Applied Element Method (AEM)

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  • Earthquake Pounding Effect on Adjacent Reinforced Concrete Buildings

    Abstract: During earthquakes, pounding of adjacent buildings occurs due to their different dynamic characteristics as well as insufficient separation distance between them. Although earthquake loading is commonly considered in structural design, pounding of adjacent buildings is not usually considered and usually causes highly unexpected damages and failures. Pounding effect was numerically investigated in this study, where adjacent buildings were designed to resist lateral earthquake loads without taking into consideration the additional applied force resulting from pounding. Nonlinear dynamic analysis was carried using the Applied Element Method (AEM). Pounding of buildings of different structural systems, different gravity loading and different floor heights was investigated. Dynamic behavior in terms of additional base shear, base bending moments and pounding forces was investigated for different gap distances less than the safe gap distance specified by the Egyptian Code of Practice (ECP). Effect of gap distance, building's dynamic characteristics, building's height and gravity loads on additional straining actions due to impact was discussed.

    Keywords: Pounding  separation distance  applied element method.

    Mariam Ehab, Hamed Salem, Hatem Mostafa and Nabil Yehia. Article: Earthquake Pounding Effect on Adjacent Reinforced Concrete Buildings. International Journal of Computer Applications 106(9):27-34, November 2014. 
     

  • Improving the structural robustness of multistory steel-frame buildings

     Abstract: During Although there are numerous hazards that could trigger the progressive collapse of a building, there are limited provisions in related codes regarding the design of structures to withstand exposure to such threats. It is thus expedient to limit the extent of damage to prevent the initiation of progressive collapse. This could be done by usage of the alternate path method, whereby the structure is made to withstand the loss of one or more critical load-bearing elements and prevent disproportionate collapse. In our study, we investigated the resistance of seismically designed steel-frame buildings to progressive collapse, focusing on the contributions of the floor system and beam-to-column connections. The applied element method was used to predict the structural response by nonlinear static and dynamic analyses, with the purpose of determining some robustness criteria, using as reference the ratio of the failure load to the nominal gravity load.

    Keywords: Redundancy; steel structures; composite structures; damage; structural failures.

    Mariam Ehab, Florea Dinu, Dan Dubina & Ioan Marginean (2014): Improving the structural robustness of multistory steel-frame buildings, Structure and Infrastructure Engineering: Maintenance, Management, Life-Cycle Design and Performance, DOI: 10.1080/15732479.2014.927509. 

  • Structural Identification and Damage Characterization of a Masonry Infill Wall in a Full-Scale Building Subjected to Internal Blast Load

    Abstract: Structural identification continues to develop an expanding role within performance-based civil engineering by offering a means to construct high-fidelity analytical models of in-service structures calibrated to experimental field measurements. Although continued advances and case studies are needed to foster the transition of this technique from exploration to practice, potential applications are diverse and range from design validation, construction quality control, assessment of retrofit effectiveness, damage detection, and lifecycle assessment for long-term performance evaluation and structural health monitoring systems. Existing case studies have been primarily focused on large civil structures, specifically bridges, large buildings, and towers, and the limited studies exploring application to damaged structures have been primarily associated with seismic events or other conventional hazards. The current paper produces the first experimental application of structural identification to a component of a full-scale building structure with structural deterioration resulting from an internal blast load. Experimental modal analysis, nondestructive testing, and visual documentation of the structure was performed both prior to and after the internal blast, while a suite of blast overpressure transducers and shock accelerometers captured applied loads and structural response during the blast event. This paper presents an overview of the field testing and observed structural response followed by extensive treatment of the experimental characterization of structural damage in a masonry infill wall. Combined stochastic-deterministic system identification is applied to the acquired input-output data from the vibration testing to estimate the modal parameters of the infill wall for both the in-service state and in the postblast condition with damage characterized by interfacial cracking and permanent set deformation. Structural identification by global optimization of a modal parameter-based objective function using genetic algorithm is employed over two stages to produce calibrated finite-element models of the wall in the preblast and postblast conditions. Damage characterization is explored through changes in the structural properties of the calibrated models. Plausibility of the results are supported by observed cracking and spall documented in the experimental program and further reinforced through nonlinear applied element simulation of the response of the wall.

    Keywords: Structural identification, Blast loading, Vibration-based damage detection, Finite-element model updating, Applied element method.

    Timothy P. Kernicky; Matthew J. Whelan; David C. Weggel, P.E.; and Corey D. Rice. Structural Identification and Damage Characterization of a Masonry Infill Wall in a Full-Scale Building Subjected to Internal Blast Load. J. Struct. Eng. , 10.1061/(ASCE)ST.1943-541X.0001158 , D4014013.

