dynamic behaviour of a retrofitted school building subjected to the after shock sequence of the 2016 central italy earthquake

Abstract This paper deals with the dynamic behaviour of a 1960s school building in Camerino subjected to moderate earthquakes belonging to the after-shock sequence of the 2016 Central Italy earthquake. The school structure, constituted by RC frames, was seismically retrofitted by means of "Dissipative Towers", an innovative system based on the use of external stiff steel truss towers equipped with dissipative dampers. Modal properties of the building after the retrofit have been determined through ambient vibration tests. After the main shock of the 2016 Central Italy earthquake, the building was instrumented with low-noise accelerometers and the dynamic behaviour of the structure during several aftershocks was recorded. Firstly, a numerical finite element model of the building is developed and calibrated on the basis of the ambient vibration measurements; then the registered dynamic response of the structure for the highest aftershock event (among the registered ones) is compared with that obtained numerically with the calibrated model. Results demonstrate the good agreement of the registered and predicted response

Assessment of seismic vulnerability of historical defensive walls

This paper presents a study on the behaviour of the walls of the Rocca Roveresca of Senigallia in Italy built in the XIV century on the ruins of a former Roman defensive struc-ture. This is a peculiar example of a small fortress that had undergone in the XV century im-portant modifications of the plant in order to enhance its defensive performances. A linear finite element model is first developed in order to understand the dynamic behaviour of a ge-neric portion of the wall and to detect the probable incipient failure mechanisms. A subse-quent static nonlinear analysis is carried out, with the same finite element model, to investigate the formation of the cracking layout and to detect the position of plastic hinges. The last analysis level is carried out with a tailored macro-element constituted by three bod-ies, namely the two external curtains and the inner fill for which a degradation of the behav-iour is considered. The results obtained demonstrates the efficiency of the wall against earthquakes characterized by return times typical for ultimate limit states. Same issues that deserve further investigation are highlighted

Creep in composite continuous beams I: theoretical treatment

In this first part of the paper, the viscoelastic analysis of composite steel-concrete continuous beams with flexible shear connectors is performed. The method proposed evaluated the stress redistribution between the concrete slab and the steel beam, and the evolution of the redundant restrain reactions, which occur with time as a result of creep and shrinkage of the concrete part. The effects produced both by geometric and static actions are considered. The mathematical formulation of the problem involves the equations of equilibrium, internal and external compatibility conditions and constitutive relationships. i.e. an elastic law for the steel part and an integral-type creep law for the concrete part. Thus, the problem for a continuous beam with r redundant reactions is governed by a coupled system of r + 5 equations, of which two are integral-differential-type equations. Successively, this system is resolved by numerical step-by-step techniques. Therefore, performing two standard discretizations, in time and along the beam axis a numeric algorithm is proposed

Construction sequence effects on externally prestressed composite girders

The authors examine composite steel-concrete beams prestressed by external cable, in order to analyze the influence of the most common construction and prestressing sequences, by evaluating both the initial linear behaviour and the non linear behaviour under increasing loads up to failure

Mixed Variational Formulation for the Aging Viscoelastic Problem

N.D