نشریه آنالیز سازه - زلزله
سال دهم شماره 1 (بهار 1392)

Regarding the seismic hazard potential of Iran region and the damage exerted on the buildings during previous earthquakes, the developments of seismic engineering and vulnerability of buildings should be further taken into account. Due to the increasing use of reinforced concrete buildings in Iran, three 6.12.18 stories concrete flexural frames with shear wall system were selected and after designing based on 9th capture of Iranian national codes and the 2800 standard code were simulated via IDARC software with the capability of nonlinear dynamic analysis. After choosing the reliable accelographs adjustment with Iran tectonic conditions the damage estimates of these structures were investigated through performing nonlinear dynamic analysis. Note that the Ang-Park damage index was used as a reliable criteria for investigation of seismic response of reinforced concrete systems.

In previous earthquakes, the effect of infill in the structures has shown the importance of modeling and evaluating their influences in analyzing and designing the structures. Different modeling methods have been presented up to now in this field. In this research, the effect of infill with various number of stories is investigated by pushover method. The results of this research reveal that the expected behavior of the structures with and without infill differs significantly. Also with increasing the number of stories, values of initial stiffness, periods, shear values and drift in buildings with infill vary basically in comparison with building without infill.

An experimental investigation of the behavior of retrofitted FRP wrapped exterior beam-column joints under seismic conditions is presented. Also, the experimental study on exterior beam-column joint of a multistory reinforced concrete building under the seismic has been analyzed using ANSYS software. Two specimens were cast and tested to failure during the present investigation. One is control specimen test up to 70% of the ultimate load (without FRP), and another specimen test up to 70% of the ultimate load (with one layer of FRP).The results show that an increase about 18% has been obtained by retrofitting with FRP sheets in load carrying capacity. Also an increase about 54% has been obtained by retrofitting with FRP sheets in cumulative ductility.

In recent years, many researches are focused on optimizing the production of a kind of concrete with high strength and efficiency, and different methods including using fiber technology in concrete construction are proposed to achieve this goal. Fibers are one of the materials that nowadays are added to concrete as reinforcement material. Considering the low weight and good resistance of this material and using a good percent of these materials in lightweight concrete can result in smaller segments with greater resistance. In this paper, we try to study and evaluate the effects of steel fibers on the strength and also the amount of fibers in lightweight concrete. One of the strength experiments is wetting and drying which is used in this study. Also by reviewing dynamic properties of lightweight concrete made with pumice + leca and taftan and comparing with lightweight concrete which is armed with steel fiber, we can achieve the optimal percent of fiber in concrete. Experimental results are presented in graphs and charts.

There are two methods of force distribution and ductility improvement for improving collapse behaviour of double-layer space grids. In the method of ductility improvement, by applying strategies like using force limiting devices for preventing buckling of stress device, structure behaviour will change into ductility behaviour, so the impact of the number of force limiting devices in improving double-layer space grids collapse behaviour is effective until ductility and bearing capacity of structure has a considerable increase. In this article, the optimum effect of force limiting devices number in improving double-layer space grids collapse behaviour is considered according to the effectiveness of limiting devices in increasing ductility and bearing capacity of double-layer space grids from their aspect of number.

Most civil projects applied to heavy vertical and horizontal loads or in lands do not have enough strength against applied load. Despite heavy expenses, it is necessary to use pile. Pile foundations are much more expensive than spread and mat foundations; hence, determining number, dimensions and distances should be done with special care so that these parameters are not determined excessively. For optimized design of pile groups, cost analyses based on settlement equations and bearing capacities to determine number, dimensions and piles distances are necessary. In this research, a computer program has been written in MATLAB language, and by using genetic algorithm which can optimize pile groups design. Outputs of this computer program consist of diameter and length of piles, thickness of pile cap, number of piles and their distances in each direction; therefore, this computer program can design an optimized pile group which tackles technical problems while it is the most economical.

Usually, safety of slip surfaces in embankment dams have been evaluated with 2 peak ground acceleration increasing method and stuff resistance decreasing method are 2 main methods for evaluation of critical bound. In this research, peak ground acceleration increasing method has been used to evaluate stability safety of slip surfaces. In this method, peak ground acceleration has been increased to receiving critical bounds for parameters in time domain (for example permanent deformation, equal dynamic factor of safety, and minimum dynamic factor of safety). To evaluate the effect of this parameter, Masjed Soleiman dam has been selected for a case study. 10 Finite Element model of Masjed Soleiman dam has been constructed considering the Mohr-Coulomb failure criterion for the body of the dam. The 2 earthquake records have been applied horizontally to the bedrock as the input for dynamic analysis without any change in frequency content. Results show that, in critical sliding surface on downstream, with increasing of peak ground acceleration, equal dynamic factor of safety decreased but changing of minimum dynamic factor of safety and permanent deformation have meaningful process.

This paper presents the results of a laboratory study carried out on effect of using microsilis and air entrain on compressive strength of light weight perlite concrete. In this study, 63 test specimens with different percentage and mixtures including microsilis and air entrain were used. 63 test specimens including microsilis were also prepared for comparison purposes. Laboratory test results showed that workability and compressive strength can be increased, and density can be decreased by the use of air entrain and microsilis. These results showed that concrete mixture incorporating 0.5% air entrain and 10% microsilis can be optimum case

This paper presents a new method for the analysis and design of beams and networks. In this method, both the strength and stiffness of the beams as well as the condition of the beam column simultaneously provides the stability condition. Through an example and comparison with available analyses, the efficiency of the method is shown. It can be seen that as a quick, economical and easy method, this method can be used for the analysis and design of beams and columns with different boundary conditions, and other structures including frames and continuous beams.

Today following the development of construction of hydraulic structures like dams, the matter of concrete durability used in these kinds of structures has gained paramount importance. One of the important factors of concrete durability in these structures is its resistance against abrasion due to the crash of particles carried by water.
To enhance the abrasion resistance of concrete, different methods have been offered and investigated by researchers and one can refer to the following to name a few.
Using aggregates resistant to abrasion, reducing the water-cement ratio, using nanocilica microcylis in concrete, suitable and on time seasoning.
In the present research the following experiments have been done on concrete samples.
-The abrasive strength of block samples of 15×15×15 cm for 28 past days using Sand Blast Method.
-The hydraulic conductivity coefficient of cylinder samples with the height of 10cm., and 10cm., in diameter, 28 past days using Penetration Method.
The results of abrasion experiments showed that by reducing water-cementratio from 0.50 to 0.33, the abrasive strength of concrete improves as far as 30.94 %.
The permeability experiments showed that;
By reduction of water-cement ratio from 0.50 to 0.33, the hydraulic conductivity coefficient of the concrete is reduced from 39.88 × 10 m/sec to 2.49 × 10 m/sec., and the porosity of concrete is reduced from 13.90 % to 13.10 %.
The above results show that reducing water-cement ratio results in increasing abrasive strength and increasing the hydraulic conductivity coefficient and reducing porosity of silica fume concrete.