Load limiters on shores: Design and experimental research

[EN] When constructing reinforced concrete building structures, shores are normally used to transmit the loads from freshly poured slabs to lower floors. However, certain problems are involved in this process, including: (a) the loads on the shores may be higher than expected, which can lead to the collapse of the shoring system or even of the whole structure, and (b) the limited range of shore types in commercial catalogues, which often means that the shores used are oversized. This paper describes the study carried out on the development of a new loadlimiter (LL) that can be fitted to shores to improve safety and reduce the cost of constructing building structures. The study shows that combining mechanical and civil engineering fields made it possible to produce a novel device that could revolutionise the shoring techniques at present in use. The method of designing and implementing the LLs involved: (a) the design of prototypes by using numerical simulations, (b) the use of the design of experiments technique, (c) an ambitious experimental campaign in which LL were tested, (d) the detailed simulation of the final design, and (e) the formulation of a simplified model that considers the behaviour of the shore-LL as a unit.The authors would like to express their gratitude to the Spanish Ministry of Education, Culture and Sport for funding received under the FPU Program [FPU13/02466], also to the Generalitat Valenciana [GV/2015/063] and to Professor Salvador Ivorra from University of Alicante for helping us to carry out the steel characterization tests.Buitrago, M.; Adam, JM.; Calderón García, PA.; Moragues, JJ. (2018). Load limiters on shores: Design and experimental research. Engineering Structures. 173:1029-1038. doi:10.1016/j.engstruct.2018.07.063S1029103817

Load transmission between slabs and shores during the construction of RC building structures A review

[EN] Shoring successive floors is at present the most frequently used technique when constructing reinforced concrete (RC) building structures. This technique allows the recently poured slabs to be supported by the lower slabs by means of shores. Considering the particular characteristics of shoring successive floors, it is very important to be able to estimate how loads are transmitted between shores and slabs in order to maintain adequate structural safety and avoid situations of risk or even collapse in buildings under construction. The transmission of loads from shores to slabs during all the construction stages is a complex phenomenon and has been the subject of numerous studies, especially in recent years. The research carried out to date has included experiments on fullscale buildings and the development of advanced numerical models, the estimation of the loads acting on slabs during construction, the definition of simplified calculation methods to estimate loads on slabs and shores during building construction and estimating the appropriate construction times taking into account the evolution of the mechanical properties of early-age concrete. This paper was conceived in order to give an answer to: (1) advances in the field of constructing RC building structures, (2) the growing interest of the scientific community, and (3) the need for the structural and construction engineering sector to have the tools available to increase the safety and design of building construction processes. The paper is unique in the field of RC building structures in that it is the widest, most complete and most ambitious review carried out to date and includes the most important advances in the study of slab-shore load transmissions. This work will be of interest to researchers who wish to go deeper into the field of building construction, and to more experienced professionals who require all the up-to-date information in a single document. However, engineers, architects and builders could also find the paper an excellent guide that will help them to improve their daily work in the field of designing and constructing buildings.The authors would like to express their gratitude to the Spanish Ministry of Education, Culture and Sport for funding received under the FPU Program [FPU13/02466] and also to the Generalitat Valenciana [GV/2015/063].Buitrago, M.; Adam, JM.; Moragues, JJ.; Calderón García, PA. (2018). Load transmission between slabs and shores during the construction of RC building structures A review. Engineering Structures. 173:951-959. https://doi.org/10.1016/j.engstruct.2018.07.04695195917

A full-scale timbrel cross vault subjected to vertical cyclical displacements in one of its supports

