A Performance Evaluation of Seismic Retrofit of Existing Greece Building

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C. Haran Pragalath This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3834368/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract A seismic retrofit entails modifying existing structures in order to improve the system's performance or to repair or strengthen its components to reach the desired performance. In order to arrive at an appropriate retrofitting scheme, the structure's vulnerability and a detailed seismic evaluation are essential, where seismic fragility curves are one of the tools for seismic evaluation. In this study, a 5-storey typical existing Greek building is selected which was designed according to Greek Code. The selected buildings are modelled for nonlinear analysis with and without shear walls. Seismic records are selected, scaled and modified according to Greek Response spectrum. Dynamic time-history analysis is performed. Inter-story drift is considered as damage parameter and fragility curves are developed for various performance levels. This holistic approach contributes to the broader understanding of seismic retrofitting methodologies and their applicability to existing structures, particularly those designed under specific regional codes such as the Greek Code. The result shows that there are significant improvements after retrofitting the building using shear walls. Fragility Curves Shear Wall Inter storey drift Retrofitting Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction The occurrence of earthquakes has become widespread throughout the world. Structures built to withstand loads like dead, live, wind, etc. may not necessarily be safe against earthquake loading. It is neither practical nor economically viable to design buildings so that they remain within elastic limits during earthquakes. Today, the demand for seismic assessment and the retrofitting of structures has grown due to a multitude of issues including design inadequacies, construction deficiency, and the aging of these structures. Retrofitting, in this context, refers to the process of modifying existing structures, such as buildings and bridges, to enhance their resistance to seismic events and other natural disasters. Earthquakes, being among the most hazardous of natural disasters for structures, necessitate meticulous attention, particularly in the structural design phase. The aging of structures is often responsible for diminishing their strength, primarily due to factors like seismic activity, soil instability, and the failure of structural elements like columns, beams, and slabs owing to design and construction deficiencies. Reinforced concrete (RC) buildings that were initially designed without considering seismic criteria and ductile detailing face the risk of severe damage during earthquake-induced ground motion. Strengthening existing buildings has proven to be a more cost-effective and practical solution for providing immediate shelter as opposed to replacing entire structures. Existing reinforced concrete buildings also faces the potential of inadequate seismic performance, primarily attributed to the periodic revisions of seismic standards and procedures within different regions. While some of these structures may exhibit satisfactory performance in potential future earthquakes, others lack the capability to endure substantial damage and could ultimately collapse due to their insufficient seismic performance. In these circumstances, there is a significant need to carry out an adequate performance assessment of RC buildings and to investigate possible retrofitting schemes prior to future seismic events. Hence, the need for strengthening options is paramount for ensuring safety. Lazaris [1], studied a four-storey concrete building in Athens, constructed in 1970, was evaluated for seismic resilience using Eurocode 8 [2] and Seismostruct [3] software, the seismic assessment identified torsional sensitivity and shear failures. Retrofitting methods, including X-shaped steel braces and fiber-reinforced plastic jacketing, were sequentially applied, resolving torsional sensitivity, shear, and compressive failures. Alashkar et al. [4] investigated the seismic performance of a nine-story RC building in zone III, focusing on retrofitting with shear walls and concentrated steel bracing. The comprehensive analysis compared various steel bracing systems in combination with concrete shear walls, evaluating performance based on criteria such as story drift, lateral displacements, bending moments, and base shear. Haikal and Muca [5] investigated the retrofitting of a seven-story building in Stockholm, constructed with prefabricated concrete and steel elements. Utilizing Eurocode 8 and previous studies, seismic analysis identified critical areas with abnormal behavior. Various retrofitting approaches, including steel bracing and prefabricated reinforced concrete walls (shear walls), were applied, highlighting a combined strategy as the most effective in enhancing the building's strength and overall structural performance. Sahin [6] focuses on earthquake-resistant design, seismic evaluation, and retrofitting strategies for a steel moment-frame building. Emphasizing the necessity of seismic upgrading, it outlines processes to assess structural vulnerabilities and proposes retrofitting methods, particularly concentrically braced frames. The study underscores the importance of performance-based design, using computer software modeling and analyses to enhance seismic resistance and prevent structural collapse under design loads. D’Amato [7] investigated the seismic retrofitting of an existing RC building from the '90s, initially designed only for vertical loads, which was achieved through the application of seismic isolation. This involved adding seismic devices at the base, including a bracing system with two elastic steel frames to stiffen the superstructure and minimize higher vibration modes' effects. Dumaru et al. [8] made a study that evaluates the seismic performance of existing non- and pre-engineered buildings, particularly those damaged during the 2015 Gorkha earthquake. The retrofitted measures, primarily involving steel bracing, significantly enhance the stiffness, strength, and ductility of the structures, as evidenced by pushover curves. The retrofitting reduces the probability of collapse, with steel bracing identified as a particularly effective strategy in improving the seismic performance of the analyzed buildings. Tzavidis et al. [9] made a study assessing the performance of an 8-story reinforced concrete building retrofitted with a new precast insulated steel and concrete composite sandwich wall. The retrofitting includes inverted-V steel bracings. Through inelastic dynamic analyses with earthquake scenarios, the seismic response is evaluated, considering both construction cost and earthquake losses. The study aims to determine the most efficient retrofit method by comparing the performance of each method with the original building. Suresh Kannan [10] made a research analysing the seismic performance of a (G + 8) building by modeling it as a bare frame, a frame with shear wall, and a frame with X bracing, with variations in the placement of a soft storey. Using Staad Pro-V8i software for static analysis in seismic zones IV and V, the study assesses parameters such as displacement, storey drift, and base shear. The results indicate that shear walls significantly reduce lateral displacement