Simplified FEM modelling for the collapse assessment of a masonry vault

 

Simplified FEM modelling for the collapse assessment
of a masonry vault

Pierluigi Olmati
Sapienza University of Rome, Italy (now at TAISEI Corp., Tokyo, Japan)
pierluigi.olmati@gmail.com

Konstantinos Gkoumas
Sapienza University of Rome, Italy (now at European Commission, Joint Research Centre)
konstantinos.gkoumas@uniroma1.it, https://orcid.org/0000-0003-3833-6223

Franco Bontempi
Sapienza University of Rome, Italy
franco.bontempi@uniroma1.it, https://orcid.org/0000-0001-6377-7501

ABSTRACT. This study is motivated from the collapse of an old masonry building in the Southern Italy. FEM analyses are carried out focusing on the influence of the contrasting wall on the stability of the vault. In the analyses, the structure is subjected to a damage scenario on the contrasting wall due to a demolition project, and the consequence of the damage is evaluated using the explicit dynamic simulation made by Ls-Dyna®. A micro modelling technique (discrete FEM model) is adopted to model the masonry: the mortar is modelled by contact surfaces between the masonry units, which are explicitly modelled by blocks of meshes. This modelling technique is proven to be effective to predict the collapse behavior of the structure.

KEYWORDS. FEM; Masonry structures; Forensic investigations; Vault structures.

Coupling effects between wind and train transit induced fatigue damage in suspension bridges

Coupling effects between wind and train transit induced fatigue damage in suspension bridges

Petrini F 1), Olmati P 2), Bontempi F 1)

1) Department of Structural and Geotechnical Engineering, Sapienza University of Rome, Via Eudossiana 18, Rome, Italy

2) Taisei Corporation, Shinjuku Center Building, Nishi Shinjuku 1-25-1, Tokyo, Japan

Abstract 

Long-span steel suspension bridges develop significant vibrations under the effect of external time-variable loadings because their slenderness. This causes significant stresses variations that could induce fatigue problems in critical components of the bridge. The research outcome presented in this paper includes a fatigue analysis of a long suspension bridge with 3300 meters central suspended span under wind action and train transit. Special focus is made on the counterintuitive interaction effects between train and wind loads in terms of fatigue damage accumulation in the hanger ropes. In fact the coupling of the two actions is shown to have positive effects for some hangers in terms of damage accumulation. Fatigue damage is evaluated using a linear accumulation model (Palmgren-Miner rule), analyses are carried out in time domain by a three-dimensional non-linear finite element model of the bridge. Rational explanation regarding the above-mentioned counterintuitive behavior is given on the basis of the stress time histories obtained for pertinent hangers under the effects of wind and train as acting separately or simultaneously. The interaction between wind and train traffic loads can be critical for some hanger ropes therefore interaction phenomena within loads should be considered in the design.

Keywords: suspension bridges; fatigue analysis; wind-train interaction; damage accumulation; non-linearity