1,721,379 research outputs found
Innovative Systems for Masonry Infill Walls Based on the Use of Rubber Joints: Combined in-Plane / Out-of-Plane Tests
No full textWithin the INSYSME Project, funded under the 7th Framework Program by the Com- mission of the European Communities and aimed at developing innovative systems for masonry enclo- sure walls, the University of Padova and ANDIL (Italian Association of Clay Bricks and Roofing Tiles Producers) proposed a construction system named DRES (Damage Reduction Enclosure System). The system is made of a single-leaf clay masonry wall, with three horizontal deformable joints within the clay unit rows, to be employed in RC frame buildings in regions prone to medium/high intensity earthquakes. To understand the behaviour of this system, an experimental campaign on four real-scale, one-bay, one- storey RC frames infilled with both partial and full enclosure walls, was performed. The tests combine cyclic in-plane and monotonic out-of-plane loading of the specimen. Two variants of the DRES system and a reference plain masonry enclosure were first tested in the in-plane direction and then in the out-of- plane direction. An additional specimen infilled with two partial enclosures, one built with DRES and one with plain masonry, was first tested in the out-of-plane direction and then, after removal of damaged walls from the bare frame, tested in the in-plane direction. An analysis, in terms of strength, ductility parameters and damage, of the in-plane and the out-of-plane test results is carried out
The INSYSME project: Innovative construction systems for earthquake resistant masonry infill walls
No full textAt the end of 2013 the Commission of the European Communities has funded a research project for the benefit of Associations of Small and Medium Enterprises (SME-AGs), aimed at developing innovative systems for masonry enclosures. The project mainly deals with external partition systems for reinforced concrete framed buildings, i.e. infill walls. The project involves sixteen partners from seven European countries, among which there are seven universities and research centres, five industrial associations and four small and medium enterprises. In the present contribution, an overview of the main objectives and steps of the project is given, together with a general summary of the various construction systems developed by the project partners
In-plane cyclic behaviour of thin joint masonry walls
No full textNew technologies for the construction of reinforced and unreinforced masonry buildings, based on the production of new blocks, are being employed and developed and are recognized by the modern generation of codes. In particular, a technique based on the use of clay blocks with small dimensional tolerance in unit height, i.e. machine flat bed faces, for the use with special mortars for thin layer
joints, has been introduced only recently in most of the European countries. This construction technique allows simple and fast assemblage and enhances the acoustic and thermal insulation of the masonry walls.
As a consequence of the introduction of this system for the construction of masonry buildings also in earthquake prone countries, it is necessary to assess its behaviour under seismic actions. In this framework, an extensive experimental program was carried out at the University of Padua, in order to characterize the mechanical behaviour of the new construction system, also under combined in-plane vertical
and horizontal cyclic loading. The system was studied in comparison with other typologies of masonry walls currently adopted in the practice, characterized by different configurations of head and bed joints.
The test set-up for the execution of shear compression tests was created on purpose for the research, after studying the most appropriate test configurations to reproduce the behaviour of shear walls. All the data collected from the experimental activity were used to assess some analytical models available for the prediction of the ultimate capacity of masonry walls under in-plane uniaxial compression and
shear compression loading. A new formulation for the evaluation of the tensile strength of masonry was proposed and assessed against experimental data. The cyclic behaviour of the specimens was also modelled and this allowed carrying out non-linear dynamic analysis for the evaluation of the reduction of the elastic response of the masonry walls due to their hysteretic behaviour. The results obtained can be used as data-base and input for standardization purposes
Prestressing of 19th Century Wood and Iron Truss Bridges in the U.S.
No full textMany of the well-known American truss bridges built in the first half of the 19th century were prestressed. Specifically, the Long, Howe, Pratt and Rider/Moulton forms, built entirely of wood or iron or using a combination of wood and iron, were prestressed. The prestressing was achieved by driving wood or iron wedges or by tightening nuts on threaded iron rods. The level of prestressing was controlled only qualitatively, probably by observing if any elements became slack when a heavy live load traversed the span. The significant advantages of prestressing were that connections were simplified, some wood tensile connections were eliminated and, if all elements did not loosen, the stiffness of a bridge was increased.
This paper describes studies of the Eldean Bridge in Miami County, Ohio. The Eldean Bridge is a wooden Long truss, built in 1860 by James and William Hamilton. The experimental and analytical studies address the actual magnitudes of prestress forces achieved by driving wedges, the effects of prestress on the structural behavior, the loss of prestress from wood shrinkage and creep, and the need for periodic retightening. Also presented are studies of the Pine Bluff Bridge in Putnam County, Indiana. The Pine Bluff Bridge is a classic Howe truss, built in 1886 by Joseph Albert Britton. The studies quantify the actual magnitudes of prestress forces achieved by tightening nuts and examine the same issues as those for the Long truss.
After the Long and Howe trusses, two significant prestressed truss forms were patented in the U.S. They are the truss of Thomas and Caleb Pratt and the truss of Nathaniel Rider and Stephen Moulton. These designs are briefly discussed, to provide a more complete view of the early 19th century prestressed truss forms
Definizione dello smorzamento equivalente per strutture in muratura a supporto della progettazione agli spostamenti
No full textNegli ultimi anni diversi studi hanno dimostrato l’importanza di correlare gli stati limite di progetto a livelli di prestazione definiti dallo spostamento, al fine di ottenere un migliore controllo sul danno atteso in seguito ad un evento sismico.