and storey drift, recommending their use in seismic hazard zones, while steel bracing is recommended for low seismic zones based on the analysis results. Natraj et al. [11] focuses on the analytical investigation of a multi-storey building in seismic zone III. Adopting externally bonded FRP strengthening techniques, the study evaluates the seismic performance by analyzing the building both with and without a lateral resisting system (shear wall). Retrofitting involves wrapping deficient beams and columns with Carbon Fiber Reinforced Polymer (CFRP sheet), aiming to enhance the structural elements' performance. Shendkar et al. [12] analysed a three-dimensional 4-story RC building using various infill wall configurations for seismic effects. Different models, including infilled frames and a bare frame, were subjected to static adaptive pushover analysis. The study assessed the impact of infill wall compressive strengths on seismic design factors, revealing decreased response reduction factors for infilled frames with lower compressive strengths and highlighting a deviation in deflection factors from NEHRP provisions. According to the KANEPE [13], Greek Code structures should be designed so that they can withstand minor earthquakes occurring frequently and without damage; the structure should be able to resist moderate earthquakes without significant structural damage, despite some non-structural damage occurring, and the structure should be able to withstand major earthquakes without collapsing. To safely withstand the significant lateral forces that are applied to structures during frequent earthquakes, structures must have appropriate earthquake resistant features. Commonly, buildings are constructed to safely support their own weights. Low lateral loads from wind are ineffective against strong lateral forces from even a moderate-sized earthquake. These lateral forces have the potential to cause a structure to experience critical stresses, undesirable vibrations, and lateral sway—all of which could cause discomfort for the occupants. Strengthening the structure can be used as an effort to prevent collapse. There are a variety of retrofitting techniques that can help reduce lateral displacement. Reinforced concrete shear walls have been used as most effective solution to provide resistance and stiffening to the buildings against the lateral loads imposed by the earthquakes and wind. Moreover, these walls also provide sufficient ductility and lateral control drift in order to minimize the strong lateral load effect especially during earthquake. The use steel bracing is also an effective solution for retrofitting and strengthening of seismically inadequate reinforced concrete frame structure. It is highly efficient and economical method to increase the lateral resistant capacity of the building by increasing its lateral stiffness. High in plane stiffness and strength allow shear walls (SW) to support gravity loads while simultaneously resisting heavy horizontal loads. Present work is to estimate the building seismic performance using fragility curves for the building designed according Greek old code [13] and to improve the building performance using shear walls. 2. Methodology Fragility function shows the likelihood that a chosen Engineering Demand Parameter ( EDP ) will be exceeded for a chosen structural limit state ( LS ) for a particular ground motion intensity measure ( IM ). Fragility curves are cumulative probability distributions that represents the probability, as a function of a given demand, that a component or system will reach a specific damage state or a more severe one. The following equation can be used to express the seismic fragility, FR(x) , in closed form. $$P \left(D \ge \left.C \right| IM\right)=1-\varnothing \left(\frac{ln\frac{{S}_{C}}{{S}_{D}}}{\sqrt{{{\beta }^{2}}_{\left(D|IM\right)}}+{{\beta }_{c}}^{2}+{{\beta }_{M}}^{2}}\right)$$ (1) where, SC and SD are the selected limit state and the median of the demand ( LS ), respectively, and D is the drift demand. C is the drift capacity at the chosen limit state. Dispersions in the intensity measure, capacities, and modeling are denoted as βd/IM, βc and \({\beta }_{M}\) , respectively. Using the above equation fragility curve can be derived for various limit stat es. The equation below, where \(a{IM}^{b}\) stands in for the mean inter-storey drift, can be used to calculate the dispersion, D/IM , of inter-storey drifts ( \({d}_{i}\) ) from the time history analysis. In general, probabilistic seismic demand models ( PSDMs ) describe the seismic demand ( SD ), particularly for the Nonlinear Time History Analysis ( NTHA ), and provide an appropriate intensity measure ( IM ). It was proposed by Cornell et al. [14], the estimate of the median demand, EDP ( SD ), can be generalized by a power model as given below. $$EDP=a{\left(IM\right)}^{b} \left(2\right)$$ where, a and b are the regression coefficients of the PSDM . Eq. 1 can be rewritten for system fragilities as follows: $$P \left(D \ge \left.C \right| IM\right)=1-\varnothing \left(\frac{\text{ln}\left({S}_{c}\right)-\text{ln}\left(a\bullet {IM}^{b}\right)}{\sqrt{{{\beta }^{2}}_{\left(D|IM\right)}+{{\beta }_{c}}^{2}+{{\beta }_{M}}^{2}}}\right) \left(3\right)$$ The dispersion, \({\beta }_{\left(D|IM\right)}\) , of inter-storey drifts ( \({d}_{i}\) ) from the time history analysis can be calculated using the following equation where \({aIM}^{b}\) represents the mean inter-storey drift. [15] $${ \beta }_{\left(D|IM\right)}\cong \sqrt{\frac{\sum {[\text{ln}\left({d}_{1}\right)-\text{ln}\left(a{IM}^{b}\right)]}^{2}}{N-2}} \left(4\right)$$ Values for \({\beta }_{C}\) under typical conditions are recommended by ATC 58 [16]. In the current study, \({\beta }_{C}\) is taken into account to be 0.25, indicating that the building design is finished to a level typical of design development and that limited quality is expected in construction quality assurance and inspection. According to ATC 58, inaccurate component modeling, damping, and mass assumptions lead to modeling uncertainty ( \({\beta }_{M}\) ). This uncertainty has been correlated to the nonlinear analysis model's completeness and accuracy ( \({\beta }_{q}\) ) as well as the dispersion of building definition and construction quality assurance ( \({\beta }_{C}\) ) for the purpose of estimating, \({\beta }_{M}\) . The total modelling dispersion can be estimated as follows: $${ \beta }_{m}=\sqrt{{{\beta }_{c}}^{2}+{{\beta }_{q}}^{2}} \left(5\right)$$ In this study, \({\beta }_{q}\) is considered to be 0.25, indicating that each component's numerical model is reliable across the expected range of displacement or deformation response. Even though some failure modes are simulated indirectly, the degradation of strength and stiffness is fairly well represented. The majority of the building's structural and non-structural elements that significantly increase stiffness or strength are included in the mathematical model. 