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The novelty of the research is the development of closed-form equations to assess the effective capacity of retrofitting interventions to reduce the seismic risk of existing buildings. The goal of the proposed procedure is to provide decision-making in the context of the Loss-Based Earthquake Engineering, whose purpose is the reduction of the seismic risk, which is herein computed through a monetary loss. The procedure consists of specifying performance targets (e.g. acceptable monetary losses, capital to invest, reduction of expected annual loss) and deriving engineering parameters, specifically the target fragility curves to achieve the established performance target. The identification of required fragility curves, in turn, allows to identify proper retrofitting interventions to mitigate the expected seismic loss. The method allows for estimating the maximum reduction of the annual average loss and the recommended capital to invest, accounting for the actual cost of the retrofitting alternatives and the nominal life of the building. In addition, it can be used to identify the payback period. With the aim of promoting the design procedure in the common practice, an existing reinforced concrete moment-resisting frame, retrofitted with three strengthening methods, is explored as case-study. [ABSTRACT FROM AUTHOR]

The paper presents a novel optimization framework aimed at the minimization of seismic retrofitting-related costs for existing unreinforced masonry building structures. The framework provides topology optimization of reinforcements (reinforced plasters) to implement in masonry walls for the accomplishment of seismic safety checks under the reference seismic load combinations. Optimization is carried out by a genetic algorithm (GA) developed in MATLAB®, which controls a 3D finite element equivalent frame model of the masonry structure developed in OpenSees. The GA routine iterates the reinforcement configurations employing specific genetic operators. The feasibility of each candidate retrofitting solution is assessed by performing in-plane shear and flexural safety checks of masonry walls. The framework is finally tested with a case study masonry structure supposed to be made of average-quality or poor-quality masonry. Results will show that the proposed framework can effectively provide the minimization of seismic retrofitting costs for existing masonry structures, giving as output the optimal configuration of the reinforcements within the structural layout. [ABSTRACT FROM AUTHOR]

The Swiss code SIA 269/8 for the seismic evaluation of existing structures is risk-based. It relies on the compliance factor αeff, defined as the ratio of the seismic capacity of an existing structure to the required seismic capacity of a hypothetical identical new structure, to indirectly evaluate the casualty risk posed by the existing structure. While it is convenient to have a direct relationship between the casualty risk and the degree of code compliance of the existing structure, it is debatable if the contributions of the seismic hazard, structural performance and occupancy to the casualty risk should be merged into a single quantity, conflicting with the multi-component nature of seismic risk. This paper presents a graphical framework to evaluate the seismic fatality risk for existing buildings. The framework is based on the PEER Center performance-based earthquake engineering methodology to provide a transparent view of the contributions of different sources of hazard and risk. Starting from a seismic hazard model, probabilistic seismic demand, damage and loss models are introduced, taking the uncertainty into account at each step. The final product of the proposed framework, a loss curve representing the (annual) exceedance rate of fatality counts, enables engineers and building owners to make better, risk-based decisions. The proposed framework is demonstrated for an existing building in Switzerland. Notably, in addition to the SIA 269/8 evaluation method, this demonstration compares eight hybrid approaches differentiated by the utilized structural assessment techniques (nonlinear static pushover vs. incremental dynamic analysis), uncertainty propagation in the demand model (record variability only vs. record variability and epistemic uncertainty) and solution strategies (closed-form vs. numerical) to find a practical compromise between the accuracy and the computational effort. A comparison of the obtained results shows that the SIA 269/8 evaluation method underestimates the fatality risk for the presented building and identifies a practical alternative based on the proposed graphical framework. [ABSTRACT FROM AUTHOR]

During the Puebla earthquake on September 19, 2017, about 200 steel buildings were subjected to a severe shake in the State of Mexico, Puebla, Morelos, and Mexico City. Although null or minor structural damage was reported, design and assembly opportunity areas in some beam–column moment joints were identified during the post-seismic inspections. With this in mind, six beam–column connections, widely employed in steel frame structures by the local practice, were experimentally tested through natural-scale. A damage concentration with not enough ductile response for high-ductility steel structures was reported. Welding parameters and fabrications details are emphasized to improve the response for new structures, and a rehabilitation suggestion for existing structures is discussed. This research is part of a study that aims to establish the vulnerability of steel structures in Mexico. [ABSTRACT FROM AUTHOR]

