Bassam A. Izzuddin

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 Studies on Progressive Collapse Resistance of Steel Moment Frames under Localized Furnace Loading

AbstractThis paper presents experimental studies on the performance of planar moment steel frames with one column heated. The novelty of these tests is that the influences of key stages in the resp...

Mixed-Dimensional Coupling for Parallel Partitioned Nonlinear Finite-Element Analysis

AbstractThis paper presents a novel mixed-dimensional coupling method for parallel partitioned analysis, allowing efficient nonlinear structural analysis with selective deployment of differently dimensioned elements. With this method, a structural domain is decomposed into partitions that are processed in parallel using a recently developed dual super-element partitioning approach. Individual partitions consist exclusively of reduced dimensioned (1D) or higher dimensioned (3D continuum) elements, and coupling between 1D and 3D partitions is introduced at the boundary of 3D partitions, enabling a reduction in the communication overhead. Several examples are provided to verify the proposed approach and demonstrate its benefits for nonlinear structural analysis.

A 4-Node Co-Rotational Quadrilateral Composite Shell Element

A 4-node co-rotational quadrilateral composite shell element is presented. The local coordinate system of the element is a co-rotational framework defined by the two bisectors of the diagonal vectors generated from the four corner nodes and their cross product. Thus, the element rigid-body rotations are excluded in calculating the local nodal variables from the global nodal variables. Compared with other existing co-rotational finite-element formulations, the present element has two features: (i) The two smallest components of the mid-surface normal vector at each node are defined as the rotational variables, leading to the desired additive property for all nodal variables in a nonlinear incremental solution procedure; (ii) both element tangent stiffness matrices in the local and global coordinate systems are symmetric owing to the commutativity of the nodal variables in calculating the second derivatives of strain energy with respect to the local nodal variables and, through chain differentiation with respect to the global nodal variables. In the modeling of composite structures, the first-order shear deformable laminated plate theory is adopted in the local element formulation, where both the thickness deformation and the normal stress in the direction of the shell thickness are ignored, and an assumed strain method is employed to alleviate the membrane and shear locking phenomena. Several examples involving composite plates and shells with large displacements and large rotations are presented to testify to the reliability and convergence of the present formulation.

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...

Investigating the Need for Long Laps in Reinforced Concrete Elements

The current Eurocode 2 (EN 1992-1-1) detailing rules can lead to considerably greater lap and anchorage lengths than previous design recommendations such as the superseded British Standard BS 8110-1. Moreover, fib Model Code 2010 (MC 2010) requires even longer laps than EN 1992-1-1. This research is motivated by complaints from industry that designing to the current EN 1992-1-1 detailing rules leads to numerous construction issues such as reinforcement congestion, as well as cost and sustainability implications, with no apparent justification. This paper presents the experimental programme which was conducted by the authors with a view to justifying reduced lap lengths more commensurate with previously proven UK experience. To this end, a series of three point bending (3PB) and four point bending (4PB) tests were designed and tested in the Structures Laboratory at Imperial College London to investigate bond stress distributions along laps of different lengths consisting of lapped reinforcing bars of the same or different bar diameters. In particular, experiments were aimed at quantifying the effectiveness of very long laps in transferring forces between two lapped bars. The 3PB tests were aimed at investigating whether anchorage capacity of laps is enhanced at high shear locations.

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