3. Case Study Building Data A five-storey reinforced concrete moment resting frame building of symmetrical rectangular plan configuration typical existing Greek building that has been used for checks of KANEPE, the Greek Code with a medium type of soil conditions is considered in this study. Selected building plan and elevation are shown in Figs. 1 & 2, respectively. The total height of the building is 15m with ground and storey height of 3m respectively Table I and II. Table I. Column sections and reinforcement details for the existing 5-storey building. Storey number Position Width (mm) Depth (mm) Main Reinforcement Details (uniformly distributed) G A 400 400 8@18 mm B 300 450 8@16mm C 350 450 8@18mm D 500 500 12@20mm 1st – 4th A 350 350 4@20mm B 300 400 8@14mm C 500 500 12@20mm Table II. Shear wall section and reinforcement details Width (m) Thickness (mm) Reinforcement Details (uniformly distributed) 3 300 38@16mm 4. Selection of earthquake ground motion Seismic load uncertainties are considered in this study by using number of seismic records. Only Far field earthquakes are chosen for this study considering the building is located at least 10 km away from faults (Ravichandaran and Klinger, [17]). Sarkar et. al [18] developed seismic fragility curves using natural and synthetic ground motions and concluded that, it is conservative approach to use synthetic ground motions. The 22 pairs of far-field seismic records given in FEMA P695 [19] are chosen for the analysis and they are modified to match the Greek Design response spectrum. Figure 3 . Shows Greek Design response spectrum chosen with the spectrum type as 1 and the group type as C with the importance Class III and the damping value is 5%. Selected earthquakes are modified using Seismomatch [20] software and modified seismic records response spectrum are shown in the Fig. 4 . Further these records are scaled to 0.1 PGA to 1 PGA linearly. 5. Nonlinear Modelling of elements A series of nonlinear time history analyses (N-LTH) of RC frames have been performed. Seismostruct software is used for all analyses. Force-based nonlinear beam column element that consider the spread of plasticity along the element is used for modelling the beams, columns and Shear walls. Formulation of the fiber-based element can be seen in Lee and Mosalam [21]. The Concrete is modelled according to Mander et. al [22]. and reinforcements are modelled according to Menegotto and Pinto [23]. Similar kind of non-linear material modelling are found in [24], [25].Rayleigh damping is used in the present study, Eigenvalue analysis is carried out for both bare frame building and with retrofitted shear walls. Calculation of Rayleigh damping is shown in Table III. Table III. Damping used for different frames Frame type Period, \(s\) Bare Frame 0.645 0.214 Strengthened frame (Shear wall) 0.365 0.085 6. Probabilistic seismic demand models and Fragility curves In the context of the five-storey retrofitted building using shear walls, a comprehensive analysis has been undertaken to establish (PSDMs) for both the original bare frame and the retrofitted structure. The analysis encompasses two distinct models, each representing different configurations of the selected building. The (NTHA) has been applied to the models, with particular focus on monitoring Inter-Storey Drifts (ISD) at each level of the building. Subsequently, the maximum ISD at each storey is plotted against the corresponding (PGA) in a logarithmic plot. Through rigorous regression analysis, optimal curves are derived, characterizing the PSDM for each storey level are developed (Figs. 5 & 6 ). The coefficients denoted as 'a' and 'b' in the power law model (refer Eq. 2) are derived through the optimization of a best-fit curve. Utilizing the dataset comprising (ISD) and (PGA) values, the dispersions in the Intensity Measure ( βEDP/IM ) are computed. This calculation, outlined in Eq. 4, is performed individually for each storey across all frames. Damage Limitation, Significant Damage, and Collapse Prevention are three crucial performance levels that are estimated to be 1% (DL), 2% (SD), and 4% (CP) in the current study. Fragility curves for various performance levels, including Damage Limitation (DL), Significant Damage (DM), and Collapse prevention (CP), are developed after PSDM models using Eq. 3 and dispersions (βD|PGA, βc, and βm) for all the models are computed as shown in Fig. 7. In order to understand the behavior of bare frame in comparison with a retrofitted shear wall building the corresponding fragility curves are compared. In a comprehensive comparison of the fragility curves for Damage Limitation (DL), Significant Damage (DM), and Collapse Prevention (CP) between the bare frame and retrofitted building models, distinct trends and improvements are seen. For the Damage Limitation aspect at a PGA of 0.7, the bare frame model exhibits a vulnerability of 94%, whereas the shear wall retrofitted model demonstrates a significant enhancement, reducing the vulnerability to 62%. This stark reduction underscores the effectiveness of shear wall retrofitting in minimizing damage under moderate seismic events. Similarly, in the context of Significant Damage, the bare frame model registers an 80% vulnerability, while the shear wall retrofitting substantially mitigates the risk, yielding a vulnerability of only 32%. The most substantial disparity is observed in Collapse Prevention, where the bare frame model displays a vulnerability of 54%, while the shear wall retrofitted model impressively reduces this vulnerability to a mere 10%. These values collectively illustrate the considerable resilience and structural integrity conferred by shear wall retrofitting methods for buildings designed according to old codes., emphasizing its pivotal role in enhancing the overall seismic performance and risk mitigation capabilities of the five-storey building. 7. Conclusion Structures designed without considering seismic criteria and lacking ductile detailing face significant damage when subjected to earthquake ground motion. The imperative for retrofitting or strengthening such earthquake-prone or damaged buildings has intensified, particularly in the result of recent seismic events. This study focuses on the seismic analysis of a five-storey building using Seismostruct software, with the incorporation of shear walls identified as a highly efficient strategy for enhancing seismic resilience. Structural retrofitting at the system level becomes imperative when the entire lateral load-resisting system is deemed deficient. Specifically, shear wall strengthening techniques are used to fortify failed beams and columns. The key findings of this investigation are as follows: The addition of new concrete shear walls emerges as a widely adopted and proven technique, effectively controlling global lateral drifts and minimizing damages in frame structures. The strategic placement of shear walls within the frame system emerges as a critical consideration, significantly reducing lateral forces. Notably, the introduction of shear walls results in a substantial reduction of up to 48% in the maximum storey drift of the building. This underscores the efficacy of shear wall retrofitting in enhancing structural stability and minimizing seismic-induced deformations. Declarations Author Contribution M.S. Yousif did nonlinear modelling for selected buildings, performed dynamic time history analysis and developed Manuscript. Wrote the main manuscript and prepared figures with tables and all necessary information to create the script. D.C. Haran explored the methods to develop fragility curves, and developed fragility curves based on dynamic time history analyses. And provided guidance throughout the script contributing to the overall script's coherence and conceptual framework. References Lazaris, A. Seismic evaluation and retrofitting of an existing building in Athens using pushover analysis, 2019. British Standards Institution. Eurocode 8: Design of structures for earthquake resistance. London, BS EN 1998. 