Dynamic response of masonry minarets strengthened with Fiber ...

Nat. Hazards Earth Syst. Sci., 11, 2011–2019, 2011 www.nat-hazards-earth-syst-sci.net/11/2011/2011/ doi:10.5194/nhess-11-2011-2011 © Author(s) 2011. CC Attribution 3.0 License.

Natural Hazards and Earth System Sciences

Dynamic response of masonry minarets strengthened with Fiber Reinforced Polymer (FRP) composites A. C. Altunis¸ik Karadeniz Technical University, Department of Civil Engineering, 61080, Trabzon, Turkey Received: 3 June 2011 – Revised: 15 June 2011 – Accepted: 16 June 2011 – Published: 20 July 2011

Abstract. Engineering structures strengthened with FRP composites are gaining popularity, and there is a growing need to understand and compare the behavior of these structures before/after FRP composite strengthening. In this paper, it is aimed to determine the dynamic response of masonry minarets before/after FRP composite strengthening. An ˙Iskenderpas¸a historical masonry minaret dating back to XVI century with a height of 21 m located in Trabzon, Turkey was selected as an application. Firstly, 3-D finite element model of the minaret was constituted using ANSYS software. Then, an analytical model of the minaret was analyzed using the 1992 Erzincan earthquake record, which occurred near the area, to determine the dynamic behavior. After this, the cylindrical body of the minaret was strengthened with FRP composite using different configurations and dynamic analyses were performed. Finally, dynamic responses of the minaret before and after FRP composite strengthening, such as displacements and maximum-minimum principal stresses, were compared. At the end of the study, it is seen that displacements had increased along the height of the minaret, maximum and minimum principal stresses occur at the region of transition segment and cylindrical body for all analyses. Also, it is seen from the earthquake analyses that FRP strengthening is very effective on the dynamic responses of the minaret.

1

Introduction

Historical structures are our cultural values left behind by thousands of years’ cultural accumulation. They pass our identity and civilization on to the next generations. Conservation of historical structures and carrying them into the Correspondence to: A. C. Altunis¸ik ([email protected])

future are our inevitable duty. In the last decade, the conservation, strengthening and the structural safety assessment of historical masonry structures such as minarets, towers, bridges and buildings have become of increasing concern, probably as a consequence of some dramatic events registered in the world. Tall structures by their nature are computationally intensive to analyze. They consist of thousands of degrees of freedom and when subjected to strong ground motion from a source, exhibit a very complex response (Krishnan, 2004). Minarets are one of the thin and tall engineered structures. These are distinctive architectural features of Islamic mosques and generally tall spires with onion shaped or conical crowns. Minarets are used for calling out the azan five times each day by a muezzin in order to signal people to come to prayers. Polymeric composites are advanced engineering materials with the combination of high-strength, high-stiffness fibers, and low-cost, light-weight, environmentally resistant matrices. Fiber reinforced polymers (FRPs) are a class of advanced composite materials that originated from the aircraft and space industries. They have been used widely in the medical, sporting goods, automotive and small ship industries. FRP has high strength to weight ratios, and excellent resistance to corrosion and environmental degradation (Mosallam, 2007; Zaki, 2011). It is very flexible and forms all kinds of shapes and is easy to handle during construction. With the increasing demand for infrastructure renewal and the decreasing cost for composite manufacturing, FRP materials began to be extensively used in civil engineering in the 1980s and continue to expand in recent years. In the literature, there is more paper exist about the structural behavior of engineering structures before and after FRP composite strengthening. Stierwalt and Hamilton (2005) examined the creep behavior of masonry walls strengthened with FRP composites compared to that of conventional reinforcement. Eight full-scale unreinforced concrete masonry

Published by Copernicus Publications on behalf of the European Geosciences Union.

the İskenderpaşa historic masonry minaret. As in Figure 1, the minaret is very thin and tall with one balcony on its body. 2012

