Evaluation of the Collapse Potential Magnitude of Untreated and Treated Collapsible Gypseous Soil – A New Procedure

Ahmed S. A. Al-Gharbawi,Mohammed Y. Fattaha,Mahmood R. Mahmood 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.6

Many researches have been conducted to study the collapse potential of collapsible soils using collapse tests; single-oedometer tests, and double-oedometer tests. The radical rearranging of particles in response to a significant volume loss from wetting under loading is the definition of collapse. The main goal of this study is to create a method for recognition of gypseous soil that is susceptible to collapse. The suggested procedure depends on using a sample larger than that used in conventional collapse tests and the saturation of sample is done by flowing water from the bottom to the top of the sample. The new idea for the modified collapse test was made because of the limitations of conventional tests including the small size of sample that may not give a suitable collapse. In addition, the saturation process of the sample may not saturate all the particles. Also, the behavior of collapsible gypseous soil was investigated on soil improved with different Magnesium Oxide percentages (0, 5, 10, and 15%) and carbonated Magnesium Oxide with variable carbonation times (0, 1, 3, and 24 hours). The soil was prepared at two relative densities of 35 and 75 percent relative density. The collapse potential was investigated using a modified Rowe cell with soil moisture content sensors. The results illustrated that the size of the sample affects the collapsibility, the collapse potential increased from 15.8% to 22.3% and the collapse severity is changed from (severe trouble) to (very severe trouble) for the natural untreated gypseous soil using the conversional tests and modified test, respectively. The collapse potential increased by about 40% for the soil treated with different percentages of “Magnesium Oxide”. For the modified test, the collapse potential decreased by about 93% when using 10 percent of Magnesium Oxide then the sample was carbonated for 3 hours as compared with untreated soil.

Energy-based sidesway collapse fragilities for ductile structural frames under earthquake loadings

Deniz, Derya,Song, Junho,Hajjar, Jerome F. Elsevier 2018 ENGINEERING STRUCTURES Vol.174 No.-

<P><B>Abstract</B></P> <P>In assessing the likelihood of structural collapse under strong earthquake motions, uncertainties in structural properties and ground motions can be incorporated by use of a probabilistic analysis framework in conjunction with analysis methods such as incremental dynamic analysis (IDA). Maximum inter-story drift ratio (<I>IDR</I>) is typically selected as the key descriptor to characterize the global behavior of structural system in such a probabilistic assessment. The structural collapse capacity is often defined in terms of a threshold value of <I>IDR</I> or a reduced slope of the IDA curve between a selected seismic intensity measure and the corresponding <I>IDR</I>. However, collapse assessment approaches based on <I>IDR</I> may not accurately represent the overall structural collapse behavior due to redistribution and variation of local damage within the structure. Moreover, results of collapse predictions are found to be sensitive to variability in such drift measures, and assumed threshold values used in the collapse criterion. Recently, an energy-based seismic collapse criterion has been developed to describe collapse in terms of dynamic instability of the whole structural system caused by gravity loads. Using the energy-based collapse criterion, this paper proposes a more effective sidesway collapse risk assessment approach of ductile planar frames subjected to horizontal seismic loadings based on a new key descriptor of structural performance. The key descriptor, designated as the equivalent-velocity ratio, is related to the ratio of the energy dissipated through structural degradation to the seismic input energy. Using the equivalent-velocity ratio, a probabilistic collapse assessment method is developed for systematic treatment of uncertainties in the ground motions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new descriptor’s been proposed for seismic performance of ductile moment frames. </LI> <LI> New seismic demand models and collapse fragility relations are obtained for frames. </LI> <LI> The new collapse fragility relations are compared with the traditional approaches. </LI> <LI> The developed techniques help achieve reliable prediction of structural collapse. </LI> </UL> </P>

