Giuseppe Santarsiero

Cyclic Tests on External RC Beam-Column Joints: Role of Seismic Design Level and Axial Load Value on the Ultimate Capacity

A wide experimental program on beam-column RC joints carried out in the framework of the DPC-Reluis Project (DPC: Department of Civil Protection, Reluis: Network of University Laboratories of Earthquake Engineering) is presented. All the experimental tests were performed at the Laboratory of Structures of the University of Basilicata, Potenza, Italy. The main objective of the experimental campaign is to study and compare the post-elastic behavior of beam-column joints with different earthquake-resistant design levels, indicating the role of some structural parameters such as the axial load value acting on the column, beam dimensions, and steel type, on the joint performances and failure mechanism. The analyses have mainly been devoted to improving the assessment procedures regarding existing buildings but also to verifying the prediction capability of the capacity models relevant to beam-column joints contained in literature and in the new seismic codes. Following a short description of the experimental methodologies used in other campaigns, the experimental program is presented, providing a detailed description of the specimens and of the testing set-up. This is followed by a report of the main results of the cyclic tests performed on the beam-column specimens that highlight the role played by axial load and seismic design level in determining the failure mechanism and the global response of the joints.

Concrete Strength Variability in Italian RC Buildings: Analysis of a Large DataBase of Core Tests

The knowledge of the materials’ mechanical properties is a preliminary and important step in the seismic vulnerability assessment of existing buildings. In RC structures, the compressive strength of concrete can have a crucial role on the seismic performance and is usually difficult to estimate. Major seismic codes prescribe that concrete strength has to be determined essentially from in-situ and laboratory tests. In some cases such estimation can be complemented by default values in accordance to standards at the time of construction, therefore analysing the actual concrete properties typically found in RC existing buildings realized in different periods can make available useful data. To this end, in this paper attention has been addressed to public buildings, namely schools and hospitals. A large database made up of about 1500 test results on concrete cores extracted from about 300 RC public buildings located in Basilicata region (Italy), has been prepared and analysed. The relationships between the actual strength values (mean and dispersion) and the construction period of buildings have been studied. Theoretical distributions to approximate the discrete distributions of strength values in different construction periods have been determined, thus providing relevant data for the structural assessment of individual buildings and, especially, for large scale vulnerability evaluations.

Influence of Axial Load on the Seismic Behavior of RC Beam-Column Joints with Wide Beam

Beam-column joints can play a key role on the seismic behavior of reinforced concrete buildings. Until now studies and experimental investigations on this topic have been mainly focused on beam-column joints with stiff beams, i.e. beams with height larger than the thickness of the adjacent floor slab. However, especially in the European residential building stock, frame structures are often equipped with wide - therefore rather flexible - beams. However, not many studies have been devoted so far to this type of connection, therefore an experimental investigation on full scale beam-column joints with wide beam was planned at the University of Basilicata and is currently in progress. In the present paper the main results of two cyclic tests are reported and discussed specifically analyzing the role of the axial load applied to the column on the joint performances and damage mechanisms. Test results highlights that the axial load value has a significant influence of on deformation capacity and ductility behavior.

Seismic Tests on RC Building Exterior Joints with Wide Beams

Reliable assessment procedures of existing RC buildings are currently available, and have been introduced in the Italian and European codes reporting new rules for seismic analysis. However, further studies are required in order to further improve such procedures and, specifically, obtain more accurate data on the behavior of beam-column joints, whose role on the global behavior of framed RC buildings can be crucial. Until now studies on this issue have been mainly devoted to joint specimens with stiff beams, however frame structures having wide (also called flexible or flat) beams are widely used in the European residential building stock. To this purpose, given the lack of knowledge, an experimental investigation on full scale beam-column joints with wide beam has been planned and is currently in progress. In the present paper the main results of three tests are reported and discussed. The role of different earthquake resistant design levels on joint performances is pointed out.

Performance of the healthcare facilities during the 2016–2017 Central Italy seismic sequence

This paper presents an overview on the response of the healthcare system in the area mostly affected by the 2016 Central Italy earthquake based on specific surveys and information from local health authorities. The authors collected in the field information on the seismic response capacity of the healthcare system. They surveyed five hospital complexes from medium to small dimension whose maximum capacity was up to 50 beds. This type of hospitals are representative of those ones present in the small towns located along the Apennines mountain range, usually including few buildings (i.e. 3–5) constructed in different periods and with different structural types. In all the surveyed hospitals there were partially or totally unusable buildings causing severe limitations to the functionality of the healthcare services, forcing to move many patients to other hospitals and to stop outpatient treatment. This was due mainly to severe damage to non-structural components and, in some cases, to moderate damage to structural components. In the present paper, two hospital case studies, namely “Tolentino” and “San Severino” hospitals, both located in Marche region, are analysed and discussed in detail in order to better understand their performance to the earthquakes, by also estimating their seismic risk via simplified methods, including the WHO Safety Index and the Cosenza and Manfredi (in: Fajfar and Krawinkler (eds) Seismic design methodologies for the next generation of codes, Balkema, Rotterdam, 1997) damage index.

FINITE ELEMENT ANALYSIS OF EXTERNAL RC WIDE BEAM-COLUMN JOINTS PROVIDED WITH DIFFERENT DETAILING SOLUTIONS

Wide beams are part of the residential buildings’ construction habits in Italy as well as in other Mediterranean countries. In fact, undoubted advantages are provided by this type of beams with respect to architectural functionality and time-saving in formwork installation. However, in the design process of new RC buildings, some penalties in terms of ductility are prescribed in seismic codes when this type of beam is used. Previous studies demonstrated that the detailing of beam reinforcement can influence the response of external wide beam-column connections, especially for what concern the reinforcing bars bent outside the column width. In order to investigate the influence of this aspect on the global performance of external wide beam-column joints, the authors calibrated detailed finite element models based on the experimental results of cyclic tests carried out on two full-scale specimens. Beyond the detection of the main phenomena characterizing the subassemblages’ behavior, a parametric analysis has been performed to evaluate the influence of reinforcement amounts placed inside and outside the column core. Particularly, three values of the beam reinforcement area have been considered either placed inside or outside the column core, and the corresponding global lateral response curves of the beam-column joint have been obtained. It has been observed that in the cases where the additional amount of longitudinal reinforcement in the beam was placed inside the column core, both a more ductile behavior and a higher strength of the connection were obtained. This finding suggests that slip phenomena and torsion cracking occurred in the non-confined zone outside the column core, accounted for by the numerical model, can heavily influence the seismic behavior of this kind of beam-column joints even though they are seismically designed. 3992 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 3992-4006