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Siesmosoft ltd, SeismoMatch (Version 2022 Release-1 Build-50) [Computer Software]. https://seismosoft/products/ Seismomatch (2022) Lee, T. H. and Mosalam, K. M. Probabilistic fiber element modeling of reinforced concrete structures, Computers and Structures , 82(27):2285-2299, 2004 Mander J.B., Priestley M.J.N., Park R. "Theoretical stress-strain model for confined concrete," Journal of Structural Engineering , Vol. 114, No. 8, pp. 1804-182, 1988. Menegotto M., Pinto P.E. "Method of analysis for cyclically loaded R.C. plane frames including changes in geometry and non-elastic behaviour of elements under combined normal force and bending," Symposium on the Resistance and Ultimate Deformability of Structures Acted on by Well Defined Repeated Loads , International Association for Bridge and Structural Engineering, Zurich, Switzerland, pp. 15-22, 1973. Karthick, L.A. , Sriraman, M. , Durai, T.N.P., Pragalath, D.H., Fragility curves by SAC FEMA and ANN Method, International Journal of Civil Engineering and Technology, Vol. 8(7), pp. 1103–1110, 2017. Haran Pragalath, D.C., Karthick Hari, K.B., Rana Pratap, S.,Sriraman, M., Madhura, S., Selection of infill wall material modelling for seismic excitations, International Journal of Applied Engineering Research, Vol. 10(17), pp. 37225–37234, 2015. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3834368","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":265243773,"identity":"12073005-3875-4806-8db7-eba2db23b7d0","order_by":0,"name":"Mohanad Salsal Yousif","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+0lEQVRIiWNgGAWjYFACHhDBDMINDAwFNkAGY+MBIrUwArUYpIEZJGk5DBbDq0W3vffg54Iaawb59oPNH34YnLdb234YaEuNTTQuLWZnziVLzziWzmBwJrFNssfgdvK2M4lALcfSchtwabmRYyDNw3aYwYAhsY2BB6jF7ABQC2PDYXxajH/z/DvMIN//sPnjH4NzyWbnHxLUYibN2wb09Y3EBmkegwN2ZjcI2XLmjJk1b186j8GNh23SMgbJCWY3gLYk4PPL8R7j2zzfrOXk+5MPf3xTYWdvdj794YMPNTY4tcAAD4yRCFaZQEA5CrAnRfEoGAWjYBSMDAAAx5Nih0dcTFwAAAAASUVORK5CYII=","orcid":"","institution":"British Applied College","correspondingAuthor":true,"prefix":"","firstName":"Mohanad","middleName":"Salsal","lastName":"Yousif","suffix":""},{"id":265243774,"identity":"6352c31b-a0e2-4ece-ab06-56d63bfba85c","order_by":1,"name":"D. C. Haran Pragalath","email":"","orcid":"","institution":"British Applied College","correspondingAuthor":false,"prefix":"","firstName":"D.","middleName":"C. Haran","lastName":"Pragalath","suffix":""}],"badges":[],"createdAt":"2024-01-04 11:02:22","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3834368/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3834368/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":49324782,"identity":"1368f44d-452b-41ba-bc2c-eaa0614d180a","added_by":"auto","created_at":"2024-01-08 17:20:39","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":17204,"visible":true,"origin":"","legend":"\u003cp\u003eBuilding plan view\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-3834368/v1/e36cc4ab35a692bec5134817.png"},{"id":49324783,"identity":"9d84fad7-6268-4517-a654-209006b1ccd1","added_by":"auto","created_at":"2024-01-08 17:20:39","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":16308,"visible":true,"origin":"","legend":"\u003cp\u003eBuilding Side Elevation\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-3834368/v1/3c61e28a0a388907ed8611c2.png"},{"id":49324784,"identity":"386e07a6-8287-4c8a-9cec-e8f380d433b7","added_by":"auto","created_at":"2024-01-08 17:20:39","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":20176,"visible":true,"origin":"","legend":"\u003cp\u003eGreek Design response spectrum\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-3834368/v1/00cf09fe4fedd68861bc6adf.png"},{"id":49324786,"identity":"91a6d08b-f383-4478-abd8-8967307f42af","added_by":"auto","created_at":"2024-01-08 17:20:39","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":100531,"visible":true,"origin":"","legend":"\u003cp\u003eSelected ground motion response spectrum with Greek design spectrum\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-3834368/v1/ab61e9d6f351e827fd32fb3d.png"},{"id":49324785,"identity":"140c004c-61cb-43be-9d24-934d6af6497e","added_by":"auto","created_at":"2024-01-08 17:20:39","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":51796,"visible":true,"origin":"","legend":"\u003cp\u003ePSDM Model of the bare frame building.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-3834368/v1/226d4cff931546393a1e933f.png"},{"id":49325651,"identity":"a2f5bc22-741e-4660-aad5-02f7a81eebc7","added_by":"auto","created_at":"2024-01-08 17:28:39","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":62221,"visible":true,"origin":"","legend":"\u003cp\u003ePSDM Model of Shear walls building.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-3834368/v1/d06f17b5e646359bf9be4457.png"},{"id":49324788,"identity":"c076a62e-5dce-418a-91ec-1d063689d6c0","added_by":"auto","created_at":"2024-01-08 17:20:39","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":60949,"visible":true,"origin":"","legend":"\u003cp\u003eFragility curves for different Performance Levels\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-3834368/v1/4bd86c3ca872a556cca5cf65.png"},{"id":49671065,"identity":"9bc6caf3-c93e-4b9b-ae2f-a40be7b8bfc6","added_by":"auto","created_at":"2024-01-16 08:52:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":767221,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3834368/v1/f1710861-786f-479a-abe4-343d053138eb.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"A Performance Evaluation of Seismic Retrofit of Existing Greece Building","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe occurrence of earthquakes has become widespread throughout the world. Structures built to withstand loads like dead, live, wind, etc. may not necessarily be safe against earthquake loading. It is neither practical nor economically viable to design buildings so that they remain within elastic limits during earthquakes. Today, the demand for seismic assessment and the retrofitting of structures has grown due to a multitude of issues including design inadequacies, construction deficiency, and the aging of these structures. Retrofitting, in this context, refers to the process of modifying existing structures, such as buildings and bridges, to enhance their resistance to seismic events and other natural disasters. Earthquakes, being among the most hazardous of natural disasters for structures, necessitate meticulous attention, particularly in the structural design phase. The aging of structures is often responsible for diminishing their strength, primarily due to factors like seismic activity, soil instability, and the failure of structural elements like columns, beams, and slabs owing to design and construction deficiencies. Reinforced concrete (RC) buildings that were initially designed without considering seismic criteria and ductile detailing face the risk of severe damage during earthquake-induced ground motion. Strengthening existing buildings has proven to be a more cost-effective and practical solution for providing immediate shelter as opposed to replacing entire structures. Existing reinforced concrete buildings also faces the potential of inadequate seismic performance, primarily attributed to the periodic revisions of seismic standards and procedures within different regions. While some of these structures may exhibit satisfactory performance in potential future earthquakes, others lack the capability to endure substantial damage and could ultimately collapse due to their insufficient