Seismic Performance of Multistorey Masonry Structure with Openings Repaired with CFRP Grid

FRP composites have been used for strengthening RC and masonry structures for decades. However, the researches on repairing multistorey masonry structures using FRP grids were relative less. In the present paper, an experimental study on the seismic performance of multistorey masonry structure with openings repaired with CFRP grid is introduced. Specifically, a 1/3-scale three-floormasonry wall with window openings was tested under quasistatic action to simulate the seismic damages.-e damaged masonry wall was then repaired by externally bonding CFRP grids to the areas where the cracks intensively occurred.-e repaired masonry wall was retested under the same loading to investigate the seismic resistance and assess the recovery attributed from the CFRP grid repairing. -e findings of this study showed that CFRP grid repairing could effectively postpone or even prevent the occurrence and development of cracking. -e seismic resistance of the masonry, including shear capacity, energy dissipation capacity, deformability, stiffness degradation, and ductility, was restored. -e application of CFRP grid may shift the failure mechanism of the multistoreymasonry wall.-e recommendation of repair scheme for the similar structures was also proposed in accordance with the findings of the present work.


Introduction
ere have been large a number of masonry structures still on service although reinforced concrete (RC) and steel structures prevail in the modern structures.Masonry structures show the advantages in good acoustic and heat insulation, local availability of raw material, and low cost [1,2].Masonry is a heterogeneous material because of the diversity of components [3].e majority of unreinforced masonry (URM) structures are prone to severe damage under seismic action due to the low strength and consequently vulnerable to earthquake [4,5].URM walls or under-reinforced masonry walls subjected to seismic actions can fail by in-plane or out-of-plane mode.In-plane failures usually exhibit diagonal shear crack pattern, by sliding of a portion of the wall generally along a bed joint, by rocking about the wall toe or by crushing of the wall toe [6].In terms of the structural configuration, masonry structures, either solid or segmented by window and door openings in each storey, represent the basic structural element of a masonry building [1].
ere are two types of failure mechanism summarized by Tomaževič [1] for the masonry wall with openings, weak piers failure, and weak spandrels failure.e masonry structural walls, composed of piers and spandrels, are usually modelled as an equivalent frame structure [1,7].
e shear force and bending moment from earthquake are introduced in both piers and spandrels and controls the failure mechanism [1,8].
e application of fiber-reinforced polymer (FRP) for masonry structure retrofitting and repairing is an advanced technology due to its advantages of high strength, light weight, good durability, and convenient implementation [4,[9][10][11][12][13].In general, the existing studies have demonstrated that the seismic performance, including the seismic shear bearing capacity, the ductility, and the energy dissipation, of masonry structures can be significantly improved by bonding FRP composites [4,[14][15][16][17][18].However, most of the previous studies focused on the FRP strengthened undamaged URM walls.ere has been less study contributed to the repairing in which masonry walls were damaged before repairing with FRP.In these repairing studies, the masonry walls were usually subjected to in-plane loading, either quasistatic or shake table testing, to simulate the earthquake actions.ese walls were consequently damaged and later repaired with FRP.en, the repaired walls were tested to failure [13,19,20].e results from Zhou et al. [13] and Santa-Maria and Alcaino [19] suggested that the repair scheme needed to be determined according to the magnitude of damage and proved that the maximum resistance of the repaired walls depended on the repair scheme.
FRP grid is a composite material consisting of bidirectional bers, which is especially suitable for the structural members with large areas, such as shear walls and slabs [4,21,22].FRP grid has been used to retro t the RC structures [21,23].However, studies on masonry walls repaired with FRP grid have been lack in the literature.Meanwhile, the existing researches are limited to the masonry wallettes [22].e research on repairing more complex masonry structures, like multistorey masonry walls with openings, is rare.
In this paper, a 1/3-scale three-storey masonry wall with openings was designed.e strength and size of brick and mortar were not scaled accordingly in the present study because it is still a challenge to determine compatible scale factors among structures and materials.e model URM wall initially under the in-plane quasistatic loading was damaged.It was repaired with carbon ber-reinforced polymer (CFRP) grid, which was adhesively bonded at the areas where the cracks intensively occurred.e repaired masonry wall was retested under the identical loading.e purpose of this work was to investigate the seismic performance of the model wall prior to and after repairing.Comparisons are made in terms of shear strength, cracking pattern, failure mechanism, hysteretic responses, sti ness degradation, energy dissipation capacity, and interstorey drifts.Recommendation of repair scheme for the similar masonry structures was eventually proposed based on the ndings of the work.

