• Coupled systems mechanics
• /
• v.7 no.2
• /
• pp.111-139
• /
• 2018

A successful methodology for modelling controlled destruction and progressive collapse of 2D reinforced concrete frames is presented in this paper. The strategy is subdivided into several aspects including the failure mechanism creation, and dynamic motion in failure represented with multibody system (MBS) simulation that are used to jointly capture controlled demolition. First phase employs linear elasto-plastic analysis with isotropic hardening along with softening plastic hinge concept to investigate the complete failure of structure, leading to creation of final failure mechanism that behaves like MBS. Second phase deals with simulation and control of the progressive collapse of the structure up to total demolition, using the nonlinear dynamic analysis, with conserving/decaying energy scheme which is performed on MBS. The contact between structure and ground is also considered in simulation of collapse process. The efficiency of the proposed methodology is proved with several numerical examples including six story reinforced concrete frame structures.

• Korean Journal of Veterinary Research
• /
• v.63 no.2
• /
• pp.10.1-10.5
• /
• 2023

A 6-month-old female Border Collie presented with a history of collapse after strenuous exercise. The dog was normal between episodes but experienced loss of focus and ataxia after exercise. This is particularly noticeable under hot weather conditions. No remarkable findings were observed in the diagnostic tests. Based on these results, the patient was tentatively diagnosed with Border Collie collapse (BCC). After exercise restriction, the dog had no episode of collapse and remained clinically well with no signs until the follow-up period of 8 months was complete. To our knowledge, this is the first case report of BCC in South Korea.

• Structural Engineering and Mechanics
• /
• v.12 no.2
• /
• pp.157-168
• /
• 2001

In this paper, experimental investigation into the behavior of reinforced concrete (RC) columns tested under large lateral displacement with four different types of loading arrangements is presented. Each loading arrangement has a different system for controlling the consistency of the loading condition. One of the loading arrangements used three units of link mechanism to control the parallelism of the top and bottom stub of column during testing, and the remaining employed eight hydraulic jacks for the same purpose. The loading systems condition used in this investigation were similar to the actual case in a moment-resisting frame where the tested column was displaced in a double curvature. Ten model column specimens, divided into four series were prepared. Two columns were tested monotonically until collapse, and unless failure took place at an earlier stage of loading, the remaining eight columns were tested under cyclic loading. Test results indicated that the proposed system to keep the top and bottom stubs parallel during testing performed well.

• The Journal of Korean Academy of Prosthodontics
• /
• v.38 no.4
• /
• pp.383-401
• /
• 2000

• The Journal of the Korean dental association
• /
• v.57 no.5
• /
• pp.288-295
• /
• 2019

Sleep-disordered breathing (SDB) is defined as a disturbed breathing during sleep caused by repetitive upper airway collapse. Complete collapse causes a cessation of breathing, known as obstructive sleep apnea (OSA) and snoring can arise from partial collapse. Undiagnosed and untreated OSA means recurrent intermittent hypoxemia and leads to a variety of cardiovascular disorders, disturbed neurocognition, and excessive daytime sleepiness. Various behavioral modalities have been suggested for treating snoring and sleep apnea including changing the sleep position, avoiding alcohol, and weight loss. Until now continuous positive airway pressure (CPAP) therapy is one of effective treatment for patients with OSA, but its discomfort causes less tolerance and compliance. Therefore, clinical effectiveness and convenience for oral appliance have emerged and the role of dentists has become more important in the management of OSA.

