Search

Ultrahigh-performance concrete (UHPC) is a new class of concrete with far superior mechanical and durability properties compared to conventional concrete. Recently, its use has been growing in both civil and architectural applications, especially in the precast industry. This paper presents the application of UHPC to the production of precast concrete sandwich wall panels commonly used in Northern regions and known as insulated wall panels. Using UHPC in the panel wythes allows for a significant reduction in wythe thickness and, consequently, panel weight, in addition to the elimination of longitudinal and transverse reinforcement, which simplifies production. In this study, four 2.44 m × 1.22 m × 203 mm composite UHPC sandwich wall panels were fabricated by a local precast producer using a nonproprietary UHPC mixture. Panels were tested in flexure to evaluate the degree of composite action when wythe thickness of 32 mm and glass fiber–reinforced polymer (GFRP) shear connectors are used. These panels do not contain any conventional rebars or prestressing strands as they are fully dependent on the presence of random steel fibers in UHPC to provide the tensile resistance. Test results have shown that this new system can achieve a flexural capacity of 92% of that of a fully composite panel while being more flexible and lighter than conventional concrete sandwich wall panels. The composite UHPC sandwich wall panels have a great potential in architectural and structural applications, such as exterior load-bearing walls and cladding panels. This paper investigates the structural behavior of a new system of sandwich wall panels utilizing reduced wythe thicknesses made of ultrahigh-performance concrete (UHPC) and achieving high degree of composite action. Structural performance and production efficiency of this system can have significant impacts on energy-efficient building construction. This new system can achieve a degree of composite action up to 92%, which makes the design efficient for large cladding panels and load bearing exterior walls. A design example is presented comparing a conventional concrete sandwich wall panel made of two 76-mm-thick concrete wythes and 51-mm-thick insulation to a UHPC panel with the same overall thickness of 203 mm but with 32-mm-thick concrete wythes and 140-mm-thick insulation. Both panels are 2.44-m wide and 9.14-m tall and subjected to unfactored wind pressure of 1.44-kPa, which is considerably higher than the typical values used in wall design for midwest states. The significant increase in the insulation thickness of the UHPC panel results in significantly less weight and higher R-value than those of the conventional concrete panel. In addition, the UHPC panel does not have either longitudinal prestressing strands or transverse reinforcing bars, which simplifies panel fabrication. [ABSTRACT FROM AUTHOR]

Low-impact development practices (LIDs) have been used to reduce the impacts of flash floods in Brazil. However, there is a lack of investigations on their construction costs concerning the effects on the mitigation of flash floods. This paper addresses the construction costs and the runoff reduction by using seven scenarios of LIDs for a 32-km2 basin in the Midwest Brazil region. The LIDs considered were permeable pavement (PP), rainwater harvesting (RWH), and infiltration trenches (IT). The first three LID scenarios considered PP, RWH, and IT techniques, respectively, and the other four used different combinations of the three LIDs. Scenario 3 showed a decrease of 15% in the runoff, achieved at a lower cost using only IT. This result corresponds to a 2.6% runoff reduction per $1 million spent. These analyses may help in the identification of the balance between benefit and cost by local stakeholders for the use of LIDs. [ABSTRACT FROM AUTHOR]

Keeping bridges in good condition during their service lives continues to be a challenge. Additionally, the condition assessment of concrete bridge decks is complicated as it is influenced by several factors. Environmental factors are among the main reasons behind the deterioration of concrete bridge decks. Therefore, studying the impact of environmental factors is a significant part of the condition assessment of concrete bridge decks. In this study, the condition ratings of concrete bridge decks were used to investigate whether there is a universal model that can represent the impact of environmental factors on deterioration rates of concrete bridge decks in the US. The results showed that the best deterioration model varied from one state to another, and there was no universal statistical prediction model that can be developed for all states. Additionally, it was observed that the Weibull distribution method was the best model for the Southern, Southeast, and Western Regions, while the lognormal method was the best for the Northeast, Midwest, and High Plain regions. Furthermore, it was concluded that environmental factors have a significant impact on the deterioration of concrete bridge decks. This paper will help transportation network agencies better plan for the maintenance, rehabilitation, and reconstruction actions and funding. Additionally, it can help in establishing optimal guidelines to maintain bridges based on their climatic regions. [ABSTRACT FROM AUTHOR]

