Dr. Islam and his team of graduate students have been involved in various cutting-edge research projects. His research was supported by state and federal agencies. In the Summer of 2013 and 2014, Dr. Islam received the NASA Glenn Summer Faculty Fellowship and performed research on health monitoring of military aircrafts at the NASA Glenn Research Center, Cleveland, Ohio. He also received the first ODOT grant to YSU to perform research on health monitoring of bridges using wireless sensor networks.
Following is a list of research projects Dr. Islam has been involved:
Damage Detection using Vibration Response
Vibration response of damaged and undamaged samples is being analyzed to develop algorithms to identify location and severity of damage.
Health Monitoring of Bridges using Wireless Sensor Networks
The hypothesis is based on the assumption that the dynamic response is a sensitive and important indicator of the physical integrity and condition of a structure. Two wireless sensor networks (WSNs) were deployed for the collection of real-time acceleration response of a 25-year old PSBB bridge under trucks with variable loads and speeds. The acceleration response of the bridge at its newest condition was collected from the dynamic simulations of its full-scale finite element (FE) models mimicking field conditions. The analyses and comparisons of the bridge dynamic response between the newest and the current bridge interestingly indicate a 37% reduction in its fundamental frequency over its 25 years of service life. This reduction has been correlated to the current condition rating of the bridge to develop application software for quick and efficient condition assessment of a PSBB bridge. The application software can instantly estimate overall bridge condition rating when used with the WSN deployed on a PSBB bridge under vehicular loads. The research outcome and the software is expected to provide a cost-effective solution for assessing the overall condition of a PSBB bridge, which helps to reduce maintenance costs and provide technologically improved bridge maintenance service.
This research describes a method for load rating of prestressed box beam (PSBB) bridges based on their dynamic response collected using wireless sensor networks (WSNs).The hypothesis is based on the assumption that the health of a bridge is associated with its vibration signatures under vehicular loads. Two WSNs were deployed on a 25-year old PSBB bridge under trucks with variable loads and speeds for collecting real-time dynamic response at the current condition. Dynamic simulations of three dimensional finite element models of a bridge were performed to acquire its dynamic response under vehicular loads at its newest condition right after construction. The bridge model was validated by field testing and numerical analysis. Fast Fourier Transform and peak-picking algorithms were used to find maximum peak amplitudes and their corresponding frequencies. This information and the necessary bridge geometric parameters were used to calculate the in-service stiffness of the bridge in order to develop application software for load rating of bridges. The application software can instantly calculate the load rating of a PSBB bridge by collecting its real time dynamic response under vehicular loads using WSNs. The research outcome and the software will help reduce bridge maintenance costs and will increase public safety.
Load Rating of Bridges without Plans
In the United States, there is a large number of reinforced concrete flat slab bridges, which were constructed during 1900’s and are still in service. The state Departments of Transportation (DOTs) do not have necessary information of design details, and properties of materials used during the construction of those old flat slab bridges. Those old bridges are not designed to support the current traffic. Nowadays, the visual inspection techniques followed by AASHTO guidelines are used for the evaluation of current load carrying capacity of concrete flat slab bridges. The usual method would overestimate or underestimate the load bearing capacity, which may not represent the actual capacity. For a simple non-destructive test, Profoscope and Schmidt hammer were used to run the test in the field. By using field data, three dimensional finite element analysis of a flat slab bridge was performed in ANSYS to determine deflection at the mid-point of a concrete flat slab bridge under a truck. So, the truck load position, which would produce the maximum moment at mid span, was used as a critical load position. The load was increased up to a point that produces the deflection close to the maximum allowable value. The load corresponding to the maximum allowable deflection on the existing bridge is used to calculate the rating factor of the bridge. The Ohio legal load vehicle of gross weight 30 of kips having the truck load designation of OH-2F1 is considered for this research. The rating factor is determined as the ratio of truckload that produce the maximum allowable midpoint deflection to the original designated truck load. The research outcome will provide guidelines to evaluate the load rating factor of existing flat slab bridges without plans.
Corrosion in Bridge Substructure Reinforcement
A pedestrian bridge linking Moser Hall and Cushwa Hall at Youngstown State University (YSU), Youngstown, Ohio, was built almost 40 years ago. Three hammerhead pier caps supporting the bridge deck have experienced severe corrosion at the bottom. This corrosion has led to spalling of concrete at multiple locations in all three pier caps and thereby exposed the rebars to open air facilitating more corrosion. At some locations, corroded steel bars are clearly visible at spalled locations and through larger cracks. Some patches of repair are seen on the site, but the corrosion problem still continues to degrade the substructure.
