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The recent seismic activity highlights the crucial need to enhance seismic design and safety assessment methods, particularly for irregular structures, in both new and existing constructions. The present study focuses on structural irregularities in elevation for buildings, as the design of structural systems involves multiple variables that often result in irregularities in many buildings. This work aims to perform a comparative assessment of the criteria adopted for the evaluation of the structural irregularities in elevation present in European and international seismic codes. This paper is structured as follows: Firtsly, it discusses structural irregularities and more specifically the most common types of structural damage due to seismic events. Then, it shows the documented experiences of structural damages in seismic events associated with structural irregularities in China, Italy, Spain, Nepal and Mexico. Additionaly, it discusses the requirements of the standards on irregularities and their limitation in that matter. At the end of this section, the different approaches of each code in irregularities in elevation are compared. All assessed seismic codes addresses the structural irregularity issue, attributing the desired characteristics of a seismic-resistant structure. However, there are considerable development differences between norms, demonstrated on ambiguity of few codes on criteria of vertical irregularies. [ABSTRACT FROM AUTHOR]

Irregular reinforced concrete (RC) buildings constitute a significant portion of the existing housing stock. A common type of irregularity is in the form of discontinuity in the vertical framing elements, which can exacerbate their seismic vulnerability. The design guidelines available in seismic design codes essentially cater to only regular buildings, and the safety of such buildings, even when the other guidelines of the codes are followed, is doubtful. This article evaluates the vulnerability of RC frame buildings with discontinuity in columns designed for modern seismic codes, in the form of seismic collapse capacity, collapse resistance against maximum earthquake demand level, and failure mechanism. The adequacy and limitations of the provisions of the seismic design codes are evaluated for such buildings. Analysis results show that the sequential analysis of buildings considering the construction staged effects, considerably affects the design and hence the collapse failure mechanism of even low‐ and mid‐rise buildings. The results also underline the importance of strong column–weak beam design in the seismic performance of the floating column buildings. The vertical component of ground motion is also observed to be relatively more crucial in floating column buildings. [ABSTRACT FROM AUTHOR]

Effect of different proportioning of lateral force-resisting system in the orthogonal directions, on seismic collapse capacity and fragility of reinforced concrete buildings is investigated. Buildings with different structural systems and configurations, are designed for a modern seismic design code. To simulate the structural collapse, the hysteretic models of beams, columns, and shear walls are duly calibrated using experimental tests results. Results show that if the buildings of a given height are designed for the same hazard level, these show equal levels of safety against collapse, irrespective of the proportioning of lateral load resisting systems in the orthogonal directions. [ABSTRACT FROM AUTHOR]

This paper addresses the application of conventional (force-based) seismic design methodologies to hybrid RC-steel systems. The q-factor-based EC8-3 seismic assessment procedure is first reviewed. A case-study application follows, analyzing and discussing the difficulties a practitioner will face when assessing the efficiency of a steel-brace retrofitting system designed within the framework of EC8-1. Afterward, the performance of the obtained retrofitted structure is evaluated using nonlinear analysis. The obtained results are discussed in light of the EC8-3 performance requirements, and conclusions are drawn about the adequacy of the force-based design (FBD) methodology (and associated q-factors) for such situations. The study shows that the process does not ensure the adequate seismic behavior of the retrofitted structures. It thus calls for the development of an effective performance-based design methodology that explicitly considers the interaction between the two structural systems (RC structure and steel braces), namely the influence of the steel braces' resistance on the deformation capacity of RC members. [ABSTRACT FROM AUTHOR]

