Search results for " concrete"
showing 10 items of 190 documents
Case-studies of corroded reinforced concrete bridges in Southern Italy
2020
On Italian roads, a lot of reinforced concrete bridges were built in the 1950’s and 1960’s for short spans, before the advent of prefabricated structures. Many of these bridges, sited on principal or secondary roadways, show the effects of corrosion of reinforcements and high levels of damage, leading to the likelihood of achievement of the Ultimate Limit State, below the required performances of serviceability, especially in the case of Gerber saddles having strongly corroded reinforcements. Different case studies of bridges sited in Southern Italy (Sicily) are shown, allowing engineers to classify the main effects of damage in corroded structures with the Gerber static scheme (cantilever …
Simplified technique for constitutive analysis of SFRC
2014
Steel fibre reinforced concrete (SFRC) has become widespread material in areas such as underground shotcrete structures and industrial floors. However, due to the absence of material models of SFRC reliable for numerical analysis, application fields of this material are still limited. Due to interaction of concrete with fibres, a cracked section is able to carry a significant portion of tensile stresses, called the residual stresses. In present practices, residual stresses used for strength, deflection and crack width analysis are quantified by means of standard tests. However, interpretation of these test results is based on approximation using empirically deduced relationships, adequacy o…
LA CALUNNIA DIFENSIVA AI CONFINI DEL DIRITTO DI DIFESA: SULLA NECESSITÀ DI DISTINGUERE TRA CALUNNIA IMPLICITA E CALUNNIA-MEZZO
2020
La giurisprudenza sembra avere ormai individuato un criterio sufficientemente stabile per decidere quando la calunnia difensiva sia lecita e quando non lo sia: a tal fine, occorrerebbe verificare che tra calunnia e difesa corra (quella che i giudici chiamano) una stretta connessione funzionale; la quale, peraltro, dipenderebbe anche dalle modalità concrete della calunnia: quanto più dettagliata e credibile sia questa, tanto meno stretta sarebbe la sua connessione funzionale con la difesa. Nell’articolo si sostiene che, sebbene le soluzioni giurisprudenziali alle quali si giunge in applicazione di questo criterio appaiano generalmente condivisibili, il criterio stesso ne costituisce una gius…
Experimental investigation on the compressive behavior of short-term preloaded carbon fiber reinforced polymer-confined concrete columns
2017
Strengthening of concrete columns with fiber reinforced polymer sheets provides a good improvement to the existing structural members in terms of load and strain capacity due to the properties of the composite jacket. A proper knowledge of the load–strain response of the composite members is necessary to design retrofitting intervention of existing structures; however, so far the available design methods do not allow to take into account the effect of the possible presence of service loads on the compressive behavior of the reinforced columns. An experimental investigation on the compressive behavior of preloaded circular concrete columns reinforced with carbon fiber reinforced polymer was …
Hydraulic conductivity and strength of pervious concrete for deep trench drains
2019
Abstract Pervious concrete for deep trench drains, used to stabilise slopes, must meet many requirements, namely, adequate hydraulic conductivity, adequate shear strength a few days after pouring, capacity to act as a protective filter for soils in which the drain is installed, good resistance to clogging and adequate residual hydraulic conductivity. In current engineering practice, the composition of pervious concrete for drains is improperly selected according to criteria used for no-fines concrete for road pavements. To detect more suitable and specific criteria, a laboratory investigation has been conducted aimed at identifying the composition and the properties of pervious concrete sat…
Preventing early age chloride migration into low-carbon concrete
2019
The use of substituting cementitious materials (SCMs) to produce low-carbon concrete is escalating. This contributes to reducing the anthropogenic emission of CO2, and to reduce harmful temperature gradients during cement hydration in massive structures. Mature low-carbon concretes are known to perform well on both strength and durability. However, the maturity process is slow compared to that of standard concrete. Structures made from low-carbon concrete are subject to penetration of agents like chloride at early age, accelerating degrading processes. Chloride penetration is a major problem especially to infrastructure, due to seawater proximity and the use of de-icing agents. Solutions fo…
Pumice powder as filler of self-compacting concrete
2015
Abstract An experimental study on the rheological and mechanical properties of self-compacting concrete with pumice powder used as filler additive is presented. Self-compacting concrete (SCC) shows its peculiar characteristics in the fresh state and many researches have been developed with reference to its rheological characteristics paying attention to the techniques of self-compacting properties assessment. One of the most important aspect in concrete mix-design is the type and the amount of fillers with respect to water and cement: this amount has great influence not only on self-compacting properties (fluidity, segregation, etc.), but also on the mechanical properties of the mixture. Vo…
The Permeable Concrete: A Low Energy Consumption Solution for Deep Draining Trenches
2018
The reduction of pore water pressures is one of the very effective measures to improve the stability conditions of marginally stable water-bearing slopes or to stabilise landslides. For this purpose the trench drains have been used long since. Like filling material of deep trenches the permeable concrete can be effectively employed. It presents relatively high hydraulic conductivity, filtering capacity in order to prevent the internal erosion of the soil in which the trench drain is installed, enough residual hydraulic conductivity after possible clogging, sufficient shear strength after a short curing time to avoid the instabilisation of adjacent previously built panels or piles. Results o…
The façade-tower of Santa Maria delle Stelle Church in Comiso. Historical events, vulnerability and conservation strategy
2020
Dopo avere richiamato l’estesa vicenda storica della costruzione della chiesa Madre di Santa Maria delle Stelle a Comiso, iniziata nel 1736 e terminata due secoli dopo, il contributo è focalizzato sul tema del completamento della sua facciata con l’uso della struttura intelaia di calcestruzzo di cemento armato, progettata dall’ingegnere Santoro Secolo. In tempi più recenti, alcuni dissesti improvvisi hanno posto in evidenza il tema del rischio e la necessità di interventi per risanare la struttura architettonica. L’importanza del monitoraggio e della manutenzione, intesi come fondamentali strategie di conservazione, concludono l’articolo.
Stochastic Tension-Stiffening Approach for the Solution of Serviceability Problems in Reinforced Concrete: Constitutive Modeling
2015
A number of studies have indicated that the tension-stiffening law is an important input parameter in a numerical analysis of serviceability (deformations and cracking) problems of reinforced concrete (RC) structures. The stochastic nature of concrete cracking, which results in a large scatter of experimental results, renders the constitutive modeling a very difficult task. Even data obtained from short-term tests are to some degree uncertain due to time-dependent processes occurring in concrete, such as shrinkage and creep relaxation. This article provides statistical analysis tools that can be readily applied to engineering practice. Stochastic principles are applied to modeling of tensio…