. In this paper, the seismic response control of offshore jacket -type platform equipped with Shape Memory Alloy (SMA) braces is investigated. Concerning the properties of the SMAs, a new connection is introduced in order to make the most of it. Based on an actual platform structure and its mechanical model, the optimized localization of SMAs are found by damage propagation under pushover loadings. To evaluate the possibility of adopting the innovative bracing system and its efficiency, the dynam ic responses of 3 -D model of the existing 4 -legged offshore platform placed in Persian Gulf (SPD12) is compared to the ones with SMA braces. The results show that using an SMA element is an effective way to develop the API recommendations and improve the d ynamic response of offshore platforms subjected to earthquake excitations. Implementing the SMA braces can lead to a reduction in residual displacement, deck level displacement, elements and connections forces, and base shear compare d to the steel tubular braces model . Keywords : platform, SMA, seismic assessment, offshore, jacket , SMA connection 1. Introduction Offshore platforms should be safe and comfortable to guarantee the living and working conditions of workers. However, many offshore platforms have been installed in seismic regions and can be damaged easily by earthquakes. Therefore, controlling the struct ure under seismic loading needs to be conducted. The seismic control of the fixed jacket -type offshore platforms can be useful to reduce the required construction materials volume, increase the service life, and improve the reliability of the structure und er seismic loads and oscillations. There are many methods for the control of structures subjected to earthquake -induced loads, but the application of these methods needs to be considered and assessed for offshore structures. One innovative method which is not mainly considered in offshore platforms yet is utilizing Shape Memory Alloys (SMAs) to control these structures under seismic loading. The Nitinol (which is very common SMA type) is a kind of intelligent material that can undergo large recoverable strains of about 6-9% without any plasticity [1,2]. SMAs are effective material for seismic application due to good fatigue resistance, long -term reliability even after strong earthquakes, high dampin g capacity, and the recovery of strains [ 3-6]. Many researchers have studied using SMAs in seismic control of buildings and bridges. Asgarian and Moradi [ 7] investigated the seismic performance of steel frames equipped with SMA braces. Wilde et al [ 8] asse ssed base isolation system with shape memory device for elevated highway bridges that could control the displacements of the rubber bearing. A critical review for the applications of using SMAs in seismic resistant design is provided by Desroches and Smith [ 9]. Tamai et al [ 10] investigated the application of SMA rod to * Correspondence author , Email: kbargi@ut.ac.ir , Tel: +989121128923 exposed -type column base experimentally and analytically. Haque and Alam [ 11] investigated the feasibility of the novel piston -based self -centering bracing (PBSC) system and predic ted its load - deformation hysteresis during seismic events. Some researchers are studied on steel structures connections using SMAs [ 12-16]. On the other hand, assessment of jacket -type platforms equipped with SMAs has seldom been studied. Li et al [ 6] inve stigated the seismic control of offshore platform structures with SMA dampers and found that the SMA damper is an effective control device for these structures. Shabakhty and Givkay [ 17] used SMA braces to control the response of fixed offshore platforms u nder extreme wave loading, and Aghajani Delavar et al. [18] did similar research under seismic loading, but they didn’t present any optimum and practical method to use SMAs in braces. In this research, the seismic response behavior of fixed jacket -type offshore platforms equipped with SMAs being used in optimum locations is investigated and compared with the ones without SMAs , and a practical method for applying the SMAs to the brace elements is proposed. 