Architectural Engineering

This paper presents an overview of preliminary results from an on-going research thrust to create a structured procedure for an owner to develop a detailed Building Information Modeling (BIM) implementation strategy within their organization. The paper documents initial results which define an Owner’s Planning Procedure for Building Information Modeling (BIM) and key BIM Planning Elements for Organizations. Through focus group meetings, interviews, work sessions, and literature review, three primary tasks have been identified for developing a detailed BIM execution plan for owner organizations: 1) Conducting an Organizational BIM Assessment, 2) Establishing an approach to the future implementation of BIM, and 3) Developing the BIM transition plan. The BIM Planning Elements identified need to be evaluated and considered during each step in the planning procedure. These planning elements include: a) BIM Mission and Goals; b) Organizational and Project BIM Uses; c) Project and Organiza...

We developed, characterized, and tested a new dual-collimation aqueous UV reactor to improve the accuracy and consistency of aqueous k-value determinations. This new system is unique because it collimates UV energy from a single lamp in two opposite directions. The design provides two distinct advantages over traditional single-collimation systems: 1) real-time UV dose (fluence) determination; and 2) simple actinometric determination of a reactor factor that relates measured irradiance levels to actual irradiance levels experienced by the microbial suspension. This reactor factor replaces three of the four typical correction factors required for single-collimation reactors. Using this dual-collimation reactor, Bacillus subtilis spores demonstrated inactivation following the classic multi-hit model with k=0.1471cm(2)/mJ (with 95% confidence bounds of 0.1426 to 0.1516).

Epidemiological evidence indicates that common environmental allergens found in building reservoirs are strongly associated with the development of bronchial hyper-reactivity (BHR) or asthma, affecting up to half the population in North America and Europe. Although they are rarely life threatening, these diseases cause much distress and lost time from school and work. These diseases are believed inhalation sensitized and developed, suggesting an aerobiological pathway of allergen-containing carrier particles from reservoir to occupant respiration. This study presents and develops a controlled and characterized method to explore the influence of human walking on the aerosolization of allergen-containing particles. Time resolved particle size distribution and allergen content are measured for particles resuspended from representative samples of flooring materials and for different sets of floor disturbances in an environmentally controlled experimental chamber. Initial results, when placed in the context of previous investigations, indicate the method can be utilized to develop a database for particle resuspension rates.

Controlled milling of natural source materials has led to establishment of an allergen carrier particle sample bank for common, indoor, allergen proteins. Allergen "reference" powders are obtained from controlled processing of spent dust mite culture, roach colony fras, and cat and dog fur samples from pet grooming establishments. Due to wide variations in parent material particle size, shape, hardness or tensile strength, different milling prescriptions are required to produce appreciable yields of suspendable particles in the 0.5-20 µm size range with substantial mass fractions less than 12 µm. Characterization data includes: mass fraction and number particle size distributions determined by optical scattering and inertial impactor methods; particle morphology as determined by scanning electron microscope examination; allergen concentrations determined by immuno-assay enzyme-linked analysis (ELISA); inhalation exposure risk analysis of the powders as reservoir dusts. Certified quartz powders (99% < 10 microns) and Bacillus Thuringiensis spores serve as reference powders.

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. ii DISCLAIMER Portions of this document may be illegible electronic image products. Images are produced from the best available original document.

With advancements in design tools, architects and engineers have developed novel sustainable solutions that reduce the amount of embodied carbon in structures while maintaining structural integrity. A concrete structural system, though commonly used, contributes a large portion of a building's overall weight, emissions, and embodied carbon. Concrete systems are often overdesigned in terms of material when using common construction and fabrication practices, resulting in a larger building embodied carbon footprint than necessary. As advanced construction technology and fabrication methods have emerged alongside performance-based design methods, new design possibilities can be found through computational methods such as structural optimization. However, structural optimization procedures often neglect secondary design objectives such as acoustics during the computational process. Acoustic-based performance objectives are directly impacted by structural shaping due to the overlap of objectives such as structural mass, which relates to sustainability. Sound phenomenon such as speech can be easily transmitted through lighter, thinner elements compared to heavier, stiffer elements. The acoustic characteristic of transmission loss, which describes the amount of sound transmitted through a structure, is a concern while shaping concrete slabs, as geometry-based structural optimization may create an unsatisfactory acoustic environment between building floors. The acoustic metric, sound transmission class (STC), is used to provide a single number quantity to represent the transmission loss values in one-third octave bands. This thesis performs an investigation of structural and acoustic behavior for shaped concrete slabs with curved, non-standard geometry. Nine unique geometric variables were used to define and shape concrete slabs. For this parametric geometry, structural and acoustic models were developed to simultaneously evaluate each design as geometric variables changed. The design space was sampled using Latin Hypercube Sampling (LHS) to determine broad relationships between structural mass and STC. Structural mass is the objective that relates to embodied carbon; as structural mass decreases, the amount of embodied carbon the slab has decreases. STC is a standard metric that quantifies acoustic performance of speech and noise transmission through a structure. The structural model and acoustic model identify slab designs that meet all the structural and acoustic checks. Following initial design space exploration, multiobjective optimization (MOO) was used to improve upon the resolution of obtaining the best shaped slabs in the design space while confirming the general structural-acoustic trends from LHS. Then constrained optimization was used to find the best performing shaped slab designs at specific acoustic levels. Constrained optimization further increased the resolution of obtaining the best shaped slabs from MOO. The benefits of shaped concrete slabs were then compared to conventional layered floor constructions.

Amorphous silicon films prepared by electron beam evaporation have systematically and substantially greater atomic density for higher thickness, higher growth temperature, and slower deposition rate, reaching the density of crystalline Si when films of thickness greater than ∼ 300 nm are grown at 425 • C and at < 1 Å/sec. A combination of spectroscopic techniques provide insight into atomic disorder, local strains, dangling bonds, and nanovoids. Electron diffraction shows that the shortrange order of the amorphous silicon is similar at all growth temperatures, but fluctuation electron microscopy shows that films grown above room-temperature show a form of medium-range order not previously observed in amorphous silicon. Atomic disorder and local strain obtained from Raman spectroscopy reduce with increasing growth temperature and show a non-monotonic dependence on thickness. Dangling bond density decreases with increasing growth temperature and is only mildly dependent on thickness. Positron annihilation Doppler broadening spectroscopy and electron energy loss spectroscopy show that nanovoids, and not density variations within the network, are responsible for reduced atomic density. Specific heat and mechanical loss measurements, which quantify the density of tunneling two-level systems, in combination with the structural data, suggest that two-level systems in amorphous silicon films are associated with nanovoids and their surroundings; which are in essence loosely bonded regions where atoms are less constrained.

Computational tools have become integrated into design practice at the building scale and component scale. While there has been a resurgence of optimization techniques in room acoustics, research has been limited on utilizing optimization techniques on building components, such as a building's structural floor. Quality design solutions must be found at the component scale to accommodate for increased urbanization, environmental concerns, building utilization, and the well-being of the occupants, especially in relation to the tenants' acoustic environment. This presentation will discuss the use of several design space exploration and optimization approaches to generate and consider multiple permutations of shaped concrete floor designs. The shape of the ribbed slab will be varied in order to improve both the embodied energy of the concrete slab, which is proportional to mass, as well as the sound transmission class (STC). Three computational techniques (Latin Hypercube Sampling, multi-objective evolutionary optimization and constrained optimization) will be used to determine trade-offs in the design. The advantages and disadvantages of each technique will be highlighted with respect to the trade-off between reduced mass and improved STC. Finally, the importance of model resolution will be discussed in early design space exploration and optimization procedures.