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1.
A comparison of seismic risk maps for Italy 总被引：5，自引：3，他引：2
Helen Crowley Miriam Colombi Barbara Borzi Marta Faravelli Mauro Onida Manuel Lopez Diego Polli Fabrizio Meroni Rui Pinho 《Bulletin of Earthquake Engineering》2009,7(1):149-180
National seismic risk maps are an important risk mitigation tool as they can be used for the prioritization of regions within
a country where retrofitting of the building stock or other risk mitigation measures should take place. The production of
a seismic risk map involves the convolution of seismic hazard data, vulnerability predictions for the building stock and exposure
data. The seismic risk maps produced in Italy over the past 10 years are compared in this paper with recent proposals for
seismic risk maps based on state-of-the-art seismic hazard data and mechanics-based vulnerability assessment procedures. The
aim of the paper is to open the discussion for the way in which future seismic risk maps could be produced, making use of
the most up-to-date information in the fields of seismic hazard evaluation and vulnerability assessment. 相似文献
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A principal aspect of seismic design is the verification of performance limit states, which help ensure satisfactory behaviour within a performance-based earthquake engineering framework. However, it is increasingly acknowledged that while ensuring life safety is a suitable basic design requirement, more meaningful metrics of seismic performance exist. Expected annual loss (EAL) has gained attention in recent years but tends to be limited to seismic assessment. This article proposes a novel conceptual design framework that employs EAL as a design tool and requires very little building information at the design outset. This means that designers may commence from a definition of required EAL and arrive at a number of feasible structural solutions without the need for any detailed design calculations or numerical analysis. This works by transforming the building performance definition to a design solution space using a number of simplifying assumptions. A suitable structural response backbone is subsequently determined and used to identify feasible building typologies and associated structural geometries. The assumptions made to implement such a conceptual design framework are discussed and justified herein followed by a case study application. This proposed design framework is intended to form the first step in seismic design to identify suitable typologies and layouts before subsequent member detailing and design verification. This way, engineers, architects, and clients can make more informed decisions that target certain performance goals at the beginning of design before further refinement. 相似文献
4.
Donatello Cardone Timothy Sullivan Giuseppe Gesualdi Giuseppe Perrone 《地震工程与结构动力学》2017,46(12):2009-2032
Performance‐based earthquake engineering procedures have now developed to the point that it is possible to evaluate a range of possible decision variables, including the expected annual monetary loss (EAL). Quantification of the EAL is considered to be particularly useful because it could assist with the identification of effective design and retrofit measures that consider seismic performance over a range of intensity levels. Recognizing, however, that existing procedures for the evaluation of EAL tends to be quite time consuming, this paper builds on a recent proposal to use simplified limit state loss versus intensity relationships to compute EAL via a closed‐form equation, without the need to compile an inventory of damageable components and with freedom in the choice of structural analysis method. Various developments to the simplified approach are made in this paper to allow consideration of loss thresholds, non‐uniform damage distributions and the impact of differences in seismic performance in orthogonal directions. In addition, means of accounting for uncertainties in the simplified EAL assessment are described. The work has focused on the assessment of EAL for reinforced concrete frame buildings with details representative of construction practice adopted in Italy in the 1950s through to the early 1970s. By comparing loss assessment results obtained using a refined methodology with those obtained using the new guidelines developed here for two case study buildings, it is concluded that the simplified approach works well. Future research should therefore aim to further validate the approach and extend it to other building typologies and construction eras. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
5.
This study describes the seismic performance of an existing five storey reinforced concrete building which represents the typical properties of low-rise non-ductile buildings in Turkey. The effectiveness of shear walls and the steel bracings in retrofitting the building was examined through nonlinear static and dynamic analyses. By using the nonlinear static analysis, retrofitted buildings seismic performances under lateral seismic load were compared with each other. Moreover, the performance points and response levels of the existing and retrofitting cases were determined by way of the capacity-spectrum method described in ATC-40 (1996). For the nonlinear dynamic analysis the records were selected torepresent wide ranges of duration and frequency content. Considering the change in the stiffness and the energy dissipation capacities, the performance of the existing and retrofitted buildings were evaluated in terms of story drifts and damage states. It was found that each earthquake record exhibited its own peculiarities, dictated by frequency content, duration, sequence of peaks and their amplitude. The seismic performance of retrofitted buildings resulted in lower displacements and higher energy dissipation capacity depending mainly on the properties of the ground motions and the retrofitting strategies. Moreover, severe structural damage (irreparable or collapse) was observed for the existing building. However, buildings with retrofit alternatives exhibited lower damage levels changing from no damage to irreparable damage states. 相似文献
6.