seismic performance. In these circumstances, there is a significant need to carry out an adequate performance assessment of RC buildings and to investigate possible retrofitting schemes prior to future seismic events. Hence, the need for strengthening options is paramount for ensuring safety. Lazaris [1], studied a four-storey concrete building in Athens, constructed in 1970, was evaluated for seismic resilience using Eurocode 8 [2] and Seismostruct [3] software, the seismic assessment identified torsional sensitivity and shear failures. Retrofitting methods, including X-shaped steel braces and fiber-reinforced plastic jacketing, were sequentially applied, resolving torsional sensitivity, shear, and compressive failures. Alashkar et al. [4] investigated the seismic performance of a nine-story RC building in zone III, focusing on retrofitting with shear walls and concentrated steel bracing. The comprehensive analysis compared various steel bracing systems in combination with concrete shear walls, evaluating performance based on criteria such as story drift, lateral displacements, bending moments, and base shear. Haikal and Muca [5] investigated the retrofitting of a seven-story building in Stockholm, constructed with prefabricated concrete and steel elements. Utilizing Eurocode 8 and previous studies, seismic analysis identified critical areas with abnormal behavior. Various retrofitting approaches, including steel bracing and prefabricated reinforced concrete walls (shear walls), were applied, highlighting a combined strategy as the most effective in enhancing the building's strength and overall structural performance. Sahin [6] focuses on earthquake-resistant design, seismic evaluation, and retrofitting strategies for a steel moment-frame building. Emphasizing the necessity of seismic upgrading, it outlines processes to assess structural vulnerabilities and proposes retrofitting methods, particularly concentrically braced frames. The study underscores the importance of performance-based design, using computer software modeling and analyses to enhance seismic resistance and prevent structural collapse under design loads. D\u0026rsquo;Amato [7] investigated the seismic retrofitting of an existing RC building from the '90s, initially designed only for vertical loads, which was achieved through the application of seismic isolation. This involved adding seismic devices at the base, including a bracing system with two elastic steel frames to stiffen the superstructure and minimize higher vibration modes' effects. Dumaru et al. [8] made a study that evaluates the seismic performance of existing non- and pre-engineered buildings, particularly those damaged during the 2015 Gorkha earthquake. The retrofitted measures, primarily involving steel bracing, significantly enhance the stiffness, strength, and ductility of the structures, as evidenced by pushover curves. The retrofitting reduces the probability of collapse, with steel bracing identified as a particularly effective strategy in improving the seismic performance of the analyzed buildings. Tzavidis et al. [9] made a study assessing the performance of an 8-story reinforced concrete building retrofitted with a new precast insulated steel and concrete composite sandwich wall. The retrofitting includes inverted-V steel bracings. Through inelastic dynamic analyses with earthquake scenarios, the seismic response is evaluated, considering both construction cost and earthquake losses. The study aims to determine the most efficient retrofit method by comparing the performance of each method with the original building. Suresh Kannan [10] made a research analysing the seismic performance of a (G\u0026thinsp;+\u0026thinsp;8) building by modeling it as a bare frame, a frame with shear wall, and a frame with X bracing, with variations in the placement of a soft storey. Using Staad Pro-V8i software for static analysis in seismic zones IV and V, the study assesses parameters such as displacement, storey drift, and base shear. The results indicate that shear walls significantly reduce lateral displacement and storey drift, recommending their use in seismic hazard zones, while steel bracing is recommended for low seismic zones based on the analysis results. Natraj et al. [11] focuses on the analytical investigation of a multi-storey building in seismic zone III. Adopting externally bonded FRP strengthening techniques, the study evaluates the seismic performance by analyzing the building both with and without a lateral resisting system (shear wall). Retrofitting involves wrapping deficient beams and columns with Carbon Fiber Reinforced Polymer (CFRP sheet), aiming to enhance the structural elements' performance. Shendkar et al. [12] analysed a three-dimensional 4-story RC building using various infill wall configurations for seismic effects. Different models, including infilled frames and a bare frame, were subjected to static adaptive pushover analysis. The study assessed the impact of infill wall compressive strengths on seismic design factors, revealing decreased response reduction factors for infilled frames with lower compressive strengths and highlighting a deviation in deflection factors from NEHRP provisions.\u003c/p\u003e \u003cp\u003eAccording to the KANEPE [13], Greek Code structures should be designed so that they can withstand minor earthquakes occurring frequently and without damage; the structure should be able to resist moderate earthquakes without significant structural damage, despite some non-structural damage occurring, and the structure should be able to withstand major earthquakes without collapsing. To safely withstand the significant lateral forces that are applied to structures during frequent earthquakes, structures must have appropriate earthquake resistant features. Commonly, buildings are constructed to safely support their own weights. Low lateral loads from wind are ineffective against strong lateral forces from even a moderate-sized earthquake. These lateral forces have the potential to cause a structure to experience critical stresses, undesirable vibrations, and lateral sway\u0026mdash;all of which could cause discomfort for the occupants.\u003c/p\u003e \u003cp\u003eStrengthening the structure can be used as an effort to prevent collapse. There are a variety of retrofitting techniques that can help reduce lateral displacement. Reinforced concrete shear walls have been used as most effective solution to provide resistance and stiffening to the buildings against the lateral loads imposed by the earthquakes and wind. Moreover, these walls also provide sufficient ductility and lateral control drift in order to minimize the strong lateral load effect especially during earthquake. The use steel bracing is also an effective solution for retrofitting and strengthening of seismically inadequate reinforced concrete frame structure. It is highly efficient and economical method to increase the lateral resistant capacity of the building by increasing its lateral stiffness. High in plane stiffness and strength allow shear walls (SW) to support gravity loads while simultaneously resisting heavy horizontal loads. Present work is to estimate the building seismic performance using fragility curves for the building designed according Greek old code [13] and to improve the building performance using shear walls.