---

Abstract Most structural failures are because of break in consisting materials. These breaks are initiated with crack extension, which is a serious threat to the behavior of structure, so different methods have been developed for distinguishing and showing such cracks. Meanwhile, the new methods based on original wavelet transform are efficient and very important in the subject of signals. The main aim of this paper is to fin the methods capable of distinguishing the specifications of cracks practically. first a modal analysis of the structure was For this purpose, performed using ANSYS software, Then the structure was analyzed as original wavelet using the wavelet toolbox of MATLAB software the results are shown in two dimensional charts of coefficient-position.

---

Abstract: In the present article, the effect of fire on the axial compressive strength of reinforced concrete (RC) columns was studied. Method of research was laboratory investigation. The axial compressive strength of RC columns was measured by applying variable heat in different time intervals in the process of experiment. Thirty two samples of fine-scale RC columns with square and circular cross sections, the gross cross section area of 225 cm² (for both sections), longitudinal reinforcement area of 3.1 cm², general height of 30 cm for all samples and other uniform structural characteristics ( 25 c f   MPa , 300 y f  MPa ) were exposed to fire and different temperatures (300°C to 700°C) were applied in the time intervals of 30, 60 and 90 minutes. Then they were exposed to axial loading by hydraulic jack with 200 ton capacity, and their strengths were measured. It is worth noting that, in the heating stage of samples, caps with thermal insulation were used in order to prevent instantaneous strain at the two ends of the samples. By carrying out the experiments, it became clear that at the time of fire, two factors, i.e., the "period of fire" and "temperature of fire" resulted in the loss of strength in RC columns. Of course, the "period of fire" factor was more effective than temperature of fire. It also became clear that RC columns with circular cross section fail faster in comparison with the columns with square cross sections at the time of fire. In order to evaluate and measure the results obtained, a relative factor called "Fire Factor" was utilized. The results indicated that the amount of axial compressive strength loss resulting from fire is approximately 3-5% greater in circular RC columns in comparison with square columns.

---

  The main aspect of this research study is investigation on scour phenomenon around marine pipelines with respect to submerged impermeable plates beneath the pipe. So far, numerous investigations have been done but the main difference of this study with them is installation an impermeable base plate under the pipelines. Installing these impermeable plates mainly causes that the developed streamlines under the bed, located under the pipeline, are lengthened and accordingly the pressure gradient reduces across the pipe. Reduction of the pressure gradient may be considered an important issue since one of the most important criteria of establishing and progressing of scour under pipelines is the formation of piping phenomenon under the pipelines. This phenomenon is due to dominance of the pressure gradient on floating weight of the bed materials. For this research study, firstly scour phenomena under the pipelines were investigated both for unprotected pipelines and protected pipelines with submerged impermeable plates, with the piping phenomenon under the pipelines were being considered for both cases. The experiments were carried out in a channel with 10m length, 0.25m width and 0.5m depth. P.V.C. pipes with four diameters (i.e., 2cm, 3cm, 4cm and 5cm) and 0.5cm thickness were investigated. The bed materials were consisted of sediment particles with median size of 0.50 mm and geometric standard deviation of 1.43. The specific gravity of bed materials was 2.65. All experiments were run at clear water conditions. For each test the steady approach flow was adjusted so that the ratio of velocity to critical velocity was equal to about 0.85 on the centerline of the flume. A number of rectangular galvanized iron plates with 25cm in length, 0.7mm thickness and various dimensions of breadths were selected as countermeasure tools for scouring phenomenon. Then, the scour depth beneath two parallel pipelines with side by side arrangements and their interaction on scouring process were investigated. Finally, with installing impermeable base plates under the pipelines, the effect of these plates on scour phenomenon were studied for any arrangements of the parallel pipelines. The experimental results showed that installation a plate under the pipeline could prevent the formation of scour hole to some degrees and protect them from scour hazards. For all test cases of unprotected pipelines, the maximum dimensionless scour depth beneath the pipelines decreased when the pipe diameter increased. For side by side arrangement of two parallel pipelines, the formed scour depth decreased when the distance of pipelines increased. Then, for practical purposes, in order to reduce the maximum scour depth it is recommended that the distance of two parallel pipelines increases as far as possible or a submerged base plate may be used beneath the under pipeline. For all test cases of pipelines with impermeable base plates, the scour process will not further occur unless due to wake vortices

---

Most of structural failures are because of break in consisting materials. Beginning of these breaks is with crack which extension of them is a serious threat to behavior of structure, so the methods of distinguishing and showing of cracks are most important subjects which are being investigated. In this article, a new smart portable mechanical system to detect damage in beam structures form using fuzzy-genetic algorithm is introduced. Acceleration-time history of the three point of beam is obtained. The signals are then decomposed into smaller components using new EMD (Empirical Mode Decomposition) method with every IMF containing a specific range of the frequency. The dominate frequencies of the structure are obtained from these IMFs using Short-Time Fourier transform. Subsequently, a new method of damage detection in simply supported beams 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 location and severity of the damage along the beam, which can detect the damage location and severity based on the pattern of beam frequency variations between undamaged and damaged states.