Reliability-based design of infrastructure requires the probabilistic assessment of jointly occurring natural hazards. As infrastructure design practices evolve, it is important that multiple hazards be considered--for example, wind and storm surge in a hurricane, an earthquake generating a tsunami, or strong winds and high temperatures leading to wildfires. These jointly occurring hazards in some cases can be more devastating than a single hazard. This paper describes the assessment of two jointly occurring hazards: wind and ice. For locations in the United States, wind and ice [e.g., freezing rain (FR)] are hazards whose properties are of interest for the design of transmission lines and other energy infrastructure (e.g., wind turbines). Using archived meteorological data from measurement stations in the Midwest, occurrences of icing conditions and the wind speeds that accompany them were identified and input into a simple ice accretion model. Observations from wind speed and ice thickness were fit to probability distributions, and simulations using these distributions were constructed. These simulations were then compared with the observed data and with existing prescribed treatments of these two hazards in design loading guidelines, such as ASCE 7. It is shown that the ASCE 7 method is overly conservative when considering joint hazards. [ABSTRACT FROM AUTHOR]

The major water quality impairment in the midwest United States is sediment eroded from agricultural lands. Yet, few understand the spatial and temporal variability of erosion, or soil erosion dynamics, in relation to precipitation, topography, land management, and severe events. The objectives of this paper are to (1) develop a methodology for estimating long-term spatial soil erosion and water runoff losses and (2) explore issues in applying an established physical-based process model, Water Erosion Prediction Project (WEPP), to a large area by establishing a prototype system for the state of Iowa. This study for the first time provides a comparison of the model predictions against long-term measurements of the sediment delivery ratio (SDR) in the South Amana Catchment of the Clear Creek Watershed (CCW), a heavily instrumented watershed that is roughly 10 times the maximum WEPP fold size. To further examine the performance of WEPP in a semihumid environment, such as the CCW, where runoff and raindrop impact to erosion may be significant, the SDR was plotted as a function of the runoff coefficient, defined as the runoff/rainfall ratio. In addition, the WEPP predictions are compared against the statistical relation of SDR vs. runoff coefficient developed by Piest et al. in 1975) for watersheds in Iowa. It is shown that WEPP follows the trend shown by Piest et al. quite closely and performs well for continuous simulations extended up to 300 years. [ABSTRACT FROM AUTHOR]

The wind moment frame (WMF) method has been and continues to be widely utilized in the central and eastern United States, resulting in a very large population of structures having been designed without a rigorous analysis with respect to lateral loads. The primary objectives of this paper are to determine whether moment-resisting frames designed by the WMF method are adequate to handle the increased demand on lateral resistance made by modern seismic codes, and to evaluate and compare the seismic performance of existing and new moment-resisting steel frames with partially restrained (PR) connections. Three prototype frames were designed and analyzed utilizing synthetic ground motions for the Mid-America region. The seismic performance of these PR frames was evaluated in accordance with FEMA 273/356 criteria. In addition, studies were conducted on the confidence level of the performance results to take into account the uncertainties and randomness inevitably involved. This analysis and evaluation found that all PR frames designed in this study satisfied the selected performance objective with 99% confidence level for the global performance limit. Thus, the seismic performance of the PR frames in the Mid-America region will be satisfactory even under large ground motions. [ABSTRACT FROM AUTHOR]

