A Screening Methodology for the Identification of Critical Units in Major-Hazard Facilities Under Seismic Loading

The complexity of process industry and the consequences that Na-Tech events could produce in terms of damage to equipment, release of dangerous substances (flammable, toxic, or explosive), and environmental consequences have prompted the scientific community to focus on the development of efficient methodologies for Quantitative Seismic Risk Analysis (QsRA) of process plants. Several analytical and numerical methods have been proposed and validated through representative case studies. Nevertheless, the complexity of this matter makes their applicability difficult, especially when a rapid identification of the critical components of a plant is required, which may induce hazardous material release and thus severe consequences for the environment and the community. Accordingly, in this paper, a screening methodology is proposed for rapid identification of the most critical components of a major-hazard plant under seismic loading. It is based on a closed-form assessment of the probability of damage for all components, derived by using analytical representations of the seismic hazard curve and the fragility functions of the equipment involved. For this purpose, fragility curves currently available in the literature or derived by using low-fidelity models could be used for simplicity, whereas the parameters of the seismic hazard curve are estimated based on the regional seismicity. The representative damage states (DS) for each equipment typology are selected based on specific damage states/loss of containment (DS/LOC) matrices, which are used to individuate the most probable LOC events. The risk is then assessed based on the potential consequences of a LOC event, using a classical consequence analysis, typically adopted in risk analysis of hazardous plants. For this purpose, specific probability classes will be used. Finally, by associating the Probability Class Index (PI) with Consequence Index (CI), a Global Risk Index (GRI) is derived, which provides the severity of the scenario. This allows us to build a ranking of the most hazardous components of a process plant by using a proper risk matrix. The applicability of the method is shown through a representative case study.

Hazard characterization for alternative intensity measures using the total probability theorem

Since their inception in the 1980s, simplified procedures for the analysis of liquefaction hazards have typically characterized seismic loading using a combination of peak ground acceleration and earthquake magnitude. However, more recent studies suggest that certain evolutionary intensity measures (IMs) such as Arias intensity or cumulative absolute velocity may be more efficient and sufficient predictors of liquefaction triggering and its consequences. Despite this advantage, widespread hazard characterizations for evolutionary IMs are not yet feasible due to a relatively incomplete representation of the ground motion models (GMMs) needed for probabilistic seismic hazard analysis (PSHA). Without widely available hazard curves for evolutionary IMs, current design codes often rely on spectral targets for ground motion selection and scaling, which are shown in this study to indirectly result in low precision of evolutionary IMs often associated with liquefaction hazards. This study presents a method to calculate hazard curves for arbitrary intensity measures, such as evolutionary IMs for liquefaction hazard analyses, without requiring an existing GMM. The method involves the conversion of a known IM hazard curve into an alternative IM hazard curve using the total probability theorem. The effectiveness of the method is illustrated by comparing hazard curves calculated using the total probability theorem to the results of a PSHA to demonstrate that the proposed method does not result in additional uncertainty under idealized conditions and provides a range of possible hazard values under most practical conditions. The total probability theorem method can be utilized by practitioners and researchers to select ground motion time series that target alternative IMs for liquefaction hazard analyses or other geotechnical applications. This method also allows researchers to investigate the efficiency, sufficiency, and predictability of new, alternative IMs without necessarily requiring GMMs.

Analysis of Exponent K Based on “Share” Project Data and Its Implications on Importance Factors of En 1998-1

This paper deals with seismic activity represented by a hazard curve through a single parameter – exponent k as given in EN 1998-1, as well as with its implications on importance factors. We have used the SHARE project dataset for calculation of exponent k for the wider European area and limited number of separate national studies for comparison of results since comparison to the SHARE results on the same dataset resulted with values of exponent k smaller by 1–1.5. The results indicate that recommended value of exponent k of 3 is rather an exception than expected value in seismically active regions, and that with the exclusion of Vrancea zone, for majority of Europe exponent k is well below assumed in EN 1998-1, which consequently indicate that importance factors for these locations should be larger than recommended in EN 1998-1.

