Evaluation Possibility of Concrete Frames Rehabilitation with Off-Grade Steel Bracing

Document Type : Original Research

Authors
A. Biglari 1
S. nodeh 2
1 Assistant Professor, Department of Civil Engineering, Golestan University.
2 Master of Civil Engineering Student, Department of Civil Engineering, Golestan University.
A-10-64884-2
Abstract
Steel bracing is known as one of the most effective systems resistant to lateral loads, and its use has been the subject of numerous studies to improve the lateral deformation tolerance of existing reinforced concrete frames. In this study, the seismic performance of steel bracing in the concentric plane in order to strengthen the existing reinforced concrete structures has been numerically investigated. A scaled reinforced concrete frame was modeled by finite element method by simple cross bracing. In the retrofitting of damaged reinforced concrete structures, attention should be paid to the continuity of service of the structure in structures of high importance. The important point in buildings of special importance such as hospitals and government buildings is that in such buildings the maintenance of the structure must be maintained at all hours. In addition, the implementation of in-plane bracing causes the destruction of intermediate frame components and can reduce the effective role of intermediate frame components in the seismic load of reinforced concrete frames. The interaction between the frame and the frame in seismic loading is an important issue that has been extensively focused on by various researches. Another important point is to pay attention to architectural issues and match the retrofit method with the aesthetic aspects of the structure. If there is an opening in the damaged frame, using the internal reinforcement method may cause problems in the opening space in the desired frame.

According to the mentioned points, in order to continue the service of the structure during the retrofit operation and to reduce the destruction operation in the intermediate frame components, the reinforcement member can be externally connected to the damaged frame. Therefore, in this study, in order to achieve the mentioned goals, the implementation of steel bracing outside the plane was also investigated using the numerical method and its Possibility was verified. The studied sample was subjected to lateral load by displacement control method by ABAQUS software and analyzed by quasi-static method. This enables a better understanding of the performance of frames strengthened with in-plane and out-of-plane steel braces and the evaluation of the proposed method. In this study, the models were examined in terms of deformation and cracking characteristics, hysteresis, lateral stiffness reduction and energy absorption capability.The results of this study showed that after strengthening with braces, there was no local rupture due to the application of lateral load in the place of the plastic joints of the frames. As a result of the application of lateral load, the normal moment frame specimen showed a more fragile hysteretic behavior. The maximum resistance value of the reinforced concrete frame in a certain displacement after strengthening increased to 2.5 times of its original sample and resulted in less stress concentration in the boundary elements compared to in-plane bracing. The amount of hardness created in the sample increased to 1.35 times of the original sample and the amount of energy absorption increased to 2.25 times of the original sample. The results obtained in hysteresis, stiffness reduction and energy absorption sections indicate the effective performance of the proposed method in strengthening damaged reinforced concrete structures.