Model Wall Design.
e experiment protocol included the quasistatic testing of the URM wall, repairing the damaged URM wall with CFRP grid, as well as the quasistatic test of the CFRP grids repaired masonry (CRM) wall.A 1/3-scale three-storey masonry wall with openings was constructed.RC beams were set at the top and the bottom of the model wall, to support and apply the uniform vertical load.
ree identical openings existed in each oor.RC lintels were set at the top of each opening at the rst and second oors, whereas the lintels of third oor overlapped with the top RC loading beam.Both ends of the wall were set with short cross walls, to provide the lateral restriction and accurately model the real multistorey masonry structures.
e dimensions of the model wall are illustrated in Figure 1. e repairing scheme was completed by adhesively bonding CFRP grids in the certain areas where the cracks intensively developed.e repairing detail was reported in the following section.

Material Properties.
e model wall was constructed with solid clay bricks (240 mm × 115 mm × 53 mm).e test brick compressive strength was 17.8 MPa with a standard deviation of 0.12 MPa according to the Chinese standard GB50003-2011 [24].Twelve cube mortar samples (70.7 mm × 70.7 mm × 70.7 mm) were cast, and the average compressive strength was 8.6 MPa with a standard deviation of 0.52 MPa.Based on the test strengths of brick and mortar, the compression strength and the shear strength of masonry were calculated as 5.3 MPa and 0.37 MPa based on the models proposed in GB50003-2011 [24].
e composite material used in the present study was a bidirectional equal-strength CFRP grid, shown in Figure 2, with uniform grid size of 20 mm × 20 mm and minimum thread width of 3 mm, for which, the material properties are listed in Table 1.e material properties of the CFRP sheet that were bonded at the edges of openings to prevent the premature cutting fracture of CFRP grid are listed in Table 1.e adopted epoxy adhesive was the Sika-330 epoxy resin, and its material properties are listed in Table 1 as well.

Test Setup.
e test setup is presented in Figure 3. e bottom RC beam was xed to the strong oor by four threaded rods.Two vertical hydraulic jacks were placed on the top of the distribution beams to apply the vertical load.
e top RC beam uniformly distributed the vertical load that was kept constant as 0.75 MPa during the test.e lateral load was applied to the height of every oor by three MTS  Advances in Civil Engineering electrohydraulic servo actuators.e top actuator was set as the master unit, and the rest two actuators were the slave units.In order to achieve a triangular load distribution, the master unit was under displacement control and the slave units were coded to be load-controlled in accordance with the load of master unit.It means that each actuator pushed the wall with the same proportional loads at each oor as shown in Figure 4.
A typical quasistatic loading history was adopted to simulate the seismic action by a displacement-controlled loading.For the URM wall, two cycles were adopted at each displacement level prior to the appearance of rst visible crack and one cycle thereafter, in which the displacement increment was 1 mm.When the seismic shear bearing capacity of the wall decreased to 85% of the maximum load, or the wall displayed severe damages, the test was terminated.For the CRM wall, the same loading history as the URM wall was applied.e loading history is presented in Figure 5.
ree linear variable di erential transformers (LVDTs) were installed to measure the lateral displacement at height of every oor.e loading scheme and instrumentation are illustrated in Figure 4.