Seismic performance of existing buildings constructed before modern seismic design codes is one of the important problems of earthquake prone countries. Increasing life and economic losses after strong earthquakes shows the necessity of seismic performance assessment studies and methods. Therefore, in this study assessment methods recommended by different seismic codes were investigated and probabilistically assessed by comparing the fragility curves of existing low- to mid-rise RC structures. Building performances were determined according to TEC-2007, TBEC-2018, EC8/3 and ASCE 41-17. Eight different occupied buildings, classified according to construction dates (old and new) and story numbers (3 to 6), were selected and investigated by using these codes. At first, building capacity curves and damage limits, defined by the different code methods, were determined via pushover analyses. Structures were then subjected to more than 300 real strong ground motion (GM) records employing nonlinear dynamic analysis and fragility curves were obtained. Static analysis results showed that strength, stiffness and deformation capacity of new buildings are significantly higher than old ones according to all seismic codes considered and it is observed that TBEC-2018 gives the most conservative capacity estimations with respect to others. Comparison of fragility curves indicated that damage probabilities of TBEC-2018 and EC8/3 are higher than other seismic codes and this situation is valid for all story number and building age classes. In most cases TBEC-2018 and TEC-2007 results represent the upper and lower bounds of damage probabilities. It was also found that building age is the most effective parameter that affect the fragilities of existing buildings. Distribution of fragility curves imply that different code methods can give significantly different damage estimations under identical seismic demand levels. [ABSTRACT FROM AUTHOR]

Post-earthquake observations have outlined the poor seismic performance of substandard reinforced concrete (RC) beam-column joints in existing buildings. They often exhibit significant cracking even under moderate intensity earthquakes, compromising the seismic performance of the entire building. This makes the quantification of their residual capacity and the definition of reliable repairability thresholds critical. Different approaches are available in the literature to establish the repairability of RC joints. However, a simple crack width-based criterion is required for practitioners during in-situ inspections. This study deals with the definition of crack width-based fragility curves relying on numerical analyses. Those are carried out by using the validated finite element (FE) models, being capable of reproducing the initiation and development of cracks in RC joints. To this end, the uncertainties in material properties, influencing the seismic performance of structural components, are accounted for different joints. In particular, experimentally validated FE models are evolved to stochastic level by generating random variables of material properties with the stratified sampling scheme. Fragility curves representing a certain level of probability of exceeding the defined crack width at the joint back, joint core, and beam-to-joint interface are developed. An application of the proposed methodology for in-situ inspections is also presented, and the results of in-situ measurements of residual crack width from real buildings damaged by recent earthquakes are used for the validation. [ABSTRACT FROM AUTHOR]

Each existing building is required to be assessed before an impending severe earthquake utilizing Rapid Visual Screening (RVS) methods for its seismic safety since many buildings were constructed before seismic standards, without taking into account current regulations, and because they have a limited lifetime and safety based on how they were designed and maintained. Building damage brought on by earthquakes puts lives in danger and causes significant financial losses. Therefore, the fragility of each building needs to be determined and appropriate precautions need to be taken. RVS methods are used when assessing a large building stock since further in-depth vulnerability assessment methods are computationally expensive and costly to examine even one structure in a large building stock. RVS methods could be implemented in existing buildings in order to determine the damage potential that may occur during an impending earthquake and take necessary measures for decreasing the potential hazard. However, the reliability of conventional RVS methods is limited for accurately assessing large building stock. In this study, building inspection data acquired after the 2015 Gorkha, Nepal earthquake is used to train nine different machine learning algorithms (Decision Tree Classifier, Logistic Regression, Light Gradient Boosting Machine Classifier, eXtreme Gradient Boosting Classifier, Gradient Boosting Classifier, Random Forest Classifier, Support Vector Machines, K-Neighbors Classifier, and Cat Boost Classifier), which ultimately led to the development of a reliable RVS method. The post-earthquake building screening data was used to train, validate, and ultimately test the developed model. By incorporating advanced feature engineering techniques, highly sophisticated parameters were introduced into the developed RVS method. These parameters, including the distance to the earthquake source, fundamental structural period, and spectral acceleration, were integrated to enhance the assessment capabilities. This integration enabled the assessment of existing buildings in diverse seismically vulnerable areas. This study demonstrated a strong correlation between determining building damage states using the established RVS method and those observed after the earthquake. When comparing the developed method with the limited accuracy of conventional RVS methods reported in the literature, a test accuracy of 73% was achieved, surpassing conventional RVS methods by over 40% in accurately classifying building damage states. This emphasizes the importance of detailed data collection after an earthquake for the effective development of RVS methods. [ABSTRACT FROM AUTHOR]

