Showing papers by "Katrin Beyer published in 2010"

Quasi-static cyclic tests on different types of masonry spandrels

Abstract: Keywords: masonry spandrels, composite spandrels, quasi-static cyclic tests, Reference EPFL-REPORT-162088 URL: http://e-collection.library.ethz.ch/view/eth:2360 Record created on 2011-01-05, modified on 2016-08-09

Quasi-static cyclic tests of two prefabricated, reinforced masonry walls

Abstract: In the second half of the 20th century, the majority of residential buildings in Switzerland have been built with unreinforced brick masonry walls and reinforced concrete floors. Following a re-evaluation of the seismic hazard in Switzerland, a country of moderate seismicity, the seismic design spectra have increased in the last revision (2003) of the Swiss building code. As a consequence, it has become very difficult to justify the use of unreinforced masonry walls as sufficient seismic resistance elements. In many new residential buildings, structural walls are constructed as reinforced concrete walls instead of unreinforced masonry walls although the latter provide better thermal and insulation properties at a lower cost. Reinforced masonry systems, which could constitute a viable alternative to reinforced concrete walls, are rarely used within Switzerland. The objective of this research project was therefore to develop a reinforced masonry system unlike most reinforced masonry systems that are available on the international market today. It was decided to develop a prefabricated wall system that would require less construction time and allow an easier introduction to the Swiss market. The most critical construction detail is the connection between the prefabricated wall and the foundation. In a preliminary study two different connection details were developed and their functionality tested by means of quasi-static cyclic tests of full-scale wall elements. This paper summarises the details of the system, the test setup, the instrumentation and the test results. The tests were able to show that the proposed systems achieve similar displacement ductilities as ductile reinforced concrete walls. Finally, recommendations for further improvement of the suggested prefabricated reinforced masonry wall system are made.

Seismic behaviour of different types of masonry spandrels

Abstract: Most residential buildings that were constructed during the last century in Switzerland are 2-6 storey unreinforced masonry (URM) structures. At the beginning of the century, houses were constructed with timber floors and small bricks. This type of construction was later replaced by one which used larger, perforated bricks and reinforced concrete slabs. When assessing the seismic risk in Switzerland, a good understanding of the performance of the different types of URM buildings is mandatory. Numerical analyses have shown that spandrel beams have a significant influence on the seismic behaviour of URM structures since they influence strongly the stiffness and strength of the structure. However, until today, spandrel elements are often not considered when modelling URM structures because only very limited information on their force-deformation characteristics is available. For this reason a research project was initiated that aims at investigating the behaviour of different configurations of spandrel beams in URM walls using numerical and experimental methods. As part of the project large-scale, quasi-static monotonic and cyclic tests of spandrel beams were carried out. The test units represented spandrel beams in modern URM structures with reinforced concrete slabs or ring beams as well as spandrel beams in older URM structures with wooden floors. This paper presents the results of the test campaign on masonry spandrels in URM structures with wooden floors. Four spandrels were subjected to a quasi-static cyclic loading regime. The masonry spandrels were supported by either a timber lintel or a shallow masonry arch.

Experimental investigation of the cyclic behaviour of unreinforced masonry spandrels

Abstract: In unreinforced masonry (URM) walls the vertical piers are connected by horizontal spandrel elements. Numerical simulations have shown that spandrels influence significantly the global wall behaviour under seismic loading. Despite their importance, experimental data on the cyclic behaviour of these spandrels is very scarce. The lack of experimental data prevented in the past the validation of numerical and mechanical models regarding the cyclic behaviour of masonry spandrels. For this reason a research program was initiated in which the cyclic behaviour of masonry spandrels was investigated experimentally and numerically. Within this program different configurations of masonry spandrels were tested under quasi-static monotonic and cyclic loading. The spandrel configurations that were investigated included pure masonry spandrels and masonry spandrels which also comprise a reinforced concrete (RC) beam or slab. The latter represents spandrels in newer masonry buildings with RC slabs or RC ring beams while the former can be found in older masonry buildings. This paper presents preliminary results of the experimental program as well as some selected results of the accompanying numerical study.

