This study investigated the deformation of the structural members constituting the wall formwork due to the lateral pressure of fresh concrete in the conventional formwork method using plywood sheathing. The primary variables in this experiment were the layout of separators, and the material and spacing of vertical studs in the wall formwork. Results of the experiment demonstrated that for formworks with identical separator layouts and vertical stud spacing, the total deformation of the formwork using steel studs was about two times less than that of the formwork using wood studs.
This paper describes the effects of subsurface structure on ground motions and nonlinear responses of super high-rise RC buildings to pulse-like ground motions using subsurface structure models from the seismic bedrock to the ground surface in the Tokyo Metropolitan area. Amplification of pulse-like ground motions and relatively large story drift of upper buildings are remarkably seen in the area between Sumida and Edo Rivers. The shallow part of subsurface structure is dominant for the ground motion amplification and consequent structural responses rather than deep part mainly due to nonlinear soil responses in the low Vs sediments.
There are few cases where the evaluation of soil springs used in the seismic design of super high-rise buildings has been verified by actual measurement. In addition, there are few studies that deal with the temporal variation of the nonlinear behavior of soil springs using observation records. In this study, rocking soil springs in super high-rise residential buildings are evaluated by actual measurement using strong motion observation records including large amplitude levels. In addition, the effect of nonlinearity of rocking soil springs on the structural response during large earthquakes is evaluated.
An experiment was conducted in which the surface pressure was applied to a PTFE sliding bearing used for elastic sliding bearings and the static friction coefficient was measured after a waiting time. According to the results, we proposed a relational expression by multiple regression analysis with waiting time, surface pressure and temperature as variables, and showed that the calculated value by the proposed formula corresponds well with the experimental value. In addition, the consideration of using the proposed formula in the actual design and an example of the restoring force model were shown that the design method was proposed.
Tuned mass dampers exhibit high performance when optimally tuned to a structure. However, their damping performance decreases once the natural period of the structure is elongated due to the elastic-plastic response under strong earthquakes. In this paper, long-duration earthquake ground motions are substituted by the multi impulse and the optimal characteristics of the tuned inertial mass dampers are derived numerically. This substitution allows us to avoid conducting repetitive computation of complicated and time-consuming nonlinear time-history response analysis. An ideal drift response curve is proposed for structures subjected to multilevel seismic ground motion inputs and an optimal design method is presented.
When steel piles experience the higher axial compression force caused by the superstructure’s overturning moment in the liquefied soil, the pile’s flexural buckling may occur. In previous papers, the steel piles’ collapse mechanism is presented. On the other hand, the CFT piles may fail when they experience the significant earthquake in the soft ground. In this paper, the centrifugal tests of the superstructure, the CFT piles and the liquefied soil system are conducted and the piles’ ultimate mechanism is clarified. Moreover, the pile’s ultimate strength is evaluated using M-N interaction curves, to which the pile’s elasto-plastic buckling strength is applied.
Modeling on restoring force characteristics of unbonded precast prestressed concrete beams with widened beam end was proposed in this paper. One model has rotational springs at both the outer end of the general and widened beam end, and another model has one spring with a rigid zone at the end. Ten unbonded precast prestressed concrete beams whose parameters are beam longitudinal rebar amount, widened beam end size, prestressing force, etc., were constructed and tested. The proposed method captured the restoring force characteristics of the test results in good accuracy.
While BRBs using laminated timber as a restrainer have been widely studied, timber restrainers have lower stiffness than steel restrainers with higher risk of fragile crack failure, it is necessary to consider the safety factor of global buckling, global stability of restrainer ends and local bulging failure at restrainer. In this study, a wide range of mock-up loading tests on BRBs with timber restrainer were carried out with different core-to-restraint compositions, in-plane and out-of-plane clearances, with and without core additional steel plates, and with different boundary conditions. Their exhibited failure modes are carefully studied and evaluation methods are proposed.
In this paper, the structural behavior of beam joint using bearing bolts was investigated by the bending test. From test results, the slip behavior of beam joint using bearing bolts against the linear behavior of that using high strength bolts, the rotation angle of beam joint increases with the increase of the clearance of bolt holes and the decrease of beam depth were confirmed. In addition, the rotation angle of beam joint using bearing bolts was evaluated accounting for the slip, the shifting range from the contact to pressure state and the rotational stiffness under the pressure.
This paper presents design recommendations for optimal seismic response control of damped braced tube system with focus on cost performance of introducing energy-dissipation devices. According to the results, 1) braced tube structure should be designed so that coupled-shear-wall-like vibration modes are predominant to obtain highly damping ratio and better cost performance of dampers, 2) oil damper should be introduced to obtain highly damping ratio, 3) BRB has good cost performance about seismic response reduction and can be used to reduce damper costs.