• International Journal of High-Rise Buildings
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• v.3 no.3
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• pp.223-230
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• 2014

In this study the progressive collapse resisting capacities of tall diagrid buildings were evaluated based on arbitrary column removal scenario, and the seismic load-resisting capacities were investigated through fragility analysis and ATC 63 procedure. As analysis model structures both regular and twisted diagrid structures were designed and their load-resisting capacities were compared by nonlinear static and dynamic analyses. The analysis results showed that the progressive collapse potential of twisted buildings decreased as the twisting angle increased, but the seismic fragility or the probability of failure decreased as the twisting angle increased.

• Steel and Composite Structures
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• v.26 no.5
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• pp.635-647
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• 2018

In order to improve the efficiency of the Reinforced Concrete, RC, structures against progressive collapse, this paper proposes a procedure using alternate path and specific local resistance method to resist progressive collapse in intermediate RC frame structures. Cap truss consists of multiple trusses above a suddenly removed structural element to restrain excessive collapse and provide an alternate path. Steel strut is used as a brace to resist compressive axial forces. It is similar to knee braces in the geometry, responsible for enhancing ductility and preventing shear force localization around the column. In this paper, column removals in the critical position at the first story of two 5 and 10-story regular buildings strengthened using steel strut or cap truss are studied. Based on nonlinear dynamic analysis results, steel strut can only decrease vertical displacement due to sudden removal of the column at the first story about 23%. Cap truss can reduce the average vertical displacement and column axial force transferred to adjacent columns for the studied buildings about 56% and 61%, respectively due to sudden removal of the column. In other words, using cap truss, the axial force in the removed column transfers through an alternate path to adjacent columns to prevent local or general failure or to delay the progressive collapse occurrence.

• Earthquakes and Structures
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• v.23 no.6
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• pp.503-515
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• 2022

Global or partial damage to a structure due to the failure of gravity or lateral load-bearing elements is called progressive collapse. In the present study, the alternate load path (ALP) method introduced by GSA and UFC 4-023-03 guidelines is used to evaluate the progressive collapse in special steel moment-resisting frame (SMRF) buildings. It was assumed that the progressive collapse is due to the earthquake force and its effects after the removal of the elements still remain on the structures. Therefore, nonlinear dynamic time history analysis employing 7 earthquake records is used to investigate this phenomenon. Internal and external column removal scenarios are investigated and the stiffness of the connections is changed from semi-rigid to rigid. The results of the analysis performed in the OpenSees program show that the loss of the bearing capacity of an exterior column due to a seismic event and the occurrence of progressive collapse can increase the inter-story drift of the structure with semi-rigid connections by more than 50% and make the structure unable to satisfy the life safety performance level. Furthermore, connection stiffness severely affects the redistribution of forces and moments in the adjacent elements of the removed column.

• Structural Engineering and Mechanics
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• v.91 no.4
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• pp.369-382
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• 2024

The earthquake loss assessment framework of ductile reinforced concrete (or RC) frame using component-performance -based methodology was studied in this paper. The elasto-plastic rotation angle was used as the damage indicator of structural component, and the damage-to-loss model was proposed on the basis of the deformation indicator of structural component. Dynamic instability during incremental dynamic analysis was taken as collapse criterion, and column failure was taken as criterion that structure has to be demolished. Expected earthquake losses of low-rise, mid-rise and high-rise RC frames were discussed. The expected earthquake loss encompassed collapse loss, demolition loss and repair loss. Furthermore, component groups of RC frame were divided into structural components, nonstructural components and rugged components. The results indicate that ductile RC frame is more likely to be demolished than collapse, especially in low-rise and mid-rise RC frames. Furthermore, the less collapse margin ratio the structure has, the more demolition probability the structure will suffer under rare earthquake. The demolition share of total earthquake loss might be more prominent than repair share and collapse share in ductile RC frame.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.9
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• pp.62-68
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• 2011

Power system needs to sustain high reliability due to its complexity and security. The reliability prediction method is usually based on independent failure. However, in practice, the Common Cause Failures(CCF) and Cascading failure occur to the facilities in power system as well as independent failures in many cases. The CCF and Cascading failure turn out the system collapse seriously in a wide range. Therefore to improve the reliability of the power system practically, it is required that the analysis is conducted by using the CCF and Cascading failure. This paper describes the CCF and Cascading failure modeling combined with independent failure. The incorporated model of independent failure, CCF and cascading failure is proposed and analyzed, and it is applied to the distribution power system in order to examine this method.

