1,720,980 research outputs found
Tensile Testing on Hemp Stems
No full textBecause of its considerable impact on the environment and in line with the increasing worldwide attention to sustainability, the building industry is consistently looking for recyclable components for civil engineering applications. Among the available natural fibres, hemp has been used in bricks, blocks, panels, plasters, coats and screeds, as well as in thermal and acoustic insulation components. The stems of the plant could be used as basic reinforcing materials for seismic retrofitting applications based on fiber-reinforced mortars. In line with these goals, in this paper the mechanical properties of whole hemp stems under tensile loading have been assessed. After having assembled a suitable anchoring system, the prepared samples have been subjected to tensile tests. The results revealed intrinsic capability of the prepared specimens to bear high tensile stresses, which legitimize a potential use of hemp stems in the construction industry by collaborating with the bearing structure
Hardness vs Strength for Structural Steels: First Results from Experimental Tests
No full textCultural heritage protection and restauration are fundamental matters. Intervention design requires preliminary modelling and analysis to carefully simulate the structural behaviour of existing buildings. The identification of constructive schemes is based on direct surveys, whereas direct testing are required to reveal mechanical and physical properties of materials and their degradation status. Clearly, higher knowledge levels correspond to minor penalties in terms of material performances. For metal structures, regulations provide the employment of destructive investigations only. Furthermore, the sampling of specimens often collides with the safety requirements of artifacts. Therefore, there is a strong need for non-destructive investigations, such as the Leeb method, for a reliable in-situ characterization of carpentry steels. A fundamental step towards reaching this aim is represented by the identification of a theoretical relationship between Leeb hardness values, measured in-situ, and experimental tensile strengths. In order to identify a generally valid correlation, data of the past four years were collected from the database of the Tecnolab s.r.l. company. The experimental setup was based on in-situ Leeb analysis followed by samples collection for consequent tensile tests performed in the laboratory. The experimental data, compared to the trend provided by internationally valid guidelines, provide resistances that the regulations tend to overestimate. Therefore, designing an intervention using these resistances would not be on the safe side. Further analyses should be performed to investigate determinants related to in-situ conditions altering the steel resistance with the aim of identifying potential corrective factors
Seismic analysis and retrofitting by steelwork of existing precast RC buildings: A case study
No full textThe seismic retrofitting of existing buildings is still an open issue in the Seismic Engineering field. The need of upgrading and rehabilitation techniques is crucial, especially in highly seismic regions such as Italy. In this framework, The advantages of steel have teen clearly stated. However, its use as technology for seismic improvement and retrofitting of constructions is still limited. This study, focused on an industrial precast RC warehouse struck by the 2012 Northern Italy earthquakes, has the aim of both discussing improvements and disadvantages connected to different beam-column joint types and highlighting how local steel interventions can also improve the building global response
Leeb hardness tests for mechanical characterisation of carpentry steels
No full textSeismic vulnerability assessment requires a sufficient knowledge of existing buildings. In order to preserve existing metal structures, studies on non-destructive tests assume fundamental importance. The Leeb test performed with a portable tester is herein investigated as a method to indirectly estimate tensile strength of carpentry steels by measuring the surface hardness. The current work aims to identify a theoretical correlation between Leeb hardness values and the tensile strengths of steel deriving from direct tensile tests. Two sets of samples were analysed: existing steel profiles and new ones. The experimental results achieved were compared with the standard curves in the guidelines to evaluate the effectiveness of the latter theoretical provisions to foresee the mechanical behaviour of carpentry steels
Seismic vulnerability assessment and fragility analysis of Iranian historical mosques in Kermanshah city
No full textKermanshah is a city in Iran's Zagros seismotectonic region regarded as one of the cradles of prehistoric and historic cultures. This novel study investigates the quantitative assessment of the seismic vulnerability of historical buildings in Kermanshah using numerical modeling. This study uses the hybrid method to estimate seismic vulnerability for seven mosques in Kermanshah's historical heritage. The structures are modeled by macro-elements. The material properties for the numerical models of the mosques are calibrated through ambient vibration tests. Furthermore, the efficiency and accuracy of Italian indirect method in evaluating the damage probability in Iranian historical buildings could be determined by the comparison with the hybrid method results. Moreover, it provides the knowledge for developing these methods by the architecture and structural specifications of Iranian historical structures. In the indirect method, the aggregate effect of mosques interacting with other structures is taken into account. Finally, considering local site effects, the fragility curves of both methods are developed and compared to each other at the probable design acceleration acquired from the Iranian seismic standard. The results show the seismic vulnerability of investigated mosques and the necessity to provide some parameters for the type of ceiling and configuration of the aggregates to evaluate the Iranian historical structures by indirect method more effectively
