Using Discrete Event Simulation Models to Evaluate Resilience of an Emergency Department

Hospitals are critical infrastructures which are vulnerable to natural disasters, such as earthquakes, man-made disasters and mass causalities events. During the emergency, the hospital might also incur in structural and non-structural damage, have limited communication and resources, so they might not be able to treat the large number of incoming patients. For this reason, the majority of medium- and large-size hospitals have an emergency plan that expands their services quickly beyond normal operating conditions to meet an increased demand for medical care, but it is impossible for them to test it before an emergency occurs. The objective of this article is to develop a simplified model that could describe the ability of the Hospital Emergency Department to provide service to all patients after a natural disaster or any other emergency. The waiting time is the main response parameter used to measure hospital resilience to disasters. The analytical model has been built using the following steps. First, a discrete event simulation model of the Emergency Department in a hospital located in Italy is developed taking into account the hospital resources, the emergency rooms, the circulation patterns and the patient codes. The results of the Monte Carlo simulations show that the waiting time for yellow codes, when the emergency plan is applied, are reduced by 96%, while for green codes by 75%. Then, using the results obtained from the simulations, a general metamodel has been developed, which provides the waiting times of patients as function of the seismic input and the number of the available emergency rooms. The proposed metamodel is general and it can be applied to any type of hospital.     

Technical Note: Practical Challenges Facing the Selection of Conditional Spectrum-Compatible Accelerograms

There are various possibilities for the selection and scaling of ground motions for advanced seismic assessment of buildings using nonlinear response-history analyses. As part of an on-going project looking at building-specific loss assessment in Italy, this article highlights a number of challenges currently facing the use of conditional spectra for ground motion selection in practice, essentially related to the limited amount of seismic hazard information that is publicly available. To illustrate the points being made, the challenges faced when trying to develop conditional spectra and select spectrum-compatible accelerograms for a rock site in Napoli, Italy, are described and the seismic assessment results obtained for a number of reinforced concrete wall structures are presented. Aside from providing practitioners with an appreciation of the potential difficulty associated with using conditional spectra for record selection, this technical note should also motivate national authorities to provide more background information on national seismic hazard data and detailed guidance for record selection.     

Seismic Performance Assessment of Slender T-Shaped Reinforced Concrete Walls

T-shaped slender reinforced concrete (RC) structural walls are commonly used in medium-rise and high-rise buildings as part of lateral force resisting system. Compared to its popularity, experimental results on seismic performance of these walls are relatively sparse, especially for data regarding these walls in the non-principal bending directions. This article aims at providing additional experimental evidence on seismic performance of T-shaped RC structural walls. Experimental results of six T-shaped RC walls were presented. These walls resemble the structural walls found in existing buildings in Singapore and possess slightly inferior details compared to the requirements of modern design codes. The test variables were the loading direction and the axial load ratio. The experimental results were discussed in terms of the failure mechanisms, cracking patterns, hysteretic responses, curvature distributions, displacement components, and strain profiles. In addition, the experimental results were compared with methods commonly adopted in current design practice including the nonlinear section analyses, shear strength models and effective width of the tension flange. The experimental data illustrate that the shear lag effect not only was not accurately accounted for by the effective width method but also significantly affected the strength and stiffness of the tested specimens.     

Developing Representative Dual Loading Protocols for the Columns of Steel Special Moment Frames based on the Seismic Demands on These Members

The column members of steel moment frames undergo high axial forces as well as inelastic rotations during a severe seismic event. The boundaries of these simultaneous structural demands on the columns of special moment frames have been investigated in this research. Based on the results of this investigation, dual cyclic loading protocols have been developed that represent both axial force and lateral deformation demands. Contrary to other loading scenarios that have been implemented in previous studies on steel columns, the loading protocols developed in this study include simultaneous axial and lateral loading cycles with varying amplitudes. The level of axial forces and story drifts tolerated by the columns of some typical Special Moment Frames (SMFs) has been investigated through performing nonlinear dynamic analyses. These frames have been selected with several configurations and different number of stories. The results of the nonlinear dynamic analyses have been processed to assess cumulative and instantaneous seismic demands on the columns of the chosen typical frames. Subsequently, dual cyclic loading protocols have been developed such that exerting these loading protocols on individual steel columns can result in structural effects close to the general seismic demands assessed in this study. Two separate dual loading protocols have been introduced for Design Earthquake (DE) and Maximum Considered Earthquake (MCE) seismic intensity levels.     

