Investigating the size effect of recycled concrete containing steel fibers
Seyed Roohollah
Mousavi
Civil Engineering Department, University of Sistan and Baluchestan, P.O. Box: 98155-987, Zahedan, Iran.
author
yasin
mokhtari
Civil Engineering Department, University of Sistan and Baluchestan, Zahedan, Iran
author
Seyed Hojjatollah
Mousavi
Civil Engineering Department, University of Zabol, Zabol, Iran
author
text
article
2018
per
Utilizing recycled aggregates in concrete makes new feasibility study possible for recirculation of materials in construction industry. One of the considerable points in using concrete is the alteration of mechanical properties by changing specimen size that is called size effect. Compressive strength test was conducted on cubic samples with variable sizes and standard cylinder 15*30. Water absorption and penetrability tests were conducted on 10 and 15 centimeter cubic samples. By replacing the results of compressive strength test in modified Bazantt’s formula and applying linear regression, empirical coefficients of α and β were obtained. By applying these coefficients in the above formula, the ratio of compressive strength of cube sample to standard cylinder was obtained. Examining the results for recycled concrete shows that by increasing the size of specimens, compressive strength declines which suggests the size effect on recycled concrete. In addition, adding 1.5% steel fibers to recycled concrete enhances the mechanical properties and durability. In addition, the size effect and differences between standard cylindrical and cubic compressive strength were decreased.
Asas Journal
Iranian Society of Civil Engineering
2008-7721
20
v.
51
no.
2018
5
15
https://www.isceiran.org/article_81820_d41d8cd98f00b204e9800998ecf8427e.pdf
A meta-heuristic algorithm for solving the time-cost optimization problem with multiple execution modes in construction projects.
Mohammad Javad
Taheri Amiri
Department of Construction Management, Babol University of Technology
author
Farshidreza
Haghighi
Faculty of Civil Engineering, Babol University of Technology
author
Ehsan
Eshtehardian
Department of project management, Tarbiat Modarres University
author
Milad
Hematian
Department of Industrial engineering, Mazandaran University of Science and TeCHNOLOGY
author
Maedeh
Javaheri Barforooshi
Department of civil engineering, Islamic Azad University, Arak Branch
author
text
article
2018
per
In how to balance time and cost is crucial to construction project management. The main specification of time-cost trade off problem is discretization of the decision space to limited and accountable decision variables. In this situation the efficiency of the traditional methods decrease and applying of the evolutionary algorithm is necessary. The clever use of evolutionary algorithms allows us to solve many interesting and difficult problems and our ability to model complex problems increases tremendously. In this article use multi objective particle swarm optimization to solve two construction project management problems. These two projects include 7 and 70 activities with multiple modes. These problems are both in discrete domain including two objectives, separately. In this regard, some procedures has been suggested with solving by optimization algorithm. The developed optimization algorithm has been designed to find the best sequence and mode of operation, making it the shortest time and cost. Results show the advantages and effectiveness of the used procedures in repeating the optimal Pareto for optimization problems.
Asas Journal
Iranian Society of Civil Engineering
2008-7721
20
v.
51
no.
2018
16
29
https://www.isceiran.org/article_81819_d41d8cd98f00b204e9800998ecf8427e.pdf
Evaluation of the capacity of the final tunnel lining under earthquake conditions based on non-linear analysis of the ground structure
rahim
hassani
Department of Civil Engineering, South Tehran Branch, Islamic Azad University, Tehran,Iran
author
Ata
Hojatkashani
Faculty member,Structure and Earthquake group, Department of Civil Eng
Islamic Azad Uni, South Tehran branch
author
text
article
2018
per
Since the analysis of underground structures under seismic conditions is done based on nonlinear ground and linear structures, considering the nonlinear behavior of the soil and tunnel against earthquakes is important in order to achieve real responses. In this regard, in addition to linear analysis, nonlinear seismic analysis of the Tehran Metro tunnel by quasi-static method using ABAQUS software was investigated. The damaged concrete behavior model and mohr-coloumb model were used for tunnel lining and soil in numerical simulation, respectively. The simulations were carried out under three conditions of free field, ovaling, and racking, and at two levels of hazardous earthquake of Operation Design Earthquake (ODE) and Maximum Design Earthquake (MDE). Then, the structural capacity curve and the behavior coefficient for the final tunnel lining were obtained. The results showed that the stresses status and the damage caused to the tunnel lining in each of the three conditions are similar. According to the results of the simulations, behavioral coefficient by considering the importance of the tunnel structure for risk level 1 and 2 were proposed 1-1.5 and 2.5, respectively. The results also indicated that in the linear analysis mode, the tunnel final structure is responsive to the ODE conditions, but it does not suffice for MDE condition. On the other hand, the tunnel lining is safe in the both situations with considering the nonlinear analysis, and applying the behavior coefficient.
