Lorenzo Macorini

Nonlinear analysis of masonry structures using mesoscale partitioned modelling

This paper presents an effective and accurate computational strategy for unreinforced brick masonry structures. Mesoscale descriptions allow a realistic representation of the nonlinear structural behaviour of URM, but can pose prohibitive computational demands for large-scale problems. To overcome this drawback, the computational strategy presented in the paper employs the domain partitioning approach, which is coupled with an accurate mesoscale finite element model. This allows the effective parallelisation of the nonlinear structural analysis simulation, where significant speed-up can be achieved in the nonlinear analysis of large masonry structures. The potential and effectiveness of the proposed computational strategy are shown through numerical examples, where full-scale masonry structures are considered.

A novel hybrid system with RC-encased steel joists

ABSTRACT The paper presents the main results of an experimental and numerical study on a novel structural frame system, which employs RC encased steel joist beams and columns. An accurate 3D numerical model has been used to represent the resistance mechanisms in beams and beam-to-column connections. Experimental and numerical outcomes have been employed to develop suitable analytical models to be used in practical design. In particular, the beam flexural response has been investigated, providing a simple relationship for the flexural rigidity at different load levels. Capacity models have been then proposed for the bending and shear resistance of partially and fully-encased beams, and for exterior beam-to-column joints.

Nonlinear Analysis of Unreinforced Masonry Walls under Blast Loading Using Mesoscale Partitioned Modeling

AbstractThis paper presents the application of an advanced modeling strategy for the nonlinear analysis of structures with unreinforced masonry (URM) components under blast loading. This approach enables the investigation of the nonlinear dynamic response of large structures with URM walls, accounting for the mechanical and geometrical characteristics of URM components, the coupling between the in-plane and out-of-plane response as well as the interaction between URM panels and the other parts of the considered structural system. According to the utilized strategy an URM wall is described by a parent structure, which consists of super-elements representing the partitioned subdomains, allowing effective parallelization of the nonlinear structural analysis simulation. Each partition is represented by a detailed 3D mesoscale model, which uses an advanced 2D nonlinear interface element that allows the representation of crack propagation in URM elements. Furthermore, the macroscale model considers only the par...

Numerical investigation of arches in brick-masonry bridges

Abstract A significant number of old masonry bridges are still in use and need to be assessed considering current traffic loading and safety requirements. Masonry bridges are complex heterogeneous systems, where masonry arches represent the main components. Thus, a realistic modelling of arches is vital for accurate assessment of masonry bridges. The authors have previously proposed and validated a detailed mesoscale description for masonry arches allowing for the actual masonry bond and the specific arch geometry including the case of skew arches. In this paper, the proposed mesoscale modelling strategy is used in a comprehensive numerical study to investigate the effects of various parameters, including masonry bond and defects in the brickwork, abutment stiffness and movements at the supports, which are usually disregarded in practical assessment of masonry arches and bridges. The results achieved show how these parameters affect the ultimate load capacity, failure mechanisms and initial stiffness of square and skew arches, where the use of detailed 3D mesoscale modelling is critical in providing accurate response predictions under a variety of loading conditions for which reduced models might provide incorrect results.

Experimental Response of Brick-Masonry Spandrels under In-Plane Cyclic Loading

AbstractThis paper investigates the behavior of spandrels in perforated walls of existing unreinforced masonry buildings. The main results of experimental tests carried out on full-scale brick-masonry coupling beams under in-plane cyclic loading are presented and critically discussed. The effectiveness of different strengthening techniques has been examined by testing damaged spandrels reinforced using steel ties or angles. The resistant mechanisms, the degradation of strength and stiffness, and the hysteretic energy dissipation capacity of the tested coupling beams have been analyzed. The experimental shear resistance of the unstrengthened and strengthened spandrels have been then compared against analytical predictions obtained by using expressions provided by current codes of practice. Finally, these analytical formulations calibrated against the experimental results have been employed to study the effects of the main spandrel geometrical characteristics. The results achieved provide relevant informati...

Robustness of Multistory Buildings with Masonry Infill

AbstractThis paper investigates the influence of unreinforced masonry panels on the robustness of multistory buildings under sudden column loss scenarios. A recently developed multilevel framework is employed to evaluate the resistance to progressive collapse under such scenarios, which is applied in this paper at story level allowing for the resistance of the floor system and the infill panels. The response of various structural components under pushdown deformation is obtained using high-fidelity finite-element analysis, where an accurate mesoscale description is utilized for the masonry infill, elastoplastic beam-column elements are used for the floor system, and component-based nonlinear mechanical models are employed for the joints. This methodology is applied to a 7-story composite steel-concrete benchmark building, where it is established that the use of masonry infill panels for exterior cladding can considerably increase progressive collapse resistance, even in the case of perforated walls. Furth...