Within the 2019–2021 research agreement between the Civil Protection Department (DPC) and the Network of University Laboratories for Earthquake Engineering (ReLUIS), the work package WP4 "Seismic Risk Maps—MARS" is specifically devoted to update the 2018 release of the Italian National Seismic Risk Assessment. To this end, the previously considered models of hazard, exposure and vulnerability will be critically reviewed and updated by taking advantage also from the results deriving from other WPs of the DPC-ReLUIS research project. In the present paper some of the most relevant aspects that are being introduced in the development of the new Italian risk maps have been described and shortly analysed. First, a significant upgrade of the vulnerability model implemented in the new version of the platform used for risk calculation (IRMA) is proposed, where reference to the six EMS-98 classes is made also considering regional vulnerability features. Further, empirical data from observed real damage are integrated with results from numerical simulations (mechanical approach), in particular for reinforced concrete buildings. Finally, some special construction types such as schools, churches and bridges are included in order to provide a more comprehensive view of the national risk. [ABSTRACT FROM AUTHOR]

The pipe-embedded building envelope is heavyweight thermally activated building systems (TABS) that has its pipe circuits inside building envelopes, but it has been seldom done in existing buildings. In this context, the concept of thermo-activated phase change material composite wall (TAPCW) is proposed to address the retrofitting challenges facing existing buildings, that is to substitute the pipe-embedded interlayer with macro-encapsulated PCM panel and relocate it to the exterior of the load-bearing layer. This work aims to investigate the thermal and energy saving performances of TAPCW under the winter climate conditions of northern China (i.e, Tianjin city) through a validated numerical model. Furthermore, performances of TAPCW are examined for some key factors, including the pipe spacing, PCM thickness, and orientation. The comparative study of three cases (case 1: TAPCW; case 2: normal wall integrated with PCM; and case 3: normal wall) verifies the effectiveness of TAPCW, and the daily heat loss (Groom), primary energy consumption (PE) and operation cost (C) can be reduced by 105.5%, 14.07%, and 56.03%, respectively. The parametric study shows that the pipe spacing has a more obvious influence than the PCM thickness, and the case 100/30 could be used as an optimum value for thermal barrier function, while the case 75/30 could provide a more efficient supplementary heating. Results also show that the TAPCW applied in the north orientation is more effective, which has the highest value of interior temperature increase (1.8 °C), effective PCM utilization ratio (14.14%), reduction size of PE (64.98%) and reduction size of C (34.43%). Overall, the proposed TAPCW presents a satisfactory thermal behavior in the heating season and could contribute to the progress of energy saving retrofit in the vast existing buildings. [ABSTRACT FROM AUTHOR]

The development of an accurate numerical model plays a key role for the proper assessment of structures. To this end, fibre modelling is widely considered as one of the most rigorous tool for an accurate evaluation of the seismic response of RC framed buildings. However, it has been noted that the interaction between fibre modelled RC beams and the rigid diaphragm adopted to simulate the concrete slab, typical of RC buildings, may cause the development of unintended fictitious axial forces in beams. These axial forces may lead to an overestimation of the resisting bending moment of beams cross section, thus altering the distribution of yielding in the structural members and the collapse mechanism. The goal of this paper is to overcome this drawback by introducing at one end of each beam a simple additional element, named axial buffer element. This element allows the axial deformation of the beam, prevents the development of fictitious axial force and does not invalidate the transmission of shear force and bending moment. The paper investigates the influence of the presence/lack of the axial buffer element on the seismic response of a set of RC buildings representative of real structures. For this purpose, incremental nonlinear dynamic analysis and nonlinear static analysis were conducted. [ABSTRACT FROM AUTHOR]

