نشریه آنالیز سازه - زلزله
سال هشتم شماره 1 (بهار 1389)

To resist lateral loads in concrete buildings, usually systems such as flexural frame, shear wall or their combinations are used. Using X form of cable bracing in order to strengthen concrete buildings is a new method. This system is more economical compared with the other systems due to cables low weight, high tensile resistance, easy performance and less maintenance problems. In this system pre-tensioned cables are used to increase the stiffness of structure and more reduction in frame lateral displacements. The amount of pre-tensioning has a specific range, exceeding of which does not cause considerable reduction in frame displacements. By modeling and analyzing two one-storey frames using SAP 2000 package, the mentioned range has been discussed and shown. By analyzing more frame structures, it can be said that using cable bracing has reduced considerably the lateral displacements of storeys and also increased considerably frame shear resistant capacity. The results of analyzing of buildings have verified the above mentioned results.

Structural optimization in Civil Engineering is a designing technique that, besides controlling the technical behavior of the structure, should possess the minimum weight. A dome structure is one type that is so applicable in civil engineering purposes. In such structures with a constant span diameter and under a constant distributed loading, determining a minimum weight depends on the location of the joints and a portion of the load applied to each joint. One of the major drawbacks in optimization techniques is a possible convergence of the problem in a local region. Therefore, using a technique capable of overcoming this major problem could be crucial. Genetic Algorithm (GA), a method based on the nature, is a technique which has overcome this problem to some extent. In this research, the objective is to minimize the weight of dome structures with concern to the buckling of all the members, while the height of the layers may vary to its best location in Z direction. Obviously alteration of the joint location will cause a change on the amount of load applied to each joint in order to keep the total loading constant. Also in order to make the optimum shape practical, the new location of the joint will move in the xy plane to fit a parabolic function. Therefore, obtaining the best location of the joints with regard to the defined parabolic function could also be considered as a secondary objective of the paper. The proposed technique was then applied to a number of dome problems and also to a barrel vault. The results obtained were found to be very satisfactory.

Evaluating criteria of nature of forces on structures is an important step in design, construction and utility. In a stochastic phenomenon, the process of the force exerting, are more complicated. Sea waves have such characteristics, where hydrodynamic forces act on hydraulic, offshore and coastal structures. In this paper, the cylinder structure is considered as a system with incoming water wave inputs and the time series of the resultant forces are system’s responses. The experimental data used in this study were collected at a hydraulics laboratory on a full-scale rough vertical cylinders and the capability of system identification and spectral analysis to modeling and prediction of these forces were evaluated and compared. For this purpose, first, a transfer function has been estimated, and then an ARMAX model has been used to capture the dynamics of the process relating in-line forces provided by water waves. Finally, the comparisons between two methods and conclusion have been made.

In this thesis the nonlinear-inelastic behavior of two braced frame systems (special concentric, SCBF, and buckling restrained, BRBF) have been investigated. By choosing sample structures. These structure have been analyzed and designed by current standards, their push-over and cyclic analysis were performed using opensees software. The comparison of results confirms the more stable and ductile behavior of the BRBF. In addition, the effect of initial imperfection of brace element in SCBF and the variation of strain hardening parameter has been verified.

Analysis of composite structures, including space frame structures with concrete shell have been taking meny attention from researchers and different methods is being used for analyzing such structures. In this paper, based on the substructures metod and the theory of equivalent section, analyzing the actual structural model, a transverse strip alone has been analyzed to show that if the structural and loading symmetry can be a single strip from the entire structure or not. For the ease, using the theory of equivalent section, composite structure including steel truss structure and concrete shell can also be changed to a equivalent of truss. On this way, three models including main structure, a single element of structure and equivalent steel truss, modeling and analyzing havebeen done by using SAP. In order to review and compare the results, while using symmetry, the results in four parts of the structure have been evaluated.Then the results of analyzing the models. Have been summarized in the tables and then changed to the graphs.The results show that in analyzing and studying the behavior of composite double-layer barrel vaults, we can make use of the single strip composite truss or its equivalent steel truss in place of the whole structure in case studies.

A growing trend in building in the country, the necessity to move towards sustainable development and, the need for durable buildings and structures and use of indigenous materials made the researchers in this field to study, design and construct materials that, in addition to being economical, build structures with light weight to reduce forces due to earthquakes and to increase earthquake resistance. One of these materials, usually as a factory production and supply to the market, is the building block. Brick and block is the most used masonry and building material in the world so that the bulk of each building by a wall is built , surrounded by the same block and partitioned. Hence, by reducing the weight of blocks, we can significantly decrease the dead weight of the buildings. Concrete blocks usually have high density and because of their structure usually lack thermal and sound insulation. In this research, we have studied the effect of metal fibers in the light concrete to make new light blocks. In addition to thermal and sound insulation, these blocks are light, which increases the shear strength of masonry construction. Then pressure-tensile resistance was tested in order to get the optimum mix design of experiments for manufacturing light concrete blocks containing metal fibers obtained.

Considering the high consumption of cement in construction works and the low amount of cement production to consumption, every year in working season a long number of projects are closed for a long period of time due to shortage of cement, and this substantially imposes damages to civil projects. Limestone as a substitute for part of cement in concrete can decrease the consumption of cement considerably. Fortunately in Iran there are lime-rich mines and it is considered as one of raw materials in production of cement.
In this research, effects of lime as a replacement of part of cement in compressive strength of concrete are studied and the optimum amount of lime consumption is determined. For effects inspection of lime as a substitute for part of the cement in concrete, for three concrete category, C20, C25 and C30 and in each category for lime values 2.5, 5, 7.5, 10, 15 and 20 percent of cement weight and water to the cement ratios 0.45, 0.5, 0.55 0 and 0. 6 cubic samples 15 × 15 × 15 cm were prepared. After reproduction in laboratory conditions,the pressure of samples the age of 28 days were examined pressure and the results were analyzed. For each concrete category and in each water to cement ratio one sample without lime was considered for comparing samples results. The total number of 168 samples were tested and evaluated.