Domenico Raffaele

Designing Simply Supported R.C. Bridge Decks Subjected to In-Plane Actions: Strut-and-Tie Model Approach

The evaluation of the effects of seismic action on the decks of multi-girder bridges is often neglected by practitioners because it is thought that seismic code prescriptions (i.e., deck elastic behavior and minimum reinforcement) in addition to ultimate limit state reinforcement dimensioning for permanent and variable load, do not justify more accurate analyses aimed at checking and/or optimizing reinforcement layout. With the aim of verifying the reliability of this kind of approach, this article proposes a step-by-step procedure, based on the Strut-and-Tie Model, for the design of R.C. girder bridge decks subjected to in-plane seismic actions. As a first application, the proposed approach is used for a single span girder bridge deck. The influence on the model of geometry and supports of the bridge deck as well as the layout of girders and cross-beams is also investigated.

INFLUENCE OF RIGID FLOOR ASSUMPTION IN SEISMIC ANALYSIS OF RC EXISTING BUILDINGS

The study concerns with the seismic analysis of reinforced concrete (RC) building, with particular attention to the role played by floor system. The rigid-floor assumption is often used for RC existing buildings’ vulnerability assessment, in order to simplify the study of their structural behavior. Seismic codes (EC8, NZS4203, FEMA-273) provide a set of quantitative criteria related to deformation of diaphragm and average drift of the associated storey and qualitative criteria related to the shape of diaphragm. Despite in many cases this hypothesis can be considered sufficiently accurate, it is not always valid because it is related to several features of structure as floor geometry and materials, relative stiffness between floor system and vertical structural elements, shape of building, etc. In fact, unlike new structures, the main problem of RC existing buildings is not having geometrical and mechanical regular features (for example, in a ribbed slab, the irregular depth of the top concrete slab) as well as to present irregular dynamic parameters. When the floor system cannot be considered rigid, it may be studied as flexible slab with the increment of uncertainty related to stress states of structural elements. In order to understand how the floor system influences the structural behavior, it has been investigated the seismic performance of several applications, extrapolated from real RC existing buildings, through numerical methods, with and without the rigid-floor assumption. 3439 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 3439-3449

SIMPLIFIED CLOSED-FORM SOLUTION FOR THE DETERMINATION OF THE MOMENT-CURVATURE RESPONSE OF A CIRCULAR RC SECTION

A seismic vulnerability analysis of a multi-span simply supported bridge is often based on the seismic response of the most critical pier. This response is influenced by different collapse modes (flexural, shear, second order effects, lap-splice of longitudinal bars or their buckling). Among these the flexural behaviour is important and it’s known if the equivalent plastic hinge length and the Moment-Curvature law of the fixed end are given. This paper provides a closed-form dimensionless solution to obtain a 5 point Moment-Curvature diagram for circular RC section. The solution is based only on three parameters: dimensionless axial force, mechanical percentage of longitudinal reinforcement, geometrical percentage of transversal reinforcement. A numerical example is presented to test the solution comparing it with a FEM analysis.