2. FE modeling and analysis 2.1 Details of the case study In this research, a 3 -D model of SPD12 jacket -type platform located in Persian Gulf is selected as a case study. The jacket which is fixed to the ground by 4 piles has four main legs located in 71.4 - meter water depth. The top sid e of the platform is 20.50m 24.25m and consists two distinguished parts; main module and Free Wate r KO drum module (FWKO module). The main module has four decks, and the FWKO module has three decks. Mudline elevation of the platform has 33.25m 38.50m plan dimension. General configuration of SPD12 jacket platform is shown in Fig.1. Fig. 1 Perspective plot of SPD12 jacket platform [19] 2.2 Modeling of the jacket Considering the effects of hydrodynamic forces and added mass are essential to model the tubular members of the jacket. Therefore, the buoyancy forces (effect of hydrodynamic forces) and the simplified added mass (calculated by the added mass coefficients) are assigned to the model. Computer model is created using the SAP2000 software [ 20] which is more powerful in analyzing such an intricate model than other software and useful for modeling of tubular members and assignments of nonlinear behavior of elemen ts due to its user -friendly modeling. In dynamic analysis, the mass should contain the mass of the platform associated with gravity loading including the platform dead weight, actual live loads and 75% of the maximum supply and storage loads [ 21]. Moreover , additional moment due to P- effects is considered because the vertical load in this structure is large . For modeling of the jacket -type platform, the properties of steel are presented in Table 1 . Table 2 indicates the yield stress of the steel considering the thickness of the tubular elements. Bilinear stress - strain curve with 3% of the elastic slope and maximum ductility of 14 is modeled for considering the material non -linearity (Fig. 2). The elements are beam -column due to the loading assignment to be more similar to the SPD12, and all the connections are moment resistant which are simulated as the real structure. The 5% damping ratio is considered for this simulation. Fig. 2. Steel material Table 1. Steel properties Grade Density Young’s Modulus  Poisson’s Ratio S355 7850 kg/m3 200 GPa 0.3   Table 2. Yield stress of steel (N/mm2) Thickness in mm 16 16 40 63 80 100 40 63 80 100 150 350 345 335 325 315 295 2.3 Modeling of the interactions During the analysis of jacket -type offshore platforms simplified methods can be used to obtain the effects of interactions; soil -pile interaction and water -structure interaction , provided that the purpose of analysis is the st udy of global behavior of the structure . The main object of this article is the comparison of seismic responses with and without using of SMAs in the platforms relatively. Therefore, for considering the soil -pile interaction, the equivalent length method i s used. The equivalent length of the pile in loose clayey soils is suggested 8D -12D, where D is the diameter of the pile [ 22]. In this research, the value of 12D which is approximately equal to 18.3m is considered as the equivalent length of piles. For con sidering the water -structure interaction, the added mass coefficient is used to assign the calculated added mass to the elements. The added mass coefficients as a function of submergence are presented in Fig. 3 and Table 3. When the tubular element is full y submerged ( d>D ), the value for the vertical added mass coefficient is the same as that for the horizontal one [ 23]. Fig. 3 Vertical and horizontal added mass coefficients of cylinder as a function of submergence ratio d/D [23]  Table 3 Buoyancy and added mass coefficients of cylinder [23] Submergence ratio Dd Buoyancy/ gAw where 42D A= Added mass coefficient Vertical z w V V uA M C = Horizontal x w H H uA M C = 0.1 0.052 0.163 0.009 