جستجوی مقالات مرتبط با کلیدواژه "coupling beam" در نشریات گروه "عمران"

So far, various elements have been introduced for modeling concrete shear walls, which are classified into two general categories: microscopic and macroscopic. Compared to microscopic elements, macroscopic elements have less degrees of freedom and therefore require less time for analysis. This is the main advantage of these elements. In this article, a special type of macroscopic elements called Multiple-Vertical-Line-Element-Model (MVLEM) is used to model the concrete shear wall. These elements simulate the behavior of simple shear walls well, but when the opening is embedded in the wall, it does not work satisfactory. In this article, the modified MVLEM is used to model the concrete shear wall with asymmetric openings. For this purpose, an experimental concrete shear wall with asymmetric openings was selected and verified using the microscopic finite element method in Abaqus software. After validation, the shear wall was subjected to macroscopic modeling in Abaqus software. In this model, a method for macroscopic modeling of the coupling beam was proposed, which is based on the moment distribution diagram in the beam. When the wall is subjected to lateral loading, due to its geometric shape, the amount of moment on one side of the beam is almost zero and on the other side it is maximum. In simple concrete shear walls under lateral load, the amount of moment at the top of the wall is zero and at the bottom is maximum too. Therefore, the coupling beam can be considered as a simple shear wall. In the shear wall with asymmetric openings, the coupling beams are modeled as simple shear wall whose base is connected to the main wall. After modeling the coupling beam, three different methods were proposed to connect this beam to the main body of the wall. This research includes a microscopic wall with asymmetric openings, three macroscopic walls. The main difference between the macroscopic walls is in the way of connecting the beam to the shear wall, which is based on the difference in the stiffness of the connection. In order to check the accuracy of the proposed models, macroscopic and microscopic walls were subjected to static and quasi-dynamic loading. Based on the results of the aforementioned analyses, the models showed acceptable behavior. The amount of connection stiffness caused the behavior of macroscopic models to be different from each other. Based on the results, as the stiffness of the beam to the wall increases, the bearing capacity and elastic stiffness of the model increases and the ductility decreases. The degree of stiffness of the connection also affects the cyclic behavior of the wall. In such a way that the higher the stiffness of the connection, the greater the loss of carrying capacity is observed in cyclic loading. In the model whose stiffness is higher than the other models, it experiments a large resistance drop in the ninth and tenth cycles. In the model whose stiffness is less than the others, less drop is observed and it shows a soft behavior. The model in which the connection stiffness was in the middle level showed the most accuracy compared to other models.

Though steel shear walls have proven effective, they are limited due to the opening on their bay. To address this, coupled shear walls can be used. Consequently, there has been widespread use of corrugated sheets in the steel shear walls for low- and mid-rise buildings. However, there are limited studies on coupled shear walls. Hence, as a symbol of low- and mid-rise buildings, this study utilized Abaqus software to model samples of coupled steel shear wall 3-, 6-, and 12-story buildings. Under push over-analysis of up to 4% roof drift, the study investigated how trapezoidal corrugated steel plate with vertical and horizontal waves impact four key factors: bearing capacity, energy dissipation, degree of coupling, and behavior coefficient, and ductility ratio of the coupled steel shear wall. In the models, the study assessed the effect of increasing both the cross-sectional area of coupling beam and coupling beam's length. The results demonstrate that vertical and horizontal corrugated sheets cause a reduction of three factors: the base shear, degree of coupling, and energy dissipation. Besides, behaviour coefficient and ductility ratio decreases in the vertical corrugated sample and increases in horizontal corrugated sample. Furthermore, increasing the beam's length or cross-sectional area causes a decrease in four factors: the bearing capacity, coefficient of behaviour, ductility, and energy dissipation ratio. The degree of coupling decreases in the vertical corrugated samples and increases with the horizontal wave. Moreover, the degree of coupling increases in both cases of flat and corrugated steel sheets, increasing the number of stories.

The strong earthquakes recorded worldwide have shown that the damages and the failure mechanisms of the reinforced concrete structural walls depend on a series of factors, such as the shape in plan and elevation, the dimensions of the walls and openings. During the past several decades, extensive experimental and analytical studies have been conducted on the behavior of structural walls with openings. This article describes an Analytical study carried out on of reinforced concrete walls with eccentric opening. In order to achieve this goal, variations in various parameters including changes in the aspect ratio of the openings, the stiffness of the link beam, the aspect ratio of the openings with simple connection at the both end of link beams and the aspect ratio of the walls are studied. Story drift, center of mass displacement, shear and moment in coupling beams and axial load in columns which coupled with shear wall are analyzed and compared together. The results show that by decreasing the aspect ratio of the openings (ho/lo), the axial load in the column coupled with the wall decreases and with increasing rigidity of the link beam the shear forces in link beam increased and center of mass displacement and story drift are reduced. The strength of structural wall components becomes different in pull/push loading direction due to the eccentric opening location. Also, compared to seven buildings, decreasing the wall aspect ratio from the axial forces in the column and shear forces in the link beam decreases.

