JOURNAL OF STRUCTURAL AND CONSTRUCTION ENGINEERING
Year:2016 | Volume:2 | Issue:4|Papers Count:10

Dual system of steel moment frame and steel plate shear wall has many advantages in comparison to the other systems. Since the last four decades the dual system has been used more frequently in new and existing structures. the steel shear wall has many advantages such as high ductility, strength, stiffness and it has light weight, it consequent reduce lateral forces and time efficiency in contracture procedure. The aim of this study is to evaluate the seismic performance of the dual steel frame steel plate shear wall system in comparison with the moment resisting frame using nonlinear dynamic analysis. A dual System of Steel Moment frame and steel Plate shear walls system and a moment resisting frame is chosen a frame of four stories building were designed by used existing code. The height of each floor is 3.5 m. Seismic behavior of frame evaluate using nonlinear dynamic analysis. For this purpose a set of seven earthquake ground motions were appropriately selected and applied to the systems. Interstory drift ratio, input energy, distribution frames responses in height were compared for the systems under two different hazard level of ground motion and the results were analyzed.

In this investigation, seismic response of steel structures utilizing Cylindrical Frictional Dampers (CFD) is studied. CFD is an innovative frictional damper which comprises two principal elements, the shaft and the hollow cylinder. These two elements are assembled such that one is shrink-fitted inside the other. If the damper’s axial force overcomes the static friction load, the shaft inside the cylinder will move and results in considerable mechanical energy absorption. To assess the efficacy of CFD 6 story steel frame are constructed and analyzed. Nonlinear time history analyses are applied to the frames and clear distinction has been drawn between the frames comprising CFD and the counterparts without CFD to emphasize the effectiveness of CFD in altering seismic responses. The results show that CFD extremely improves the seismic response of the structure. Considering that we can install this damper in various situations to absorb energy, the behavior of this damper is evaluated in these situations. Response of structure (such as displacement, base shear, etc) represents the best and most effective position and optimal situation of the damper which is in diagonal brace.

Truss model is an analytical approach to predict the strength of reinforced concrete members with geometric or statical discontinuous regions. This study investigates the use of truss model to predict the structural behavior of reinforced concrete members with discontinuity areas under monotonic loading. The estimated failure load and its corresponding deformation are the main objective of this research. Twenty and three samples including short shear walls, short columns and deep beams tested by other researchers throughout the literature have been selected. Then their truss models as well as their three dimensional finite element models are analyzed using ABAQUS software. The comparison of experimental and analytical results shows fair correlation between them. Also, the structural response of samples estimated by truss model analysis is fairly acceptable.

Direct Displacement-Based Design (DDBD) is a performance-based seismic design method that has been proposed and developed over the past two decades for RC frame structures, shear walls and bridges design. The aim of this study is to evaluate overstrength of EBFs with short, intermediate and long link beams designed according to the DDBD method. For this purpose, twelve EBFs with 3, 5, 9 and 12 stories having short, intermediate and long link beams designed using the DDBD method. To investigate the seismic behavior of the considered EBFs, it is first necessary to model properly the nonlinear cyclic behavior of link beams properly. In this regard, the macro-model developed and proposed by Richards was utilized in this study to simulate the nonlinear behavior of some tested link beams available in the literature. After validating the finite-element model, the seismic behavior of the considered EBFs was studied using nonlinear static analyses. The results show that the overstrength factors of the DDB designed EBFs are variable depending on their links length ratio and may even be less than the factor proposed in the DDBD method (i.e.1.5). This factor was evaluated as 1.51, 1.37 and 1.19 for the investigated EBFs in this study with short, intermediate and long link beams, respectively.

This study aims to investigate distribution of earthquake lateral load along the building’s height of moment resisting frames, considering the structure nonlinear effects. For this purpose several case study steel frames including 3, 7, and 15 story frame -which are common for urban areas- are considered. These frames are designed according to Iranian standard codes for steel buildings and Iranian seismic code of practice (Standard No 2800), using the standard equivalent static procedure, for a soil class of II. Thereafter considering seven earthquake ground-motion scaled records, a nonlinear dynamic analysis for each of frames was performed and distribution pattern of shear force was extracted in frame elevation. In order to take out a certain and reliable lateral load pattern, the incremental dynamic analysis is used and results are averaged. Eventually considering the effective factors in distribution of earthquake lateral load along the height, the extracted load pattern is simplified and formulated to be practicable. The presented equation shows 95% correspondence with the dynamic analysis results.

