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1 – 10 of over 1000George Markou and Manolis Papadrakakis
The purpose of this paper is to present a simplified hybrid modeling (HYMOD) approach which overcomes limitations regarding computational cost and permits the simulation and…
Abstract
Purpose
The purpose of this paper is to present a simplified hybrid modeling (HYMOD) approach which overcomes limitations regarding computational cost and permits the simulation and prediction of the nonlinear inelastic behavior of full-scale RC structures.
Design/methodology/approach
The proposed HYMOD formulation was integrated in a research software ReConAn FEA and was numerically studied through the use of different numerical implementations. Then the method was used to model a full-scale two-storey RC building, in an attempt to demonstrate its numerical robustness and efficiency.
Findings
The numerical results performed demonstrate the advantages of the proposed hybrid numerical simulation for the prediction of the nonlinear ultimate limit state response of RC structures.
Originality/value
A new numerical modeling method based on finite element method is proposed for simulating accurately and with computational efficiency, the mechanical behavior of RC structures. Currently 3D detailed methods are used to model single structural members or small parts of RC structures. The proposed method overcomes the above constraints.
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Khalid Abou El-Ftooh, Ahmed Atta, Ayman Ahmed Seleemah and Salah El-Din Fahmy Taher
Separately, nonlinear finite element analysis, artificial neural networks (ANNs) and continuous damage mechanics (CDM) attracted many investigators to model masonry infilled frames…
Abstract
Purpose
Separately, nonlinear finite element analysis, artificial neural networks (ANNs) and continuous damage mechanics (CDM) attracted many investigators to model masonry infilled frames. The purpose of this paper is to pursue four phases to develop a versatile model for partially and fully low-rise infilled RC frames using these tools.
Design/methodology/approach
The first phase included the study of the behavior of 1,620 low-rise infilled reinforced concrete frames using macro-scale nonlinear pushover finite element analysis. The approach helped to explore the effects of imposing different masonry infill distributions for one of the typical models of school buildings in Egypt. The outputs of this phase were used in the second phase for the development of an ANN model where input neurons included number of stories, continuity conditions, frame geometry, infill distribution and properties of RC sections. The third phase included the employment of the notions of CDM on the structural scale. Monitoring frames’ stiffness degradation allowed for damage variables identification. In the fourth phase, the simpler equivalent static lateral load (ESLL) for elastic analysis was employed in conjunction with ANN and CDM to obtain the capacity curves for partially and fully low-rise infilled RC frames.
Findings
The obtained capacity curves were compared with the nonlinear finite element results. The close agreement of all curves indicated how rigorous, yet simple, the suggested solution procedure is.
Social implications
The study is concerned with an important type of service buildings. These are the school buildings of Egypt.
Originality/value
The paper presents a combination of four phases that include FE analysis, ANNs, ESLL, and CDM to obtain the capacity curves for partially and fully low-rise infilled RC frames. Such a combination of approaches in tackling a practical problem related to service buildings is innovative and deserves research interest.
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The occurrence of multiple hazards in extreme conditions is not unknown nowadays, but the sustainability of the reinforced concrete structures under such scenarios form…
Abstract
Purpose
The occurrence of multiple hazards in extreme conditions is not unknown nowadays, but the sustainability of the reinforced concrete structures under such scenarios form competitive challenges in civil engineering profession. Among all, fire following earthquake (FFE) is categorized under multiple extreme load scenarios which causes sequential damages to the structures. This paper aims to experiment a full-scale RC frame sub-assemblage for the FFE scenario and assess each stage of damage through the nondestructive testing method.
Design/methodology/approach
Two levels of simulated earthquake damages, i.e. immediate occupancy (IO) level and life safety (LS) level of structural performance were induced to the test frame and then, followed by a realistic compartment fire of 1 h duration. Also, the evaluation of damage to the RC frame after the fire subsequent to the earthquake was carried out by obtaining the ultimate capacity of the frame. Ultrasonic pulse velocity and rebound hammer test were conducted to assess the structural endurance of the damaged frame. Cracks were also marked during mechanical damages to the test frame to study the nature of its propagation.
