Critical Comparison of Assessment Codes for Steel Moment Resisting Frames

Many existing steel multi-storey frame buildings worldwide were designed prior to the introduction of modern seismic design provisions or based on outdated hazard maps considering low values of seismic intensity. This often resulted in buildings showing low performances with respect to earthquake loads. Assessment codes, such as the Eurocode 8 Part 3 and the ASCE 41, have been conceived to provide tools to assess the seismic performance of existing structures, to evaluate their adequacy with respect to the current safety standards and the need for seismic retrofit. However, recent research studies have revealed the necessity for a revision of these codes. In particular, for steel moment resisting frames, the current European regulation shares many similarities with older versions of the American codes, but has failed to incorporate changes based on the state-of-the-art knowledge. In addition, the undergoing update of other parts of the Eurocode motivates a full revision of the current standards. This paper compares the assessment procedures of the European and American codes. Two low-code steel Moment Resisting Frames were considered for case study purposes and the assessment was performed based on three local Engineering Demand Parameters (EDPs), i.e., column’s rotation, beam’s rotation and panel zone’s shear distortion, and the inter-story drift as global EDP. Incremental Dynamic Analyses were performed for the development of component and system fragility curves. The present work aims to identify some challenges and to provide some preliminary insights for the revision of the Eurocode 8 Part 3

An intrusion and fault tolerant forensic storage for a SIEM system

Current Security Information and Events Management (SIEM) solutions lack a data storage facility which is secure enough - i.e. stored events related to security incidents cannot be forged and are always available - that it can be used for forensic purposes. Forensic storage used by current SIEM solutions uses traditional RSA algorithm to sign the security events. In this paper we have analyzed the limits of current forensic storages, and we have proposed an architecture for forensic storage, implementing a threshold-based variant of the RSA algorithm, that outperforms state of the art SIEM solutions in terms of intrusion- and fault-tolerance. We show by experiments that our forensic storage works correctly even in the presence of cyber-attacks, although with a performance penalty. We also conduct an experimental campaign to evaluate the performance cost of the proposed scheme as a function of the threshold

A resilient architecture for forensic storage of events in critical infrastructures

In Critical Infrastructures, forensic analysis of stored events is an essential task when a security breach occurs. The goal of forensic analysis is to provide evidence to be used as valid proofs in a legal proceeding. So, it is very important to ensure the integrity of the events stored in order to perform a correct forensic analysis. Today, most of the SIEMs used to protect the Critical Infrastructures sign the security events with RSA classic algorithm in order to ensure their integrity. The signed security events cannot be admissible as evidence if the secret key is compromised, or when the module responsible for signing operations is down for any reason. In this paper a new architecture that overcomes these limitations has been proposed. Experimental tests show the performance of our architecture and the high resilience in faulty situations, i.e. some nodes are under attack

Numerical analysis of potential failure modes in shear walls of the tunnel form concrete system: Performance-based approach

Similar to other structural systems, the nonlinear modeling process of the tunnel-form concrete system necessitates an understanding of the potential failure modes in its primary lateral load-bearing members. With the identification of failure modes in the elements, deformation-control actions, force-control actions and deformation parameters are determined, making the analysis/design process straightforward. Given the unique characteristics of the tunnel-form concrete system, the applicability of design requirements and assumptions proposed for other similar systems for this structural system remains uncertain. In this study, to assess the potential failure modes of the walls of the system, two different modeling scenarios were utilized, employing pushover and time-history analyses. Within the scope of the studied 5- and 10-story buildings and the adopted assumptions, the results revealed that in the walls, shear is controlled by deformation and bending is force-control. In the incremental analysis, the bending failure mode of the walls (reaching yielding in vertical rebars) was estimated to be almost 10% higher than that of the shear failure mode (achieving an immediate occupancy limit). In the time-history analysis, under the design hazard level (475-year return period), the shear strain in the walls exceeded 13 times the strain at the onset of nonlinear shear behavior. This is because the wall sections still retained sufficient flexural-axial capacity and, contrary to code-based predictions, remained far from the flexural failure mode. The investigations further demonstrated that shear failure in the system was sufficiently ductile and capable of adequately absorbing and dissipating seismic input energy

Seismic risk of critical facilities in the Dominican Republic: case study of school buildings

