EFFECT OF CONFIGURATIONS OF PARTIAL CONCRETE JACKETING ON BEHAVIOR OF STRENGTHENED BEAM

Transcription

1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 10, October 2018, pp , Article ID: IJCIET_09_10_062 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed EFFECT OF CONFIGURATIONS OF PARTIAL CONCRETE JACKETING ON BEHAVIOR OF STRENGTHENED BEAM Bandar F. Al-Harbi Chairman of Civil and Architectural Construction Department, Institute of Architecture and Construction, Qassim Region, Technical and Vocational Training Corporation (TVTC), PG, Civil Engineering Department, College of Engineering, Qassim University, KSA Dr. Gamal A. Al-Saadi Assistant Professor, Civil Engineering Department, College of Engineering, Qassim University, KSA. Dr. Ahmed F. Elragi Assistant Professor, Civil Engineering Department, College of Engineering, Qassim University, KSA. ABSTRACT With the continuous developments of civil engineering practices in general and structural engineering in particular, engineers have been investigating the rehabilitation/strengthening techniques of existing structures to save them and/or increase their load capacity by raising the efficiency of the structural elements of existing buildings such as beams and columns. This technique used for different purposes such as in increasing the lifetime of these structures, adapting with the change of functionality of the building, and to overcome the error design. The objective of this study is to investigate the effect of the strengthening reinforced concrete (RC) beams using partial concrete jacketing with different configurations. Using partial concrete jacketing consider as a demand for the RC beams that have architectural limitations in terms of the size such as beams in the building edges. This study will focus on increasing the load capacity of beams in existing buildings. The effect of using the partial concrete jacketing technique on the load capacity of beams will be investigated aiming at identifying the best practices in this regard using Finite Element Method (FEM)-based numerical analysis utilizing ANSYS software. Moreover, Reinforcement stress is discussed. The results of the numerical analysis have verified experimentally utilizing previous research. It is noticed that this proposed concrete jacketing proves to be a more effective technique to strengthen the existing beams which shall help engineers in practical use in the field editor@iaeme.com

2 Effect of Configurations of Partial Concrete Jacketing on Behavior of Strengthened Beam Key words: ANSYS, Numerical analysis, Partial concrete jacketing, Reinforced concrete beams, Strengthening. Cite this Article: Bandar F. Al-Harbi, Dr. Gamal A. Al-Saadi, Dr. Ahmed F. Elragi, Effect of Configurations of Partial Concrete Jacketing on Behavior of Strengthened Beam, International Journal of Civil Engineering and Technology (IJCIET) 9(10), 2018, pp INTRODUCTION Firstly, the rehabilitation and strengthening of existing structures have common use in construction field to increase load capacity of structures by raising efficiency of structural elements of buildings such as beams and columns. This technique contributes in cost saving and increasing longevity of structures. Rehabilitation and strengthening is an effective alternative to rebuilding or reconstruction of existing structures. In addition, there are many researches that studied different ways of rehabilitating to increase the strength and load capacity of concrete beams considering them as basic structural elements [1]. Strengthening of existing structures considers among the most important challenges in civil engineering in recent years. Furthermore, improving resistance or stiffness to resist additional loads and increasing the load-carrying capacity for higher allowable loads are possible reasons for using strengthening techniques [2]. The strengthening of the structural elements of existing buildings is considered the most significant topic in the field of rehabilitation of structures [3]. Most of the studies focused on FRP technique because of its ability to increase strength without significantly increasing in dead load of structures (D.L); this urges a need to study other methods of confinement [4]. The research depends on the use of concrete jacketing for strengthening constructed RC beams and study their structural behavior. It has been chosen since engineers are familiar with it and it does not require skilled labor compared to the other methods [5]. Rehabilitation of existing structures using concrete jacketing is required in some situations such as [6]: Buildings that are not designed to resist seismic forces or designed with old seismic codes. The low quality of the constructions. Changing the use or functionality of structures. Weak members of soft story buildings. Weak members of monumental buildings. Strengthening technique may be required due to safety demands or changes in the usage of the structure. In addition, they indicate this technique is more economical for structures compared with demolishing and rebuilding [7]. Concrete jacketing of beams involves increasing cross-sectional area of reinforced concrete whether one or more face [8]. Generally, there are two purposes of using concrete jacketing; first, is to increase shear capacity, second, is to improve flexural strength for structural elements [6] editor@iaeme.com