Gli spettri in spostamento proposti dalla normativa per valori dello smorzamento superiori al valore convenzionale del 5% sono generalmente ottenuti, come per l’Eurocodice 8 e le Norme Tecniche del 2008, applicando un fattore di riduzione agli spettri elastici smorzati del 5%. Tale fattore viene definito in funzione dello smorzamento viscoso equivalente, che dipende dalla dissipazione di energia per isteresi.
In questo lavoro viene presentata una procedura per la determinazione dello smorzamento isteretico per strutture in muratura. Nella procedura si fa ricorso al sistema lineare equivalente, il cui periodo di oscillazione viene determinato attraverso analisi dinamiche non lineari su sistemi idealizzati ad un grado di libertà, utilizzando accelerogrammi sintetici spettro-compatibili. Le analisi sono state condotte utilizzando un modello isteretico tarato sui risultati sperimentali ottenuti da prove cicliche di compressione e taglio effettuate presso l'Università di Padova
Definition of equivalent damping for masonry structures in support of displacement based design
No full textIn the last years, several researches have established the importance to correlate design limit states to performance levels defined by displacement, in order to obtain a better control on expected damage after an earthquake.
The displacement spectra proposed by code for damping values higher than the nominal value of 5% of critical are generally obtained, as in the case of Eurocode 8 and the Italian Technical Code (2008), by applying a scaling factor to the elastic response spectras 5% damped. This factor is defined as a function of equivalent viscous damping, which depends on hysteretic energy dissipation.
The paper presents a procedure for determining the hysteretic damping for reinforced masonry structures. The method makes use of the equivalent linear system, whose vibration period is determined by nonlinear dynamic analysis on single degree of freedom idealized system, by using synthetic spectrum compatible time histories. The analyses are performed using an hysteretic model calibrated on experimental results obtained from cyclic shear compression tests that were carried out by the University of Padova
Review of the Progress in Thin Bed Technology for Masonry Construction
No full textThin bed technology for clay/ concrete masonry is gaining popularity in many parts of the developed economy in recent times through active engagement of the industry with the academia. One of the main drivers for the development of thin bed technology is the progressive contraction of the professional brick and block laying workforce as the younger generation is not attracted towards this profession due to the general perception of the society towards manual work as being outdated in the modern digital economy. This situation has led to soaring cost of skilled labour associated with the general delay in completion of construction activities in recent times. In parallel, the advent of manufacturing technologies in producing bricks and blocks with adherence to specified dimensions and shapes and several rapid setting binders are other factors that have contributed to the development of thin bed technology. Although this technology is still emerging, especially for applications to earthquake prone regions, field applications are reported in Germany for over a few decades and in Italy since early 2000. The Australian concrete masonry industry has recently taken keen interest in pursuing research with a view to developing this technology. This paper presents the background information including review of literature and pilot studies that have been carried out to enable planning of the development of thin bed technology. The paper concludes with recommendations for future research
Development of a fiber model for load-bearing masonry walls
No full textIn the last few years, the possibility of being able to control the damage based on the probability of occurrence of an earthquake and designing on the basis of different performance levels, has arose. Masonry is still a widespread construction system for low-rise residential buildings even for countries prone to seismic risk, hence masonry needs to develop these design concepts.
Experimental tests were performed in recent years at the University of Padova on different masonry systems, both reinforced, and unreinforced with different joints types. The tests were aimed at characterizing the masonry behaviour under combined in-plane cyclic loading, and they were used to develop an analytical model that reproduce and extend the experimental results using parametric analyses. This model is a formulation of a fiber element and is cast in the general framework of the mixed method. It includes effects of shear deformation, diagonal shear failure mechanism and it is able follow response in post-peak phase. The model is able to interpret the performances of masonry panels linking them with limit states resulting from integration of cross-section equilibrium equations. Finally, its results were generalized proposing design equations directly related to performance levels and both geometrical and mechanical properties of URM panels
Analysis of out-of-plane behaviour of tall reinforced masonry walls under P-Δ effects
No full textIn the framework of the DISWall research project, funded by the European Commission, an innovative construction system aimed at building mainly tall, load bearing reinforced masonry walls for one-storey industrial and commercial buildings, was developed. These structures are often provided with deformable roofs and, as a consequence, out-of-plane forces can be significant in the wall behaviour and can lead to the onset of second order effects. For this structural configuration, a special set-up for out-of-plane cyclic tests was designed and built, to assess experimentally the structural behaviour and calibrate moment-curvature relationships. Non-linear static parametric analyses were carried out, aimed at studying the influence of vertical load, wall slenderness and percentage of vertical reinforcement on the wall behaviour. The present contribution describes the results of first and second order bending moment analysis and of numerical parametric assessment
Development of a fiber model for load-bearing masonry members
No full textIn the last few years, the possibility of being able to control damage based on the probability of occurrence of an earthquake and designing on the basis of different performance levels, has arose. Masonry is still a widespread construction system for low-rise residential buildings even in earthquake prone countries; hence masonry needs to develop these design concepts.
Experimental tests were performed in recent years at the University of Padova on different masonry systems, both reinforced, and unreinforced with different joint types. The tests were aimed at characterizing the masonry behaviour under combined in-plane cyclic loading, and they were used to develop an analytical model that reproduces the experimental results.
This model is a formulation of a fiber element and is cast in the general framework of the mixed method. It includes effects of shear deformation, diagonal shear failure mechanism and it follows the response in the post-peak phase. The model is able to interpret the performances of masonry panels linking them with limit states resulting from integration of cross-section equilibrium equations
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