Record-to-record variability and code-compatible seismic safety-checking with limited number of records

The Italian code requires spectrum compatibility with mean spectrum for a suite of accelerograms selected for time-history analysis. Although these requirements define minimum acceptability criteria, it is likely that code-based non-linear dynamic analysis is going to be done based on limited number of records. Performance-based safety-checking provides formal basis for addressing the record-to-record variability and the epistemic uncertainties due to limited number of records and in the estimation of the seismic hazard curve. “Cloud Analysis” is a non-linear time-history analysis procedure that employs the structural response to un-scaled ground motion records and can be directly implemented in performance-based safety-checking. This paper interprets the code-based provisions in a performance-based key and applies further restrictions to spectrum-compatible record selection aiming to implement Cloud Analysis. It is shown that, by multiplying a closed-form coefficient, code-based safety ratio could be transformed into simplified performance-based safety ratio. It is shown that, as a proof of concept, if the partial safety factors in the code are set to unity, this coefficient is going to be on average slightly larger than unity. The paper provides the basis for propagating the epistemic uncertainties due to limited sample size and in the seismic hazard curve to the performance-based safety ratio both in a rigorous and simplified manner. If epistemic uncertainties are considered, the average code-based safety checking could end up being unconservative with respect to performance-based procedures when the number of records is small. However, it is shown that performance-based safety checking is possible with no extra structural analyses.

The longitudinal risk of mortality between invasive ductal carcinoma and metaplastic breast carcinoma

The management of metaplastic breast carcinoma (MBC) has largely paralleled the paradigms used for invasive ductal carcinoma (IDC) in the current National Comprehensive Cancer Network guidelines of breast cancer. However, patients with IDC and MBC have been shown to have a different prognosis, and there are significant differences in risk and failure patterns after treatment. The purpose of this study was to compare breast cancer specific survival (BCSS) and hazard function between IDC and MBC. We included patients from the Surveillance, Epidemiology, and End Results program with stage I-III IDC and MBC between 2000 and 2012. Statistical analyses were including chi-square analysis, life-table methods, multivariate Cox proportional hazards models, and propensity score matching (PSM). We identified 294,719 patients; 293,199 patients with IDC and 1520 patients with MBC. Multivariate analyses showed that the MBC subtype had significantly lower BCSS than the IDC subtype before and after PSM (p < 0.001). There were significant differences in the hazard curve between IDC and MBC. The hazard curve for breast cancer mortality in the IDC cohort peaked at 3 years (2%), and then changed to a slowly decreasing plateau after prolonged follow up. However, the hazard curve for breast cancer mortality in the MBC cohort peaked at 2 years (7%), then declined sharply between 3 and 6 years, and changed to a low death rate after a follow-up time exceeding 6 years. Subgroup analyses revealed that the hazard curves significantly differed between IDC and MBC after stratifying by tumor stage and hormone receptor status. Our study suggests that patients with MBC should receive more effective systemic agents and intensive follow-up because of their significantly augmented risk of death compared to IDC patients.

Morbidities and mortality among infants of HIV-1-infected mothers with bacterial vaginosis in Kenya

Background: This study aimed to assess the effects of maternal bacterial vaginosis (BV) on the morbidity and mortality of HIV-exposed infants of women enrolled in a randomized controlled trial (pre-dating antiretroviral therapy) at birth, 6 months, and 12 months. Methods: Four hundred and twenty-five HIV-positive pregnant women were enrolled in this trial and were categorized as exposed if they had a laboratory-based diagnosis of BV (Nugent method). We compared the morbidity and mortality of infants of the mothers at birth, 6 months, and 12 months. We assessed morbidities from the mother’s history and clinical examination during scheduled and non-scheduled visits. The data that were collected longitudinally were then analyzed via multiple logistic regression with the generalized estimating equation. An independent correlation structure was assumed to evaluate the specific morbidity risks to infants associated with exposure to BV. We used the Kaplan–Meier method to generate the cumulative hazard curve, to determine mortalities at different stages between the two groups. Overall, only data for 328 infants were complete and used in the analysis.Results: Data were available for 159 and 171 BV exposed and non-exposed mothers, respectively. Exposure to BV was not associated with any neonatal morbidity at birth, but was associated with adverse maternal condition (unadjusted odds ratio [OR], 2.93; 95% confidence interval [CI], 1.19–7.20, P=0.02) and maternal hospital admissions (unadjusted OR, 1.95; 95% CI, 1.08–3.51, P=0.02). At 6 months, infants of BV exposed mothers had higher odds of bloody stool (adjusted OR, 3.08; 95% CI, 1.11–10.00, P=0.04), dehydration (adjusted OR, 2.94; 95% CI, 1.44–6.37, P=0.01), vomiting (adjusted OR, 1.64; 95% CI, 1.06–2.56, P=0.03), and mouth ulcers (adjusted OR, 12.8; 95% CI, 2.27–241.21, P=0.02). At 12 months, exposure to BV was associated with dehydration (adjusted OR, 1.81; 95% CI, 1.05–3.19, P=0.03) and vomiting (adjusted OR, 1.39; 95% CI, 1.01–1.92, P=0.04). Kaplan­–Meier survival analysis showed no association of BV with infant mortality (P=0.65); however, the cumulative hazard curve showed a higher trend toward deaths among BV exposed infants.Conclusion: Our findings demonstrate that BV is a good predictor of maternal and infant morbidities. Infants of both HIV and BV exposed mothers can manifest these symptoms at any stage within a year of growth. Adverse maternal condition and hospitalization of mothers after birth could indicate exposure to BV. Bloody stool, dehydration, vomiting, and mouth ulcers could indicate exposure to BV among infants.

