نشریه آنالیز سازه - زلزله
سال هشتم شماره 2 (زمستان 1389)

In order to determine an efficient approach for compound curing of high resistant concertes under saturated/ autoclave medium and studying the influence of saturated situation on reduction of holding time in autoclave, the research was carried out using different curing methods. Concrete specimens which were prepared on standard methods were divided into control and treated ones from which the formers were just exposed to saturated situation(which attained compressive strength of 884.54 Kg/cm2 at 28 days) while the other 3 sets were cured as follows: First and second part were placed under saturated situation for one to three days but the remaining one) was directly transferred to autoclave. All of these 3 sets were maintained in autoclave for 15 to 150 minutes. Results showed that specimens kept in autoclave for 15 minutes (without any maintenance at saturated situation), attained compressive strength of 748.73 Kg/cm2 while in the case of the ones kept at saturated situation for one-day (before autoclave) the compressive strength to 834.71 Kg/cm2 which was about 84.65 and 94.37% of compressive strength of the control sample at the age of 28-days respectively. By increasing the autoclave time to 30 minutes, the compressive strength of the specimens under two circumstances mentioned above improved up to 892.40 Kg/cm2 and 903.51 Kg/cm2 respectively which was about the compressive strength of the check specimen in 28 days. We found no impact on compressive strength growth whenever samples were kept in autoclave for more then one-day

The existence of some geometrically imperfect members, like initial curvature in a double layer space structures with hundreds or thousands of members is almost inevitable. These imperfections give rise to loss of load bearing capacity of double layer space structures. To evaluate the effect of initial member imperfection on load bearing capacity of double layer space structures and their failure behavior, two models of double layer space structures were considered and analyzed nonlinearly by different member imperfection values. The distribution of imperfections was carried out in two ways: 1-uniform distribution, 2- random distribution. In uniform distribution one amount of imperfection was considered and performed to all of the members, but in random distributions, different amounts of imperfections were considered and performed to members and then the structure was analyzed. The results of these analyses were presented with load- displacement figures and they showed loss of overall strength of structures due to initial member imperfections, so that the greater amount of initial imperfection led to increase in the loss of strength. With random distribution of imperfections, results showed 17 to 32 percent loss of strength with respect to the normal condition.

Retrofitting structures is an important issue. Structural weakness may be due to changes in design codes or defects in implementation. Adding structural floors to the existing structures may also lead to the need for strengthening and retrofitting. Retrofitting is possible before the earthquake or may take place as rehabilitation of damaged members after earthquake. Elements such as columns in buildings are vulnerable to earthquakes. Increasing the ductility and load bearing capacity of reinforced concrete columns can be effective in strengthening the entire structures. In recent years several methods for repairing or strengthening the columns have been presented and several theories have been proposed about increasing their load bearing capacity. One of these methods is using reinforced concerte or steel profile jacketing technique. Retrofitting methods also should be applicable and cost effective. This method of retrofitting on weak or damaged columns improves the axial and shear load bearing capacity and increases the ductility. In this research 12 column specimens in small scales were prepared in laboratory and retrofitted using jacketing technique. Load bearing capacity of the specimens before and after retrofitting were calculated and compared. Finally advantages and disadvantages of this method were investigated using experimental test results.

This article deals with a tentative method of concrete compression and the measurement of compressional resistance. The subject of free fall for concrete compression has not received adeqaute attention so far. In this research, the compresional resistance of compressed concrete with free fall is compared with the compressed concrete by trembling bed. To do so, 176 cylinderical testing case with dimensions of 30*15 cm were made. The concrete casting was accomplished in the laboratory of the technical college in 88 stages. Construction of the testing case was on the basis of suggested factors effective on the result of tests including the amount of compression energy, the height and time of fall in every energy, the ratio of water to cement (W/C) and gravel to sand (G/S). All of the testing cases (after testing) were broken under press machinery at the age of 28 days simultaneously. The result obtained from breaking of the free fall and vibrated testing case accomplished by press machinery have been represented in different tables and charts.

During the last few decades, steel shear walls have been adopted as efficient lateral resisting systems for high rise structures and numerous researches have been conducted on their static and dynamic behavior. Steel shear walls have been utilized for retrofitting existing structures, as well as in design of new buildings in japan and USA. In this research, we have focused on the optimization of steel shear walls. Optimization in this research is to increase the proportion of lateral resistance to the weight of steel shear wall panels. For this purpose, three groups of steel shear walls (SSW) with length to height ratios of 5:3, 4:4 and 3:5 were selected. In each group, there was one un-stiffened panel and 5 stiffened walls. The patterns of stiffeners were different for 5 walls. All the SSWs were analyzed by pushover method using the ANSYS code. The analyses show that SSW without stiffener has the highest lateral resistance to weight ratio. Although adding stiffeners increase the lateral strength of the shear walls but decrease the lateral resistance to weight ratio. In this research optimum pattern of stiffeners is discussed and compared to other SSWs.

The most conventional method for lateral bracing of steel frames is using diagonal and x steel braces. In conventional method, braces of frame emplace in one bay or more, relative to structural requirement, from first to last story without displace the braces emplacement on height as columnar form. This pattern is a preliminary and simplest bracing template that the generally codes present based on it. But conventional bracing method isn’t the best bracing template and can’t give the best structural response and behavior. This article purpose is finding the best bracing template to upgrade structural response and efficiency. The optimization is obtained by evaluating several different templates using pseudo-static and time history analysis method. The parameters such as weight, top displacement and period of structures are used to comparison of various bracing frames. All Braced steel frames was designed according to current seismic codes. The results of this study shown the lateral loads distribution and structural response and efficiency for proposed bracing template are upgraded.

In this paper, load and buckling mode of a smart column are presented. The theoretical model is a three-layer piezoelectric composite beam that behaves as an axial actuating mechanism. This actuator consists of an elastic core sandwiched between two piezoelectric active outer layers. The piezoelectric layers are polarized transversely, i.e., the polarization vector is parallel to the applied electric field intensity vector. The finite element models of smart composite are derived by ANSYS. Then, numerical buckling analysis results of composite column are used to train of Genetic programming (GP) intelligent system. Finally, a mathematic formulation is presented for calculation of load and buckling mode of smart column using GP.