scholarly journals The Behaviour of Half-Slabs and Hollow-Core Slab in Four-Edge Supported Conditions

2021 ◽  
Vol 11 (21) ◽  
pp. 10354
Author(s):  
Jakub Zając ◽  
Łukasz Drobiec ◽  
Radosław Jasiński ◽  
Mirosław Wieczorek ◽  
Wojciech Mazur ◽  
...  
Keyword(s):  
Computational Models ◽  
Hollow Core ◽  
Short Term ◽  
Design Procedures ◽  
Current Design ◽  
Hollow Core Slab ◽  
Longitudinal Joints ◽  
Electronic Method ◽  
Conservative Estimation

In this study, qualitative tests were carried out to compare the behaviour of selected slabs exposed to short- and long-term loading. Full-scale models of the half-slab and hollow-core slab with dimensions of 6.30 m × 6.30 m, built of four different precast panels, were tested. The first two were semi-precast lattice girder slabs, the third semi-precast prestressed ribbed panels, and the last was composed of hollow-core panels. A common feature was the lack of joint reinforcement and the same modular width of 600 mm. The short-term load was applied sequentially in the first stage, and displacement was measured using an electronic method. In the second stage of long-term testing, the load was mainly applied to one part of the slab. Testing under short-term and long-term load allows determining the change in the performance of panel slabs over time. The panels maintained the ability of load redistribution based on their interaction despite the work of the longitudinal joints being only through the concrete cross-section. The behaviour of slabs with concrete topping shows more significant lateral interactions than elements connected only by shear key. Comparative calculations were made based on four computational models. Comparative analysis showed that the current design procedures lead to a safe but conservative estimation of the slab behaviour.

scholarly journals Comparison of the Performance of Prestressed Ribbed Panels and Hollow Core Panels Supported on Four-Edges

2021 ◽  
Vol 1203 (3) ◽  
pp. 032049
Author(s):  
Jakub Zając ◽  
Łukasz Drobiec
Keyword(s):  
Cross Section ◽  
Hollow Core ◽  
Short Term ◽  
Shear Key ◽  
Scale Models ◽  
Longitudinal Joints ◽  
Electronic Method ◽  
Aerated Concrete ◽  
The Difference ◽  
Different Response

Abstract Tests of full-scale models of the precast slab with dimensions of 6.30 x 6.30 m, built of two different precast panels, were carried out under short-term load. The models were made of autoclaved aerated concrete (700 type) brick with a thickness of 240 mm and a height of 2.24 m. The slabs were supported at four edges. The first slab was precast prestressed ribbed panels with concrete overtopping. The second slab was made of prestressed hollow-core panels. The panels had the same modular width of 600 mm. Tests were carried out under load placed on the top of the slab. The short-term load was applied sequentially, and displacement measurements were measurement by the electronic method. The load was initially applied evenly distributed. In the last step, part of the load was transferred to one-half of the slabs. The obtained load was different for each half of the slab. The first part of the slab were panels 1 to 5, loaded with the value of 1.7 kN/m2, and the second part was panels 6 to 10 loaded with the value of 7.7 kN/m2. The tests allow determining the difference in slabs' performance depending on shear key construction. The panels maintained the possibility of load redistribution based on their interaction despite the longitudinal joints' work only through the concrete cross-section. The slabs had a different character of transverse displacements depending on the presence of concrete topping. The models revealed a different response to transferring part of the load to one-half of the slabs. There were no cracks in the line of longitudinal joints on the upper surface of the slabs. Also, there were no cracks on the bottom of the panels. At the panels' connection with the wall, rotation and lifting corners of the slabs were noticed. The measured displacements were significantly smaller than for the corresponding models of single-span slabs with a parallel load.

scholarly journals Performance of soil nails in Dublin glacial till

2008 ◽  
Vol 45 (12) ◽  
pp. 1685-1698 ◽  
Author(s):  
Christopher O. Menkiti ◽  
Michael Long
Keyword(s):  
Large Scale ◽  
Design Methods ◽  
Glacial Till ◽  
Deformation Pattern ◽  
Soil Nailing ◽  
Short Term ◽  
Soil Nail ◽  
Design Procedures ◽  
Temporary Support ◽  
Current Design

