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Showing 4 results for Efficiency

Farhoudi J., Shah Alami H.,
Volume 3, Issue 1 (3-2005)

The rectangular broad crested weirs are widely used to measure the water dischargewhich is one of the most popular tools in the irrigation canals particularly, in developingcountries.The present article is trying to demonstrate the results of an experimental work carriedout on rectangular broad crested weir with sloped upstream face to investigate the effect ofupstream slope on discharge efficiency. The upstream slope was varying from 90 to 23 degreeswhile incoming discharge was ranging from 14 to 75 lit/ sec. The experiments were conducted in aflume with a weir of fixed height under the normal downstream water depth .It is revealed that theslope of upstream face in rectangular broad crested weir would smoothen the flow profile havingthe critical depth on the weir crest adjacent and upstream of downstream edge of the weir . Theresults also lead to a novel achievement showing that the weir discharge efficiency is dependenton the slope of upstream face of the weir. As the slope of upstream face of the rectangular broadcrested weir is decreasing from 90 to 23 the weir discharge efficiency is increasing and reachingto its maximum through a parabola function at slope angle of 25 degrees(i.e. 1:2.15). Theinvestigation also showed that the depth of flow over the weir crest, the specific energy head ofthe approaching flow relative to chanel bed and the critical depth would be a pertinent similarityscales to asses the flow behavior over different sloped rectangular broad crested weirs betweenmodel and prototype. However, some broad investigation is recommended to endorse theachievements.
A. Arabzadeh, R. Aghayari, Ali A. R. Rahai,
Volume 10, Issue 4 (12-2012)

Strut-and-Tie Model (STM) can be used to model the flow of compression within a concrete strut. Concrete struts are formed

in various shapes such as prismatic or bottle-shaped. In order to study the behavior of concrete struts, a series of simple tests

were performed. Eighteen reinforced concrete isolated struts with compressive strength of 65 MPa were tested up failure under

point loading in the plane of specimens. The tested specimens were reinforced by various reinforcement layouts. The behavior

of tested beams was investigated. Observations were made on transverse displacement, primary cracking and ultimate failure

load and distribution of strain on the face of tested panels. Based on these observations, the geometry of the concrete struts was

examined. a new model to analysis of concrete struts was proposed based on modified compression field theory (MCFT). A

database of 44 tested specimens was compiled to evaluate the proposed model. The results indicate that using the ACI and CSA

codes expressions regarding the amount of minimum required reinforcement in a strut produces conservative but erratic results

when compared with the test data. Conversely, the new proposed model presents a more accurate prediction for the strength of

44 tested struts.

A. Eslami, I. Tajvidi, M. Karimpour-Fard,
Volume 12, Issue 1 (1-2014)

Three common approaches to determine the axial pile capacity based on static analysis and in-situ tests are presented, compared and evaluated. The Unified Pile Design (UPD), American Petroleum Institute (API) and a SPT based methods were chosen to be validated. The API is a common method to estimate the axial bearing capacity of piles in marine environments, where as the others are currently used by geotechnical engineers. Seventy pile load test records performed in the northern bank of Persian Gulf with SPT profile have been compiled for methods evaluation. In all cases, pile capacities were measured using full scale static compression and/or pull out loading tests. As the loading tests in some cases were in the format of proof test without reaching the plunging or ultimate bearing capacity, for interpretation the results, offset limit load criteria was employed. Three statistical and probability based approaches in the form of a systematic ranking, called Rank Index, RI, were utilized to evaluate the performance of predictive methods. Wasted Capacity Index (WCI) concept was also applied to validate the efficiency of current methods. The evaluations revealed that among these three predictive methods, the UPD is more accurate and cost effective than the others.
N. Kaid, M. Cyr, H. Khelafi,
Volume 13, Issue 4 (12-2015)

The paper presents the characterisation of an Algerian natural pozzolan (NP) intended to for use in cement-based materials. The experimental programme was based on different tests on paste and mortar. The pozzolanic activity was assessed by the means of lime consumption over time of mixtures of lime-pozzolan (75% NP and 25% Ca(OH)2, water-binder ratio of 0.45). The degree of reactivity was assessed by observing the crystallographic changes (XRD) and lime consumption (TG) up to 1 year of hydration. The effect of NP on cement-based mixtures was based on the measurement of the water demand and setting time of pastes, and on the compressive strength of mortars, up to one year. The replacement rates of cement by pozzolan were 5, 10 and 15%. A superplasticizer was used (0, 1, 2 and 3% of the binder mass). A calculation of the carbon footprint was investigated in order to assess if the natural pozzolan could be considered as eco-efficient when used in replacement of the clinker. The results showed that NP had a medium pozzolanic reactivity and with a medium-low silica content. The use of NP usually led to a small increase in the water/binder ratio (up to 10%) to maintain constant workability. The setting time was also increased by around 20%. Nevertheless, strength tests showed that the pozzolan had sufficient activity to counteract the water demand, since long-term compressive strength of the binary system (cement + pozzolan) were higher than those of cement alone. The use of NP in replacement of clinker involves a reduction in CO2 emissions for transport up to 1800 km, which is compatible with sustainable development. The results are most promising from both a performance-based and an environmental point of view

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