0.2 0.142 0.286 0.036 0.5 0.500 0.500 0.203 0.8 0.858 0.581 0.461 1.0 1.000 0.646 0.646 1.2 1.000 0.783 0.783 1.5 1.000 0.885 0.885 2.0 1.000 0.948 0.948 3.0 1.000 0.983 0.983 2.4 Modeling of the topside In assessing the jacket part, modeling the topside (deck) with precise details is not necessary. Thus, a simplified model is used to consider the real height of the structure. To do so, the columns are modeled , and membrane elements which are suitable in distribution of gravitational load are chosen to model the deck. Each deck is modeled as an independent diaphragm in order to have the ability to move relatively. 2.5 Modeling of the SMAs Over the past decades, constitutive models have been proposed by several researchers for capturing the behavior of the SMAs. In this paper, a constitutive model proposed by Fugazza [ 24] was selected to represent the super -elastic behavior of the SMAs. This kind of constitutive model can be simulated easily due to the few parameters it required . These parameters are the austenite to martensite starting stress ( 𝜎𝑠𝐴𝑆), the austenite to martensite finishing stress ( 𝜎𝑓𝐴𝑆), the martensite to austenite star ting stress ( 𝜎𝑠𝑆𝐴), the martensite to austenite finishing stress ( 𝜎𝑓𝑆𝐴), modulus of elasticity for austenite and martensite phases ( 𝐸𝑆𝑀𝐴 ) and the super -elastic plateau strain length ( 𝜀𝐿 ). The hysteresis loop of an SMA element looks like a fla g that has the benefit of some energy dissipation along with minimal residual deformations upon removal of loads. Fig. 4 represents the SMA model schematically which has no strength degradation during cycling, and the martensite and austenite modulus of el asticity are the same [25,26]. The mechanical behavior of the SMAs are provided in Table 4 which is based on the uniaxial cyclic tests carried out by DesRoches et al [ 27]. Fig. 4 Stress -strain relationship of SMA member: parameters needed for the model Table 4 Mechanical properties of SMA bars in numerical simulation Quantity 𝐸𝑆𝑀𝐴 𝜎𝑠𝐴𝑆 𝜎𝑓𝐴𝑆 𝜎𝑠𝑆𝐴 𝜎𝑓𝑆𝐴 𝜀𝐿 Value 27579 MPa 414 MPa 550 MPa 390 MPa 200 MPa 3.5% For modeling the super -elastic SMA behavior in SAP2000, multiple link elements can be used. By defining two link properties and assign them to two link elements in parallel, the SMA behavior can be obtained. A multi -linear plastic link u tilizing the pivot mod el is used to define the hysteresis loop, and a multi -linear elastic link is used to shift the hysteresis loop away from the origin. Fig. 5 shows the modeling of SMA element in SAP2000 in comparison to DesRoches’s model which is verified by experimental wo rks. Fig. 5 Verifying SMA modeling in SAP2000 with DesRoches model 2.6 Modal analysis A modal analysis is conducted to extract the mode shapes of the structur e and the corresponding periods with considering P - effect. Fig. 6 shows the first three mode shapes of the SPD12. As shown in Table 5, first 12 periods of the generated model are compared with the corresponding period of the structure . The first two periods of the structure are very similar to their corresponding generated model and other periods have about 10% variation in average due to the simplification of the model. a) Mode -1 b) Mode -2 c) Mode -3 Fig. 6 Mode Shapes of the platform  Table 5 Comparison of periods Mode Modal Period SPD12 Period Error (%) 1 2.957 3.004 1.5 2 2.506 2.565 2.3 3 2.081 1.638 -27.0 4 1.179 0.974 -21.0 5 1.145 0.945 -21.0 6 0.738 0.739 0.1 7 0.455 0.533 14.6 8 0.415 0.531 21.8 9 0.403 0.500 19.4 10 0.341 0.341 0.0 11 0.292 0.308 5.2 12 0.279 0.286 2.4 2.7 Pushover analysis Nonlinear static analysis is conducted to obtain the damage propagation in the structure to find places where the structure will be damaged first. Thus, defining hinges for all the main elements of the SPD12 is done and the structure is pushed with two kinds of loading; modal and constant pattern distribution of load. Due to the fully restrained moment frames and concentric braced frames of the platform, calculating parameters and numerical acceptance