Seismic Behaviors of RC Frame Beam-Column Joints under Acid Rain Circle: A Pilot Experimental Study

This research was carried out to investigate the seismic performance of RC beam-column joints under acid rain circle via comparison of energy dissipation behavior and failure mechanism of joints with different corrosion levels and axial compression ratio. At the initial corrosion level, the strength, ductility, and energy consumption of RC beam-column joints improved slightly; at a later stage, the bearing and deformation capacity decreased as the corrosion rate of steel rebars increased. The test shows that with the increasing of the axial compression ratio, the initial stiffness and ultimate bearing capacity of the joints will increasing if the corrosion levels are the same, but the ductility of that will decrease.     

Seismic Evaluation of Tall Buildings Using a Simplified but Accurate Analysis Procedure

A simplified analysis procedure for evaluating the nonlinear seismic responses of tall reinforced concrete (RC) buildings is examined in this study. It is called the Uncoupled Modal Response History Analysis (UMRHA) procedure. It can be viewed as an extended version of the classical modal analysis procedure, where the nonlinear response of each vibration mode is first computed, and they are later on combined into the total response of the structure. The procedure requires the knowledge of the modal hysteretic behavior, which can be obtained from a cyclic modal pushover analysis. The responses of four tall buildings in Bangkok to distant large earthquakes are computed by this procedure and compared with those obtained from the Nonlinear Response History Analysis (NLRHA) procedure. These four buildings have different heights—varying from 20 to 44 stories, different configurations of floor plan, and different arrangement of RC walls. The comparison shows that the UMRHA procedure is able to accurately compute the story shears and story overturning moments, floor accelerations, and inter-story drifts of all these tall buildings. The required computational effort is also extremely low compared to that of the NLRHA procedure. Moreover, since the UMRHA procedure computes the response of each individual vibration mode, it provides more understanding and insight into the complex nonlinear seismic responses of these tall buildings.     

Effects of Geometrical Features on the Seismic Response of Historical Masonry Towers

ABSTRACT

Historical masonry structures are often located in earthquake-prone regions and the majority of them are considered to be seismically vulnerable and unsafe. Historical masonry towers are slender structures that exhibit unique architectural features and may present many inadequacies in terms of seismic performance. The seismic protection of such typologies of structures and the design of effective retrofitting interventions require a deep understanding of their behavior under horizontal loads. This paper presents the results of the seismic performance evaluation of historical masonry towers located in Northern Italy. A large set of case studies is considered, comprising a significant number of towers with high slenderness and marked inclination. First, a preliminary assessment of the dynamic behavior of the different towers is carried out through eigenfrequency analyses. Then, non-linear dynamic simulations are performed using a real accelerogram with different peak ground accelerations. A damage plasticity material model, exhibiting softening in both tension and compression, is adopted for masonry. The huge amount of results obtained from the non-linear dynamic simulations allows a comparative analysis of the towers to be performed in order to assess their seismic vulnerability and to show the dependence of their structural behavior on some geometrical characteristics, such as slenderness, inclination, and presence of openings and belfry. The evaluation of different response parameters and the examination of tensile damage distributions show the high vulnerability of historical masonry towers under horizontal loads, mainly in the presence of marked inclination and high slenderness. Some general trends of the seismic behavior of the towers are deduced as a function of the main typological features.     

Scalar Structure-Specific Ground Motion Intensity Measures for Assessing the Seismic Performance of Structures: A Review

The assessment of the seismic performance depends on the choice of the earthquake Intensity Measure (IM). During the past years many IMs, which take into account not only earthquake characteristics but also structural information, have been proposed. However, no consensus on which IM is the best predictor of the seismic response exists. Along these lines, the objective of this paper is to present the various developed scalar structure-specific seismic IMs and the problems associated with their use in practice, so that the engineer may become familiar with them and their implications in the context of Performance-Based Earthquake Engineering.     

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。     

区域形象设计的方法与实践——以冷水江市为例

本文在阐述区域形象设计的必要性与可行性的基础上,探讨了区域形象设计的理论基础和主要内容。并对冷水江市进行了实践研究。     

Single-Degree-of-Freedom Characterization of Multi-Phase Passive Control Systems

A Multi-phase Passive Control System (MPCS) combines two passive control devices in order to offset the individual weaknesses and enhance structural performance, allowing the structure to respond effectively to varying levels of loading. Previous work involving a nine-story frame demonstrated the effectiveness of MPCSs but the fundamental understanding of the system was lacking. In order to more clearly understand the behavior and identify important parameters and parameter interactions, a single-degree-of-freedom (SDOF) non-linear dynamic study was performed. The results offer significant insight towards developing structural systems adaptable to multi-objective performance-based design procedures that meet higher performance standards than for ductility-based design.     

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.