Shear Vulnerability of Historical Reinforced-Concrete Structures

Modern buildings have been characterized by the rapid spread of reinforced concrete as a novel and versatile building material. Within the assessment of existing buildings, the most sensitive structures are those designed in the first half of the 20th century, when the theory of reinforced concrete and the detailing rules were not yet well established. This study considers the issues related to the gradual understanding of the vulnerability at a territorial scale of structural typologies designed only for vertical loads. In particular, the shear behavior of the buildings in the period between 1920 and 1960 is investigated. The shear strength control of the structural elements of an open-air stadium in Southern Italy is carried on according to Eurocode 2, the American Concrete Institute Code, ACI 318R–2008, and a method based on Arslan’s equation. The results are compared with those included in the original calculus report according to the 1930 Royal Decree-Law (RDL 18/7/1930).     

From Sorcery to Laboratory: Pandemics and Yanyuwa Experiences of Viral Vulnerability

The COVID‐19 pandemic has prompted renewed attention among health professionals, Aboriginal community leaders, and social scientists to the need for culturally responsive preventative health measures and strategies. This article, a collaborative effort, involving Yanyuwa families from the remote community of Borroloola and two anthropologists with whom Yanyuwa have long associations, tracks the story of pandemics from the perspective of Aboriginal people in the Gulf region of northern Australia. It specifically orients the discussion of the current predicament of ‘viral vulnerability’ in the wake of COVID‐19, relative to other pandemics, including the Hong Kong flu in 1969 and the Spanish flu decades earlier in 1919. This discussion highlights that culturally nuanced and prescribed responses to illness and threat of illness have a long history for Yanyuwa. Yanyuwa cultural repertoires have assisted in the process of making sense of massive change, in the form of past pandemics and the onset of sickness, the threat of illness with COVID‐19 and the attribution of ‘viral vulnerability’ to this remote Aboriginal community. The aim is to centralise Yanyuwa voices in this story, as an important step in growing understandings of Aboriginal knowledge of pandemics and culturally relevant and controlled health responses and strategies for communal well‐being.     

文物建筑保护工程中的勘察设计——以北大红楼等三个文物建筑为例

文物建筑勘察的目的是掌握现状文物的真实状态和危险程度,进而为制定科学合理的保护方案提供重要依据和支撑。为此,探讨了文物建筑保护工程勘察设计的特点和内涵,结合实际案例,归纳总结了文物建筑勘察设计四个基本特点:在强调文物真实性的同时,要求勘察内容的完备性和详实性;强调病害机理分析与病害成因的数值仿真验证;关注文物本体的抗震性能研究;强调以最小的干预获取最真实的情况。阐述论证了建立文物防灾减灾体系的必要性和重要性,点明了文物建筑勘察设计未来的发展方向必然和防患于未然的防灾减灾体系相联系,作为该体系下的技术支撑而长期发展。     

故宫太和殿动力特性与常遇地震响应

为更好地保护故宫太和殿,采用有限元分析方法,研究了太和殿的动力特性及常遇地震作用下的响应。采用弹簧单元模拟榫卯节点及斗拱构造,并考虑柱础为铰接,建立了太和殿有限元模型。通过模态分析,获得了太和殿基频及主振型;通过对模型进行时程分析,获得了典型节点的位移、加速度响应曲线,以及典型单元的内力响应曲线,评价了太和殿的抗震性能。结果表明:太和殿基频为0.9Hz,主振型以平动为主;常遇地震作用下,太和殿能保持稳定振动状态,结构的内力和变形均在容许范围内,且斗拱及榫卯节点均能发挥一定的减震作用。     

Simplified Seismic Sidesway Collapse Capacity-Based Evaluation and Design of Frame Buildings with Linear Viscous Dampers

This article describes a simplified procedure for estimating the seismic sidesway collapse capacity of frame building structures incorporating linear viscous dampers. The proposed procedure is based on a robust database of seismic peak displacement responses of viscously damped nonlinear single-degree-of-freedom systems for various seismic intensities and uses nonlinear static (pushover) analysis without the need for nonlinear time history dynamic analysis. The proposed procedure is assessed by comparing its collapse capacity predictions on 272 different building models with those obtained from incremental dynamic analyses. A straightforward collapse capacity-based design procedure is also introduced for structures without extreme soft story irregularities.     

