Nunziante Squeglia

Influence of Tension Stiffening on the Flexural Stiffness of Reinforced Concrete Circular Sections

Within this paper, the assessment of tension stiffening effects on a reinforced concrete element with circular section subjected to axial and bending loads is presented. To this purpose, an enhancement of an analytical model already present within the actual technical literature is proposed. The accuracy of the enhanced method is assessed by comparing the experimental results carried out in past research and the numerical ones obtained by the model. Finally, a parametric study is executed in order to study the influence of axial compressive force on the flexural stiffness of reinforced concrete elements that are characterized by a circular section, comparing the secant stiffness evaluated at yielding and at maximum resistance, considering and not considering the effects of tension stiffness.

Role of Monitoring in Historical Building Restoration: The Case of Leaning Tower of Pisa

A short summary is presented of the studies and the actions of Committees appointed in past 50 years for the Tower of Pisa. The discussion first addresses the attempts carried out during the whole history of the Tower to measure its movements and the efforts made to understand the origin and causes of its inclination. A history of foundation rotation has been also deduced by means of a precise architectural survey, which has led to a diagnosis for the inclination and its increase in time. As a consequence, several hypotheses for its stabilization have been proposed. All the measures for leaning tower stabilization need the application of observational method for their implementation. The observational method is strictly based on a comprehensive monitoring system, both described in the second part of the paper. The aims are to stress the importance of a well-conceived monitoring system and to propose the extension of concept of monitoring to construction history details. The data and actions described are from the work carried out by committees appointed by Italian Government during the second half of 20th century, in particular by the committee chaired by Professor Jamiolkowski, appointed in 1991. The authors have collaborated with this committee since 1993, and they are still in charge of the monitoring and maintenance of the Tower of Pisa.

Behavior of the Leaning Tower of Pisa: Analysis of Experimental Data from Structural Dynamic Monitoring

Understanding the structural behavior of heritage buildings is usually a very complicated task because they typically present complex deterioration and damage patterns which cannot be fully evaluated by means of visual inspections. Moreover, the reliability of such constructions largely depends on different materials, structural components and details, the health of which is often unknown or affected by great uncertainties. In this regard, the experimental dynamic testing of heritage buildings and monuments subjected to ambient vibrations has become a valuable tool for their assessment because of the minimum interference with the structure. Traffic-induced vibrations are not always a feasible dynamic load for monumental buildings due to their very low intensity or owing to existing restrictions to road and rail traffic. On the other hand, the analysis of the experimental response under earthquakes can lead to more relevant information about the dynamic behavior of historic constructions, provided that the structure is equipped with a permanent sensor network. Within this framework, the present work illustrates preliminary results carried out from time and frequency domain analyses performed on the experimental dynamic response of the leaning tower of Pisa using seismic records. The main dynamic features of the monument have been identified, and then examined taking into account the seismic input and the soil-foundation-structure interaction.

Analysis Method for Laterally Loaded Pile Groups Using an Advanced Modeling of Reinforced Concrete Sections

A Boundary Element Method (BEM) approach was developed for the analysis of pile groups. The proposed method includes: the non-linear behavior of the soil by a hyperbolic modulus reduction curve; the non-linear response of reinforced concrete pile sections, also taking into account the influence of tension stiffening; the influence of suction by increasing the stiffness of shallow portions of soil and modeled using the Modified Kovacs model; pile group shadowing effect, modeled using an approach similar to that proposed in the Strain Wedge Model for pile groups analyses. The proposed BEM method saves computational effort compared to more sophisticated codes such as VERSAT-P3D, PLAXIS 3D and FLAC-3D, and provides reliable results using input data from a standard site investigation. The reliability of this method was verified by comparing results from data from full scale and centrifuge tests on single piles and pile groups. A comparison is presented between measured and computed data on a laterally loaded fixed-head pile group composed by reinforced concrete bored piles. The results of the proposed method are shown to be in good agreement with those obtained in situ.

A knowledge-based approach for the structural assessment of cultural heritage, a case study: La Sapienza Palace in Pisa

The full knowledge of the morphological evolution of an historical masonry building, defined more as ‘structural aggregate’ than as ‘single construction’, together with the analysis of the architectural, structural, geological and geotechnical aspects, allow the assessment of the static safety and seismic vulnerability of the complex and the design of retrofit interventions. In the present paper, a Knowledge-Based-Approach is applied to the historical building ‘Palazzo La Sapienza’ in Pisa, allowing to provide reliable results concerning the actual structural condition of the building avoiding the strong computational effort usually associated to the execution of refined numerical analyses. In case of complex buildings, characterized by a high heterogeneity of materials, structural typologies, geometries and so on, the adoption of a global model is not always useful to represent the effective structural behaviour. The proposed approach shows how a deep multidisciplinary knowledge of the construction can limit the use of cumbersome numerical modelling and analysis, however reaching reliable and accurate results usable also in the current practice.