---

---

Abstract

Rotational friction dampers are a specific type of friction dampers which have several advantages. Dampers are used to improve the cyclic behavior of structures against forces caused by wind and earthquake. These types of dampers will cause energy dissipation by its rotating and rerotating. However, complete and comprehensive researches have not been performed on the effect of rotational friction dampers and their effect on the bearing capacity of steel frames. In this research, the behavior of concrete-filled steel tube (CFT)  in two cases frame braced with rotational friction dampers and frame braced without rotational friction dampers is investigated. For verification, the results obtained from finite element method software, ABAQUS, were compared with that of experimental studies for test samples used in a building with a height of 300m in Osaka, Japan. The hysteresis curves of the modeled samples are in good agreement with the experimental results.

In order to investigate the performance of steel composite frame (with CFTs) braced with rotational friction dampers towards to steel composite frame (with CFTs) braced without rotational friction dampers  under the effect of three earthquake Far-field records, the structure was modeled, designed and analyzed in ETABS software. The use of bracing with rotational friction dampers has caused a decrease in the displacement of the roof’s center of mass for each record mentioned above which modeled in ETABS software. It decreased by 13 to 49 % for 9 records and increased by 2 to 17 % for 2 records. The use of bracing along with rotational friction damper modeled in ABAQUS software under the effect of each record has caused a decrease in base shear. The extent of these reductions was different for each record mentioned above. In each record modeled in ETABS software, the base shear of the structure has not reduced similarly; however, in some cases, the base shear has increased. It had a decrease of 11 to 37% for 7 records and an increase of 3 to 26% for 4 records.

 Then a Single-storey frame with single-span With the same materials and specifications introduced in ETABS software in ABAQUS software Has been modeled. For lateral loading of columns, the lateral loading protocol based on ATC-24 and the instructions for using dampers in the design and reinforcement of buildings have been used.
 According to Regulation No. 766 of the Program and Budget Organization, the loading cycles introduced in ETABS software with a frequency of 1.15T have been used in the ABAQUS Limited Components Software to move. The use of rotary braces and crankshafts in the ABAQUS limited component software under the influence of each of the discussed records has reduced the displacement of the structure relative to the structure without braces and without rotational friction dampers of the structure mentioned above was exerted under the record effect of the same earthquake in ABAQUS software The use of bracing along with rotational friction damper modeled in ABAQUS software under the effect of each record has caused a decrease in base shear. The amount of energy reduction for records understudy was not equal and varied from 8% to 34.7%. The hysteresis curves of base shear of braced structures with and without dampers are well presented.

---

Reinforced concrete structures with standard steel rebar are vulnerable to corrosion and harsh environmental conditions, hence RC structures reinforced with fiber-reinforced polymer (FRP) rebar were commonly used these days. Du to FRP rebar’s better performance such as high strength, low self-weight, electromagnetic transparency and, as mentioned, non-corrodibility nature, using them as reinforcing bar is very widespread now. Because of financial matters, between different kinds of FRPs, GFRP is a better choice. Considering GFRP’s high strength and elastic behavior until failure, Although a large amount of reinforcement ratio is needed in composite beam components, the flexural stiffness of GFRP rebar reinforced beams is relatively lower compared to steel-RC, and more deflection and cracking are allowed in the serviceability design of these beams. Recently, shear and flexural behavior of continuous concrete beams reinforced with GFRP bars has been well investigated. Because of linear elastic behavior of GFRP materials until failure, considering moment redistribution in analysis and design of these beams is not allowed in almost all of cods and guidelines. Although many experimental and numerical researches investigated the moment redistribution in FRP-RC continuous beams with rectangular section, the behavior of these beams with T-section is almost unknown. This paper is a numerical investigation of existence and variety of moment redistribution in concrete continuous T-section beams reinforced with GFRP bars using finite element method with ABAQUS software. The verification of numerical models was done with some experimental beams, so the simulation can be used for further researches. The considering variables included the longitudinal reinforcement percentage, the number of main bars with constant bar ratio, transverse reinforcement ratio, stirrup space with constant ratio and constant bar size. For investigating mentioned parameters, 35 beams were modeled in software according to Canadian design and construction of building structures with FRP code, so 5 groups of beams were made which one beam is constant in each group. T-section beams were modeled assuming which failure happens because of concrete crashing not rebar failure. Deflection and serviceability were not interested, so bond-slippage behavior of GFRP rebar with concrete is not considered in modeling. Problem is indeterminate, so the percentage of moment redistribution was determined by comparing the reactions resulted from numerical and elastic analysis. Load-deflection and load-moment redistribution curves were used to discuss. The results show, as there is in steel-RC structures, moment redistribution exist in GFRP-RC continuous beams with T-section; however the amount of it is lower. Amount of bars between 2.5 times of balance reinforcement ratio and 3.5 times of it, in top and bottom of beam, shows the highest flexibility load and moment redistribution capacity. Increasing the number of main bars with constant reinforcement ratio and increasing the stirrup space with constant transverse reinforcement ratio reduce the moment redistribution capacity. It seems that the minimum amount of transverse reinforcement considered in Canadian code is not enough for preventing shear failure in these beams. So, with considering some points, the moment redistribution can be taken to account in analysis and design of GFRP-RC continuous beams with T-section.