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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]

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]

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]