[EN] Up-and-down cyclical displacement of supports-foundations, due for example to the presence of expansive soils, can affect the integrity of a structure and may even lead to its collapse. A recent study carried out at the ICITECH laboratories of the Universitat Politècnica de València analysed the effects of earth settlements on the behaviour of masonry cross vaults. One of the tests involved the construction and testing of a full-scale timbrel cross vault, one of whose supports was subjected to up-and-down vertical displacement cycles. The 4×4 m2 vault was composed of four 3.6 m diameter arches supporting a masonry web. Vertical displacements were applied to one of the supports by means of two synchronised mechanical jacks. The results of the tests provide valuable information to the scientific community, architects and engineers on the behaviour of timbrel cross vaults when one of their supports is subjected to cyclical movements.The authors wish to express their gratitude to the Spanish Ministry of Economy, Industry and Competitiveness for the funding provided through Project BIA 2014-59036-R, and also to LIC-Levantina Ingenieria y Construction and the Grupo Puma for their invaluable assistance. The second author (Elisa Bertolesi) would like to thank the Universitat Politecnica de Valencia for funding received for her postdoctoral grant (PAID-10-17).Torres Górriz, B.; Bertolesi, E.; Calderón García, PA.; Moragues, JJ.; Adam, JM. (2019). A full-scale timbrel cross vault subjected to vertical cyclical displacements in one of its supports. Engineering Structures. 183:791-804. https://doi.org/10.1016/j.engstruct.2019.01.054S79180418

Load limiters on temporary shoring structures: Tests on a full-scale building structure under construction

