2003 — 2009 |
Nikitopoulos, Dimitris (co-PI) [⬀] Levitan, Marc Cai, Steve C.s. |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Investigation of Large Coastal Bridge Performance in Hurricane Environment @ Louisiana State University & Agricultural and Mechanical College
Investigation of Large Coastal Bridge Performance In Hurricane Environment, CMS proposal 0301696
PI: Cai, Louisiana State University
When a hurricane strikes the coast, the results are often devastating. Even as storm prediction and tracking technologies improve, providing greater warning times, our nation is still becoming ever more susceptible to the effects of hurricanes due to the massive population growth in the south and southeast along the hurricane coast from Texas to Florida to the Carolinas. As backbones of transportation lines, coastal bridges are extremely important in supporting evacuations. In addition to the general wind- induced problems, long-span large coastal bridges on hurricane evacuation routes face the threats from the combination of hurricane-induced winds, heavy traffic, and their interactions. The objectives of the proposed study are: (1) to study the performance of large coastal bridges under the action of strong winds as well as heavy traffic. This situation happens in a scenario of hurricane evacuation; (2) to investigate the effect of temporary mass dampers in ensuring bridge safety and/or reducing bridge vibration. The temporary mass dampers can conveniently be driven on the bridge when needed and be removed otherwise; and (3) to advance the state-of-the-art of aerodynamic analysis of large bridges under strong winds.
In a typical aerodynamic analysis of long-span bridges, no traffic load is considered by assuming that bridges will be closed to traffic at high wind speeds. Therefore, bridges have been tested in the wind tunnel or analyzed numerically based on the pure bridge section without vehicles on it. However, during a hurricane evacuation, the bridges may be occupied by slowly moving traffic. On one hand, vehicles affect the modal characteristics and section shape of the bridge, which affects the aerodynamic behavior. On the other hand, the same vehicles may act like mass dampers that may help damp out some vibrations. The total effects of the traffic on bridge performance and also bridge vibrations on vehicles are not clear and no studies have been reported. While it is generally assumed (but still controversial) that turbulence helps enhance bridge flutter velocity, the effects of hurricane-induced high turbulence on bridge stability haven't been adequately studied. These issues need to be addressed to ensure the safety of both bridge and vehicles during hurricanes and evacuations. While the developed procedures are intended for general coastal bridges, the Luling Bridge near New Orleans will be used as the primary subject of study. Both wind tunnel testing and numerical simulations will be conducted. The bridge performance will be investigated by arranging different traffic patterns to find the worst case for safety assurance, and find the optimal pattern that may be utilized for hazard mitigation (e.g., closing certain lanes). Another alternative is to develop a movable TMD system that can be driven on the bridges to act as a temporary vibration damper. The research activities and results will be incorporated into the new education curriculum - Hurricane Engineering developed at LSU with the NSF fund.
The proposed study is to address the issue of how large coastal bridges perform in hurricanes under evacuation conditions. The answer is very important since thousands of lives potentially hinge on the decision of when to close the evacuation routes too soon and people may be trapped in coastal areas subject to storm surge, too late and people may be on the bridge under unsafe conditions. The educational activities include high school outreaching, minority students recruiting, and technical information dissemination. These activities will promote minority participation, affect high school students career path, and foster future engineers to develop more systematical strategies in dealing with the most destructive hurricane hazards for years to come. International collaboration with Tongji University, China, will not only utilize the second largest boundary layer wind tunnel facility in the world, but will also foster further research and collaboration, increase the visibility of hurricane engineering in both countries, and combine the resources to deal with the worldwide engineering challenge of the 21st century . mitigating hurricane hazards. To achieve the research objectives, a unique team of researchers is formed. This team consists of Dr. Cai (PI) who has extensive expertise in wind vibration analyses, Dr. Levitan (co-PI), director of the LSU Hurricane Center and an expert in wind loading, Dr. Nikitopoulos (co-PI) is the Director of Wind Tunnel Laboratory with expertise in fluid dynamics and wind tunnel simulation.
