Computer Analysis of In-plane Behavior of Masonry Walls Strengthened by FRP Strips

Transcription

1 , October, 2014, San Francico, USA Computer Analyi of In-plane Behavior of Maonry Wall Strengthened by FRP Strip J. Szolomicki Abtract The paper concern the trengthening uing FRP compoite of maonry wall loaded in the plane. Strength of unreinforced maonry wall i baed on the trength of mortar and brick proportion and layout. When the force reache a ufficient value to exceed the in-plane trength of the wall, the detruction can occur due to hear. Thi failure i characterized by different factor: diagonal tenion, joint liding and flexural cracking. The paper preent an analytical model and numerical calculation for two different ytem of FRP trip. FRP trip were intalled parallel to the bed and head layer of mortar and along the diagonal of the wall in the X-haped form. In the recent year, interet in the renovation of the contruction and trengthening of exiting maonry building ha led to the development of non-invaive method of engineering. A an alternative to the ue of traditional method advanced FRP compoite fiber can be ued. FRP trip offer perfect phyical and mechanical propertie. The main characteritic of the compoite FRP are little effect on the overall tructure weight, high tenile trength (ultimate and long-term) in the fiber direction and negligible in the direction tranvere to them. Their function i primarily to take over the tenile tree caued by the action of hear and bending. Achievable advantage of their ue are alo increaing of the total tiffne, ductility, flexibility (very high value of limit train), high corroion reitance, eay way of application in area with limited acce, no need for application of heavy equipment when working with compoite material, and fat intallation. Furthermore, the ue of FRP compoite can be the perfect olution for modernization of tructural wall in eimic area, and give effectivene in repairing damaged maonry tructure during the earthquake. Index Term in-plane behavior, maonry wall, trengthening, FRP compoite I. INTRODUCTION In the recent year the importance of the repair and trengthening of maonry tructure ha greatly increaed. Thi i due not only to the detruction of maonry tructure a a reult of natural diater, but alo becaue many of the typical maonry tructure have achieved their ervice life, and a well it i a reult of a many activitie in the revitalization deign. Maonry tructure can be damaged due to the low trength of the contruction or overloading, dynamic vibration, ettlement and in-plane deformation. Behavior of maonry wall loaded in their plane depend on variou parameter, uch a mechanical and geometrical Manucript received February 21, 2014; revied April 01, J. Szolomicki i with the Intitute of Building Engineering, Wroclaw Univerity of Technology, Wroclaw, POLAND ( jerzy.zolomicki@ pwr.edu.pl). propertie, load chema and boundary condition. Strength of unreinforced maonry wall i baed on the trength of mortar and brick proportion and layout. When the force reache a ufficient value to exceed the in-plane trength of the wall, the detruction can occur due to hear. Thi type of failure i characterized by brittle tenile cracking in mortar and brick, and udden lo of lateral reitance. The traditional method ued in the repair of maonry are: - filling cavitie, internal void and ealing poible crack uing injection of mortar or fluid rein; - titching of large crack and other weak area by drilled hole in the element filled with bar and mortar; - ue of reinforced grouted perforation in order to improve the conitency and tenile trength of the wall; - external jacketing uing hotcrete or cat-in-itu concrete; - internal or external pot-tenioning with teel tie in order to tie tructural element together into an integrated threedimenional ytem. Conventional technique of trengthening can enure adequate increae of trength, tiffne and ductility, but are often hort-lating and have extenive influence. Moreover, additional component can be intalled to tranfer additional force or to trengthen exiting brace and trut. A an alternative to thee olution, in the event of a ignificant increae in the load of trengthened tructure compoite material may be ued [5]. The compoite material are made of polymeric fiber with high trength and are impregnated with polymeric rein. FRP compoite are characterized by perfect tenile trength in the fiber direction and the low trength in the direction tranvere to the fiber [12]. Their main function i to adorb the tenile tree ariing from hear and bending. Among the achievable advantage there are alo overall tiffne, trength and ductility. The fiber mot ued for compoite material employed in the application for the civil engineering tructure are: carbon CFRP and gla GFRP [1]. The mot common hape of the compoite material i the laminate one. The laminate are contituted by two or more overlapped thin layer [3], [14]. The fiber provide the trength and the rein matrix hold them in place and tranfer the load evenly amongt the fiber. The rein alo protect the fiber and bond them to the urface, tranferring the load from the tructure into the fiber. Method of trengthening uing CFRP and GFRP compoite material poitively affect the bearing capacity and the repone of the tructure [7]. FRP compoite are important in the tranferring of load, compenating the lack of tenile trength of maonry tructure [4]. However,