  • Collapse Analysis of Utatsu Ohashi Bridge Damaged by Tohuku Tsunami using Applied Element Method

    Abstract: The 2011 Tohuku tsunami on the east coast of Japan resulted in killing more than 15,000 people and missing more than 2,500 people, washing away of more than 250 coastal bridges and loss of US$235 billion. Collapse of coastal bridges due to tsunami impact represents a huge obstacle for rescue works. Therefore, in the current study, the collapse of Utatsu Ohashi bridge is numerically studied. The analysis is carried out using the Applied element Method due to its advan-tages of simulating structural progressive collapse. The AEM is a discrete crack approach, in which elements can be separated, fall and collide to other elements in a fully nonlinear dynamic scheme of computations. The Utatsu Ohashi bridge collapse was successfully simulated using AEM. It was numerically found that the amount of trapped air between deck girders during tsunami had a significant effect on the behavior of the bridge. This is attributed to the buoyant force accompanied with the trapped air. A simplified method for estimating trapped air was assumed and proved to give reasonable results compared to reality. Three different solution examples for mitigating collapse of similar existing bridges were introduced and applied to Utatsu Ohashi bridge case and found to be efficient for preventing collapse.

    Keywords: Tsunami, Impact, Bridge, Progressive Collapse, Applied Element Method.

    Hamed Salem, Suzan Mohssen, Kenji Kosa, Akira Hosoda. Collapse Analysis of Utatsu Ohashi Bridge Damaged by Tohuku Tsunami using Applied Element Method. Journal of Advanced Concrete Technology Vol. 12(2014) No. 10. p.388-402. Released: October 11, 2014.

  • Modelling Debris Distribution of Masonry Panels Subject to Blast Loads Using Experimental & Applied Element Methods

    Abstract: Blast loading and its interaction with structures is a complex phenomenon even in the simplest of cases and modelling its effects is a non-trivial task. This complexity is increased when dealing with  long duration blast due to the drag loads associated with the dynamic pressure. This paper establishes a scientific benchmark for the debris distribution modelling of masonry panels as the foundation of an extended in-depth research study. Experimental trials were conducted in which identical masonry walls were subjected to separate conventional high explosive and long duration blast loads for comparison. Both experiments were subsequently modelled using the Applied Element Method (AEM) with the computational results demonstrating good agreement. The experimental blast loads were characterised with matching overpressures for computational simplicity allowing for a direct comparison between both cases and a clear indication of the effects of impulse, dynamic pressure and entrainment on debris distribution.

    Keywords: Blast, dynamic loading, debris, masonry wall panel, blast experiment, Applied Element Method.

    Keys, Richard and Clubley, Simon (2013) Modelling Debris Distribution of Masonry Panels Subject to Blast Loads Using Experimental & Applied Element Methods. In, 15th International Symposium on Interaction of the Effects of Munitions (ISIEMS 15), Potsdam, DE, 17 - 20 Sep 2013. 10pp.

  • Theoretical and Experimental Research on Progressive Collapse of RC Frame Buildings

    Abstract: Progressive collapse of the buildings has become an important issue to be studied in recent years due to the catastrophic nature of its effects. This subject can be approached from two different perspectives: one where an ideal collapse of the structure is aimed to be achieved and corresponds to the controlled demolition of buildings and other which treats the mitigation of the potential of progressive collapse of structures. The paper presents the results of theoretical and experimental research conducted by the authors regarding the progressive collapse of RC structures from the two perspectives above mentioned.

    Keywords: Progressive collapse, RC Structures, threat mitigation, Applied element method.

    Lupoae, Marin and Constantin, Daniel  (2013). Theoretical and Experimental Research on Progressive Collapse of RC Frame Buildings. National Institute for Research and Development in Construction, Urban Planning and sustainable Development. Urbanism. Architecture. Constructions ISSN 2069-0509 (print) / 2069-6469 (on-line), Vol. 4, issue no. 3 / 2013

  • Performance-Based Seismic Vulnerability Evaluation of Masonry Buildings Using Applied Element Method in a Nonlinear Dynamic-Based Analytical Procedure

    Abstract: A thorough four-step performance-based seismic evaluation for a six-story unreinforced masonry building is conducted. Incremental dynamic analysis is carried out using the applied element method to take advantage of its ability to simulate progressive collapse of the masonry structure including out-of-plane failure of the walls. The distribution of the structural responses and inters-tory drifts from the incremental dynamic analysis curves are used to develop both spectral-based (Sa) and displacement-based (interstory drift) fragility curves at three structural performance levels. The curves resulting from three-dimensional (3-D) analyses using unidirectional ground motions are combined using the weakest link theory to propose combined fragility curves. Finally, the mean annual frequencies of exceeding the three performance levels are calculated using the spectral acceleration values at four probability levels 2%, 5%, 10%, and 40% in 50 years. The method is shown to be useful for seismic vulnerability evaluations in regions where little observed damage data exists.