Analytical Seismic Assessment of a Tall Long-Span Curved Reinforced-Concrete Bridge. Part I: Numerical Modeling and Input Excitation

The seismic response of bridges is affected by a number of modeling considerations, such as pier embedment, buried pile caps, seat-type abutments, pounding, bond slip and architecturally flared part of piers, and loading considerations, such as non-uniform ground excitations and orientation of ground motion components, which are not readily addressed by design codes. This article addresses a methodology for the nonlinear static and dynamic analysis of a tall, long-span, curved, reinforced-concrete bridge, the Mogollon Rim Viaduct. Various modeling scenarios are considered for the bridge components, soil-structure interaction system, and materials, i.e., concrete and reinforcing steel, covering all its geotechnical and structural aspects based on recent advances in bridge engineering. Various analysis methodologies (nonlinear static pushover, time history response to uniform and spatially variable seismic excitations, and incremental dynamic analyses) are performed. For the dynamic analyses, a suite of nine earthquake accelerograms are selected and their characteristics are investigated using seismic intensity parameters. A recently developed approach for the generation of non-uniform seismic excitations, i.e., spatially variable simulations conditioned on the recorded time series, is used. Methods for the evaluation of structural performance are discussed and their limitations addressed. The numerical results of the seismic assessment of the Mogollon Rim Viaduct are presented in the companion article (Part II). The sensitivity of the bridge response to the adopted modeling, loading and analyzing strategies, as well as the correlation between structural damage and seismic intensity parameters are examined in detail.     

髹漆丝织物的水解老化性能研究

髹漆丝织物水解老化性能的测试研究,旨在了解髹漆丝织品抗老化的能力,为出土髹漆丝织品的起取、保存和展示提供科学的依据.以精制纯漆和加入15%桐油的桐油漆分别对丝织物进行髹涂整理,并对整理后的试样进行加速碱性水解老化处理.测试表明,纯漆试样和桐油漆试样的强度和伸长性能下降迅速.老化初期与丝绸降幅相近,随着老化延续,降幅大于丝绸,桐油漆试样降幅最大.漆膜在碱性水解老化中发生开裂,对蚕丝没有保护和加固作用.桐油漆膜受碱液损伤尤为严重.老化导致蚕丝结晶度下降,脆化的漆膜和老化蚕丝结合,强度和伸长性反而不如老化丝绸.检测表明,髹涂纯生漆和桐油漆的丝织物耐碱性水解老化的能力均很差,逊于未髹漆的丝织物.相比之下,桐油漆试样尤其差.     

Integrated seismic tomography and ground-penetrating radar (GPR) for the high-resolution study of burial mounds (tumuli)

The study primarily aims at providing adequate imaging resolution of large and prominent targets of archaeological interest, such as pyramids and tumuli, at all depth levels. We implemented an integrated seismic tomography and georadar (STG) technique to perform high-resolution imaging and characterization of tumuli (burial mounds). We tested the proposed technique on a preserved late Bronze Age burial mound in northern Italy, for which STG succeeded in performing an accurate 3-D reconstruction of the structure and stratigraphy as proved by later archaeological excavations. We completed two transmission seismic tomography measurements, at present ground level and at 1.5 m elevation, with a 24-channel seismograph and 15° angular separation between geophones. The ground-penetrating radar (GPR) dataset encompasses 12 250 MHz radial profiles and 12 common mid point gathers for velocity analysis. Shallow layers of the mound are successfully imaged by GPR, whilst the structure of the deep central part of the tomb is reconstructed from seismic traveltime inversion. In particular, GPR images lenses and layers of sediments forming the external part of the tumulus, evidences of a looting attempt, peripheral structures associated with later exploitation of the mound (furnaces) and, in the external sector of the tumulus, the top of the deep layer of silty sediments covering the funeral chamber. Tomographic results reveal seismic velocity anomalies of potential archaeological interest at ground level, which were successively validated by archaeological excavations. The integration of GPR and tomographic datasets is an effective strategy to overcome the imaging and interpretation problems related to the structure of such peculiar funeral monuments. STG can be applied to a virtually unlimited dimensional range and requires a limited data acquisition, processing and inversion effort. The results of the study allowed the identification of the funeral chamber and a detailed imaging of layering and structural details.     

