Effect of the openings on the seismic response of an infilled reinforced concrete structure

The seismic behavior of the infill masonry infill walls has a significant impact on the global response of reinforced concrete frame structures. One factor influencing its behavior is the existence of openings in the walls, such as doors and windows, which are crucial for the infill seismic performance. Although the numerical simulation of the seismic behavior of RC buildings with infill walls has evolved significantly in recent years in terms of micro- and macro-modelling, most of the existing studies are only related to infill walls without openings. Based on this motivation, four main objectives were defined for this research work: (i) present a simplified modeling approach and its calibration to simulate the seismic behavior of infill walls with central openings such as windows; (ii) evaluate the impact of the openings on the global seismic response of an RC building; (iii) study the impact of the irregular distribution of the infill walls (vertical and in-plane) on the global seismic response of an RC building; and (iv) study the impact of the central openings ratio (i.e., relative percentage between opening and infill wall area) on the global seismic response of an RC building structure. A four-story infilled RC building was used as a case study to perform parametric analyses investigating the impact of the masonry infill walls’ irregular distribution (vertical and in-plan) and their openings ratio. The results are discussed in terms of natural frequencies and vibration modes, initial lateral stiffness, and maximum lateral resistance. This study found that the openings caused a reduction in the natural frequencies of about 20% compared with the full infill (without openings). The openings did not modify the vibration modes. In addition, the openings reduced the initial stiffness by about 20% compared with the model without openings. The maximum strength increased about 50% with the infill walls, but this was reduced by the openings by 20%.publishe

Strengthening of structures damaged by the Azores earthquake of 1998

This paper addresses repair and strengthening techniques proposed for the rehabilitation of small buildings on Faial Island, Azores, hit and damaged by the Azores earthquake on 9 July 1998. A brief description is provided of the construction type and practice in the island, highlighting the main type of houses. Due to the lack of relevant information concerning construction material data, experimental tests were performed in situ, involving static and dynamic measurements. The experimental campaign is addressed and the main results are highlighted. These results served as input data for numerical seismic analysis of a number of house structures, which provided validation support for the design of strengthening strategies. One of such analysis is presented herein. The basic aspects of the proposed strengthening techniques are briefly presented and discussed, focusing on their practical application

A review of the performance of infilled RC structures in recent earthquakes

The primary objective is to present the most representative types of damage observed in reinforced concrete (RC) structures due to earthquakes. Those damages are divided according to the ten most representative types. Examples and the main reasons that could trigger each failure mechanism are presented. The definition of these damage types is supported by post-earthquake damage reconnaissance missions in Sichuan (China) in 2008, L’Aquila (Italy) in 2009, Lorca (Spain) in 2011, Emilia-Romagna (Italy) in 2012, Gorkha (Nepal) in 2015, Muisne (Ecuador) in 2016 and Chiapas (Mexico) in 2017. An extensive discussion is presented concerning the infill walls’ seismic behaviour and their interaction with the RC structural elements. The presentation of the significant learnings and findings concerning the typical damage herein presented and discussed are compared with the common Southern European construction practice. The impact of the infill walls on the rehabilitation costs of damaged RC buildings is also studied. These costs are compared to those related to the structural damage and rehabilitation of the entire building structure to understand the impact of the infill walls. Finally, a case study is presented to study the effect of implementing simplified retrofitting strategies to prevent the soft-storey mechanism, one of the most common problems observed in past earthquake events.publishe

Influence of seismic loading on axial load variation in reinforced concrete columns

Experimental tests demonstrated the importance of the axial load variation in the seismic response of RC columns, namely, through the reduction in the strength capacity, reduced deformation capacity, and reduced energy dissipation capacity. Thus, this manuscript aims to study the axial load variability of RC columns, according to the plan and height disposition, and assess the relationship between the corresponding column flexure capacity and its influence on the global response of the structure. Hence, three RC structures were modeled using the software SeismoStruct and subjected to non-linear static pushover and dynamic analyses. According to the results, which are assessed in terms of capacity curves, axial load variation, and story/global shear capacity of each model, it can be concluded that the axial load variation is higher in the bottom storys and decreases with the story height of the structure. As observed, the corner columns reached a higher axial load variation than the façade and central columns

A experimental characterization of seismic plus thermal energy retrofitting techniques for masonry infill walls