Findings
Careful visual inspection during and after the fire test to the test frame were done. To differentiate between concrete chemically affected by the fire or physically damaged is an important issue. In situ inspection and laboratory tests of concrete components have been performed. Concrete from the test frame was localized with thermo-gravimetric analysis. The UPV results exhibited a sharp decrease in the strength of the concrete material which was also confirmed via the DTA, TGA and TG results. It is important to evaluate the residual capacity of the entire structure under the FFE scenario and propose rehabilitation/retrofit schemes for the building structure.
Research limitations/implications
The heterogeneity in the distribution of the damage has been identified due to variation of fire exposure. The study only highlights the capabilities of the methods for finding the residual capacity of the RC frame sub-assemblage after an occurrence of an FFE.
Originality/value
It is of find kind of research work on full-scale reinforced concrete building. In this, an attempt has been made for the evaluation of concrete structures affected by an FFE through nondestructive and destructive methods.
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Ranjit Kumar Chaudhary, Tathagata Roy and Vasant Matsagar
Despite recognizing the significance of risk-based frameworks in fire safety engineering, the usual approach in structural fire design is largely member/component level, wherein…
Abstract
Purpose
Despite recognizing the significance of risk-based frameworks in fire safety engineering, the usual approach in structural fire design is largely member/component level, wherein effect of uncertainties influencing the fire resistance of structures are not explicitly considered. In this context, a probabilistic framework is presented to investigate the vulnerability of a reinforced concrete (RC) members and structure under fire loading scenario.
Design/methodology/approach
The RC structures exposed to fire are modeled in a finite element (FE) platform incorporating material and geometric nonlinearity, in which the transient thermo-mechanical analysis is carried out by suitably incorporating the temperature variation of thermal and mechanical properties of both concrete and steel rebar. The stochasticity in the system is considered in structural resistance, thermal and fire model parameters, and the subsequent fragility curves are developed considering threshold limit state of deflection.
Findings
The fire resistance of RC structure is reported to be significantly lower in comparison to the RC members, thereby illustrating the current prescriptive design approaches based on studies of structural member behavior to be crucial from a safety and reliability point of view.
Practical implications
The framework developed for the vulnerability assessment of RC structures under fire hazard through FE analysis can be effectively used to estimate the structural fire resistance for other similar structure to enhance safety and reliability of structures under such extreme threats.
Originality/value
The paper proposes a novel methodology for vulnerability assessment of three-dimensional RC structures under fire hazard through FE analysis and provides comparison of the structural fragility with fragility developed for structural members. Moreover, the research emphasizes to assume 3D behavior of the structure rather than the approximate 2D behavior.
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Nibas Apu and Ravi Sinha
Increasing awareness of the society and complying with design requirements of building codes for seismic safety of structures and inhabitants during severe earthquakes are the…
Abstract
Purpose
Increasing awareness of the society and complying with design requirements of building codes for seismic safety of structures and inhabitants during severe earthquakes are the primary purpose of seismic analysis. This study aims to present the variability in seismic fragility functions for frames of different heights for the most vulnerable condition of structure using nonlinear time history analysis.
Design/methodology/approach
A total of 4, 8 and 20 stories reinforced concrete (RC) moment-resisting two-dimensional frames are considered for this study. Ground motions (GM) are selected as per the conditional mean spectrum and these are conditioned on a target spectral acceleration at the concern time period. RC frames are designed and detailed as per Indian standards. A concentrated plasticity approach is adopted for non-linear analytical modeling of the RC frames. Deterministic capacity limit states in terms of maximum inter-story drift ratio are considered for different damage states. Fragility functions have been derived following a lognormal distribution from incremental dynamic analysis curves. Finally, the maximum likelihood estimation of the response is obtained for fitting curves with observed fragility.
Findings
The fragility functions of the three structures reflect that under critical or extreme conditions of GM the taller buildings have higher fragility than the shorter buildings for each level of limit states even though both are designed to meet their code-level design forces.