3 Bandar F. Al-Harbi, Dr. Gamal A. Al-Saadi, Dr. Ahmed F. Elragi This study will focus on structural behavior of RC beams with partial concrete jacketing, especially the load capacity through determine the applied load for each strengthened beam by numerical analysis utilizing ANSYS software [9]. Importance of the concrete jacketing in this numerical study is to strengthen RC beams in term of load capacity through increasing value of applied loads. Regardless of the cause of the strength shortage whether it is a design error or change the function of the building or so on. It is significant to introduce details of the experimental tests that carried out by Chalioris et al. [10], since these were used for verification of the numerical ing in this study. This previous research discussed the behavior of RC beams that were strengthened using concrete jacketing. Self-compacting concrete (SCC) has been used in this experimental test because it does not require compaction by vibration [11]. The jackets consisted of thin layers of fine-aggregate concrete and not exceeding 25 mm in thickness. The research illustrated that performance efficiency with thin RC jackets is higher than conventional RC jackets. Chalioris et al. [10] conducted on RC beams that were constructed and subjected to monotonic loading. The beams were strengthened using U-shaped SCC jacket. The concrete jackets included small diameter steel bars and U-formed stirrups. Moreover, experimental results confirmed that the load capacity and overall performance of RC beams with SCC jacketing was greatly improved compared with the initial situation by 50%. In addition, analytical results are in a good agreement with the experimental ones. The present study focused on the effect of the position of RC jacket or, in other words, configurations of RC jackets that may become a choice for engineers in practical uses due to determined architectural conditions or situations that not permit to build U-jacket to which considered conventional method for concrete jacketing to strengthen RC beams. 2. NUMERICAL MODEL The numerical ing achieved using ANSYS [9] and the details in the present study are taken the same as the previous research Chalioris et al. [10] which includes experimental test (U-jacket) (Figure 1), especially of the beam B2J-U which chosen as a control beam and to verify the finite element s through it. Results of the nonlinear finite element s in the present study have checked by comparing with the corresponding results of that experimental test that available in the reference [10] Geometry and Definition of Numerical Models Figure 1 and Table 1 represent the cross-section and assumed reinforcement details for the numerical s of the RC beams B2 & B2J. Figure 1 Cross-sectional and reinforcement details of the beam s B2 & B2J (all dimension in mm) editor@iaeme.com

4 Effect of Configurations of Partial Concrete Jacketing on Behavior of Strengthened Beam Initial beam name Table 1 Geometrical, mechanical and steel reinforcement characteristics of the beam s b o /h o (mm) d o (mm) Characteristics of the initial beams ɑ/d o B2 125/ Jacketed beam name Top 4ϕ8 (0.92%) Longitudinal bars Bottom 2ϕ8 (0.46%) Stirrups ϕ 5/300 (0.10%) ƒ c,o /ƒ ct,o (MPa) 28.2/2.15 Characteristics of the jackets and the jacketed beams Total Longitudinal bars U- ƒ c,j /ƒ ct,j b J /h J d J reinforcement ɑ/d (MPa) (mm) (mm) J formed Top Middle Bottom Stirrups ρ l (%) ρ t (%) B2J-U 175/ ϕ5 (0.11%) 2ϕ5 (0.11%) 4ϕ5 (0.22%) Φ5/150 (0.15%) 42.8/ In case of not permit to build U-jacket to which considered conventional method for concrete jacketing to strengthen RC beams, especially when the beams have some architectural limitations in terms of size. There are three s (Figure 2) discussed that have partial concrete jacketing as well as the original beam and the U-jacket : Bottom and left. Bottom. One side. Figure 2 Cross-sectional and reinforcement details of the s (all dimension in mm) 2.2. Materials All s details depend on the numerical B2J-U (U-jacket ) that indicated in Figure 2 with reing the position and shape of the concrete jacket according to the cases under study. Moreover, all configurations of concrete jackets have f y equals 255 MPa for ϕ5 and 570 MPa for ϕ8, and f'c equals 42.8 MPa for the concrete jackets while it equals 28.2 MPa for the original concrete beam Boundary Condition and Applied Load Characteristics of the boundary condition and applied load can be summarized in the following points and in (Figure 3): editor@iaeme.com

5 Bandar F. Al-Harbi, Dr. Gamal A. Al-Saadi, Dr. Ahmed F. Elragi The beam self-weight was taken into consideration in this numerical ing. The simple beam rested on two supports (hinged and roller) as well as it subjected to twopoint load. Length of the rectangular beam is 1600 mm and its cross section for B2J-U (U-jacket ) are 150 x 222 mm. Distance between the supports is 1400 mm, the distance between the two-point load is 200 mm and shear span equals 600mm. The beam self-weight was taken into consideration in this numerical ing. The simple beam rested on two supports (hinged and roller) as well as it subjected to twopoint load. Length of the rectangular beam is 1600 mm and its cross section for B2J-U (U-jacket ) are 150 x 222 mm. Distance between the supports is 1400 mm, the distance between the two-point load is 200 mm and shear span equals 600mm. Figure 3 Geometry, loading, and beam dimension - simply supported beam 2.4. Model Mesh, Type of Analysis, Types of Element Characteristics of the mesh and type of analysis can be summarized in the following points: The was constructed numerically by fine and coarse meshes as shown in (Figure 4). Figure 4 Finite element mesh, strengthened beam (U-jacket ) Three types of finite element (Figure 5) were used in the : a. Type no.1: LINK 180 element which represents rebar and reinforcement generally. b. Type no.2: SOLID 65 element which represents concrete. c. Type no.3: SOLID 45 element which represents supports and loads editor@iaeme.com