Retrofitting coupling beams in shear walls to improve their seismic performance can be a viable option. Fiber reinforced polymer (FRP) composites are widely used in strengthening reinforced concrete (RC) structures. This paper aims to investigate and compare the result of shear strengthening of reinforced concrete coupling beams by means of CFRP & GFRP sheets, with externally bonded reinforcement (EBR) method and GFRP rods, with near surface mounted (NSM) method, using ABACUS software. Hence, numerical studies were conducted to analyze these methods. The results show that using FRP composites can increase the shear strength and ductility of strengthened coupling beam, effectively. In EBR method, carbon and glass fiber sheets are more effective to increase the strength and ductility, respectively. The NSM method increased the shear strength by 44% and also the ductility by 70%.

HPFRCC is the materials including cement mortar, aggregate, and fibers which represent strain hardening within tensile load. The HPFRCC can be used in numerous cases such as seismic rehabilitation of structural members. One of the structural members is the existed coupling beam in coupling shear walls which is applied as shear fuse. Using the materials in the members can enhance ductility and energy absorption and also delays failure. This paper investigates a study on the effect of existence of diagonal reinforcements and spirals of diagonal reinforcements of the coupling beam. For this purpose, three prototypes of coupling shear walls with coupling beam were designed by HPFRCC with length-to-depth ratio of 2 and 1/2 scales. The first prototype is considered as reference and we use concrete with reinforcement design based on ACI 318-08 code. The other prototypes are built by HPFRCC with PPS fibers. But in one of them the spiral of diagonal reinforcements and in the other both spirals and diagonal reinforcements are omitted. In order to simulate the test set-up with real behavior, two strong walls were considered and cast at both sides of coupling beams. The rotation of these walls should be prevented, so in the experimental set-up, vertical small steel column in addition two strong steel roller were considered during tests. The several strain gauges were installed on longitudinal and diagonal and vertical bars to measure the strains during tests and particularly showing the displacement and load of yielding points of reinforcement. LVDTs were installed to measure the maximum displacement of the tip of beam and also to measure probable rotation. The drift if the ratio of the tip displacement of the specimen to the beam length and the ductility is the ratio of ultimate displacement to the yielding displacement and finally the energy absorption is the area under load-displacement cure for each separate cycle.
Results are indicating of appropriate effect of HPFRCC concrete in enhancing ductility and energy absorption capabilities and it can also reduce diagonal reinforcements. In addition improved crack pattern and shrinkage of cracks represent an appropriate participation of fiber in increasing the shear capacity. Comparing these prototypes, it is found the one in which spirals were omitted load capacity¡ ductility factor¡ energy absorption and failure displacement capabilities have been increased 15%, 36%, 69%, 35%. And the prototype in which diagonal reinforcements were omitted, has decreased load capacity down to 36% and ductility factor and failure displacement have been increased up to 13%, 35% and finally energy absorption has no changes. The pinching loops of load-displacement hysteresis curves of specimens were compared and the results indicated that the pinching of HPFRCC specimen was reduce comparing to reference specimen even in case of omitting the spiral. The stiffness slope of each specimen was calculated and results showed that the HPFRCC specimen with diagonal bars had more 8 percentage but the stiffness of HPFRCC specimen without diagonal bars was reduced up to 60% comparing to reference regular concrete specimen. Elastic experimental shear capacity of specimens was about 5 times of elastic Design code (ACI) shear capacity because the shear capacity calculated by ACI is conservatively only based of diagonal bar shear capacity.

A coupling beam is a type of beam for connecting two adjacent shear walls, with a functioning similar to that of eccentrically braced steel frames (EBF). Seismic characteristics of various types of coupled beams such as diagonally reinforced concrete coupling beam (DBCB), steel coupling beam (SCB), composite steel/concrete beam utilising a vertical web shear plate with headed shear (SPCB), and steel beam with a steel fuse link located at mid span of the beam (FCB) are studied (Fig. 1). Pushover analysis has been performed for chosen frames of up to 20 storeys in order to determine reduction factor as a function of overstrength factor, ductility factor and indeterminacy reduction factor. In this research, novel relations have been proposed for calculating reduction factor, which include the effect of the type of soil and height of the structure. Four 5-, 10-, 15- and 20-storey frames with 3 m-high storeys and five spans have been analysed. There are four concrete bending frame spans, each 5 m long, and a 4 m-long span with two coupling core wall, each 1.4 m long, and a 1.2 m-long coupling beam. ETABS code [1] has been used for the design of structural members, pushover analysis, and the determination of overstrength factor, ductility factor and indeterminacy reduction factor by which reduction factor can be calculated. The effect of four different types of soil has been considered. Effect of variable parameters on reduction factor In order to investigate the effect of variable parameters on reduction factor, two types of frames, i.e. intermediate and special bending frames, four numbers of storeys, i.e. 5, 10, 15 and 20 storeys, and four different types of soil, i.e. types I, II, III and IV [2], have been considered. The sequence of member stiffness increase is from coupling beams towards beams, columns and shear walls and it is more pronounced for lower frames. By increasing the height of the frame, the reduction factor calculated by the proposed equations is decreased until it coincides with the value proposed by the Iranian Earthquake Code [2]. For points higher than the coincidence point, reduction factor is on the safe side. For looser soils, the value of reduction factor increases slightly for points lower than the coincidence point and it decreases slightly for points higher than the coincidence point.