This study provides a thorough comparative analysis of structural design strategies across different ductility classes and seismic action levels, as outlined in Eurocode 8 provisions. The analysis is carried out for 5- and 10-storey building examples. The research highlights key findings regarding base shear demand, storey displacements, sensitivity coefficients, and other crucial structural performance parameters. Those findings indicate that while buildings designed for DCM and DC3 ductility classes generally exhibit similar base shear values and roof displacements, exceptions arise, particularly in the lower-storey buildings where DC2 demonstrates significantly lower roof displacements. The influence of strut inclination on design bending moments is also noted, underscoring its significance in structural behaviour. Moreover, the study delves into interstorey drift ratio (IDR) demands from analysis, revealing consistent displacement patterns across various structures with notable implications for deflection and stability. Additionally, insights into chord rotation control, sensitivity coefficients, and reinforcement quantities shed light on their behaviour under diverse seismic conditions, aiding in optimising structural design strategies. • The study compares the design demands of buildings for some ductility classes and seismic action based on the Eurocode 8. • Analysis shows similarities in base shear values and roof displacements for buildings designed for DCM and DC3. • Structures like DC2.W.50.5 and DC3.W.50.5 exhibit higher resistance to deformations compared to others. • Torsional rotation varies by height, with DC3.W.75.5 showing the highest average torsional angle in 5-story buildings. • The sensitivity coefficients highlight structural behavior, indicating minor to significant impacts on internal forces. [ABSTRACT FROM AUTHOR]

The existing practice to estimate seismic performance of a regular building is to carry out nonlinear time history analysis using two-dimensional models subjected to unidirectional excitations, even though the multiple components of ground motion can affect the seismic response, significantly. During seismic shaking, columns are invariably subjected to bending in two orthogonal vertical planes, which leads to a complex interaction of axial force with the biaxial bending moments. This article compares the seismic performance of regular and symmetric RC moment frame buildings for unidirectional and bidirectional ground motions. The buildings are designed and detailed according to the Indian codes, which are at par with the other modern seismic codes. A fiber-hinge model, duly calibrated with the biaxial experimental results, is utilized to simulate the inelastic behavior of columns under bidirectional bending. A comparison of the estimated seismic collapse capacity is presented, illustrating the importance of considering the bidirectional effects. The results from fragility analysis indicate that the failure probabilities of buildings under the bidirectional excitation are significantly higher as compared to those obtained under the unidirectional excitation. [ABSTRACT FROM AUTHOR]

This paper analyses the adequacy of the q‐factor approach when applied to hybrid RC‐steel systems. This approach is prescribed by EC8‐1 as the basic design method, and usually referred to as the most conservative. However, due to its simplicity and popularity for the design of new structures, practitioners are more likely to resort to it, than to the more complex nonlinear static and dynamic procedures, when dealing with the seismic assessment and strengthening of existing RC buildings. A case‐study application is thus presented to analyse and discuss the difficulties a practitioner will face when assessing the efficiency of a steel‐brace retrofitting system designed within the framework of EC8‐1. [ABSTRACT FROM AUTHOR]

Eurocode 8 is undergoing a thorough revision process encompassing a significant number of changes. In this work, the novel ductility classes, drift limits for damage limitation, local ductility conditions, and corresponding detailing prescriptions are presented and discussed. It is paramount to analyse and contrast these modifications with the current provisions of Eurocode 8. In order to assess the impact of such revisions, an extensive examination was conducted on ten symmetrical moment-resisting frame (MRF) buildings. These buildings are regular in plan and in elevation and are not torsionally flexible. The analysis was carried out following both the current and the second-generation Eurocode 8 provisions, with the results being compared in order to evaluate the effectiveness of the new design and detailing provisions. The study outcomes revealed that the DCM, DC2, and DC3 structures demonstrated different trends in their detailing demands for local ductility and capacity design. Differences in reinforcement quantities were observed between DCM and DC2, as well as DC2 and DC3, for 5-storey and 10-storey buildings. The design approach focused on individual member detailing requirements, to optimize design, while maintaining the overall concrete quantities. These insights offer valuable economic considerations for various structural configurations under strong seismic actions. • The comparison between DCM - DC2 and DC2 - DC3, shows variations in the longitudinal and transverse reinforcement. • Buildings designed for DCM and DC3 ductility classes behave similarly. • There is a consistent linear trend where capacity design in shear exceeds seismic design demand for all ductility classes. • Capacity design in shear is generally higher than seismic design demand, indicating adequate shear resistance. • Some columns show substantially higher values, possibly due to higher moment values at lower storeys. [ABSTRACT FROM AUTHOR]