Test of URM Wall.
e URM wall response under quasistatic action could be divided into three stages as follows: the elastic stage, the deformation development stage, and the strength decrease stage.
e URM wall showed elastic response of lateral load-displacement   relationship when the top lateral displacement was below ±7 mm, indicating that it behaved the in elastic stage.ere were no visible cracks observed at this stage.When the top lateral displacement reached to ±7 mm, the rst visible crack appeared in the mortar layer of the 2-CD region, which was de ned as the upper boundary of the elastic stage.Consequently, each displacement level was cycled once afterwards.e corresponding top displacement range of the deformation development stage was ±8 mm to ±15 mm.When the top lateral displacement reached to +8 mm, the 2-AB and 2-BC regions displayed cracks at the corner of rst oor openings; in the meantime, new cracks occurred in the 2-CD region.When the top lateral displacement reached to +10 mm, the cracks of 2-AB, 2-BC, and 2-CD regions further increased and developed.Following the completion of the loading cycle at the ±11 mm, the cross diagonal cracks appeared in the 2-AB, 2-BC, and 2-CD regions.After completing the loading cycle of ±12 mm, few small cracks appeared in the 1-B region.Following the completion of the loading cycle of ±13 mm, the 1-C and 2-B regions began to crack and existing cracks in the spandrels of second oor (2-AB, 2-BC, and 2-CD) widened further.When the top lateral displacement reached to ±14 mm, the 2-C region began to crack.As the top lateral displacement increased to ±15 mm, where the URM wall reached the maximum bearing capacity, the 1-B, 1-C, 2-B, and 2-C regions showed completely connected cross diagonal cracks.Simultaneously, the 3-AB, 3-BC, and 3-CD regions started to crack.During this stage, the load increase gradually slowed down, indicating that the sti ness of URM wall decreased.e cracks of the URM wall propagated and gradually widened.
e corresponding displacement range of the strength decrease stage was between ±16 mm and ±21 mm.During this stage, new cracks appeared in the damaged regions, the existing cracks became intensi ed, and bricks at the bottom corners of the rst oor openings crushed.When the top lateral displacement reached to ±21 mm, the loading capacity of the URM wall reduced to 85% of the peak load, and the test was terminated.
e nal failure mode and cracking schematic diagram of the URM wall are presented in Figure 6. e cracks in the spandrels of the second oor rstly occurred, the piers of the rst oor cracked thereafter, and the piers of the second oor then cracked, the spandrels of the third oor nally cracked.
e failure mechanism of the URM wall was thus the weak spandrel failure corresponding to the sequence of cracking [1].e URM wall failed due to shear failure in accordance with the cross diagonal cracks.

URM Wall Repairing.
In order to develop an e ective and convenient repair scheme for the earthquake damaged masonry walls, the damage mechanism and the magnitude of damage of the URM wall were the key parameters to be considered.e purpose of the present study is to evaluate the seismic performance and recovery results of the CRM wall which utilize limited CFRP grid.erefore, only the severely damaged areas, including the spandrels of second oor and the piers of the rst oor, were repaired with CFRP gird in the present study.It was expected to address the lower limit of repairing demand and its performance.Additionally, although double-side strengthening is usually recommended in the available design codes, like [25,26], a single side repair scheme was adopted in the present study with consideration of the application convenience and less interruption.
e repair procedure of the earthquake-damaged masonry wall could be summarized as follows: the broken bricks and mortar were rstly remedied using same strength mortar, but the completely broken bricks need to be replaced using same bricks.e surface of the repair areas were then cleaned to remove the irregularities and dust after the repaired mortar being hardened.In order to secure the performance of the CFRP grid repair scheme and prevent the premature cutting fracture of the CFRP grids, CFRP sheets were bonded at the edges of openings before bonding CFRP grids as presented in Figure 7. e CFRP sheet width was 100 mm, and the ber direction was across the edges.
e epoxy resin was only applied to the repaired area, and the CFRP grids were then bonded.e CFRP grid repairing system was cured for 24 hours before testing.e repaired masonry wall is schematically presented in Figure 7.   e failure process of the CRM wall could be divided to three stages: the predamage minor development stage, the new damage development stage, and the strength decrease stage.When the top lateral displacement was below ±6 mm, the residual displacement was quite small after unloading.When the top lateral displacement reached to the rst cycle of +3 mm, the breakage sound of the hardened epoxy resin could be heard.It can be attributed to the development of the existing cracks.When the top lateral displacement continuously increased, no apparent cracks occurred or widened, whereas the epoxy resin fracture sound could be occasionally heard.When the top lateral displacement reached to ±6 mm, the 1-A region displayed new cracks, implying the limit of predamage minor development stage.
e corresponding displacement range of the new damage development stage was ±7 mm to ±22 mm.Following the completion of the rst loading cycle at the ±7 mm, the CFRP grid near the center of 1-C region debonded, and the existing cracks in this region widened.
e lateral load was turned to single cycle at each load level thereafter to match with the loading history of URM wall.When the top lateral displacement reached to ±8 mm, the 1-D region displayed new cracks, the CFRP grid at the center of 1-B region simultaneously debonded, and the existing cracks of this region widened as consequence.With the top lateral displacement reaching to ±9 mm, the CFRP grid of the 2-AB region started to debond, and the cracks of this region widened.As the top lateral displacement reaching to ±10 mm, the 2-CD and 2-A regions showed new cracks.In the meantime, the CFRP grid near the center of 2-CD region debonded.While the top lateral displacement reached to ±11 mm, the cross diagonal cracks of the 1-B and 1-C regions became apparently widened, the 1-A and 1-D regions displayed fully connected cross diagonal cracks.When the top lateral displacement increased to ±15 mm, the CFRP grid at the center of 2-BC region started to debond, and the existing cracks in the region widened.Until this lateral displacement level, all ve repaired areas exhibited debonding failures.As the top lateral displacement continuously increased, the existing cracks widened with the appearance of new cracks and the CFRP grid gradually debonded from the masonry.With the top lateral displacement reaching to ±20 mm, the CRM wall reached the negative maximum bearing capacity with the widening of the 3-AB, 3-BC, and 3-CD regions existing cracks.After completion of the loading cycle at the ±22 mm, all existing cracks became wider and all CFRP grids partly debonded from the masonry.
e CRM wall achieved the positive maximum bearing capacity at this load level as well.
e corresponding displacement range of the strength decrease stage was ±23 mm to ±28 mm.At this stage, the cracks developed along with some mortar and broken bricks on the repairing areas falling o .e spandrels of the rst oor showed a large shear deformation.Following the completion of the loading cycle at the ±28 mm, all CFRP grids dramatically debonded, and the unrepaired areas were severely damaged.Meanwhile, the lateral load of the CRM wall reduced to 85% of the peak load, and the test was terminated accordingly.
e nal failure and cracking schematic diagram of the CRM wall are presented in Figure 8. e details of failure were shown in Figure 9.
e debonding failure mostly initiated from the center of repaired regions and propagated to the edges.It was noticed that the CFRP gird was not fully debonded from the masonry because the additional CFRP sheets bonded at the edges of openings which can e ectively prevent the propagation of debonding failure.It may be concluded that the failures of the CRM wall developed from the lower oor to the higher oor according to the sequence of failure.Furthermore, the unrepaired areas cracked before the occurrence of debonding failure of the same oor.

