Experimental Investigation on the Torsion-Shear Behaviour at the Interfaces of Interlocking Masonry Block Assemblages

This paper presents an experimental investigation on the initial shear (cohesion) and torsion-shear strengths at the interface of an interlocking masonry block. An interlocking block is a rigid unit with locks avoiding the block to slide. This improves the seismic response of dry jointed assemblages of masonry structures subjected to in-plane and out-of-plane loading. The experimental investigation is designed and carried out for the corrugated interface having one lock with rectangular cross section, i.e. the specimen is an interlocking unit composed of a main body and a lock located on the upper face of the main body. Cement- based mortars are selected to reproduce the specimen, casted using a mould provided by a 3D printer, and both the lock and the main body are kept rigid during the tests. The initial shear and torsion-shear capacities of the interface at which the lock is connected to the main body are assessed together with its quasi-brittle fracture and registered in terms of load- displacement curves. In the designed setup, the horizontal force is applied to the rigid lock until it is disjointed from the rigid main body of the block, while the effect of rocking during the shear test is avoided. The force and the displacements are measured using a load cell and Linear Variable Displacement Transducers (LVDTs), respectively. The experimental programme includes four different sets with different load application points and different load directions, each set repeated on a number of similar specimens. Empirical formulations between the initial shear and compressive strengths of the lock interface are also evaluated

Timber Coverings of the Palatine Chapel in Caserta Royal Palace

The analysis of the timber covering structure of Palatine Chapel in the Royal Palace of Caserta, built in the eighteenth century by Luigi Vanvitelli, is the object of the present study. The interpretation of its structural behaviour has been based upon a detailed survey and visual as well as non destructive inspections. Results of decay analysis have shown presence of confined damaged areas, which in any case do not induce exceeding safety limits, or loss of serviceability. At the aim of understanding the designing process followed by the architect in deciding the best disposition of the structural elements and specifically in choosing the slope of the underlining inclined posts more efficient to optimize structural behaviour, a comparative analysis has been done on different theoretical schemes obtained varying that slope. Numerical results evidence how little modification on Vanvitelli’s scheme will not leave the same safety margins

Timber Pins Connection: Reliability of Bolted Joints Design Rules

The use of timber pins in connecting timber elements is a valid alternative to the employment of metallic devices, and apart from being quite spread in prefabricated timber frames, it could be an efficient solution in the field of restoring timber structures. The design rules for pinned joints are universally based on Johansen’s theory, (European Yield Model), but their application to timber pegged connections still shows some unsolved problems, linked to: 1) dowel-bearing strength; 2) bending strength of the pin; 3) shear strength of the pin; 4) the feasibility of the fourth failure Mode of EYM. Many studies analysing one or more of those aspects can be found in literature, but there isn’t yet an analytical formulation alternative to this on which the EYM is based. Authors are carrying on an extended experimental research, trying to better understand the complex mode of failure of timber joints connected by timber pegs, and consequently improving design rules. A first phase has involved double shear plane joints of glulam fir connected by ash pins, varying thickness of jointed board, pointing out the role of bending strength. In a second step the role of dowel-bearing strength has been investigated, choosing as base material three wood essences with quite different densities. Now the final step of the whole research is presented: first of all, the role of pin shear strength has been studied; then all obtained results are employed in analyzing the behaviour of double shear plane joints with varying timber essences and its transposition in using design rules

The Influence of Dowel-Bearing Strength in Designing Timber Pegged Timber Joints

The employment of timber pegs in timber structure joints is a widespread technology in the field of timber frame building in the United States, where the Timber Frame Engineering Council has published a special Standard to supplement the National Design Specification for Wood Construction. The authors have been studying the possibility of supplementing the Eurocode 5 design formulas, thought for timber joints with metal connectors, with specifications needed for a reliable design when employing timber pegs. The field of application envisaged is that of restoring timber structures and results obtained until now are quite encouraging. In this step of the research, more attention has been paid to deformation process: fir and chestnut samples have been tested to determine their dowel-bearing behavior with steel and ash timber peg while double-shear plane joints made of the same wood species, and fastened with steel as well as timber pegs, have been analyzed

