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This paper describes the calibration of a phenomenological hinge model to simulate the nonlinear hysteretic response of reinforced concrete (RC) beam-columns under large deformations. The model is developed to enable simulation of the nonlinear dynamic response of RC frame buildings, from the initiation of damage to the onset of sidesway collapse, under earthquake ground motions. The model’s monotonic backbone curve and hysteretic degradation rules capture post-peak in-cycle softening, combined with cyclic deterioration, which are associated with concrete crushing and reinforcing bar buckling at large cyclic deformations. The model calibration is based on experimental data for 255 rectangular RC columns with widely varying seismic design and detailing characteristics. For each of the 255 tests, the element model parameters, including initial stiffness, inelastic rotation limits, and cyclic energy dissipation capacity, are systematically calibrated to laboratory test data. Regression analyses are then used to develop semi-empirical equations to calculate the model parameters as functions of the column design parameters. The model parameters are calibrated in a statistically rigorous manner, where both median estimates and lognormal standard deviations are reported for each parameter. Important design parameters that affect the column model properties are the axial load ratio, confinement steel ratio, and spacing of confinement steel. [ABSTRACT FROM AUTHOR]

In an effort to limit the environmental impact of concrete materials, there is increasing interest in the development and use of a wider range of minerals as acceptable supplementary cementitious materials (SCMs). This study investigated calcined blended clays of kaolinite and bentonite, with impurities, to assess their feasibility as SCMs. The combined use of Rietveld quantitative x-ray diffraction (RQXRD) and thermogravimetric analysis (TGA) techniques proved useful in initially gauging amorphous content post-calcination, lending insight into the relationship between calcination temperature and pozzolanic reactivity. The results demonstrated that for the calcined blended clays, as the amorphous content increased, the SCM consumed more portlandite and the compressive strength of cement-SCM mortars increased. Blends of kaolinite–bentonite clays, containing initially 35 wt.% crystalline kaolinite prior to calcination, achieved roughly 10% increase in compressive strength over samples containing 100 wt.% cement, at 90 days. Blended kaolinite SCMs may offer significant advantages as a low-cost alternative binder or cement replacement material, with the ability to maintain or enhance mechanical strength. [ABSTRACT FROM AUTHOR]

The objectives of this study were to use activation treatments on sodium montmorillonite and illite shale, to alter early hydration or later pozzolanic reactivity when used as supplementary cementitious materials (SCMs). For comparison purposes, treatment methods were also applied to the highly reactive pozzolan, metakaolin, and the inert filler, quartz. Activation treatment strategies included the addition of 0.15wt% zinc oxide and the use of thermal treatments to the SCMs at temperatures of 650°C, 830°C and 930°C. The use of zinc oxide additions increased the early hydration rate of SCM-containing pastes, yet introduced a chemical retardation and negatively impacted early compressive strengths. Moreover, the results suggest that retardation was inversely correlated with the pozzolanic reactivity of the SCM used. Thermal treatment methods were effective at influencing the SCM pozzolanic reactivity, with montmorillonite calcined at 830°C and illite calcined at 930°C behaving as late-reacting pozzolans. SCMs calcined at these temperatures resulted in higher 90day compressive strengths compared to mortars containing the quartz filler. Overall, this study provides insight into different strategies that maybe used to enhance the reactivity of impure calcined clays in order to facilitate their acceptance into the concrete industry. [ABSTRACT FROM AUTHOR]

Abstract: Radon (222Rn) and progenies emanate from soil and building components and can create an indoor air quality hazard. In this study, nine concrete constituents, including the supplementary cementitious materials (SCMs) fly ash and metakaolin, were used to create eleven different concrete mixtures. We investigated the effect of constituent radium specific activity, radon effective activity and emanation fraction on the concrete emanation fraction and the radon exhalation rate. Given the serious health effects associated with radionuclide exposure, experimental results were coupled with Monte Carlo simulations to demonstrate predictive differences in the indoor radon concentration due to concrete mixture design. The results from this study show that, on average, fly ash constituents possessed radium specific activities ranging from 100Bq/kg to 200Bq/kg and emanation fractions ranging from 1.1% to 2.5%. The lowest emitting concrete mixture containing fly ash resulted in a 3.4% reduction in the concrete emanation fraction, owing to the relatively low emanation that exists when fly ash is part of concrete. On average, the metakaolin constituents contained radium specific activities ranging from 67Bq/kg to 600Bq/kg and emanation fractions ranging from 8.4% to 15.5%, and changed the total concrete emanation fraction by roughly ±5% relative to control samples. The results from this study suggest that SCMs can reduce indoor radon exposure from concrete, contingent upon SCM radionucleotide content and emanation fraction. Lastly, the experimental results provide SCM-specific concrete emanation fractions for indoor radon exposure modeling. [Copyright &y& Elsevier]

