Parametric analysis on external dissipative link system for seismic protection of low rise R.C. buildings

The seismic rehabilitation of existing R.C. and masonry buildings is a topical issue in Civil Engineering. A useful technique consists in the introduction of the external bracing system. This kind of intervention can be improved through the introduction of dissipative links, investigated here with the help of some examples. The links are made of common steel profiles: length, geometry and positioning are considered as design parameters. A general procedure of link-bracing optimization is proposed by applying a set of identical external restraints. The adopted dissipative links allow a cheaper and more effective design both in terms of ULS and of DLS: the damages are addressed in a small area allowing easy replacement of the links in case of an earthquake

Seismic reinforcement of a R.C. school structure with strength irregularities throughout external bracing walls

The effect of irregularities due to the non-uniform distribution of material properties on structural elements of a significant real case is here investigated. Mechanical tests performed on a typical Italian reinforced concrete (r.c.) school building built in the 1960s showed irregularity in the distribution of compression strength in columns, even though the construction is featured by substantially symmetric distribution of the frames. Extreme scenarios in the distribution of irregularities in compression strength of concrete columns are analyzed, with the hypothesis of rigid or deformable slabs. The seismic analysis showed the influence of the response due to the irregular distributions of concrete strength. A proposal of equivalent "material eccentricity" is shown to account for the mentioned irregularity. Furthermore, the practical solution of reinforcement to mitigate the effects of irregularities is also described. It consists of couple of external r.c. walls stiffened by r.c. buttresses added to the building, connected by transverse slabs. An extensive reduction of material eccentricity is achieved, together with a relevant improvement in seismic capacity

Damage and restoration of historical urban walls: literature review and case of studies

Within this work, the causes of collapses and damages occurred in masonry artefacts have been evaluated to properly identify suitable monitoring and restoration methods. In this regard, a comprehensive literature review has been performed. Based on the results, moisture has been found to be a critical parameter, that affects the structural health of masonry artefacts. Various non-destructive methods were employed to measure moisture and monitor the materials involved, including Infrared Thermography, Electrical Resistivity Tomography, Ground Penetrating Radar, Laser Scanning and Digital Terrestrial Photogrammetry, Global Navigation Satellite Systems, Unilateral Nuclear Magnetic Resonance, Laser-Induced Fluorescence technique, Acoustic Imaging and Acoustic Tomography, Geographic Information System, on-site survey process and computer modeling of the structure with specific FEM software. Finally, the implementation of tie-beams, Fiber Reinforced Polymers layers, ventilation, draining systems, and high-quality materials are proposed as solutions for controlling the moisture effect and retrofitting

Rocking and kinematic analysis of two masonry church façades

The paper deals with the application of two methods of local analysis on masonry structures. Rocking and kinematic analysis are applied to two cases study: a gable of the Ica Cathedral that survived the 2007 Pisco earthquake and a church façade connected to transverse walls, which collapsed in the 2012 Emilia Romagna earthquake. The critical aspects of both analysis are discussed and the differences in the outputs commented. Being the two rigid blocks at height different from zero, an amplification factor of the seismic record was calculated for performing the rocking analysis. The gable is treated as free-standing block whereas the upper part of the church façade is analyzed in the rocking analysis by accounting for the rebound effect caused by the transverse walls, through the stiffness of a bed spring.The authors wish to thank Ing. Luciano Bellesia for his helpful cooperation. The activity is cosponsored by Consortium RELUIS – Masonry 2014

Graphical methods, kinematic and finite element analysis of the premilcuore masonry bridge

This paper presents the results of static and seismic vulnerability analyses performed on a single-span masonry bridge located in Northern Italy. The structure, dated back to the 17th century, is a bridge with single-span of about 16 meters and height of 8 meters, built with rubble and irregular masonry. A preliminary static analysis was performed on the bridge through traditional graphic approaches such as the Méry's rule and the Durand-Claye's method. Afterwards, a kinematic non-linear analysis was executed once the collapse mechanism under horizontal earthquake-type actions was identified. Finally, a static finite element analysis with brick elements was performed to state the seismic vulnerability of the bridge, by changing its mechanical properties to evaluate their influence on the structural response. Collapse load factors have been also computed considering non-uniform gravitational loads and horizontal settlements at the bridge foundations

Fast falling weight deflectometer method for condition assessment of rc bridges

In this paper, the use of Fast Falling Weight Deflectometer (Fast-FWD) is analyzed as a non-destructive and quick test procedure to evaluate the efficiency of short-span bridges. The FastFWD is an instrument that can produce a broadband dynamic force up to an impact value of 120 KN: The impact is constant and replicable, providing accurate action measures of bridge stiffness in a truly short period (30 ms). In this paper, a single-span reinforced concrete bridge is investigated, using the Fast-FWD. The considered bridge, approximately 12.0 m long and 15.5 m wide, was in critical condition. The bridge is in a suburban principal road near to the City of Cagliari in Sardinia (Italy), with an Annual Average Daily Traffic of 13,500 vehicles/day, and was suddenly closed, creating serious problems for urban mobility. In these conditions, the investigation through other standard techniques is time-consuming and labor intensive. For this reason, it is important to introduce methods that can be rapid, accurate and cost-efficient. In this paper, bridge stiffness values obtained during the in situ experimental campaign were compared with finite element models values. The Fast-FWD has the potential to provide engineering information that can help us to better understand bridge condition, in a rapid and cost-effective procedure

Modelling of Moisture Effect in Safety Evaluation of Soil-Interacting Masonry Wall Structures

This paper deals with analytical models of retaining walls interacting with soil, whose mechanical properties are influenced by penetrating moisture. Specifically, urban masonry walls are here considered. The proposed simplified procedure takes rainfalls as the intensity measure dependent on rain duration and return period. Growing levels of imbibition of the soil behind the wall determine a de-crease of the strength parameters of the soil. A geometry of the section at each step of imbibition is analyzed considering a set of soil layers with modified properties over time. The method is applied to a section of the Volterra historical urban walls named "Sperone" which was affected by a relevant collapse occurred in March 2014: a back analysis of the soil-structure section is also proposed to re-place the collapse

Soluzione di un incrocio con circolazione rotatoria a Lucca

Le rotatorie stradali: un biglietto da visita per il territori

Large-scale survey method for the integrity of historical urban walls: Application to the case of Volterra (Italy)

Several relevant collapses of historical urban walls happened in Tuscany in the last ten years, due to rainfalls. The wide extension of the walls, with difficulties of proper monitoring, joined with lack of maintenance, contributed to the failures. This recalled the attention on their vulnerability, in view to ensure a proper safety level and appropriate cultural heritage protection. In this paper, a method of extensive and quick structural survey to identify the mechanical characteristics of an historical urban wall path is proposed. It is based on geographic method of management of the territory (GIS database, satellite data). The data are obtained throughout a discretization of the walls in a wide set of vertical sections. A reduced subset of sections is directly surveyed, while the others are indirectly identified via numerical procedure, with the help of GIS data. A specific form to take note of the most relevant features is edited. The method is tested on the entire perimeter of the Middle Age walls of Volterra (2,6 km), affected by two relevant collapses in 2014. The procedure of survey is conceived to perform structural analysis to evaluate the vulnerability to landslides and earthquake risks, in view to determine restoration strategies and consolidation or monitoring programs