A large number of infilled RC frame buildings have undergone moderate to extensive structural damages and even collapsed after the 2015 Gorkha earthquake. The repair and maintenance works are still being carried out in the existing RC buildings, many of them without any consultation with design engineers. Such practices are likely to create a benefit of doubt on the efficiency of the retrofitting works and repair/maintenance works. Therefore, the present study aims to evaluate the seismic performance of the existing non- and pre-engineered buildings, and later employed retrofit measures that are commonly practised in the region. The analytical results revealed that the selected buildings were seismically deficient and are most likely to undergo extensive damage to collapse states, at 0.3 g PGA. It was found that the retrofit measure significantly enhances the stiffness, maximum strength and ductility in the existing buildings. The pushover curves indicated that the steel bracing highly increased the stiffness, strength and ductility capacity in all case study buildings. The steel-braced building was recorded to have increased the maximum base shear capacity by almost ten times for the soft-storey MRT1 building. Similarly, the retrofit measures also eliminated the potential single storey drift concentration recorded in the original building, such that a uniform inter-storey drift profile can be attained throughout. The conditional probability of collapse for the case study buildings, at 0.3 g PGA, ranges from 13.5 to 42% and could be minimized below 4% in the worst case scenario for the shear wall. All the numerical results demonstrated that steel bracing was much more effective in enhancing the seismic performance of the existing buildings. [ABSTRACT FROM AUTHOR]

Considering the likely unfavorable behavior under seismic action of adobe construction, this article aims at providing a seismic fragility characterization of two adobe Portuguese traditional buildings, using numerical models calibrated over experimental results. The study of such two case-study buildings in the region of Aveiro contributes to the understanding of the seismic fragility of adobe construction in the region in general. The buildings were numerically modeled to estimate their structural behavior under seismic loading using adobe material properties that were calibrated based on the experimental results of a cyclic in-plane test of a full-scale double-Tshaped adobe wall. The method chosen to characterize adobe masonry and model its nonlinear behavior followed a total strain crack-based macro-modeling (TSCM) approach, whereas pushover analysis was carried out to reproduce the pseudo-static experimental test in order to enable a refined calibration of adobe masonry mechanical properties. Fragility functions were then derived, based on the above-mentioned numerical models, using nonlinear static analysis, bringing further insight on the seismic fragility of traditional Portuguese adobe construction. [ABSTRACT FROM AUTHOR]

This article addresses the laboratory testing of a full-scale double-T shaped adobe wall, under in-plane horizontal cyclic loading of increasing amplitude, with the aim of contributing to the understanding of the seismic behavior of adobe structures. The wall was built with lime adobes taken from an existing building and mortar with a traditional composition. The behavior of the wall was assessed in terms of: shear stress versus horizontal drift and moment versus rotation relationships; maximum lateral strength; drift and rotation at peak stress; evolution of stiffness, lateral displacements, dissipated energy, and natural frequency; and damage pattern. The wall exhibited brittle behavior and in-plane strength corresponding to 56% of the vertical load. Cracking was observed with an X-shaped pattern whereas no sliding occurred at its base. This research supported the subsequent development of a repair and retrofit solution and also of numerical models to simulate the seismic behavior of two adobe buildings. [ABSTRACT FROM AUTHOR]

The assessment of seismic vulnerability and strengthening of existing buildings is a topic of relevant importance and priority, as evidenced in recent earthquakes around the world, particularly in Southern European countries. Some architectural solutions adopted in the decade of 1970, combined with the common design and construction practices at that time, particularly in what regards to the seismic design, influences the seismic vulnerability of these structures. The objective of the present work is to study, based on numerical analyses, different strengthening techniques to adopt into an existing building with the behaviour potentially governed by soft storey mechanism when subjected to seismic actions. The influence of the masonry infill panels will be studied and the seismic safety of the building will be assessed. Also, different strengthening techniques will be tested to fix/eliminate the soft storey like response, namely: RC columns jacketing, addition of steel bracings with and without shear link and addition of RC shear walls. The strengthened buildings results will be compared with the results of the original structure, deducting about the structural efficiency by each type of strengthening technique adopted. The costs associated to each solution will be determined and compared with the market value of the building. [ABSTRACT FROM AUTHOR]