The renovation and refurbishment of existing envelopes of existing RC buildings are usually performed, focusing only on improving their structural or thermal energy characteristics. However, international concern about the sustainability and resilience of existing building structures demands the rethinking of retrofitting techniques that tackle both aspects simultaneously, making the envelopes more energy efficient and seismic safer. Based on this motivation, a testing campaign was carried out to validate the efficiency of novel seismic plus energy retrofitting techniques. Five full-scale specimens were built, three of them with seismic plus energy retrofitting and two of them with solutions developed to improve each case. The five specimens were subjected to pure OOP quasi-static loadings until reached the collapse or partial collapse. The results of the retrofitted walls were compared with a reference specimen (i.e. non-retrofitted) to assess the efficiency of each solution. From the results, it was observed that the novel combined retrofitting can improve the thermal transmittance of the wall by around 70%, and the strength and deformation capacity by up to 125% and 340%, respectively.publishe

Inspecção e avaliação estrutural de pontes: algumas contribuições da FEUP

A presente comunicação tem como objectivo a apresentação de algumas contribuições do Departamento de Engenharia Civil da Faculdade de Engenharia da Universidade do Porto (DEC-FEUP) no domínio da inspecção e de avaliação estrutural de pontes. Discutem-se algumas questões relativas a linguagem e conceitos neste domínio e referem-se casos de fichas de inspecção que têm sido propostas e usadas. Apresenta-se sumariamente alguns exemplos de trabalhos inspecção e avaliação estrutural que têm sido realizados no DEC-FEUP

Comportamento cíclico de pilares de betão armado sujeitos à flexão bi-axial: estudo experimental

Sismos recentes têm mostrado que a investigação em engenharia sísmica deve dar especial atenção à avaliação da vulnerabilidade das construções existentes, frequentemente desprovidas de adequada resistência sísmica, tal como acontece em edifícios de betão armado (BA) de muitas cidades em países do sul da Europa, entre os quais Portugal. O comportamento de elementos de betão armado carregados axialmente e sujeitos a esforços de flexão biaxial é reconhecido como um assunto fundamental e não suficientemte estudado, revelandose muito importante em virtude da real resposta tridimensional dos edificios de betão armado e do facto de se reconhecer que as solicitações bidireccionais dos elementos de betão armado tendem a aumentar a degradação de rigidez e a reduzir a sua capacidade resistente para carregamentos cíclicos. No presente estudo apresentam-se os resultados de uma campanha de ensaios realizada sobre pilares rectangulares sujeitos à flexão cíclica uniaxial e biaxial. É realizada uma análise dos resultados em termos de comportamento global dos pilares, da evolução do dano, das componentes de deformação, da dissipação de energia

Identificação dinâmica e análise do comportamento sísmico de um quarteirão localizado na Cidade da Horta - Ilha do Faial

O presente artigo aborda uma parte de um trabalho em curso relativo à análise do comportamento sísmico de todo um quarteirão da cidade da Horta, na ilha do Faial, Açores, afectado pelo sismo de 9 de Julho de 1998. Apresenta-se o resultado de uma análise numérica preliminar para aferir a sensibilidade ao tipo de modelação e às propriedades dos materiais, realizada ao nível local de uma casa e também ao nível global do quarteirão. Após uma identificação prévia das zonas mais vulneráveis do quarteirão, refere-se a realização de uma campanha experimental de medições de vibração ambiental in situ, cujos resultados permitiram obter frequências e modos de vibração de alguns edifícios do quarteirão e calibrar as modelações numéricas que aqui se apresentam

Structural reliability assessment based on optical monitoring system: case study

ABSTRACT Optical systems are recognized to be an important tool for structural health monitoring, especially for real time safety assessment, due to simplified system configuration and low cost when compared to regular systems, namely electrical systems. This work aims to present a case study on structural health monitoring focused on reliability assessment and applying data collected by a simplified optical sensing system. This way, an elevated reinforced concrete water reservoir was instrumented with a bi-axial optical accelerometer and monitored since January 2014. Taking into account acceleration data, the natural frequencies and relative displacements were estimated. The reliability analysis was performed based on generalized extreme values distribution (GEV) and the results were employed to build a forecast of the reliability of the water elevated reservoir for the next 100 years. The results showed that the optical system combined with GEV analysis, implemented in this experimental work, can provide adequate data for structural reliability assessment