Research limitations/implications
The study is conducted on the extreme scenario of GM conditioned on the fundamental time period of each building, whereas comparison can be developed by selecting various methodologies of GM set. The probabilistic capacity model can be developed for future studies to check the fragility variation with deterministic and probabilistic capacity.
Originality/value
The investigation endeavors to present a comprehensive fragility assessment framework by analytical method. The outcome will be useful in the development of a disaster management strategy for new or old buildings and the response of seismic force with a variation of the building’s height. The findings will also be useful for updating the earthquake-resistant building codes for the new building construction in a similar context.
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Faisal Mehraj Wani, Jayaprakash Vemuri and Rajaram Chenna
The objective of the study is to examine the response of reinforced concrete (RC) structures subjected to Near-Fault Ground Motions (NFGM) and highlight the importance of…
Abstract
Purpose
The objective of the study is to examine the response of reinforced concrete (RC) structures subjected to Near-Fault Ground Motions (NFGM) and highlight the importance of considering various factors including the influence of the relative geographical position of near-fault sites that can affect the structural response during an earthquake.
Design/methodology/approach
In this paper, the response of a four-storey RC building subjected to NFGMs with varied characteristics like hanging wall and footwall in conjunction with directivity and the effect of pulse-like ground motions with rupture direction are investigated to understand the combined influence of these factors on the behavior of the structure. Furthermore, the capacity and demand of the structural element are investigated for computing the performance ratio.
Findings
Results from this study indicate that the most unfavorable combinations for structural damage due to near-fault ground motion are the hanging wall with forward rupture, the fault normal component of ground motions, and pulse-like ground motions with forward directivity.
Originality/value
The results from this study provide valuable insight into the response of RC structures subjected to NFGM and highlight the importance of considering various factors that can affect the structural response during an earthquake. Moreover, the computation of capacity and demand of the critical beam indicates exceedance of desired limits, resulting in the early deterioration of the structural elements. Finally, the analytical analysis from the present study confirms that the hanging wall with forward ruptures, pulse-like motions, and fling steps are the most unfavorable combinations for seismic structural damage.
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Kevin Quinn Walsh, Reza Jafarzadeh, Nicola M. Short and Jason M. Ingham
The purpose of this article is to assist facilities asset managers who are dealing with regulatory environments pertaining to earthquakes and buildings. These professionals can…
Abstract
Purpose
The purpose of this article is to assist facilities asset managers who are dealing with regulatory environments pertaining to earthquakes and buildings. These professionals can learn a great deal from the successes and short-comings of a case study programme from the Auckland Council Property Department (ACPD), which manages the public facilities portfolio for the largest local administrative region in New Zealand in both population and landmass.
Design/methodology/approach
ACPD has initiated its response to New Zealand’s earthquake mitigation mandates by identifying buildings most at risk to an earthquake in its large and varied portfolio through the use of a rapid building evaluation programme strategically targeted to vulnerable building types with consequential attributes, including service type, number of occupants, floor area and geographic location.
Findings
ACPD was able to rapidly cull down its portfolio of approximately 3,500 buildings to just over 100 “high-exposure” buildings in urgent need of evaluation, set priorities for future evaluations, estimate needed operational and capital expenditures for long-term planning and provide useful information to more general facilities management decision-making processes.
Originality/value
A number of major cities around the world in areas of high seismicity have enacted ordinances mandating seismic retrofitting. However, much of the existing guiding literature regarding earthquake-related portfolio evaluations and costs pertains to specific scenarios involving real or hypothetical earthquakes. This case study, in contrast, details the approach taken by a public portfolio owner responding to legal mandates and attempting to quantify and reduce its life-safety risk exposure across a large portfolio as efficiently as possible using readily available information, a rapid building evaluation programme and best-practice predictive models for consulting and construction work.
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Puneet Kumar and Gaurav Srivastava
Reinforced concrete structural frames with masonry infills (infill-frames) are commonly used for construction worldwide. While the behavior of such frames has been studied…
Abstract
Purpose
Reinforced concrete structural frames with masonry infills (infill-frames) are commonly used for construction worldwide. While the behavior of such frames has been studied extensively in the context of earthquake loading, studies related to their fire performance are limited. Therefore, this study aims to characterize the behavior of infill-frames under fire exposure by presenting a state-of-the-art literature review of the same.