Purpose – When a numerous amount of buildings was built in reinforced concrete, in a period when the regulations did not have the design philosophy for the occurrence of earthquakes, it is of extreme importance to carry out full and effective structural assessments, specially considering and comparing bare frame and infilled structure. The paper aims to discuss these issues. Design/methodology/approach – Among several possibilities to make the evaluation as, simplified, linear analysis and static non-linear analysis, the non-linear dynamic can provide the most accurate numerical behaviour compared to the real one. The time-history non-linear analyses are developed on the software SeismoStruct for different levels of intensity. Local verifications are then applied separately from both Eurocode and Italian Code. Findings – The application of validated models for the analysis of real buildings allows a complete seismic assessment. The level of uncertainty increases integrating particularities regarding the infill masonry walls. The paper shows important global and local seismic safety for these complex typology of buildings. Originality/value – A representative common concrete structure without seismic provisions is first analysed and discussed in terms of global behaviour, deformations and progression of forces. The case study structure is considered both as bare structure and with integrated infill panels. It is also discussed in a local level, about brittle and ductile mechanisms, and extra comparisons between different interpretations of different standards. The case study structure is considered both as bare structure and with integrated infill panels. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) buildings in Nepal are constructed with RC frames and masonry infill panels. These structures exhibit a highly non-linear inelastic behavior resulting from the interaction between the panels and frames. This paper presents an extensive case study of existing RC buildings in Nepal. Non-linear analyses were performed on structural models of the buildings considered as a bare frame and with masonry infill, in order to evaluate the influence of infill walls on the failure mechanisms. Five three-storey buildings with different structural configurations and detailing were selected. The effect of masonry infill panels on structural response was delineated by comparing the bare-framed response with the infill response. Seismic performance is evaluated with regard to global strength, stiffness, energy dissipation, inter-storey drift, and total deflection of the structure. A parametric analysis of structures with masonry infill is also performed. For this, the influence of different material properties is studied, namely diagonal compressive stress, modulus of elasticity and tensile stress of masonry infill panels. Study results show that masonry infill increases the global strength and stiffness of the structures; it decreases the inter-storey drift and hence the total displacement of the structure. The results quantify the influence of the infill panels on structural response and, in particular, the effect of the diagonal compressive strength of the masonry wall. [ABSTRACT FROM AUTHOR]

One of the main challenges in earthquake risk mitigation is the assessment of existing buildings not designed according to modern codes and the development of effective techniques to strengthen these structures. Particular attention should be given to RC frame structures with masonry infill panels, as demonstrated by their poor performance in recent earthquakes in Europe. Understanding the seismic behaviour of masonry-infilled RC frames presents one of the most difficult problems in structural engineering. Analytical tools to evaluate infill-frame interaction and the failure mechanisms need to be further studied. This research intends to develop a simplified macro-model that takes into account the out-of-plane behaviour of the infill panels and the corresponding in-plane and out-of-plane interaction when subjected to seismic loadings. Finally, a vulnerability assessment of an RC building will be performed in order to evaluate the influence of the out-of-plane consideration in the building response. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Kathmandu Valley is geologically located on lacustrine sediment basin, characterized by a long history of destructive earthquakes. The past events resulted in large structural damage, loss of human life's and property, and interrupted the social development. In recent years, the earthquake risk in this area has significantly increased due to uncontrolled development, poor construction practices with no earthquake safety provisions, and lack of awareness amongst the general public and government authorities. In this context, this study explores the realistic situation of earthquake losses due to future earthquakes in Kathmandu Valley. To this end, three municipalities: (a) Kathmandu Metropolitan City, (b) Lalitpur Sub-Metropolitan City and (c) Bhaktapur Municipality are selected for a case study. The earthquake loss estimation in the selected municipalities is performed through the combination of seismic hazard, structural vulnerability, and exposure data. Regarding the seismic input, various earthquakes scenario considering four seismic sources in Nepal are adopted. For what concerns the exposure, existing literature describing the construction typologies and data from the recent national census survey of 2011 are employed to estimate ward level distribution of buildings. The economic losses due to the earthquake scenarios are determined using fragility functions. Finally, the ward level distribution of building damage and the corresponding economic losses for each earthquake scenario is obtained using the OpenQuake-engine. The distribution of building damage within the Kathmandu Valley is currently being employed in the development of a shelter model for the region, involving various local authorities and decision makers. [ABSTRACT FROM AUTHOR]

