Bespoke Reinforcement for Optimised Concrete Structures

Flexible formwork for concrete structures has been shown to be an appropriate method for the construction of optimised concrete structures (Veenendaal et al. [1], Orr et al. [2]). With the goal of achieving low carbon design, two major challenges exist: 1) to reinforce structures with complex geometries and 2) to provide durable and resilient infrastructures. Meeting both challenges would allow one to capitalise on the fluidity of concrete to meet long-term emissions reductions targets. This will require an entirely new approach to design and construction of concrete structures.Research underway at the University of Bath is attempting to completely replace internal steel reinforcement with a knitted composite cage made from fibre reinforced polymer (FRP) reinforcement. By fabricating the cage in exactly the right geometry, it will be possible to provide the required strength exactly where it is needed.This paper will outline ongoing work which aims demonstrate that CFRP can be woven into geometrically appropriate ‘cages’ for the reinforcement of concrete beams, including consideration of the manufacturing process, construction technique, and technical design requirements

A numerical model based on ALE formulation to predict crack propagation in sandwich structures

A numerical model to predict crack propagation phenomena in sandwich structures is proposed. The model incorporates shear deformable beams to simulate high performance external skins and a 2D elastic domain to model the internal core. Crack propagation is predicted in both core and external skin-to-core interfaces by means of a numerical strategy based on an Arbitrary Lagrangian�Eulerian (ALE) formulation. Debonding phenomena are simulated by weak based connections, in which moving interfacial elements with damage constitutive laws are able to reproduce the crack evolution. Crack growth in the core is analyzed through a moving mesh approach, where a proper fracture criterion and mesh refitting procedure are introduced to predict crack tip front direction and displacement. The moving mesh technique, combined with a multilayer formulation, ensures a significant reduction of the computational costs. The accuracy of the proposed approach is verified through comparisons with experimental and numerical results. Simulations in a dynamic framework are developed to identify the influence of inertial effects on debonding phenomena arising when different core typologies are employed. Crack propagation in the core of sandwich structures is also analyzed on the basis of fracture parameters experimentally determined on commercially available foam

A moving interface finite element formulation to predict dynamic edge debonding in FRP-strengthened concrete beams in service conditions

A new methodology to predict interfacial debonding phenomena in fibre-reinforced polymer (FRP) concrete beams in the serviceability load condition is proposed. The numerical model, formulated in a bi-dimensional context, incorporates moving mesh modelling of cohesive interfaces in order to simulate crack initiation and propagation between concrete and FRP strengthening. Interface elements are used to predict debonding mechanisms. The concrete beams, as well as the FRP strengthening, follow a one-dimensional model based on Timoshenko beam kinematics theory, whereas the adhesive layer is simulated by using a 2D plane stress formulation. The implementation, which is developed in the framework of a finite element (FE) formulation, as well as the solution scheme and a numerical case study are presented

Pseudo-ductile Failure of Adhesively Joined GFRP Beam-Column Connections:An Experimental and Numerical Investigation

Glass Fiber Reinforced Polymer (GFRP) I-beam-column adhesively bonded connections are tested under combined bending and shear. The special feature of the novel connection is the wrapping of the seat angles at the connection by a carbonfiber reinforced polymer (CFRP) fabric wrap. The wrap is primarily intended to alter the connection failure mode from brittle to pseudo-ductile, thus providing adequate warning of impending failure. Four moment resisting connection configurations are tested, including the reference configuration without the wrap. It is observed that the connection failure is initiated by the fracture of the adhesive, but the provision of the wrap, together with a steelseat angle, alters the failure mode from brittle to pseudoductile. The post-peak load deformation is achieved without a large drop in the resistance of the connection. On other hand, the connection with the wrapping and a GFRP seat angle can also change the failure mode to pseudo-ductile, but it could not be done without a large reduction in theconnectionresistanceafterthepeakload