2 , October, 2014, San Francico, USA reinforcement cannot prevent maonry from cracking. So crack may alo form at a reinforced boundary, but crack cannot open becaue the reinforcement cloe them. Thi paper preent a finite element modeling approach, developed with LUSAS code, for the behavior analyi of the unreinforced and FRP trengthened brick wall ubjected to in-plane hear loading [6]. The main aim of the preented analyi are: to compare numerically behavior up to the ultimate condition of wall trengthened by different type of fibre (CFRP and GFRP one [8, 13, 15]) and placing the reinforcement in different poition, and to formulate analytical model able to predict the ultimate trength in agreement with the oberved failure mechanim. The application of FRP trip modifie the tatic behavior of wall becaue the fibre can bear the tree occurring at the tened edge. II. MODEL OF FRP AND MASONRY Deign of FRP trip reinforcement hould enure that the ytem i alway in tenion. Compreion of FRP compoite may caue debonding due to local intability. FRP compoite are generally ued in maonry wall in different geometrical arrangement. In preented numerical analyi two different pattern of wall trengthening were ued: - wall trengthened with cro pattern Carbon and Gla FRP trip; - wall trengthened with grid pattern Carbon and Gla FRP trip. In recent decade, many author have propoed different trategie for determining the numerical modeling of the tructural repone of maonry tructure [10]. For example taken into account the heterogeneity of the wall coniting of block connected by a head and bed mortar. There can be indicated the three concept of numerical modeling of the wall. The firt one i called the micro-modeling or twomaterial model, the econd implify micro-modeling, and the third i referred to a macro-modeling or equivalent material model, Fig. 1. Thi lat approach, alo known a homogenization, require the adoption of a unified repreentative replacement cell, which i a implification of the real ytem component forming the wall. It parameter mut correpond to the mot of the actual parameter of the material, which i the bai of the effectivene of the application of the FEM. In computer analyi of the wall wa ued the homogenized aniotropic numerical model propoed by Lopez [9]. Thi model i baed on aumption about the compatibility of deformation and equilibrium model of repreentative homogenized maonry cell, Fig. 2. Fig. 1. Micro and macro-model of maonry tructure. The in-plane reitance in load-bearing unreinforced maonry wall i provided by the hear bond trength of the mortar and the friction hear due to the horizontal load. The hear trength of a bearing wall, in the cae of a liding failure mode, can be determined a: (1) where: - hear tre at the hear bond failure, - hear bond trength at zero normal tre due to adheive trength of a mortar, - coefficient of friction between brick and mortar, - normal tre. FRP compoite can provide viable olution for trengthening of wall ubjected to tree caued by wind or earthquake load. Fig. 2. Bae cell of repreentative homogenized maonry. III. MODEL OF FINITE ELEMENT METHOD In the preented paper the tudied model were analyzed uing FE analyi uing the LUSAS code, ver Maonry wall wa modeled by mean of the olid element HX 16 and HX 20, Fig. 3. A the contitutive model for maonry material a homogenized model wa applied a propoed by Lopez et al [9]. In thi analyi a perfect bond between material wa aumed. The high trength of the epoxy rein ued to attach FRP trip to maonry wall upported the perfect bond aumption. In the finite element model, node of the FRP layered olid element were connected to thoe of adjacent maonry olid element in order to atify the perfect bond aumption.