Design/methodology/approach
Both experimental and computational studies have been included with a special emphasis on numerical modeling (simplified as well as advanced). The cold behavior of the infill-frame and its design requirements in case of fire exposure are first reviewed to set the context. Subsequently, the applicability of numerical modeling strategies developed for modeling cold infill-frames to simulate their behavior under fire is critically examined.
Findings
The major hurdles in developing generic numerical models for analyzing thermo-mechanical behavior of infill-frames are identified as: lack of temperature-dependent material properties, scarcity of experimental studies for validation and idealizations in coupling between thermal and structural analysis.
Originality value
This study presents one of the most popular research problems connected with practical and reliable utilization of numerical models, as a good alternative to expensive traditional furnace testing, in assessing fire resistance of infill-frames. It highlights major challenges in thermo-mechanical modeling of infill-frames and critically reviews the available approaches for modeling infill-frames subjected to fire.
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H. Kit Miyamoto, Amir S.J. Gilani and Akira Wada
School buildings have suffered disproportionate damage during past and recent earthquakes. For example, during the 2008 Sichuan earthquake, many school buildings collapsed…
Abstract
Purpose
School buildings have suffered disproportionate damage during past and recent earthquakes. For example, during the 2008 Sichuan earthquake, many school buildings collapsed, resulting in loss of life. School buildings in many other parts of the world are also susceptible to this type of widespread damage because of inadequate design, detailing, or poor construction quality. The purpose of this paper is to show how these fatal flaws can be mitigated prior to future catastrophe by using good engineering practice to retrofit vulnerable schools.
Design/methodology/approach
Conventional and innovative, cost‐effective, and reliable tools are available to prevent damage to schools. It is often necessary to examine a group of buildings or all structures in a locality and develop a comprehensive risk management plan for the vulnerable buildings. As an example, a comprehensive evaluation and retrofit project, under the auspices of the World Bank, is currently under way in Istanbul, Turkey, to address vulnerable school and hospital buildings as discussed in the paper. As part of this effort in Turkey, a guideline that relies on state‐of‐the‐art evaluation and retrofit methods has been developed to assist the local engineers.
Findings
Implementation of the program based on the uniform standards developed in the retrofit guidelines, has significantly reduced the seismic risk to schools in Istanbul.
Practical implications
The proposed evaluation and implementation technique can be utilized by governments worldwide to prevent further damage to key infrastructure and save millions of lives.
Originality/value
Innovative retrofits can be used to provide enhanced performance and provide seismic resiliency for cluster of school buildings.
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RC columns are very susceptible to fire, as besides the detrimental effects due to this action, second‐order effects play a significant role. In this work, the aim is to consider…
Abstract
Purpose
RC columns are very susceptible to fire, as besides the detrimental effects due to this action, second‐order effects play a significant role. In this work, the aim is to consider the ISO834 standard fire, and the focus is put on checking the proper use of a simplified method suggested on Annex B.3 of EC2 to account for the second‐order effects in RC columns.
Design/methodology/approach
The use of Annex B.3 of EC2 is obscure in what concerns the peak strain to be considered at the most deformed cross‐section concrete fibres, and this affects the evaluation of the second‐order moment installed in the RC column during the fire. Two hypotheses are analysed in the paper, and validated against the calculations from the advanced code SAFIR: the one where the classical limit of 3.5‰ is assumed for the peak concrete strain in compression, and a more refined compatibility of the section total strains.
Findings
The simulations demonstrate that using the simplified method with hypothesis H1 leads to unsafe conclusions. Conversely, hypothesis H2 compares much better with SAFIR predictions, and it can be rather easily adopted in real applications.
Originality/value
The indications provided here for the proper application of the simplified method are very useful for practical use. They overcome an unclear aspect on its implementation, not yet previously addressed.
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