[EN] Temporary shoring structures are used in the construction of reinforced concrete buildings to transmit the loads of newly poured slabs onto the lower floors. The main problems involved in the use of shores/props are: a) the possibility of having higher loads than those initially foreseen, and b) the structural efficiency and cost of the system, which is normally over-sized due to being designed to bear the maximum load of the most demanding building operation. This paper describes a test carried out on a full-scale one-story building to analyze the behaviour of load limiters (LLs) installed on shores under actual construction loading conditions. The theoretical approach and development of this new LL concept were described in previous papers. As these LLs still had not been tested in actual buildings, this paper covers the existing need for a test in the form of a "proof of concept". It also includes computer simulations and recommendations for the use of LLs.The authors would like to express their gratitude to the Spanish Ministry of Education, Culture and Sport for funding received under the FPU Program [FPU13/02466], to the Generalitat Valenciana [GV/2015/063] and also to the Levantina, Ingenieria y Construcción S.L. and Encofrados J. Alsina S.A. business companies for their invaluable cooperation.Buitrago, M.; Calderón García, PA.; Moragues, JJ.; Alvarado, YA.; Adam, JM. (2021). Load limiters on temporary shoring structures: Tests on a full-scale building structure under construction. Journal of Structural Engineering. 147(3):1-9. https://doi.org/10.1061/(ASCE)ST.1943-541X.0002948S191473Adam, J. M., Buitrago, M., Moragues, J. J., & Calderón, P. A. (2017). Limitations of Grundy and Kabaila’s Simplified Method and Its Repercussion on the Safety and Serviceability of Successively Shored Building Structures. Journal of Performance of Constructed Facilities, 31(5), 04017040. doi:10.1061/(asce)cf.1943-5509.0001038Adam, J. M., Parisi, F., Sagaseta, J., & Lu, X. (2018). Research and practice on progressive collapse and robustness of building structures in the 21st century. Engineering Structures, 173, 122-149. doi:10.1016/j.engstruct.2018.06.082Alvarado, Y. A., Calderón, P. A., Adam, J. M., Payá-Zaforteza, I. J., Pellicer, T. M., Pallarés, F. J., & Moragues, J. J. (2009). An experimental study into the evolution of loads on shores and slabs during construction of multistory buildings using partial striking. Engineering Structures, 31(9), 2132-2140. doi:10.1016/j.engstruct.2009.03.021Buitrago, M., Adam, J. M., Alvarado, Y. A., Calderón, P. A., & Gasch, I. (2016). Maximum loads on shores during the construction of buildings. Proceedings of the Institution of Civil Engineers - Structures and Buildings, 169(7), 538-545. doi:10.1680/jstbu.15.00089Buitrago, M., Adam, J. M., Alvarado, Y. A., Moragues, J. J., Gasch, I., & Calderón, P. A. (2016). Designing construction processes in buildings by heuristic optimization. Engineering Structures, 111, 1-10. doi:10.1016/j.engstruct.2015.12.009Buitrago, M., Adam, J. M., Calderón, P. A., & Moragues, J. J. (2018). Load limiters on shores: Design and experimental research. Engineering Structures, 173, 1029-1038. doi:10.1016/j.engstruct.2018.07.063Buitrago, M., Alvarado, Y. A., Adam, J. M., Calderón, P. A., Gasch, I., & Moragues, J. J. (2015). Improving construction processes of concrete building structures using load limiters on shores. Engineering Structures, 100, 104-115. doi:10.1016/j.engstruct.2015.06.007Buitrago, M., Moragues, J. J., Calderón, P. A., & Adam, J. M. (2018). Structural failures in cast-in-place reinforced concrete building structures under construction. Handbook of Materials Failure Analysis, 153-170. doi:10.1016/b978-0-08-101928-3.00008-2Buitrago, M., Sagaseta, J., & Adam, J. M. (2018). Effects of sudden failure of shoring elements in concrete building structures under construction. Engineering Structures, 172, 508-522. doi:10.1016/j.engstruct.2018.06.052Buitrago, M., Sagaseta, J., & Adam, J. M. (2020). Avoiding failures during building construction using structural fuses as load limiters on temporary shoring structures. Engineering Structures, 204, 109906. doi:10.1016/j.engstruct.2019.109906Calderón, P. A., Alvarado, Y. A., & Adam, J. M. (2011). A new simplified procedure to estimate loads on slabs and shoring during the construction of multistorey buildings. Engineering Structures, 33(5), 1565-1575. doi:10.1016/j.engstruct.2011.01.027Carper, K. L. (1987). Structural Failures During Construction. Journal of Performance of Constructed Facilities, 1(3), 132-144. doi:10.1061/(asce)0887-3828(1987)1:3(132)Ellirtgwood, B. (1987). Design and Construction Error Effects on Structural Reliability. Journal of Structural Engineering, 113(2), 409-422. doi:10.1061/(asce)0733-9445(1987)113:2(409)El-Tawil, S., Li, H., & Kunnath, S. (2014). Computational Simulation of Gravity-Induced Progressive Collapse of Steel-Frame Buildings: Current Trends and Future Research Needs. Journal of Structural Engineering, 140(8). doi:10.1061/(asce)st.1943-541x.0000897Epaarachchi, D. C., Stewart, M. G., & Rosowsky, D. V. (2002). Structural Reliability of Multistory Buildings during Construction. Journal of Structural Engineering, 128(2), 205-213. doi:10.1061/(asce)0733-9445(2002)128:2(205)Gasch, I., Alvarado, Y. A., Calderón, P. A., & Ivorra, S. (2014). Construction loads using a shoring–clearing–striking process. Proceedings of the Institution of Civil Engineers - Structures and Buildings, 167(4), 217-229. doi:10.1680/stbu.12.00006Ghali, A., & Gayed, R. B. (2014). Sustainable Serviceability of Structural Concrete: Control of Deflection and Cracking. Journal of Structural Engineering, 140(7), 04014042. doi:10.1061/(asce)st.1943-541x.0000965Hadipriono, F. C. (1985). Analysis of Events in Recent Structural Failures. Journal of Structural Engineering, 111(7), 1468-1481. doi:10.1061/(asce)0733-9445(1985)111:7(1468)Hadipriono, F. C., & Wang, H.-K. (1987). Causes of falsework collapses during construction. Structural Safety, 4(3), 179-195. doi:10.1016/0167-4730(87)90012-9Karshenas, S., & Ayoub, H. (1994). Analysis of Concrete Construction Live Loads on Newly Poured Slabs. Journal of Structural Engineering, 120(5), 1525-1542. doi:10.1061/(asce)0733-9445(1994)120:5(1525)Liu, X., Chen, W., & Bowman, M. D. (1985). Construction Load Analysis for Concrete Structures. Journal of Structural Engineering, 111(5), 1019-1036. doi:10.1061/(asce)0733-9445(1985)111:5(1019)Qian, K., & Li, B. (2013). Performance of Three-Dimensional Reinforced Concrete Beam-Column Substructures under Loss of a Corner Column Scenario. Journal of Structural Engineering, 139(4), 584-594. doi:10.1061/(asce)st.1943-541x.0000630Sasani, M., Kazemi, A., Sagiroglu, S., & Forest, S. (2011). Progressive Collapse Resistance of an Actual 11-Story Structure Subjected to Severe Initial Damage. Journal of Structural Engineering, 137(9), 893-902. doi:10.1061/(asce)st.1943-541x.0000418Sasani, M., & Sagiroglu, S. (2008). Progressive Collapse Resistance of Hotel San Diego. Journal of Structural Engineering, 134(3), 478-488. doi:10.1061/(asce)0733-9445(2008)134:3(478)Schellhammer, J., Delatte, N. J., & Bosela, P. A. (2013). Another Look at the Collapse of Skyline Plaza at Bailey’s Crossroads, Virginia. Journal of Performance of Constructed Facilities, 27(3), 354-361. doi:10.1061/(asce)cf.1943-5509.0000333Zhang, H., Reynolds, J., Rasmussen, K. J. R., & Ellingwood, B. R. (2016). Reliability-Based Load Requirements for Formwork Shores during Concrete Placement. 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Improving construction processes of concrete building structures using load limiters on shores