Seismic assessment of existing buildings is usually treated by international codes and guidelines through a semi-probabilistic approach based on the use of the so-called confidence factor (CF). Many authors revealed the inadequacy of such an approach, proposing alternative procedures based on: the updated calibration of the CF values together with its application to a parameter better representative of the structural response than the material strength, as usually adopted by codes; or the fully probabilistic approach by explicitly considering the propagation of uncertainties. Although the latter constitutes the most rigorous approach, it is still computationally demanding and difficult to be integrated as standard tool in the engineering practice. In this paper, the model parameter sensitivity analysis is proposed to support the seismic assessment in various aspects such as: pointing out, in an explicit way, the influence each uncertain parameter has on the structural response; supporting the set of an effective investigation plan; computing the essential parameters for a probabilistic-based verification on basis of a limited number of analyses. To the latter aim, the results from the model parameter sensitivity analysis executed according to the star design with central point approach are used to determine the median intensity measure (IMLS) and, with the help of the surface response technique, its dispersion (βLS), that are the two parameters of the fragility curve representing the capacity in the assessment. The proposed methodology is applied on two case studies, representative of existing URM buildings. Firstly, the IMLS and βLS values are calculated and thus compared, for the aim of validation, with the reference ones obtained from nonlinear static analyses performed on a large number of models generated using Monte Carlo simulations. Results obtained show a good estimate of the fragility curve parameters, compared to the rigorous probabilistic approach, highlighting the potential of the procedure proposed. [ABSTRACT FROM AUTHOR]

In order to achieve long-term targets for energy savings and emission reductions, substantial savings will be needed from existing buildings. For example, a recent analysis for the USA examines aggressive strategies to cut carbon emissions in half by 2040 and finds that in order to achieve this emission reduction target, more than half of existing buildings will need comprehensive energy efficiency retrofits. Germany is targeting an overall primary energy consumption reduction of 50% in 2050 including increasing building renovation rate to 2% per year. In France, ambitious targets have also been set for existing buildings: 50% reduction of primary energy consumption in 2050 compared to the 2012 level. Multiple countries have realized the importance of comprehensive building retrofits and have begun to adopt policies to spur these improvements. For example, Germany is emphasizing grants and loans through the KfW Development Bank, complemented with building and heating system labels, a new "heating check" programme, and possible technical renovation requirements. France has established a goal of bringing all buildings up to "A" performance level (on their A-G scale) by 2050 in order for them to be sold or leased, with lower performance levels required as soon as 2020. In the USA, the focus has been on a combination of rating and disclosure of energy use, financing, and technical assistance. Focused community approaches show promise. This paper summarizes the efforts, successes and challenges, future directions, and savings of building retrofit policies in the three countries. We conclude by contrasting the three countries and discussing areas of opportunity for these and other countries. [ABSTRACT FROM AUTHOR]

In this paper, a two-level multi-group approach to seismic performance assessment of existing building stock is presented and discussed. The first level of assessment is a simple visual screening based on the principles originally developed in FEMA (Rapid visual screening of buildings for potential seismic hazards: a handbook—FEMA 154 and 155, Applied Technology Council, Redwood City, 2002). The second level of assessment is based on an integrated approach (field survey, geotechnical investigations, experimental testing and analytical investigations) with incorporated procedures of different levels of complexity. The acceptance criteria for assessment are founded on demand versus capacity relationships, defined at element and story level. The developed approach was applied in performance assessment of the existing buildings in Karposh, which is one of the largest and oldest municipalities in Skopje, the capital of the Republic of Macedonia. Rapid visual screening (level_1 activity) was performed for 161 existing buildings. For two selected buildings, level_2 assessment was carried out. The results from the assessment were uploaded into the existing geo-referenced building inventory database on the Karposh municipality that represents a practical tool for the decision makers in enforcing decisions on design and construction of seismically resilient building environment. [ABSTRACT FROM AUTHOR]

Although energy simulation can provide valuable information about building energy behavior, the inaccuracy of input data can undermine the reliability of the results. Despite the vast literature about uncertainty analysis, little is known about the influence of building characteristics on the propagation of uncertainty through the energy simulation models. This study investigates the extent to which uncertain thermal conductivity and specific heat of structural layers affect the annual heating and cooling needs for a set of 144 simplified reference building configurations in three European climates. The analysis is carried out by means of a Monte Carlo technique coupled with TRNSYS hourly simulations. This study points out that the uninsulated residential buildings with a high aspect ratio, a small transparent surface with south exposure and low SHGC are more sensitive in the cooling needs estimation to the propagation of uncertainty in material properties. Similarly, the heating needs precision is greatly reduced when the uncertainty affects the thermal conductivity in uninsulated buildings with a low aspect ratio, a high SHGC and small window size. On the contrary, the uncertainty in specific heat is emphasized in buildings with external insulation having large windows oriented to either east or south and with glazing characterized by high SHGC. [ABSTRACT FROM AUTHOR]