• Earthquakes and Structures
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• v.7 no.4
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• pp.587-607
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• 2014

Progressive collapse, which is referred to as the collapse of the entire building under local damages, is a common failure mode happened by earthquakes. The collapse process highly depends on the whole structural system. Since, asymmetry of the building plan leads to the local damage concentration; it may intensify the progressive collapse mechanism of asymmetric buildings. In this research the progressive collapse of regular and irregular 6-story RC ordinary moment resisting frame buildings are studied in the presence of the earthquake loads. Collapse process and collapse propagation are investigated using nonlinear time history analyses (NLTHA) in buildings with 5%, 15% and 25% mass asymmetry with respect to the number of collapsed hinges and story drifts criteria. Results show that increasing the value of mass eccentricity makes the asymmetric buildings become unstable earlier and in the early stages with lower number of the collapsed hinges. So, with increasing the mass eccentricity in building, instability and collapse of the entire building occurs earlier, with lower potential of the progressive collapse. It is also demonstrated that with increasing the mass asymmetry the decreasing trend of the number of collapsed beam and column hinges is approximately similar to the decreasing trend in the average story drifts of the mass centers and stiff edges. So, as an alternative to a much difficult-to-calculate local response parameter of the number of collapsed hinges, the story drift, as a global response parameter, measures the potential of progressive collapse more easily.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.5 s.236
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• pp.754-761
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• 2005

The 40\% of wall thickness criterion which has been used as a plugging rule of steam generator tubes is applicable only to a single cracked tube. In the previous studies performed by authors, several global failure prediction models were introduced to estimate the failure loads of steam generator tubes containing two adjacent parallel axial through-wall cracks. These models were applied for thin plates with two parallel cracks and the COD base model was selected as the optimum one. The objective of this study is to verify the applicability of the proposed optimum global failure prediction model for real steam generator tubes with two parallel axial through-wall cracks. For the sake of this, a series of plastic collapse tests and finite element analyses have been carried out fur the steam generator tubes with two machined parallel axial through-wall cracks. Thereby, it was proven that the proposed optimum failure prediction model can be used as the best one to estimate the failure load quite well. Also, interaction effects between two adjacent cracks were assessed through additional finite element analyses to investigate the effect on the global failure behavior.

• Geomechanics and Engineering
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• v.10 no.1
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• pp.21-35
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• 2016

Employing non-associated flow rule and Power-Law failure criterion, the failure mechanisms of tunnel roof in homogeneous and layered soils are studied in present analysis. From the viewpoint of energy, limit analysis upper bound theorem and variation principle are introduced to study the influence of dilatancy on the collapse mechanism of rectangular tunnel considering effects of supporting force and seepage force. Through calculation, the collapsing curve expressions of rectangular tunnel which are excavated in homogeneous soil and layered soils respectively are derived. The accuracy of this work is verified by comparing with the existing research results. The collapsing surface shapes with different dilatancy coefficients are draw out and the influence of dilatancy coefficient on possible collapsing range is analyzed. The results show that, in homogeneous soil, the potential collapsing range decreases with the decrease of the dilatancy coefficient. In layered soils, the total height and the width on the layered position of possible collapsing block increase and the width of the falling block on tunnel roof decrease when only the upper soil's dilatancy coefficient decrease. When only the lower soil's dilatancy coefficient decrease or both layers' dilatancy coefficients decrease, the range of the potential collapsing block reduces.

• International Journal of Concrete Structures and Materials
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• v.1 no.1
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• pp.29-36
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• 2007

The purpose of this paper is the assessment of the capacity of the reinforced concrete (RC) elements of an arch bridge when they are subjected to contact and near-contact explosive charges of various amounts, and the estimation of the critical charges for these components. The bridge considered is the Tenza Viaduct, a decommissioned structure south of Naples, Italy. Its primary elements, deck, piers and arches were analyzed. The evaluation was accomplished via numerical analyses that made possible to obtain the elements dynamic response when they are exposed to blast loading conditions. To evaluate the member's capacities, failure criteria for deck, piers and arches were proposed based on concrete damage parameters. Additionally, curves relating the explosive charge to the residual capacity and to damage level of the elements were also developed. The results of this work were taken into account to investigate the progressive collapse of the global structure.

• Earthquakes and Structures
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• v.21 no.5
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• pp.445-460
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• 2021

This study experimentally explored the behaviour of 12 concrete filled steel tube (CFST) and steel tube columns subjected to lateral cyclic loading. The L/D ratio was 12.3 while D/t ratios were 45.4, 37.8 and 32.4, classifying these 12 specimens into 3 groups. Each group included 3 CFST and 1 steel tube columns and were tested to failure. The experimental results indicated that CFST specimens reached the state of 'collapse prevention' (drift 4%) prior to the occurrence of local buckling. Strength degradation of CFST specimens did not occur up to the failure by buckling. This showed the favourable characteristic of CFST columns in preventing collapse of structures subjected to earthquakes. The high energy absorption capability in the post collapse limit state was appropriate for dissipating energy in structures. Compared to steel tube columns, CFST columns delayed local buckling and prevented inward buckling. Consequently, CFST columns exhibited their outstanding seismic performance in terms of the increased ultimate resistance, capacity to sustain 2-3 additional load cycles and significantly higher drift. A simple and reasonably accurate model was proposed to predict the ultimate strength of CFST columns under lateral cyclic loading.