This paper analyses the redistribution of maximum loads using a system of load limiters on shores in which the limiters yield at a given load and thus reduce the maximum load absorbed by the shores. For this analysis a finite element modelling (FEM) of an experimental building was developed in which load limiters had been fitted to the shores to restrict their maximum load to a given value. This was designed to: (a) optimise slab construction costs by using shores of lower load-bearing capacities, (b) improve safety during the construction of consecutive concrete slab floors by reducing maximum loads and redistributing loads amongst the shores; and (c) increase structural efficiency by more efficient use of the materials employed due to load redistribution. It has been estimated that using load limiters in this way can reduce total shoring costs in a building project by between 30% and 40%.The authors would like to express their gratitude to the Universitat Politecnica de Valencia for funding this research project (PAID-06-11) and also to the Encofrados J. Alsina Company for their invaluable cooperation.Buitrago Moreno, M.; Alvarado Vargas, YA.; Adam Martínez, JM.; Calderón García, PA.; Gasch, I.; Moragues, JJ. (2015). Improving construction processes of concrete building structures using load limiters on shores. Engineering Structures. 100:104-115. doi:10.1016/j.engstruct.2015.06.007S10411510

Eduardo Torroja's Zarzuela Racecourse grandstand: Design, construction, evolution and critical assessment from the Structural Art perspective

The grandstands of La Zarzuela Racecourse in Madrid designed by the engineer E. Torroja and the architects C. Arniches and M. Dominguez are one of the world s most outstanding concrete constructions of the first half of the 20th century. This paper describes the design competition and the conceptual design process that led to their construction and carries out a critical assessment of the grandstands from the perspective of Structural Art. By doing so, the paper helps to develop the discipline of structural criticism, and points out lessons learned from their design and construction process which should not be forgotten at the present time, such as: (a) the importance of design competitions; (b) the fact that the pursuit of economy and efficiency can actually improve the quality and aesthetics of the design; (c) the importance of combining logical reasoning based on technical criteria with imagination to achieve excellence in structural design; and (d) the importance of estimating structural behavior by simple formulas and of learning from both existing structures and experimental models.The authors are very grateful to the engineers G. Ayuso and L. Fernandez Troyano from Carlos Fernandez Casado S.L. and C. Polo from the company Hipodromo de La Zarzuela S.A. for all the information and support provided. The authors also want to thank the Archivo Torroja and its former librarian, I. Garcia, for providing full access to the funds of the archive to develop this research. Funding for this research was provided by the Spanish Ministry for Science and Innovation (Research Project BIA 2011-27104).Moragues, JJ.; Paya-Zaforteza, I.; Medina, O.; Adam Martínez, JM. (2015). Eduardo Torroja's Zarzuela Racecourse grandstand: Design, construction, evolution and critical assessment from the Structural Art perspective. Engineering Structures. 105:186-196. https://doi.org/10.1016/j.engstruct.2015.10.008S18619610

Adiciones y correcciones a la orquidoflora valenciana, VII

Se aportan datos sobre algunos táxones de Orchidaceae que resultan escasos en la Comunidad Valenciana o en determinadas de sus comarcas; a destacar la presencia de Ophrys santonica y O. × pseudospeculum en Alicante.It is shown some data about rare taxa of Orchidaceae at the Valencian Community (E Spain) or expansions of area to new shires; to emphasize the presence of Ophrys santonica and O. × pseudospeculum in Alicante

Clinical factors associated with a Candida albicans Germ Tube Antibody positive test in Intensive Care Unit patients