An investigative study was undertaken to identify the causes of corrosion in these substructures and to propose a viable remedy to this problem. The replacement of the pier caps was not a preferable option, unless no remedial option is available. The researchers studied the construction drawings available at the time of this study, and some important documents containing information on material strength and clear cover were lost in time. This situation created a significant challenge in performing structural analysis of the existing substructure. Therefore, Schmidt Hammer and Profoscope were used to determine the approximate concrete strength, rebar location and clear cover.
Reviews of previous research suggest that substructure corrosion can likely be chloride-induced or carbonation-induced. Chloride-induced corrosion is more common in structures subject to deicing salts or saline water. Being a pedestrian bridge between two educational buildings with no access to deicing salts or saline water, chloride-induced phenomenon was ruled out as an active cause of corrosion in the substructure. Ingression of aggressive ions through cracks due to physical deterioration was ruled out as well. No signs of crack due to sulfate attack, alkali-silica reaction, freezing and thawing action, shrinkage or support settlement were seen on the structure. Although carbonation-induced corrosion is a slower process in a dry environment and mostly occurs in older structures, it was predicted that the corrosion in those pier caps was due to carbonation of concrete. Free carbon dioxide in the atmosphere reacts with alkaline hydroxides in the concrete to form carbonic acid. Carbonic acid, unlike other acids, does not attack the concrete paste but it lowers the pH value. Carbonation reaction takes place on the outer surface of concrete and gradually penetrates into the concrete cover resulting in a low pH concrete cover.
A full-scale structural analysis revealed no major reduction in strength of the pier caps. Visual inspections and analytical study were conducted to ensure no major deficiency exists in the corroded concrete and steel reinforcement. After considering various repair methods, patching with low-slump dense concrete coupled with hydrophobic coating is suggested as a remedial measure to protect the substructure from further deterioration.
CFRP Laminates in Shear Strengthening of Concrete Beams
This paper presents the results of an experimental study that investigated the shear strength contribution of carbon fiber reinforced polymer (CFRP) bars attached with concrete beams using a near surface mounted (NSM) technique. In this research, four concrete beams were cast with regular steel reinforcement in flexure. The control beam had typical shear steel and the other three beams were strengthened in shear with CFRP bars. Strain gauges were attached with the shear reinforcement of all four beams at various shear critical locations. Strains during loading to failure of the beams were recorded using a data acquisition system. The performance of the NSM technique was found to be very effective with no occurrence of delamination, debonding or fracture of FRP. Effective strains in the NSM CFRP bars were determined through analyzing the collected strain data. A new formula to calculate the nominal shear strength provided by NSM CFRP bars has also been proposed.
Performance of AASHTO Girder Bridges uunder Blast Loads
AASHTO has specified probability based design methodology and load factors for designing bridge piers against ship impact and vehicular collision. Currently, no specific AASHTO design guideline exists for bridges against blast loading. Structural engineering methods to protect infrastructure systems from terrorist attacks are required. This study investigated the most common types of concrete bridges on the interstate highways. A 2-span 2-lane bridge with Type III AASHTO girders was used for modeling. AASHTO Load and Resistance Factor Design methods were used for bridge design. The girders, pier caps and columns loading were analyzed for typical blast loading. The model bridge failed under typical blast loads applied over and underneath the bridge. The research findings show that typical AASHTO girder bridges are unable to resist typical blast loads.
Post-Storm Model for the Reconstruction of Habitable Coastal Structures
Florida, which is one of the most storm-prone states in the United States, experienced several major hurricanes such as Andrew, Georges, Earl, and Opal in the last decade. The tremendous population growth in the Florida coastal region has increased the volume of coastal residential construction, enhancing the possibility of storm damage. After a storm is over, the Florida Department of Environmental Protection and local government personnel identify the amount of damage sustained by structures and follow the Federal Emergency Management Agency’s “50% substantial damage rule” to determine the repairability of structures on a case-by-case basis. This process requires a substantial amount of personnel time and effort, often delaying the permitting process. Currently, there is no convenient decision-making tool to quickly assess damaged structures after a storm and place them in “repair” or “rebuild” categories. In this study, decision matrices were developed based on the current construction cost data, identified damage levels, factors affecting decision making, and current requirements of Florida Statutes, Chapter 161, the Florida Department of Natural Resources, the Florida Department of Community Affairs, and the Florida Department of Environmental Protection. Decision-making software was developed that can be used in the field to quickly classify structures for rebuildability and to provide approximate repair costs.