The majority of existing buildings are not safe against earthquakes in most of the developing countries. Existing building stocks should be assessed with a seismic safety assessment method before a devastating earthquake. Cheaper and quicker rapid seismic safety assessment methods can be used instead of code-based assessment methods to determine the seismic performance of existing buildings. In this study, an approach was introduced to determine the seismic performance of existing mid-rise reinforced concrete buildings with fewer parameters and process steps than code-based detailed assessment procedures. Calibration and regulation of the introduced method were conducted on the 39 collapsed buildings' projects in 1999 Kocaeli, Turkey, earthquake. Finally, 55 existing buildings located in Eskisehir, Turkey, assessed with this calibrated method and the results were compared with the results of a code-based detailed assessment method; the results showed a very good agreement of about 83%. This study shows that the proposed method can be applied for the determination of the seismic performance of existing mid-rise reinforced concrete buildings quickly and without compromising reliability. [ABSTRACT FROM AUTHOR]

We performed large-scale earthquake economic loss estimations for France and cost-benefit analyses for several French cities by developing a semiempirical, intensity-based approach. The proposed methodology is inexpensive and easily applicable in case of a paucity of detailed information regarding the specific regional seismic hazard and the structural characteristics of the building stock, which is of particular importance in moderate-to-low seismic hazard regions. The exposure model is derived from census datasets, and the seismic vulnerability distribution of buildings is calculated using data mining techniques. Several hypothetical, large-scale retrofit scenarios are proposed, with increasing levels of investment. These cities, in their respective reinforced states, are then subjected to a series of hazard scenarios. Seismic hazard data for different return periods are calculated from regulatory accelerations from French seismic zoning. Loss estimations for the original (non-reinforced) configuration show high levels of expected building repair and replacement costs for all time spans. Finally, the benefits in terms of damage avoidance are compared with the costs of each retrofit measure. Relatively limited strengthening investments reduce the probability of building collapse, which is the main cause of human casualties. However, the results of this study suggest that retrofitting is, on average, only cost-effective in the parts of France with the highest seismicity and over the longest time horizons. [ABSTRACT FROM AUTHOR]

In recent years, several research groups have studied a new generation of analysis methods for seismic response assessment of existing buildings. Nevertheless, many important developments are still needed in order to define more reliable and effective assessment procedures. Moreover, regarding existing buildings, it should be highlighted that due to the low knowledge level, the linear elastic analysis is the only analysis method allowed. The same codes (such as NTC2008, EC8) consider the linear dynamic analysis with behavior factor as the reference method for the evaluation of seismic demand. This type of analysis is based on a linear-elastic structural model subject to a design spectrum, obtained by reducing the elastic spectrum through a behavior factor. The behavior factor (reduction factor or q factor in some codes) is used to reduce the elastic spectrum ordinate or the forces obtained from a linear analysis in order to take into account the non-linear structural capacities. The behavior factors should be defined based on several parameters that influence the seismic nonlinear capacity, such as mechanical materials characteristics, structural system, irregularity and design procedures. In practical applications, there is still an evident lack of detailed rules and accurate behavior factor values adequate for existing buildings. In this work, some investigations of the seismic capacity of the main existing RC-MRF building types have been carried out. In order to make a correct evaluation of the seismic force demand, actual behavior factor values coherent with force based seismic safety assessment procedure have been proposed and compared with the values reported in the Italian seismic code, NTC08. [ABSTRACT FROM AUTHOR]

The nonlinear static method of analysis has become the most popular tool for the seismic assessment of existing buildings. However, seismic codes do not allow its use for in-plan irregular buildings because it does not provide accurate predictions of the deck rotation. To overcome this limitation, the 'corrective eccentricity method' evaluates the maximum seismic response as the envelope of the results of two nonlinear static analyses. In these analyses, the lateral force is applied with two different (corrective) eccentricities with respect to the centre of mass of the deck. The corrective eccentricities were calibrated on single-storey systems with unidirectional resisting elements, i.e. with elements that are representative of walls or braced frames. This paper proposes new corrective eccentricities aiming at generalizing and simplifying the previous corrective eccentricity method. In particular, new equations are defined for the corrective eccentricities devoted to predict the displacement demand on the stiff side of the building. These equations are defined based on the response of a set of single-storey systems representative of buildings with uni-directional or bi-directional resisting elements (e.g. moment resisting frames). Further, the displacement demand on the flexible side of the building is determined assuming a null eccentricity of the lateral force. The response of a set of multi-storey buildings is predicted by means of the new and original corrective eccentricities and compared to the maximum response obtained by nonlinear dynamic analysis. This comparison is made in terms of floor displacements, storey drifts and storey shears. The set of the examined structural systems comprises buildings with steel braced structure as well as buildings with r.c. framed structure. [ABSTRACT FROM AUTHOR]