Discussion
In this section, the seismic performance of the model wall prior to and after repairing was quantitatively analyzed.e e ectiveness of the adopted repair scheme was evaluated based on the experimental results.

Failure Mechanism.
In the present study, the URM wall under the in-plane quasistatic loading failed in the sheardominant failure mode, which was mainly characterized by the cross diagonal cracks occurred in both spandrels and piers.Also, the failure mechanism was considered as a typical weak spandrel failure because the spandrels of second oor cracked before the occurrence of cracks in piers of the rst oor.
e repairing mechanism of FRP grid mainly takes the advantages of high tensile strength and Young's modulus of ber, which can e ectively prevent the occurrence of cracks.Furthermore, the bonded FRP crossing the local cracks contributes bridge e ects to secure the structure stability and integrity and to restrain the global deformation.
e bidirectional ber structure of the grid is more e ective to restrict the diagonal shear crack failure [22,27,28].
It needs to be stressed that the failure of CRM wall was largely a ected by the magnitude of damage and repair scheme [13,19].e failure of CRM wall in the present study consisted of the CFRP grid debonding failure and shear diagonal cracks in the unrepaired masonry areas.
e sequence of CRM wall failure strongly depended on Advances in Civil Engineering the magnitude of damage, extent of damage, and repair scheme.e unrepaired piers of the rst oor cracked prior to the debonding failure of repaired piers at the same oor, indicating that the failure mechanism shifted from the weak spandrel failure to the weak pier failure due to the application of CFRP grids.e weak pier failure is the preference because it rarely leads to the collapse of the entire wall compared with the weak spandrel failure [1,7].Also, the reason why no ber fracture occurred may be due to the weaker strengthening.e failure mode usually corresponding to strong strengthening, like ber fracture, is the preference because the advantages of high strength of FRP can be fully utilized.

Hysteretic Response and Skeleton Curve.
e hysteretic response represents the detailed relationship of lateral displacement and the corresponding load.It demonstrates the deformation characteristics, the sti ness degradation, and the energy dissipation of the structures during cyclic load.e hysteretic and skeleton curves of each oor of the model wall prior to and after repairing are presented in Figures 10 and 11.
From the comparison of the hysteretic and skeleton curves of the model wall at each oor, it can be found that the seismic shear bearing capacity of the URM wall was 235.7 kN.It was e ectively restored to 194.3 kN after CFRP grids repairing.e shear bearing capacity of was restored to 82.4%, 84.7%, and 83.0% for the rst, second, and third oor, respectively.
e hysteresis curves of the URM wall displayed a certain pinching phenomenon, whereas the CRM wall curves exhibited fatter envelope curve, demonstrating an improved energy dissipation capacity.Due to the heavy damage of the URM wall and the limited repair areas, the secant sti ness of the CRM wall did not recover to the undamaged state as shown in Figure 11(b).

