Optimization of a reinforced concrete structure subjected to dynamic wind action

This work proposes a methodology to optimize a reinforced concrete structure. For this, the Whale Optimization Algorithm (WOA) algorithm was used, an algorithm from the group of metaheuristic algorithms, which presents an easy computational implementation. As a study object, a frame structure adapted from a real reinforced concrete building was used, subjected to the dynamic action of artificially generated synoptic wind. The objective function is to reduce the volume of concrete of the structure. For that, the dimensions of the cross-sections were used as design variables, and the maximum displacement at the top imposed by the ASCE / SEI 7-10 standard as a lateral constraint, as well as the maximum story drift between floors. In addition to this structural optimization, it was also proposed the use and optimization of Tuned Mass Dampers (TMD), in different quantities, positions and parameters, improving the dynamic response of the reinforced concrete building. The results show that for this situation it was possible to reduce the concrete volume of the structure by approximately 24%, respecting the maximum limit of displacement at the top required by the standard.

Common irregularities and its effects on reinforced concrete building response

In most of the countries, the irregular building construction is popular for fulfilling both aesthetic and functional requirements. However, the evidence of past earthquakes in Nepal and the globe demonstrated the higher level of seismic vulnerability of the buildings due to irregularities. Considering this fact, the present study highlighted the common irregularities and its effect on reinforced concrete building response. The effect of structural irregularities was studied through numerical analysis. The geometrical, mass and stiffness irregularities were created by removing bays in different floor levels and removing the columns at different sections respectively. In this study, the numerical models were created in finite element program SAP2000. The structural performance was studied using both non-linear static pushover and dynamic time history analysis. The results indicate that the level of irregularities significantly influenced the behavior of structures.

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.

Seismic Performance Assessment of a Moment-Frame Reinforced Concrete Building Typology

This study covers the application of Static and Dynamic nonlinear analysis to an old moment-frame reinforced concrete building. The case study selected is a template one designed in 1982 without shear walls and built throughout Albanian region in the communism era using old standards (KTP 2-78). For the capacity calculation, Pushover analysis is performed using an inverse triangular load pattern. The demand calculation is conducted using Incremental Dynamic Analysis (IDA) as a method which provides the response behavior of the structure from the elastic range until collapse. For the dynamic analysis is used a set of 18 earthquakes with no marks of directivity. Limit states are defined for both Pushover and IDA based on the FEMA 356 guidelines. The mathematical model is prepared in the environment of Zeus-NL, a software developed especially for earthquake applications. The parameters defined for the IDA analysis are 5% damped first mode spectral acceleration (Sa(T1,5%)) for the intensity measure (IM) and maximum global drift ratio (ϴmax) for the damage measure (DM). In addition, limit states are selected for the pushover curve as Immediate Occupancy (IO), Life Safety (LS) and Collapse Prevention (CP). Similarly, for the IDA curve the limit states are selected as IO, CP and Global Instability (GI) based on FEMA guidelines. Furthermore, IDA curves are summarized into 16%, 50% and 84% fractiles as suggested in the literature. Additionally, a comparison between Pushover and IDA median (50% fractile) is shown from the same graph to illustrate the correlations between performance levels. Finally, structural performance is interpreted based on the outcomes.