Background: Poor outcomes of invasive candidiasis (IC) are associated with the difficulty in establishing the microbiological diagnosis at an early stage. New scores and laboratory tests have been developed in order to make an early therapeutic intervention in an attempt to reduce the high mortality associated with invasive fungal infections. Candida albicans IFA IgG has been recently commercialized for germ tube antibody detection (CAGTA). This test provides a rapid and simple diagnosis of IC (84.4% sensitivity and 94.7% specificity). The aim of this study is to identify the patients who could be benefited by the use of CAGTA test in critical care setting. Methods: A prospective, cohort, observational multicentre study was carried out in six medical/surgical Intensive care units (ICU) of tertiary-care Spanish hospitals. Candida albicans Germ Tube Antibody test was performed twice a week if predetermined risk factors were present, and serologically demonstrated candidiasis was considered if the testing serum dilution was >= 1: 160 in at least one sample and no other microbiological evidence of invasive candidiasis was found. Results: Fifty-three critically ill non-neutropenic patients (37.7% post surgery) were included. Twenty-two patients (41.5%) had CAGTA-positive results, none of them with positive blood culture for Candida. Neither corrected colonization index nor antifungal treatment had influence on CAGTA results. This finding could corroborate that the CAGTA may be an important biomarker to distinguish between colonization and infection in these patients. The presence of acute renal failure at the beginning of the study was more frequent in CAGTA-negative patients. Previous surgery was statistically more frequent in CAGTA-positive patients. Conclusions: This study identified previous surgery as the principal clinical factor associated with CAGTA-positive results and emphasises the utility of this promising technique, which was not influenced by high Candida colonization or antifungal treatment. Our results suggest that detection of CAGTA may be important for the diagnosis of invasive candidiasis in surgical patients admitted in ICU.This study has been supported by a Pfizer research gran

World checklist of hornworts and liverworts

A working checklist of accepted taxa worldwide is vital in achieving the goal of developing an online flora of all known plants by 2020 as part of the Global Strategy for Plant Conservation. We here present the first-ever worldwide checklist for liverworts (Marchantiophyta) and hornworts (Anthocerotophyta) that includes 7486 species in 398 genera representing 92 families from the two phyla. The checklist has far reaching implications and applications, including providing a valuable tool for taxonomists and systematists, analyzing phytogeographic and diversity patterns, aiding in the assessment of floristic and taxonomic knowledge, and identifying geographical gaps in our understanding of the global liverwort and hornwort flora. The checklist is derived from a working data set centralizing nomenclature, taxonomy and geography on a global scale. Prior to this effort a lack of centralization has been a major impediment for the study and analysis of species richness, conservation and systematic research at both regional and global scales. The success of this checklist, initiated in 2008, has been underpinned by its community approach involving taxonomic specialists working towards a consensus on taxonomy, nomenclature and distribution

Modified Wisconsin Card Sorting Test (M-WCST): Normative data for Spanish-speaking pediatric population

OBJECTIVE: To generate normative data for the Modified Wisconsin Card Sorting Test (M-WCST) in Spanish-speaking pediatric populations. METHOD: The sample consisted of 4,373 healthy children from nine countries in Latin America (Chile, Cuba, Ecuador, Guatemala, Honduras, Mexico, Paraguay, Peru, and Puerto Rico) and Spain. Each participant was administered the M-WCST as part of a larger neuropsychological battery. Number of categories, perseverative errors, and total error scores were normed using multiple linear regressions and standard deviations of residual values. Age, age2, sex, and mean level of parental education (MLPE) were included as predictors in the analyses. RESULTS: The final multiple linear regression models indicated main effects for age on all scores, such that the number of categories correct increased and total number of perseverative errors and total number of errors decrease linearly as a function of age. Age2 had a significant effect in Chile, Cuba, Ecuador, and Spain for numbers of categories; a significant effect for number of perseverative errors in Chile, Cuba, Mexico, and Spain; and a significant effect for number of total errors in Chile, Cuba, Peru, and Spain. Models showed an effect for MLPE in Cuba (total errors), Ecuador (categories and total errors), Mexico (all scores), Paraguay (perseverative errors and total error), and Spain (categories and total errors). Sex affected number of total errors for Ecuador. CONCLUSIONS: This is the largest Spanish-speaking pediatric normative study in the world, and it will allow neuropsychologists from these countries to have a more accurate way to interpret the M-WCST with pediatric populations