Hardness Tests on New and Existing Steel Structures
No full textNon-destructive tests represent a valuable resource to achieve a higher knowledge of existing structures without excessively compromising its safety with the sampling operations. In this framework, the Leeb hardness test allows to measure the hardness value of steel elements directly in-site with portable devices without taking samples from the structure for laboratory tests. The purpose of the research is to find a relationship between the Leeb hardness values and the tensile strengths of steel elements to obtain reliable results that can allow to disseminate the use of this test type
Non-Linear Analysis and Retrofitting by Steelwork of a Precast RC Warehouse
No full textSeismic upgrading and retrofitting of existing constructions is a pressing need for designers and researchers. The necessity of efficient seismic upgrading/retrofitting techniques is, therefore, required in seismic-prone countries, such as Italy. In this framework, steelwork has clearly shown many advantageous applications in the last century. Nonetheless, if compared to other different technologies, steelwork is still limited for consolidation purposes. Moreover, the wide damage provoked by earthquakes to industrial buildings have induced scientific research to investigate the seismic vulnerability of such constructions much more. In the current study, the attention has been, therefore, focused on the use of steelwork systems as anti-seismic intervention techniques from a precast RC industrial warehouse hit by the 2012 Northern Italy earthquakes. Besides the usefulness of steelwork in implementing reliable techniques against earthquakes, the paper has the aim of discussing the different seismic behaviour of the building deriving from dissimilar beam-to-column joint types obtained using steelwork interventions. Other than the widely diffused static scheme with hinges, other types of joints (semi-rigid and rigid), along with the presence of a rigid roof, have been investigated, and the different seismic risk indicators derived from these static schemes have been achieved, highlighting the case of the best seismic behaviour of the warehouse. Finally, the effectiveness of local steel interventions in improving the efficient global response of the building has also been highlighted
Experimental Investigation on Cement Mortar Bricks Manufactured with Fennel Wastes
No full textCurrent practices supporting sustainable building design aim at reducing the expenditure of natural resources, such as raw materials, energy and water, in the production of construction supplies. In the current paper water is replaced by fennel centrifugate (FC) for the realization of cement mortar bricks. After having identified the most suitable cementitious pre-mixed over three potential candidates, the mechanical and physical characteristics of the FC bricks are compared to cement mortar bricks, prepared with regular water, by means of bending, compression at ordinary and high temperatures, imbibition and acoustic tests. From compared results, it is noticed that FC bricks have the same imbibition property, but tensile and compression (ordinary and high temperatures) resistances have about 20% less than the control specimen ones. The acoustic tests revealed a better response of FC bricks to the high frequencies greater than 1600 Hz. However, fennel fibres do not provide a manifest advantage, likely due to the small size of the centrifuged fragments that are not able to enhance the product tensile resistance
Seismic Analysis and Rehabilitation by Steel Jacketing of a Historical Precast RC Industrial Building
No full textThe field of seismic upgrading and retrofitting of historical buildings is an ever-developing discipline. The need of updated and ameliorative intervention techniques is fundamental, especially in highly seismic regions as Italy. The advantages of steel for the application of these techniques have been clearly stated. Nevertheless, its use as structural material is still limited both for new constructions and retrofitting of existing ones. The current study takes the inspiration from these premises, focusing the interest on the application of local steel interventions for rehabilitation of a historical precast RC industrial warehouse, that was struck by the Emilia-Romagna seismic sequence occurred in 2012. Two different local jacketing interventions of columns have been foreseen. Moreover, the efficiency of different beam-to-column joint types, namely hinge, semi-rigid and rigid joints, as well as the presence of a roof rigid diaphragm, have been examined and compared to each other by static non-linear analyses. Finally, from the achieved numerical analysis results it has been shown that the proposed local interventions also provide the global retrofitting of the building
- …
