important damage detected has been classified and described during the visits to the Principe Felipe Science Museum. The damage mechanisms are widely diverse and include: those due to the behaviour of the concrete itself (e.g. shrinkage and early age thermal cracking), those due to the presence of damp, those whose origin can be traced back to the construction phase, and others due to corroded reinforcement and to the loads acting on the structure. The paper has a double value since on one hand it describes a highly successful teaching aid for the training of experts in structural engineering, while on the other it classifies and describes the existing damage in one of the most important modern buildings in Spain and perhaps in Europe.Adam, JM.; Buitrago, M. (2018). Learning from failures in an emblematic building in Valencia, Spain. Engineering Failure Analysis. 92:418-429. doi:10.1016/j.engfailanal.2018.06.023S4184299

Effects of sudden failure of shoring elements in concrete building structures under construction

[EN] The most frequently used technique to construct reinforced concrete (RC) building structures is the shoring or propping of successive floors, in which the slabs are supported by the shores until the concrete acquires sufficient strength. A significant number of structural failures have been reported during construction in recent years leading in some cases to the progressive collapse of the whole structure. The collapse often starts with the local failure of a single element which could be due to errors in design or construction and/or due to accidental events. Although this is a well-recognized problem, studies on the effects of local failure in the shoring elements on the integrity of the shoring-structure system have not been carried out in the past. In this work advanced numerical finite element models were carried out of a three-storey RC building and its shoring system. Four scenarios of local failure were considered: sudden removal of a (1) shore, (2) joist and (3) complete shore line; and (4) incorrect selection of shores. The results indicated that the structure-shoring system was able to develop al- ternative load paths without dynamic amplification effects due to the large stiffness and redundancy of the system without compromising the integrity of the structure but leading to significant damage in the concrete slabs. Design recommendations are also given based on the results from this study, which pretend to be the first study to focus on the structural response and damage of a building structure under construction after the sudden failure of one or more shores.The authors would like to express their gratitude to the Spanish Ministry of Education, Culture and Sport for funding received under: (a) the FPU Program [FPU13/02466] and complementary funding received for a stay at the University of Surrey (UK), and (b) the Mobility Program (Salvador de Madariaga 2017) of the Promotion of Talent and Employability within the state's Research & Innovation Program 2013-2016 [PRX17/00302]. The authors would like to thank Dr. P. Olmati who developed the prelimiundernary FE model of the structure at the operational stage as part of a project sponsored by the EPSRC Impact Acceleration Account held by the University of Surrey (grant ref: EP/ K503939) linked with a previous project funded by the EPSRC (grant ref: EP/K008153/1).Buitrago, M.; Sagaseta, J.; Adam, JM. (2018). Effects of sudden failure of shoring elements in concrete building structures under construction. Engineering Structures. 172:508-522. https://doi.org/10.1016/j.engstruct.2018.06.052S50852217

Protein interface classification by evolutionary analysis

Background Distinguishing biologically relevant interfaces from lattice contacts in protein crystals is a fundamental problem in structural biology. Despite efforts towards the computational prediction of interface character, many issues are still unresolved. Results We present here a protein-protein interface classifier that relies on evolutionary data to detect the biological character of interfaces. The classifier uses a simple geometric measure, number of core residues, and two evolutionary indicators based on the sequence entropy of homolog sequences. Both aim at detecting differential selection pressure between interface core and rim or rest of surface. The core residues, defined as fully buried residues (>95% burial), appear to be fundamental determinants of biological interfaces: their number is in itself a powerful discriminator of interface character and together with the evolutionary measures it is able to clearly distinguish evolved biological contacts from crystal ones. We demonstrate that this definition of core residues leads to distinctively better results than earlier definitions from the literature. The stringent selection and quality filtering of structural and sequence data was key to the success of the method. Most importantly we demonstrate that a more conservative selection of homolog sequences - with relatively high sequence identities to the query - is able to produce a clearer signal than previous attempts. Conclusions An evolutionary approach like the one presented here is key to the advancement of the field, which so far was missing an effective method exploiting the evolutionary character of protein interfaces. Its coverage and performance will only improve over time thanks to the incessant growth of sequence databases. Currently our method reaches an accuracy of 89% in classifying interfaces of the Ponstingl 2003 datasets and it lends itself to a variety of useful applications in structural biology and bioinformatics. We made the corresponding software implementation available to the community as an easy-to-use graphical web interface at http://www.eppic-web.org.ISSN:1471-210