Displacement-Based Design of an Energy Dissipating System for Seismic Upgrading of Existing Masonry Structures

A displacement-based method for the design of an energy dissipating system is proposed in this article. The device, which is composed of added concrete walls equipped with hysteretic Added Damping and Stiffness (ADAS) dampers, is aimed at upgrading the seismic behavior of existing masonry structures. The design method is based upon a simplified model of the overall structure-dissipating system. The proposed displacement-based design procedure was tested by means of inelastic response-time history analyses considering different masonry structures. The results of the analyses were compared with the seismic behavior expected from the design.     

Full-Scale Shaking Table Tests on a Substandard RC Building Repaired and Strengthened with Post-Tensioned Metal Straps

The effectiveness of a novel Post-Tensioned Metal Strapping (PTMS) technique at enhancing the seismic behavior of a substandard RC building was investigated through full-scale, shake-table tests during the EU-funded project BANDIT. The building had inadequate reinforcement detailing in columns and joints to replicate old construction practices. After the bare building was initially damaged significantly, it was repaired and strengthened with PTMS to perform additional seismic tests. The PTMS technique improved considerably the seismic performance of the tested building. While the bare building experienced critical damage at an earthquake of PGA = 0.15 g, the PTMS-strengthened building sustained a PGA = 0.35 g earthquake without compromising stability.     

Contribution of Earthquake-Resistant Design for Reinforced Concrete Buildings when Coping with External Explosions

Fanaticism, as well as social and economic crises, has provoked a significant increase in the frequency of terrorist attacks during the last two decades and, when considered together with possible accidental explosions, has lead to a higher awareness among involved staff (owners, designers, constructors, government entities). Additionally, the fact that some buildings or targets are in seismic areas while others are not leads to a blast-loading behavior comparison. This article examines the contribution of earthquake-resistant design when coping with ground-surface explosions through nonlinear seismic assessment static analyses and nonlinear time-history analyses of blast resistance assessment using finite elements.     

Impact of Modification on Ground Motion Characteristics and Geotechnical Seismic Analyses for a California Site

The impact of different modification techniques on ground motion characteristics and results of seismic geotechnical analyses is investigated for a site in California. Twenty-eight motions were selected and scaled and also modified using both time domain (TD) and frequency domain (FD) techniques. PGV and PGD of the TD-modified motions are found to be larger than their FD-modified counterparts, but slightly less than the scaled ground motion characteristics. Cyclic stress ratios and amplification factors are similar for all sets of motions. Newmark-type slope displacements caused by the scaled and modified ground motions are similar (within 25%) for a variety of sliding masses.     

Seismic Behavior of L-Shaped RC Squat Walls under Various Lateral Loading Directions

Considerable progress has been made on the research of non-rectangular reinforced concrete (RC) squat walls over the past decades. However, the experimental data of L-shaped RC squat walls remain limited, especially for their seismic behaviors under non-principal bending actions. This paper presents an experimental and numerical investigation on L-shaped RC squat structural walls with an emphasis on how varying the directions of lateral cyclic loading influences the seismic responses of these walls. Four L-shaped specimens are tested under lateral cyclic displacements and low levels of axial compression The variables are axial loads and lateral loading directions. The performance of specimens is discussed in terms of cracking patterns, failure mechanisms, hysteretic responses, deformation components and strain profiles. Furthermore, three-dimensional finite element models are developed to supplement the experimental results. The direction of lateral loading is found to have a significant effect on the peak shear strength of L-shaped RC squat walls.