Comportamento e analisi non lineare di nuclei in calcestruzzo armato (Behaviour and nonlinear analysis of RC core walls)

Abstract: Nuclei in calcestruzzo armato (CA) sono spesso utilizzati per irrigidire le strutture in zona sismica e, se progettati in modo corretto, ne garantiscono un comportamento adeguato. I recenti terremoti de L’Aquila e del Cile hanno pero mostrato come nuclei apparentemente costruiti in modo ragionevole hanno subito seri danni. In quest’ambito un’importante difficolta consiste nella limitata disponibilita, sia nella letteratura tecnica che nelle norme strutturali, di indicazioni di progetto specifiche. Nonostante la complessita di questi elementi strutturali spiccatamente tridimensionali, la maggior parte delle norme chiede al progettista di trattare i nuclei in maniera analoga ai setti rettangolari, senza pero specificare dove questa analogia risieda. Questo articolo vuole fornire un contributo alla comprensione del comportamento anelastico dei nuclei nonche alla sua modellazione. In una prima parte sono discussi aspetti importanti riguardanti le caratteristiche di forza-spostamento di nuclei a “U”, prendendo spunto dai risultati di alcune prove sperimentali recentemente svolte dagli autori. Nella seconda parte invece, viene proposta una strategia di modellazione numerica semplificata, in grado di cogliere le peculiarita del comportamento isteretico mostrate dall’evidenza sperimentale. La cosiddetta Wide Column Analogy (WCA), sviluppata a partire dagli anni sessanta del secolo scorso per l’analisi elastica di pareti a sezione sagomata, permette di modellare nuclei tridimensionali tramite elementi a trave. Scegliendo adeguatamente le caratteristiche di questi elementi e possibile simulare in maniera abbastanza accurata il comportamento ciclico anelastico dei nuclei. L’efficacia e la semplicita della strategia proposta sono mostrate sia riproducendo i risultati sperimentali presentati, sia proponendo una serie di raccomandazioni pratiche di facile applicazione per la modellazione di nuclei in CA.

Das Verhalten von Gebäuden mit Stahlbetontragwänden während des Erdbebens Centro-Sur in Chile am 27.2.2010

Abstract: Am 27. Februar 2010 um 3.34 Uhr Ortszeit ereignete sich im südlichen Zentral-Chile ein sehr starkes Erdbeben mit der Magnitude Mw = 8,8. Es ist damit eines der größten, jemals aufgezeichneten Beben. Chile gehört zu den Ländern mit großer Seismizität und hat bereits in der jüngeren Vergangenheit einige starke Erdbeben entlang seiner Küste erfahren (1835, 1906, 1928, 1960 und 1985). Das Epizentrum des diesjährigen Erdbebens lag 330 km südlich der Hauptstadt Santiago etwa 20 km vor der Küste der Region Le Maule in einer Tiefe von ungefähr 35 km (Bild 1). Die Bruchfläche erstreckte sich über eine Länge von 460 km. Das Beben forderte 577 Todesopfer, ein großer Teil davon als Folge der entstandenen Flutwellen bis 11 m Höhe, die bereits nach 30 Minuten die ersten Küstenorte erreichten. Die gesamten Sachschäden werden auf USD 30 Milliarden geschätzt [EERI10]. Chile ist weltweit eines der wenigen Länder mit hoher Seismizität, in welchem fast alle höheren Gebäude mittels Stahlbetontragwänden für horizontale Kräfte ausgesteift werden. Einige davon wurden beim Erdbeben vom 27.2.2010 unerwartet stark beschädigt. Im folgenden werden typische Schadensbilder von Stahlbetontragwandgebäuden präsentiert und mögliche Gründe für die Schäden diskutiert. In den meisten übrigen Ländern mit hoher Seismizität werden Stahlbetonrahmengebäude bevorzugt (z.B. in Japan, Neuseeland, Griechenland und Italien). An der Westküste der USA wurden ebenfalls in der Vergangenheit Rahmentragwerke bevorzugt, in den letzten Jahren hat jedoch eine Trendwende eingesetzt und viele der neuen Hochhäuser verwenden nun Stahlbetonkerne als Aussteifung. Ferner ist Chile ein Land, in dem bereits seit sehr langer Zeit Erdbebennormen existieren und mit Erfolg umgesetzt wurden. Die mehrgeschossigen Stahlbetongebäude sind deshalb allesamt auf Erdbeben bemessen. Die gemeinsame französisch-schweizerische Erkundungsmission der Association française du génie parasismique (AFPS) und der Schweizer Gesellschaft für Erdbebeningenieurwesen und Baudynamik (SGEB) bot daher eine seltene Gelegenheit, das Verhalten von auf Erdbeben bemessenen Stahlbetontragwandgebäuden zu studieren und daraus Folgerungen für mitteleuropäische Verhältnisse zu ziehen [Mar+10]. Der Beitrag beginnt mit einem kurzen Abriss der Geschichte der Erdbebennormen und einen Überblick über das Schadensausmaß bei Gebäuden, gefolgt von der ausführlichen Beschreibung der Schäden an ausgewählten neueren Stahlbetontragwandgebäuden. Zum Abschluss werden mögliche Ursachen für die Schäden an Stahlbetontragwandgebäuden diskutiert und einige Aspekte der chilenischen Erdbebennorm mit denjenigen des Eurocodes 8 verglichen. Das Verhalten von Gebäuden mit Stahlbetontragwänden während des Erdbebens Centro-Sur in Chile am 27.2.2010