Akihiko Kawano

A study on the static and impact structural behavior of concrete filled steel tubular members under Tsunami flotsam collision

The 2011 off the Pacific coast of Tohoku Earthquake triggered the Tsunami which caused massive great damage of the structural building either by the Tsunami waves themselves or by the Tsunami flotsam impact. With respect to the wave pressure, the loads by wave pressure are treated as statically equivalent loads. On the other hand, with respect to the collision of flotsam, the quantitative design method has not been established so far. The collision between Tsunami flotsam and concrete filled steel tubular (CFT) member is studied. Specimens consist of square, circular, and diamond cross-sectional shapes. The three dimensional finite element analysis (FEM) by MSC Marc Mentat (2012) was performed to evaluate static behavior of CFT members subjected to concentrated lateral load. The tip shape of lateral load is intended the collision with Tsunami flotsam. The solid element is used for steel tubes and infill concrete, respectively. The contact analysis between tip shapes of load and the steel as well as the co...

Finite Element Analysis of Vacant Tubular Members under Static Loading Considering the Tip Shapes of Load

FEM analysis of MSC. Marc program is used to simulate the models. Three-dimensional FEM model with contact analysis between deformable body of specimens and rigid body of load are studied. The isotropic material and The Von Mises yield criterion are used and kinematic hardening is used as a flow plasticity model. The effect of various shapes of loading tips is investigated. The load-displacement were established. The results of these works are expected to be a useful reference for analyzing structures under various shapes of loading tips either static or dynamic loading.

Damage to Steel Reinforced Concrete Buildings

Steering Committee on Steel-Concrete Composite Structure (SCCS), Architectural Institute of Japan, conducted a survey on the damage of Steel Reinforced Concrete (SRC) buildings in Sendai City. The SRC buildings suffered damage to nonstructural members in principle and little damage was observed in structural members. However, some buildings designed by old seismic design codes suffered severe damage to structural members. But they are not such serious damage as story collapse at the middle story of SRC buildings, which were found after the 1995 Great Hanshin earthquake. This chapter briefly describes damage to four SRC buildings which showed distinct types of damage.

Seismic Responses of High-Rise Buildings Subjected to Extreme Ground Motions of Tohoku Earthquake in Japan

Seismic performances of high-rise buildings are urgent to be studied given the background of the 2011 off the Pacific coast of Tohoku earthquake and probable long-period ground motions happened in subduction zone near east-coast of Japan. One 20 story frame of CFT and steel high-rise buildings were modeling, and seismic responses of models were simulated in FEM program with fiber model subjected to extreme ground motions recorded in the 2011 off the Pacific coast of Tohoku earthquake and the relevant artificial ground motions. Analysis results indicate that, the frame models could not satisfy the seismic demand under extreme ground motions. The CFT model has superior ultimate stability behavior than steel model as result of confinement effect of confined concrete to steel tubular. The phenomenon of deformation concentration along with vertical direction becomes more intense when the inputting acceleration level arrives extremely higher.

A Study on Connections of Concrete Filled Steel Tubes by Using Built-in Steel Bars

From 2006, authors started a series of experimental and analytical studies to establish a design method for a new connection system of concrete filled steel tube (CFT) by using built-in reinforcing steel bars (CFTR). Among the series, a pullout test of the built-in steel bars from the CFTRs has been early performed, which is orientated as a fundamental study for the connections of CFTR [1]. In the pullout test study, it is clarified that the influence of tube shapes (square and circular), the stress transfer capacities of bond by steel bars, ring bands in steel tubes and anchor plates of steel bars. The new connection system of CFTR may apply to an exposed-type CFT column base, where the built-in high strength steel bars contribute to transfer the axial force, bending moment and shear force from a CFT column to the foundation [2, 3]. The column base strength is much increased by the built-in steel bars. In other words, the built-in steel bars make the base plate and anchor bolts compact without any strength reduction in the column base. A stable elastic-plastic behavior is observed in the CFTR column base, and an evaluation method of the ultimate strengths is proposed for that. A further improved CFTR column base is the base without any base plate (non-base-plate CFTR column base), so that all of the stresses can be transferred through the built-in high strength steel bars [4]. A stable hysteretic behavior is observed in the column base, and the evaluation method of the ultimate strength is also proposed. It is noteworthy that the non-base-plate CFTR column base is applicable to the super high strength steel, because the base system does not require any full penetration welding, which sometimes causes brittle fracture in super high strength steel.

LATERAL-TORSIONAL BUCKLING OF TRUSSES WITH RECTANGULAR TUBE SECTIONS

Rigidly-jointed truss beam-columns which are composed of rectangular tubes by welding have the high strength of the lateral-torsional buckling, and can be more easily fabricated than trusses composed of circular tubes. However, the web members may cause local deformations in the flat plate elements of rectangular tube chords around the connections, which might reduce the buckling strength. From this point of view, experimental and theoretical investigations have been carried out. The paper presents the results, and then gives a more rational and economical design method instead of conventional methods which neglect the advantages of tubes.