Soil nailing is being used in many projects in glacial tills in Ireland, particularly to provide temporary support to steep slopes. Little design guidance is available for such materials, and it is known that the application of design procedures developed for other material is conservative. Detailed nail instrumentation and field monitoring has been undertaken during large-scale soil nailing works for the Dublin Port Tunnel project. It was found that the short-term behaviour of nails was the reverse of that assumed in current design methods. Most of the load was induced as a results of drilling and nailing the lift immediately below the nail being monitored rather than due to excavation-induced stress relief. The highest forces were developed in the upper nails where the largest ground movements occurred. This is the reverse of most current design methods where the highest soil–nail bond is assigned to the deepest nails. It seems that the observed short-term, prefailure behaviour of nailed slopes is governed more by the deformation pattern of the slope than by large-scale development of failed wedges. Current design procedures should be reviewed. Despite this, the trial confirmed that the currently used procedures are highly conservative for Dublin glacial till.

Duration of load tests for shear strength

1986 ◽  
Vol 13 (2) ◽  
pp. 188-195 ◽  
Author(s):  
R. A. Spencer ◽  
Borg Madsen
Keyword(s):  
Shear Strength ◽  
Stress Ratio ◽  
Control Sample ◽  
Term Strength ◽  
Short Term ◽  
Current Design ◽  
Short Term Strength ◽  
Load Effects ◽  
Duration Of Load

The strength of wood falls with time under load, and in current design codes the short-term strength of wood is reduced by about 40% to account for duration of load effects. This figure is based on tests made on small bending specimens. In this paper are described tests made on wooden torque tubes to investigate the effect of duration of load on shear strength. A control sample was tested to establish a curve for short-term strength, and four groups of 80 specimens each were then tested under various levels of constant long-term load. Stress ratio at failure was estimated by assuming that the short-term strength of each group could be represented by the control curve, and that under long-term loading specimens would fail in the order of their short-term strength. In each group the stress ratio at failure fell with time under load, and this reduction appears to be related to that predicted by a viscoelastic plastic model. It is concluded that the Madison curve presently used to predict duration of load effects may be conservative at normal levels of applied stress. Key words: wood, shear, long-term loading, duration of load.

The Cost of Structure Learning

2017 ◽  
Vol 29 (10) ◽  
pp. 1646-1655 ◽  
Author(s):  
Anne G. E. Collins
Keyword(s):  
Computational Models ◽  
Structure Learning ◽  
Behavioral Experiment ◽  
Learning Problem ◽  
Short Term ◽  
New Information ◽  
Transfer Rules ◽  
Learning Flexibility ◽  
The Cost

Human learning is highly efficient and flexible. A key contributor to this learning flexibility is our ability to generalize new information across contexts that we know require the same behavior and to transfer rules to new contexts we encounter. To do this, we structure the information we learn and represent it hierarchically as abstract, context-dependent rules that constrain lower-level stimulus–action–outcome contingencies. Previous research showed that humans create such structure even when it is not needed, presumably because it usually affords long-term generalization benefits. However, computational models predict that creating structure is costly, with slower learning and slower RTs. We tested this prediction in a new behavioral experiment. Participants learned to select correct actions for four visual patterns, in a setting that either afforded (but did not promote) structure learning or enforced nonhierarchical learning, while controlling for the difficulty of the learning problem. Results replicated our previous finding that healthy young adults create structure even when unneeded and that this structure affords later generalization. Furthermore, they supported our prediction that structure learning incurred a major learning cost and that this cost was specifically tied to the effort in selecting abstract rules, leading to more errors when applying those rules. These findings confirm our theory that humans pay a high short-term cost in learning structure to enable longer-term benefits in learning flexibility.

A Comparison of Methods for Assessing the Lifetime Reliability of a Moored FPSO

2004 ◽  
Author(s):  
Andrew J. Grime ◽  
R. S. Langley
Keyword(s):  
Reliability Analysis ◽  
Offshore Structures ◽  
Extreme Value Analysis ◽  
Design Codes ◽  
Short Term ◽  
Safety Level ◽  
Value Analysis ◽  
Design Storm ◽  
Current Design