This paper offers a parametric study on reinforced concrete frames representative of structural types widely present in the European building stock. It focuses on buildings which have been designed only for vertical loads. These are detailed by adopting the simulated design procedure proposed in Masi (Bull Earthq Eng 1(3):371-395, 2003) and introduced in the European code for the seismic assessment and retrofitting of existing buildings EC8-3 (CEN in Eurocode 8: design of structures for earthquake resistance-part 3: assessment and retrofitting of buildings, prEN 1998-3, Brussels, 2005). Some structural types have been selected by varying the numbers of storeys (2, 4 and 8 storeys) and the infill configuration (bare, infilled and pilotis frames). The seismic analyses have been carried out applying linear and non-linear static analysis methods in accordance to EC8-3. Different performances were computed by adopting different seismic intensities (4 cases: very low to high seismic zone), behaviour factors (4 cases, only for linear analysis), knowledge levels (3 cases), and concrete strength values (3 cases: 10, 18 and 28 MPa). The performances were compared to investigate the consistency of the analysis methods under study that is to verify whether they provided results which were mutually consistent in terms of outcomes regarding safety verifications taking into account differences in complexity and accuracy. The role of some structural parameters is emphasized and future developments of the study aimed at upgrading the current version of the European code are outlined. [ABSTRACT FROM AUTHOR]

Developing earthquake scenarios for cities in areas with a moderate seismicity is a challenge due to the limited amount of available data, which is a source of large uncertainties. This concerns both the seismic hazard, for which only recordings for small earthquakes are available and the unknown earthquake resistance of the majority of structures not designed for seismic loading. The goal of the present study is to develop coherent probabilistic mechanics-based scenarios for a mid-size building stock including a comprehensive analysis of the uncertainties. As an application, a loss assessment for the school buildings of the city of Basel is performed for different scenarios of historical significance, such as the 1356 event, and from the deaggregation of the Swiss Probabilistic Seismic Hazard Model of 2015. The hazard part of the computations (i.e. ground motion estimation) is based on this model, a regional microzonation and recordings of small earthquakes on a dense strong motion network to compute site-amplification factors. The school buildings, which are mainly unreinforced masonry or reinforced concrete shear wall buildings, have been classified according to a specifically developed taxonomy. Fragility curves have been developed using non-linear static procedures and subsequently, vulnerability curves in terms of human and financial losses are proposed. The computations have been run with the OpenQuake engine, carefully propagating all the recognized uncertainties. Scenarios before and after retrofitting measures show their impact on the earthquake safety. A sensitivity analysis shows that the largest uncertainties come from the ground motion prediction although an improvement of all parts of the model is necessary to decrease the uncertainties. Although improved data and models are still necessary to be developed, probabilistic mechanics-based models outperform the capabilities of deterministic and/or empirical models for retrieving realistic earthquake loss distributions. [ABSTRACT FROM AUTHOR]