\u003c/p\u003e"},{"header":"2. Methodology","content":"\u003cp\u003eFragility function shows the likelihood that a chosen Engineering Demand Parameter (\u003cem\u003eEDP\u003c/em\u003e) will be exceeded for a chosen structural limit state (\u003cem\u003eLS\u003c/em\u003e) for a particular ground motion intensity measure (\u003cem\u003eIM\u003c/em\u003e). Fragility curves are cumulative probability distributions that represents the probability, as a function of a given demand, that a component or system will reach a specific damage state or a more severe one. The following equation can be used to express the seismic fragility, \u003cem\u003eFR(x)\u003c/em\u003e, in closed form.\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$P \\left(D \\ge \\left.C \\right| IM\\right)=1-\\varnothing \\left(\\frac{ln\\frac{{S}_{C}}{{S}_{D}}}{\\sqrt{{{\\beta }^{2}}_{\\left(D|IM\\right)}}+{{\\beta }_{c}}^{2}+{{\\beta }_{M}}^{2}}\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e\u003cp\u003ewhere, \u003cem\u003eSC\u003c/em\u003e and \u003cem\u003eSD\u003c/em\u003e are the selected limit state and the median of the demand (\u003cem\u003eLS\u003c/em\u003e), respectively, and \u003cem\u003eD\u003c/em\u003e is the drift demand. \u003cem\u003eC\u003c/em\u003e is the drift capacity at the chosen limit state. Dispersions in the intensity measure, capacities, and modeling are denoted as \u003cem\u003eβd/IM, βc\u003c/em\u003e and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\beta }_{M}\\)\u003c/span\u003e\u003c/span\u003e, respectively. Using the above equation fragility curve can be derived for various limit stat es. The equation below, where \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(a{IM}^{b}\\)\u003c/span\u003e\u003c/span\u003estands in for the mean inter-storey drift, can be used to calculate the dispersion, \u003cem\u003eD/IM\u003c/em\u003e, of inter-storey drifts (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({d}_{i}\\)\u003c/span\u003e\u003c/span\u003e) from the time history analysis.\u003c/p\u003e \u003cp\u003eIn general, probabilistic seismic demand models (\u003cem\u003ePSDMs\u003c/em\u003e) describe the seismic demand (\u003cem\u003eSD\u003c/em\u003e), particularly for the Nonlinear Time History Analysis (\u003cem\u003eNTHA\u003c/em\u003e), and provide an appropriate intensity measure (\u003cem\u003eIM\u003c/em\u003e). It was proposed by Cornell et al. [14], the estimate of the median demand, \u003cem\u003eEDP\u003c/em\u003e (\u003cem\u003eSD\u003c/em\u003e), can be generalized by a power model as given below.\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$EDP=a{\\left(IM\\right)}^{b} \\left(2\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere, a and b are the regression coefficients of the \u003cem\u003ePSDM\u003c/em\u003e. Eq.\u0026nbsp;1 can be rewritten for system fragilities as follows:\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e\n$$P \\left(D \\ge \\left.C \\right| IM\\right)=1-\\varnothing \\left(\\frac{\\text{ln}\\left({S}_{c}\\right)-\\text{ln}\\left(a\\bullet {IM}^{b}\\right)}{\\sqrt{{{\\beta }^{2}}_{\\left(D|IM\\right)}+{{\\beta }_{c}}^{2}+{{\\beta }_{M}}^{2}}}\\right) \\left(3\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThe dispersion, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\beta }_{\\left(D|IM\\right)}\\)\u003c/span\u003e\u003c/span\u003e, of inter-storey drifts (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({d}_{i}\\)\u003c/span\u003e\u003c/span\u003e) from the time history analysis can be calculated using the following equation where \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({aIM}^{b}\\)\u003c/span\u003e\u003c/span\u003e represents the mean inter-storey drift. [15]\u003cdiv id=\"Equd\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equd\" name=\"EquationSource\"\u003e\n$${ \\beta }_{\\left(D|IM\\right)}\\cong \\sqrt{\\frac{\\sum {[\\text{ln}\\left({d}_{1}\\right)-\\text{ln}\\left(a{IM}^{b}\\right)]}^{2}}{N-2}} \\left(4\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eValues for \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\beta }_{C}\\)\u003c/span\u003e\u003c/span\u003e under typical conditions are recommended by ATC 58 [16]. In the current study, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\beta }_{C}\\)\u003c/span\u003e\u003c/span\u003e is taken into account to be 0.25, indicating that the building design is finished to a level typical of design development and that limited quality is expected in construction quality assurance and inspection. According to ATC 58, inaccurate component modeling, damping, and mass assumptions lead to modeling uncertainty (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\beta }_{M}\\)\u003c/span\u003e\u003c/span\u003e ). This uncertainty has been correlated to the nonlinear analysis model's completeness and accuracy (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\beta }_{q}\\)\u003c/span\u003e\u003c/span\u003e) as well as the dispersion of building definition and construction quality assurance (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\beta }_{C}\\)\u003c/span\u003e\u003c/span\u003e) for the purpose of estimating, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\beta }_{M}\\)\u003c/span\u003e\u003c/span\u003e. The total modelling dispersion can be estimated as follows:\u003cdiv id=\"Eque\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Eque\" name=\"EquationSource\"\u003e\n$${ \\beta }_{m}=\\sqrt{{{\\beta }_{c}}^{2}+{{\\beta }_{q}}^{2}} \\left(5\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eIn this study, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\beta }_{q}\\)\u003c/span\u003e\u003c/span\u003e is considered to be 0.25, indicating that each component's numerical model is reliable across the expected range of displacement or deformation response. Even though some failure modes are simulated indirectly, the degradation of strength and stiffness is fairly well represented. The majority of the building's structural and non-structural elements that significantly increase stiffness or strength are included in the mathematical model.\u003c/p\u003e"},{"header":"3. Case Study Building Data","content":"\u003cp\u003eA five-storey reinforced concrete moment resting frame building of symmetrical rectangular plan configuration typical existing Greek building that has been used for checks of KANEPE, the Greek Code with a medium type of soil conditions is considered in this study. Selected building plan and elevation are shown in Figs.\u0026nbsp;1 \u0026amp; 2, respectively. The total height of the building is 15m with ground and storey height of 3m respectively Table I and II.\u003c/p\u003e \u003cp\u003eTable I. Column sections and reinforcement details for the existing 5-storey building.