Performance based evaluation of RC coupled shear wall system with steel coupling beam

Habib Akbarzadeh Bengar,Roja Mohammadalipour Aski 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.2

Steel coupling beam in reinforced concrete (RC) coupled shear wall system is a proper substitute for deep concrete coupling beam. Previous studies have shown that RC coupled walls with steel or concrete coupling beam designed with strength-based design approach, may not guarantee a ductile behavior of a coupled shear wall system. Therefore, seismic performance evaluation of RC coupled shear wall with steel or concrete coupling beam designed based on a strength-based design approach is essential. In this paper first, buildings with 7, 14 and 21 stories containing RC coupled shear wall system with concrete and steel coupling beams were designed with strength-based design approach, then performance level of these buildings were evaluated under two spectrum; Design Basis Earthquake (DBE) and Maximum Considered Earthquake (MCE). The performance level of LS and CP of all buildings were satisfied under DBE and MCE respectively. In spite of the steel coupling beam, concrete coupling beam in RC coupled shear wall acts like a fuse under strong ground motion.

Effective flexural rigidities for RC beams and columns with steel fiber

Habib Akbarzadeh Bengar,Mohammad Asadi Kiadehi,Javad Shayanfar,Maryam Nazari 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.3

Influences of different variables that affect the effective flexural rigidity of reinforced concrete (RC) members are not considered in the most seismic codes. Furthermore, in the last decades, the application of steel fibers in concrete matrix designs has been increased, requiring development of an accurate analytical procedure to calculate the effective flexural rigidity of steel fiber reinforced concrete (SFRC) members. In this paper, first, a nonlinear analytical procedure is proposed to calculate the SFRC members’ effective flexural rigidity. The proposed model’s accuracy is confirmed by comparing the results obtained from nonlinear analysis with those recorded from the experimental testing. Then a parametric study is conducted to investigate the effects of different parameters such as varying axial load and steel fiber are then investigated through moment-curvature analysis of various SFRC (normal-strength concrete) sections. The obtained results show that increasing the steel fiber volume percentage increases the effective flexural rigidity. Also it’s been indicated that the varying axial load affects the effective flexural rigidity. Lastly, proper equations are developed to estimate the effective flexural rigidity of SFRC members.

A practical model for simulating nonlinear behaviour of FRP strengthened RC beam-column joints

Javad Shayanfar,Habib Akbarzadeh Bengar 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.1

Generally, beam-column joints are taken into account as rigid in assessment of seismic performance of reinforced concrete (RC) structures. Experimental and numerical studies have proved that ignoring nonlinearities in the joint core might crucially affect seismic performance of RC structures. On the other hand, to improve seismic behaviour of such structures, several strengthening techniques of beam–column joints have been studied and adopted in practical applications. Among these strengthening techniques, the application of FRP materials has extensively increased, especially in case of exterior RC beam-column joints. In current paper, to simulate the inelastic response in the core of RC beam–column joints strengthened by FRP sheets, a practical joint model has been proposed so that the effect of FRP sheets on characteristics of an RC joint were considered in principal tensile stress-joint rotation relations. To determine these relations, a combination of experimental results and a mechanically-based model has been developed. To verify the proposed model, it was applied to experimental specimens available in the literature. Results revealed that the model could predict inelastic response of as-built and FRP strengthened joints with reasonable precision. The simple analytic procedure and the use of experimentally computed parameters would make the model sufficiently suitable for practical applications.

Flexural ductility of HSC members

Maghsoudi, A.A.,Bengar, H. Akbarzadeh Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.24 No.2

In seismic areas, ductility is an important factor in design of high strength concrete (HSC) members under flexure. A number of twelve HSC beams with different percentage of ${\rho}$ & ${\rho}^{\prime}$ were cast and incrementally loaded under bending. The effect of ${\rho}^{\prime}$ on ductility of members were investigated both qualitatively and quantitatively. During the test, the strain on the concrete middle faces, on the tension and compression bars, and also the deflection at different points of the span length were measured up to failure. Based on the obtained results, the serviceability and ultimate behavior, and especially the ductility of the HSC members are more deeply reviewed. Also a comparison between theoretical and experimental results are reported here.

Numerical model to simulate shear behaviour of RC joints and columns

J.Shayanfar,H. Akbarzadeh Bengar 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.18 No.4

In this paper, a new numerical model for the evaluation of the seismic behaviour of existing reinforced concrete (RC) structure with considering the effect of variation of applied axial load on columns is presented. Focus is given on developing accurate and practical models for simulating nonlinearities in joint core as well as column under varying axial load. For exterior as well as interior joints, according to experimental and finite element results, principal tensile stresses versus shear deformation relations in joint core are recommended. Moreover, to consider the effects of stirrup on the principal tensile stress-shear deformation relation, an incremental procedure is proposed based on the Mohr theory. According to the proposed numerical model, complex nonlinear behaviour of joint core is simulated by two diagonal axial springs so that the effect of variation of axial load is also considered. The properties of these springs are determined based on the proposed principal tensile stress-shear deformation relation in the joint core. Moreover, the shear and flexural nonlinear behaviour of RC beams and columns is also simulated by rotational springs. A simplified methodology is developed to consider the effects of axial load variation on shear and flexural nonlinear behaviour of RC columns. To demonstrate the capability of the proposed numerical model at structural level, two RC frames with various failure modes are investigated. The results confirm the ability of the model in predicting the nonlinear behaviour of the frame, which can provide an alternative method for engineers in practice.