Sti ness Degradation.
e secant sti ness of the model wall is expressed by where |±F max,i | is the absolute value of the positive and negative peak lateral loads of the ith cycle, and |±x max,i | is the absolute value of displacements corresponding to the   positive and negative peak lateral loads of the ith cycle.In the case of two cycles prior to cracking, the sti ness was calculated by the rst cycle.e sti ness degradation curves presented in Figure 12 showed that the initial secant sti ness of the CRM wall was lower than that of the URM wall. is moderate sti ness recovery can be attributed to the severe damage of URM wall and the limited repairing scheme.
For the URM wall, the sti ness degradation of the elastic stage was signi cantly greater than the deformation development stage.In terms of the CRM wall, prior to the rst new crack occurrence (±6 mm), the sti ness degradation of this stage was apparently greater compared to the new damage development stage.Compared to the URM wall, since the CFRP grid restricted the occurrence and development of cracks, the sti ness degradation of the CRM wall was milder than the URM wall.

Displacement Ductility.
e displacement ductility of the model wall refers to the deformability of the masonry wall without signi cant loss of shear bearing capacity.In general, the ductility magnitude of the structure is expressed by the ductility coe cient μ which can be assessed as a ratio of displacement at the ultimate state d u , 85% of peak load in the present study, to the displacement at the attained elastic limit d y , like the appearance of rst crack, as.
Because the initiation of cracking state of each oor of CRM wall was di cult to capture, in the present study, the displacement ductility of the entire wall was analyzed.To simplify the calculation, the method proposed by Tomaževič [29] was adopted to idealize the actual envelope load-displacement curve as an ideal elastic-plastic relationship.
e idealized maximum strength R max,i is evaluated by assuming the same energy dissipation capacities of the actual and idealized structure, which is the Advances in Civil Engineering area enveloped by either load-displacement curve.e secant sti ness at the formation of the rst crack of the idealized curve K e was de ned as the ratio of the load to the corresponding displacement at the initiation of the cracks as where R cr and d cr are the lateral shear load and corresponding displacement at the initiation of cracks, respectively.When idealizing the actual curve, the idealized maximum lateral shear load R max,i can be calculated as Tomaževič [29].
where R max,i is the area enveloped by the actual loaddisplacement curve, and d 0.85R max is the lateral displacement at the ultimate state.e displacement at the idealized elastic limit thus d e,i can be evaluated as e ductility coe cient μ can be eventually determined according to the idealized load-displacement curve as e obtained idealized envelope load-displacement curves are presented in Figure 13.Consequently, the ductility coe cient of the URM wall was 2.35, and it increased to 2.41 for the CRM wall. is promotion was because CFRP grids e ectively postponed or even prevented the appearance and development of the cracks.

Energy Dissipation Capacity.
e hysteretic loop area of each displacement level represented the energy dissipation of the corresponding state.Figure 14 presents the energy dissipation of each oor at every displacement level of the wall prior to and after repairing.It can be found that the energy dissipations of the walls prior to and after repairing were approximately identical before the rst new crack appearance in the CRM wall when the top displacement reached to ±6 mm. e energy dissipation of the walls prior to and after repairing was mainly attributed to the rst and second oors, leading to these two oors severe damaged.For the URM wall, after reaching to the peak load (±15 mm), the energy dissipation of the rst oor signi cantly increased compared to the second oor.For the CRM wall, when the top displacement of the CRM wall reached to ±15 mm, as all CFRP grids exhibited debonding failure, the energy dissipation of the rst oor signi cantly increased compared to the second oor.e energy dissipations of both rst and second oors of CRM wall were almost equivalent to these of the URM wall at the same displacement level, indicating that the energy dissipation capacity was successfully restored due to the CFRP grid repairing.However, due to the fact that the third oor was unrepaired, the corresponding energy dissipation was not restored.When the top lateral displacement of the CRM wall reached to ±26 mm, the energy dissipation of each oor started to decrease, indicating that the CFRP grid displayed severe debonding failure and the wall severely damaged.
Figure 15 shows the percentage of energy dissipation of the entire wall contributed from each oor.e development trends of the percentage of energy dissipation contributed from each oor of both URM and CRM walls were almost similar.It can be found that the percentage of energy dissipation contributed from the third oor continuously decreased.On the contrary, the percentages of energy dissipation contributed from both rst and second oors constantly increased.
In terms of URM wall, once the rst crack occurred (±7 mm), the percentages of energy dissipation contributed from the rst and second oors were greater than those from the third oor because the damages intensively concentrated in the lower two oors.In the deformation development stage of the URM wall (±8 mm to ±15 mm), the percentage of energy dissipation contributed from the second oor was greater than that from the rst oor because heavy damages occurred in the spandrels of the second oor.After the peak load of the URM wall, the energy dissipation capacity of the entire wall mostly contributed from the rst oor because the heavy damages shifted to the piers of the rst oor.
For the CRM wall, after all repaired piers of the rst oor, 1-C, and 1-B regions starting to debond (±9 mm), the energy dissipation capacity of entire wall mostly shifted to the second oor due to the initiation and development of debonding in the spandrels of second oor.After the top lateral deformation reaching to ±15 mm, where all repaired spandrels of second oor exhibited debonding failure, the major contributions on the energy dissipation of entire wall shifted back the rst oor.After the peak load (±22 mm), the percentages of energy dissipation contributed from each oor approximately were constant.