3 , October, 2014, San Francico, USA a) Fig. 3. Example of applied olid element [11]. IV. NUMERICAL ANALYSIS OF MASONRY WALLS STRENGTHENED WITH FRP STRIPS Carbon fiber reinforced polymer (CFRP) and gla fiber reinforced polymer (GFRP) were conidered for invetigating the behavior of FRP trip bonded on maonry wall. b) Fig. 5. Different type of application of FRP trip for wall trenghtening: a) wall trengthened with cro pattern, b) wall trengthened with grid pattern. Fig. 4. Geometry, loading and boundary condition of analyzed maonry wall. The wall with dimenion (2.40 m x 1.2 m x 0.25 m) and with loading condition hown in Fig. 4 were the ubject of the analyi. Numerical analyi wa completed taking into account literature data [2] which indicated the location and the layout of the trengthening trip a in Fig. 5. In order to compare the validity of the propoed computer modeling technology and behavior of not trengthened and trengthened wall up to the ultimate tate the following cae were invetigated: - wall without trengthening; - wall trengthened with cro pattern by uing CFRP (epoxy TB650+HS Carbon UD) (Tab. 1); - wall trengthened with cro pattern by uing GFRP (epoxy TB650+E-Gla) (Tab. 1); - wall trengthened with grid pattern by uing CFRP (epoxy TB650+HS Carbon UD) (Tab. 1); - wall trengthened with grid pattern by uing GFRP (epoxy TB650+ E-Gla) (Tab. 1). Numerically examined wall were trengthened before failure mode wa reached. TABLE I BASIC CHARACTERISTICS OF CFRP AND GFRP STRIPS [11] Strip Widt h (cm) Thickne (mm) Modulu E x Modulu E y Modulu G xy (N/m 2 ) (N/m 2 ) (N/m 2 ) CFRP E9 9.0E9 4.4E9 GFRP E9 8.0E9 4.0E9 Each model wa tudied conidering typical horizontal uniformly ditributed load cae (Fig. 4). Selected reult of tre ditribution calculation were preented in the figure below: - tre S1 in not trengthened maonry wall for horizontal uniformly ditributed load 200 kn/m 2 (Fig. 6); - tre S1 in wall trengthened with cro pattern by uing CFRP trip for horizontal uniformly ditributed load 200 kn/m 2 (Fig. 7); - tre S1 in wall trengthened with grid pattern by uing CFRP trip for horizontal uniformly ditributed load 200 kn/m 2 (Fig. 8); - tre S1 in cro pattern of CFRP trip for horizontal uniformly ditributed load 200 kn/m 2, 500 kn/m 2 (Fig. 9, 10); - tre S1 in grid pattern of CFRP trip for horizontal uniformly ditributed load 200 kn/m 2, 500 kn/m 2 (Fig. 11, 12).

4 , October, 2014, San Francico, USA Fig. 6. Stre S1 in not trengthened maonry wall for horizontal uniformly ditributed load 200 kn/m 2. Fig. 8. Stre S1 in maonry wall trengthened with grid pattern by uing CFRP trip for horizontal uniformly ditributed load 200 kn/m 2. Fig. 7. Stre S1 in maonry wall trengthened with cro pattern by uing CFRP trip for horizontal uniformly ditributed load 200 kn/m 2. Fig. 9. Stre S1 in cro pattern of CFRP trip for horizontal uniformly ditributed load 200 kn/m 2. From Fig 6 to 12 it i poible to ee that CFRP and GFRP trip tranferred exceeded tenile tree and ignificantly reduced it in the wall.

5 , October, 2014, San Francico, USA Fig. 10. Stre S1 in cro pattern of CFRP trip for horizontal uniformly ditributed load 500 kn/m 2. Fig. 12. Stre S1 in grid pattern of CFRP trip for horizontal uniformly ditributed load 500 kn/m 2. Fig. 11. Stre S1 in grid pattern of CFRP trip for horizontal uniformly ditributed load 200 kn/m2. V. CONCLUSIONS The objective of the preented tudy wa to determine the behavior of unreinforced and FRP trengthened maonry wall under in-plane loading. For thi purpoe, the numerical approach wa carried out. In-plane load of the examined wall wa aumed in order to oberve the behavior of the wall from the initial tate (not damaged one) to the tate of it detruction. For uch model tre ditribution analye in the wall without reinforcement and in the wall trengthened with CFRP and GFRP trip (grid and cro pattern) were conducted. For the wall trengthened with CFRP and GFRP trip it can be clearly een that the tenile tree are tranferred to thee tripe that lead to a ignificant reduction of thee tre in the maonry wall. A the load increae, the zone of maximum tenile tre occur in the lower corner of the wall and move up. Tenile tre in the wall without reinforcement caue appearance of crack and with their further increae caue detruction. In the cae of wall trengthened with CFRP and GFRP fibre tre S1 ditribution i imilar. When the load increae intalled FRP trip tranfer greater tenile tree. However, it hould be noted, that more efficient for the tranfer of unfavorable tenile tre in the cae of cro pattern are the CFRP trip then GRFP one. The preented analyi how that both CFRP and GFRP compoite offer great advantage in trengthening of maonry wall giving important increae in their hear trength. Future reearch will involve the verification of the numerical model of trengthening the damaged maonry wall. It i alo planned to carry out laboratory tet on model and conduct tudie on exiting building.

