Search results for "concrete"

Analysis of a Collapsed Long-Span Reinforced Concrete Roof in South Italy: Design Mistakes and Material Degradation

2020

In 2004, during ordinary maintenance work, consisting of waterproofing a building located in the south of Italy, the long-span (14.5 m) in situ RC roof partially collapsed. The building, constructed in 1950, was in service as a cinema until 1967 and then utilized as a school until 1985. Lastly, it was a hotel until 2000. In 2004, when the building was not in service and was undergoing maintenance work, it partially collapsed under dead load. After the collapse, which involved a large portion of the roof, several beams, and two columns, the Italian court nominated an official technical consultant to investigate the direct and related causes of the failure. After the main causes were identifi…

Prediction Equations for Out-of-Plane Capacity of Unreinforced Masonry Infill Walls Based on a Macroelement Model Parametric Analysis

2021

In the seismic performance assessment of reinforced concrete (RC) frames, a reliable estimation of the capacity of unreinforced masonry (URM) infill walls is of utmost importance to ensure structural safety conditions. With particular attention to the out- of-plane (OoP) capacity of URM infill walls after in-plane (IP) damage, the issue of defining reliable analytical prediction models for the assessment of the capacity is an ongoing study. In this paper, empirical equations are proposed for the evaluation of the infilled frame’s OoP capacity, with or without IP damage, based on an extensive numerical parametric analysis, focusing on the influence of the key parameters that govern the mecha…

A semi-empirical stress-strain model for equivalent strut fiber-section modeling of infilled frames

2017

Infill-frame interaction is commonly modeled by means of equivalent strut macro-models. The main difficulty in using this phenomenological approach is to properly calibrate a force-displacement curve for the struts, as this depends not only on the geometrical and mechanical properties, but more specifically on the different potential damage mechanisms which may occur for the infill-frame system subject to lateral forces. If fiber-section elements are used as diagonal struts, the force-displacement curve is substituted by a stress-strain law. In both cases, the attribution of the inelastic law of the struts, based on a mechanical approaches, is not valid in general, as mechanical approaches …

EVALUATION OF FRAGILITY OF INFILLED FRAME STRUCTURES SUBJECT AFTERSHOCKS BY MEANS OF DOUBLE INCREMENTAL DYNAMIC ANALYSIS APPROACH

2018

The paper investigates the role of masonry infill walls on the seismic fragility of reinforced concrete structures subject to mainshock/aftershock sequences. An assessment framework aimed at determining aftershock fragility curves of bare frames and infilled frames is presented. The framework is based on a Double Incremental Dynamic Analysis (D-IDA) approach, which provides the adoption of ground motions defined by combining a fixed intensity mainshock with a set of variable intensity aftershocks. Mainshock (MS) intensity is scaled several times and combined with the same set of aftershocks (AS). Chord-rotation and shear limit states are specifically defined to consider the influence of mas…

Macroelement Model for In-Plane and Out-of-Plane Responses of Masonry Infills in Frame Structures

2018

A new macroelement model is presented in this paper for the simulation of the in-plane (IP) and out-of-plane (OOP) response of infilled frames subjected to seismic actions. The model consists of two diagonal, one horizontal, and one vertical struts. Each strut is represented by two fiber-section beam-column elements. The model is able to capture the arching action of the wall under an OOP load as well as the interaction between the IP and OOP actions. The proposed modeling approach is sufficiently simple and efficient that it can be used for the static or dynamic analysis of an entire structural system. An experimental validation has been carried out. A further numerical study performed wit…

Il recupero parziale di opere in muratura di interesse storico in zona sismica

2011

A simple model for the calculation of the axial load-carrying capacity of corroded RC columns

2015

In the present paper, a simplified model is used to determine the axial load-carrying capacity of compressed short reinforced concrete columns subjected to corrosion processes. The model considers members with circular and square cross-sections and accounts for—cover spalling, —concrete core confinement induced by transverse steel reinforcement, —buckling of longitudinal reinforcing bars. Strength reduction in concrete cover and core due to cracking induced by rust formation, reduction of steel area in longitudinal bars and transverse stirrups due to general and pitting corrosion and loss of confinement pressure are considered. The load-carrying capacity and load-axial strain curves here ge…

Increasing the shear capacity of reinforced concrete beams using pretensioned stainless steel ribbons

2017

In this work, the second part of an experimental campaign investigating the efficiency of an alternative retrofitting method for increasing the flexural and/or shear capacity in reinforced concrete beams, based on the use of prestressed stainless steel ribbons and steel angles, is presented and analytically reproduced. This group of tests focuses on the ability of the adopted retrofitting method to improve the shear strength and ultimate deformation of reinforced concrete structural elements. As described in a companion paper, the adopted retrofitting method is alternative to traditional techniques of reinforced concrete retrofitting, being easy to install and usually reversible, and charac…

Ultrasonic inspection for the detection of debonding in CFRP-reinforced concrete

2017

Fibre-reinforced plastic (FRP) composites are extensively used to retrofit civil structures. However, the quality and the characteristics of the bond between the FRP and the structure are critical to ensure the efficacy of the retrofit. For this reason, effective non-destructive evaluation (NDE) methods are often necessary to assess the bonding conditions. This article presents an ultrasonic technique for detecting defects at the FRP-substrate interface. The technique uses the Akaike Information Criterion, to detect automatically the onset of the ultrasonic signals, and the novel Equivalent Time Lenght (ETL) parameter, to quantify the energy of the propagating ultrasonic signals along the i…

Stress transfer and failure mechanisms in steel-concrete trussed beams: Experimental investigation on slab-thick and full-thick beams

2018

Abstract This study presents the results of an experimental investigation on semi-precast Hybrid Steel Trussed-Concrete Beams (HSTCBs) for analyzing the failure modes and the stress transfer mechanism between concrete and embedded steel elements (plate and truss). The available literature presents previous studies carried out by the authors mainly focused on the understanding of the local transfer mechanism by means of push-out tests. Conversely, in this paper original the results of laboratory tests conducted on six specimens of full-size HSTCBs subjected to four-point bending, with variation in the shear span, are reported on. From these results, the authors are able to assess the failure…