criteria for beams, columns, and braces are obtained with respect to FEMA [ 28] and Iranian code number 360 [ 29] to define hinges for nonlinear analysis. Due to the forces and configuration of the elements, component actions might be Deformation - Controlled (DC) or Force -Controlled (FC). Characteristics of the sections (like t/D ) cause the columns and most of the beam s to be FC. B y the pushover analysis, the initial elements that experience the collapse prevention (CP) are braces which are DC. As a result, damage distribution of each frame is obtained and using SMAs for controlling the seismic response of the structure can be optimized by this method . By conducting push over analysis, plastic hinges are formed in braces first, then spread to the other members which are investigated by Aghajani D elavar and Bargi [30]. The collapse spread process provides the opportunity to recognize the next potential member in which the plastic hinges may be formed. This would result in finding optimum places to reinforce the structure . According to the analysis , braces are thos e members. 2.8 Design of SMA braces For comparing the two structures which are SPD12 platform with and without SMA braces, super -elastic SMA braces are designed to provide the same yielding strength and the same axial stiffness as tubular steel braces. Therefore, cross section and length of the SMA elements (𝐴𝑆𝑀𝐴,𝐿𝑆𝑀𝐴) can be obtained [ 8]. To do so, the following relations are achieved: 𝐴𝑆𝑀𝐴=𝐹𝑦 𝜎𝑠𝐴𝑆=𝑓𝑦𝑠𝑡𝑒𝑒𝑙×𝐴𝑠𝑡𝑒𝑒𝑙 414=(355 𝑜𝑟 345 )𝐴𝑠𝑡𝑒𝑒𝑙 414=0.857 𝐴𝑠𝑡𝑒𝑒𝑙 0.833 𝐴𝑠𝑡𝑒𝑒𝑙 𝐿𝑆𝑀𝐴=𝐸𝑆𝑀𝐴×𝐴𝑆𝑀𝐴 𝐾𝑠𝑡𝑒𝑒𝑙=27579 ×𝐴𝑆𝑀𝐴 2×105×𝐴𝑠𝑡𝑒𝑒𝑙 𝐿𝑠𝑡𝑒𝑒𝑙⁄=0.118 𝐿𝑠𝑡𝑒𝑒𝑙 0.115 𝐿𝑠𝑡𝑒𝑒𝑙 As the SMA bars are made i n small diameter, they can not resist compression forces and can buckle simply, so SMA bars should be tensile elements. For modeling of the SMA braces due to the length and the cross section of needed SMAs, these braces are modeled with SMA which has the require d stiffness and is in c ompliance with force -displacement curve. The link elements which are defined in SAP2000 have independent configurations that the length and the cross section of the SMA is considered in its P - curve, so drawing with different length didn’t make any differ ence in modelling. For solving the problem of the SMA bars in compression forces, new connection of SMA to the steel braces is introduced which makes SMA elements be in tension although the brace is in compression. As a result, Symmetric P - curve (Fig. 5) is used to consider the compression part as same as the tension one for modeling the SMA elements. 2.9 Proposed connection between SMA and tubular braces One of the objectives of this article is utilizing the SMA behavior, especially having no residual strain, in offshore platforms. Due to not being capab le of restricting SMA bars under the compression forces, the SMA braces should design in such both tension and compression. Fig. 7 presents the proposed connection in SMA braces. This novel connection is inspired from the conducted research by Kari [ 31] who proposed a constitutive SMA braces in BRB frames . (a) (b) (c) (d) (e) (f) (g) (h) Fig. 7 Details of the proposed connection; (a) 3 -D model, (b) 2 -D model, (c) Section A -A, (d) Section B -B, (e) Section C -C, (f) Section D -D, (g) Section E -E, and (h) Free moving plate As shown in Fig. 7, this SMA brace consists of tubular steel and SMA elements. The SMAs are connected to the main tubular elements in such a way that the SMAs are under tension forces. For obtaining this purpose, some plates and two short tubular elements which have differe nt diameter are considered . First tubular element is connected to the left side of the main tubular brace and its right side is free to move, and second one is connected to the right side of the main tubular brace and its left side is free to move. The SMA bars are connected to the plates which are free to move in axial direction of the brace. When the brace is under tension, the two triangle plates push the moving plates apart from each other and the SMA bars will experience the tension. When the brace is under compression , the two short tubular elements push the moving plates from their free sides, so the SMA bars will be under tension again . 