单檐歇山式古建筑抗震性能振动台试验

为有效保护古建筑,采用振动台试验方法,研究了中国明清官式木构古建的抗震性能。以故宫某单檐歇山木构古建为对象,制作了1∶2缩尺比例模型。模型含浮放柱底、柱架、斗拱、歇山屋顶、墙体等所有构造,且施工工艺完全符合中国明清官式木构古建施工规定。通过施加白噪声激励,获得了模型的基频和阻尼比。通过施加不同强度等级的1940年El-Centro波,获得了模型典型节点的位移和加速度响应,讨论了模型的减震系数,评价了浮放柱底、榫卯节点、斗拱、屋顶、墙体等构造的抗震性能。结果表明:模型的振动形式表现为平面内的扭摆,其原因与歇山式屋顶质量分布不均密切相关。模型的震前基频为1.47Hz,阻尼比为4.6%。地震作用下,模型的位移及加速度响应曲线近似稳定、均匀。尽管屋顶构造则对地震力有一定放大作用,但浮放柱底、榫卯节点、斗拱等构造能发挥较好的耗能减震作用。对于不同构造而言,榫卯节点的减震性能最好,其减震系数可降至0.30;斗拱次之,其减震系数可降至0.53;而浮放柱底与柱顶石之间的摩擦耗能性能最弱,其减震系数最小值为0.66。墙体在地震波强度增大过程中发生倒塌,但不影响结构整体稳定性。因此,单檐歇山式木构古建具有良好的抗震性能。     

古代壁画、彩绘显现剂应用机理和性能研究

针对粘结硬质、钙化土锈的壁画和彩绘在保护修复中使用的去除剂和显现加固剂复合应用后对其性能进行了研究测试。从光学角度对明胶膜和加样后膜折射率进行测试,对土锈剩余层粒径与厚度进行测试,又从耐久性、柔韧性等方面对两种试剂复合用的模拟壁画进行了系统评价。结果表明:两种膜的折射率几乎相同,当土锈剩余层粒径在120μm以内,厚度在70μm内的土粒都可以通过显现加固剂进行显现,恢复其古朴原貌,且不触及颜料层。复合应用后对模拟样板老化后性能测试,数据显示各方面性能良好。     

ANTAEUS Project for the Regional Vulnerability Assessment of the Current Building Stock in Historical Centers

This article presents a methodology for the seismic vulnerability assessment of current buildings, suitable for the study of historical centers at the regional scale. The applicability is demonstrated with reference to four case studies: the historical center of the city of Foggia (Italy) and three other small towns of this province, for a total of 4519 housing units. Field data were collected by several teams of technicians by means of a survey form, provided in electronic format. The subsequent data processing and drawing of vulnerability maps was performed using geographical information system (GIS) technology. The collected data were used also for the validation of the algorithm, by comparing the results with those of the methodology used by the Gruppo Nazionale per la Difesa dai Terremoti (GNDT [Italian National Group for Defense Against Earthquakes]), which is widely adopted in Italy. The results of the research study and the application showed some critical points, related to the poor nature of the information collected and to the reliability of the final results. These issues are analyzed and discussed, proposing a strategy for improving the methodology.