    Keywords: Progressive Collapse, Seismic, Vulnerability Assessment, Masonry.

    Karbassi A., Nollet M. Performance-Based Seismic Vulnerability Evaluation of Masonry Buildings Using Applied Element Method in a Nonlinear Dynamic-Based Analytical Procedure: Earthquake Spectra: May 2013, Vol. 29, No. 2, pp. 399-426. Keywords: Progressive Collapse, Seismic, Vulnerability Assessment, Masonry.

  • Progressive Collapse Assessment of Framed Reinforced Concrete Structures According to UFC Guidelines for Alternative Path Method

    Abstract: A structure is subjected to progressive collapse when a primary vertical structural element fails, resulting in failure of adjoining structural elements which, in their turn, cause further structural failure leading eventually to partial or total collapse. The failure of a primary vertical support might occur due to extreme loadings such as bomb explosion in a terrorist attack, gas explosion and huge impact of a car in the parking area. Different guidelines such as the General Services Administration (GSA) and the Unified Facilities Criteria (UFC) addressed the structural progressive collapse due to the sudden loss of a main vertical support. In the current study, a progressive collapse assessment according to the UFC guideline is carried out for a typical 10-story reinforced concrete framed structure designed according to (ACI 318-08). Fully nonlinear dynamic analysis for the structure was carried out using Applied Element Method. The investigated cases included the removal of a corner column, an edge column, an edge shear wall, internal columns and internal shear wall. The numerical analysis showed that for economic design, the slabs should be taken into consideration due to their significant effect on structural integrity after support removal. The simplification of the problem into 3D bare frames would lead to uneconomic design. It was found for the studied case that, reinforced concrete structures designed according to ACI code does not meet the UFC limits and that they a have a high potential for progressive collapse for cases of loss of either the corner column or edge shear wall. A modification for the ACI code was proposed to meet the UFC limits.

    Keywords: Progressive collapse; UFC; ELS; AEM; Slabs; Catenry action; Collapsed area and rotation limits

    Helmy H., Salem H. , and Mourad S. Progressive Collapse Assessment of Framed Reinforced Concrete Structures According to UFC Guidelines for Alternative Path Method, Engineering Structures 42 (2012) pp 127–141.

  • The Simulation of an Industrial Building Demolition

    Abstract: The paper presents a way of checking and optimization of a demolition scenario at an industrial building based on controlled blasting method in order to transition to the actual demolition of the building in question. For this purpose we used a specialized computer system that describes the behaviour of the structure at exceptional actions, from the application of forces, the opening and propagation of cracks, the separation structural elements up to total collapse of the building.

    Keywords: Controlled collapse, Demolition, controlled blasting, collapse, Applied element method.

    Simion, Adrian, Dragomir, Claudiu-Sorin (2013). The Simulation of an Industrial Building Demolition. National Institute for Research and Development in Construction, Urban Planning and sustainable Development. Urbanism. Architecture. Constructions ISSN 2069-0509 (print) / 2069-6469 (on-line), Vol. 4, issue no. 2 / 2013

  • Computer-Aided Design of Framed Reinforced Concrete Structures Subjected to Flood Scouring

    Abstract: In the beginning of 2010, several reinforced concrete structures collapsed due to floods in Sinai and Aswan, Egypt. Scour of soil beneath foundations lead to excessive differential settlements, failure of main structural members and finally complete structural collapse. A three-dimensional nonlinear dynamic analysis of a multi-storey reinforced concrete framed structure with induced soil scour under its foundation is carried out using the Applied Element Method. The analysis of the structure is followed until its complete collapse. The numerical analysis is then used to propose a safe design against collapse. Three different alternatives proposed for preventing progressive collapse are independently investigated; floor beams, tie beams connecting footings, and diagonal bracings.

    Increasing the size of the floor beams was found not to have significant effect on mitigating progressive collapse, while the use of diagonal bracings in the ground floor or rigid tie beams connecting the structure’ footings was found to efficiently prevent progressive collapse. With diagonal bracings or rigid tie beams, the excessive differential settlements of the footings can be eliminated and the gravity loads can follow a safe alternative path preventing the structural collapse. The tie beam reinforcement was found to have a significant effect on the structural behavior during such an extreme loading case. Section analysis of the tie beam suggests that its ultimate strength should be based on rupture of main reinforcement, which is more economical and appropriate for such loading case.

    Keywords: Flood scouring, progressive collapse, Applied Element Method, tie beams

    Hamed, S. Computer-Aided Design of Framed Reinforced Concrete Structures Subjected to Flood Scouring. Journal of American Science 2011;7(10):191-200]. (ISSN: 1545-1003). http://www.americanscience.org.

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