6 LIN K 180 SOLI D 65 Effect of Configurations of Partial Concrete Jacketing on Behavior of Strengthened Beam Figure 5 Geometry of elements: Link180, Solid65, and Solid45 [9] Nonlinear static analysis was performed in the ing. Displacement control has relied which depended on increasing the displacement and recording data of the applied load sequentially as a method in constructing load-deflection curve. Table 2 shows details of the mesh such as number of finite element and nodes. Table 2 Number of elements and nodes generated in mesh for reinforced Description No, of Element No. of Nodes Element Type Original beam concrete U- jacket concrete Original beam reinforcement U- jacket reinforcement VALIDATION OF NUMERICAL MODEL Depending on test results, load capacity of the beam before jacketing is 36.4 kn, it reaches 55.2 kn after jacketing. The numerical ing presents similar results of the experimental test indicated. As a result of validation process, the load capacity (P u ) for the U-jacketed beam (B2J-U) equals 55.2 kn in the experimental test, and it equals 51 kn by numerical analysis. As an additional process of validation, the load capacity (P u ) for the original beam (B2) equals 36.4 kn in the experimental test, and it equals 34 kn by numerical analysis. This result indicates to a good agreement between the experimental and numerical results. That means the numerical has verified as shown in (Table 3), (Figure 6) and (Figure 7). Table 3 Experimental test results Beam name P flex (kn) P diag (kn) P u (kn) P u (mm) B B2J-U There is increasing in the load capacity by dint of increasing cross section of RC beam (Ujackets). Figure 6 and Figure 7 refer to about 50% increase in the applied load of the jacketed beam (B2J-U) compared with the original beam (B2). In addition, they show a comparison between the results of the numerical analysis and the experimental tests. This matching confirms that the numerical ing is validated editor@iaeme.com

7 Applied load, N Applied load, N Bandar F. Al-Harbi, Dr. Gamal A. Al-Saadi, Dr. Ahmed F. Elragi Verification of B2J-U (U-Jacket ) B2J-U (Numerical) B2J-U (Experimental) Deflection, mm Figure 6 Verification of B2J-U Verification of B2 (Original beam ) B2 (Numerical) B2 (Experimental) Deflection, mm Figure 7 Verification of B2 4. RESULTS AND DISCUSSION All numerical s that mentioned in section 2.1 have constructed using ANSYS software which is finite element ing. Figure 8 also considers as a comparison between the concrete jackets of the s under study: U-jacket, bottom and left, bottom, and one side. This comparison depended on numerical analysis and represents the maximum stress and deflection of the RC jackets for the studied s. Figure 8 Nodal solution, maximum deflection (DMX, mm) and maximum stress (SMX, MPa) of jackets The load capacity of each case has compared with the u-jacket and the original beam as shown in (Table 4), (Figure 18), and (Figure 19), (Table 5). Table 4 The load capacity of the beam s Beam name Load Capacity (kn) Original beam One side Bottom Bottom & left U-Jacket editor@iaeme.com

8 Load capacity (kn) Applied Load, N Effect of Configurations of Partial Concrete Jacketing on Behavior of Strengthened Beam Comparison between different configurations of concrete jackets and original beam Original beam U-Jacket Bottom & left Bottom One side Displacement, mm Figure 9 Structural behavior of different configurations Original beam One side Bottom Bottom and left U-Jacket Figure 10 The load capacity of the beam s Table 5 The rate of the load capacity in the jacketed beam s compared with the original beam Jacketed beam name Increase percentage of load capacity % One side Bottom Bottom & left U-Jacket 6% 15% 32% 50% 4.1. First Case: Bottom and Left Model When the beams in the edges of buildings have some architectural limitations in terms of size due to one of faces, the bottom and left jacket could be a choice to strengthen beams rather than the conventional method (U-jacket). Figure show the numerical analysis for tension rebars and stirrups editor@iaeme.com