Liquefaction assessment based on CSR-hazard curve through empirical procedure

&lt;p&gt;Semi-empirical procedures for evaluating liquefaction potential (e.g. Seed &amp; Idriss, 1971) require the estimation of cyclic resistance ratio (CRR) and cyclic shear stress ratio (CSR). The first can be obtained using empirical relationships based on in situ tests (e.g. CPT, SPT), the latter can be expressed as function of the maximum horizontal acceleration at ground surface (a&lt;sub&gt;max&lt;/sub&gt;), total and effective vertical stresses at the depth of interest (&amp;#963;&lt;sub&gt;v0&lt;/sub&gt;, &amp;#963;&amp;#8217;&lt;sub&gt;v0&lt;/sub&gt;) and a magnitude-dependent stress reduction coefficient (r&lt;sub&gt;d&lt;/sub&gt;) that accounts for the deformability of the soil column (Idriss &amp; Boulanger, 2004). All these methods were developed referring to a moment magnitude (M&lt;sub&gt;w&lt;/sub&gt;) equal to 7.5 and therefore require a magnitude scale factor (MSF) to make them suitable for different magnitude values. Usually, MSF and r&lt;sub&gt;d&lt;/sub&gt; are computed with reference to the mean or modal value of M&lt;sub&gt;w&lt;/sub&gt; taken from a disaggregation analysis, while a&lt;sub&gt;max&lt;/sub&gt; is obtained from a seismic hazard curve, including the contribution of various combinations of magnitudes and distances (Kramer &amp; Mayfield, 2005). Thus, there might be inconsistency between the magnitude values used to evaluate either MSF or r&lt;sub&gt;d&lt;/sub&gt; and a&lt;sub&gt;max&lt;/sub&gt;. To overcome this problem, Idriss (1985) suggests to directly introduce the MSF in the probabilistic hazard analysis of the seismic acceleration. In this contribution, an alternative method is proposed, by properly modifying the acceleration seismic hazard curve conventionally adopted by the code of practice on the basis the disaggregation analysis, so that i) the contribution of the different magnitudes and the associated MSF and r&lt;sub&gt;d&lt;/sub&gt;-values are considered, ii) the computational effort is reduced since a CSR-hazard curve is straightforward obtained. This alternative method is used to carry out a simplified liquefaction assessment of a sand deposit located in the municipality of Casamicciola Terme (Naples, Italy), where the results of SPT tests are available from recent seismic microzonation studies. The CSR computed using the proposed procedure is lower than that obtained adopting the classical method suggested by Idriss &amp; Boulanger (2004). This can be explained considering that the suggested method takes into account all the magnitudes that contribute to the definition of the seismic hazard, instead of considering the mean or modal value of the disaggregation analysis. Such an accurate prediction of the seismic demand may represent a basis for more reliable seismic microzonation maps for liquefaction and for a less conservative design of liquefaction risk mitigation measures.&lt;/p&gt;&lt;p&gt;References&lt;/p&gt;&lt;p&gt;Idriss, I.M. (1985). Evaluation of seismic risk in engineering practice, Proc. 11th Int. Conf. on Soil Mech. and Found. Engrg, 1, 255-320.&lt;/p&gt;&lt;p&gt;Idriss, I.M., Boulanger, R. W. (2004). Semi-Empirical Procedures for Evaluating Liquefaction Potential During Earthquakes, Proceedings of the 11th ICSDEE &amp; 3rd ICEGE, (Doolin et al. Eds.), Berkeley, CA, USA, 1, 32-56.&lt;/p&gt;&lt;p&gt;Kramer, S.L., Mayfield, R.T. (2005) Performance-based Liquefaction Hazard Evaluation, Proceedings of the Geo-Frontiers Congress, January 24-26, Austin, Texas, USA.&lt;/p&gt;&lt;p&gt;Seed H.B., Idriss M. (1971). Simplified procedure for evaluating soil liquefaction potential, J. Soil Mech. Found. Div., 97, 1249-1273.&lt;/p&gt;