낙상 감지 폰의 개발과 낙상판단 알고리즘

장덕성 대한임베디드공학회 2015 대한임베디드공학회논문지 Vol.10 No.1

To deal with the emergency of the solitary aged people, we have developed a collapse-sensing phone, in which a collapse sensor, a GPS receiving chipset and a CDMA sending chipset are included. The general cellular phone is somewhat expensive communication device using sound and characters, but the collapse-sensing phone is a cheaper and popular version. If the collapse sensor recognizes a certain of collapse of the aged people, CDMA sending chipset will send the location of the phone which is received from satellite by GPS receiving chipset. In this paper, a collapse recognition algorithm which is developed by using much experimental data, will be introduced to explain how to recognize the real collapse from fast sitting or immediate standing after collapse. Once a true collapse is ecognized, the phone-ID and the coordinate will be sent to the server of administrative office via CDMA network. And theposition of emergency will be displayed on the GIS with the rescue center.

좌폐 대엽성 무기폐의 단순흉부 측면상 소견: 양측 상엽기관지간의 거리변화

신길현 대한영상의학회 1996 대한영상의학회지 Vol.34 No.6

Purpose : To evaluate the distance between both upper lobe bronchi on lateral radiographs and its change in left upper or lower lobe collapse. Materials and Methods : 144 true lateral radiographs were analyzed on which both upper lobe bronchi were clearly identified. They included 116 normal cases, 11 cases of left upper lobe collapse, 13 of left lower lobe collapse, and 4 cases of left lower lobe lobectomy. Line A was drawn parallel to the vertebral end plate through the upper margin of the left upper lobe bronchus. Line B was drawn parallel to line A through the upper margin of the right upper lobe bronchus. The shortest distance between line A and line B was measured as the distance between both upper lobe bronchi. Results : In normal cases, the mean value of the distance was 2.19cm $\pm$ S.D. 0.37cm on right and 2.16cm $\pm$ S.D. 0.40cm on left lateral radiographs ; these results were not significantly different(P=0.79). In cases of collapse, the mean value of the distance was 0.43cm $\pm$ S.D.0.99cm in upper lobe collapse and 3.56cm $\pm$ S.D. 0.72cm in lower lobe collapse, results which were significantly different from those of normal cases(P<0.01). In eight cases(73%) of left upper lobe collapse, the distance was less than 1cm and in 10 cases(77%) of left lower lobe collapse, the distance was more than 3cm. Conclusion : The distance between both upper lobe bronchi varies markedly in case of lobar collapse. A distance of less than 1cmsuggests collapse of the left upper lobe and a distance more than 3cm suggests collapse of the left lower lobe.

Vertical Building Collapse Triggered by Loss of All Columns in the Ground Story−Last Line of Defense

Nikolay Lalkovski,Uwe Starossek 한국강구조학회 2016 International Journal of Steel Structures Vol.16 No.2

In multi-story buildings, one of the worst collapse types in terms of structural damage and loss of life is the pancake-type collapse, where some or all floors end up lying on top of each other like the layers of a pancake, with the floor contents crushed between them. Mostly observed after strong earthquakes, such collapses are triggered by loss of some or all vertical load bearing elements in some story−often the ground story. Once this occurs, the building part above the lost vertical elements− still intact−starts gaining downward velocity until it meets resistance from below. The ensuing impact forces often lead to collapse progression ending in total collapse. However, there are some examples of buildings in which the columns of an entire story failed and the collapse remained arrested after the subsequent impact. Such cases were observed in the 1995 Kobe earthquake and in the 1985 Mexico City earthquake. There have also been some failed controlled demolition attempts in which the intended total vertical collapse did not occur after letting a building collide with the ground by explosive removal of the vertical load bearing elements in the lowest stories. In an attempt to determine the factors which play the main role in arresting vertical collapse once initiated at the ground level, this paper studies the behavior of vertically falling multi-story building structures impacting a rigid surface representing the ground. A simplified analytical model of the problem is presented. Depending on the structural properties, several possible energy dissipation mechanisms, and−in case the collapse cannot be arrested at impact−collapse modes, are identified.

