Reliability-based Strength Amplification Factors for Structures with Asymmetric Yielding

A reliability-based methodology to estimate strength amplification factors for structures with asymmetric yielding is proposed. The approach is based on structural demand hazard analyses. Nonlinear time-history analyses of tridimensional simplified systems are carried out. The effects of two orthogonal components of the seismic ground motions and soil-structure interaction, are considered. Results show that the expected ductility demand of systems with asymmetric yielding may be much higher than those of symmetric systems. A simplified mathematical expression (which is function of the ratio between the fundamental vibration period of the system and that of the soil, ductility demand, and level of asymmetric yielding) is proposed to estimate the amplification factors. The expression is applied successfully to a 9-story reinforced concrete building exhibiting asymmetric yielding produced by tilting.     

Masonry Italian Code-Conforming Buildings. Part 1: Case Studies and Design Methods

ABSTRACT

Several architectural configurations of unreinforced masonry residential buildings are designed according to the different methods proposed in the Italian code: rules for the so-called simple masonry buildings, linear and nonlinear static analyses. Always complying with code requirements, for each building-site combination, the design was made, as much as possible, without an excessive margin of safety. The different design methods provided buildings with very different levels of safety, being linear static analysis largely overconservative with respect to the nonlinear static approach. These buildings were then analyzed in the companion paper.     

Rocking of Non-symmetric Rigid Blocks in Buildings Considering Effects Associated with Dynamic Soil-Structure Interaction

A dynamic model for the estimation of the rocking and/or overturning response of a free-standing non-symmetric rigid block considering rotational and horizontal excitation is proposed. The block is situated at different levels of a building with flexible base subjected to earthquakes. Base flexibility introduces the rotational component of the excitation due to dynamic soil-structure interaction (DSSI). The model is used to assess the influence of the dynamic soil-structure interaction on the behavior of the block. An illustrative example of the proposed model for non-symmetric rigid blocks in 5-, 10-, and 15-story buildings located in soft soils considering earthquakes from different seismic sources is presented. Results show that it is important to consider kinematic effects as well as inertial effects of DSSI in the dynamic response of contents. The influence of base flexibility depends on the change of spectral intensities associated to the increase of the building structural period and is larger for higher building levels.     

Investigation Techniques for the Seismic Response Assessment of Buildings Located in Historical Centers

ABSTRACT

It is an acknowledged fact that historical centers, given its significance from the cultural and architectural viewpoint, bring further challenges in terms of maintenance planning, survey, and safety assessment. The preparation of an adequate investigation plan and the extent of data to be collected is highly reliant on many aspects, such as the category of the architectonic asset, the importance of the heritage site, or the resources available, for example. In what regards the seismic response assessment of urban cultural heritage assets located in historical centers, the amount and detail of data also depend on this article, scale of assessment, and current state of conservation and occupation. Within this framework, this article provides an overview of the state of the art of investigation techniques currently used in survey operations, which are currently available for improving the knowledge level of urban cultural heritage assets within historical centers, as a supporting tool for the seismic response assessment of such singular assets. Finally, acknowledging the lack of accuracy when evaluating the seismic response of an asset enclosed in aggregate as an isolated structure, this article also focuses on the identification of the main particularities inherent to buildings enclosed in aggregate.     

History in Two Dimensions or Three? Working Class Responses to History

Research carried out by the author in North Carolina (2007) aimed to assess how museums might help rebuild identity in communities devastated by economic decline. Interviews, compared with examples from ‘Time and Tide’, Yarmouth, UK, suggested that working class people feel a strong need for history, intense emotional ties to the industrial landscape, and believe that museums can radically change their lives. The evidence suggested that the importance of history to people’s sense of self has been underestimated, particularly in the case of the industrial poor. This paper considers reasons for this underestimation, and suggests that these groups may also have higher and more wide‐ranging expectations of history than intellectuals do. It suggests these ‘emotional’ uses of history, rather than being inferior to academic history, may be richer, and that this ‘three‐dimensional’ experience of history exhibited by the urban poor can enrich the two‐dimensional historical experience of the researcher or museums professional.     