Two surveys helped gather information on the state transportation agency's snow fence programs and private landowner's perspectives on snow fences. The first survey collected responses from state transportation agencies in the Midwest of the United States and the landowner survey was distributed to Illinois landowners via the online publication Farm Week. The agency survey showed that the vast majority of respondents planned to expand or maintain their snow fence programs and relied on the feedback and experience of road maintenance personnel to identify snow drifting problem segments. Key concerns identified by the landowner survey include the implementation and maintenance of snow fences by state agencies, proper and timely compensation, making long-term commitments with the state, and soil moisture in the snow storage area. It also showed that the number of acres and unit price of crops were the most important factors to include in a payment structure. Landowners' participation in snow fence programs could be encouraged by providing more flexible contracts, offering adjustable payment structures, adding incentives to engage landowners in installation and maintenance, and providing an awareness program. [ABSTRACT FROM AUTHOR]

A large portion of existing building stock is comprised of load-bearing masonry buildings, particularly in the Midwest and on the East Coast, though such buildings are distributed across the US. Most of them have uninsulated walls or suffer from insufficient thermal insulation materials. These buildings are inseparable parts of the cultural, social, and economic characteristics of their cities. Due to heritage and preservation concerns, zoning, and space restrictions, they cannot be retrofitted with exterior insulation. Interior insulation must therefore be considered as an alternative. Lack of insulation directly results in energy waste as well as heat loss and gain. Furthermore, it adversely affects heating, ventilation, and air conditioning (HVAC) loads, equipment sizing, indoor air quality, and thermal comfort for residents. The objective of this study is to simulate and evaluate the effects of various internal thermal insulation materials and strategies on mass masonry load-bearing walls in multifamily buildings with attention to various variables and parameters. It not only addresses the energy performance and cost savings associated with an interior insulation retrofit, but also outlines other variables and parameters that are factors in the selection of optimum insulation material, including installations costs, payback periods, useful internal space loss, and options for the depth of the interior insulation retrofit. The audience for this paper is diverse: homeowners, contractors and remodelers, architects and designers, engineers, housing and preservation authorities, and more can benefit from understanding the results outlined in this study. [ABSTRACT FROM AUTHOR]

The deterioration of reinforced concrete bridges due to environmental stressors is proven to adversely affect their strength and durability over time. This primarily originates from the penetration of aggressive ions, leading to the corrosion of steel rebars embedded in concrete. A range of factors, such as temperature, humidity, and precipitation, have a direct impact on this process and can greatly influence the corrosion initiation time. In the United States, the Midwest region is known to experience long winters, requiring multiple applications of deicing salts to keep the roadways open. The amount of deicing salts used on an annual basis has witnessed constant growth, while the climate change is believed to have intensified the exposure conditions. To investigate the deterioration of bridges serving the roads in the Midwest region, a computational framework is developed to predict the corrosion initiation time based on regional climate data obtained for the three major cities of Chicago, Minneapolis, and Des Moines. In addition, a rigorous sensitivity analysis is performed to evaluate the contribution of various input parameters based on the Sobol indices. In the absence of any similar studies on the bridges in the Midwest region, this investigation predicts the extent of vulnerability of the region's bridges to deterioration based on historical climate data, as well as future forecasts. From the simulation results, the impact of climate conditions on the crack width and time duration to reach the durability thresholds has been quantified. With the possibility of an extension to other cold climate regions, the outcome of this study is expected to help transportation agencies optimize their maintenance and repair actions, which will not only improve the condition state of the bridges in service but also reduce the time, effort, and investment needed for the management of a large inventory of bridges. [ABSTRACT FROM AUTHOR]

The article provides insights into the severity of the 2012 U.S. Midwest drought and its impacts over the region utilizing existing and new techniques. Agricultural activities across the U.S. are said to be severely impacted by the drought in 2012, particularly corn and soybean crops. An overview of the potential causes of the drought and its impact is provided. The U.S. drought monitor classification scheme is also described.

Examines the mechanical properties of the Saint Peter Sandstone in the Middle West. Geology of Saint Peter Sandstone; Discussion of the results of laboratory and thin section analyses; Use of the pressuremeter as alternative to laboratory testing.