Current design codes for floating offshore structures are based on measures of short-term reliability. That is, a design storm is selected via an extreme value analysis of the environmental conditions and the reliability of the vessel in that design storm is computed. Although this approach yields valuable information on the vessel motions, it does not produce a statistically rigorous assessment of the lifetime probability of failure. An alternative approach is to perform a long-term reliability analysis in which consideration is taken of all sea states potentially encountered by the vessel during the design life. Although permitted as a design approach in current design codes, the associated computational expense generally prevents its use in practice. A new efficient approach to long-term reliability analysis is presented here, the results of which are compared with a traditional short-term analysis for the surge motion of a representative moored FPSO in head seas. This serves to illustrate the failure probabilities actually embedded within current design code methods, and the way in which design methods might be adapted to achieve a specified target safety level.

scholarly journals Research on semi-precast prestressed concrete slab under short-term and long-term load

2020 ◽  
Vol 323 ◽  
pp. 02001
Author(s):  
Jakub Zając ◽  
Łukasz Drobiec ◽  
Radosław Jasiński ◽  
Wojciech Mazur ◽  
Krzysztof Grzyb ◽  
...  
Keyword(s):  
Prestressed Concrete ◽  
Concrete Slab ◽  
Scale Model ◽  
Concrete Slabs ◽  
Short Term ◽  
Shear Key ◽  
Vertical Displacements ◽  
Electronic Method ◽  
Precast Prestressed Concrete

Tests of a full-scale model of slab with the dimensions of 6.30x6.30m, built of TerivaPanel panels were carried out under short-term and long-term load. TerivaPanel panels are partial precast, pre-tensioned concrete slabs with ribs connected at the bottom. The panels have a specially shaped cross-connection (shear key) enabling loads to be transferred between the panels. The tests were carried out under a load placed on the top of the slab. Additionally, the load was applied sequentially. Measurements were made by an electronic method. In one of the stages, long-term testing, the load was applied to one half of the slab to examine the possibility of faulting. The measurements were carried out at monthly intervals, using a geodetic method. The values of vertical displacements at the panel joints (in the middle of the slab) and for central panels along the entire length of the joint were measured.

Long-term extreme buffeting response of long-span bridges considering uncertain turbulence parameters

2021 ◽  
Author(s):  
Tor Martin Lystad ◽  
Aksel Fenerci ◽  
Ole Øiseth
Keyword(s):  
Short Term ◽  
Long Span Bridges ◽  
Buffeting Response ◽  
Long Span ◽  
Long Span Bridge ◽  
Extreme Response ◽  
Current Design ◽  
Extreme Responses ◽  
Turbulence Parameters

<p>Long-term extreme response analyses are recognized as the most accurate way to predict the extreme responses of marine structures excited by stochastic environmental loading. In wind engineering for long-span bridges this approach has not become the standard method to estimate the extreme responses. Instead, the design value is often estimated as the expected extreme response from a short-term storm described by an N-year return period mean wind velocity.</p><p>In this study, the long-term extreme buffeting response of a long-span bridge is investigated, and the uncertainty of the turbulent wind field is described by a probabilistic model. The results indicate that the current design practice may introduce significant uncertainty to the buffeting load effects used in design, when the variability in the turbulence parameters as well as the uncertainty of the short-term extreme response is neglected.</p>

Conceptual short-term memory (CSTM) supports core claims of Christiansen and Chater

2016 ◽  
Vol 39 ◽  
Author(s):  
Mary C. Potter
Keyword(s):  
Working Memory ◽  
Rapid Serial Visual Presentation ◽  
Language Comprehension ◽  
Short Term Memory ◽  
Visual Presentation ◽  
Long Term Memory ◽  
Short Term ◽  
Term Memory ◽  
Use Of Knowledge

AbstractRapid serial visual presentation (RSVP) of words or pictured scenes provides evidence for a large-capacity conceptual short-term memory (CSTM) that momentarily provides rich associated material from long-term memory, permitting rapid chunking (Potter 1993; 2009; 2012). In perception of scenes as well as language comprehension, we make use of knowledge that briefly exceeds the supposed limits of working memory.

Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

1990 ◽  
Vol 48 (3) ◽  
pp. 374-375
Author(s):  
D.E. Loudy ◽  
J. Sprinkle-Cavallo ◽  
J.T. Yarrington ◽  
F.Y. Thompson ◽  
J.P. Gibson
Keyword(s):  
Antidepressant Drug ◽  
Beagle Dogs ◽  
Long Term Effects ◽  
Short Term ◽  
Platelet Counts ◽  
Toxicological Studies ◽  
Induced Aggregation ◽  
Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

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