Existing buildings can be at a greater seismic risk due to non-conformance to current design codes and may require structural retrofitting to improve building performance. The performance of buildings is measured in terms of immediate consequences due to direct damage, but the continuing impacts related to recovery are not considered in seismic retrofit assessment. This paper introduces a framework of retrofit selection based on the seismic resilience of deficient buildings retrofitted with the conventional mitigation approaches. The assembly-based methodology is considered for the seismic resilience assessment by compiling a nonlinear numerical model and a building performance model. The collapse fragility is developed from the capacity curve, and the resulting social, economic, and environmental consequences are determined. The seismic resilience of a building is assessed by developing a downtime assessment methodology incorporating sequence of repairs, impeding factors, and utility availability. Five functionality states are developed for the building functionality given investigated time interval, and a functionality curve for each retrofit is determined. It is concluded that seismic resilience can be used as a performance indicator to assess the continuing impacts of a hazard for the retrofit selection. 相似文献
7.
Based on performance-based seismic engineering, this paper proposes an optimal seismic retrofit model for steel moment resisting frames (SMRFs) to generate a retrofit scheme at minimal cost. To satisfy the acceptance criteria for the Basic Safety Objective (BSO) specified in FEMA 356, the minimum number of upgraded connections and their locations in an SMRF with brittle connections are determined by evolutionary computation. The performance of the proposed optimal retrofitting model is evaluated on the basis of the energy dissipation capacities, peak roof drift ratios, and maximum interstory drift ratios of structures before and after retrofitting. In addition, a retrofit efficiency index, which is defined as the ratio of the increment in seismic performance to the required retrofitting cost, is proposed to examine the efficiencies of the retrofit schemes derived from the model. The optimal seismic retrofit model is applied to the SAC benchmark examples for threestory and nine-story SMRFs with brittle connections. Using the retrofit efficiency index proposed in this study, the optimal retrofit schemes obtained from the model are found to be efficient for both examples in terms of energy dissipation capacity, roof drift ratio, and maximum inter-story drift ratio. 相似文献
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以山西G市为例，通过对该市建筑物造价、建筑物室内财产、各乡镇经济收入、县乡企业经济等情况进行的调查，对该市进行了直接和间接经济损失预测，从而给出总经济损失预测结果。在建筑物震害预测的基础上，给出不同破坏烈度下预测区的死亡人数、无家可归人数的预测结果，指出预测未来地震灾害的经济损失和人员伤亡是把握当今社会经济布局和未来灾害损失程度、科学制定防震减灾对策的重要环节之一。 相似文献
9.
Edoardo Cosenza Ciro Del Vecchio Marco Di Ludovico Mauro Dolce Claudio Moroni Andrea Prota Emanuele Renzi 《Bulletin of Earthquake Engineering》2018,16(12):5905-5935
The Italian “Guidelines for the seismic risk classification of constructions” approved in February 2017 define the technical principles for exploiting tax deductions with respect to seismic strengthening interventions on existing buildings (Sismabonus). Tax deductions represent a unique opportunity to improve the seismic safety of the existing Italian building stock. The guidelines are very simple and allow practitioners to deal with the sophisticated concepts behind modern seismic design, such as expected annual losses (EAL) and repair costs (expressed as a fraction of the Reconstruction Cost: %RC). The seismic risk classes of buildings and the class upgrade due to strengthening interventions can be assessed using the principles included in the guidelines. The seismic risk class is the minimum between the class defined by the building safety index at the ultimate limit state and the one related to the EAL. The latter class depends on the area under the curve of the expected losses, which is easily obtained by computing the safety index converted in the return period (annual frequency) at different limit states and the relevant %RC. This paper illustrates the technical principles at the base of the guidelines and the procedure used to calibrate the repair costs associated with the different limit states using the actual repair costs monitored in the reconstruction process following recent Italian earthquakes. Finally, simple tools to estimate the cost of the strengthening interventions to improve the seismic capacity at the life-safety limit states are provided. 相似文献
10.