Seismic risk in the form of impending disaster has been seen from past records that moderate-to-large earthquakes have caused the loss of life and property in all parts of Nepal. Despite the availability of new data, and methodological improvements, the available seismic hazard map of Nepal is about two decades old. So an updated seismic hazard model at the country level is imperative and logical. The seismic hazard and risk model constitute important tools for framing public policies toward land-use planning, building regulations, insurance, and emergency preparedness. In fact, the reliable estimation of seismic hazard and risk eventually minimizes social and economic disruption caused by earthquakes. In this frame of reference, the seismic risk assessment at a country level is elementary in reducing potential losses stemming from future earthquakes. Thus, this study investigates structural vulnerability, seismic risk, and the resulting possible economic losses owing to future earthquakes in Nepal. To this end, seismic risk assessment in Nepal is done using an existing probabilistic seismic hazard, a newly developed structural vulnerability, and recently released exposure data. The OpenQuake-engine, the open-source platform for seismic hazard and risk assessment from the Global Earthquake Model initiative, was used to calculate the seismic hazard and risk in Nepal. The seismic hazard and mean economic loss map were formulated for the 1, 2, 5, and 10 % probability of exceedance in 50 years. Finally, the distribution of building damage and corresponding economic losses due to the recurrence of the historical 1934 earthquake was presented in this study. [ABSTRACT FROM AUTHOR]

The seismic damages commonly observed on beam-column joints of old reinforced concrete structures, built with plain bars and without proper detailing, justifies the need to further study the behaviour of this type of structures. The response of these structures when loaded cyclically, as occurs during the earthquakes, is partially controlled by the bond properties between the reinforcing bars and the surrounding concrete. This paper presents the results of an experimental campaign of unidirectional cyclic tests carried out on six full-scale beam-column joints built with plain bars. These joint specimens are representative of existing reinforced concrete structures, that is, built without adequate reinforcement detailing for seismic demands. For comparison, an additional specimen is built with deformed bars and tested. The seven specimens are designed and detailed to allow the investigation of the influence of bond properties, lapping of the longitudinal bars in columns and beams, bent-up bars in the beams, slab contribution and concrete strength. The lateral force-drift relationships, global dissipated energy evolution, contribution of the joint, beams and columns to the global dissipated energy, ductility, equivalent damping, final damage observed, homogenized reinforced concrete damage index, displacement components, curvature evolutions and Eurocode requirements are presented and discussed. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The seismic vulnerability assessment of Nepalese Pagoda temples is essential as these monuments are recognized with high historical and heritage value. Many of these architectural and culture heritage are listed in UNESCO World heritage. Rigorous vulnerability assessment of these structures and the implementation of appropriate retrofitting solutions can help reduce the levels of physical damage and the economic impact of future seismic events. This paper approaches the seismic vulnerability assessment of Pagoda temples by applying a simplified methodology developed. The proposed methodology adopted in this study was based on a vulnerability index used for the evaluation of damage and the study of loss scenarios on a large scale. Over 78 Pagoda temples located in three cities of the Kathmandu valley (Nepal) were assessed using this methodology. The results of the vulnerability assessment together with the surveyed database and damage classification were integrated into a GIS tool, allowing the spatial visualation of damage scenarios, which is potentially useful for the planning of retrofitting priorities to mitigate and manage seismic risk. [ABSTRACT FROM AUTHOR]