Learning from the observation of failures

The Medicean Aqueduct of Pisa (Tuscany, Italy), is a relevant historical infrastructure built at the end of the XVI century, composed of 954 masonry arches over a total length of 6 km. Many of the arches are affected with several decay phenomena, which occurred during the years, due to ordinary and extraordinary causes. These have changed the original static arrangement, so that several arches are collapsed or degraded. It is worthwhile to point out that originally the foundation was supported by wooden piles that probably have been totally or partially deteriorated with time. A research activity is undergoing in order to understand the causes that induced the alteration of the original static model and to design necessary countermeasures. Anyway, the present paper illustrates the possible use of such a case history as educational material related to: durability, maintenance and preservation of historical heritage. The multidisciplinary nature of the case history is also pointed out. As for the research project the following activities have already been carried out by the research team, which consists of structural, geotechnical engineering and geophysicists: · analysis of the historic documentation; · accurate survey of the geometric characteristics of most of the structure above ground (the typology of the building materials and the decay phenomena were carefully catalogued); · geotechnical investigations (along the structure) consisting of boreholes, laboratory testing, piezocone testing and geophysical testing. On the contrary, it was not yet possible to assess the foundation geometry. Direct investigations are not possible for safety problems. Indirect investigations by means of geo-radar are planned at the end of the dry season. Since the masonry behaves according to a set of specific macro-elements, namely of rigid-bodies, the structural analysis mainly concerns the identification of these macro-elements and the related failure mechanisms activated by specific actions, such as the settlement of foundation or earthquakes. The structure has been studied with various types of analysis. Since the various aspects of the structural behaviour are captured by different methods, comprehensive answers are obtained only through a combined approach.

An example of teaching slope stability from true case hisrories: Three year experience

Part of the information summarized in this paper has already been published (Lo Presti 2013). The context (Study Course, Subject) within which the case history has been used and the case history itself has already been described. Such details are reported for a full understanding. Anyway the present paper mainly evaluates the effectiveness of using such a case history after an experience of three years. The use of case histories in classroom mainly involves an inductive teaching approach. This paper discusses the intrinsic advantages and possible drawbacks of such an inductive approach in the light of three year experience. More specifically, the paper illustrates an example of teaching the class of “slope stability” based on such methodology. The experience took place at the University of Pisa in the second tier degree of Civil Engineering of Infrastructures in 2010 and covered three academic years. The inductive teaching approach is very popular in the British/American Higher Education system. On the contrary it is not so popular in Latin countries like Italy. In order to make more clear the comprehension of this paper to the potential readers, information on the Higher Education system in Europe and specifically in Italy is also given.

An Innovative Method to Evaluate Degree of Compaction of River Embankments

The paper illustrates an innovative method to evaluate the degree of compaction of both existing and new river embankments after their completion. A tip resistance target—profile is inferred from laboratory tests in a mini calibration chamber (CC) using a mini CPT (cone penetration test). The “laboratory” tip resistance (qcLAB) is expressed as a function of the expected density and of the vertical—horizontal stress components. Such a dependence of qcLAB is obtained carrying out a number of repeated tests in the CC at given density and different consolidation stresses. In situ stresses are inferred by combining DMT (Marchetti Dilatomer) results and an estimate of the vertical stress component. A comparison between the qcLAB profile, from CC testing, and the qc, as inferred from in situ CPT, gives the possibility of assessing the density of existing embankments, while, for new embankments, the method defines the expected in situ qc for a given target density.

Liquefaction Potential Assessment Of Silty And Silty‐Sand Deposits: A Case Study

The paper shows a case study concerning the liquefaction potential assessment of deposits which mainly consist of non plastic silts and sands (FC>35 %,Ip<10%, CF negligible). The site under study has been characterized by means of in situ tests (CPTU, SPT and DPSH), boreholes and laboratory tests on undisturbed and remolded samples. More specifically, classification tests, cyclic undrained stress‐controlled triaxial tests and resonant column tests have been performed. Liquefaction susceptibility has been evaluated by means of several procedures prescribed by codes or available in technical literature. The evaluation of liquefaction potential has been carried out by means of three different procedure based on in situ and laboratory tests.