A. C. Altunis¸ik: Dynamic response of masonry minarets

Figure 1 Some views of İskenderpaşa historical masonry minaret

Fig. 1. Some views of ˙Iskenderpas¸, a historical masonry minaret

The objective of this paper is to calculate the detailed dywalls were constructed for testing long-term deflections outnamic responses of a historical masonry minaret and comof-plane. Mosallam (2007) presented the results of a study Minarets offlexural threebehavior parts;of a pare base, and a counterpart. gallery. The thematoshaft, an FRP composite For thisbase pur- is focused onbasically evaluating theconsist out-of-plane ˙ pose, the Iskenderpas¸a masonry minaret located in the city two FRP composite systems for strengthening unreinforced foundation of the minaret. shaft is prothe thin, bodyTurkey of the minaret stairsA are centerslim of Trabzon, is selected as a and case study. red brick masonry walls. Ghosh andThe Karbhari (2007) vided details of an investigation into the strengthening effithree-dimensional finite element model of the minaret has created by ANSYS software and structural has the ciency of FRP- rehabilitated bridgeshaft deck slabs teststhe been place cylindrically in the to through provide necessary structural support foranalysis highly been performed. Then, the cylindrical body of the minaret conducted on slab sections cut from a bridge just prior to was strengthened FRP upper compositesection using different config- the demolition. shafts. Al-Saidy et al. (2008) conducted analytical that elongated The gallery is aan balcony encircleswiththe where urations and dynamic analyses were performed. At the end parametric study on the behavior of steel-concrete composite beam that has been with It CFRP In of dynamic responses before and after FRP commuezzins call out strengthened to prayer. is plates. covered bythe astudy, roof-like canopy and adorned with posite strengthening such as displacements and maximumaddition, the effect of girder damage on the overall load disminimum principal stresses are compared. tribution of a typical short span composite bridge has been ornamentation such as decorative bricks and decorated with painted tile, cornices, arches investigated for various load cases. Mortazaei et al. (2010) the seismic response of FRP strengthened typianddetermine inscriptions. Similar to classical Ottoman style minarets, the İskenderpaşa minaret cal existing RC buildings subjected to near-fault ground mo˙ 2 Iskenderpas ¸a historical masonry minaret tions. Kim and Harries (2010) emerged a modeling approach consist of the a footing astimber a base; transition segment, cylindrical or polygonal body as a to predict behavior of beamspulpit, strengthened with ˙ The Iskenderpas ¸a historical masonry minaret has a total FRP composites. A 3-D finite element analysis model is forheight of 20.5 m and is located in a heavy traffic and crowded shaft; balcony; upper partconstitutive of the characteristics minaret body; spire; and the end ornament as shown in mulated, based on the orthotropic area in Trabzon city center, Turkey. The minaret was built by of timber species. Zaki (2011) studied the behavior of FRP a governor of a Trabzon (˙Iskender Pasha) in the XVI century. Figure 2. circular columns under combined axial loads Stones and bricks were used together in construction of the strengthened and biaxial bending moments. Tao et al. (2011) performed a minaret with beautiful decorations under the balcony. Scareseries of laboratory tests investigating the behavior of a large crows are decorated with emblems and circular motifs. Figmodel masonry arch bridge repaired with externally bonded ure 1 shows some views of the ˙Iskenderpas¸a historic masonry FRP composites on its intrados. A two-span, single-ring minaret. As in Fig. 1, the minaret is very thin and tall with semi-circular brick arch bridge was selected for this study, one balcony on its body. complete with fill material. Besides these studies, there 5/19 is Minarets basically consist of three parts; a base, a shaft, not more paper exist only a few paper (not enough for literand a gallery. The base is foundation of the minaret. The ature) exist relate to dynamic responses of FRP strengthened shaft is the thin, slim body of the minaret and stairs are place thin and tall historical masonry structures such as minarets. cylindrically in the shaft to provide the necessary structural Nat. Hazards Earth Syst. Sci., 11, 2011–2019, 2011

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Figure 2 Segments of the classical Ottoman style and İskenderpaşa minarets General arrangement drawings of the entire minaret are shown in Figure 3 where the geometrical properties of the minaret are given. In addition to these dimensions, there is a 0.20m diameter stone block in the middle of the minaret. Around the stone block, there are Figurefrom 2 Segments stylestep andheight. İskenderpaşa minarets 83 stairs the flooroftothe theclassical balconyOttoman with 0.20m Each stair has an inner and

Fig. 2. Segments of the classical Ottoman style and ˙Iskenderpas¸a minarets.

outer radius as 0.10m and 0.60m, respectively. General arrangement drawings of the entire minaret are shown in Figure 3 where the geometrical properties of the minaret are given. In addition to these dimensions, there is a 0.20m diameter stone block in the middle of the minaret. Around the stone block, there are 83 stairs from the floor to the balcony with 0.20m step height. Each stair has an inner and outer radius as 0.10m and 0.60m, respectively.

