Updating Numerical Models of Masonry Arch Bridges by Operational Modal Analysis

This article aims at presenting and discussing the strategies for updating the finite element numerical modeling of stone masonry arch bridges using operational modal analysis. The study comprehended three bridges: two old ones, the St. Lázaro and the Lagoncinha bridges, and a recently constructed bridge in Vila Fria, Portugal. Updating of the bridge models is performed by comparing the numerical and experimental modal parameters. Three-dimensional detailed numerical models are used to perform modal analysis of the bridges. Experimental modal identification of the bridges is based on the measurement of their acceleration responses during normal operation. The assigned material properties are also based on available results obtained from in situ and laboratory tests and on the results of visual inspection and historical research carried out for both old bridges.     

赤水“桥上桥”与生态环境变迁

本文考证了渭南、华县之间的赤水河“桥上桥”的建造年代及形成原因。通过对有关历史资料深入研究,确证下桥始建于清初(1667年),上桥则建于清朝中叶(1832年)。赤水河中上游的过度垦殖和植被破坏带来的生态环境恶化造成了下游河床泥沙淤积,形成了地面悬河,原赤水桥为泥沙淹塞,失去功能,故不得不在桥上建桥。桥上桥的形成是当地生态环境变化的结果和标志。     

Sources and Pseudo‐sources on the foundation of the Valamo Monastery

The article discusses the understanding of the road as a collective duty and institutionalized public space in late medieval Finland and the Swedish realm, as presented in the legislation of King Magnus Erikssons' law (landslag) of the late 1340s. After an introduction on the nature of past scholarship on the history of roads in Europe and Finland, the theoretical framework on the production and social implications of space on historical roads is discussed. The spatial understanding of the road in late medieval Finland is then studied in the context of medieval normative legislation, of which the main interest here is on King Magnus Eriksson's law, which was the major medieval law code valid in Finland. In the code, issues concerning roads and their maintenance are distributed to various sections of the law, but the main body of the legislation is set in Bygningabalken and Edsöresbalken. The analysis shows that, in the bygningabalken, the road and facilities attached to it such as bridges were rather exclusively discussed in the context of common duty, where the word common seems to be inherently understood as something obliged and insisted by the crown. In the edsöresbalken instead, the spatial dimensions of the road were brought forward in the context of the sworn peace of the realm, where the judicial space produced by the traveller was considered as a product of the road and the actual motives of travelling of the individual using it. The analysis of the respective chapters and decrees of the code shows that, from the point of normative legislation, the road was not only a recognizable space of its own but also constituted a judicial condition capable of producing distinctive social implications for those involved in the maintenance and use of roads in medieval Finland.     

CONCEPT AND DEVELOPMENT OF HYBRID SOLUTIONS FOR SEISMIC RESISTANT BRIDGE SYSTEMS

The development of alternative solutions for precast concrete buildings based on jointed ductile connections has introduced innovative concepts in the design of lateral-load resisting frame and wall systems. Particularly efficient is the hybrid system, where precast elements are connected via post-tensioning techniques and self-centring and energy dissipating properties are adequately combined to achieve the target maximum displacement with negligible residual displacements. In this contribution, the concept of hybrid system is extended to bridges as a viable and efficient solution for an improved seismic performance when compared with monolithic counterparts. Critical discussion on the cyclic behaviour of hybrid systems, highlighting the most significant parameters governing the response, is carried out.

The concept of a flexible seismic design (displacement-based) of hybrid bridge piers and systems is proposed and its reliability confirmed by quasi-static cyclic (push-pull) and nonlinear time-history analyses based on lumped plasticity numerical models.     

DYNAMIC RESPONSE OF SKEW HIGHWAY BRIDGES

A simplified bridge model suitable for use in a parametric study of short-span skew highway bridges and bridges with stiffness eccentricity is presented. The proposed model is simple, yet it captures all essential features that affect the dynamic response of these bridges. Using this simplified model, formulas for computing earthquake response of the bridges are developed and parameters that significantly influence the dynamic response of the bridges are identified. The study indicates that the response of a given skew bridge depends not only on its deck aspect ratio, the stiffness eccentricity ratio, the skew angles, its natural frequencies, but also on the frequency ratio. In particular, the rotational to translational frequency ratio has a pronounced influence on the dynamic response of the bridge. It is found that skew bridges with high rotational to translational frequency ratios often exhibit less dependence on such parameters as deck aspect ratios, stiffness eccentricity ratios and skew angles.     

Strands that Stand: using wire rope to date and identify archaeological sites

The invention of wire rope in the early 19th century and its continuous improvement since then provide a reasonable documentary record that can be used by archaeologists to date and identify submerged and terrestrial sites. The international character of the manufacture of and trade in this product requires a global approach to its application as a research tool.     

Fact Sheet: The Islands of Sweden

Not many think of Sweden as an island nation, but in fact Sweden has lots of islands. The actual number could be as high as 221 800, or as low as twenty‐four. Which is correct? It all depends on how one defines an ‘island’ and which ‘pieces of land surrounded by water’ are counted and why (or why not). This fact sheet presents a brief overview of the islands of Sweden, including a short discussion of problems met with trying to count and sort them. After trying either to visit, or contact, all possible Swedish islands with a permanent population but without a permanent mainland connection, the author has concluded that Sweden has 401 such islands. Their distribution according to geographical position and number of inhabitants is presented, and differences between Swedish islands and island regions are also briefly discussed.     

A Study on the Evolution in Design and Calculation of Iron and Steel Structures over the Mid 19th Century in Western and Central Europe

ABSTRACT

The design of metallic structures in the 19th century is a subject topic of much admiration, as many emblematic structures that are currently withstanding the test of time have become part of our built cultural heritage. Knowledge on the assumptions and design procedures available at that time is of importance to structural engineering nowadays. It allows for the understanding, maintaining and safe extending of the service life of historical metallic structures. The goal of this article is to describe the evolution in the design and calculation of metallic structures during the second half of the 19th century, with focus on Western and Central Europe. Special attention is paid to the similarities and differences between the 19th century design rules and the current structural design standards. Based on a literature survey, the evolution in terms of load definition, calculation methods, material properties, and verifications are described. Different design aspects are illustrated through a case study: The Garabit viaduct in France.