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabb\" border=\"1\"\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStorey number\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePosition\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWidth (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDepth (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMain Reinforcement Details (uniformly distributed)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eG\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8@18 mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e450\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8@16mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e350\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e450\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8@18mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12@20mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e1st \u0026ndash; 4th\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e350\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e350\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4@20mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8@14mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12@20mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \n\u003c/br\u003e\n\u003cp\u003eTable II. Shear wall section and reinforcement details\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\u003ctable id=\"Tabc\" border=\"1\"\u003e\n \u003ccolgroup cols=\"4\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWidth (m)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eThickness (mm)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eReinforcement Details (uniformly distributed)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e38@16mm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e"},{"header":"4. Selection of earthquake ground motion","content":"\u003cp\u003eSeismic load uncertainties are considered in this study by using number of seismic records. Only Far field earthquakes are chosen for this study considering the building is located at least 10 km away from faults (Ravichandaran and Klinger, [17]). Sarkar \u003cem\u003eet. al\u003c/em\u003e [18] developed seismic fragility curves using natural and synthetic ground motions and concluded that, it is conservative approach to use synthetic ground motions. The 22 pairs of far-field seismic records given in FEMA P695 [19] are chosen for the analysis and they are modified to match the Greek Design response spectrum. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Shows Greek Design response spectrum chosen with the spectrum type as 1 and the group type as C with the importance Class III and the damping value is 5%. Selected earthquakes are modified using Seismomatch [20] software and modified seismic records response spectrum are shown in the Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e4\u003c/span\u003e. Further these records are scaled to 0.1 PGA to 1 PGA linearly.\u003c/p\u003e "},{"header":"5. Nonlinear Modelling of elements","content":"\u003cp\u003eA series of nonlinear time history analyses (N-LTH) of RC frames have been performed. Seismostruct software is used for all analyses. Force-based nonlinear beam column element that consider the spread of plasticity along the element is used for modelling the beams, columns and Shear walls. Formulation of the fiber-based element can be seen in Lee and Mosalam [21]. The Concrete is modelled according to Mander et. al [22]. and reinforcements are modelled according to Menegotto and Pinto [23]. Similar kind of non-linear material modelling are found in [24], [25].Rayleigh damping is used in the present study, Eigenvalue analysis is carried out for both bare frame building and with retrofitted shear walls. Calculation of Rayleigh damping is shown in Table III.\u003c/p\u003e \u003cp\u003eTable III. Damping used for different frames\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabd\" border=\"1\"\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFrame type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003ePeriod,\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(s\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBare Frame\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.645\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.214\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStrengthened frame (Shear wall)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.365\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.085\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"6. Probabilistic seismic demand models and Fragility curves","content":"\u003cp\u003eIn the context of the five-storey retrofitted building using shear walls, a comprehensive analysis has been undertaken to establish (PSDMs) for both the original bare frame and the retrofitted structure. The analysis encompasses two distinct models, each representing different configurations of the selected building. The (NTHA) has been applied to the models, with particular focus on monitoring Inter-Storey Drifts (ISD) at each level of the building. Subsequently, the maximum ISD at each storey is plotted against the corresponding (PGA) in a logarithmic plot. Through rigorous regression analysis, optimal curves are derived, characterizing the PSDM for each storey level are developed (Figs. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e \u0026amp; \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e). The coefficients denoted as \u0026apos;a\u0026apos; and \u0026apos;b\u0026apos; in the power law model (refer Eq.\u0026nbsp;2) are derived through the optimization of a best-fit curve. Utilizing the dataset comprising (ISD) and (PGA) values, the dispersions in the Intensity Measure (\u003cem\u003e\u0026beta;EDP/IM\u003c/em\u003e) are computed. This calculation, outlined in Eq.\u0026nbsp;4, is performed individually for each storey across all frames.\u003c/p\u003e\n\u003cp\u003eDamage Limitation, Significant Damage, and Collapse Prevention are three crucial performance levels that are estimated to be 1% (DL), 2% (SD), and 4% (CP) in the current study. Fragility curves for various performance levels, including Damage Limitation (DL), Significant Damage (DM), and Collapse prevention (CP), are developed after PSDM models using Eq. 3 and dispersions (\u0026beta;D|PGA, \u0026beta;c, and \u0026beta;m) for all the models are computed as shown in Fig. 7.\u003c/p\u003e\n\u003cp\u003eIn order to understand the behavior of bare frame in comparison with a retrofitted shear wall building the corresponding fragility curves are compared. In a comprehensive comparison of the fragility curves for Damage Limitation (DL), Significant Damage (DM), and Collapse Prevention (CP) between the bare frame and retrofitted building models, distinct trends and improvements are seen. For the Damage Limitation aspect at a PGA of 0.7, the bare frame model exhibits a vulnerability of 94%, whereas the shear wall retrofitted model demonstrates a significant enhancement, reducing the vulnerability to 62%. This stark reduction underscores the effectiveness of shear wall retrofitting in minimizing damage under moderate seismic events. Similarly, in the context of Significant Damage, the bare frame model registers an 80% vulnerability, while the shear wall retrofitting substantially mitigates the risk, yielding a vulnerability of only 32%. The most substantial disparity is observed in Collapse Prevention, where the bare frame model displays a vulnerability of 54%, while the shear wall retrofitted model impressively reduces this vulnerability to a mere 10%. These values collectively illustrate the considerable resilience and structural integrity conferred by shear wall retrofitting methods for buildings designed according to old codes., emphasizing its pivotal role in enhancing the overall seismic performance and risk mitigation capabilities of the five-storey building.