Propuesta de diseño para estimar el diagrama axil-momento de pilares de hormigón armado reforzados con angulares y presillas metálicos

De las diferentes técnicas existentes en refuerzo de pilares de hormigón armado, el uso de angulares y presillas metálicas, ha sido y sigue siendo, una de las técnicas más utilizadas. Sin embargo, todavía a día de hoy no existe una metodología totalmente aceptada sobre cómo debe diseñarse y comprobarse un refuerzo empleando esta técnica. En este artículo se presenta una nueva propuesta de diseño que permite obtener, de forma simple y rápida, el diagrama axil-momento de un pilar de hormigón armado reforzado con angulares y presillas. Esta nueva propuesta se basa en la aproximación del mencionado diagrama mediante una parábola dada por 3 puntos. Con ello se logra un considerable grado de ajuste con el comportamiento real exhibido por un pilar reforzado, lo que unido a su sencillez, convierten a la nueva propuesta de diseño en una opción recomendable para profesionales del sector que necesiten calcular el refuerzo de un pilar de hormigón armado con angulares y presillas.Ministerio de Educación y Ciencia de España Generalitat Valencian

Temperature effects on load transmission between slabs and shores

This paper analyses the influence of temperature changes on load transmission between floor slabs and shores during the in situ casting of concrete slabs by the shoring-clearing-striking method. Therefore several experimental studies were carried out which measured both the internal temperature evolution of the slabs and the loads on the shores. With the results of these studies, a Finite Element Model (FEM) of an experimental structure was then developed. In both the FEM and the experimental studies the same behaviour was observed regarding changes in temperature. When temperatures rose, the loads on shores decreased, accompanied by a reduction in slab deflection. When temperatures dropped, the loads on the shores increased, accompanied by an increased slab deflection. In the experimental study, for a temperature increment of ±1°C the load per surface unit on shores varied between 0.13kN/m 2 and 0.34kN/m 2, which represents between 2% and 6% of the self-weight of the slabs. The main cause of these load variations appears to be the temperature gradient inside the floor slabs.The authors would like express their gratitude to the Spanish Ministry for Science and Technology for funding the project (BIA2004-02085) and also to the Encofrados J. Alsina formwork company for their invaluable assistance.Gasch, I.; Alvarado Vargas, YA.; Calderón García, PA. (2012). Temperature effects on load transmission between slabs and shores. Engineering Structures. 39:89-102. https://doi.org/10.1016/j.engstruct.2012.02.004S891023

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. Journal of Structural Engineering, 142(1), 04015094. doi:10.1061/(asce)st.1943-541x.000136

Metaheuristic approaches for optimal broadcasting design in metropolitan MANETs

11th International Conference on Computer Aided Systems Theory. Las Palmas de Gran Canaria, Spain, February 12-16, 2007Mobile Ad-hoc Networks (MANETs) are composed of a set of communicating devices which are able to spontaneously interconnect without any pre-existing infrastructure. In such scenario, broadcasting becomes an operation of tremendous importance for the own existence and operation of the network. Optimizing a broadcasting strategy in MANETs is a multiobjective problem accounting for three goals: reaching as many stations as possible, minimizing the network utilization, and reducing the duration of the operation itself. This research, which has been developed within the OPLINK project (http://oplink.lcc.uma.es), faces a wide study about this problem in metropolitan MANETs with up to seven different advanced multiobjective metaheuristics. They all compute Pareto fronts of solutions which empower a human designer with the ability of choosing the preferred configuration for the network. The quality of these fronts is evaluated by using the hypervolume metric. The obtained results show that the SPEA2 algorithm is the most accurate metaheuristic for solving the broadcasting problem.Publicad

Improving SIEM for critical SCADA water infrastructures using machine learning

Network Control Systems (NAC) have been used in many industrial processes. They aim to reduce the human factor burden and efficiently handle the complex process and communication of those systems. Supervisory control and data acquisition (SCADA) systems are used in industrial, infrastructure and facility processes (e.g. manufacturing, fabrication, oil and water pipelines, building ventilation, etc.) Like other Internet of Things (IoT) implementations, SCADA systems are vulnerable to cyber-attacks, therefore, a robust anomaly detection is a major requirement. However, having an accurate anomaly detection system is not an easy task, due to the difficulty to differentiate between cyber-attacks and system internal failures (e.g. hardware failures). In this paper, we present a model that detects anomaly events in a water system controlled by SCADA. Six Machine Learning techniques have been used in building and evaluating the model. The model classifies different anomaly events including hardware failures (e.g. sensor failures), sabotage and cyber-attacks (e.g. DoS and Spoofing). Unlike other detection systems, our proposed work helps in accelerating the mitigation process by notifying the operator with additional information when an anomaly occurs. This additional information includes the probability and confidence level of event(s) occurring. The model is trained and tested using a real-world dataset

Evaluation of new regenerated fiber Bragg grating high-temperature sensors in an ISO 834 fire test

[EN] Temperature, one of the most important parameters in building fires, is now mostly measured with high-temperature thermocouples, which have the typical drawbacks of electric sensors, such as their sensitivity to electrical and magnetic interference. Fiber optic sensors are an alternative to electric sensors and offer many advantages, although their use in fire engineering is somewhat limited at the present time. This paper presents a set of new fiber optic sensors for measuring high temperatures, based on Regenerated Fiber Bragg Gratings (RFBGs). The sensors were placed near the surface of two concrete specimens and then tested under ISO 834 fire curve conditions for one hour. We consider this an important step forward in the application of high-temperature fiber optic sensors in fire engineering, as the sensors were subjected to direct flames and temperature increments of the order of 200 degrees C/min, similar to those in a real fire. The RFBG sensors measured maximum gas temperatures of circa 970 degrees C, in good agreement with those provided by thermocouples in the same position. The gas temperature measurements of the FOSs were also compared with the adiabatic temperatures measured by plate thermometers and concrete specimens surface temperatures calculated with numerical heat transfer models. (C) 2014 Elsevier Ltd. All rights reserved.This work has been possible thanks to the financial support of the Spanish Ministry of Science and Innovation (Research Projects BIA 2011-27104 and TEC2011-29120-C05-05). Funding for this research was provided to Paula Rinaudo by the European Commission (Erasmus Mundus Project Action 2 ARCOIRIS).Rinaudo, P.; Torres Górriz, B.; Paya-Zaforteza, I.; Calderón García, PA.; Sales Maicas, S. (2015). Evaluation of new regenerated fiber Bragg grating high-temperature sensors in an ISO 834 fire test. Fire Safety Journal. 71:332-339. https://doi.org/10.1016/j.firesaf.2014.11.024S3323397