scholarly journals Nonlinear Model of an Additional Concrete Head and its Comparison with Long-Term Measurements

2018 ◽  
Vol 26 (3) ◽  
pp. 1-10
Author(s):  
Jan Nováček ◽  
Miloš Zich ◽  
Michal Hasa
Keyword(s):  
Analytical Models ◽  
Laboratory Research ◽  
Bottom Surface ◽  
Construction Site ◽  
Flat Slab ◽  
Bond Slip ◽  
Flat Slabs ◽  
Temperature Load ◽  
Long Term Measurement

Abstract An additional concrete head or drop panels are not common solutions for strengthening flat slabs and have not yet been an adequately studied solution in the field of laboratory research. The investigation of drop panels in a laboratory is quite complicated, so that an examination directly at a construction site could be a better solution. Long-term measurement sensors were installed inside a concrete drop panel, which is on the bottom surface of a flat slab. Gauging was performed during various loading situations, including the loading of heavy machines, the ambient temperature load, and a uniformly distributed load. Results from the measurements are given in comparison with analytical models, which have been studied with respect to the influence of shrinkage and the bond-slip behaviour of a reinforcement.

scholarly journals Limitations on ACI Code Minimum Thickness Requirements for Flat Slab

2021 ◽  
Vol 7 (11) ◽  
pp. 1918-1932
Author(s):  
Bilal Ismaeel Abd Al-Zahra ◽  
Maitham Alwash ◽  
Ameer Baiee ◽  
Ali A. Shubbar
Keyword(s):  
Compressive Strength ◽  
Slab Thickness ◽  
Minimum Thickness ◽  
Element Analysis ◽  
Flat Slab ◽  
Flat Slabs ◽  
Wide Range ◽  
High Consistency ◽  
Panel Thickness

Reinforced concrete two-way flat slabs are considered one of the most used systems in the construction of commercial buildings due to the ease of construction and suitability for electrical and mechanical paths. Long-term deflection is an essential parameter in controlling the behavior of this slab system, especially with long spans. Therefore, this study is devoted to investigating the validation of the ACI 318-19 Code long-term deflection limitations of a wide range of span lengths of two-way flat slabs with and without drop panels. The first part of the study includes nonlinear finite element analysis of 63 flat slabs without drops and 63 flat slabs with drops using the SAFE commercial software. The investigated parameters consist of the span length (4, 5, 6, 7, 8, 9, and 10m), compressive strength of concrete (21, 35, and 49 MPa), the magnitude of live load (1.5, 3, and 4.5 kN/m2), and the drop thickness (0.25tslab, 0.5tslab, and 0.75tslab). In addition, the maximum crack width at the top and bottom are determined and compared with the limitations of the ACI 224R-08. The second part of this research proposes modifications to the minimum slab thickness that satisfy the permissible deflection. It was found, for flat slabs without drops, the increase in concrete compressive strength from 21MPa to 49MPa decreases the average long-term deflection by (56, 53, 50, 44, 39, 33 and 31%) for spans (4, 5, 6, 7, 8, 9, and 10 m) respectively. In flat slab with drop panel, it was found that varying drop panel thickness t2 from 0.25  to 0.75  decreases the average long-term deflection by (45, 41, 39, 35, 31, 28 and 25%) for span lengths (4, 5, 6, 7, 8, 9 and 10 m) respectively. Limitations of the minimum thickness of flat slab were proposed to vary from Ln/30 to Ln/19.9 for a flat slab without a drop panel and from Ln/33 to Ln/21.2 for a flat slab with drop panel. These limitations demonstrated high consistency with the results of Scanlon and Lee's unified equation for determining the minimum thickness of slab with and without drop panels. Doi: 10.28991/cej-2021-03091769 Full Text: PDF

Continuous automatic measurement of rhythms in fungal respiration using a gas chromatograph

1973 ◽  
Vol 51 (4) ◽  
pp. 701-710 ◽  
Author(s):  
Roger S. Smith
Keyword(s):  
Carbon Dioxide ◽  
Agar Medium ◽  
Quantitative Measure ◽  
Automatic Measurement ◽  
Carbon Dioxide Production ◽  
Chromatographic Technique ◽  
Gas Chromatograph ◽  
Growth Chambers ◽  
Long Term Measurement

The long-term measurement of aerobic fungal respiration, both on an agar medium and on wood blocks, was possible using a gas-chromatographic technique for the detection of the carbon dioxide. This method was fully automated to analyze gas samples sequentially from eight or more growth chambers, after variable but determined time periods. It provided a precise quantitative measure of the respired carbon dioxide, presented both in the form of punched computer tape and normal printed teleprinter output. This apparatus worked continuously for several years without serious breakdown.The fungi Lentinus lepideus, Lenzites trabea, Poria monticola, and several strains of Coniophora puteana all showed a rhythm in their respiration which was not controlled by temperature or light. The magnitude and frequency of the rhythmical peaks in carbon dioxide production varied between fungi and, although there was considerable variation between different isolates of the same species, the separation of these species of fungi based on their different patterns of respiration was possible.

scholarly journals Routes to Research for Novice Undergraduate Neuroscientists

2006 ◽  
Vol 5 (2) ◽  
pp. 175-187 ◽  
Author(s):  
Kyle J. Frantz ◽  
Robert L. DeHaan ◽  
Melissa K. Demetrikopoulos ◽  
Laura L. Carruth
Keyword(s):  
Undergraduate Students ◽  
Attitudes Toward Science ◽  
Laboratory Research ◽  
Research Experience ◽  
Neuroscience Research ◽  
Long Term Follow Up ◽  
Apprenticeship Model ◽  
Design Experiments

Undergraduate students may be attracted to science and retained in science by engaging in laboratory research. Experience as an apprentice in a scientist's laboratory can be effective in this regard, but the pool of willing scientists is sometimes limited and sustained contact between students and faculty is sometimes minimal. We report outcomes from two different models of a summer neuroscience research program: an Apprenticeship Model (AM) in which individual students joined established research laboratories, and a Collaborative Learning Model (CLM) in which teams of students worked through a guided curriculum and then conducted independent experimentation. Assessed outcomes included attitudes toward science, attitudes toward neuroscience, confidence with neuroscience concepts, and confidence with science skills, measured via pre-, mid-, and postprogram surveys. Both models elevated attitudes toward neuroscience, confidence with neuroscience concepts, and confidence with science skills, but neither model altered attitudes toward science. Consistent with the CLM design emphasizing independent experimentation, only CLM participants reported elevated ability to design experiments. The present data comprise the first of five yearly analyses on this cohort of participants; long-term follow-up will determine whether the two program models are equally effective routes to research or other science-related careers for novice undergraduate neuroscientists.

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