Most current seismic design includes the nonlinear response of a structure through a response reduction factor ( R). This allows the designer to use a linear elastic force-based approach while accounting for nonlinear behavior and deformation limits. In fact, the response reduction factor is used in modern seismic codes to scale down the elastic response of a structure. This study focuses on estimating the actual ' R' value for engineered design/construction of reinforced concrete (RC) buildings in Kathmandu valley. The ductility and overstrength of representative RC buildings in Kathmandu are investigated. Nonlinear pushover analysis was performed on structural models in order to evaluate the seismic performance of buildings. Twelve representative engineered irregular buildings with a variety of characteristics located in the Kathmandu valley were selected and studied. Furthermore, the effects of overstrength on the ductility factor, beam column capacity ratio on the building ductility, and load path on the response reduction factor, are examined. Finally, the results are further analyzed and compared with different structural parameters of the buildings. [ABSTRACT FROM AUTHOR]

In structural analyses, masonry infill walls are commonly considered to be non structural elements. However, the response of reinforced concrete buildings to earthquake loads can be substantially affected by the influence of infill walls. In this article, an improved numerical model for the simulation of the behavior of masonry infill walls subjected to earthquake loads is proposed and analyzed. First, the proposed model is presented. This is an upgrading of the equivalent bi-diagonal compression strut model, commonly used for the nonlinear behavior of infill masonry panels subjected to cyclic loads. Second, the main results of the calibration analyses obtained with two series of experimental tests are presented and discussed: one on a single frame with one story and one bay tested at the LNEC Laboratory; and the second, on a full-scale four story and three-bay frame tested at the ELSA laboratory. [ABSTRACT FROM AUTHOR]

The main objective of this study is to analytically investigate the effectiveness of different strengthening solutions in upgrading the seismic performance of existing reinforced concrete (RC) buildings in Nepal. For this, four building models with different structural configurations and detailing were considered. Three possible rehabilitation solutions were studied, namely: (a) RC shear wall, (b) steel bracing, and (c) RC jacketing for all of the studied buildings. A numerical analysis was conducted with adaptive pushover and dynamic time history analysis. Seismic performance enhancement of the studied buildings was evaluated in terms of demand capacity ratio of the RC elements, capacity curve, inter-storey drift, energy dissipation capacity and moment curvature demand of the structures. Finally, the seismic safety assessment was performed based on standard drift limits, showing that retrofitting solutions significantly improved the seismic performance of existing buildings in Nepal. [ABSTRACT FROM AUTHOR]

During the last years, several studies have been made aiming to assess the out-of-plane seismic response of unreinforced stone masonry structures. This fact led to the development of a wide variety of models and approaches, ranging from simple kinematic based analytical models up to complex numerical simulations. Nevertheless, for the sake of simplicity, the out-of-plane seismic response of a masonry wall pier may be obtained by means of a simple single-degree-of-freedom system while still providing good results. In fact, despite the assumptions associated with such a simple formulation, it is also true that the epistemic uncertainty inherent with the selection of appropriate input parameters in more complex models may render them truly ineffective. In this framework, this paper focuses on the study of the out-of-plane bending of unreinforced stone masonry walls (cantilevers) by proposing a simplified analytical approach based on the construction of a linearized four-branch model, which is used to characterize the linear and nonlinear response of such structural elements through an overturning moment-rotation relationship. The formulation of the four-branch model is presented and described in detail and the meaningful parameters used for its construction are obtained from a set of experimental laboratory tests performed on six full-scale unreinforced regular sacco stone masonry specimens. Moreover, a parametric analysis aiming to evaluate the effect of these parameters’ variation on the final configuration of the model is presented and critically discussed. Finally, the results obtained from the application of the developed four-branch model on real unreinforced regular sacco stone masonry walls are thoroughly analysed and the main conclusions obtained from its application are summarized. [ABSTRACT FROM AUTHOR]