In the last few years, nonregular reinforced concrete (R/C) slabs have become more popular in buildings and bridges due to architectural or functional requirements. In these cases, an optimum design method to obtain the ultimate load capacity and the minimum reinforcement amount should be used. For simple R/C slabs, the yield‐line method is extensively used in engineering practice. In addition to strength, the “true” failure mechanism is also obtained by identifying the parameters that define it and minimizing the collapse load. Unfortunately, when the mechanism is too complicated to be described or defined by several parameters (e.g., in slabs with complicated geometry), the method becomes more difficult because the system of nonlinear equations becomes harder to solve through traditional methods. In this case, an efficient and robust algorithm becomes necessary. In this paper, a structural analysis of R/C slabs is performed by using the yield‐line method in association with a zero‐th order optimization algorithm (the sequential simplex method) to avoid calculating gradients as well as any derivatives. The constraints that often limit these parameters are taken into account through the exterior penalty function method, leading to a successful solution of the problem. Considering that the direction of each yield‐line is sought by minimizing the ultimate load and finding the parameters defining the collapse mechanism, another parameter concerned with the direction of an orthotropic reinforcement grid is introduced. In this way, the number of unknown parameters increases, but aside from obtaining the ultimate load and the parameters defining the collapse mechanism, the solution also finds both best and worst reinforcement orientations.
After Maillart's concrete curved arch bridges were built before the Second World War, in the second half of the past century and this century, many curved bridges have been built with both steel and concrete. Conversely, since the construction of Musmeci's shell supported bridge in Potenza, few shell bridges have been constructed. This paper explains how to design a curved footbridge supported by an anticlastic shell by shaping the shell via a thrust network analysis (TNA). By taking advantage of the peculiar properties of anticlastic membranes, the unconventional method of shaping a shell by a TNA is illustrated. The shell top edge that supports the deck has an assigned layout, which is provided by the road curved layout. The form of the bottom edge is obtained by the form-finding procedure as a thrust line, by applying the thrust network analysis (TNA) in a non-standard manner, shaping the shell by applying the boundary conditions and allowing relaxation. The influence of the boundary conditions on the bridge shape obtained as an envelope of thrust lines is investigated. A finite element analysis was performed. The results indicate that the obtained shell form is effective in transferring deck loads to foundations via compressive stresses and taking advantage of concrete mechanical properties.
Energy audits play a crucial role in energy retrofit of buildings, as the accuracy and completeness of the data strongly affect the reliability of the design energy model. The paper proposes a BIM-based workflow to manage data collection in an energy audit process, to minimize data losses and inconsistencies. The framework is based on a simplified BIM Model, linked to an external database and to a webpage. This can be used as a data container to implement a model for energy simulations. The efficacy of the workflow has been validated through a survey on window fixtures for a case study.
Shells are attractive and efficient structures that play a special role for engineers and architects. However, only few bridges supported by concrete shells have been designed and built after the Musmeci’s bridge in Potenza (Italy). Several numerical form-finding methods have been implemented in the last decades to optimize the shape of shells. In the present paper, a comparison of the Thrust Network Analysis (TNA) and Particle-Spring System (PS) is made by searching the optimal shape of a concrete shell supporting the curved cantilevered deck of a pedestrian bridge under the same boundary conditions. Finite Element Analysis was performed to compare the structural behaviour of the footbridges optimized by the two different form-finding techniques. The effectiveness of both form-finding methods in minimizing unfavourable tensile stresses in concrete shells, thus taking advantage of mechanical properties of concrete, is investigated. Furthermore, transverse deflections of the curved cantilevered deck were reduced introducing an external prestressing system applied to the upper flange of the ring box girder. Finally, the obtained results can help architecture and engineering practitioners to develop innovative bridge conceptual design.
Building Information Modelling (BIM) is increasingly adopted in supporting Facility Management (FM). However, in the future perspective of efficiently encouraging the management of building estates, e.g. owned by public authorities or institutions, providing an effective integration between Building Information Models and Geographic Information Systems (GIS) becomes also essential. This contribution is therefore aimed at presenting a methodological framework integrating BIM and GIS environments by mainly taking advantage of open-source tools (e.g. QGIS and Dynamo) and non-proprietary data exchange formats like the COBie (Construction-Operations Building Information Exchange) international standard. Unlike what has been mainly proposed in the literature concerning BIM-GIS integration so far, the methodology presented in this paper does not provide for an integral transfer of BIM data to the GIS platform. The work led instead to the development of an effective bidirectional integration between the two informative systems, by properly relating them and allowing for an easy switch from one system database to the other. This integrated framework is intended to enable facility managers to easily visualize in the GIS platform, through queryable 2D and 3D maps, some relevant information from BIM to efficiently manage workspaces. At the same time, this hybrid informative system allows BIM practitioners to access and manage more detailed information stored in Building Information Models. The findings of experimental applications of the proposed methodological approach to the ex-Macciotta pediatric hospital, a healthcare building owned by the University of Cagliari, are finally presented and discussed.
<p>Curved arch bridges with curved deck supported by an inclined arch either through web members or without are studied. Reference to shell-supported bridges is first made. It must be taken into account that even if the deck is supported by a shell, its bottom free edge (usually stiffened) is described by a thrust line, so that the shell connects the curved deck (that is a horizontal arch) with an inclined 3D funicular arch. A limit case is that the ring girder of the curved deck and the funicular arch merge dividing the shell into two parts, so that, if shell thickness tends to zero, no shell connects them. This is the case of curved bridges supported only at mid-span by an inclined arch. The efficiency of different arches is compared. Moreover, the deck can be supported not only at mid-span but also by web members connecting deck girder and inclined arch. In this latter case, the most appropriate form of the inclined arch is obtained.</p>
Shells are attractive and efficient structures that play a special role for engineers and architects. However, only few bridges supported by concrete shells have been designed and built after the Musmeci’s bridge in Potenza (Italy). Several numerical form-finding methods have been implemented in the last decades to optimize the shape of shells. In the present paper, a comparison of the Thrust Network Analysis (TNA) and Particle-Spring System (PS) is made by searching the optimal shape of a concrete shell supporting the curved cantilevered deck of a pedestrian bridge under the same boundary conditions. Finite Element Analysis was performed to compare the structural behaviour of the footbridges optimized by the two different form-finding techniques. The effectiveness of both form-finding methods in minimizing unfavourable tensile stresses in concrete shells, thus taking advantage of mechanical properties of concrete, is investigated. Furthermore, transverse deflections of the curved cantilevered deck were reduced introducing an external prestressing system applied to the upper flange of the ring box girder. Finally, the obtained results can help architecture and engineering practitioners to develop innovative bridge conceptual design.
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