Study on overstrength and ductility of reinforced concrete building with different infill through nonlinear analysis

The building structure with infill wall shows higher global stiffness along with the uncertain behaviour during 2015 Gorkha earthquake. It significantly increased the collapse rate of structures during earthquakes. The response of buildings with different infills during seismic excitations is not completely accounted by current seismic codes in the region. On the other hand, due to the different geological region, availability of infill materials for reinforced concrete building also differs on region to region. In most of the situations the burnt clay brick, concrete blocks and stone block are used as infill materials during building construction. In this scenario, this study explores the importance of selection of right infill material for better seismic performance during earthquakes. For this, building constructed at Pokhara Metropolitan City is considered for case study. The structural model is prepared with and without considering infills. The solid, hollow concrete block and clay brick masonry are taken as infill material during analysis. The structural behaviour during earthquakes is studied with non-linear static pushover. The result shows that the hollow concrete block masonry infill (INHB) shows better structural performance compared to other infill types.

Multi-Platform Simulation of Infilled Shear-Critical Reinforced Concrete Frames Subjected to Earthquake Excitations

This paper proposes a multi-platform simulation method for seismic performance assessment of masonry infilled reinforced concrete (RC) frames, especially for those who tend to fail in shear during an earthquake due to inadequate reinforcing details. The method is based on a micro-macro modeling approach where a detailed finite element (FE) model of the RC frame is incorporated with a strut model of the infill wall. It takes advantage of the strut model in terms of computational efficiency and the FE model based on the Modified Compression Field Theory (MCFT) to capture the nonlinear behaviour of the RC frame with explicit modeling of the beam-column joint failure and shear failure of the frame. The proposed method is validated against previously tested frames subjected to lateral loads, and its advantages over the conventional struct models are demonstrated through both quasi-static and dynamic analyses.

Seismic Analysis of a Residential Building Considering Different Types of Opening Arrangement in the Infill Wall

Infill walls are inevitable components of any structure to create dispassion between interior space and external condition. In general, there are some prevalent openings inside the infill walls because of practical needs, architectural observations or aesthetic inspections. In current design practice, strength and inflexibility contribution of infill walls aren't thought of. However, the presence of infill walls may impact the seismic reaction of structures exposed to earthquake loads and cause a conduct which is not the same as that estimated for a bare frame. Additionally, partial openings inside infill walls are significant parameter prompting the seismic behaviour of infilled frames in this manner retreating lateral stiffness and strength. In this study is proposed to compare various models of buildings considering the openings (10% of surface area) at different locations in the infill walls for the seismic behaviour. A G+13 residential building is considered in Zone III with soil type II and analysis is carried out by Response Spectrum Method. Various parameters are considered such as Natural Time period, Base shear, Storey displacement, Storey drift and Storey stiffness were studied. The comparative study could simplify designers and code developers in selecting and recommending appropriate analytical models for estimating strength, stiffness, failure modes and other properties of infill frames with openings. Keywords: Residential Building, Openings Infill Wall, ETAB Software, Natural Time Period, Base Shear, Storey Shear, Storey Displacement, Storey Drift, Storey Stiffness.

Examination of Anchorage of Mesh Wire on Seismic Response of Infilled Walls in RC Frames

The infill walls may lose their positive effects during the first stages of earthquakes, either by leaving their plane or through breakage. That is why it is common to strengthen these walls before design earthquakes or to repair and strengthen them after suffering slight or moderate damage due to the occurrence of an earthquake. In this study, the effect of adding and strengthening these walls on the structural behavior of reinforced concrete structures was investigated. For this purpose, the infill walls were strengthened with a single mesh of reinforcement and covered with plaster. Five one-story, single bay and ½ scaled reinforced concrete frames were cast, one was built without infill, the second with a bare infill wall, and the other three with strengthened infill walls with anchorage of different diameters. All these specimens were tested under cyclic loading type reverse. The tests resulted in important relationships and curves, including the lateral load-lateral displacement, envelope curve-lateral load and lateral displacement, as well as stiffness- lateral displacement and others. Through these results, the effect of adding infill walls and the strengthening procedure of these walls on the structural behavior of the structures was discussed.

Evaluation of the period and soft story conditions of reinforced concrete buildings with and without infill walls

Since the ground floor of most of the buildings in our country is designed as a shop or ground floor (in the buildings created as a workplace), there is very little infill wall ratio on the ground floors due to architectural and functional reasons, and some of them do not even exist at all. However, infill walls significantly increase the horizontal rigidity and strength of the structure, thus causing a decrease in the period value that determines the earthquake loads that will affect the structure. However, the infill wall meets the first destructive forces of the earthquake, and during this time, it cracks and absorbs some of the earthquake energy. The structural system elements of the building (columns and shear walls) start to meet the earthquake forces only when the infill walls are damaged and fail. In this direction, the aim of this study is to investigate to what extent the amount of infill wall on the ground floor affects the period of the building, and whether there are soft storey irregularities in the building according to the change in the amount of infill wall on the ground floor. In this study, while there are infill walls on all floors and all axes of buildings of various heights (3, 6, 9 and 11 floors), the amount of infill walls in the x and y directions on the ground floors is reduced to a certain extent, and many models are created until the ground floor is completely without infill walls. All these models created were analyzed with the support of the SAP2000 program, and the period values were determined and examined according to the soft storey problems and compared with the case of the entire building with and without infill walls. In addition, it was examined whether the period formulas determined as a result of the studies and taking into account the infill wall give realistic results for the situation examined in this study.

Advanced Composite Retrofit of RC Columns and Frames with Prior Damages—Pseudodynamic Finite Element Analyses and Design Approaches

This study develops three-dimensional (3D) finite element (FE) models of composite retrofits in deficient reinforced concrete (RC) columns and frames. The aim is to investigate critical cases of RC columns with inadequate lap splices of bars or corroded steel reinforcements and the beneficial effects of external FRP jacketing to avoid their premature failure and structural collapse. Similarly, the RC-frame FE models explore the effects of an innovative intervention that includes an orthoblock brick infill wall and an advanced seismic joint made of highly deformable polymer at the boundary interface with the RC frame. The experimental validation of the technique in RC frames is presented in earlier published papers by the authors (as well as for a four-column structure), revealing the potential to extend the contribution of the infills at high displacement ductility levels of the frames, while exhibiting limited infill damages. The analytical results of the advanced FE models of RC columns and frames compare well with the available experimental results. Therefore, this study’s research extends to critical cases of FE models of RC frames with inadequate lap splices or corroded steel reinforcements, without or with brick wall infills with seismic joints. The advanced pseudodynamic analyses reveal that for different reinforcement detailing of RC columns, the effects of inadequate lap-spliced bars may be more detrimental in isolated RC columns than in RC frames. It seems that in RC frames, additional critical regions without lap splices are engaged and redistribution of damage is observed. The detrimental effects of corroded steel bars are somewhat greater in bare RC frames than in isolated RC columns, as all reinforcements in the frame are considered corroded. Further, all critical cases of RC frames with prior damages at risk of collapse may receive the innovative composite retrofit and achieve higher base shear load than the original RC frame without corroded or lap-spliced bars, at comparable top displacement ductility. Finally, the FE analyses are utilized to propose modified design equations for the shear strength and chord rotation in cases of failure of columns with deficiencies or prior damages in RC structures.