Fluid conveying pipe used in different fields such as petrochemical, oil, gas, hydraulic structures in transmission lines. The damage caused by vibrations damaging pipes or other components of a power plant industrial plants are related to each other, one of the main reasons for the loss of production time is considered damage and ultimately fires in industrial plants. So make a way as to identify damage in the fluid conveying pipe is of particular importance. The purpose of this study, the effect of the fluid inside the pipe vibration characteristic is a theoretical approach. Then for forced vibration analysis of fluid pipe considered passes through the external moving oscillator. And then a method to detect damage in pipes recommended based on fuzzy-genetic algorithm. First, fluid conveying pipe dynamic equations, modeled interaction between external moving, pipe and fluid then solving vibration system, acceleration time history extracted from midpoint of pipe. Subsequently, a new method of damage detection in simply supported pipe is introduced based on fuzzy-genetic algorithm. The new method is capable of identifying the location and severity of the damage. This algorithm is developed to detect the damage location along the beam, which can detect the damage location based on the pattern of beam frequency variations between undamaged and damaged states. The severity of damage is assessed based on quantitative variations in frequencies.

The selection of the most appropriate project for the investment is one of the most important decisions that should be made by the private investors. This problem is of vital importance in BOT projects, where the total investment as well as the investor's profit should be recovered by the project's income. There are several approaches proposed by the researchers to determine the best economical project in comparison to other projects. The previous researches, however, faced with some major defects. As an example, the effects of various factors affecting the project evaluation process as well as the existing risks and uncertainties are not taken into account. In this research, economic assessment of BOT projects is performed by integrating system dynamic simulation approach and fuzzy logic. For this purpose, first the project's NPV is modeled considering all the influencing factors qualitatively. The relationships that exist between different factors are then determined and the quantitative model is built. Using the developed model, the value of NPV is simulated considering the effects of all the influencing factors and the existing uncertainties. Finally, the value of project's NPV is determined as a triangular fuzzy number. Finally, the best alternative project is selected by comparing the simulated values of NPV. To evaluate the capabilities and performance of the proposed model, the project economical evaluation is performed for two highway projects and the best project is selected.

In the recent years, damage detection of structures has been one of the active research areas in sensitivity analyses. There are various responses to determine the location and extent of damages in structures which one of them is deformations caused by dynamic stimulation of time history. In this research, artificial acceleration mapping, which is used in time history analyses, produced in agreement with earthquake properties by using wavelet functions. The approach which was used for damage detection was sensitivity based damage detection. Joint deformations caused by artificial acceleration mapping in structures were inputs of damage detection problem. In this research to show the capabilities of artificial acceleration mapping, two numerical cases were studied. Results indicated that artificial acceleration mapping not only was efficient in damage detection, it was more accurate than natural acceleration mapping.

Ground motions recorded in near-fault sites, where the rupture propagates toward the site, are significantly different from those observed in far-fault regions. In this research, finite element modeling is used to compare the effects of near- and far-fault ground motions on a system consisting of soil, pile group and structure, considering the possibility of non-linear behavior for the structure. The Von Wolffersdorff hypoplastic model with intergranular strain concept is applied for modeling of granular soil (sand). Five fault-normal near-fault ground motion records and five far-fault ground motion records, recorded on rock, are applied to the model. The results show that when seismic waves pass through the soil layer, the fundamental period of the soil layer lengthens, due to non-linear deformations. Also, in near-fault pulse-like ground motions a displacement pulse is generated in the pile response. Whereas, in the far-fault ground motions, due to the more uniform distribution of energy during the record, such pulse-like displacements are not observed in the pile response. Based on the obtained results, for a constant PGA, there are positive correlations between the values of maximum pile displacement, and PGD and PGV values of near-fault ground motion records. But such correlations are not observed in the case of far-fault ground motions.

Ductility, over-strength, material properties and design methodology are the factors affect the reduction rate of the lateral strength of structure in nonlinear region. These factors are introduced as Seismic Performance Parameters, SPP, in technical literature. In seismic codes, the behavior factor, which defines corresponding to the lateral resisting system, covers the aforementioned parameters. Although the R-factor is proposed experimentally, but it could be calculated by means of analytical models in two categories which are demand and capacity R-factor. However, reviewing previous studies reveal that less attention has been paid to the effects of near-fault pulse type earthquakes on R-factor. Therefore, in this study, the SPP is calculated by conventional and advanced pushover methods and the results are compared with the R-factor proposed by Standard 2800-Ver.3. In addition, the effect of load patterns on SPP and capacity curved are considered. The result of this study shows that the proposed R-factor by Standard 2800-3rd for steel special moment frames is conservative for low-rise structures. Increasing the height decreases, the capacity R-factor thus using the R-factor of standard-2800 is inaccurate. The conventional load patterns have no considerable effect on capacity R-factor. In addition, the average of global ductility is about 2 for all models and it is almost independent of the analysis method. At the end, the demand R-factor resulted by near-fault pulse type ground motions is between 0.2 and 0.4 of the value proposed by standard-2800. Therefore, using R-factor introduced by standard-2800 is conservative for the elastic design procedure.