D. De Domenico

LIMIT STATE EVALUATION OF STEEL-REINFORCED CONCRETE ELEMENTS BY VON MISES AND MENÉTREY–WILLAM-TYPE YIELD CRITERIA

An advanced version of a recently developed numerical limit analysis procedure for the prediction of peak loads and failure modes of steel-reinforced concrete elements is proposed. The modified procedure allows to take into account possible yielding of reinforcement thus capturing the actual behavior at the collapse of both steel and concrete. This implies a finite element (FE) modeling of the reinforced concrete (RC) elements in which concrete is governed by a Menetrey–Willam-type yield criterion, with cap in compression, while steel bars are governed by a von Mises yield criterion. The peak load of a wide range of RC structures whose behavior at ultimate state is dominated either by the concrete crushing or by the steel bars yielding is then predicted with a very good accuracy.

Earthquake Protection of Existing Structures with Limited Seismic Joint: Base Isolation with Supplemental Damping versus Rotational Inertia

Existing civil engineering structures having strategic importance, such as hospitals, fire stations, and power plants, often do not comply with seismic standards in force today, as they were designed and built based on past structural guidelines. On the other hand, due to their special importance, structural integrity of such buildings is of vital importance during and after earthquakes, which puts demands on strategies for their seismic protection. In this regard, seismic base isolation has been widely employed; however, the existing limited seismic joint between adjacent buildings may hamper this application because of the large displacements concentrated at the isolation floor. In this paper, we compare two possible remedies: the former is to provide supplemental damping in conventional base isolation systems and the latter consists in a combination of base isolation with supplemental rotational inertia. For the second strategy, a mechanical device, called inerter, is arranged in series with spring and dashpot elements to form the so-called tuned-mass-damper-inerter (TMDI) directly connected to an isolation floor. Several advantages of this second system as compared to the first one are outlined, especially with regard to the limitation of floor accelerations and interstory drifts, which may be an issue for nonstructural elements and equipment, in addition to disturbing occupants. Once the optimal design of the TMDI is established, possible implementation of this system into existing structures is discussed.

Limit Analysis on RC-Structures by a Multi-yield-criteria Numerical Approach

The present study proposes a multi-yield-criteria limit analysis numerical procedure for the prediction of peak loads and failure modes of reinforced concrete (RC) elements. The proposed procedure, which is a generalization of a previous one recently presented by the authors, is hereafter applied to structural elements reinforced either with traditional steel bars and stirrups or with fiber reinforced polymer (FRP) sheets used as strengthening system. The procedure allows to take into account the actual behaviour, at a state of incipient collapse, of steel, FRP and concrete by a finite element (FE) based plasticity approach where concrete is governed by a Menetrey-Willam-type yield criterion, FRP reinforcement obey to a Tsai-Wu-type yield criterion and steel reinforcement follow the von Mises yield criterion. To check the effectiveness and reliability of the numerically detected peak loads and failure modes a comparison with experimental laboratory findings, available in literature for large-scale specimens, is presented.

Limit Analysis: A Layered Approach for Composite Laminates

The present contribution summarizes the results of recent studies carried on by the authors in the last few years concerning the evaluation of the load bearing capacity of single- and multi-pin joints in composite orthotropic plates. The problem, tackled via limit analysis, employs a Tsai-Wu-type yield surface and a non standard treatment of limit analysis approach. Upper and lower bounds to the real peak load value are evaluated by two FE based numerical procedures predicting also the joint failure mode. The whole procedure is implemented at lamina level so taking into account some of the through thickness effects on the joint strength capabilities. A wide number of experimental findings, coming from laboratory tests on real prototypes and available in the relevant literature, is considered to validate, by comparison, the expounded methodology.

Limit analysis on FRP-strengthened RC members

Reinforced concrete (RC) members strengthened with externally bonded fiber-reinforced-polymer (FRP) plates are numerically investigated by a plasticity-based limit analysis approach. The key-concept of the present approach is to adopt proper constitutive models for concrete, steel reinforcement bars (re-bars) and FRP strengthening plates according to a multi-yield-criteria formulation. This allows the prediction of concrete crushing, steel bars yielding and FRP rupture that may occur at the ultimate limit state. To simulate such limit- state of the analysed elements, two iterative methods performing linear elastic analyses with adaptive elastic parameters and finite elements (FEs) description are employed. The peak loads and collapse mechanisms predicted for FRP-plated RC beams are validated by comparison with the corresponding experimental findings.

Experimental Investigation on the Mechanical Strength and Thermal Conductivity of Extrudable Foamed Concrete and Preliminary Views on Its Potential Application in 3D Printed Multilayer Insulating Panels

This contribution is focused on the properties of a particular type of foamed concrete, the extrudable foamed concrete, which is characterized by the dimensional stability in the green state, that is the ability to maintain its shape in the fresh state (green strength). In particular, after an overview of both the compressive and the indirect tensile strength, the effect of density on thermal conductivity values is presented. Interestingly, the thermal conductivity of this particular kind of lightweight cementitious material is lower compared to both classical foamed concrete and aerated autoclaved concrete (AAC) at comparable density. Moreover, the remarkable inherent green strength makes this material potentially suitable for in situ 3D printing applications in co-extruded elements with both thermal insulation and structural purposes.

NUMERICAL ASSESSMENT OF CONCAVE SLIDING ISOLATOR’S MECHANICAL BEHAVIOR UNDER BI-DIRECTIONAL MOTION

6th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering M. Papadrakakis, M. Fragiadakis (eds.) Rhodes Island, Greece, 15–17 June, 2017 NUMERICAL ASSESSMENT OF CONCAVE SLIDING ISOLATOR’S MECHANICAL BEHAVIOR UNDER BI-DIRECTIONAL MOTION Dario De Domenico, Giuseppe Ricciardi, and Gianmario Benzoni 1Department of Engineering, University of Messina Contrada Di Dio, 98166 Sant’Agata, Messina, Italy e-mail: dario.dedomenico@unirc.it, gricciardi@unime.it 2Department of Structural Engineering, University of California San Diego, La Jolla, California, 92093-0085, USA e-mail: gbenzoni@ucsd.edu