Asas Journal
Iranian Society of Civil Engineering
2008-7721
20
v.
51
no.
2018
52
63
https://www.isceiran.org/article_81821_d41d8cd98f00b204e9800998ecf8427e.pdf
Experimental study of bearing capacity of strip footings near the retaining walls reinforced with grid-anchor
Amin
Mohamadiani
Civil Engineering Department, Kermanshah Razi University, Iran
author
جهانگیر
خزائی
عضو هیات علمی دانشگاه رازی
author
Hossein
Moayedi
Associate Professor, Civil Engineering Department, Kermanshah University of Technology
author
text
article
2018
per
Nowadays, the application of a variety of novel reinforcing elements for the design and implementation processes of reinforced soil systems is proliferating. Obviously, it is deserving of note that the selection of the reinforcing element type is of bountiful importance in ameliorating the performance of reinforced soil walls. More latterly, a new type of reinforcing elements labeled grid-anchors conjoining anchors, made up of polymeric substances, with conventional geogrid has been invented, which can generate specific capabilities in reinforced soil walls. In this research, the effect of using grid-anchors on the bearing capacity of strip foundations and lateral deformations of the reinforced soil wall surface in a small-scale laboratory case are investigated. On this purpose, the bearing capacity of a strip foundation resting on a reinforced soil wall and lateral deformations of the wall in unreinforced, geogrid-reinforced and anchor-grid reinforced conditions at differential spaces of the foundation from the wall edge are scrutinized and compared. The results of the experiments disclosed that using anchor-grids in the reinforcement of the reinforced soil wall has resulted in increment of the bearing capacity of the strip foundation locating on the upward parcel of the wall up to 5.5 and 1.5 times in relation to the unreinforced and geogrid-reinforced conditions, respectively. Additionally, anchor-grids can dwindle later wall deformations up to 66% and 16% compared with the unreinforced and geogrid-reinforced conditions, respectively.
Asas Journal
Iranian Society of Civil Engineering
2008-7721
20
v.
51
no.
2018
30
38
https://www.isceiran.org/article_82565_d41d8cd98f00b204e9800998ecf8427e.pdf
Evaluation the Effects of Elements Nonlinear Deformation on Seismic Vulnerability of Irregular Steel Buildings
Abbas
Sivandi-Pour
استادیار دانشکده مهندسی عمران و نقشه برداری، دانشگاه تحصیلات تکمیلی صنعتی و فناوری پیشرفته کرمان
author
text
article
2018
per
Structural damage assessment during earthquakes has always been a challenging problem for earthquake engineers. Evaluation of buildings vulnerability and determination of damage can be an important step taken for rehabilitation. Dissipated energy and deformation in an earthquake are the most important parameters in vulnerability of buildings. In this research, effects of elements nonlinear deformation on vulnerability and damage of irregular steel structures in different earthquake hazard levels has been assessed in three dimensions which have not been considered in recent studies done on seismic vulnerability. The buildings have been considered in different floors with irregular plans. The buildings were modeled in three dimensions with considering panel zone. It is concluded that nonlinear deformation of beams is 70% more than column in life safety performance and nonlinear deformation of columns is 20% more than beams in collapse prevention. Severe damage and collapse due to these parameters occurred in the initial stories of low-rise buildings and in middle stories of high-rise buildings.
Asas Journal
Iranian Society of Civil Engineering
2008-7721
20
v.
51
no.
2018
39
51
https://www.isceiran.org/article_82568_d41d8cd98f00b204e9800998ecf8427e.pdf
Seismic ground response in the presence of underground elliptical soft inclusions subjected to propagating incident SH-waves
Mehdi
Panji
Department of Civil Engineering, Islamic Azad University, Zanjan, Iran
author
farshid
yasemi
Department of Civil Engineering, Zanjan Branch, Islamic Azad University, Zanjan, Iran
author
text
article
2018
per
In this paper, seismic response of the ground surface was presented in the presence of a subsurface elliptical inclusion subjected to propagating incident SH-waves. A numerical approach known as half-plane time-domain BEM that was able to focus the meshes only around the inclusion was used for analysing the problem. After implementing the method in a general algorithm and solving a verification example, a sensitivity analysis was successfully carried out to obtain the amplification pattern of the surface in the presence of a soft elliptical inclusion with considering some key parameters including the ratios of depth, location, shape, impedance and incident wave angle. Finally, by obtaining the maximum amplification of the surface and linear regression from them, the results were summarized in the form of tables and linear equations for engineering applications. The achievements showed that all these parameters were effective in forming different pattern of the ground surface. The results can be practically used in completing the existing seismic codes for heterogeneous domains with underground lenses.
Asas Journal
Iranian Society of Civil Engineering
2008-7721
20
v.
51
no.
2018
64
83
https://www.isceiran.org/article_87885_d41d8cd98f00b204e9800998ecf8427e.pdf