Timber covering structures of churches built in Naples during Angevin domination

ABSTRACT: This research goes trough historical phases of the most ancient churches built during Angevin domination in Naples Kingdom, (thirteenth - fifteenth centuries), and specifically of their covering structures. Between those churches, only St. Mary of Donnaregina and St. Peter from Majella preserve their ancient covering systems, on which a deep study has been done, also tracing the history of the most relevant transformations, partly due to decay, partly due to “remedies” contrasting deformation effects induced by the addiction of the ceilings. The efficiency of those interventions has been verified comparing the static analysis on the original schemes with that on the modified ones. The historical research has been extended to the other main Angevin churches in Naples, even if they haven’t preserved their ancient timber covering sys-tems, and it has shown that the most widespread covering system was that constituted of simple king post trusses, with slope of about 30°. The only differing one is that of St. Claire church

Resistographic inspection of ancient timber structures for the evaluation of mechanical characteristics

Among non-destructive testing methods for the analysis of ancient timber structures, the Resistographic method is gaining great diffusion. This method is based on the registration of density, variations through timber sections by means of an electronic drill and nowadays it is generally employed only to detect the presence of defects and damage. The present study is about the use of Resistographic method to evaluate mechanical characteristics of timber and, with this aim, an experimental program on wood-worm damaged timber has been carried on. Results show the usefulness of this non-destructive testing method as it allows the investigation through the interior part of timber and thus can give a quite reliable idea of local strength of wood in the examined section. That gives an useful parameter for the detection of recoverable elements in standing timber structures to be restored. In the present research, beech compressive strength has been evaluated from small clear wood specimens, while the evaluation of strength of dimensional lumber is outside the scope of the work

Feasibility of Timber Pegged Joints for Seismic Design of Structures

This paper investigates the feasibility of employing timber pegged joints in modern seismic-resistant structures or for retrofitting existing structures. The behavior of timber pegged connections has been investigated for about twenty years, but seismic design aspects are not treated in existing standards. In the framework of the force-based design approach, this paper analyzes and defines seismic design aspects and rules for timber pegged connections that are easy-to-use in engineering practice. A large database (more than 350 test results) has been elaborated and the data processed with the purpose of (1) analyzing the effectiveness of the European Yield Model for evaluating the maximum strength of the connection, accounting for the particular embedding behavior due to the presence of timber peg; (2) assessing and defining the capacity design rules to design the dissipative regions (i.e., overstrength factor); and (3) defining the available ductility of the connection with identification of ductility class intervals. The obtained results proved that timber pegged joints have a good potential to be used in seismic-resistant structures. In fact, data processing identified a suitable value for the overstrength factor (useful to project the joint with the capacity design) similar to that used for steel-dowelled connections, and defined a likelihood range of ductility classes. Finally, it is highlighted that the European Yield Model can be a practical tool to calculate connection strength, provided that some modifications are included to consider peg behavior

Restoring of timber structures: connections with timber pegs

quite widespread methodology of restoration of ancient timber structures envisages the introduction of new timber elements, connected to the standing structure by a timber-to-timber joint. An efficient alternative to the most used jointing technologies, which employ metallic bolted plates, steel pins, or epoxy resin adhesives, could be the use of timber pegs, if reliable design formulas could be found in codes devoted to timber structures. The design rules currently available for pinned joints contemplate only steel connectors, involve mechanical characteristics of the dowel as well as of the timber elements constituting the joint and are based on Johansen’s theory. The present research has the target of verifying the applicability of this theoretical model, and of the derived design formulas, to the case of timber pegs. At this aim, an experimental research has been performed, devoting special attention to the description of timber peg behavior inside the double shear plane joint and of dowel-bearing strength of the base timber, when a timber peg substitutes the envisaged steel bolt. Obtained results were compared with theoretical ones, showing that the different nature of the material employed for the pins needs more specific evaluation of the mechanical properties to be inserted in design formulas. Moreover, as in the field of new building timber joints fastened by timber pegs are widely employed in prefabricated timber frame industry, contents of the design standard for those structures are also taken into account, especially with reference to the “effective shear” failure mode of the timber peg