Search results for " ductility"

PBO textile embedded in FRCM for confinement of r.c. columns

2014

Results of experimental tests on two reinforced concrete columns confined with PBO-FRCM jacketing subject to axial load and bending moments are presented, showing the effectiveness of the confinement system. Comparison of test results against theoretical results derived by a fiber model stress the ability of the confinement system to enhance both strength and deformation capacity of the confined concrete

SHEAR STRENGTH DEGRADATION DUE TO FLEXURAL DUCTILITY DEMAND IN R.C. ELEMENTS

2014

A proposal is formulated that allows to evaluate the residual shear strength of reinforced concrete columns and beams for an assigned flexural ductility demand by limiting the range of the deviation angle between the inclinations of the yield  and the crack lines. In order to take into account the degradation due to cyclic loads, the reduction of the range of the deviation angle is related to the value of cinematic ductility

Seismic behavior of exterior RC beam-column joints without code-specified ties in the joint core

2021

Abstract Beam-column joint design for reinforced concrete (RC) buildings is a critical issue for modern earthquake engineering, because for these structural elements, the current codes provide several geometrical constraints and reinforcement provisions, which may be very complex to implement during the construction phase. To investigate how a construction error might influence the joint behavior, two identical full-scale exterior beam-column joints specimens are built, according to Italian Building Code specifications for the high ductility class, but without the required horizontal ties inside the joint panel. This construction error could be plausible because, according to the design dra…

Seismic response of steel frames with reduced beam sections

2003

This study concerns the effectiveness of weakening on the beams of fully and partially restrained connection steel frames in order to locate plastic hinges far from the joints. Two types of non-linear analysis, for geometry and constitutive law are developed: static pushover analysis, in which the structure is subjected to constant vertical loads and to horizontal loads linearly increasing up to collapse; and incremental dynamic analysis, in which the structure is subjected to uniformly scaled ground motions. Applications for four-bay frames with three and nine stories designed according to the EC3 code and for Italian 1st-category seismic areas are developed in order to evaluate the influe…

Strength and ductility of RC jacketed columns: A simplified analytical method

2016

Abstract Reinforced concrete (RC) jacketing is a common method for retrofitting existing columns with poor structural performance. It can be applied in two different ways: if the continuity of the jacket is ensured, the axial load of the column can be transferred to the jacket, which will be directly loaded; conversely, if no continuity is provided, the jacket will induce only confinement action. In both cases the strength and ductility evaluation is rather complex, due to the different physical phenomena included, such as confinement, core–jacket composite action, preload and buckling of longitudinal bars. Although different theoretical studies have been carried out to calculate the confin…

Flexural bearing capacity and related ductility demand for masonry sections under nonlinear constitutive law

2003

This paper aims at examining the maximum bearing capacity of rectangular masonry cross-sections subjected to eccentric compression, by assuming a nonlinear constitutive law characterized by two parameters defining stress-strain curve of the material. The variation of these parameters permits us to represent a wide variety of materials; therefore the ductility required of these materials in order for a section to achieve the maximum bending moment compatible with an average normal stress is also determined. The proposed approach can be utilized to evaluate the safety condition of masonry bearing walls, like those characterizing buildings of historical and/or monumental interest, for which th…

Minimum volume design of structures with constraints on ductility and stability

2014

Abstract A minimum volume design problem of elastic perfectly plastic frame structures subjected to different combinations of fixed and seismic loads is presented, in which the design variables are considered as appertaining alternatively to a continuous assigned range as well as to appropriate discrete sets. The structure is designed so as to behave elastically for the applied fixed loads, to shakedown in presence of serviceability seismic conditions and to prevent the instantaneous collapse for suitably chosen combinations of fixed and high seismic loadings. In order to avoid further undesired collapse modes, the P-Delta effects are considered and the structure is also constrained to prev…

Hardening structures isolated by double sliding devices: Seismic reliability-based design approach

2019

This study deals with seismic reliability-based design (SRBD) relationships in terms of behavior factors and displacement demands for hardening structures equipped with double friction pendu-lum system (DFPS) bearings. An equivalent 3dof system having a hardening post-yield slope is adopted to describe the superstructure behavior, whereas velocity-dependent laws are assumed to model the responses of the two surfaces of the DFPS. The yielding characteristics of the super-structures are defined for increasing behavior factors in compliance with the seismic hazard of L’Aquila site (Italy) and with NTC18 assuming a lifetime of 50 years. Considering several natural seismic records and building p…

Analysis and design of elastic plastic structures subjected to dynamic loads

In the last decades, the concept of “optimization” has reached considerable value in many different fields of scientific research and, in particular, it has assumed great importance in the field of structural mechanics. The present study describes and shows the scientific path followed in the three years of doctoral studies. The state of the art concerning the optimization of elastic plastic structures subjected to quasi-static loads was already well established at the beginning of the Ph.D. course. Actually, it was already faced the study of structures subjected to quasi-static cyclic loads able to ensure different structural behaviors in relation to different intensity levels of the appli…

A simplified method for ductility calculation in RC jacketed columns

2015

Reinforced concrete (RC) jacketing is a common method to retrofit existing columns with poor structural performance. It can be applied in two different ways: if the continuity of the jacket is ensured, the axial load of the column can be transferred to the jacket, which will be directly loaded; conversely, if no continuity is provided, the jacket induces only confinement action. In both cases the strength and ductility evaluation is rather complex, due to the different physical phenomena included, such as confinement, composite action core-jacket, preload, buckling of longitudinal bars. Although different theoretical studies have been carried out to calculate the confinement effects, a prac…