Moment Redistribution in Continuous Steel-Concrete Composite Beams with Compact Cross Section

The paper investigates the design of continuous steel-concrete composite beams with compact cross section using the elastic analysis with limited redistribution. The permissible moment redistribution which satisfies the requirements of the ultimate limit state collapse and serviceability limit state crack width in the concrete slab was computed. An advanced finite element program accounting for all mechanical nonlinearities and time-dependent phenomena creep and shrinkage of concrete was used. An extensive parametric analysis aimed to determine the influence of several geometrical parameters on the permissible moment redistribution was carried out on propped cantilevers and fixed-end beams. The analyzed parameters include the shape of the steel profile, the ratio between the depths of concrete slab and steel beam, the steel to concrete area ratio, and the reinforcement percentage of the concrete slab. The analysis was limited to compact steel sections AISC 360-05 or class 1 steel sections Eurocode 3 and low ductility reinforcing steel elongation at maximum load ru=2.5%. The moment redistribution domain which satisfies the rotation compatibility in the critical sections, due to the attainment of the rupture of the reinforcement or the local buckling of the steel profile, and the control of cracking 0.3 mm in service was evaluated and compared with the limits recommended by current codes of practice. A proposal for the allowable moment redistri- bution domain according to the limits of the study was given. DOI: 10.1061/ASCEST.1943-541X.0000098 CE Database subject headings: Composite beams; Concrete; Steel; Continuous beams; Bending; Nonlinear analysis; Finite element method; Moment distribution; Cross sections. Author keywords: Composite beams; Concrete; Steel; Continuous beams; Bending moments; Nonlinear analysis; Finite-element method.

Pushdown Tests on Masonry Infilled Frames for Assessment of Building Robustness

AbstractThe research presented in this paper addresses the influence of nonstructural masonry infill on the resistance of multistory buildings to progressive collapse under sudden column loss scena...

Nonlinear Finite Element Analysis of Reinforced Concrete Flat Slabs Subjected to Reversed-Cyclic Loading

Flat slabs are only permitted to be used as gravity-load carrying systems in regions of high seismicity because of poor resistance to lateral deformation and punching shear under reversed cyclic loading. This paper considers the influence of reverse cyclic loading on the punching resistance of internal slab column connections without shear reinforcement. Currently, ACI 318-14 determines the deformation capacity of slab-column connections using a best-fit line based on test data from relatively thin slabs, with average thickness of 110 mm, and flexural reinforcement ratios of around 1%. Consequently, the ACI 318-14 (2014) design recommendations require further validation for slab thicknesses and reinforcement ratios outside this range. A possible tool for doing this is the mechanically-based critical shear crack theory (CSCT) of Muttoni (2008). The model is based on considerations of equilibrium and kinematics for an isolated axis-symmetrical slab. The model gives good predictions of punching resistance under concentric loading but its applicability to the design of flat slabs subject to reversed-cyclic loading requires further consideration. The paper presents the results of a parametric study which was carried out with the finite element program ATENA (Cervenka et al. 2007) in order to obtain an improved understanding of the influence of cyclic degradation on punching resistance. Maximum slab rotations are shown to increase under cyclic loading with a consequent degradation in unbalanced moment resistance and ultimate slab rotation. This finding is consistent with the predictions of the CSCT.

REALISTIC 3D NONLINEAR DYNAMIC ANALYSIS OF EXISTING AND RETROFITTED MULTI-STOREY RC BUILDINGS SUBJECT TO EARTHQUAKE LOADING

This paper presents a high fidelity numerical model developed to investigate the seismic performance of an original and retrofitted 10-storey reinforced concrete (RC) framed building. The analysed structure represents a typical existing building in Catania, Italy, which was designed according to old standards to resist gravity and wind loading but not earthquakes. The proposed numerical description adopts beam-column elements for beams and columns and special purpose shell elements for modelling RC floor slabs, both allowing for geometric and material nonlinearity. In order to model the influence of masonry infill, a novel macro-element is developed within a FE framework based on a discrete formulation. 3D nonlinear dynamic simulations are performed considering sets of natural accelerograms acting simultaneously along the two horizontal and the vertical directions and compatible with the design spectrum for the Near Collapse Limit State (NCLS). To improve computational efficiency, which is critical when investigating the nonlinear dynamic behaviour of large structures, the partitioning approach previously developed at Imperial College is adopted, enabling effective parallelisation on HPC systems. The numerical results obtained from the 3D nonlinear dynamic simulations are presented and discussed, focusing on the variation in time of the deformed shape, inter-storey drifts, plastic deformations and internal force distribution, considering or neglecting the infill panel contribution. The original structure showed a very poor seismic performance, where the consideration of the infill panel contribution leads to significant variation in the response. An effective strengthening solution utilising eccentric steel bracings with dissipative shear links is also illustrated and employed to retrofit the original structure. A detailed model of the retrofitting components is also proposed and implemented within the detailed model for the original building. The results of numerical simulations for the retrofitted structure confirm that the proposed solution significantly enhances the response under earthquake loading, allowing the structure to resist the design earthquake with only limited damage in the original RC beams and columns, highlighting the feasibility of retrofitting for this typical multi-storey RC building structure. 1685 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 1685-1699