Expected annual loss (EAL), which can be expressed in dollars, is an effective way of communicating the seismic vulnerability of constructed facilities to owners and insurers. A simplified method for estimating EAL without conducting time‐consuming non‐linear dynamic analyses is presented. Relationships between intensity measures and engineering demand parameters resulting from a pushover analysis and a modified capacity‐spectrum method are combined with epistemic and aleatory uncertainties to arrive at a probabilistic demand model. Damage measures are established to determine thresholds for damage states from which loss ratios can be defined. Financial implications due to damage can then be quantified in the form of EAL by integrating total losses for all likely earthquake scenarios. This rapid loss estimation method is verified through the computationally intensive incremental dynamic analysis, with the results processed using a distribution‐free methodology. To illustrate the application of the proposed method, the seismic vulnerability of two highway bridge piers is compared; one bridge is traditionally designed for ductility while the other is based on an emerging damage avoidance design (DAD) philosophy. The DAD pier is found to have a clear advantage over the conventional pier; the EAL of the DAD pier is less than 20% of its ductile counterpart. This is shown to be primarily due to its inherent damage‐free behaviour for small to medium earthquake intensities, whose contribution to EAL is significantly more than that of very rare events. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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The catastrophic nature of seismic risk resides in the fact that a group of structures and infrastructure is simultaneously
excited by spatially correlated seismic loads due to an earthquake. For this, both earthquake-to-earthquake (inter-event)
and site-to-site (intra-event) correlations associated with ground motion prediction equations must be taken into account
in assessing seismic hazard and risk at multiple sites. The consideration of spatial correlation of seismic demand affects
aggregate seismic losses as well as identified scenario seismic events. To investigate such effects quantitatively, a simulation-based
seismic risk model for spatially distributed structures is employed. Analysis results indicate that adequate treatment of
spatial correlation of seismic demand is essential and the probability distribution of aggregate seismic loss can be significantly
different from those based on the assumptions that seismic excitations are not correlated or fully correlated. Furthermore,
the results suggest that identified scenario events by deaggregation in terms of magnitude and distance become more extreme
if the spatial correlation is ignored. 相似文献
13.
This paper deals with the development of a procedure aimed at defining a seismic risk mitigation strategy for public buildings in terms of prioritization, time required and funds. The procedure is based on a global risk index involving the entire building stock under study thus facilitating an examination of risk variation over time up to its final value. Relationships between the current seismic capacity–demand ratios and the required strengthening costs (cost models) have been developed. Each of the assumed cost models has a different target in terms of capacity–demand ratio to be obtained after strengthening, basically ranging between full retrofit and upgrading. The procedure has been applied to 69 hospital buildings located in Basilicata region for which the vulnerability data was available as a result of a large assessment program set up by the regional government. Priorities have been defined on the basis of seismic capacity, local hazard and number of human beings possibly involved (exposure). The results of different strengthening strategies have been outlined with a special focus on the pros and cons of the upgrading strategy with respect to various retrofit strategies. The procedure may be applied to different categories of public buildings by properly modifying some input parameters and partially redefining criteria for prioritization. 相似文献
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This paper assesses the seismic performance of typical reinforced concrete (RC) existing framed structures designed for gravity loads only. The sample two-storey structural system exhibits high vulnerability, i.e. low lateral resistance and limited translation ductility; hence an effective strategy scheme for seismic retrofitting was deemed necessary. Such a scheme comprises buckling restrained braces (BRBs) placed along the perimeter frames of the multi-storey building. The adopted design approach assumes that the global response of the inelastic framed structure is the sum of the elastic frame (primary system) and the system comprising perimeter diagonal braces (secondary system); the latter braces absorb and dissipate a large amount of hysteretic energy under earthquake ground motions. Comprehensive nonlinear static (pushover) and dynamic (response history) analyses were carried out for both the as-built and retrofitted structures to investigate the efficiency of the adopted intervention strategy. A set of seven code-compliant natural earthquake records was selected and employed to perform inelastic response history analyses at serviceability (operational and damageability limit states, OLS and DLS) and ultimate limit states (life safety and collapse prevention limit states, LSLS and CPLS). Both global and local lateral displacements are notably reduced after the seismic retrofit of the existing system. In the as-built structure, the damage is primarily concentrated at the second floor (storey mechanism); the computed interstorey drifts are 2.43% at CPLS and 1.92% at LSLS for modal distribution of lateral forces. Conversely, for the retrofitted system, the estimated values of interstorey drifts (d/h) are halved; the maximum d/h are 0.84% at CPLS (along the Y-direction) and 0.65% at LSLS (yet along the Y-direction). The values of the global overstrength Ω vary between 2.14 and 2.54 for the retrofitted structure; similarly, the translation ductility μΔ-values range between 2.07 and 2.36. The response factor (R- or q-factor) is on average equal to 5.0. It is also found that, for the braced frame, under moderate-to-high magnitude earthquakes, the average period elongation is about 30%, while for the existing building the elongation is negligible (lower than 5%). The inelastic response of the existing structure is extremely limited. Conversely, BRBs are effective to enhance the ductility and energy dissipation of the sample as-built structural system. Extensive nonlinear dynamic analyses showed that more than 60% of input seismic energy is dissipated by the BRBs at ultimate limit states. The estimated maximum axial ductility of the braces is about 10; the latter value of translation ductility is compliant with BRBs available on the market. At DLS, the latter devices exhibit an elastic behaviour. It can thus be concluded that, under moderate and high magnitude earthquakes, the damage is concentrated in the added dampers and the response of the existing RC framed structure (bare frame) is chiefly elastic. 相似文献
16.
