Davorin Penava

Validation of a simplified micromodel for analysis of infilled RC frames exposed to cyclic lateral loads

An RC frame structure with masonry infill walls (“framed-masonry”) exposed to lateral loads acts as a composite structure. Numerical simulation of framed-masonry is difficult and generally unreliable due to many difficulties and uncertainties in its modelling. In this paper, we reviewed the usability of an advanced non-linear FEM computer program to accurately predict the behaviour of framed-masonry elements when exposed to cyclic lateral loading. Numerical results are validated against the test results of framed-masonry specimens, with and without openings. Initial simplified micromodels were calibrated by adjustment of the input parameters within the physically justifiable borders, in order to obtain the best correlation between the experimental and numerical results. It has been shown that the use of simplified micromodels for the investigation of composite masonry-infilled RC frames requires in-depth knowledge and engineering judgement in order to be used with confidence. Modelling problems were identified and explained in detail, which in turn offer an insight to practising engineers on how to deal with them.

Influence of Openings, With and Without Confinement, on Cyclic Response of Infilled R-C Frames — An Experimental Study

This article presents the experimental results of a study on reinforced-concrete frames infilled with masonry with openings. The frames were designed according to current European codes. They were built in a scale 1:2.5 and infilled with masonry walls. Mid-size window and door openings were located centrically and eccentrically and were executed with and without tie-columns around them. Presence of masonry infill, although not accounted for in design, improved the system behavior (increase in stiffness, strength and energy dissipation capacity) at drift levels of up to 1%. During the test, openings did not influence the initial stiffness and strength at low drift levels. Their presence became noticeable at higher drift levels, when they lowered the energy dissipation capacity of the system. The infill wall had a multiple failure mechanism that depended on the opening height and position. Tie-columns controlled the failure type, independent of the opening type, prevented out-of-plane failure of the infill, and increased the systems ductility. Negative effects of the infill on the frame were not observed. The infills contribution could be deemed positive as it enhanced the overall Structural Performance Level. Analytical expressions commonly used for infilled frames underestimate the infills contribution to strength and stiffness and overestimate the contribution of the bare frame.

DEVELOPMENT OF A THREE-DIMENSIONAL COMPUTATIONAL MODEL FOR THE IN-PLANE AND OUT-OF-PLANE ANALYSIS OF MASONRY-INFILLED REINFORCED CONCRETE FRAMES

Structural frames, constructed either by steel or reinforced concrete (RC), are often infilled with masonry panels. In design, they are usually treated as non-structural elements, and their interaction with the bounding frame is often ignored. However, recent studies have demonstrated that infilled frame can be superior to a bare frame in terms of stiffness, strength and energy dissipation, when the structure is subjected to strong lateral loads including earthquakes. Today, several models have been developed to evaluate infilled structures. Nevertheless, such models have been validated with limited experimental data, and they have demonstrated different performances when compared with test results. This paper presents the development of a three-dimensional computational model based on the finite element method (FEM) that has been used to study the in-plane and out-of-plane behaviour of masonry infilled RC frames containing openings. Masonry infill walls were modelled as an assemblage of stiff yet deformable bricks while mortar joints as zero thickness interfaces. Initially, the material and interface parameters were determined by carrying out a series of small scale tests. The computational model was then used to predict the in-plane and out-of-plane behaviour of a series of full scale infill wall panels constructed in the laboratory using a similar brick and mortar combination. From the results analysis, it was shown that the FE model was capable of capturing the mode of failure and the load carrying capacity of the masonry-infilled RC frame with sufficient accuracy.

Clay block masonry and mortar joint interlocking

Ako se pri izvedbi konstrukcijskog ziđa upotrebljevaju opecni zidni elementi s vertikalnim supljinama i mort opce namjene, tijekom ispunjavanja sAko se pri izvedbi konstrukcijskog ziđa upotrebljevaju opecni zidni elementi s vertikalnim supljinama i mort opce namjene, tijekom ispunjavanja sljubnica nastupa prodiranje morta u supljine zidnog elementa. Otpornost pri posmiku određuje se na jednak nacin za ziđe od punih ili supljih opecnih zidnih elemenata te stoga utjecaj međusobnog spoja zidnih elemenata i sljubnica morta nije uzet u obzir. Pomocu prostornih nelinearnih proracunskih modela i usporedbom s odzivom fizikalnih modela provjeren je utjecaj međusobnog spoja supljih zidnih elemenata i sljubnica morta na posmicnu nosivost.

