This paper describes characteristics of air pressure variation field on the surface of the 3-dimentional square prism under aerodynamic vibration. The analysis is conducted by means of Complex Proper Orthogonal Decomposition, which is referred as CPOD. The improved hybrid aerodynamic vibration technique is applied to measure the air pressure. As a result, two typical modes, which are symmetrical mode and inversely symmetrical mode, are included in the CPOD mode. It is found out that the inversely symmetrical mode is a governing mode to generate the aerodynamic vibration, and in the case of generating Vortex Induced Vibration or Galloping Vibration, we can distinguish these phenomena from the information of phase angle distribution of inversely symmetrical mode.

View full abstract

This paper discusses on designing of vibration control system using evolutionary algorithms based on Particle Swarm Optimization (PSO). First, a new modified PSO strategy by adding a mutation rule (MPSO) is shown. Search efficiencies with Genetic Algorithms, original PSO and proposed MPSO are compared by solving standard benchmark functions. MPSO shows the excellent performance to optimize parameter of these functions, even it has multi-modal or parameters with epistasis. Second, structural system identification problems using MPSO are discussed. Structural system represented with product of biquad transfer functions can be identified by MPSO strategy. Finally, MPSO is applied to design MDOF vibration controller. The control performance by MPSO controller is described in both simulation and experiment to reduce floor vibration using an active mass damper.

View full abstract

Simplified theories are proposed for seismic response evaluation and preliminary design of RC building structures added with visco-elastic dampers. They are based on the single-degree-of-freedom (SDOF) idealization of multistory building, and produce the control performance curve expressing the peak responses as a function of stiffness of all components, based on spectral characteristics of the earthquake. Against the target peak response, a rule to convert the SDOF design to multistory design, with consideration to distribute damper stiffness over the building height, is also presented. Accuracy of the approach is demonstrated by passive control design and time history simulations on a 7-story RC building.

View full abstract

The main problem addressed in this paper is to evaluate robustness of a linear elastic structure with an uncertain static external load. We consider the compliance constraint as a performance requirement and use the robustness function as a qualitative measure of robustness. The robustness function is defined as the largest level of uncertainty in the external load, up to which the compliance constraint is satisfied. We show that the robustness function can be computed by solving a semidefinite programming problem. Numerical examples illustrate that robust preference between two given structural designs depends on the critical performance.

View full abstract

This paper investigates the behavior of the second mode resonance in the liquid storage tanks with the single-deck type floating roof. In the Tokachi-Oki Earthquake in 2003, the floating roof of the large-sized oil tanks received damage by sloshing. One of the reasons is considered to be elliptical deformation of the pontoon by the second mode resonance in the past report. In this paper, the behavior of the floating roof is simulated by the numerical analysis method which we propose, and the deformation and stress in the pontoon are investigated in detail. The stress of the pontoon calculated by the design method notified by the Fire Defense Agency is compared with the numerical results. By these results, the validity and the applicability of the design method are discussed.

View full abstract

In this paper, moment resisting behavior of mortise-tenon joint with dowel is examined. At first, bending tests for mortise-tenon joint are conducted. A hundred and eight specimens are tested, and their parameters are dimension of tenon, post, beam and dowel and tree species of members. In addition, evaluation rule for moment resisting performance of mortise-tenon joint is proposed. It is based on the result of local compression test of wooden materials. Moment - rotation relationship of connection can be calculated by solving simplified equation of equilibrium.

View full abstract

We have developed a new seismic reinforcing method that combines aramid fiber sheets and steel plates for existing RC columns. In order to investigate structure characteristic of RC columns retrofitted with this technique, cyclic lateral loading test was carried out. As a test results, the tendency of hysteretic loops were generally similar for all specimens;longitudinal bar was yielding at drift angle of 1/100rad, the strength started to decrease when the maximum strength was achieved at drift angle of about 1/50rad. Flexural cracks after the test were observed at the top and bottom of column. However, the strength decrease was very small and cracks was few. Furthermore, it was found that this method can be used for enhancing the flexural strength compared with RC columns retrofitted only by aramid fiber sheets. Therefore, the calculated values by current ultimate flexural capacity formula were underestimate test results.
This paper was discussed about the flexural strength and the ductile behavior obtained form the skeleton curve, which was converted into the elastic-plastic restoring force characteristics based on principle of the ultimate energy equilibrium. In conclusion, the experimental evaluation methods of seismic performance for columns retrofitted with this technique was estimated considering the increasing effect of flexural strength and equivalent viscous damping factor.

View full abstract

The first objective of this paper is to clarify the analytical accuracies and the points of the existing three formulas which estimate the maximum strength of isolated framed shear walls. The second is to reconstruct the authors' elasto-plastic analytical model considering the clarified points at issue. In the reconstructed elasto-plastic analytical model, the elasto-plastic properties of the surrounding frame are considered. And the inclination angle of diagonal line of the surrounding frame is adopted as the inclination angle of compressive struts. Furthermore, the effective compressive strength of the struts: 0.63σ_B is introduced. The analysis by the three existing formulas and the reconstructed elasto-plastic analytical model were executed for sixty seven specimens subjected to shear loading. They failed in shear failure mode or flexural-shear failure mode. Analytical accuracies of the three existing formulas are unsatisfactory. On the other hand, the analytical accuracy of the reconstructed elasto-plastic analytical model is satisfactory. In case of the reconstructed elasto-plastic analytical model, the analytical accuracy is described by the ratios of the observed maximum strength to the calculated maximum strength as follows: The mean is 1.193, the standard deviation is 0.128, and the coefficient of variance is 0.107. These values show that this model is effective to estimate the maximum strength of the isolated framed shear walls.