Integration of Site Effects into Probabilistic Seismic Hazard Assessment (PSHA): A Comparison between Two Fully Probabilistic Methods on the Euroseistest Site

The integration of site effects into Probabilistic Seismic Hazard Assessment (PSHA) is still an open issue within the seismic hazard community. Several approaches have been proposed varying from deterministic to fully probabilistic, through hybrid (probabilistic-deterministic) approaches. The present study compares the hazard curves that have been obtained for a thick, soft non-linear site with two different fully probabilistic, site-specific seismic hazard methods: (1) The analytical approximation of the full convolution method (AM) proposed by Bazzurro and Cornell 2004a,b and (2) what we call the Full Probabilistic Stochastic Method (SM). The AM computes the site-specific hazard curve on soil, HC(Sas(f)), by convolving for each oscillator frequency the bedrock hazard curve, HC(Sar(f)), with a simplified representation of the probability distribution of the amplification function, AF(f), at the considered site The SM hazard curve is built from stochastic time histories on soil or rock corresponding to a representative, long enough synthetic catalog of seismic events. This comparison is performed for the example case of the Euroseistest site near Thessaloniki (Greece). For this purpose, we generate a long synthetic earthquake catalog, we calculate synthetic time histories on rock with the stochastic point source approach, and then scale them using an adhoc frequency-dependent correction factor to fit the specific rock target hazard. We then propagate the rock stochastic time histories, from depth to surface using two different one-dimensional (1D) numerical site response analyses, while using an equivalent-linear (EL) and a non-linear (NL) code to account for code-to-code variability. Lastly, we compute the probability distribution of the non-linear site amplification function, AF(f), for both site response analyses, and derive the site-specific hazard curve with both AM and SM methods, to account for method-to-method variability. The code-to-code variability (EL and NL) is found to be significant, providing a much larger contribution to the uncertainty in hazard estimates, than the method-to-method variability: AM and SM results are found comparable whenever simultaneously applicable. However, the AM method is also shown to exhibit severe limitations in the case of strong non-linearity, leading to ground motion “saturation”, so that finally the SM method is to be preferred, despite its much higher computational price. Finally, we encourage the use of ground-motion simulations to integrate site effects into PSHA, since models with different levels of complexity can be included (e.g., point source, extended source, 1D, two-dimensional (2D), and three-dimensional (3D) site response analysis, kappa effect, hard rock …), and the corresponding variability of the site response can be quantified.

ANALISA KURVA HAZARD PADA KABUPATEN TAMBRAUW DENGAN MENGGUNAKAN BEBERAPA FUNGSI ATENUASI

Kabupaten Tambrauw adalah salah satu kabupaten di Provinsi Papua Barat, Indonesia. Pusat pemerintahan berada di Fef. Kabupaten Tambrauw mempunyai luas wilayah 11 529,19 Km², yang terdiri dari daratan dan lautan. Secara geografis Kabupaten Tambrauw pada sebelah Utara berbatasan dengan Samudera Pasifik, sebelah Selatan berbatasan dengan Kabupaten Sorong Selatan dan sebelah Timur berbatasan dengan Distrik Sidey dan Kabupaten Manokwari. Ada beberapa metode yang dapat digunakan dalam Seismic Hazard Assessment untuk membuat prediksi kejadian gempa di masa yang akan datang (gempa rencana). Pada analisa ini, Seismic Hazard Assessment menggunakan The Line Source Method untuk membuat Hazard curve yang dapat memperkirakan kejadian gempa di Kabupaten Tambrauw. Kurva hazard dibuat menggunakan fungsi atenuasi Esteva (1970), fungsi Atenuasi Hou &amp; Hu (1991), fungsi Atenuasi Ambraseys (1995) dan fungsi Atenuasi Crouse-Mc Guirre (1996). Hasil analisa menunjukkan besarnya nilai percepatan tanah (ground acceleration) akan semakin mengecil pada jarak atau radius yang semakin jauh. Analisis kurva hazard pada daerah Kabupaten Tambrauw akibat pergeseran lempeng akan menunjukkan nilai terbesar pada saat menggunakan fungsi atenuasi Hou &amp; Hu (1991) dan analisis kurva hazard pada daerah Kabupaten Tambrauw akibat pergeseran lempeng akan menunjukkan nilai terkecil pada saat menggunakan fungsi atenuasi Crouse-McGuirre (1996), F = 0.