Gaetano Della Corte

Experimental analysis of steel dissipative bracing systems for seismic upgrading

Abstract Energy dissipating devices, such as metallic ductile dampers, could represent one reliable system for seismic performance upgrading of reinforced concrete (RC) structures. This paper illustrates the significant improvement to the seismic response of RC structures equipped with dissipative bracing systems, such as eccentric braces (EBs) and buckling restrained braces (BRBs). In fact, the results of experimental tests carried out on two similar two‐storey one‐bay RC structures, respectively equipped with EBs and BRBs, are described. Referring to EBs, 3 lateral loading tests have been performed. Each test is characterized by shear links with bolted end‐plate connections. Different design criteria have been applied in the design of the connections. In the first test, capacity design criteria have not been considered. In the second test, a capacity design criterion has been applied, with a link shear over‐strength factor equal to 1.5. In the third test, a design criterion similar to the one adopted fo...

Field Testing of All-Steel Buckling-Restrained Braces Applied to a Damaged Reinforced Concrete Building

AbstractThis paper reports the results of full-scale inelastic cyclic static tests of all-steel dismountable buckling restrained braces (BRBs) applied to an existing damaged reinforced concrete (RC) building. The two concepts set as the design targets for the prototype BRBs were to minimize interference with the functions and aesthetics of the existing building and to use an all-steel dismountable solution to allow for inspection of the yielding core after earthquakes. Two masonry infill panels (typical in RC buildings) were used to hide the braces and satisfy the first objective. Specially designed steel built-up shapes with bolted connections were used to satisfy the second objective. The design criteria and procedure adopted for the retrofitting design are first described, and a description of the BRB specimens and the experimental results follows.

Development of a Displacement-Based Design Method for Steel Dual Systems With Buckling-Restrained Braces and Moment-Resisting Frames

Dual systems can offer an attractive lateral force-resisting solution, combining individual systems in a complementary manner. A displacement based-design (DBD) method is proposed for steel dual systems incorporating moment-resisting frames (MRFs) and buckling-restrained braces (BRBs). The validity of the method is established through a verification study considering theoretical designs of 6-, 9-, 12-, and 18-story buildings and nonlinear time-history analysis (NTHA) using ten spectrum compatible accelerograms. The results show that the DBD method provides good control of displacements and drifts for the structures, although higher mode effects tend to become significant for the taller case studies. In addition to controlling peak deformations, the article illustrates how the inclusion of the MRFs in parallel to BRB systems can be an effective means of limiting residual deformations.

Development of a Displacement-Based Design Method for Steel Frame-RC Wall Buildings

A Displacement-Based Design (DBD) methodology for steel frame-RC wall structures has been proposed. The effectiveness of the methodology in limiting lateral displacements has been tested by designing a set of case studies. Their structural performance was investigated through nonlinear time-history analyses by using seven spectrum-compatible accelerograms. For the seismic intensity and modeling assumptions considered in this work, it is found that the proposed design methodology controls the lateral displacements of the buildings well.

Experimental Tests of a Real Building Seismically Retrofitted by Special Buckling‐Restrained Braces

Buckling Restrained Braces (BRBs), differently from conventional braces, do not exhibit appreciable difference between the tensile and compression capacity and no strength degradation of brace capacity under compressive and cyclic loading. Since lateral and local buckling behaviour modes are restrained, large inelastic capacities are attainable. Hence, BRBs may represent an efficient and reliable solution for reducing the seismic vulnerability of buildings. Results of experimental tests on the response of a real two‐story reinforced concrete (RC) building equipped with BRBs are presented and discussed. The considered BRBs are a special ‘only‐steel’ version of the more common ‘unbonded braces’. In particular, two different BRBs have been tested. Both of them are detachable “only‐steel” devices, consisting in a rectangular steel plate and a restraining steel sleeve. The latter is composed by two omega shapes which are bolted together. The main characteristic of the braces consists in the possibility to hide...

Design Tools for Bolted End-Plate Beam-to-Column Joints

Predicting the response of beam-to-column joints is essential to evaluate the response of moment frames. The well-known component method is based on a mechanical modelling of the joint, through joint subdivision into more elementary components subsequently reassembled together to obtain the whole joint characteristics. Significant advantages of the component method are the following: (i) the mechanics-based modelling approach; (ii) the easier general characteristics of components. However, the method is commonly perceived by practicing engineers as being too laborious for practical applications. Within this context, this paper summarizes the results of a theoretical study aiming to develop simplified analysis tools for bolted end-plate beam-to-column joints, based on the Eurocode 3 component method. The accuracy of the component method was first evaluated, by comparing theoretical predictions of the plastic resistance and initial stiffness with corresponding experimental data collected from the available literature. Subsequently, design/analysis charts were developed through a parametric application of the component method by means of automatic calculation tools. They are easy and quick tools to be used in the first phases of the design process, in order to identify joint configurations and geometrical properties satisfying specified joint structural performances. The parametric analysis allowed also identifying further simplified analytical tools, in the form of nondimensional equations for predicting quickly the joint structural properties. With reference to selected geometries, the approximate equations were verified to provide sufficiently accurate predictions of both the stiffness and the resistance of the examined beam-to-column joints.

Battened Steel Columns with Semi-Continuous Base Plate Connections: Experimental Results vs. Theoretical Predictions

The paper describes a comparison of experimental results and theoretical predictions regarding the lateral force-displacement response of built-up battened steel columns including semi-rigid and partial-strength base plate connections. Two specimens, representing samples of columns extracted from an existing industrial building, were fabricated and tested. Different types of both the battens and the base-plate connections characterized the two specimens. Preliminary lateral-loading tests in a range of elastic response, under varying levels of the concomitant axial force, allowed both exploring initial (elastic) stiffness and estimating yield displacements. Subsequently, cyclic lateral-loading tests with a given value of the axial force allowed investigating the restoring force characteristics in case of seismic actions. First, the paper describes and comments on the experimental performance of the two specimens. Second, numerical finite-element model predictions are illustrated and compared with experimental results. Third, based on the experimental results, as well as on the FE model analysis, the study looks for possible extensions and adaptations to current Eurocode 3 prediction models.

Modeling and Seismic Response Analysis of Italian Code-Conforming Single-Storey Steel Buildings

ABSTRACT This article describes the structural design, nonlinear modeling, and seismic analysis of prototype single-storey non-residential steel buildings made of moment-resisting portal frames in the transverse direction and concentric braces in the longitudinal direction. Various design parameters (building geometry, seismic hazard, foundation soil category) and different modeling assumptions (bare frame model, model including cladding elements, ground motions including vertical accelerations, and modeling uncertainties) were considered to investigate their effects on the simulated seismic performance.