Application of tuned liquid dampers in controlling the torsional vibration of high rise buildings

Ross, Andrew S.,El Damatty, Ashraf A.,El Ansary, Ayman M. Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.21 No.5

Excessive motions in buildings cause occupants to become uncomfortable and nervous. This is particularly detrimental to the tenants and ultimately the owner of the building, with respect to financial considerations. Serviceability issues, such as excessive accelerations and inter-story drifts, are more prevalent today due to advancements in the structural systems, strength of materials, and design practices. These factors allow buildings to be taller, lighter, and more flexible, thereby exacerbating the impact of dynamic responses. There is a growing need for innovative and effective techniques to reduce the serviceability responses of these tall buildings. The current study considers a case study of a real building to show the effectiveness and robustness of the TLD in reducing the coupled lateral-torsional motion of this high-rise building under wind loading. Three unique multi-modal TLD systems are designed specifically to mitigate the torsional response of the building. A procedure is developed to analyze a structure-TLD system using High Frequency Force Balance (HFFB) test data from the Boundary Layer Wind Tunnel Laboratory (BLWTL) at the University of Western Ontario. The effectiveness of the unique TLD systems is investigated. In addition, a parametric study is conducted to determine the robustness of the systems in reducing the serviceability responses. Three practical parameters are varied to investigate the robustness of the TLD system: the height of water inside the tanks, the amplitude modification factor, and the structural modal frequencies.

Application of tuned liquid dampers in controlling the torsional vibration of high rise buildings

Andrew S. Ross,Ashraf A. El Damatty,Ayman M. El Ansary 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.21 No.5

Excessive motions in buildings cause occupants to become uncomfortable and nervous. This is particularly detrimental to the tenants and ultimately the owner of the building, with respect to financial considerations. Serviceability issues, such as excessive accelerations and inter-story drifts, are more prevalent today due to advancements in the structural systems, strength of materials, and design practices. These factors allow buildings to be taller, lighter, and more flexible, thereby exacerbating the impact of dynamic responses. There is a growing need for innovative and effective techniques to reduce the serviceability responses of these tall buildings. The current study considers a case study of a real building to show the effectiveness and robustness of the TLD in reducing the coupled lateral-torsional motion of this high-rise building under wind loading. Three unique multi-modal TLD systems are designed specifically to mitigate the torsional response of the building. A procedure is developed to analyze a structure-TLD system using High Frequency Force Balance (HFFB) test data from the Boundary Layer Wind Tunnel Laboratory (BLWTL) at the University of Western Ontario. The effectiveness of the unique TLD systems is investigated. In addition, a parametric study is conducted to determine the robustness of the systems in reducing the serviceability responses. Three practical parameters are varied to investigate the robustness of the TLD system: the height of water inside the tanks, the amplitude modification factor, and the structural modal frequencies.

Incidence and Significance of Biliary Stricture in Chronic Pancreatitis Patients Undergoing Extracorporeal Shock Wave Lithotripsy for Obstructing Pancreatic Duct Stones

( Jong Jin Hyun ),( Shayan S. Irani ),( Andrew S. Ross ),( Michael C. Larsen ),( Michael Gluck ),( Richard A. Kozarek ) 대한소화기학회 2021 Gut and Liver Vol.15 No.1

Background/Aims: This study assessed the significance of biliary stricture in symptomatic chronic pancreatitis patients requiring extracorporeal shock wave lithotripsy (ESWL) and endoscopic retrograde cholangiopancreatography (ERCP) to remove obstructing pancreatic calculi. Methods: A total of 97 patients underwent ESWL followed by ERCP to remove pancreatic calculi between October 2014 and October 2017 at Virginia Mason Medical Center. Significant biliary stricture (SBS) was defined as a stricture with upstream dilation on computed tomography scan or magnetic resonance cholangiopancreatography scans accompanied by cholestasis and/or cholangitis. SBS was initially managed by either a plastic stent or fully covered self-expandable metallic stent (fcSEMS). If the stricture did not resolve, the stent was replaced with either multiple plastic stents or another fcSEMS. Data were collected by retrospectively reviewing the medical records. Results: Biliary strictures were noted in approximately one-third of patients (34/97, 35%) undergoing ESWL for pancreatic calculi. Approximately one-third of the biliary strictures (11/34, 32%) were SBS. Pseudocysts were more frequently found in those with SBS (36% vs 8%, p=0.02), and all pseudocysts in the SBS group were located in the pancreatic head. The initial stricture resolution rates with fcSEMSs and plastic prostheses were 75% and 29%, respectively. The overall success rate for stricture resolution was 73% (8/11), and the recurrence rate after initial stricture resolution was 25% (2/8). Conclusions: Although periductal fibrosis is the main mechanism underlying biliary stricture development in chronic pancreatitis, inflammation induced by obstructing pancreatic calculi, including pseudocysts, is an important contributing factor to SBS formation during the acute phase. (Gut Liver 2021;15:128-134)