2.10 Non-linear time history analysis For time history analysis, the appropriate earthquake records of the location of the structure are better to be provided . The ground displacement, ground velocity, or ground acceleration are the forms of lateral loadings that earthquake records should be appl ied. Unfortunately, earthquake records from the considered region were not available to be used in this research. In this paper , earthquake acceleration records, which are provided by the University of Berkley database, used are El Centro/US, Kobe/Japan, a nd Tabas/Iran earthquakes to compare the effect of SMAs on the considered structure . The details of these ground motions can be seen in Table 6 and Fig. 8. To apply the selected accelerograms for the time history analyses, they are scaled to the maximum ac celeration of the region which is 0.35g with respect to the SeismoSignal software [ 32]. Each record is applied at the fixity level of the equivalent piles as a horizontal component. The earthquakes are applied in both directions (X and Y) separately and the results are obtained to compare these structures. Table 6 Details of the ground motions Earthquake Year Peak Ground Accelerating (g) Time step (s) Duration (s) El Centro 1940 0.291 0.01 53.71 Kobe 1995 0.309 0.01 31.99 Tabas 1978 0.968 0.02 32.98 (a) (b) (c) Fig. 8 Earthquake acceleration records; (a) ElCentro, (b) Kobe, and (c) Tabas 3. Results Pushover analysis and non -linear time history analysis are conducted on two main types of structure; SPD12 with tubular steel braces and SPD12 with SMA braces. The SPD12 with SMA braces is sorted by 4 kinds of structure; SPD12 with SMA braces in 3rd level, SPD12 with SMA braces in 1st level, SPD12 with SMA braces in 1st and 3rd levels, and SPD12 with SMA braces in all levels which are presented in Fig. 9. The reason of selecting 1st and 3rd level is due to the damage propagation in SPD12 under modal or cons tant pattern distribution pushover loading. For modal pattern distribution loading, damages are initiated from 3rd level, and for constant one, damages are initiated from 1st level. Thus, 1st and 3rd levels are vulnerable to be damaged. (a) (b) (c) (d) (e) Fig. 9 Types of SPD12 in modeling; (a) with tubular steel braces. (b) with SMA braces in 3rd level, (c) with SMA braces in 1st level, (d) with SMA braces in 1st and 3rd levels, and (e) with SMA braces in all levels 3.1. The effect of SMA braces on internal forces of the structure For assessing the internal forces in the platform and comparing the effect of the SMA braces, one brace of the jacket platform is modeled independently which is shown in Fig. 1 0. For assessing the SMA braces, three kinds o f elements are modeled; tubular steel, element with combination of tubular steel and SMA (SMA braces), and SMA element . These models are subjected to displacement loading and have the same stiffness. The maximum bearing forces are presented in Table 7. Fig. 1 0 Modeling of brace element Table 7 Maximum bearing forces (kN) of elements under displacement loading of 0.167m Modeling type Maximum bearing force Tubular steel 56160 SMA brace 9649 SMA in total length 10180 As shown in Table 7, the internal forces of the brace element will be reduced about 85% by considering the SMA bars. As a result, stress in the elements and the connections will be reduced which confirms the research studied by Shabakhty and Givkay [ 18], and utilizing SMA bars leads delay the structure collapse. The internal forces in SMA brace and SMA in total length are approximately the same which confirms the modeling of the whole platform with SMA in total length instead of SMA braces for simplifying the calculations. 