Abstract: The uptake of pollutants by building surfaces can potentially improve both indoor and outdoor air quality. Cement renders provide a unique opportunity for passive pollutant removal because they can cover large surface areas. This study investigated the passive removal of carbon dioxide and ozone by cement renders having varied binder compositions and curing durations. The results from this study demonstrated shorter curing durations resulted in greater pollutant uptake. However, the use of the supplementary cementitious material, metakaolin, in the cement render increased the carbon dioxide ingress while decreasing the ozone uptake. Therefore, the adaptation of the render composition for the best effective application may result in valuable indoor air quality or carbon savings consequences. [Copyright &y& Elsevier]

Abstract: This study aimed to improve the reactivity of metakaolin-cement mixtures using ZnO additions. Kaolinite samples with 0.1–1wt% ZnO were calcined at temperature intervals of 50°C from 500 to 650°C for 1h. The resulting metakaolins were examined for structural changes after calcination and for their pozzolanic reactivity, influence on the hydration behavior of cement pastes, and impact on the compressive strength of mortar cubes. ZnO behaved as a delayed accelerator for cement paste. However, when ZnO was combined with highly amorphous metakaolin, chemical retardation was eliminated while acceleration was maintained. Such systems also had increased 28-day compressive strengths. ZnO additions did not affect the degree of dehydroxylation or the pozzolanic reactivity of the metakaolin. These results could facilitate the use of less pure calcined clays as SCM by providing a mechanism for improving reactivity and may also impact the ability to use zinc-contaminated materials in concrete. [Copyright &y& Elsevier]

Building model calibration is critical in bringing simulated energy use closer to the actual consumption. This paper presents a novel, automated model calibration approach that uses logic linking parameter tuning with bias pattern recognition to overcome some of the disadvantages associated with traditional calibration processes. The pattern-based process contains four key steps: (1) running the original pre-calibrated energy model to obtain monthly simulated electricity and gas use; (2) establishing a pattern bias, either Universal or Seasonal Bias, by comparing load shape patterns of simulated and actual monthly energy use; (3) using programmed logic to select which parameter to tune first based on bias pattern, weather and input parameter interactions; and (4) automatically tuning the calibration parameters and checking the progress using pattern-fit criteria. The automated calibration algorithm was implemented in the Commercial Building Energy Saver, a web-based building energy retrofit analysis toolkit. The proof of success of the methodology was demonstrated using a case study of an office building located in San Francisco. The case study inputs included the monthly electricity bill, monthly gas bill, original building model and weather data with outputs resulting in a calibrated model that more closely matched that of the actual building energy use profile. The novelty of the developed calibration methodology lies in linking parameter tuning with the underlying logic associated with bias pattern identification. Although there are some limitations to this approach, the pattern-based automated calibration methodology can be universally adopted as an alternative to manual or hierarchical calibration approaches. [ABSTRACT FROM AUTHOR]

Sucrose and zinc oxide (ZnO) are effective cement hydration retarders. The goal of this study was to provide a new look into the ZnO cement hydration mechanism and to investigate impacts of various supplementary cementitious materials (SCMs) on retardation behavior of ZnO and sucrose. Changes in the pore solution composition and reaction kinetics were measured for cementitious systems with ZnO or sucrose that contained rice straw ash (RSA), wheat straw ash, silica fume, metakaolin, and fly ash. Among the SCMs used, RSA dramatically suppressed ZnO and sucrose retardation. Experimental results indicated that the mechanism by which ZnO retards hydration reaction could be nucleation and/or growth poisoning of C-S-H. Reduced retardation of paste samples containing RSA was attributed to the ability of RSA to provide nucleation sites for C-S-H precipitation. This study provides a better understanding of the interaction between SCMs and cement hydration retarders essential in predicting retarder–dose effects. [ABSTRACT FROM AUTHOR]

Small commercial buildings in the United States consume 47% of the total primary energy of the buildings sector. Retrofitting small and medium commercial buildings poses a huge challenge for owners because they usually lack the expertise and resources to identify and evaluate cost-effective energy retrofit strategies. This paper presents the Commercial Building Energy Saver (CBES), an energy retrofit analysis toolkit, which calculates the energy use of a building, identifies and evaluates retrofit measures in terms of energy savings, energy cost savings and payback. The CBES Toolkit includes a web app (APP) for end users and the CBES Application Programming Interface (API) for integrating CBES with other energy software tools. The toolkit provides a rich set of features including: (1) Energy Benchmarking providing an Energy Star score, (2) Load Shape Analysis to identify potential building operation improvements, (3) Preliminary Retrofit Analysis which uses a custom developed pre-simulated database and, (4) Detailed Retrofit Analysis which utilizes real-time EnergyPlus simulations. CBES includes 100 configurable energy conservation measures (ECMs) that encompass IAQ, technical performance and cost data, for assessing 7 different prototype buildings in 16 climate zones in California and 6 vintages. A case study of a small office building demonstrates the use of the toolkit for retrofit analysis. The development of CBES provides a new contribution to the field by providing a straightforward and uncomplicated decision making process for small and medium business owners, leveraging different levels of assessment dependent upon user background, preference and data availability. [ABSTRACT FROM AUTHOR]