Dynamic soil-structure analysis of tower-like structures using spectral elements

In this paper general equation system for linear dynamic soil-structure interaction (SSI) in frequency domain is presented. The main objective of the

Dynamic Tests of a Large-Scale Three-Story RC Structure with Masonry Infill Walls

ABSTRACT RC buildings with masonry infill walls are common throughout the world. There is uncertainty about the effect of the infill walls on the response of the building to earthquake demands. To shed light on this issue, a three-story, scaled reinforced concrete frame with masonry infill walls was subjected to two sequences of base motions in two series of tests. In Series 1, hollow masonry units were used. After completion of this series, the structure was repaired by replacing hollow masonry units with new solid units. Reinforced concrete confining elements were also added along the vertical edges of window and door openings in the first and second stories. The repaired structure was then tested with the same sequence of base motions in Series 2. On average, drift demands were 30% smaller in Series 2 and were nearly half what the drift demands were estimated to be for the bare RC frame alone. These results support the hypothesis that masonry infill panels can be used to control drift in low-rise structures, provided they do not cause column failures and provided they are restrained from out-of-plane collapse. Projections made based on the test results also support the idea that a Wall Index (ratio of masonry wall density to ten times the number of stories) exceeding 0.2% leads to acceptable earthquake response in low-rise buildings.

Three-dimensional micromodel of clay block masonry wall

In designing and implementing earthquake resistance for clay block masonry infill integrated into a structural frame, with or without openings, the infill wall should be taken into account. Presumably, simplified models, acceptable for practical use, could be applied for that purpose. However, the anisotropy of clay block masonry units, masonry mortar joints, and unit contact properties as well as the high variance of material properties limit their ability to describe the actual earthquake resistance of clay block masonry. In this work, we consider a three-dimensional micromodel of a clay block masonry wall, with the inclusion of masonry unit anisotropy and masonry mortar joint and unit contact properties. To avoid the excessive calibration procedure of the wall micromodel, the wall constituents were calibrated separately beforehand, which resulted in a high correlation of computational and experimental results without further need for calibration. Using a calibrated micromodel, the influence of variance in material properties on the walls resistance was investigated. The influence was showed not to be negligible, which may significantly affect the presumed behaviour of the whole structure.

Povezivanje u spoju mortom u ziđu od opečnih blokova

Ako se pri izvedbi konstrukcijskog ziđa upotrebljevaju opecni zidni elementi s vertikalnim supljinama i mort opce namjene, tijekom ispunjavanja sAko se pri izvedbi konstrukcijskog ziđa upotrebljevaju opecni zidni elementi s vertikalnim supljinama i mort opce namjene, tijekom ispunjavanja sljubnica nastupa prodiranje morta u supljine zidnog elementa. Otpornost pri posmiku određuje se na jednak nacin za ziđe od punih ili supljih opecnih zidnih elemenata te stoga utjecaj međusobnog spoja zidnih elemenata i sljubnica morta nije uzet u obzir. Pomocu prostornih nelinearnih proracunskih modela i usporedbom s odzivom fizikalnih modela provjeren je utjecaj međusobnog spoja supljih zidnih elemenata i sljubnica morta na posmicnu nosivost.

Šuplje ziđe od opeke i međusobni spoj sa sljubnicama morta

Ako se pri izvedbi konstrukcijskog ziđa upotrebljevaju opecni zidni elementi s vertikalnim supljinama i mort opce namjene, tijekom ispunjavanja sAko se pri izvedbi konstrukcijskog ziđa upotrebljevaju opecni zidni elementi s vertikalnim supljinama i mort opce namjene, tijekom ispunjavanja sljubnica nastupa prodiranje morta u supljine zidnog elementa. Otpornost pri posmiku određuje se na jednak nacin za ziđe od punih ili supljih opecnih zidnih elemenata te stoga utjecaj međusobnog spoja zidnih elemenata i sljubnica morta nije uzet u obzir. Pomocu prostornih nelinearnih proracunskih modela i usporedbom s odzivom fizikalnih modela provjeren je utjecaj međusobnog spoja supljih zidnih elemenata i sljubnica morta na posmicnu nosivost.

STRESS OF ANGLE SECTION SUBJECTED TO TRANSVERSAL LOADING ACTING OUT OF THE SHEAR CENTER

Angle or L-section bars are commonly used as non-structural elements in modern buildings, such as carriers of massive and expensive glass walls. While