Ezio Giuriani

Experimental study on stud shear connectors subjected to cyclic loading

Abstract Steel and concrete composite beams with deformable connections subjected to repeated loads may force the studs during unloading to a reverse shear load. In order to investigate the behavior of connectors in structures subjected to shear there is a need of a test that can simulate as confidently as possible the actual behavior of studs under reverse cyclic loading. For this purpose a direct shear test is herein proposed and discussed in detail. The test was used to study the behavior of the connectors in four specimens: two of them were subjected to monotonically increasing loading while the others were submitted to cyclic loading. The results of monotonic tests were compared with those obtained with a standard push-out test and showed good agreement. Cyclic tests were performed subjecting the specimens to various blocks of cycles between two load values. These tests gave useful information both on the shape of the load-slip curves and on the damage accumulation at the end of each cycle.

Experimental testing of engineered masonry infill walls for post-earthquake structural damage control

The paper presents the results of an experimental campaign on the behaviour of engineered masonry infill walls subjected to both in- and out-of-plane loading. The aim of the research was to develop a design approach for masonry infill walls capable of solving their vulnerability and detrimental interaction with the frame structure when exposed to seismic excitation. Tests on two large-scale specimens and sub-assemblies were performed in order to evaluate the infill deformation capacity, the damage associated with different drift levels, and the mechanical properties of the components. A design solution with sliding joints to reduce the infill-frame interaction and ensure out-of-plane stability, which was proposed in a previous study, was developed and refined with focus on construction details. The aim of sliding joints is to ensure a predetermined mechanism in the infill wall, which is governed by hierarchy of strength and is capable of ensuring ductility and energy dissipation that can be taken into account in the design practice, thanks to the predictability of the response. The two infill wall specimens, one of them including an opening, reached up to 3 % in-plane drift with very little damage and supported an out-of-plane force equivalent to a horizontal acceleration four times the acceleration of gravity. The force-displacement hysteretic curve, sliding at the joints and crack pattern show the efficiency of the construction technique, based on affordable and tradition-like construction processes and materials. The technique, presented here for hollow fired-clay masonry units, can be extended to different masonry infill typologies.

Wooden Roof Box Structure for the Anti-Seismic Strengthening of Historic Buildings

A wooden roof strengthening technique aimed at transforming the roof pitches into anti-seismic shear-resisting diaphragms is presented in this article. Shear diaphragms gather and transfer the seismic loads to the shear-resisting walls. Diaphragms are built on top of the existing structures without significantly modifying the roof overall layout. The proposed strengthening technique is mainly reversible, minimally impairing the building integrity, and can be easily applied for the construction of anti-seismic wooden roofs in new buildings. A simplified design approach is presented, which allows identification of the static role of each element. An analytical method for the estimate of the box structure displacements, as well as a short digression on the displacement control requirements is also illustrated. The diaphragm technique was recently applied for the anti-seismic retrofit of some monumental buildings in Italy. A few case studies, as well as the basic design criteria for applying this technique are presented in this article.

Cyclic behaviour of a full scale RC structural wall

Abstract The results of an experimental test on a full scale RC structural wall subjected to cyclic loading are herein presented. The tested specimen is representative of a wall in a four storey building with one underground floor, designed for moderate seismic actions (PGA=0.20 g) adopting the European Seismic Code (Eurocode 8, EC8). The experimental specimen is 15.5 m long and has a transverse section of 2800×300 mm. The boundary conditions consist of simple supports at the foundation and ground floor levels. The wall behaviour has been studied both under service conditions, up to yielding, defined as the point to which first yield of the outermost rebars corresponds, and ultimate conditions, up to collapse.

A penetration test to evaluate wood decay and its application to the Loggia monument

Facing the problem of restoration and consolidation of wooden beam floors and roofs of historical buildings and ancient masonry houses, it is important to evaluate wood decay in a reliable way. The techniques usually adopted require the taking of samples, laboratory tests, radiographs or ultrasound analysis, while tests in situ are usually based on yard practice and generally give only some qualitative information about wood condition. In the present work a method and an operative technique are proposed which make penetration measurements possible. The test can be regarded as an extension of the dynamic penetration test used for soil investigation and it is based on the pentration of a graduated rod, which advances by means of repeated blows of a rebound hammer. A preliminary study was done to identify and prepare the most suitable equipment. An attempt to find a possible correlation between wood flexural strength and penetration test results was also done and the correlation curve for spruce wood seems to give a reliable result. This technique was proposed and adopted for a broadbased investigation of the roof vault of the Palazzo della Loggia, a 16th century building in Brescia (Italy), and it gave useful indications of the extent and depth of the decay of the supporting wood structure.ResumeQuand on se trouve confronté aux problèmes de restauration et de consolidation de poutres de bois soutenant les planchers et toitures de monuments historiques et de maisons en maçonnerie ancienne, il convient d’évaluer avec sûreté l’altération du bois. Les techniques dont on se sert habituellement demandent le prélèvement d’échantillons, des essais de laboratoire, une analyse radiographique ou ultrasonique; d’autre part, les essais in situ s’appuient en général sur une technique lde terrain, et fournissent seulement quelques informations qualitatives sur l’état du bois.Dans ce travail, on propose une méthode et une technique opératoire qui permettent d’effectuer un essai de pénétration que l’on peut considérer comme une extension de l’essai de pénétration dynamique utilisé pour les études de sol. Le principe de cette technique réside dans la pénétration d’une tige graduée qui avance grâce aux rebonds répétés d’un marteau. On a effectué une étude préliminaire pour trouver et mettre au point l’appareillage le mieux adapté. On s’est également efforcé d’établir une corrélation entre la résistance à la flexion du bois et les résultats de l’essai de pénétration. La courbe de corrélation pour le bois de sapin semble donner un résultat sérieux. Cette technique, proposée et adoptée pour une vaste étude menée sur la voûte en bois du Palazzo della Loggia, un bâtiment du 16ème siècle de Brescia, a fourni des indications utiles sur l’étendue et la profondeur de l’altération de la structure portante en bois.