Figure 3 Geometrical properties of the minaret Fig. 3. Geometrical properties of the minaret.

support for the elongated shafts. The gallery is a balcony General arrangement drawings of the entire minaret are 6/19 that encircles the upper section where the muezzins call out shown in Fig. 3 where the geometrical properties of the to prayer. It is covered by a roof-like canopy and adorned minaret are given. In addition to these dimensions, there is with ornamentation such as decorative bricks and decorated a 0.20 Figure 3 Geometrical properties of m thediameter minaretstone block in the middle of the minaret. with painted tile, cornices, arches and inscriptions. Similar Around the stone block, there are 83 stairs from the floor to to classical Ottoman style minarets, the ˙Iskenderpas¸a minaret the balcony with 0.20 m step height. Each stair has an inner consisting of a footing as a base; pulpit, transition segment, and outer radius of 0.10 m and 0.60 m, respectively. cylindrical or polygonal body as a shaft; balcony; upper part 6/19 of the minaret body; spire; and the end an ornament, as shown in Fig. 2.


Nat. Hazards Earth Syst. Sci., 11, 2011–2019, 2011

the SOLID186 element is shown in Figure 4. When the structural solid geometry property of the SOLID186 element is examined, it can be seen that the elements appear to be made 2014

of tetrahedral, pyramid or prism options in the finiteA.element mesh model of the minaret. C. Altunis ¸ik: Dynamic response of masonry minarets

Figure 4 A schematic view and properties of the SOLID186 element

Fig. 4. A schematic view and properties of the SOLID186 element. Table 1. Material properties used in analyses of the minaret. Elements

Material Properties

Minaret FRP Composite

Directional

Modulus of Elasticity Symmetry Type

Isotropic Orthotropic

2.00E9 3.3E10

7/19

total thickness of the FRP is chosen as 6 mm. Element stiffness behavior is considered as tensile and compressive. Extra displacement shapes are included, but extra stress outputs

Poisson’s Ratio (N m−2 )

Mass per unit Vol. (kg m−3 )

Shear Modulus (N m−2 )

0.20 0.25

2169 1790

– 1.32E10

are not considered.

3

a) Before strengthened

b) After strengthened

c) Stone block and stairs

Figure 5 3D finite element models of the minaret before and after FRP composite strengthened including concrete block and stairs

Fig. 5. 3-D finite element models of the minaret before and after FRP composite strengthening andcomposite stairs A total of 7 natural frequencies of including the minaret concrete before and block after FRP strengthening were obtained with a range between 1.09-12.16 Hz and 1.61-19.07 Hz, respectively. When the first seven modes are examined for both analyses, the first four

Finite element modeling

Three-dimensional finite element models of the minaret before and after FRP composites strengthening were developed using the ANSYS software (ANSYS, 2008). This program can be used for linear and non-linear, static and dynamic analyses of 3-D model structures. In this paper, based on its physical and mechanical properties, the program was used to determine the dynamic behavior of the minaret. Convergence studies about element size were performed and the optimum element sizes were chosen for both models. In the finite element models of the minaret, SOLID186 elements were used which exhibited quadratic displacement behavior. The element had 20 node and three degrees of freedom per node: translations in the nodal x, y, and z directions. In addition, it had the capability of plasticity, elasticity, creep, stress stiffening, large deflection, and large strains. A schematic view of the SOLID186 element is shown in Fig. 4. When the structural solid geometry property of the SOLID186 element is examined, it can be seen that the elements appear to

modes of the minaret are horizontal modes in the z and x directions, the fifth mode is a torsional mode and last two modes are horizontal modes in the z and x directions as seen in

Nat. Hazards Earth Syst. Sci., 11, 2011–2019, 2011 Figure 6.



2015

1st Mode

2nd Mode

3rt Mode

4th Mode

5th Mode

f1=1.09 Hz

f2=1.09 Hz

f3=5.59 Hz

f4=5.59 Hz

f5=9.78 Hz

6th Mode

7th Mode

f6=12.16 Hz f7=12.16 Hz

a) Before FRP composite strengthening

4. DYNAMIC RESPONSE OF THE MINARET Linear transient analyses of the İskenderpaşa historical masonry minaret before and after FRP composite strengthening were performed using ERZIKAN/ERZ-NS component of 1992 Erzincan earthquake (Mw=6.9) ground motion (Figure 7) (PEER, 2007). The element matrices were computed using the Gauss numerical integration technique (Bathe, 1996). The Newmark method was used in the solution of the equations of motion. Rayleigh damping constants were calculated nd between the first rthorizontal modethof the st