A new damage detection indicator for beams based on mode shape data

O. Yazdanpanah,S.M. Seyedpoor,H. Akbarzadeh Bengar 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.4

In this paper, a new damage indicator based on mode shape data is introduced to identify damage in beam structures. In order to construct the indicator proposed, the mode shape, mode shape slope and mode shape curvature of a beam before and after damage are utilized. Mode shape data of the beam are first obtained here using a finite element modeling and then the slope and curvature of mode shape are evaluated via the central finite difference method. In order to assess the robustness of the proposed indicator, two test examples including a simply supported beam and a two-span beam are considered. Numerical results demonstrate that using the proposed indicator, the location of single and multiple damage cases having different characteristics can be accurately determined. Moreover, the indicator shows a better performance when compared with a well-known indicator found in the literature.

Flexural strengthening of continuous unbonded post-tensioned concrete beams with end-anchored CFRP laminates

Ghasemi, Saeed,Maghsoudi, Ali A.,Bengar, Habib A.,Ronagh, Hamid R. Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.6

This paper provides the results of an experimental investigation into the flexural behavior of continuous two-span unbonded post-tensioned high strength concrete (HSC) beams, strengthened by end-anchored CFRP laminates of different configurations in the hogging region. Implementing two different configurations of end-anchorage systems consisting of steel plates and bolts and carefully monitoring the development of strains throughout the load history using sufficiently large number of strain gauges, the response of beams including the observed crack propagations, beam deflection, modes of failure, capacity enhancement at service and ultimate and the amount of moment redistribution are measured, presented and discussed. The study is appropriate in the sense that it covers the more commonly occurring two span beams instead of the simply supported beams investigated by others. The experiments reconfirmed the finding of others that proper installation of composite strengthening system is most important in the quality of the bond which is essential for the internal transfer of forces. It was also found that for the tested two span continuous beams, the capacity enhancement is more pronounced at the serviceability level than the ultimate. This is an important finding as the design of these beams is mostly governed by the serviceability limit state signifying the appropriateness of the suggested strengthening method. The paper provides quantitative data on the amount of this capacity enhancement.

A new damage detection indicator for beams based on mode shape data

Yazdanpanah, O.,Seyedpoor, S.M.,Bengar, H. Akbarzadeh Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.4

In this paper, a new damage indicator based on mode shape data is introduced to identify damage in beam structures. In order to construct the indicator proposed, the mode shape, mode shape slope and mode shape curvature of a beam before and after damage are utilized. Mode shape data of the beam are first obtained here using a finite element modeling and then the slope and curvature of mode shape are evaluated via the central finite difference method. In order to assess the robustness of the proposed indicator, two test examples including a simply supported beam and a two-span beam are considered. Numerical results demonstrate that using the proposed indicator, the location of single and multiple damage cases having different characteristics can be accurately determined. Moreover, the indicator shows a better performance when compared with a well-known indicator found in the literature.

Flexural strengthening of continuous unbonded post-tensioned concrete beams with end-anchored CFRP laminates

Saeed Ghasemi,Ali A. Maghsoudi,Habib A. Bengar,Hamid R. Ronagh 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.6

This paper provides the results of an experimental investigation into the flexural behavior ofcontinuous two-span unbonded post-tensioned high strength concrete (HSC) beams, strengthened by endanchoredCFRP laminates of different configurations in the hogging region. Implementing two differentconfigurations of end-anchorage systems consisting of steel plates and bolts and carefully monitoring thedevelopment of strains throughout the load history using sufficiently large number of strain gauges, theresponse of beams including the observed crack propagations, beam deflection, modes of failure, capacityenhancement at service and ultimate and the amount of moment redistribution are measured, presented anddiscussed. The study is appropriate in the sense that it covers the more commonly occurring two span beamsinstead of the simply supported beams investigated by others. The experiments reconfirmed the finding ofothers that proper installation of composite strengthening system is most important in the quality of the bondwhich is essential for the internal transfer of forces. It was also found that for the tested two span continuousbeams, the capacity enhancement is more pronounced at the serviceability level than the ultimate. This is animportant finding as the design of these beams is mostly governed by the serviceability limit state signifyingthe appropriateness of the suggested strengthening method. The paper provides quantitative data on theamount of this capacity enhancement.