• Advances in concrete construction
• /
• v.9 no.3
• /
• pp.235-248
• /
• 2020

Progressive collapse in a structure occurs when load bearing members are failed and the adjoining structural elements cannot resist the redistributed forces and fails subsequently, that leads to complete collapse of structure. Recently, construction using precast concrete technology is adopted increasingly because it offers many advantages like faster construction, less requirement of skilled labours at site, reduced formwork and scaffolding, massive production with reduced amount of construction waste, better quality and better surface finishing as compared to conventional reinforced concrete construction. Connections are the critical elements for any precast structure, because in past, major collapse of precast structure took place because of connection failure. In this study, behavior of four different precast wet connections with U shaped reinforcement bars provided at different locations is evaluated. Reduced 1/3^rd scale precast beam column assemblies having two span beam and three columns with removed middle column are constructed and examined by performing experiments. The response of precast connections is compared with monolithic connection, under column removal scenario. The connection region of test specimens are filled by cast-in-place micro concrete with and without polypropylene fibers. Performance of specimen is evaluated on the basis of ultimate load carrying capacity, maximum deflection at the location of removed middle column, crack formation and failure propagation. Further, Finite element (FE) analysis is carried out for validation of experimental studies and understanding the performance of structural components. Monolithic and precast beam column assemblies are modeled using non-linear Finite Element (FE) analysis based software ABAQUS. Actual experimental conditions are simulated using appropriate boundary and loading conditions. Finite Element simulation results in terms of load versus deflection are compared with that of experimental study. The nonlinear FE analysis results shows good agreement with experimental results.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.6
• /
• pp.1382-1390
• /
• 1990

Accurate load-carrying capacities and moment distributions of thin circular plates are obtained for clamped or simply-supported boundary condition under various concentrated circular loadings. The material is regarded as perfectly-plastic based on an arbitrary yield function such as the Tresca yield function, the Johansen yield function, and the farmily of .betha.-norms which possesses the von Mises yield function and the Frobenius norm. To obtain the lower bound solutions, a maximization formulation is derived and implemented for efficient numerical calculation with a finite difference method and the modified Newton's method. The numerical results demonstrate plastic collapse behavior of circular plates and provide their design criteria.

• Steel and Composite Structures
• /
• v.29 no.2
• /
• pp.231-242
• /
• 2018

As a lateral load resisting component, buckling restrained steel plate shear walls (BRW) have excellent energy dissipating capacity. Similar to thin steel plate shear walls, the mechanical behavior of BRWs depends on the boundary elements (adjacent beams and columns) which need adequate strength and stiffness to ensure the complete yielding of BRWs and the emergence of expected plastic collapse mechanism of frame. This paper presents a theoretical approach to estimate the design forces for boundary elements of beam-connected BRW (i.e., The BRW is only connected to beams at its top and bottom, without connections to columns) using a fundamental plastic collapse mechanism of frame, a force transferring model of beam-connected BRW and linear beam and column analysis. Furthermore, the design method of boundary beams and columns is presented. The proposed approach does not involve nonlinear analyses, which can be easily and efficiently used to estimate the design forces of beams and columns in a frame with BRWs. The predicted design forces of boundary elements are compared with those from nonlinear finite element analyses, and a good agreement is achieved.

• Structural Engineering and Mechanics
• /
• v.53 no.1
• /
• pp.173-188
• /
• 2015

Several structural calamities in the second half of the 20th century have shown that adequate collapse-resistance cannot be achieved by designing the individual elements of a structure without taking their interconnectivity into consideration. It has long been acknowledged that membrane behaviour of reinforced concrete structures can significantly increase the robustness of a structure and delay a complete collapse. An experimental large-scale test was conducted on a horizontally restrained, continuous reinforced concrete slab exposed to an artificial failure of the central support and subsequent loading until collapse of the specimen. Within this investigation the development of catenary action associated with the formation of large displacements was observed to increase the ultimate load capacity of the specimen significantly. The development of displacements, strains and horizontal forces within this investigation confirmed a load transfer process from an elastic bending mechanism to a tension controlled catenary mechanism. In this contribution a special focus is directed towards strain and crack development at critical sections. The results of this contribution are of particular importance when validating numerical models related to the development of catenary action in concrete slabs.

• Journal of Chest Surgery
• /
• v.26 no.9
• /
• pp.718-721
• /
• 1993

Reexpansion pulmonary edema[ RPE ] with hypoxemia and hypotension is a very rare complication of the treatment of lung collapse secondary to pneumothorax and pleural effusion. We experienced two cases of RPE. One is a 29 year old male with complete right pneumothorax and the other is a 20 year old female with massive right pleural effusion. Life threatening pulmonary edema was developed soon after insertion of chest tube in both. Fortunately, RPE was detected early and intensive treatment was performed. They were discharged without complication. Although RPE with hypoxemia and hypotension is rare , it is very serious and occasionally life-threatening. So, chest surgeon treating lung collapse must be aware of the possibility of RPE and make an effort to prevent the occurence of this condition.