Raffaele Pucinotti

TOP AND SEAT AND WEB ANGLE CONNECTIONS: PREDICTION VIA MECHANICAL MODEL

Abstract In this paper an extension of Eurocode 3 Annex J is presented to simulate the behaviour of beam-to-column joints with specific reference to top-and-seat and web angle connections. A simplified mechanical model is proposed for this type of connection. The extension of EC3 Annex J derives from a remark in a previous study, where was demonstrated that the contributions of web cleats are not always negligible. The simplified model, which is suggested herein, derives from an oversimplification of the Eurocode 3. In this paper the extension of EC3 Annex J and the simplified mechanical model are compared with experimental results. The application of the simplified model, and its comparisons with experimental curves and the Eurocode application, have revealed the excellent quality of the simplified model with specific reference to the connections analysed.

The dispersion of concrete compressive strength of existing buildings

The correct estimation of the compressive concrete strength plays a key role in the evaluation of the structural performance of existing RC buildings. Both Italian (NTC 2008) and European (EC8) Standards define different levels of knowledge according to the number of tests carried out on a building. They indicate a reduced value to assume in the analysis, defined as the mean value of the compressive strength, divided by a confidence factor. However, such a procedure completely neglects the dispersion of the test data, as represented by the high values of the coefficient of variation. Instead, this aspect is treated by FEMA 356 where a limit to the coefficient of variation was introduced. In this paper, with reference to a significant number of existing buildings located in Tuscany, the coefficient of variation (cov) of concrete strength is evaluated and the frequency of high cov values is determined. The dispersion of compressive strength, obtained by SonReb method, using correlation curves calibrated ad hoc on single building, shows that increasing the number of data for each building the coefficient of variation does not necessary decrease. Moreover, the strength value considered by EC8 in the analysis for a single building, i.e. the mean value of compressive strength, is often not conservative, while the approach provided by FEMA 356 is safer since it dependent on the cov itself.

Classing and Extracting Information from Radar Images

GPR techniques had been successfully using for many years to examine structures and materials from inside. They are based on the possibility of sending electromagnetic pulses and registering the echo time and the amplitude of the signals eventually back-scattered by the interface between propagation media of difierent dielectric constants. The result consists of some radar images (the so-called radargrammes), where incidental targets generate distinctive hyperbolic plots or discontinuities, as an indirect evidence of either changes in the properties, nature and composition of the medium or the presence of internal breaks. The present note aims at expounding some tests and preliminary results drawn by the employment of speciflc algorithms for automatically interpreting, classing and extracting explicit information from radargrammes, once these have been traced from raw radar data by an ad hoc application designed in the MatLab framework.

Seismic-Induced Fire Analysis of Steel-Concrete Composite Beam-to-Column Joints: Welded Solutions

A multi-objective design methodology dealing with seismic-induced fire on steel-concrete composite moment resisting frames endowed with concrete filled tubes (CFT) full strength joints is presented in this paper. In order to achieve these goals analytical and FE simulations including thermal analyses were carried out to design the proposed joints: this was followed by experimental tests under monotonic and cyclic loadings. Preliminary, seismic and fire analyses provided valuable information on the performance of moment resisting frames endowed with the chosen joint typology. A total of six specimens was designed and subjected to lateral loads. The specimens were subassemblages of interior beam-to-column joints connected by means of welded connections. Relevant experimental results are presented and commented. Furthermore, since the scope of the project was to promote joint typologies able to survive a seismic-induced fire, specimens were damaged by imposing monotonic loads equivalent to damage induced by seismic excitations, before being subjected to fire loadings. Thus, valuable information was obtained about the endurance of the proposed joint typology.

In situ concrete strength assessment: Part II – valuation of equivalent aggregate hardness by neuro-fuzzy techniques

In this paper a series of nondestructive and destructive laboratory tests is presented with the purpose of investigating the influence of aggregate hardness on the test results of Windsor probe test system. A series of specimens fabricated by aggregates having various values of Mohs hardness (i.e., aggregates of fluvial origin) and by aggregates with only a class of Mohs hardness (crushed aggregates) was prepared. During the concrete casting, a series of cubical specimens was prepared. Subsequently the Windsor probe system was applied to estimate the in situ strength of specimens. Then, from each specimen two cores were extracted. Finally, a comparison between penetration tests and core strengths was carried out. The selection of the more suitable choice of Mohs hardness was carried out by neuro-fuzzy techniques. Fuzzy surfaces techniques were exploited in order to reduce the computational complexity and to select the input set of our system. The comparison between nondestructive and destructive tests, conducted on cores from the specimens, gave evidence of the reliability of the technique.

In situ concrete strength assessment: Part I – the use of multiple combined nondestructive testing

A series of nondestructive tests was performed with the purpose of investigating the mechanical properties of the concrete employed in civil buildings. A series of specimens were prepared to correlate the in situ concrete strengths obtained by multiple combined nondestructive methods with the cubical and cylindrical strength obtained by destructive methods. The multiple combined methods (SonReb methods + Windsor Probe tests) were used for the quality control and strength estimation of the concrete. In particular, a series of specimens by aggregates having various Mohs hardness and by aggregates with only a class of Mohs hardness was prepared. The comparison between nondestructive and destructive tests, conduced on cores from the specimens, were evidenced, as the use of Windsor methods is generally justifiable only if a reliable correlation for a particular type of concrete is developed and as both the SonReb and SonReb-Win methods give resistance values that are close to the actual ones.

A Multi‐Objective Advanced Design Methodology of Composite Beam‐to‐Column Joints Subjected to Seismic and Fire Loads

A multi‐objective advanced design methodology dealing with seismic actions followed by fire on steel‐concrete composite full strength joints with concrete filled tubes is proposed in this paper. The specimens were designed in detail in order to exhibit a suitable fire behaviour after a severe earthquake. The major aspects of the cyclic behaviour of composite joints are presented and commented upon. The data obtained from monotonic and cyclic experimental tests have been used to calibrate a model of the joint in order to perform seismic simulations on several moment resisting frames. A hysteretic law was used to take into account the seismic degradation of the joints. Finally, fire tests were conducted with the objective to evaluate fire resistance of the connection already damaged by an earthquake. The experimental activity together with FE simulation demonstrated the adequacy of the advanced design methodology.

A mechanical model of semi-rigid beam-to-column steel joints

Publisher Summary The chapter presents a mechanical model for the inelastic analysis of semi-rigid and partial-strength top and seat angle bolted connections. The model is based on the same “component approach” introduced by the Eurocode 3. The proposed model maintains the Eurocode 3 approach but introduces a more refined modeling of the cleat-to-column interface, and introduces a different expression for the evaluation of the moment capacity of the joint which takes into account for the effect of the d/t (“d” is the diameter of the bolt connecting the angle to the column flange, “t” is the angle thickness), and r/t (“r” is the groove fillet radius). The proposed mechanical model is suitable to be included in existing code for the analysis of framed moment-resisting steel frames (MRSFs) including this kind of joint. The results of conducted analyses show that the model gives results that are in reasonable agreement with the experimental data and are more accurate than the results of the Eurocode 3-Annex J model.