An equivalent frame model for seismic analysis of masonry and reinforced concrete buildings

In this paper a novel equivalent planar-frame model with openings is presented. The model deals with seismic analysis using the Pushover method for masonry and reinforced concrete buildings. Each wall with opening can be decomposed into parallel structural walls made of an assemblage of piers and a portion of spandrels. As formulated, the structural model undergoes inelastic flexural as well as inelastic shear deformations. The mathematical model is based on the smeared cracks and distributed plasticity approach. Both zero moment location shifting in piers and spandrels can be evaluated. The constitutive laws are modeled as bilinear curves in flexure and in shear. A biaxial interaction rule for both axial force–bending moment and axial force–shear force are considered. The model can support any shape of failure criteria. An event-to-event strategy is used to solve the nonlinear problem. Two applications are used to show the ability of the model to study both reinforced concrete and unreinforced masonry structures. Relevant findings are compared to analytical results from experimental, simplified models and finite element models such as Drain3DX and ETABS finite element package.     

In-Plane Seismic Response of URM Walls Upgraded with FRP

Recent earthquakes have shown the vulnerability of unreinforced masonry (URM) buildings, which have led to an increasing demand for techniques to upgrade URM buildings. Fiber reinforced polymer (FRP) can provide an upgrading alternative for URM buildings. This paper presents results of dynamic tests investigating the in-plane behavior of URM walls upgraded with FRP (URM-FRP). These tests represent pioneer work in this area (dynamic and in-plane). Five half-scale walls were built, using half-scale brick clay units, and upgraded on one face only. Two moment/shear ratios (1.4 and 0.7), two mortar types (M2.5 and M9), three composite materials (carbon, aramid, and glass), three fiber structures (plates, loose fabric, and grids), and two upgrading configurations (diagonal “X” and full surface shapes) were investigated. The test specimens were subjected to a series of synthetic earthquake motions with increasing intensities on a uniaxial earthquake simulator. The tests validate the effectiveness of the one side upgrading: the upgrading technique improved the lateral resistance of the URM walls by a factor ranging from 1.3 to 2.9; however, the improvement in the lateral drift was less significant. Moreover, no uneven response was observed during the test due to the single side upgrading. Regarding the upgrading configurations, the bidirectional surface type materials (fabrics and grids) applied on the entire surface of the wall (and correctly anchored) can help postpone the three classic failure modes of masonry walls: rocking (“flexural failure”), step cracking, and sliding (“shear failures”). Additionally, in some situations, they will postpone collapse by “keeping the bricks together” under large seismic deformations. On the other hand, the diagonal “X” shape was less successful and premature failure was developed during the test.     

A Simple and Fast PCR Protocol to Detect Listeria monocytogenes from Meat

Primers for the iap gene were used to develop and optimise a PCR technique for detecting Listeria monocytogenes in meat. The use of these primers gave good results in the detection of L monocytogenes in either artificially or naturally contaminated foodstuffs. The lowest sensitivity limit achieved with PCR was 10¹–10² cells ml^-1 or g^-1 product, either in pure cultures or in artificially and naturally contaminated meat. The PCR method devised has high sensitivity and specificity. It appears to give good results and is very easy and fast to perform, requiring only 30 h to detect Listeria from meat, whereas, conventional methods require almost 96–120 h. © 1997 SCI.     

Measurement-based support for post-earthquake assessment of buildings

After a damaging earthquake, assessment of the residual seismic capacity is required for large parts of the building stock. Increased vulnerability of structures together with the threat of immediate aftershocks call for rapid and objective decision making. Structural identification has the potential to reduce parameter-value uncertainties of physics-based models through interpreting measurement data. Significant amounts of uncertainty are associated with the non-linear behaviour of structures during extreme events such as earthquakes. Therefore, a structural identification methodology that accommodates multiple sources of systematic modelling uncertainties is used. Error-domain model falsification (EDMF) enables structural identification through combining damage grades observed by visual inspection with fundamental frequencies that are derived from ambient vibrations. Parametric uncertainties of a hysteretic model are reduced with the two information sources in order to extrapolate the vulnerability of the building regarding future earthquakes. The applicability of the methodology is shown using measurements made on a mixed reinforced-concrete unreinforced-masonry building tested on a shaking table. Based on nonlinear time-history analyses involving single-degree-of-freedom models, EDMF leads to more precise, yet robust, vulnerability predictions of earthquake-damaged buildings when compared with prediction ranges that are obtained without data interpretation.     

预测钢筋混凝土墙非线性逆循环性能的分析模型

总结了钢筋混凝土墙的延性模型和非线性性能预测的研究结果。采用承载力设计方法，进行地震荷载下的钢筋混凝土墙设计。回顾了带有多层界面基于韧性的无弹性多层有限单元。提出了模拟非线性滞回性能的分析结构工程模型。对钢筋混凝土墙滞回性能的所有基本特征，包括强度退化、刚度退化、粘结滑移效应、非弹性剪切变形机制和约束效果，明确地进行了分析和试验模拟。     

Adaptive video communication for an intelligent distributed system: Tuning sensors parameters for surveillance purposes

Surveillance systems include a large set of techniques for both low level and high level tasks. In particular, in the last decade the research community has witnessed a high proliferation of techniques that span from object detection and tracking to object recognition and event understanding. Although some techniques have been proved to be very effective, those tasks cannot be considered solved. Even less, we can consider concluded the research in the field of the analysis of the activities (event analysis). It is this topic together with the problem of the information sharing among different sensors that represents the core of this work. Here, a system architecture for a video surveillance system with distributed intelligence over multiple processing units and with distributed communication over multiple heterogeneous channels (wireless, satellite, local IP networks, etc.) is proposed. A new real-time technique for changing the video transmission parameters (e.g., frame rate, spatial/colour resolution, etc.) according to the available bandwidth (which depends on the number of the detected alarm situations, on the required video quality, etc.) will be presented.     

Static Cyclic Response of Masonry Walls Retrofitted with Fiber-Reinforced Polymers

The behavior of seven one-half scale masonry specimens before and after retrofitting using fiber-reinforced polymer (FRP) is investigated. Four walls were built using one-half scale hollow clay masonry units and weak mortar to simulate walls built in central Europe in the mid-20th century. Three walls were first tested as unreinforced masonry walls; then, the seismically damaged specimens were retrofitted using FRPs. The fourth wall was directly upgraded after construction using FRP. Each specimen was retrofitted on the entire surface of a single side. All the specimens were tested under constant gravity load and incrementally increasing in-plane loading cycles. The tested specimens had two effective moment/shear ratio, namely, 0.5 and 0.7. The key parameter was the amount of FRP axial rigidity, which is defined as the amount of FRP reinforcement ratio times its E modulus. The single-side retrofitting/upgrading significantly improved the lateral strength, stiffness, and energy dissipation of the test specimens. The increase in the lateral strength was proportional to the amount of FRP axial rigidity. However, using high amount of FRP axial rigidity led to very brittle failure. Finally, simple existing analytical models estimated the ultimate lateral strengths of the test specimens reasonably well.