The analysis of ductility of connection in Self consolidating concrete (SCC) members
Ali akbar
Maghsoodi
author
text
article
2008
per
The analysis of beam-column connections in reinforced concrete, RC structures are ignored in RC standards. However, recently in limited standards, the designs of such an important members are considered for conventional concrete (the type of concrete needs vibrating). Often, such members are heavily reinforced and the passing ability of conventional concrete and suitable concrete vibrating is difficult. As an alternative, the use of new concrete generation, called as Self consolidating Concrete, SCC (the type of concreter needs no vibrating) not only is an advantageous, but also, it can consider as a basically change in such elements.
Scc, with its high fluidity and no need of inner or outer vibration, and high resistance to segregation and shortening construction time are some of its advantageous. In seismic regions, the design of members based on ductility causes more safety while compared with other methods of design.
In the present research, some of the effective parameters for considering of beam-column connection in SCC members and their steps behavior are investigated.
Concrete Research
University of Guilan
2008-4242
1
v.
2
no.
2008
9
18
https://jcr.guilan.ac.ir/article_789_b41951e1ff0b49267c6252477b64d7f5.pdf
Neural networks for predicting the compressive strength of concrete: error back-propagation and recurrent elman networks
Jafar
Sobhani
author
zahra
sobhani
author
Mansour
Sheikhan
author
text
article
2008
per
In the recent years, the artificial neural networks (NNT) have been widely applied in the various fields of engineering especially in the various fields of the civil engineering. In this paper, two types of neural networks with three architectures were used to predict the compressive strength of concrete samples. In this study, a novel type of NNT, named as the recurrent Elman networks, was introduced and used to predict the compressive strength of concrete samples. Moreover, in this paper, the results of simulation with the Elman networks were compared with the results of traditional back propagation networks. The results of comparison showed that the two layered Elman network which has 5 and 3 neurons in the first and second layer respectively, has the best performance from the generalization perspective; and vice versa the standard BP (with 8 and 5 neurons in the first and second layer) has got the best performance for the estimation purposes
Concrete Research
University of Guilan
2008-4242
1
v.
2
no.
2008
19
33
https://jcr.guilan.ac.ir/article_790_02c719602aa6dcb91799fc3ab6fc2eac.pdf
The effect of mineral and chemical admixtures on viscosity and consis -tency of paste using the FlowCyl (modified Marsh cone) and mini slu -mp tests
mehdi
Khodadad Saryazdi
author
H.
Famili
author
T.
Parhizkar
author
Amir maziyar
Raees Ghasemi
author
text
article
2008
per
The production of high strength concrete (HSC), high performance concrete (HPC) and self consolidating concrete (SCC) at the end of 20th century, made a revolution in the field of concrete technology. Paste (matrix) plays an important role in these concretes. In addition to cement, a variety of mineral additives such as silica fume and fly ash used as pozolans and limestone powder, micr- onized quartzite and fine siliceous sand as fillers are frequently in the paste of these concretes. For reduction of water cement ratio, a variety of chemical admixtures and superplastisizers with different properties has been introduced to the market. In order to optimize mix proportion design of HSC/HPC/SCC, the study of compatibility of these mineral and chemical admixtures with cem -ent and the performance of their combination in the mix is essential and inevitable. The flow properties of the paste can be established by using only a few liters of the material, while providing the designer with useful information for predicting the flow behavior of mortar and concrete. A modified version of Marsh cone test called FlowCyl, was utilized to quantify the viscosity of paste. The result of automated FlowCyl test is not operator dependent and has a good repeatability index. Al -so, using a miniature slump cone, the spread diameter of the paste, which is related to its yield stress, was measured. From these data, the effect of various parameters on fresh properties of paste was studied. The saturation dosage of super plasticizer (SP) for paste, a value beyond which an increase in the SP dosage does not significantly improve the flowability, was investigated. Also the reduction of viscosity one hour after mixing was studied.
Concrete Research
University of Guilan
2008-4242
1
v.
2
no.
2008
https://jcr.guilan.ac.ir/article_791_ddacfcdd9909f91d7c806a53a3ffc2f2.pdf
Study the influence of particle size of nano silica and micro silica on mechanical properties of cements past
M.
Tadaion
author
Mojtaba
Maghrebi
author
M.