A risk‐based life cycle cost strategy for optimal design and evaluation of control methods for nonlinear structures 
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下载免费PDF全文 The lack of direct correspondence between control objectives and hazard risks over the lifetime of systems is a key shortcoming of current control techniques. This along with the inability to objectively analyze the benefits and costs of control solutions compared with conventional methods has hindered widespread application of control systems in seismic regions. To address these gaps, this paper offers 2 new contributions. First, it introduces risk‐based life cycle–cost (LCC) optimal control algorithms, where LCC is incorporated as the performance objective in the control design. Two strategies called risk‐based linear quadratic regulator and unconstrained risk‐based regulator are subsequently proposed. The considered costs include the initial cost of the structure and control system, LCC of maintenance, and probabilistically derived estimates of seismic‐induced repair costs and losses associated with downtime, injuries, and casualties throughout the life of the structure. This risk‐based framework accounts for uncertainties in both system properties and hazard excitations and uses outcrossing rate theory to estimate fragilities for various damage states. The second contribution of this work is a risk‐based probabilistic framework for LCC analysis of existing and proposed control strategies. The proposed control designs are applied to the nonlinear model of a 4‐story building subjected to seismic excitations. Results show that these control methods reduce the LCC of the structure significantly compared with the status quo option (benefits of up to $1 351 000). The advancements offered in this paper enhance the cost‐effectiveness of control systems and objectively showcase their benefits for risk‐informed decision making. 相似文献
17.
Deterministic Earthquake Scenarios for the City of Sofia 总被引：3，自引：0，他引：3
S. Slavov I. Paskaleva M. Kouteva F. Vaccari G. F. Panza 《Pure and Applied Geophysics》2004,161(5-6):1221-1237
— The city of Sofia is exposed to a high seismic risk. Macroseismic intensities in the range of VIII – X (MSK) can be expected in the city. The earthquakes that can influence the hazard in Sofia originate either beneath the city or are caused by seismic sources located within a radius of 40 km. The city of Sofia is also prone to the remote Vrancea seismic zone in Romania, and particularly vulnerable are the long-period elements of the built environment. The high seismic risk and the lack of instrumental recordings of the regional seismicity make the use of appropriate credible earthquake scenarios and ground-motion modelling approaches for defining the seismic input for the city of Sofia necessary. Complete synthetic seismic signals, due to several earthquake scenarios, were computed along chosen geological profiles crossing the city, applying a hybrid technique, which combines the modal summation technique and finite differences. The modelling takes into account simultaneously the geotechnical properties of the site, the position and geometry of the seismic source and the mechanical properties of the propagation medium. Acceleration, velocity and displacement time histories and related quantities of earthquake engineering interest (e.g., response spectra, ground-motion amplification along the profiles) have been supplied. The approach applied in this study allows us to obtain the definition of the seismic input at low cost, exploiting large quantities of existing data (e.g. geotechnical, geological, seismological). It may be efficiently used to estimate the ground motion for the purposes of microzonation, urban planning, retrofitting or insurance of the built environment, etc. 相似文献
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Upgrading noncode conforming buildings to mitigate seismic induced damages is important in moderate to high seismic hazard regions. The damage, can be mitigated by using conventional (e.g. FRP wrapping) and emerging (e.g. smart structures) retrofit techniques. A model for the structure to be retrofitted should include relevant performance indicators. This paper proposes a variable stiffness smart structure device known as the Smart Spring to be integrated on building structures to mitigate seismic induced damage. The variable stiffness capability is of importance to structures that exhibit vertical (e.g. soft storey) irregularities and to meet different performance levels under seismic excitation. To demonstrate the utility of the proposed retrofitting technique, a four‐storey steel building is modelled in MATLAB and appropriate performance indicators are chosen. Various return period seismic hazards are generated from past earthquake event records to predict the structure's performance. The performance improvement because of the retrofitting of building structures using the variable stiffness device is presented. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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A model for the regional hospitals system behaviour in case of a seismic event is developed. The aim is the evaluation of the vulnerability of the system as well as the selection of the best intervention strategy for the retrofitting of the hospitals so as to minimize the cost benefit ratio and to evaluate the effect of different post-earthquake emergency measures like the use of camp hospitals. The efficiency of the system is measured in terms of the mean distance to be cured for persons injured by the earthquake and by damages to the system. Some simplifying assumptions are used and discussed; these can be easily removed if necessary. Results allow to clearly indicate the most convenient interventions. © 1998 John Wiley & Sons, Ltd. 相似文献