Keywords

Subjects

[1 ] Bush TD, Jones EA, Jirsa JO. Behavior of RC frame strengthened using
structural-steel bracing. J Struct Eng-ASCE 1991;117(4):1115–26.
[2 ] Badoux M, Jirsa JO. Steel bracing of RC frames for seismic retrofitting .J Struct Eng-ASCE 1990;116(1):55–74.
[3 ] Masri AC, Goel SC. Seismic design and testing of an RC slab–column frame strengthened by steel bracing. Earthq Spectra 1996;12(4):645–66.
[4 ] Rodriguez M, Park R. Repair and strengthening of reinforced concrete buildings for seismic resistance. Earthq Spectra 1991;7(3):439–59.
[5 ] Ohishi H, Takahashi M, Yamazaki Y. A seismic strengthening design and
practice of an existing reinforced concrete school building in Shizuoka city. In: Proceedings of the ninth world conference on earthquake engineering. vol. VII. 1988. p. 415–20.
[6 ] Pincheira JA, Jirsa JO. Seismic response of RC frames retrofitted with steel braces or walls. Journal of Structural Engineering. 1995 Aug;121(8):1225-35.
[7 ] Nateghi-Alahi F. Seismic strengthening of eight-storey RC apartment building using steel braces. Eng Struct 1995;17(6):455–61.
[8 ] Abou-Elfath H, Ghobarah A. Behaviour of reinforced concrete frames rehabilitated with concentric steel bracing. Canadian Journal of Civil Engineering 2000, 27(3), 433-444.
[9 ] Godínez-Domínguez EA, Tena-Colunga A, Pérez-Rocha LE. Case studies on the seismic behavior of reinforced concrete chevron braced framed buildings. Engineering Structures. 2012 Dec 1;45:78-103.
[10] Varum H, Teixeira-Dias F, Marques P, Pinto AV, Bhatti AQ. Performance evaluation of retrofitting strategies for non-seismically designed RC buildings using steel braces. Bulletin of earthquake engineering. 2013 Aug;11(4):1129-56.
[11 ] Ramin K, Fereidoonfar M. Finite element modeling and nonlinear analysis for seismic assessment of off-diagonal steel braced RC frame. International Journal of Concrete Structures and Materials. 2015 Mar;9(1):89-118.
[12 ] Dong YR, Xu ZD, Li QQ, Xu YS, Chen ZH. Seismic behavior and damage evolution for retrofitted RC frames using haunch viscoelastic damping braces. Engineering Structures. 2019 Nov 15;199:109583.
[13 ] Ahmad N, Mostafa M. Eccentric steel brace retrofit for seismic upgrading of deficient reinforced concrete frames. Bulletin of Earthquake Engineering 2020, 18(6), 2807-2841..
[14 ] Safaei S, Naderpour H, Gerami M. Reliability assessment of RC frames rehabilitated by eccentrically braces having vertical shear link. SN Applied Sciences. 2020 Mar;2(3):1-4.
[15 ] Hu B, Lv HL, Kundu T. Experimental study on seismic behavior of reinforced concrete frame in primary and middle schools with different strengthening methods. Construction and Building Materials. 2019 Aug 30;217:473-86.
[16 ] Tasnimi A, Masoomi A. Evaluation of response of reinforced concrete frames strengthened with steel bracing. In: Proceedings of the third international conference on seismology and earthquake engineering. 1990 [in Farsi].
[17 ] Canales MD, Broseno de la Vega R. Retrofitting techniques used in telephone buildings in Mexico. In: Proceeding of the tenth world conference on earthquake engineering. 1992. p. 5143–47.
[18 ] Maheri MR, Kousari R, Razazan M. Pushover tests on steel X-braced and knee-braced RC frames. Eng Struct 2003;25(13):1697–705.
[19 ] Maheri MR, Hadjipour A. Experimental investigation and design of steel brace connection to RC frame. Eng Struct 2003;25(13):1707–14.
[20] Youssef MA, Ghaffarzadeh H, Nehdi M. Seismic performance of RC frames with concentric internal steel bracing. Engineering Structures 2007, 29(7), 1561-1568.
[21 ] IBC. International building code. Falls Church (VA): International Code
Council; 2003.
[22 ] ACI Committee 318. Building code requirements for reinforced concrete (ACI 318-02). Detroit (MI): American Concrete Institute; 2002.
[23 ] AISC. Manual of steel construction: Load and resistance factor design. 3rd ed. Chicago (IL): American Institute of Steel Construction; 2001.
[24 ] AISC. Seismic provisions for structural steel buildings. Chicago (IL): American Institute of Steel Construction; 2002.
[25 ] Richard RM. Analysis of large bracing connection designs for heavy
construction. In: Proc. national steel construction conference. Chicago (IL): AISC; 1986. p. 31.1–31.24.
[26 ] Kmiecik P, Kaminski M. Modelling of Reinforced Concrete Structures and Composite Structures with Concrete Strength Degradation Taken into Consideration. Archives of Civil and Mechanical Engineering 2011, XI, No. 3
[27 ] Carreira DJ, Chu KH. Stress-strain relationship for plain concrete in compression. InJournal Proceedings 1985 Nov 1 (Vol. 82, No. 6, pp. 797-804).
[28 ] Feng DC, Wu G, Lu Y. Finite element modelling approach for precast reinforced concrete beam-to-column connections under cyclic loading. Engineering structures. 2018 Nov 1;174:49-66.
Modares Civil Engineering journal
Volume 24, Issue 2
May and June 2024
Pages 31-44