Collapse Initiation and Mechanisms for a Generic Multi-storey Steel Frame Subjected to Uniform and Travelling Fires

Rackauskaite, Egle,Kotsovinos, Panagiotis,Lange, David,Rein, Guillermo Council on Tall Building and Urban Habitat Korea 2021 International journal of high-rise buildings Vol.10 No.4

To ensure that fire induced collapse of a building is prevented it is important to understand the sequence of events that can lead to this event. In this paper, the initiation of collapse mechanisms of generic a multi-storey steel frame subjected to vertical and horizontal travelling fires are analysed computationally by tracking the formation of plastic hinges in the frame and generation of fire induced loads. Both uniform and travelling fires are considered. In total 58 different cases are analysed using finite element software LS-DYNA. For the frame examined with a simple and generic structural arrangement and higher applied fire protection to the columns, the results indicate that collapse mechanisms for singe floor and multiple floor fires can be each split into two main groups. For single floor fires (taking place in the upper floors of the frame (Group S1)), collapse is initiated by the pull-in of external columns when heated beams in end bays go into catenary action. For single floor fires occurring on the lower floors(Group S2), failure is initiated (i.e. ultimate strain of the material is exceeded) after the local beam collapse. Failure in both groups for single floor fires is governed by the generation of high loads due to restrained thermal expansion and the loss of material strength. For multiple floor fires with a low number of fire floors (1 to 3) - Group M1, failure is dominated by the loss of material strength and collapse is mainly initiated by the pull-in of external columns. For the cases with a larger number of fire floors (5 to 10) - Group M2, failure is dominated by thermal expansion and collapse is mainly initiated by swaying of the frame to the side of fire origin. The results show that for the investigated frame initiation of collapse mechanisms are affected by the fire type, the number of fire floors, and the location of the fire floor. The findings of this study could be of use to designers of buildings when developing fire protection strategies for steel framed buildings where the potential for a multifloor fire exists.

Progressive Collapse Mechanism Analysis of Concrete-Filled Square Steel Tubular Column to Steel Beam Joint with Bolted–Welded Hybrid Connection

Wang Jing-Xuan,Yang Yong,Xian Wei,Li Qiu-Ying 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.5

When vertical load-bearing members of building structures are subjected to accidental loadings, such as an earthquake, fi re or explosion, the remaining structure chiefl y relies on the beam mechanism and catenary mechanism of the steel beam as the main resistance capacity, to prevent local or large-scale progressive collapse. This paper presents a three-dimensional fi nite element model of concrete-fi lled square steel tubular (CFST) column to steel beam joint with bolted–welded hybrid connection in a middle-column-removal scenario using ABAQUS software. The multi-scale modeling method was employed to calculate the collapse resistance and mechanism under vertical load. The vertical displacement and bearing capacity curve of the middle failure column was calculated and analyzed. The collapse mechanism and bearing capacity contribution of the steel beam tying in diff erent directions are also discussed. Results indicate that the failure mechanism of the process includes the beam mechanism, the translation mechanism, the catenary mechanism and the failure stage. After the short-span steel beam had been destroyed, the long-span steel beam continued to provide collapse resistance capacity. To improve progressive collapse resistance, the CFST column to steel beam joint with welded haunch is proposed in this paper. Comparing the anti-collapse bearing capacity and failure characteristics of the joint with the welded haunch and common joint indicates that the anti-collapse capacity of the joint with welded haunch can be improved, and the research results can be referenced for engineering progressive collapse design.