Use of Pushover Analysis for Predicting Seismic Response of Irregular Buildings: A Case Study

Structural irregularity undermines capability of conventional methods for 2D pushover analysis to closely approximate results from inelastic dynamic analysis. In recent years, different methods have been developed to overcome such limitation and their suitability has been checked with reference either to idealized building models or to geometrically simple tested structures. In this paper, suitability of one such method, proposed by Fajfar et al. [2005] Fajfar, P., Maru?i?, D. and Perus, I. 2005. Torsional effects in the pushover-based seismic analysis of buildings. Journal of Earthquake Engineering, 9(6): 831–854. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar], is evaluated considering an existing school building which presents both vertical and plan irregularities. Types of irregularity encompass not only those usually considered by seismic codes but also those deriving from a bad conceptual design and construction inaccuracies, very frequent at the year of construction (1974). It is found that, even under such complex irregularity conditions, this ‘modified’ pushover analysis correlates well results from inelastic dynamic analysis almost up to failure, since, in most cases, its predictions of interstorey drifts and plastic rotations are conservatively close to values from inelastic dynamic analysis. Even failure mechanism, consisting of a floor mechanism at the third level, is correctly predicted, thus demonstrating adequacy of such method for actual framed structures.     

Simplified Macro-Model for Infill Masonry Panels

In structural analyses, masonry infill walls are commonly considered to be non structural elements. However, the response of reinforced concrete buildings to earthquake loads can be substantially affected by the influence of infill walls. In this article, an improved numerical model for the simulation of the behavior of masonry infill walls subjected to earthquake loads is proposed and analyzed. First, the proposed model is presented. This is an upgrading of the equivalent bi-diagonal compression strut model, commonly used for the nonlinear behavior of infill masonry panels subjected to cyclic loads. Second, the main results of the calibration analyses obtained with two series of experimental tests are presented and discussed: one on a single frame with one story and one bay tested at the LNEC Laboratory; and the second, on a full-scale four story and three-bay frame tested at the ELSA laboratory.     

On the Design of Viscous Dampers for the Rehabilitation of Plan-Asymmetric Buildings

In this article, one of the procedures proposed in literature for the design of viscous dampers to be inserted in existing buildings is examined and extended to 3D eccentric buildings. The proposed procedure has been verified through a case study characterized by a six-story RC building. Both plan-symmetric and plan-asymmetric configurations have been considered for comparisons. The effect of considering the plan-asymmetry in the design has been studied. Moreover, also the importance of considering the higher modes has been investigated. The effectiveness of the design procedure has been then evaluated through the comparison with nonlinear dynamic analyses.     

Design Principles for Minimum Torsional Response of Wall-Frame Concrete Structures

A seismic design procedure is described incorporating the well-accepted property that the stiffness of reinforced concrete elements is strength dependent and the requirement that the method of assigning strength to elements should be aiming at minimum torsional phenomena. Such a response allows a direct comparison with the findings of a static nonlinear analysis, which may provide the limits of story drifts and the induced plastic rotations in potential plastic hinges. The requirement of a practically translational response implies that the element strength assignment should be based on planar considerations and the initially elastic response should be of minimum torsion.     

Analysing Heritage Landscapes with Historical GIS: Contributions from problem-based inquiry and constructivist pedagogy

This article examines a practical classroom experience using GIS technologies to analyse aspects of a local heritage landscape. An inventory of historic buildings comprising architectural and construction details was revised in the field and then analysed using GIS software. Elements of the geographies of these buildings were displayed using thematic mapping and students used these maps to develop explanatory hypotheses and to suggest policy options for future management of the heritage landscape. Practically, the project demonstrated the contribution GIS can make to historical geography methods, engaged students in an externally supported research partnership working with real-world data, and suggested directions for local public policy formation. Pedagogically, the project demonstrated that historical GIS can be used effectively to shape problem-based inquiry and constructivist learning.