GFRP beams by bonding simple panels: a low-cost design strategy

Although traditional materials (steel, concrete, timber and masonry) still dominate the building industry, new materials are constantly being explored by engineers and scientists. For instance, the use of the so-called FRPs (Fibre-Reinforced Polymers) is gradually spreading worldwide. FRPs can be qualified as non-corrosive, high mechanical strength and lightweight materials. They have achieved in the last few years a relevant role as a building material for applications regarding both the strengthening and the realization of full-composite structures. Examples of applications of FRPs are numerous [1],[2]. The first buildings made from FRP profiles were single-storey gable frames used in the electronics industry for Electromagnetic Interference (EMI) test laboratories. A five-storey building, named the Eyecatcher Building was erected for the Swiss Building Fair in 1998. The most cost-effective way of producing FRPs is the automated process of pultrusion. This process optimizes the production of bars and thin/thick-walled profiles with both closed and open cross-sections which are constant over the length. Because the industrial process is optimized for mass pultrusion of a limited number of shapes, it is difficult to produce complex shapes with standard cost targets. A low-cost design strategy inspired by modularity, able to exploit the immediate availability of “ready-to-use” standard components, plays a crucial role for the large-scale viability of FRP structures. The idea discussed in this paper is focused exactly on the possibility of achieving a complex FRP shape by bonding an appropriate number of simple pultruded shapes with a common epoxy glue. For example, a generic I-profile may be obtained by bonding three rectangular panels (the top/bottom flanges and the web panel), rather than via a unique pultrusion application. In addition, web-to-flange junctions may also be strengthened by bonding appropriate angle profiles. In this view, the possibility of considering composite profiles of a generic cross-section from simple rectangular panels would be an interesting constructive simplification. For this reason, the authors have recently initiated a large experimental investigation, still under development, in order to compare the flexural behaviour of pultruded FRP profiles with that of bonded FRP profiles. The results have shown the possibility of achieving a very good performance, in terms of both failure load and flexural stiffness, allowing us to consider the bonding system proposed as highly competitive in the field of construction of pultruded profiles

Effect of boulder shape on the response of compound meshes subject to dynamic impacts

Rockfall is a type of natural hazard associated with the detachment of one or several boulders in steep slopes. Passive risk mitigation strategies are based on intercepting these blocks during their movement, using rigid barriers, embankments, and flexible protection systems. In recent years, the advancement of remote sensing techniques based on discrete fracture networks allows the characterisation of the shape and size of these boulders even before their detachment [13]. However, physical and numerical modelling of the impact on flexible protection system typically considers spheres [4] and truncated cubes [3] as boulder shape. In this work, the local, i.e. bullet effect [5] and full-scale effect of the aspect ratio of the block is investigated during its impact with a full-scale barrier model. The barrier is characterised by a compound mesh, formed by interweaved double-twisted hexagons and strand ropes stretched between two fence posts. The mesh geometry is reproduced within the Discrete Element framework, using the remote contact interaction approach and the fast mesh generation technique described in [11]

Automated Framework for the Optimisation of Spatial Layouts for Concrete Structures Reinforced with Robotic Filament Winding

Concrete is a major contributor to the environmental impact of the construction industry, due to its cement content but also its reinforcement. Reinforcement has a significant contribution because of construction rationalisation, resorting to regular mats or cages of steel bars, despite layoutoptimisation algorithms and additive-manufacturing technologies. This paper presents an automated framework, connecting design and fabrication requirements for the optimisation of spatial layouts as of reinforcement of concrete structures, by the means of robotic filament winding

Visual programming for structural assessment of out-of-plane mechanisms in historic masonry structures

A visual script created during the work for the paper ‘Visual programming for structural assessment of out-of-plane mechanisms in historic masonry structures’, published by Funari, Spadea et al. (2020) in the Journal of Building Engineering. A support guide document to approach the visual scripting for structural assessment of historic masonry structures. The guide shows the practical aspects of the methods theoretically developed in the paper. The dataset of a benchmark case study suitable to test the script potential is also available for download