9 Bandar F. Al-Harbi, Dr. Gamal A. Al-Saadi, Dr. Ahmed F. Elragi Figure 11 Stress of stirrups of the original beam original beam Figure 12 Stress of main rebar of the (ϕ5 (256 MPa), f ymax =50.82 MPa) (ϕ8 (570 MPa), f ymax = MPa) Figure 13 Stress of main rebar of the jacket (ϕ5 (256 MPa), f ymax = MPa) 4.2. Second Case: Bottom Model When there are architectural limitations in term of size due to constraints on both sides of the beam, or when not accept any increase in the horizontal dimension, the bottom jacket could be a choice to strengthen beams. Figure show the numerical analysis for tension rebars and stirrups. Figure 14 Stress of stirrups of the original beam Figure 15 Stress of main rebar of the original beam (ϕ5 (256 MPa), f ymax =45.61 MPa) (ϕ8 (570 MPa), f ymax = MPa) editor@iaeme.com

10 Effect of Configurations of Partial Concrete Jacketing on Behavior of Strengthened Beam Figure 16 Stress of main rebar of the jacket (ϕ5 (256 MPa), f ymax = MPa) 4.3. Third Case: One Side Model When there are architectural limitations in term of size due to constraints on both bottom and one side of the beam, or when not accept any increase in the vertical dimension and one direction in the horizontal dimension, the one side jacket could be a choice to strengthen beams. Figure show the numerical analysis for tension rebars and stirrups. Figure 17 Stress of stirrups of the original beam Figure 18 Stress of main rebar of the original beam (ϕ5 (256 MPa), f ymax =48.02 MPa) (ϕ8 (570 MPa), f ymax = MPa) Figure 19 Stress of main rebar of the jacket (ϕ5 (256 MPa), f ymax = MPa) editor@iaeme.com

11 Bandar F. Al-Harbi, Dr. Gamal A. Al-Saadi, Dr. Ahmed F. Elragi 5. CONCLUSIONS This study concluded that the most effective s of those cases are the u-jacket where its increase percentage in the load capacity reaches 50% compared with the original concrete beam. Then the bottom and left where reaches 32% while the bottom and the one side reach 15% and 6% respectively. In addition, the most stiffness s are the u-jacket, bottom and left, bottom, one side, and original beam respectively. The results confirm the benefit of partial concrete jacketing in the cases studied compared with the original beam where all partial concrete jacketing s gave increase rate in the load capacity not less than 15% except the one side compared with the original concrete beam and it reaches to 50%. For all configuration, the stirrups stresses didn t reach yield stress for our case study. It noticed that all tension rebars reached yield for all configuration hence it will be flexure failure. REFERENCES [1] J. Rupp, Modeling of steel-jacketed reinforced concrete under axial compressive loads, Master's Thesis, The Ohio State University, Columbus, OH, [2] B. S. Al-Azzawi, Fatigue of Reinforced Concrete Beams Retrofitted with Ultra-High Performance Fibre-Reinforced Concrete, Phd thesis, Cardiff University, [3] C. Oucif, K. Ouzaa, V. Stoian, and C.A. Dăescu, Numerical ing of reinforced concrete strengthened columns under cyclic loading, Arabian Journal for Science and Engineering, 42(9), 2017, [4] J. Galbo, Fiber Reinforced Polymer (FRP) for the Repair & Retrofit of Existing Structures & for New Construction, Master s Thesis, Cooper Union, New York, [5] S. Bousias, A.L. Spathis, M.N. Fardis, and D. Biskinis, Concrete or FRP jacketing of concrete columns for seismic retrofitting, Advances in Earthquake Engineering for Urban Risk Reduction, pp.33-46, [6] N. Gupta, P. Dhiman, and A. Dhiman, Design and Detailing of RC Jacketting for Concrete Columns, IOSR Journal of Mechanical and Civil Engineering, 12(6), 2015, [7] K. Holschemacher, S. Iqbal, A. Ali and T. A. Bier, Strengthening of RC beams using lightweight self-compacting cementitious composite, Procedia Engineering, 172, 2017, [8] Q. Khalaf, Comparative Study for Strengthening Techniques of RC Beams Using Concrete Jackets and Steel Plates, Master's Thesis, Islamic University of Gaza, [9] ANSYS, Theory reference, release 19.0, ANSYS, Inc., USA, Academic Edition, [10] C. E. Chalioris, G. E. Thermou and S. J. Pantazopoulou, Behaviour of rehabilitated RC beams with self-compacting concrete jacketing Analytical and test results, Construction and Building Materials, 55, 2014, [11] R. Venu, B. Suraj and G. V. Ramana, Effects of nitric acid on durability characteristics of M60 self compacting concrete, International Journal of Civil Engineering and Technology (IJCIET), 9, 2018, editor@iaeme.com