Abstract The island of Hispaniola, shared by the Dominican Republic and Haiti, is located in a subduction zone between the North America plate and the Caribbean plate. In addition, there are 13 geological faults in the interior of the island, some of which have shown the potential to generate earthquakes of magnitude 7.5 and higher. Thus, the whole island is considered to be a high seismic risk region. In the past 100 years, several earthquakes have affected both parts of the island. In the case of the Dominican Republic, two earthquakes stand out: a magnitude 8.1 earthquake on August 4, 1946, north of the Samaná Province, which caused a tsunami, soil liquefaction, and the loss of about 100 lives, and a magnitude 6.5 earthquake on September 22, 2003, in the city of Puerto Plata, which caused significant damage for infrastructures. Among the observed effects, the partial and total collapse of several school buildings had a remarkable impact on local communities. In addition to the high seismic risk, a large part of the national infrastructure may exhibit high vulnerability to earthquakes because the seismic regulations had been the same for 32 years, namely from 1979 to 2011. During these three decades, thousands of structures were built nationwide, including essential facilities such as hospitals and schools. Considering that the current student population in public schools in the Dominican Republic is over 2 million, with the majority attending buildings that were designed with the 1979 seismic code and which proved to be highly vulnerable during the Puerto Plata earthquake, it is vital to take measures that reduce the risk and minimize potential earthquake damage to school buildings. In this context, the Technological Institute of Santo Domingo (INTEC) has undertaken recently a project with the main objective to assess the seismic vulnerability of 22 schools located in the San Cristóbal Province, in the south of the Dominican Republic. The latter schools were all built prior to the adoption of the current updated seismic code. This paper presents the results of the assessment of the Fernando Cabral Ortega School. Although only the results of a single RC building are presented, the response of such structure can be considered representative of a portfolio of existing schools in Dominican Republic

Endovascular Stent Grafts as a Safe Secondary Option for Paraanastomotic Abdominal Aortic Aneurysm

Objective: To describe our experience of endovascular repair of paraanastomotic aortic aneurysm. Methods and results: From March 2001 to December 2004 we identified 6 patients with a paraanastomotic aortic aneurysms following previous open repair of abdominal aortic aneurysm. All patients were treated with endovascular surgery under epidural anaesthesia. There were no major complications, surgical conversions or deaths. Four patients received a bifurcated aortic stent-graft, and two an aorto-uniliac stent-graft followed by a femoro-femoral bypass. At follow-up (mean 26.1 ± 10.2 months) there were no deaths, endoleaks or graft migrations observed. Conclusion: Endovascular surgery, avoiding general anesthesia and re-laparotomy, is the ideal technique for treatment of this complication resulting from failed primary conventional AAA repair. © 2006 Elsevier Ltd. All rights reserved

Milk Thistle (Silybum Marianum L.) as a Novel Multipurpose Crop for Agriculture in Marginal Environments: A Review

Milk thistle (Silybum marianum (L.) Gaertn.) is a versatile crop that has adapted to the broadly different soil and environmental conditions throughout all continents. To date, the fruits (\u201cseeds\u201d) of the plant are the only reliable source of silymarin, which, given its recognized therapeutic effects and its many present and potential uses, has led to a significant re-discovery and enhancement of the crop in recent years. Overall, although many studies have been carried out globally on the bioactivity, phytochemistry, and genetics of milk thistle, few and discontinuous research activity has been conducted on its basic agronomy as well as on the farm opportunities offered by the cultivation of this species. However, the multiple potential uses of the plant and its reduced need for external inputs suggest that milk thistle can perfectly fit among the most interesting alternative crops, even for marginal environments. The growing interest in natural medicine, the increasing popularity of herbal dietary supplements, and the multiple possibilities for livestock feeding are all arguments supporting the idea that in many rural areas, this crop could represent a significant tool for enhancing and stabilizing farm income. However, several issues still have to be addressed. The species retains some morphological and physiological traits belonging to non-domesticated plants, which make the application of some common agronomic practices challenging. Furthermore, the lack of reliable field data devoted to the definition of suitable cropping protocols represents a major constraint on the spread of this crop among farmers. This review has therefore focused on updating information on the main morphological and phytochemical traits of the crop and its agronomic characteristics and novel uses. Several gaps in technical knowledge have been addressed, and further goals for experimental activity have been outlined in order to guide farmers eager to cope with the cultivation of such a challenging and resource-rich crop

Endovascular Stent Grafts as a Safe Secondary Option for Paraanastomotic Abdominal Aortic Aneurysm

ObjectiveTo describe our experience of endovascular repair of paraanastomotic aortic aneurysm.Methods and resultsFrom March 2001 to December 2004 we identified 6 patients with a paraanastomotic aortic aneurysms following previous open repair of abdominal aortic aneurysm. All patients were treated with endovascular surgery under epidural anaesthesia. There were no major complications, surgical conversions or deaths. Four patients received a bifurcated aortic stent-graft, and two an aorto-uniliac stent-graft followed by a femoro-femoral bypass. At follow-up (mean 26.1±10.2 months) there were no deaths, endoleaks or graft migrations observed.ConclusionEndovascular surgery, avoiding general anesthesia and re-laparotomy, is the ideal technique for treatment of this complication resulting from failed primary conventional AAA repair