Experimental Study on the Injected Anchors Behaviour on Historical Masonry

The proposed paper reports the results of a research on the behaviour of injected anchors in historical masonry. The purpose of this investigation was to develop a methodology to be used as a preliminary design stage for structural interventions in order to pre-qualify the real strength of this kind of anchors. Several preliminary tests in laboratory with test specimens made of concrete and masonry and a first series of in situ tests on different types of masonry were conducted to analyse the behaviour of the anchorage and of the mortar. As this test is not included in National Standard, the studied standardised methodology could be adopted as a Guideline.

Ductility of a Structural Wall with Spread Rebars Tested in Full Scale

The experimental work focuses on the ductility of the reinforced concrete (RC) seismic structural walls in buildings of mid-rise height. A full-scale five-story structural wall was tested to obtain results, still scarce in literature, without the influence of size effect. An unusual detailing with large diameter longitudinal rebars uniformly distributed in the wall length was adopted to prevent premature web rebar fracture and shear sliding. The plastic hinge length and deformations were evaluated in detail. The results show the high ductility of the wall that reached a total drift of 2.5%, larger than those usually required in design.

Thin-folded Shell for the Renewal of Existing Wooden Roofs

ABSTRACT In this article, a technique for the renewal of historic building wooden roofs is presented. The solution can be used for the strengthening of existing wooden roofs against excessive lateral thrusts on the peripheral wall or for the recovery of the attics, as it allows removing the existing structural elements, such as possible wooden truss-works of no artistic value. With minor adaptations, the solution can be addressed to enhance the building seismic performance. The technique is minimally impairing on existing buildings and can be applied also in new constructions. The technique is based on the construction of a thin folded shell, overlaying the existing pitches. Emphasis is given to lightweight folded shells, obtained by overlaying thin plywood panels on the existing roof rafters and planks, without modifying the overall architectural layout. The technique conceptual design is discussed and a simplified analytical method is proposed, which allows for the clarification of the role of each structural component and can be adopted for the folded shell proportioning and design. The analytical results are validated against numerical results obtained with reference to some case studies. Ultimately, emphasis is given to the detailing, whose correct execution is mandatory for the success of the proposed structural intervention.

Seismic Vulnerability for Churches in Association with Transverse Arch Rocking

The research work stems from the surveys and the analysis of the damages surveyed in several churches following the 2004 earthquake in northern Italy. Focus is paid to the rocking of the diaphragm arches, which frequently induced significant damages, such as yielding or failure of the tie rods and, in one church, the collapse of the nave vaults. The diaphragm arch-rocking collapse mechanism is studied referring to the limit analysis approach, taking into account the phenomena involved, such as the buttress action of the abutments and the confining action of the tie rods. The analytical evaluation of the collapse multiplier in the case of either over-resisting or weak ties is proposed. The analytical model is validated by comparison with the experimental behavior of an arch-to-abutment structure subjected to rocking. As an example, the analytical model is applied for the structural vulnerability assessment of two churches, which were severely damaged by the 2004 earthquake.

Experimental tests on the shear behaviour of dowels connecting concrete slabs to stone masonry walls

An experimental investigation has been conducted on the behaviour of dowels used to connect concrete slabs to stone masonry walls in order to transfer horizontal shear forces. A technique for embedding the dowels in the stone block without injection of grouting material or resin has been developed. Special experimental equipment has been designed in order to allow the execution ofin situ load tests on representative ancient buildings. Monotonic loading tests have been carried out on eight specimens with the purpose of measuring both stone block displacement and dowel deformationResumeDans ce travail nous avons mené une enquête expérimentale sur le comportement vis-à-vis de l’effort tranchant des connexions à goujon, utilisées dans le but de transmettre les actions horizontales (par ex. forces sismiques) entre une dalle en béton armé et une maçonnerie en pierre. La technique adoptée consiste dans l’ancrage des goujons dans la maçonnerie, réalisé au moyen d’un trou calibré dans la pierre, puis d’une insertion en force du goujon. Cette technique présente l’avantage de ne pas exiger des interventions onéreuses au niveau de la maçonnerie, susceptibles d’en réduire la résistance.Nous avons préparé un appareillage spécifique permettant l’exécution d’expériencesin situ. Pour simplifier l’exécution, l’effet de la dalle en béton a été simulé à l’aide d’une plaque métallique conçue dans ce but. Nous avons donc effectué huit expériences sur la maçonnerie en pierre d’un vieux bâtiment. Durant chaque expérience, la charge subissait de faibles accroissements progressifs et, à chaque accroissement, on enregistrait aussi bien le déplacement relatif entre la plaque métallique et la maçonnerie que les déplacements (translation et rotation) du bloc auquel le goujon était fixé. La plupart des échantillons essayés ont atteint la rupture par cassure transversale du bloc due à des glissements entre la plaque métallique et la maçonnerie, variant entre 2 et 4 mm.Après la rupture par cassure du bloc, on n’a pas relevé de brusques réductions de la capacité portante qui, au contraire, est restée constante ou a enregistré une légère augmentation avec l’accroissement du glissement. Nous avons par ailleurs déterminé la charge correspondant à la limite d’écoulement du goujon. En outre, dans les essais effectués, la translation du bloc constitue 20 à 30% du glissement global de la plaque par rapport à la maçonnerie.