Khanzadi
author
Mahmood
habibian
author
text
article
2008
per
This paper presents a laboratory study and comparison on mechanical properties of cement mortar with nano silica and silica fume . The results were compared with those of control Portland cement concrete (OPC) . These included compressive strength and Flexural Strength . after 3 , 28 and 90 days.
The Result Shown in same mass of additive material , the mechanical properties of OPC sam-ples as expected raise by time but finally gain lowest score, e.g. at 90 days the compressive strength sample that contain 10% nano silica have more 70% performance by OPC .
Furthermore samples that contain nano silica have better behavior as silica fume until 28 days , e.g. the sample that contain 7.5% nano silica have 50% better performance as sample that contain same micro silica . after 28 days the samples that contain micro silica shown higher value e.g. at the compressive strength of mortar cement 7.5% micro silica at 90 days earned 40% more score as sample that contain same mass of nano silica .
The samples that contain micro silica and nano silica simultaneously have behavior between result of samples that contain micro silica and the samples that contain nano silica.
Concrete Research
University of Guilan
2008-4242
1
v.
2
no.
2008
https://jcr.guilan.ac.ir/article_792_3746c7440c96f9e35097f3157cc77148.pdf
Improvement of high performance concrete properties by using metakaolin
mohammad
Shekarchizadeh
author
Alireza
Mirdamadi
author
Abouzar
Bonakdar
author
mehdi
bakhshi
author
text
article
2008
per
Metakaoiln is one of the reactive pozzolans which is used in recent years.This additive whi -ch is derived from kaolin clay is applied in Increasing mechanical strength and durability of concrete. It also can be used to improve the decorative features of concrete in some cases.
In this study the effect of replacement of Metakaolin in percentages of 5, 10, 15 on fresh concrete properties (slump, air content, setting time,density),mechanical properties (compres -sive,bending and splitting tensile strength) and durability (penetration depth of water, gas permeability,water absorption,electrical resis -tivity, Potential Alkali-Silica Reactivity (ASR) and chloride penetration) with control concrete with no pozzolan is investigated. Results show high improvement in concrete properties by adding the metakaolin amount in concrete.
Concrete Research
University of Guilan
2008-4242
1
v.
2
no.
2008
55
63
https://jcr.guilan.ac.ir/article_793_5ebd3427d852e552f6475e32b4572ace.pdf
Evaluation and assessment of debon -ding model in RC beams strength -ened by external bonding of CFRP
hamid
Varastepour
author
text
article
2008
per
One of the important applications of composite material in civil engineering is the strengthened of reinforced concrete beam in situ by an externally bonded carbon fiber reinforced plastic (CFRP). To determine ultimate capacity of these beams failure mechanism and relationships between external load and shear stress distribution at concrete/plate interface must be considered. Different failure mechanisms in this type of beams occur.The failure modes due to the tensile fracture of FRP,the crushing of concrete in compression or the plate separ -ation in the plate/concrete interface. In this paper a parametrical study using the non-linear model is made to obtain the analytical equation capable of calculating the maximal shear stresses at the interface plate/concrete aimed to anticipate the debonding load. And finally for evaluation of credibility of this equation we compared the experimental results obtained by different researchers.
Concrete Research
University of Guilan
2008-4242
1
v.
2
no.
2008
65
73
https://jcr.guilan.ac.ir/article_794_c1edbc2a51f2d5fafe71e8282e38fee6.pdf
Behavior study of concrete joints
M.
Khanzadi
author
Vahid
Ahmadi
author
Behrooz
Hassani
author
text
article
2008
per
In this paper, the effect the FRP reinforcement on concrete connections for increasing shear and bending strength and its ductility is studied.
A nonlinear analysis is carried out by using the ANSYS software and a three dimensional model of the connection under gravitational and lateral loading is considered. By employing different methods of rehabilitation for two typical connect -ions; it is shown is that when the lateral FRP reinforcement fiber of the most are positioned at 45 degrees with respect to bottom of the beam is the most effective foe increasing the shear strength as well as the ductility. Also it is concluded that for beams with a larger amount of longitudinal reinfo -rcement bars, the rehabilitation is relatively more effective.
Concrete Research
University of Guilan
2008-4242
1
v.
2
no.
2008
75
83
https://jcr.guilan.ac.ir/article_795_6fd2cdf55eb329b14e9368834c2e4c3f.pdf