nan Tavio

Experimental Behavior of Concrete Columns Confined by Welded Wire Fabric as Transverse Reinforcement under Axial Compression

This study examines the behavior of normal-strength concrete short columns confined by welded wire fabric (WWF) as transverse reinforcement under monotonically increasing concentric compression. The authors investigate the effects of volumetric ratio, spacing and lateral steel configuration, and distribution of longitudinal steel around the core perimeter or longitudinal reinforcement ratio on the uniaxial behavior of reinforced concrete columns. Tests were conducted on 22 short concrete columns reinforced with longitudinal steel and WWF or conventional ties under axial compression. The performance of columns laterally reinforced with WWF was compared with that of columns laterally reinforced with conventional ties. The findings show that WWF can be effective in confining the core concrete. Ductility increases of 130% and strength increases of at least 17% were found when compared with the corresponding specimens with conventional ties. The ductility of confined concrete columns improved with an increase of longitudinal reinforcement and decrease of transverse reinforcement spacing. Welded grids reduced the congestion of reinforcement and improved concrete quality in the members.

Behavior of rubber base isolator with various shape factors

The base isolator is the most effective technique in decreasing earthquake force that transmits to the building. This system is developed for earthquake protection by increasing the frequency of the structure away from the fundamental frequency of seismic excitation and fixed base structure. The layer number of rubber and reinforcement has an important influence to the vertical and horizontal behaviors of base isolation system. The parameters of shape factor denoted S are used to present the number of layers. A series finite element analysis (FEA) was carried out to study the influence of shape factor (S) of base isolation to the vertical and horizontal behaviors. Three dimensional models of base isolations with different shape factor values were created and analyzed by ANSYS. The models were subjected to axial and combination of vertical and horizontal loads to observe their vertical and horizontal behaviors, respectively. The results of the study indicate that the values of shape factor have no significant influence to the horizontal behavior due to constant thickness of overall rubber layers. On the contrary, the opposite conditions were found on their vertical behaviors. From the study, it can be concluded that the increase of shape factor value gave a considerable impact to the vertical strength of base isolation. In other words, it can be said that the increase of shape factor value also increases the vertical stiffness of base isolators.The base isolator is the most effective technique in decreasing earthquake force that transmits to the building. This system is developed for earthquake protection by increasing the frequency of the structure away from the fundamental frequency of seismic excitation and fixed base structure. The layer number of rubber and reinforcement has an important influence to the vertical and horizontal behaviors of base isolation system. The parameters of shape factor denoted S are used to present the number of layers. A series finite element analysis (FEA) was carried out to study the influence of shape factor (S) of base isolation to the vertical and horizontal behaviors. Three dimensional models of base isolations with different shape factor values were created and analyzed by ANSYS. The models were subjected to axial and combination of vertical and horizontal loads to observe their vertical and horizontal behaviors, respectively. The results of the study indicate that the values of shape factor have no signific...

Cumulative Ductility and Hysteretic Behavior of Small Buckling-Restrained Braces

Cumulative ductility is defined as a ratio of total energy to elastic energy which is dissipated by an element of the structural system during cyclic loading. An element of the structural system is categorized hysteretic if the cumulative ductility factor fulfills certain criteria. This study investigated both analytically and experimentally Small Buckling-Restrained Braces (SBRBs). The core of bracings was modeled using Menegotto-Pinto and bilinear functions. The restrained bracing members were in the shape of square hollow steel section. They were made of the assembly of two L-shaped steel sections. From the experimental study on four SBRB specimens, it was proven that the proposed SBRBs have performed relatively stable hysteretic curves up to two percent of strain and the cumulative ductility factor of 199–450. This value is sufficient for the Buckling-Restrained Brace (BRB) elements as elastoplastic structural components. The comparisons of the hysteretic behaviors resulted by SBRB specimens using the Menegotto-Pinto functions and experiments exhibited good agreements, while the amount of energy dissipated by the SBRB specimens using the bilinear model agreed well with the experimental results. Based on the behavior of the experimental hysteretic, implementing the proposed SBRBs as components in ductile truss system is recommended.