View full abstract

A four-story prestressed concrete building is tested by using the E-Defense shake-table facility. The test building with a rectangular plan utilizes the moment frame system in the longitudinal direction and the multi-story wall frame system in the transverse direction. For a series of tests, the intensity of input ground motions is gradually increased. Finally, the moment frame system sustains the maximum story drifts more than 0.05 rad exhibiting a partial mechanism, while the multi-story wall frame system remains the story drifts less than 0.02 rad.

View full abstract

The performance of high-rise steel moment frame buildings constructed in the 1970's is examined by using the E-Defense shake-table facility. Typical design and detailing in the 1970's are incorporated in a four-story, steel moment frame specimen. The specimen is subjected to a series of response deformations representing a high-rise building. Long-period ground motions impose a substantial number of inelastic deformations, which eventually cause fracture in the beam-to-column connections.

View full abstract

Passive-control is used for most major Japanese high-rise buildings after the 1995 Kobe earthquake. Nevertheless, the majority of these studies have tested isolated dampers or simple subassemblies which neglect the influence of the framing components and the damper connections on the system performance. In order to evaluate the elasto-plastic behavior of beam-column subassemblies with wall-type damper connections, hybrid-control experiments are carried out. Connections of wall-type damper lead to 17 to 33 % increase of the initial elastic stiffness to beam-column subassemblies. Plastic rotations of framing components are observed only in beam-end parts without damper connections. Based on the test results, numerical model of beam-column subassemblies with walltype dampers is established to evaluate the concentration of plastic deformation.

View full abstract

A series of tests, which reproduced brittle fracture starting from the region around the terminations of CJP (complete joint penetration) groove welded joints, was conducted. The joint models under study were portion of welded beam flange-to-through diaphragm joints in beam-to-column connections. Various artificial defects were installed in the welded joints prior to testing. This paper describes the effects of plastic constraint on brittle fracture from the welded joints with the defects at the ends of CJP groove welds. A toughness scaling model, which considers the effects of plastic constraint, was used for evaluating the occurrence of brittle fracture and was found to predict well the test results, compared with a conventional prediction method using fracture toughness J_c.

View full abstract

Wall-type precast reinforced concrete (WPC) residential buildings were widely constructed in Japan since the middle of the 1960s. A large number of these types of buildings still exit, and maintain high structural quality; however, their residential units are rather small and are extremely standardized, which do not suit modern living use. In order to create new openings in existing WPC walls to widen possibilities for plan changes during renovations, the authors conducted experiments of half-scale WPC shear walls with new openings and reinforcement. In addition, inelastic static pushover analysis models were created, that can reasonably simulate the shear wall behavior. In this paper, the analytical models are developed for full-scale, standard WPC residential buildings to evaluate the collapse mechanism and ultimate lateral strength. Through the static pushover analyses, the ultimate seismic strength (base-shear) coefficient is determined to be approximately 0.6 and rocking of the shear walls accompanied with failure of the connecting reinforcement at the first floor is the primary mechanism. Furthermore, in some analysis models with new openings in the shear walls, the influence on the ultimate lateral strength and failure mechanism is limited.

View full abstract

In this study, experimental investigations were conducted regarding flexural strengthening of reinforced concrete (RC) beams using high-toughness polymer cement mortar (HTPCM) and continuous fiber reinforcements. Our results showed that using the HTPCM as section recovering and thickening materials is effective in improving flexural strengthening effect of continuous fiber sheets/plates and rods on RC beams, because diagonal tensile cracking in tension-side covering concrete and bond-splitting failure of thickened part are prevented by the HTPCM. Furthermore, it was also shown that the flexural strengthening effect does not remarkably decline by upward execution, if plastering thickness of HTPCM of one time is adjusted to 6 mm or less.

View full abstract

Experimental and analytical achievements on the fracture-governed deformation capacity of steel beam welded to box-column in the above paper are discussed about the following items: 1) The mode of fracture should be clarified to be ductile or fatigue cracking. 2) The proposed rule for crack propagation seems improper, because it does not match with the experimental data. 3) The statement that the equivalent plastic strain is related to the ultimate cumulative ductility irrespective of NSS and NSW seems ambiguous, because the data does not demonstrate it.

View full abstract

The authors thank Prof. Hitoshi Kuwamura for his discussion, and the answers are as follows;
(1) The mode of fracture is clarified to be ductile cracking.
(2) The proposed crack propagation approximately matches with the experimental data at the ultimate state.
(3) The equivalent plastic strain does not strictly related to the ultimate cumulative ductility, but the value seems to be related to the difference of test results between NSS and NSW.

View full abstract