1 Mode

2 Mode

3 Mode

4 Mode

5th Mode

minaret and the seventh mode, assuming damping andHz Beta coefficients f1=1.61 Hz a 5%f2=1.61 Hzratio. Alpha f3=10.59 f4=10.61 Hz

f5=17.73 Hz

before and after FRP composite strengthened were calculated asb)0.616 andFRP 0.00146; 0.928 After composite

strengthening

6th Mode

7th Mode

f6=19.06 Hz f7=19.07 Hz

and 0.00082, respectively. Because of the large memory required for the analyses, only the

Figure 6 Natural frequencies and corresponding mode shapes of the minaret before and after FRP composite strengthening

first 6.5 second of the frequencies ground motions, is the effective duration, taken into before and after FRP composite strengthening. Fig. 6. Natural andwhich corresponding mode shapeswas of the minaret account in the calculations.

Acceleration (m/s²)

analysis is very important for thin and tall structures such as minarets. But, removing test samples from the histori3.0 cal masonry structures such as minarets was not allowed by 0.0 the related institution. So, initial material properties were -3.0 taken from the literature (Frunzio et al., 2001; Doangün et -6.0 al., 2006; Gentile and Saisi, 2007; Bayraktar et al., 2008; 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Bayraktar et al., 2009). For the structural strengthening of Time (s) Figure 7 The time-history of ground motion acceleration of 1992 Erzincan earthquake the minaret, woven carbon fiber fabric material was used. 10/19This material can be used for strengthening of reinforced Fig. 7. The time-history of ground motion acceleration of 1992 Erzincan. earthquake. concrete and masonry structures, brickwork and timber in The horizontal displacements along to the height of the minaret at the time of maximum case of flexural and shear load due to increase of loading response before and after FRP composite strengthened are given in Figure 8. It is seen that capacity, changes of building utilisation, repair of defects, the displacements increase along the height of the minaret and that the maximum be made of tetrahedral, pyramid or prism options in the finite prevention of defects caused by earthquakes and meeting of displacement (at mesh the topmodel of the of minaret) is obtained before and after FRP composite element the minaret. changed standards. The values of the material properties strengthened as 32.84 and 12.71 cm, respectively. Also, the timeboundary histories of condithe horizontal used in analyses of the minaret are given in Table 1. The Determination of material properties and displacements (withmust a peak be value of) 32.84 and 12.71 cm analyses at the top of minaret was taken in place rock soil. As initial boundary tions that taken intocmaccount in for theboth finite element 6.0

Max=0.515g

the İskenderpaşa historical masonry minaret subjected to the Erzincan ground motion is presented in Figure 9.

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2016

A. C. Altunis¸ik: Dynamic response of masonry minarets A total of 7 natural frequencies of the minaret before and after FRP composite strengthening were obtained with a range between 1.09–12.16 Hz and 1.61–19.07 Hz, respectively. When the first seven modes were examined for both analyses, the first four modes of the minaret are horizontal modes in the z and x directions, the fifth mode is a torsional mode and last two modes are horizontal modes in the z and x directions, as seen in Fig. 6.

14 21

7 Height (m)

Height (m)