Axially loaded RC columns repaired on one side with cement-based mortars

[EN] This paper describes and analyses the results of an experimental programme carried out at the Universitat Politecnica de Valencia on 18 reinforced concrete (RC) columns, 12 of which had been repaired on one side with cement-based mortar before being subjected to axial loading until failure. The objective of the research was to determine the performance of the columns that had been repaired using different mortars, evaluate the influence of Class R3 and R4 mortar used and of the application of a binder or bonding agent. The results obtained were compared with those of the undamaged control columns and those of the unrepaired damaged columns to obtain values for the efficiency of the repairs and for the improvement in the load-bearing capacity of the columns. The results obtained indicate that the columns repaired with Class R3 mortar, with a lower elasticity modulus, function in better way than the Class R4 repaired ones. The presence or absence of a binder was not found to be a determining factor in improving the behaviour of the repaired elements. The chief novelty of the study lies in the fact that it is the first experimental study on RC columns totally repaired on one side only, using different types of mortar with and without the application of a binder. (C) 2018 Elsevier Ltd. All rights reserved.The authors express their gratitude to HADES CONSTRUCCIONES Y CREACIONES 2003 for their material, human and financial support.Ortega, I.; Pellicer, TM.; Calderón García, PA.; Adam, JM. (2018). Axially loaded RC columns repaired on one side with cement-based mortars. Construction and Building Materials. 177:1-9. https://doi.org/10.1016/j.conbuildmat.2018.05.102S1917

Cement-based mortar patch repair of RC columns. Comparison with all-four-sides and one-side repair

[EN] This paper describes an experimental study on patch-repaired reinforced concrete columns subjected to axial loads until failure. The behaviour of four series of columns repaired with Class R3 and R4 cement-based mortar was analysed both with and without a bonding agent. The results obtained were compared with control series of undamaged and damaged but unrepaired columns to determine the effectiveness of the repairs and the subsequent improvement in the behaviour of the columns. The results of this study were compared with those of previous work by the authors on the analysis of all-four-side repairs and one-side repairs. The conclusion reached was that patch repairs are highly effective as compared to the other techniques studied and that using Class R3 mortar achieves better results on damaged columns made with low-quality concrete. It was also concluded that applying a bonding agent does not improve the results, although this element was found to be necessary to prevent the premature detachment of the repair when there is a substantial difference between the stiffness of the column concrete and that of the mortar used in the repairs. (C) 2018 Elsevier Ltd. All rights reserved.The authors wish to express their gratitude to the HADES CONSTRUCCIONES Y CREACIONES 2003 company for their human and material contributions to this work.Ortega, I.; Pellicer, TM.; Calderón García, PA.; Adam, JM. (2018). Cement-based mortar patch repair of RC columns. Comparison with all-four-sides and one-side repair. Construction and Building Materials. 186:338-350. https://doi.org/10.1016/j.conbuildmat.2018.07.148S33835018

An experimental study on RC columns repaired on all four sides with cementitious mortars

[EN] This paper describes a study carried out in the ICITECH laboratories (Universitat Politècnica de València) on RC columns repaired on all four sides with cementitious-based mortars. A total of 18 specimens were tested, representing a group of square 200 x 200 mm2 columns subjected to compressive axial loads. Different repair scenarios were considered in order to study the influence of the type of mortar used and the presence or absence of bonding agents between the mortar and the column concrete. The results obtained showed that bonding agents have no appreciable effect on the behaviour of the repaired columns. Of the two types of mortar used in the study (Classes R3 and R4), the columns repaired with the lower grade mortar (R3) were seen to behave better. The main novelty of this work lies in the fact that this is the first time that two types of mortar are compared in the repair of four column sides, in addition to the possible use of bonding agents between the mortar and the column.The authors are grateful to the HADES CONSTRUCCIONES Y CREACIONES 2003 company for their material and financial assistance, without which the study would not have been possible. They also wish to express their gratitude to Professor Jose L. Bonet, Dr. Javier Pereiro-Barcelo and Mr. Lino Martinez for their assistance in planning and performing the tests.Ortega, I.; Pellicer, TM.; Adam, JM.; Calderón García, PA. (2018). An experimental study on RC columns repaired on all four sides with cementitious mortars. Construction and Building Materials. 161:53-62. https://doi.org/10.1016/j.conbuildmat.2017.11.126S536216

Solvable self-dual impurity models

We find a family of (half) self-dual impurity models such that the self-dual (BPS) sector is exactly solvable, for any spatial distribution of the impurity, both in the topologically trivial case and for kink (or antikink) configurations. This allows us to derive the metric on the corresponding one-dimensional moduli space in an analytical form. Also the generalized translational symmetry is found in an exact form. This symmetry provides a motion on moduli space which transforms one BPS solution into another. Finally, we analyse exactly how vibrational properties (spectral modes) of the BPS solutions depend on the actual position on moduli space. These results are obtained both for the nontrivial topological sector (kinks or antikinks) as well as for the topologically trivial sector, where the motion on moduli space represents a kink-antikink annihilation process