|
0.936 |
2005 — 2006 |
Okeil, Ayman Levitan, Marc Van Heerden, Ivor Cai, Steve C.s. |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Sger: Impacts of Hurricane Katrina Storm Surge On the Human and Built Environments @ Louisiana State University & Agricultural and Mechanical College
CMS-0553187
Abstract:
Hurricane Katrina is likely to go into the history books as the most catastrophic windstorm to strike the United States in recorded history. It offers an unprecedented opportunity to collect perishable data that will assist emergency planners and bridge officials in facing similar disasters in the future. The American Association for Wind Engineering (AAWE) is coordinating a documentation effort from research institutions with wind- and surge-related expertise across the United States in an effort to collect perishable data by acknowledged experts. Currently teams from Louisiana, Texas, Florida, South Carolina, Colorado, Iowa and New York are participating in this AAWE coordinated effort. This award supports the data collection effort conducted by a team of faculty and graduate students from Louisiana State University (LSU). The focus of LSU's effort will be on two of the most catastrophic and unique aspects of this storm: (1) the terrible loss of life due to storm surge, and (2) the damage and destruction of numerous short- and medium-span bridges due to surge and waves. The first task concerns collection of perishable data about flood casualties. Previous research has documented a strong relationship between fatality rates and depth of flooding, but the effects of other variables are less well understood. Detailed data will be collected about the conditions surrounding fatalities, including: (1) location (GPS coordinates); (2) depth of water; (3) where the fatality occurred, e.g., building, car, in open space; (4) building type, elevation, number of stories, and damage sustained (if fatality occurred in a building); and (5) demographic data. The collected data is vital to flood fatality model development and validation. Such models are valuable to emergency managers and disaster public health officials to aid in disaster planning, design of mitigation measures, search and rescue operations, and recovery operations. The second task in this award will be concerned with collecting bridge damage data. It will focus on short- and medium-span bridges that have performed poorly during Hurricane Katrina and last year during Hurricane Ivan. Many unanchored, or poorly anchored, simply supported spans were lost due to unseating. These failures will be surveyed to collect data on: (1) failure modes (e.g., anchor failure, pile-to-cap connection, pile failure, other modes); (2) scour; (3) corrosion; (4) high water mark elevations; and (5) bridge railing type (solid/open). The collected bridge data will be used to develop design solutions for new construction of coastal bridges and rehabilitation of existing coastal bridges to avoid the occurrence of similar tragedies. Collected data from both tasks will be assembled into a report along with results from other AAWE partner investigations, which will be the subject of a one-day workshop held in Washington, DC, with financial and administrative support from the American Society of Civil Engineers' Structural Engineering Institute. This forum will transfer critical knowledge on infrastructure performance during Hurricane Katrina and provide an informed input to government and industry decision-making bodies.
|
0.936 |
2009 — 2015 |
Cai, Steve C.s. |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Investigation and Damage Mitigation of Low-Lying Coastal Bridges Under Hurricane-Induced Wind and Wave Actions @ Louisiana State University & Agricultural and Mechanical College
Hurricane wind, surge, and wave induced loads on low lying bridges in coastal areas are not well understood. Several coastal bridges were damaged in Hurricanes Ivan and Katrina. The objective of this study is to characterize the wind, surge, and wave loads on bridge decks, and to develop mitigation countermeasures for coastal bridges. The specific activities include (1) developing an experimental method to simulate wind, surge, and wave loading effects on bridge decks; (2) establishing a numerical simulation methodology to predict the bridge performance for the defined wind, surge, and wave loads; and (3) investigating effective and economical hazard mitigation countermeasures to reduce the impact of hurricanes on coastal bridge structures. This study will focus on short and medium span low lying costal bridge structures that are vulnerable to wind, surge, and wave actions. The mitigation strategies include both aerodynamic streamlining of bridge decks and mechanical strengthening of the connections between the bridge superstructure and substructure, considering a balanced performance between the superstructure and substructure.