21

14

Before Strengthened

4

Dynamic response of the minaret

After Strengthened

Linear transient analyses of the ˙Iskenderpas¸a historical masonry minaret before and after FRP composite strength0 9 18 27 36 ening were performed using ERZIKAN/ERZ-NS compoDisplacements (cm) Before Strengthened nent of 1992 Erzincan earthquake (Mw = 6.9) ground moStrengthened Figure 8 Variation of maximum displacements After along to the height of the minaret at the 0 Fig.of8.maximum Variationresponse of maximum displacements along to the height of tion (Fig. 7) (PEER, 2007). The element matrices were time before and after FRP composite strengthened 0 9 18 27 36 Displacements (cm) before and after FRP the minaret at the time of maximum response computed using the Gauss numerical integration technique Figure 8 Variation of maximum displacements along composite strengthening. 40 40 to the height of the minaret at the (Bathe, 1996). The Newmark method was used in the solutime of maximum response before and after FRP composite strengthened tion of the equations of motion. 40 40 Rayleigh damping constants were calculated between the 20 20 first horizontal mode of the minaret and the seventh mode, 20 20 assuming a 5 % damping ratio. Alpha and Beta coefficients 0 0 before and after FRP composite strengthening were calcu0 0 lated as 0.616 and 0.00146; 0.928 and 0.00082, respectively. Because of the large memory required for the analyses, only -20 -20 -20 -20 the first 6.5 second of the ground motions, which is the efMax=32.84cm Max=12.71cm Max=32.84cm Max=12.71cmfective duration, was taken into account in the calculations. -40 -40 -40 -40 0.0 1.6 3.3 4.9 6.5 0.0 1.6 3.3 4.9 6.5 0.0 1.6 3.3 Time (s) 4.9 6.5 0.0 1.6 4.9 6.5 The horizontal displacements along to the height of the Time (s) 3.3 Time (s) Time (s) minaret at the time of maximum response before and afFigure 9 Time histories of maximum displacements at the top of minaret for both analyses Figure 9 Time histories of maximum displacements at the top of minaret for both analyses ter FRP composite strengthening are given in Fig. 8. It Fig. 9. Time histories of maximum displacements at the top of is seen that the displacements increase along the height of Figure 10 points out the contours of maximum horizontal displacement corresponding to minaret for both analyses. both analyses. These displacement contours represent the distribution of the peak values the minaret and that the maximum displacement (at the top Figure 10 points out the contours of maximum horizontal displacement corresponding to reached by the maximum displacement at each point within the section. of the minaret) is obtained before and after FRP composite both analyses. These displacement contours represent the distribution the peak values conditions, all of the degrees of freedom under the of footing strengthening as 32.84 and 12.71 cm, respectively. Also, the reached bypart the maximum displacement at each as point within the section. of the minaret are selected fixed. time histories of the horizontal displacements (with a peak The 3-D finite element models of the minaret before and value of) 32.84 cm and 12.71 cm for both analyses at the top after FRP composite strengthening including concrete block of the ˙Iskenderpas¸a historical masonry minaret subjected to and stairs are shown in Fig. 5. According to the convergence the Erzincan ground motion are presented in Fig. 9. 12/19 studies, the optimum mesh size is chosen as 30 cm and 20 cm Figure 10 points out the contours of maximum horizonbefore and after FRP composite strengthening, respectively. tal displacement corresponding to both analyses. These disThe mesh size may be reduced. But, when the element and placement contours represent the distribution of the peak val12/19 node numbers are increased, the analyses duration and toues reached by the maximum displacement at each point tal volume increase. In the FRP composite strengthening within the section. model, the thickness of FRP is very small when compared The time histories of the maximum and minimum prinwith the thickness of cylindrical body of the minaret. Thus, cipal stresses of the minaret subjected to the Erzincan 1992 20 cm mesh size is used in the finite element analyses after earthquake are plotted in Fig. 11. As shown in Fig. 11, the FRP composite strengthening. Therefore, 18620 and 95841 highest maximum and minimum principle stresses occurred SOLID186 elements are used in the finite element models. before FRP composite strengthening. Also, maximum and In the composite strengthening model, the cylindrical body minimum principal stress contours of the minaret before and of the minaret is wrapped by four layers of FRP and total after FRP composite strengthening are given in Figs. 12 and thickness of the FRP is chosen as 6 mm. Element stiffness 13. These stress contours represent the distribution of the behavior is considered as tensile and compressive. Extra dispeak values reached by the maximum principal stress at each placement shapes are included, but extra stress outputs are point within the section. It is clearly seen from Figs. 12 not considered. and 13 that FRP composite is very effective in the principal stresses. (cm)

7

Displacements Displacements (cm)

Displacements (cm)

Displacements (cm)

0



a) Before FRP composite strengthened


2017

The time histories of the maximum and minimum principal stresses of the minaret subjected to Erzincan 1992 earthquake are plotted in Figure 11. As shown in Figure 11, the a) Before FRP composite strengthened highest maximum and minimum principle stresses occur before FRP composite

b) After FRP composite strengthened

strengthened. Also, maximum and minimum principal stress contours of the minaret before and after FRP composite strengthened are given in Figures 12 and 13. These stress contours represent the distribution of the peak values reached by the maximum principal

Figure 10 Maximum displacement contours of İskenderpaşa historical minaret

˙ Fig. 10. Maximum displacement contours of Iskenderpas ¸a historical minaret. stress at each point within the section. It is clearly seen from Figures 12 and 13 that FRP 8

Max=6.90 MPa

6 4 2 0 b) After FRP composite 0.0 1.6 3.3 strengthened

Time (s)

4.9

Minimum Principal Stress (MPa)

Maximum Principal Stress (MPa)

composite is very effective in the principal stresses.