This paper addresses seismic vulnerability assessment at an urban scale and more specifically the capacity curves involved for building damage prediction. Standard capacity curves are a function of predefined building typology and are proposed in the Risk-UE LM2 method for computation of the corresponding damage grades. However, these capacity curves have been mainly developed for building stock of southern European cities and the accuracy of their application with different building features, such as the ones of cities of northern Europe should be assessed. A recent research project of seismic scenarios for the cities of Sion and Martigny in Switzerland provided the opportunity to check the capacity curves of Risk-UE LM2 method. Within the framework of this project, a detailed analysis was achieved for more than 500 buildings. These buildings were typical Swiss buildings and were composed of both unreinforced masonry buildings with stiff floors and reinforced concrete buildings. The construction drawings of each building were collected in order to have the most accurate information about their main structural characteristics. The typological classification that has been adopted was developed in a recent research project. Based on the individual features of the buildings, individual capacity curves were defined. Results of the seismic assessment applied to the 500 buildings compare very well with those obtained by using Risk-UE LM2 method for unreinforced masonry buildings with stiff floors. A slight improvement may be proposed for buildings with three stories through their introduction to the category of low-rise instead of mid-rise buildings. By contrast, accuracy for reinforced concrete buildings with shear walls is very poor. Damage prediction using related capacity curves of Risk-UE LM2 method does not correspond to reality. Prediction is too pessimistic and moreover damage grades increase with the height category (low-rise, mid-rise and high-rise) of these buildings which is in contradiction with the observed damages for this type of buildings. Improvements are proposed to increase the accuracy of the seismic vulnerability assessment for northern European building stock. For unreinforced masonry buildings, a slight modification of the limits of the height category of buildings using the ones defined for RC buildings improves the damage prediction. For reinforced concrete buildings with shear walls improved capacity curves derived from the typological curves of the specific typology C are proposed. [ABSTRACT FROM AUTHOR]

A proper assumption of the concrete strength is essential to model existing RC structures; their seismic performance, in fact, can be affected by the poor quality of materials, both in terms of low strength and high variability. This paper considers the effects of the variability of concrete strength within buildings. Due to the high variability of concrete strength, in fact, buildings can experience irregular seismic responses, both in plan and in elevation. This research investigates the effects of irregularity in elevation due to the strength variability of concrete in a case study, namely a four-storey RC framed building, designed for vertical loads only. The variability of the concrete strength has been evaluated on the basis of an extensive survey carried out by the REGIONE TOSCANA (Tuscany Regional Government) on a large sample of RC framed buildings. Special attention has been paid to the adequacy of current codes provisions (Eurocodes, FEMA) on how to quantify concrete strength. [ABSTRACT FROM AUTHOR]

comprehensive study is presented for empirical seismic vulnerability assessment of typical structural types, representative of the building stock of Southern Europe, based on a large set of damage statistics. The observational database was obtained from post-earthquake surveys carried out in the area struck by the September 7, 1999 Athens earthquake. After analysis of the collected observational data, a unified damage database has been created which comprises 180,945 damaged buildings from/after the near-field area of the earthquake. The damaged buildings are classified in specific structural types, according to the materials, seismic codes and construction techniques in Southern Europe. The seismic demand is described in terms of both the regional macroseismic intensity and the ratio α/ a, where α is the maximum peak ground acceleration (PGA) of the earthquake event and a is the unique value PGA that characterizes each municipality shown on the Greek hazard map. The relative and cumulative frequencies of the different damage states for each structural type and each intensity level are computed in terms of damage ratio. Damage probability matrices (DPMs) and vulnerability curves are obtained for specific structural types. A comparison analysis is fulfilled between the produced and the existing vulnerability models. [ABSTRACT FROM AUTHOR]

The seismic vulnerability of some frame structures, typical of existing Reinforced Concrete buildings designed only to vertical loads, has been evaluated. They are representative of building types widely present in the Italian building stock of the last 30 years. A simulated design of the structures has been made with reference to the codes in force, the available handbooks and the current practice at the time of construction. The seismic response is calculated through non linear dynamic analyses with artificial and natural accelerograms. Three main types have been examined: bare frames, regularly infilled frames and pilotis frames. The results show a high vulnerability for the pilotis buildings: they can be assigned to the class B of the European Macroseismic Scale of 1998 (EMS98). On the contrary, a low vulnerability (class D of EMS98) can be attributed to the regularly infilled buildings: in this case collapse can be considered unlikely also with strong earthquakes. An intermediate seismic behavior is shown by buildings without infills, whose vulnerability can be placed between the classes B and C of EMS98. [ABSTRACT FROM AUTHOR]

Concise information is presented for the development of an effective vibratory method of sinking (extracting) sheet piling, which is based on results of investigations conducted by domestic scientists. Problems of rational vibropenetration of sheet piling near existing buildings with modern vibropenetrators, for example, the V-402 type, are examined; working conditions, which for a highly efficient process, make it possible to lower the level of vibrations of the adjacent ground to minimal values (and in a number of cases, to reduce it to zero) and, in this manner, ensure the safety of existing buildings and structures, are verified. [ABSTRACT FROM AUTHOR]