Double Balloon Enteroscopy in a North American Setting: A Large Single Center 5-year Experience

( Gulseren Seven ),( Richard A. Kozarek ),( Andrew Ross ),( Shayan Irani ),( Michael Gluck ),( Drew Schembre ),( Johannes Koch ),( S. Ian Gan ) 대한장연구학회 2013 Intestinal Research Vol.11 No.1

Background/Aims: Double balloon enteroscopy (DBE) allows both diagnosis and therapeutic maneuvers in the small bowel. Its use was pioneered in Europe and Asia but there remains a relative paucity of literature from North America. Our aim in this study was to determine diagnostic and therapeutic yield in a North American setting. Methods: A five-year retrospective analysis of all patients undergoing DBE at a single tertiary care North American hospital was performed. Results: Four-hundred fifty-seven procedures, 265 anterograde and 192 retrograde, were performed on 335 patients. The most common indications were obscure gastrointestinal bleeding, small bowel obstruction, and suspected masses and mucosal abnormalities. Total enteroscopy was achieved in 19 of the 89 patients who had both anterograde and retrograde procedures. Overall diagnostic yield in the determination of cause of symptoms or previous imaging was 52%. The most common causes of obscure bleeding were small bowel ulcers (10%), vascular lesions (25%) and neoplasms (10%). The most common causes of small bowel obstruction were strictures, some of which underwent dilation. Other therapeutic interventions included polypectomy, retrieval of retained capsules, stent retrievals and percutaneous enteral jejunostomy tube placement. Overall complication rates were very low (0.6%) and included medication reaction (n=1), scope dysfunction (n=1) and perforation (n=1). Conclusions: DBE can be performed safely and with good diagnostic yield in a single referral center in North America. (Intest Res 2013;11:34-40)

Outcomes of Infected versus Symptomatic Sterile Walled-Off Pancreatic Necrosis Treated with a Minimally Invasive Therapy

( Jong Jin Hyun ),( Nadav Sahar ),( Anand Singla ),( Andrew S Ross ),( Shayan S Irani ),( S Ian Gan ),( Michael C Larsen ),( Richard A Kozare ),( Michael Gluck ) 대한소화기학회 2019 Gut and Liver Vol.13 No.2

Background/Aims: Acute pancreatitis complicated by walled-off necrosis (WON) is associated with high morbidity and mortality, and if infected, typically necessitates intervention. Clinical outcomes of infected WON have been described as poorer than those of symptomatic sterile WON. With the evolution of minimally invasive therapy, we sought to compare outcomes of infected to symptomatic sterile WON. Methods: We performed a retrospective cohort study examining patients who were undergoing dual-modality drainage as minimally invasive therapy for WON at a high-volume tertiary pancreatic center. The main outcome measures included mortality with a drain in place, length of hospital stay, admission to intensive care unit, and development of pancreatic fistulae. Results: Of the 211 patients in our analysis, 98 had infected WON. The overall mortality rate was 2.4%. Patients with infected WON trended toward higher mortality although not statistically significant (4.1% vs 0.9%, p=0.19). Patients with infected WON had longer length of hospitalization (29.8 days vs 17.3 days, p<0.01), and developed more spontaneous pancreatic fistulae (23.5% vs 7.8%, p<0.01). Multivariate analysis showed that infected WON was associated with higher odds of spontaneous pancreatic fistula formation (odds ratio, 2.65; 95% confidence interval, 1.20 to 5.85). Conclusions: This study confirms that infected WON has worse outcomes than sterile WON but also demonstrates that WON, once considered a significant cause of death, can be treated with good outcomes using minimally invasive therapy. (Gut Liver 2019;13:215-222)

A Mid-IR Selected Changing-look Quasar and Physical Scenarios for Abrupt AGN Fading

Stern, Daniel,McKernan, Barry,Graham, Matthew J.,Ford, K. E. S.,Ross, Nicholas P.,Meisner, Aaron M.,Assef, Roberto J.,Baloković,, Mislav,Brightman, Murray,Dey, Arjun,Drake, Andrew,Djorgovski, S. American Astronomical Society 2018 The Astrophysical journal Vol.864 No.1