6 , October, 2014, San Francico, USA REFERENCES [1] M. A. Aiello, S. M. Sciolti, Bond analyi of maonry tructure trengthened with CFRP heet, Contruction and Building Material, 20 (1-2),2006, pp [2] R. Capozucca, Experimental analyi of hitoric maonry wall reinforced by CFRP under in-plane cyclic loading, Compoite Structure 94(2011) pp [3] F. Ceroni, M. Pecce, G. Manfredi, A. Marcari, Experimental bond behavior in maonry element externally reinforced with FRP laminate, Proceeding of International Conference: Compoite in Contruction CCC 2003, Coenza, Italy, Ed. D. Bruno, G. Spadea, N. Swamy, Editoriale Bio, 2003, pp [4] S. W. Chuang, Y. Zhuge, T. Y. Wong, L. Peter, Seimic retrofitting of unreinforced maonry wall by FRP trip, Proceeding of Pacific Conference on Earthquake Engineering, [5] P. Foter, J. Gergely, D. Young, M. McGinley, Strengthening maonry building with FRP compoite, Proceeding of the 11th International Conference: Structural Fault & Repair, Edinburgh, UK, 183 (2006) [CD-ROM verion]. [6] E. Garbin, M. R. Valluzzi, C. Modena, N. Galati, A. Nanni, In-plane deign for maonry wall trengthened by FRP material, Proceeding of the 11th International Conference: Structural Fault & Repair, Edinburgh, UK, 184 (2006) [CD-ROM verion]. [7] R. M. Ki, L. P. Kollar, J. Jai, H. Krawinkler, Maonry trengthened with FRP ubjected to combined bending and compreion, Part II: Tet reult and model prediction, Journal of Compoite Material, 36(9),2002, pp [8] Y. Liu, J. Dawe, J. McInerney, Behaviour of GFRP heet bonded to maonry wall, Proceeding of the International Sympoium on Bond Behaviour of FRP in Structure (BBFS), Hong Kong, China, 2005, pp [9] J. Lopez, S. Oller, E. Onate, J. Lubliner, A homogeneou contitutive model for maonry, International Journal for Numerical Method in Engineering, 46, [10] P.B. Lourenco, Experimental and numerical iue in the modeling of the mechanical behavior of maonry. II Structural Analyi of Hitorical Contruction (IISAHC) Barcelona, [11] Lua Verion 14.7, Element Reference Manual, Lua, 2011, UK. [12] A. Morbin, Strengthening of Maonry Element with FRP Compoite. Univerity of Miouri-Rolla, pp [13] A. Nanni, G. Tumialan, Fiber-reinforced compoite for the trengthening of maonry tructure, Structural Engineering International, 13(4), 2003, pp [14] M. Panizza, E. Garbin, M. R. Valluzzi, C. Modena, Bond behaviour of CFRP and GFRP laminate on brick maonry, Proceeding of the 6th International Conference on Structural Analyi of Hitorical Contruction, Bath, UK, 2008, pp [15] M. R. Valluzzi, Strengthening of maonry tructure with Fibre Reinforced Platic: From modern conception to hitorical building preervation, Proceeding of the 6th International Conference on Structural Analyi of Hitorical Contruction, Bath, UK, 2008, pp