3.2. The effect of SMA braces on the displacement of the deck level and base shear The time histories of displacement of the deck level subjected to the accelerograms of El Centro, Kobe, and Tabas are presented in Fig. 1 1 for the five types of SPD12 as mentioned before. There is no specific relation between these types , and the SMA braces don’t have more priority in reducing the displacements than steel braces. Fig. 1 1 shows that the displacements of the deck level will be reduced for the El Centro accelerogram and will be increased for Kobe and Tabas accelerograms in the most time. However, SMA braces play a prominent role that they reduced the residual displacement of the structure. The maximum values of the deck level di splacement which don’t have any specific trend, and residual displacement which will be reduced by utilizing SMA braces in the five types of SPD12 are compared in Table 8. (a-1) (a-2) -0.25-0.2-0.15-0.1-0.0500.050.10.150.20.25 0 10 20 30 40 50 60Displacement (m) Time (s)El Centro -X Without SMA With SMA-All levels With SMA-1st level With SMA-3rd level With SMA-1st & 3rd levels -0.2-0.15-0.1-0.0500.050.10.150.20.25 0 10 20 30 40 50 60Displacement (m) Time (s)El Centro -Y Without SMA With SMA-All levels With SMA-1st level With SMA-3rd level With SMA-1st & 3rd levels (b-1) (b-2) (c-1) -0.25-0.2-0.15-0.1-0.0500.050.10.150.2 0 10 20 30 40 50 60Displacement (m) Time (s)Kobe -X Without SMA With SMA-All levels With SMA-1st level With SMA-3rd level With SMA-1st & 3rd levels -0.3-0.2-0.100.10.20.30.4 0 10 20 30 40 50 60Displacement (m) Time (s)Kobe -Y Without SMA With SMA-All levels With SMA-1st level With SMA-3rd level With SMA-1st & 3rd levels -0.3-0.25-0.2-0.15-0.1-0.0500.050.10.150.20.25 0 10 20 30 40 50 60Displacement (m) Time (s)Tabas -X Without SMA With SMA-All levels With SMA-1st level With SMA-3rd level With SMA-1st & 3rd levels (c-2) Fig. 1 1 The time history of displacement of the deck level of five types of SPD12 under the earthquake records of (a) El Centro, (b) Kobe, and (c) Tabas in two directions . Table 8 The effect of SMA braces on the displacement and residual displacement of the deck level of SPD12 Earthquake Deck level’s maximum displacement (m) Deck level’s maximum residual displacement (m) Without SMA SMA in 1st level SMA in 3rd level SMA in 1st & 3rd levels SMA in all levels Without SMA SMA in 1st level SMA in 3rd level SMA in 1st & 3rd levels SMA in all levels El Centro -X 0.163 0.179 0.184 0.178 0.175 0.024 0.000 0.025 0.000 0.000 El Centro -Y 0.143 0.165 0.140 0.161 0.166 0.050 0.001 0.049 0.001 0.001 Kobe -X 0.176 0.138 0.178 0.142 0.145 0.018 0.001 0.019 0.001 0.001 Kobe -Y 0.303 0.257 0.297 0.249 0.258 0.048 0.000 0.049 0.000 0.000 Tabas -X 0.186 0.189 0.185 0.188 0.185 0.018 0.002 0.018 0.002 0.002 Tabas -Y 0.103 0.133 0.105 0.130 0.134 0.022 0.003 0.028 0.003 0.003 The base shear comparison of the five types of SPD12 platform models shows that there is no relation between base shear and utilizing SMA braces , just like displacement comparison results. However, SMA braces due to their characteristics will reduce the re sidual base shear which will reduce the element residual internal forces and lower the side effects o f fatigue in the structure. Fig. 12 shows the time history of the base shear for the five types of SPD12 platform subjected to the accelerograms of El Cent ro, Kobe, and Tabas earthquakes. -0.2-0.15-0.1-0.0500.050.10.150.2 0 10 20 30 40 50 60Displacement (m) Time (s)Tabas -Y Without SMA With SMA-All levels With SMA-1st level With SMA-3rd level With SMA-1st & 3rd levels (a-1) (a-2) (b-1) -10000-8000-6000-4000-20000200040006000800010000 0 10 20 30 40 50 60Base Shear (kN) Time (s)El Centro -X Without SMA With SMA-All levels With SMA-1st level With SMA-3rd level With SMA-1st & 3rd levels -15000-10000-50000500010000 0 10 20 30 40 50 60Base shear (kN) Time (s)El Centro -Y Without SMA With SMA-All levels With SMA-1st level With SMA-3rd level With SMA-1st & 3rd levels -8000-6000-4000-200002000400060008000 0 5 10 15 20 25 30 35 40 45Base shear (kN) Time (s)Kobe -X Without SMA With SMA-All levels With SMA-1st level With SMA-3rd level