Naohito Kawai

Collapsing process simulations of timber structures under dynamic loading III: numerical simulations of real-size wooden houses

In this study, we developed a new analysis method that enables numerical simulations of the collapse process of real-size wooden houses and evaluated the accuracy thereof by carrying out numerical simulations by shaking table tests. The distinct element method was adopted as the basic theory of our numerical analysis. This research is the first approach in which the extended distinct element method was used for Japanese timber post-and-beam construction. The size of the analysis model is a 5.5 m × 5.5 m, two-story real-size wooden house. The three analytical models were developed in terms of the strength of exterior mortar walls. The simulation results were compared with the shaking table test results. One of the collapsing processes of the numerical simulation corresponds well to the experiment results. Assessment of the possibility of collapse for real-size wooden houses was determined to be possible using our newly developed numerical analysis method.

Seismic and Wind Performance of Five-Storied Pagoda of Timber Heritage Structure

In Japan, there exist a total of 22 five-storied timber pagodas constructed before the middle of 19 centuries. All of those pagodas are registered as the important cultural heritages by Japanese Government, while some of them are listed in World Cultural Heritages such as Horyu-ji Temple’s Pagoda that was built in the end of 7th century. As those timber pagodas in seismic areas have survived against earthquakes during their long histories, their earthquake resistant capacity has been studied for a century. However, the actual dynamic behaviors of timber pagodas subjected to large earthquakes should be recorded to understand the seismic performance. Furthermore, an interesting structural issue has recently risen of wind resistant capacity of traditional five-storied timber pagodas, as such tall timber structures may be severely affected by strong wind. In order to record the actual dynamic behaviors during not only earthquakes but also typhoons, we have been conducting earthquake and wind monitoring at Hokekyou-ji Temple in Ichikawa City, next to Tokyo, which has survived for 4 centuries against not only large earthquakes but also severe typhoons. Hence, while the earthquake monitoring has been done by the conventional method utilizing accelerometers, the dynamic displacement of the structural response to wind has been directly measured by a new technique employing an image process system using LED makers and CCD camera, because the wind response includes much longer period component in general, therefore, it must be difficult to measure accurately the wind response by accelerometers. The scope of the present paper are 1) to review the past studies to understand the excellent earthquake resistance of five-storied timber pagodas, as well as, to introduce our research project of seismic and wind monitoring that has been successfully conducted since 2007, 2) to interpret those monitoring records which would be useful for understanding seismic and wind performance of the heritage timber pagodas that have survived for many centuries with describing the simulation analysis of seismic response, and 3) to show the long term monitoring records of the horizontal displacement of the heritage structure.

Timber–Reinforced Concrete Core Hybrid System: Shake Table Experimental Test

AbstractThe law to promote the use of wood in the construction industry was announced by the Japanese government in 2010. As a result of this initiative, timber and timber-based hybrid buildings are increasingly used in public buildings. As the buildings are located in high seismic zone areas, however, validation of the current design guideline was of paramount importance. This paper reports the design and a shake table test of timber frame–reinforced concrete (RC) core hybrid systems. Three specimens (S1, S2, and S3) are tested: S1 and S2 are both one-story buildings with a nailed plywood floor (flexible diaphragm) and a rigid RC floor (rigid diaphragm), respectively. S3 is a two-story building with a nailed plywood floor. Each specimen is tested with increasing magnitude of earthquake loading. The shake table test results showed that the adopted design guideline is sufficient. At higher seismic loads, however, the prevalent plan irregularity induced higher torsional demand damage at the RC core and timb...

Damage to Timber Buildings

The damage to timber buildings occurred over a wide swath from Tohoku down to northern Kanto. The cause of damage is divided either by ground motion or by tsunami. The damage due to ground motion is categorized by the main cause of damage, either the ground deformation including the liquefaction or the vibration of the superstructure.

AN ANALYTICAL STUDY ON LARGE DEFORMATION STATIC BEHAVIOR CONSIDERING BREAKING JOINTS OF WOOD HOUSES

This paper attempts to predict analytically large deformation static behaviors of two story wooden frame walls from the static performances of members and joints which compose wooden frame houses and walls. Wooden frame walls in this study have fragile joints which need to consider repeated contact problems, therefore extended distinct element method (EDEM) are applied which can consider these problems.110 joint specimens are tested. They are pressed in axial side, bent inside and outside. From the results of these tests and the past researches, the two story wooden frame walls are modeled. Especially, because of the brace failure modes of pressing side, four kinds of models are proposed for each wooden frame wall. The comparison of the results between EDEM analyses and tests indicates, 1) in the range of assumed brace failure mode, proposed models can predict test results, 2) by considering brace models in detail, proposed models can reproduce test results precisely.

AN EXPERIMENTAL STUDY ON LARGE DEFORMATION PERFORMANCES OF WOOD HOUSES CONSIDERING THE BREAK OF JOINTS

This paper attempts to clear large deformation behaviors of two story wooden frame houses and to predict large deformation behaviors of two story wooden frame houses from the summation of static performances of two story wooden frame walls that compose those houses. 4 types of wooden frame houses and walls are tested. The comparison of the results between two story wooden frame houses and the summation walls indicates, 1) until 1/30-1/25rad. deformation of 1st story, the summation of walls can predict structural performances of two story wooden frame houses without the influence of joint type of the column or the existences of boards, 2) after 1/25rad. deformation of 1st story, the structural performance of the summation of walls become different from that ones because failure modes of brace in walls is different from those of houses.