A loophole in the Eurocode 8 allowing for non-conservative seismic design

Paglietti, A.; Porcu, Maria Cristina; Pittaluga, Marco

doi:10.1016/j.engstruct.2010.12.001

Cited by 4 publications

(3 citation statements)

References 12 publications

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“…This result contrasts with the fact that, being more simpler (and less reliable) the MRSA should be more conservative than the NLTHA (similar concerns are discussed in Ref. [12]). It is to note that the response of the two plastic-hinge models is very similar under less violent events (Suites 2 and 4), while it may largely differ under stronger earthquakes (Suites 1 and 3).…”

Section: Convergence Problems and Extra Ductility Demandcontrasting

confidence: 50%

Code inadequacies discouraging the earthquake-based seismic analysis of buildings

Porcu¹

2017

Int. J. SAFE

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Despite being the more accurate method to design earthquake-resistant buildings, the non-linear dynamic analysis still remains the least used in practice. The paper shows that some code inadequacies may even contribute to ward off the designer from this kind of seismic analysis. To this purpose, non-linear analyses under different sets of spectrum-compatible earthquakes and by considering two distinct plastic-hinge models were carried out for a multistory reinforced concrete (r/c) frame designed according to the Eurocode 8 provisions. It has been shown that owing to the inadequate limits imposed to the spectrum-compatible earthquakes, the European codes of practice may lead to significant inconsistencies in the seismic design of structures through the time-history non-linear analysis. Keywords: earthquake-resistant buildings, EC8 inadequacies, spectrum-compatible earthquakes, time-history non-linear seismic analysis. INTRODUCTIONThe seismic design philosophy typically requires that buildings may withstand events of moderate severity deforming in the elastic range, without suffering any irreversible structural damage. Conversely, during strong earthquakes structures are required to behave in a dissipative ductile way, even getting damaged severely but without collapsing. These achievements have to be reached regardless to which type of code-based analysis (linear or non-linear) is chosen. If a linear analysis is performed, in fact, a reduced response spectrum can be adopted to design the structure so as it can withstand moderate earthquakes in the elastic range, while compliance with the detailed code provisions (local ductility and strength hierarchy rules) ensure that the plastic deformation capacity of the system can satisfy the demand under stronger earthquakes. If a non-linear analysis is carried out instead, the elastic and postelastic behaviour of the structure can be straight monitored. Both a non-linear static analysis (often referred to as 'pushover') and a non-linear time-history analysis (NLTHA) are allowed by codes. The latter is expected to be the more powerful since it obtains the deformation time-history of the system through a numerical integration of the differential equations of motion under the considered earthquake.Despite its indubitable potentials, the NLTHA is still the least applied method of seismic analysis. This may be due to the difficulties that even an experienced designer has to overcome when (i) modelling the non-linear behaviour of the system, (ii) defining the suite of spectrum-compatible earthquakes, (iii) carrying out the numerical calculations and even (iv) interpreting the results and choosing the requirements to be met. To help the designer, some codes of practice, i.e. FEMA-356 [1] and ATC-40 [2], give default properties for r/c plastic hinges, which are implemented by finite element structural programs such as SAP2000 [3]. User-friendly software tools, as for instance REXEL [4], are also available to obtain code-based selections of accelerograms.Nevertheless, the ...

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Section: Convergence Problems and Extra Ductility Demandcontrasting

confidence: 50%

Code inadequacies discouraging the earthquake-based seismic analysis of buildings

Porcu¹

2017

Int. J. SAFE

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“…An effective and energy-saving time-window could be defined by choosing the lowest time value and the highest time value of the two time-windows found through the Arias intensity procedure, see Figure 10d. Eventually the full-length accelerograms of Figure 10a are reduced to those shown in Figure 10e which are saving 95% of the earthquake energy, while being shortened to about 1 4 of the full length. It is noted, in fact, that saving almost all the energy of the original ground motion is of paramount importance since the effects of ground motions on structures are strongly related to the energy input [54].…”

Section: Short-length Energy-saving Accelerograms For Numerical Analysesmentioning

confidence: 99%

“…Seismic methods may also be linear or non-linear, depending on whether the structural material is modelled through a linear-elastic or an elastic-plastic behavior. The simplest method proposed by codes is the linear-static one, which applies a pattern of static loads proportional to the masses and to the DRS accelerations; it generally gives less accurate results [1]. The non-linear-static method (also known as Pushover Analysis) applies a pattern of increasing static loads to the structure until targeted inelastic displacement levels are reached [2].…”

Section: Introductionmentioning

confidence: 99%

A Contribution to Facilitate the Seismic Design in Lebanon Using Short-Length Spectrum-Consistent Earthquakes

Gerges,

Porcu,

Vielma Pérez

2023

Applied Sciences

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Seismic regulations of developing countries are often grounded on rules of more experienced countries. The Lebanese regulations refer to four foreign codes, this excess of guidelines generating confusion and conflicting design choices. Moreover, the scarcity of earthquakes recorded in the Lebanese area makes it difficult to obtain suitable sets of spectrum-consistent accelerograms for dynamic analyses. Sorting through the reference regulations and the indications for their local application, this paper derives and compares all the design response spectra allowed by the Lebanese code. Consistent with the design response spectra of the two codes that are still in force (of the four referred to), some suites of spectrum-consistent accelerograms are derived. Based on the Arias intensity, a general procedure is also proposed to reduce the time duration of the accelerograms, while saving the earthquake energy content and, thus, the reliability of the results. Full-length and short-length spectrum-consistent accelerograms are thus made available for the Lebanese design. With reference to a two-dimensional model some comparisons between response-spectrum-based and earthquake-based analyses are provided, which showed that the Lebanese code allows different safety levels for earthquake-resistant buildings. The paper provides a very useful contribution to researchers and designers that are involved in the protection of the Lebanese building heritage from seismic hazards, and it also provides data and tools that can be more generally exploited in other seismic areas.

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