With SMA-1st & 3rd levels (b-2) (c-1) (c-2) Fig. 1 2 The time history of the five types of platform’s base shear under the earthquake records of (a) El Centro, (b) Kobe, and (c) Tabas in two directions . The rigidity of the structure doesn’t allow elements to experience the nonlinearity when they are subject ed to the earthquake records . So, most of the elements are linear , and SPD12 doesn’t have experience d a big displacement to be controlled by SMA bars. -20000-15000-10000-5000050001000015000 0 5 10 15 20 25 30 35 40 45Base shear (kN) Time (s)Kobe -Y Without SMA With SMA-All levels With SMA-1st level With SMA-3rd level With SMA-1st & 3rd levels -10000-8000-6000-4000-20000200040006000800010000 0 5 10 15 20 25 30 35 40 45 50Base shear (kN) Time (s)Tabas -X Without SMA With SMA-All levels With SMA-1st level With SMA-3rd level With SMA-1st & 3rd levels -10000-8000-6000-4000-200002000400060008000 0 5 10 15 20 25 30 35 40 45 50Base shear (kN) Time (s)Tabas -Y Without SMA With SMA-All levels With SMA-1st level With SMA-3rd level With SMA-1st & 3rd levels 3.3. The effect of SMA braces on pushover curve of the structure For obtaining the effects of SMA braces on offshore platforms, SPD12 is pushed by modal pattern loading for experiencing 2m displacement at the deck level of the platform. Pushover curves of five types of SPD12 in two directions are shown in Fig. 1 3. By ut ilizing SMA braces , the structure will be under a greater force as the base shear increases when the structure goes through the nonlinear part . Therefore, deck displacement of SPD12 will be decreased if it is reinforced by SMA braces. (a) (b) Fig. 1 3 Pushover curves of five types of SPD12; (a) X -direction, and (b) Y -direction 5. Conclusions This study proposed utilizing SMA bars in jacket -type offshore platforms and assessed it for further designation of platforms. Due to the characteristics of SMA bars which resist only tensional forces, a novel connection is introduced to use SMA bars, just under tens ional forces, in tubular braces . A seismic assessment of the platform is considered to obtain distribution of plastic hinges due to pushover analysis and optimization of using SMA bars in tubular braces was conducted . As a case study , an existing 4 -legged jacket -type platform SPD12 was assessed with FEMA -356. As the results show, SMA bars have a little effect on the SPD12 that just reducing residual displacements, and it seems that utilizing SMA bars isn’t an appropriate solution. However, The SPD12 is very rigid and 010000200003000040000500006000070000 0 0.5 1 1.5 2 2.5Base shear (kN) Deck level displacement (m)Without SMA With SMA in 1st and 3rd levels With SMA in 1st level With SMA in 3rd level With SMA in all levels 0100002000030000400005000060000700008000090000100000 0 0.5 1 1.5 2 2.5Base shear (kN) Deck level displacement (m)Without SMA With SMA in 1st and 3rd levels With SMA in 1st level With SMA in 3rd level With Sma in all Levels doesn’t experience the nonlinearity in its structure subject ed to considered accelerograms. So, for obtaining real effects of the SMA bars on structure, pushover analyses are conducted , and pushover curves of the five types of SPD12 are com pared. This research shows that: • For obtaining more effective offshore platform equipped with SMA braces, SMA braces have to be at least in first and third level of the structure to control the damage distribution and reduce the residual displacement. • SMA braces can reduce residual displacement and stress in the structure, so the lifetime of the structure will be increased. • Forces in e leme nts and connections will be reduced about 85% by SMA braces. Therefore, API recommendations for design of the offshore platform can be improved . • Reduction of deck level displacement and base shear can be obtained by SMA braces. • Higher offshore platforms equipped with SMA braces can be designed in deeper sea efficiently and financially. Declaration of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this arti cle.