Reza Aghayari - Academia.edu (original) (raw)

Papers by Reza Aghayari

Structural Durability & Health Monitoring

This paper deals with the modeling of punching shear failure in reinforced concrete slabs using n... more This paper deals with the modeling of punching shear failure in reinforced concrete slabs using nonlinear finite element analysis. The 3D finite element analyses (FEA) were performed with the appropriate modeling of element size and mesh, and the constitutive modeling of concrete. The FE numerical models are validated by comparing with the experimental results obtained from tested specimens and previous research. One slab served as a control without any modification while three slabs were strengthened. The ultimate behavior of FRP strengthened RC flat slabs under a centrally applied load. Each method of repair or strengthening is reviewed with emphasis on its performance with respect to the application details. The punching shear capacity, stiffness, ductility were investigated. In addition, the analytical results were compared with the predictions using the provision of ACI 318-08. The results showed that for control slab and strengthened specimens an increase varied from 4% to 105...

International Journal of Civil Engineering, 2012

Strut-and-Tie Model (STM) can be used to model the flow of compression within a concrete strut. C... more Strut-and-Tie Model (STM) can be used to model the flow of compression within a concrete strut. Concrete struts are formed in various shapes such as prismatic or bottle-shaped. In order to study the behavior of concrete struts, a series of simple tests were performed. Eighteen reinforced concrete isolated struts with compressive strength of 65 MPa were tested up failure under point loading in the plane of specimens. The tested specimens were reinforced by various reinforcement layouts. The behavior of tested beams was investigated. Observations were made on transverse displacement, primary cracking and ultimate failure load and distribution of strain on the face of tested panels. Based on these observations, the geometry of the concrete struts was examined. a new model to analysis of concrete struts was proposed based on modified compression field theory (MCFT). A database of 44 tested specimens was compiled to evaluate the proposed model. The results indicate that using the ACI and...

In this paper a new method based on Strut-and-Tie Model (STM) is proposed to determine the shear ... more In this paper a new method based on Strut-and-Tie Model (STM) is proposed to determine the shear capacity of simply supported RC deep beams and an efficiency factor for concrete with considering the effect of web reinforcements. It is assumed that, the total carried shear force by RC deep beam provided by two independent resistance, namely diagonal concrete strut due to strut-and-tie mechanism and the equivalent resisting force resulted by web reinforcements, web reinforcing reduces the concrete compression softening effect with preventing from the diagonal cracks opening or concrete splitting. The unknown function and parameters are determined from 324 experimental results obtained by other researchers. To validate the proposed method, the obtained results are compared with some of the existing methods and codes such as ACI 318-05 and CSA. The results indicate that the proposed method is capable to predict the shear strength of variety of deep beams with acceptable accuracy.

RC coupled shear walls are known as one of the best and popular lateral load resisting structural... more RC coupled shear walls are known as one of the best and popular lateral load resisting structural systems. Most of the structural design codes have no seismic design considerations for base shear and fundamental vibration period. In current study finite element models were generated to provide a reliable data base to estimate the base shear and fundamental period. The differences between the behavior of in-plane and out-of-plane actions in these systems were investigated. In the final stage corrective coefficients will present according to analyses results. More accurate estimation of the demand makes more resistant structures against wind and earthquake loads.

Civil Engineering Journal

Given the burgeoning demand for construction of structures and high-rise buildings, controlling t... more Given the burgeoning demand for construction of structures and high-rise buildings, controlling the structural vibrations under earthquake and other external dynamic forces seems more important than ever. Vibration control devices can be classified into passive, active and hybrid control systems. The technologies commonly adopted to control vibration, reduce damage, and generally improve the structural performance, include, but not limited to, damping, vibration isolation, control of excitation forces, vibration absorber. Tuned Mass Dampers (TMDs) have become a popular tool for protecting structures from unpredictable vibrations because of their relatively simple principles, their relatively easy performance optimization as shown in numerous recent successful applications. This paper presents a critical review of active, passive, semi-active and hybrid control systems of TMD used for preserving structures against forces induced by earthquake or wind, and provides a comparison of the...

Scientia Iranica, Aug 1, 2017

This paper investigates the seismic behavior of RC shear walls strengthened by Fiber Reinforced P... more This paper investigates the seismic behavior of RC shear walls strengthened by Fiber Reinforced Polymer (FRP) composites. In this research, the e ects of strengthening shear walls with di erent strengthening schemes and also strengthening walls with openings in di erent dimensions and locations are studied. The development of nonlinear niteelement methods has improved the accuracy of seismic analysis of complex structures. In this study, the ABAQUS software is used to investigate the nal resisting parameters, ductility, and behavior factor in these walls using nonlinear static analysis. The ndings prove that the applied strengthening schemes increase the nal strength of the wall. Also, the increasing ductility, behavior factor, and increased overstrength factor in some of these walls compared with original walls are observed. The ndings also prove that special openings with limited dimensions to improve seismic behavior of the wall are e ective, and the only limitation of using these openings is decreasing the nal strength which can be made up by using a proper strengthening scheme of FRP.