Interstorey Drift Rotation Angle.
Interstorey drift rotation angle is another important factor to evaluate the ductility and seismic resistance of structures.Figure 16 presents the interstorey drift rotation angle of each oor of the wall prior to and after repairing.It is indicated that the interstorey drift ratio angles of the rst and second oors were greater because the damages mainly occurred at these two oors.e interstorey drift rotation angles of the rst and second oors of the CRM wall were almost identical as the URM wall.It is because the CFRP grid repair e ectively prevented the occurrence and development of the cracks.On the contrary, the interstorey drift rotation angle of the third oor of the CRM wall was higher compared to the URM wall.Moreover, the interstorey drift rotation angle decreased Advances in Civil Engineering from the rst oor to the third oor, which implied that the CRM and URM walls were in the shear type deformation.

Conclusions
In this paper, the seismic performance of a 1/3-scale threeoor masonry wall with openings prior to and after repair with CFRP grids was experimentally studied under in-plane quasistatic cyclic loading.e critical ndings are as follows: (1) In the adopted loading and boundary conditions, the model URM wall failed in weak spandrels mode.A milder CFRP gird repairing scheme was adopted in order to detect the lower limit of repairing demand.e repair scheme was determined based on the failure sequence and the magnitude of damage.
(2) It is demonstrated that the CFRP grid as a remedial technique could e ectively prevent and postpone the occurrence as well as the development of cracks.e failure mode of CRM wall under the in-plane quasistatic cyclic loading consisted of the CFRP grid debonding failure and shear diagonal cracks in unrepaired masonry.e sequence of the CRM wall failure also depended on the magnitude of damage and repair scheme.e failure mechanism may shift from weak spandrel to the preferred weak pier behavior.(3) In the present study, the seismic shear bearing capacity of the CRM wall was restored to 82.4% of the URM wall under the area-based reinforcement ratio of 17.5%.e seismic resistance of masonry wall, such as ductility, deformability, and energy dissipation capacity, has e ectively recovered or enhanced.(4) e initial secant sti ness of the masonry wall was not fully recovered because of the heavy damages and limited repair areas.In order to furtherly improve the seismic performance of masonry wall, greater amount of FRP grid may be recommended.Advances in Civil Engineering

Figure 1 :
Figure 1: Description and Segmentation of multistorey masonry wall (mm) (number-XX represents spandrels and number-X represents piers).

Figure 6 :
Figure 6: Final failure and crack pattern of the URM wall.(a) Final failure of the URM wall from the south side.(b) Crack schematic diagram of URM wall.

4
Advances in Civil Engineering 3.3.Test of CRM Wall.

Figure 7 :
Figure 7: Repair scheme of the damaged URM wall.

Figure 8 :
Figure 8: Final failure and crack pattern of CRM wall.(a) Failure of the CRM wall from the south side.(b) Crack schematic diagram of CRM wall.

Figure 9 :
Figure 9: Failure details of CRM wall.(a) Failure of the CRM wall from the north side.(b) Debonding failure in 2-CD region.(c) Debonding failure in 1-B region.

Figure 10 :
Figure 10: Hysteresis curves of the URM and CRM walls.(a) Hysteresis curves of 1st the oor.(b) Hysteresis curves of the 2nd oor.(c) Hysteresis curves of the 3rd oor.(d) Hysteresis curves of the entire wall.

Figure 11 :Figure 12 :
Figure 11: Envelope curves of URM and CRM wall.(a) Envelope curves of each oor.(b) Envelop curves of the entire wall.

Table 1 :
Properties of CFRP grid, CFRP sheet, and epoxy resin from manufacturers.