\u003c/p\u003e"},{"header":"7. Conclusion","content":"\u003cp\u003eStructures designed without considering seismic criteria and lacking ductile detailing face significant damage when subjected to earthquake ground motion. The imperative for retrofitting or strengthening such earthquake-prone or damaged buildings has intensified, particularly in the result of recent seismic events. This study focuses on the seismic analysis of a five-storey building using Seismostruct software, with the incorporation of shear walls identified as a highly efficient strategy for enhancing seismic resilience. Structural retrofitting at the system level becomes imperative when the entire lateral load-resisting system is deemed deficient. Specifically, shear wall strengthening techniques are used to fortify failed beams and columns. The key findings of this investigation are as follows:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eThe addition of new concrete shear walls emerges as a widely adopted and proven technique, effectively controlling global lateral drifts and minimizing damages in frame structures.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThe strategic placement of shear walls within the frame system emerges as a critical consideration, significantly reducing lateral forces.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eNotably, the introduction of shear walls results in a substantial reduction of up to 48% in the maximum storey drift of the building. This underscores the efficacy of shear wall retrofitting in enhancing structural stability and minimizing seismic-induced deformations.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eM.S. Yousif did nonlinear modelling for selected buildings, performed dynamic time history analysis and developed Manuscript. Wrote the main manuscript and prepared figures with tables and all necessary information to create the script. D.C. Haran explored the methods to develop fragility curves, and developed fragility curves based on dynamic time history analyses. And provided guidance throughout the script contributing to the overall script's coherence and conceptual framework.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eLazaris, A. Seismic evaluation and retrofitting of an existing building in Athens using pushover analysis, 2019.\u003c/li\u003e\n\u003cli\u003eBritish Standards Institution. Eurocode 8: Design of structures for earthquake resistance. London, BS EN 1998.\u003c/li\u003e\n\u003cli\u003eSiesmosoft ltd, SeismoStruct (Version 2022 Release-4) [Computer Software]. https://seismosoft/products/seismostruct (2022)\u003c/li\u003e\n\u003cli\u003eAlashkar, Y., Nazar, S. and Ahmed, M. A Comparative Study of Seismic Strengthening of RC Buildings by Steel Bracings and Concrete Shear walls\u003cem\u003e. International Journal of Civil and Structural Engineering Research\u003c/em\u003e, Vol. 2(Issue 2), p.pp: (24-34), 2015.\u003c/li\u003e\n\u003cli\u003eHaikal, C. and Muca, M. Seismic analysis and retrofitting of an existing multi-storey building in Stockholm, 2018.\u003c/li\u003e\n\u003cli\u003eSahin, C. Seismic Retrofitting of Existing Structures, 2014.\u003c/li\u003e\n\u003cli\u003eD\u0026rsquo;Amato, M, Laguardia, R. and Gigliotti, R. Seismic Retrofit of an Existing RC Building With Isolation Devices Applied at Base, 2020\u003c/li\u003e\n\u003cli\u003eDumaru, R., Rodrigues, H. and Varum, H. Comparative study on the seismic performance assessment of existing buildings with and without retrofit strategies. \u003cem\u003eInternational Journal of Advanced Structural Engineering,\u003c/em\u003e [online] 10(4), pp.439\u0026ndash;464, 2018\u003c/li\u003e\n\u003cli\u003eTzavidis, A D; Nikolaidis, Th N; Baniotopoulos, C C. Evaluation of a strengthening approach for existing RC buildings in terms of resilience and cost efficiency, 2023\u003c/li\u003e\n\u003cli\u003eSuresh Kannan, S. Seismic Analysis of Soft Storey Building in Earthquake Zones, 2023.\u003c/li\u003e\n\u003cli\u003eK. Natraj, S. Elavenil and S Ragavendra. Analysis and Design of Multi-Story Building Retrofitted with Carbon Fibre Reinforced Polymer. \u003cem\u003eIOP conference series,\u003c/em\u003e 1125(1), pp.012021\u0026ndash;012021. 2022\u003c/li\u003e\n\u003cli\u003eShendkar, Mangeshkumar R; Kontoni, Denise-Penelope N; Işık, Ercan; Mandal, Sasankasekhar; Maiti, Pabitra Ranjan; et al. Influence of Masonry Infill on Seismic Design Factors of Reinforced-Concrete Buildings, 2022\u003c/li\u003e\n\u003cli\u003eKANEPE, T. P. Tassios. Code Of Interventions, Available at: https://ecpfe.oasp.gr/sites/default/files/files/full.pdf, 2013.\u003c/li\u003e\n\u003cli\u003eCornell, C. A., Jalayer, F., Hamburger, R. O. and Foutch, D. A. The probabilistic basis for the 2000 SAC/FEMA steel moment frame guidelines, \u003cem\u003eJournal of Structural Engineering\u003c/em\u003e, vol.128, no.4, pp.526-533, 2002.\u003c/li\u003e\n\u003cli\u003eCelik, O. C. and Ellingwood, B. R. Seismic fragilities for non-ductile reinforced concrete frames - Role of aleatoric and epistemic uncertainties, \u003cem\u003eStructural Safety\u003c/em\u003e, vol.32, no.1, pp.1-12, 2010.\u003c/li\u003e\n\u003cli\u003eATC 58, 100% Draft. Guidelines for Seismic Performance Assessment of Buildings, \u003cem\u003eApplied Technology Council\u003c/em\u003e, Redwood City, CA. 2012.\u003c/li\u003e\n\u003cli\u003eRavichandran, S. S. and Klinger, E. R. Seismic design factors for steel moment frames with masonry infills: Part I, Earthquake Spectra, 28(3):1189-1204, 2012.\u003c/li\u003e\n\u003cli\u003eSarkar Pradip, Davis Robin, Haran Pragalath, D.C., Seismic fragility curves using natural and synthetic ground motions, IABSE Conference, Vancouver 2017: Engineering the Future - Report, ,Vol. 109, pp. 1274\u0026ndash;1280, 2017.\u003c/li\u003e\n\u003cli\u003eQuantification of Building Seismic Performance Factors. Available at: https://nehrpsearch.nist.gov/static/files/FEMA/PB2010101512.pdf, \u003cem\u003eApplied Technology Council\u003c/em\u003e, Redwood City: California for the Federal Emergency Management Agency, Washington, D.C, 2008.\u003c/li\u003e\n\u003cli\u003eSiesmosoft ltd, SeismoMatch (Version 2022 Release-1 Build-50) [Computer Software]. https://seismosoft/products/ Seismomatch (2022)\u003c/li\u003e\n\u003cli\u003eLee, T. H. and Mosalam, K. M. 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In order to arrive at an appropriate retrofitting scheme, the structure's vulnerability and a detailed seismic evaluation are essential, where seismic fragility curves are one of the tools for seismic evaluation. In this study, a 5-storey typical existing Greek building is selected which was designed according to Greek Code. The selected buildings are modelled for nonlinear analysis with and without shear walls. Seismic records are selected, scaled and modified according to Greek Response spectrum. Dynamic time-history analysis is performed. Inter-story drift is considered as damage parameter and fragility curves are developed for various performance levels. This holistic approach contributes to the broader understanding of seismic retrofitting methodologies and their applicability to existing structures, particularly those designed under specific regional codes such as the Greek Code. The result shows that there are significant improvements after retrofitting the building using shear walls.","manuscriptTitle":"A Performance Evaluation of Seismic Retrofit of Existing Greece Building","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-01-08 17:20:34","doi":"10.21203/rs.3.rs-3834368/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"adaf33ce-ca77-4c70-af74-b76214b53c40","owner":[],"postedDate":"January 8th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-01-16T08:44:17+00:00","versionOfRecord":[],"versionCreatedAt":"2024-01-08 17:20:34","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3834368","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3834368","identity":"rs-3834368","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}