KSCE Journal of Civil Engineering

Steel Shear Walls (SSW) in buildings are known to be an effective means for resisting lateral loa... more Steel Shear Walls (SSW) in buildings are known to be an effective means for resisting lateral loading. By using un-stiffened walls and allowing them to buckle, their energy dissipation capacity will increase significantly due to the post-buckling capacity. The features of this system are being economical, quick and easy construction, low weight compared to similar systems, high ductility, high energy absorption and substantially reducing residual stress in structures. New methods and technologies obtained in the field of metals have provided new steel materials (LYP) to that has lower yield strength than conventional steel A36. This type of steel material shows the ability to deform and absorb more energy before failure. In this study the behavior of reinforced concrete frames braced with steel shear walls (LYP) was investigated and compared with other medium and high strength steel with different thicknesses. A nonlinear pushover analysis was performed. The effect of thickness of steel plate on the response modification factor was investigated. The results show that the lateral load capacities of RC frames braced with steel shear walls increase significantly and the response modification factors of RC frames braced with thin LYP steel plate is higher than the other systems.

KSCE Journal of Civil Engineering, 2016

Among the retrofitting techniques available, steel braces can be considered as one of the most ef... more Among the retrofitting techniques available, steel braces can be considered as one of the most efficient solution for seismic performance upgrading of RC frame structures. Added Damping and Stiffness (ADAS) elements are designed to dissipate energy thought the flexural yielding deformation of mild-steel plates. The current paper deals with the response ductility and the modification factors (R) of bare RC frames, RC frames with chevron steel braces, and RC frames with steel slit dampers (SSD). For this purpose three RC frames of 8, 12 and 20 stories were analyzed without considering the existence of dampers, then each frame equipped with a SSD was studied. A nonlinear pushover analysis was performed. The results show that the response modification factors of RC frames equipped with steel slit dampers is higher than the other systems. Also the effect of height of frame on the response modification factor was investigated.

ACI Structural Journal, 2016

زلزله های نزدیک گسل به دلیل داشتن حرکت پالس گونه با پریود بلند در ابتدای رکورد،وجود نسبت بزرگ حدا... more زلزله های نزدیک گسل به دلیل داشتن حرکت پالس گونه با پریود بلند در ابتدای رکورد،وجود نسبت بزرگ حداکثر سرعت به حداکثر شتاب و حداکثر سرعت و شتاب بیشتر نسبت به زلزله ها ی دور از گسل دارای تفاوت عمده ای با زلزله های دور از گسل می باشند. در این تحقیق رفتار خطی و غیر خطی قابهای فولادی با سیستم دوگانه در سازه هایی با پلان متعارف و ارتفاع ٤،۸ و١٥ طبقه بصورت سه بعدی تحت تاثیر رکوردهای دور و نزدیک گسل، مورد بررسی و مقایسه قرار گرفته اند.نتایج بدست آمده تحلیل غیر خطی تاریخچه زمانی نشان دهنده تفاوت اساسی پاسخ سازه ها تحت رکوردهای نزدیک گسل در مقایسه با رکوردهای دور از گسل می باشند.بطور کلی با نزدیک شدن به گسل مشاهده می گردد که پاسخ سازه ها ازجمله نیازهای تغییر مکانی و برش پایه افزایش یافته و بحرانی تر می گردند. بنابراین نیاز به ویرایش آیین نامه و افزایش سطح نیروها در طراحی اینگونه سازه ها بیش از پیش احساس می شود.

An experimental-analytical investigation was conducted to study the behavior of high-strength RC ... more An experimental-analytical investigation was conducted to study the behavior of high-strength RC deep beams; a total of sixteen reinforced concrete deep beams with compressive strength in range of 59 MPaOf ' c O65 MPa were tested under two-point top loading. The shear span-to-effective depth ratio a/d was 1.10; all the specimens were simply supported and reinforced by vertical, horizontal and orthogonal steel bars in various arrangements. The test specimens were composed of five series based on their arrangement of shear reinforcing. The general behavior of tested beams was investigated. Observations were made on mid-span and loading point deflections, cracks form, failure modes and shear strengths. The test results indicated that both vertical and horizontal web reinforcement are efficient in shear capacity of deep beams, also the orthogonal shear reinforcement was the most efficient when placed perpendicular to major axis of diagonal crack. Concentrating of shear reinforcement within middle region of shear span can improve the ultimate shear strength of deep beam. The test results were then compared with the predicted ultimate strengths using the ACI 318-08 provisions; ACI code tended to either unsafe or scattered results. The performed investigations deduced that the ACI code provisions need to be revised.

Asian Journal of Civil Engineering (BHRC), 2017