If successful, the research will lead to better definition of design load and improved understanding about the performance of coastal bridges, and provide essential technical data for the design of these structures and analytical tools and methodologies for safety assessments of coastal bridges in a hurricane environment. This is expected to lead to better bridge designs with reduced damage during a hurricane induced extreme wind environment. The attractive demonstrations and education tools will be prepared for outreach activities and to increase the public awareness of hurricane structural engineering. The design tools incorporating the results of this research will be developed for practitioners to design safer and more economical coastal bridge structures. The project will also train graduate students through their involvement in the project research activities.
|
0.936 |
2012 — 2017 |
Cai, Steve C.s. |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Collaborative Research: Progressive Failure Studies of Residential Houses Towards Performance Based Hurricane Engineering @ Louisiana State University & Agricultural and Mechanical College
Hurricane-induced wind and rain can cause catastrophic damages to homes. This collaborative proposal pursues research in progressive damage to single family residential structures under hurricane winds. The research will focus on propagation of internal pressures, influence of wind-driven rain on pressures, and development of nonlinear analysis for the complex structures of wood residential buildings. For analytical work proper orthogonal decomposition and database-assisted-damage-prediction techniques will be used. The wind pressure/load data will be obtained from wind tunnel tests conducted at Louisiana State University at the scale of 1:50; tests conducted at Harbin Institute of Technology (China) at the scale of 1:10, and nearly full-scale tests conducted at Florida International University's 12-fan Wall of Wind facility. The tests will provide opportunity to study impact of wind loads on damage causing mechanism and development of fragility curves. The research will allow understanding of progressive damage propagation and component failure mechanism. New knowledge gained will have the potential of developing retrofitting procedures to reduce the damage. Collaboration with foreign partner will enhance research capability. Students working on the project will gain experience in wind effects on structures and in hurricane engineering.
The proposed research addresses hurricane effects on residential buildings that are one of the most vulnerable and complex structures. While a database-assisted-damage-prediction that directly uses time variant wind pressures as loading inputs will make the progressive failure analysis possible, using the proper orthogonal decomposition will greatly reduce the computational cost. The analytical procedure will follow the procedures developed for earthquake engineering. Nonlinear procedures will be developed for response of residential structures to wind loads. The research outcomes are (1) knowledge advancement on hurricane impacts on and interactions with residential constructions, leading to more realistic and accurate loading inputs for damage predictions and structural designs/mitigations, (2) enhancement of hurricane resiliency of new and existing structures by understanding the load paths and failure modes, and (3) development of mitigation guidelines to retrofit the existing housing stock. Following the path of earthquake engineering, the research methodology will help establish a rational performance-based design and mitigation approach for wind engineering. This will eventually reduce losses due to hurricane and strong wind-related events.
|
0.936 |
2014 — 2016 |
Friedland, Carol Okeil, Ayman Aly, Aly Mousaad Cai, Steve C.s. Barbato, Michele (co-PI) [⬀] |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Planning Grant: I/Ucrc For Windstorm Hazard Mitigation @ Louisiana State University & Agricultural and Mechanical College
The planned I/UCRC for Windstorm Hazard Mitigation intends to undertake functions at the interface between basic and applied research and between private and public interests. Working with its members, the Center will focus on seeking solutions to real world problems encountered by industry members and improve their performance and competitiveness; enhancing government agencies and NGOs capabilities to prepare for and respond to future windstorms; transferring findings from federally sponsored research to products and intellectual properties that benefit researchers, university, and industry; and facilitating collaboration between Center members by developing long-term strategies for enhancing community resiliency to wind and other hazards.
The planned center aims to protect homeowners, businesses, and communities through collaborative research in windstorm mitigation and the implementation of innovations will enhance the Nation's resiliency to future disasters. Integrated in the project are several initiatives aimed at increasing diversity and collectively they contribute to the development of a more diverse workforce and business environment. Meanwhile, the planning activities provide a unique opportunity for students to interact with the industry, improve their communication skills, and enhance their employment potentials. The project helps develop students with strong problem solving, marketable capabilities. The project also helps train Center faculty on how to work with the industry.
|
0.936 |