Design guides to resist progressive collapse for steel structures

M. Mirtaheri,M. Abbasi Zoghi 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.2

The progressive collapse phenomenon in structures has been interested by civil engineers and the building standards organizations. This is particularly true for the tall and special buildings ever since local collapse of the Ronan Point tower in UK in 1968. When initial or secondary defects of main load carrying elements, overloads or unpredicted loads occur in the structure, a local collapse may be arise that could be distributed through entire structure and cause global collapse. One is not able to prevent the reason of failure as well as the prevention of propagation of the collapse. Also, one is not able to predict the start point of collapse. Therefore we should generalize design guides to whole or the part of structure based on the risk analysis and use of load carrying elements removal scenario. There are some new guides and criteria for elements and connections to be designed to resist progressive collapse. In this paper, codes and recommendations by various researchers are presented, classified and compared for steel structures. Two current design methods are described in this paper and some retrofitting methods are summarized. Finally a steel building with special moment resistant frame is analyzed as a case study based on two standards guidelines. This includes consideration of codes recommendations. It is shown that progressive collapse potential of the building depends on the removal scenario selection and type of analysis. Different results are obtained based on two guidelines.

Surgical correction of nasal valve collapse

김주연,Nam Gi Yoon,권재환 대한미용의학회 2021 대한미용의학회지 Vol.5 No.2

Background: Nasal obstruction due to internal and/or external nasal valve collapse can be occurred sometimes. To overcome internal nasal valve obstruction, spreader grafts, butterfly grafts, flaring sutures and suspension sutures have been described to be effective. The correction of the external valve collapse can be done by alar batten, alar rim graft, and various other methods. Objective: We report successful results for the patients with severe nasal valve collapse during respiration using appropriate surgical techniques for individual causes. Methods: We undertook a retrospective study of 8 patients diagnosed with nasal valve collapse. Each patient underwent one or multiple procedures according to individual problems regard to their nasal obstruction. The visual analogue scale (VAS) and Nasal Obstruction Symptom Evaluation (NOSE) validated survey was used to measure a patient’s subjective postoperative change in nasal obstruction. Facial photography and video for estimating alar collapse were taken to compare the change of pre- and postoperative nasal breathing and shape. Results: Four out of eight patients had a static collapse of the nasal valves, while the other four had a dynamic collapse. The remaining six patients had no previous nasal trauma or surgical history. Each patient underwent surgeries such as alar batten graft, alar rim graft, and debulking operation according to their respective deformities. The endonasal and open approaches were used in five and three patients, respectively. After surgery, patient satisfaction (VAS) improved from 6.6 to 2.5 points, and the NOSE scale scores improved from 15.1 to 7.1 points. Conclusion: Nasal obstruction due to nasal valve collapse can be effectively treated with various surgical techniques. After a thorough examination and analysis, the underlying cause of the nasal obstruction should be analyzed, and one or multiple procedures should be chosen according to each individual problem to get good results.

Member capacity-based progressive collapse analysis of transmission towers under wind load

Yong-Quan Li,Yong Chen,Guohui Shen,Wenjuan Lou,Weijian Zhao,Hao Wang 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.33 No.4

The wind-induced collapse of transmission towers has raised many concerns. Progressive collapse analysis is recognized as a promising method for the assessment of the collapse-resistant capacity of the transmission tower. The finite element model of an actual transmission tower is firstly built for the analysis, in which the dynamic behavior of the member in failure is taken into account to be in accord with the actual tower collapse. The analysis considering the main design load cases is conducted in advance to determine the case under which the tower has the potential to collapse. The incremental dynamic analysis in association with the explicit time integration algorithm is employed to perform a progressive collapse analysis, where the wind loads are simulated by using the linear filtering method, and the developed failure criterion with axial force and bending moment involved is based on the stability bearing capacity of the members. It is found the tower collapse begins with the horizontal bracing member near the waist. Then, the adjacent members, including the leg members, fail sequentially, and the tower collapses eventually with a shear-type failure. The demand to capacity ratio (DCR) in terms of bearing capacity of the member is defined to quantify the structural behavior, the location of the member that has the potential to fail, and when the initial failure occurs are thereby identified. It is concluded that compared to the member capacity-based analysis, the ultimate strain-based analysis, which is most likely to be an inelastic dynamic analysis permitting a large deformation, may overestimate the bearing capacity of the structure in wind-induced collapse.