13/19

0 -2 -4 -6 Min=6.77 MPa

-8 0.0

6.5

1.6

3.3

Time (s)

4.9

6.5

– From the modal analyses of the minaret, a total of 7 natural frequencies before and after FRP composite strengthening were obtained with a range between 1.09–12.16 Hz and 1.61–19.07 Hz, respectively. When the first seven modes are examined for both analyses, the first four and last two modes are horizontal modes in the z and x directions and the fifth mode is a torsional mode. It is seen that FRP composite brought stiffness into the structural system.

8

Figure 10 Maximum displacement contours of İskenderpaşa historical minaret Max=4.95 MPa 0 Minimum Principal Stress (MPa)

Maximum Principal Stress (MPa)

(a) Before FRP composite strengthened

6

-2 13/19

4 2 0 0.0

1.6

3.3

4.9

Time (s)

6.5

-4 -6 Min=4.85 MPa

-8 0.0

1.6

3.3

Time (s)

4.9

6.5

(b) After FRP composite strengthened Figure 11 The time histories of maximum and minimum principal stresses of İskenderpaşa historical minaret before and after FRP composite strengthened

Fig. 11. The time histories of maximum and minimum principal stresses of the ˙Iskenderpas¸a historical minaret before and after FRP composite strengthening. 14/19

5

Conclusions

This paper aimed to determine the dynamic response of masonry minarets before and after FRP composite strengthening. The ˙Iskenderpas¸a historical masonry minaret with a height of 21 m located in Trabzon, Turkey was selected as an application. A 3-D finite element model of the minaret was constituted using ANSYS software and dynamic behavior was determined using 1992 Erzincan earthquake record before and after the FRP composite strengthening. The following observations can be deduced from the study: www.nat-hazards-earth-syst-sci.net/11/2011/2011/

– Rayleigh damping constants are calculated between the first horizontal mode of the minaret and the seventh mode, assuming a 5 % damping ratio. Alpha and Beta coefficients before and after FRP composite strengthening are calculated as 0.616 and 0.00146; 0.928 and 0.00082, respectively. – An earthquake analysis of the minaret before and after FRP composite strengthening was performed using the 1992 Erzincan ground motion. It can be seen from the analysis that horizontal displacements increased along to the height of the minaret for both analyses and that the maximum displacement (at the top of the minaret) was obtained before and after FRP composite strengthening as 32.84 and 12.71 cm, respectively. – Maximum and minimum principal stresses occurred at the region between the transition segment and the cylindrical body before FRP composite strengthening, and they are equal to 6.90 and −6.77 MPa, respectively. Therefore, it is likely that probable damages and cracks due to earthquake loads can occur at the region between the transition segment and the cylindrical body. – To eliminate the probable damages and cracks, the cylindrical body of the minaret was strengthened with FRP composite and dynamic analyses were performed. FRP can be applied to the circular surfaces. The pulpit Nat. Hazards Earth Syst. Sci., 11, 2011–2019, 2011

2018


a) Maximum principal stressess

a) Maximum principal stressess

b) Minimum principal stressess

b) Minimum principal stressess Figure 12 Maximum and minimum principal stress contours of İskenderpaşa historical minaret obtained before FRP composite strengthened Figure 13 Maximum and minimum principal stress contours of İskenderpaşa histori

Fig. 12. Maximum and minimum principal stress contours of the ˙Iskenderpas¸a historical minaret obtained before FRP composite strengthening 15/19

minaret obtained after FRP composite strengthened

Fig. 13. Maximum and minimum principal stress contours of the ˙Iskenderpas¸a historical minaret obtained after FRP composite strengthening 16/19

has a polygon surfaces and the transition segment has a variable polygon surfaces. So, only the cylindrical body of the minaret was wrapped by FRP. From the analyses, it is seen that maximum and minimum principal stresses were obtained as 4.95 and −4.85 MPa, respectively. – It is seen from the study that FRP composite strengthening is very effective in the dynamic response of the historical minaret. To determine the static, dynamic, linear and nonlinear structural behavior of the historical masonry structures such as bridges, minarets, belltowers, dams, buildings, which are our cultural values that left behind by thousands of years’ cultural accumuNat. Hazards Earth Syst. Sci., 11, 2011–2019, 2011

lation, FRP composite strengthening should be considered and the responses should be compared before the FRP composite strengthening.

Edited by: M. E. Contadakis Reviewed by: two anonymous referees


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