The passing ability of fresh concrete is an important characteristic, which ensures fresh concrete to have enough pumpability and pass through steel bars smoothly. Particle size effect and condensation of aggregate particles due to segregation are generally considered as main blocking causes of fresh concrete at openings. However, the effect of boundary restraint of opening on the flow of fresh concrete is yet unclear. In this paper, to clarify why deformation resistance of fresh concrete increases at openings, the resulted normal stress on shear plane when the shear deformation is restrained in normal direction, was investigated experimentally with a shear box apparatus, in which a stress-controlled method was adopted. And the effects of fluidity, maximum size of coarse aggregate, and loading rate on the normal stress were examined in detail. Based on the experimental results, a normal stress model was proposed to quantify the boundary restraint on the flow of fresh concrete. A method was further proposed to predict the decline of flow ability of fresh concrete at openings. Finally, a prediction example of restrained shear strain was given.

抄録全体を表示

In this study, compressive strength and pore structure of concrete used blast furnace slag fine aggregates that was produced by 3 different steel factories and 1 type natural river sand as compared were examined, and the relationship between compressive strength and porosity was discussed. To concrete used blast furnace slag fine aggregates, compressive strength is lower and porosity is higher than concrete used sand at early ages. At long ages, compressive strength of concrete used blast furnace slag fine aggregates is higher and porosity is lower than concrete used sand when water cement ratio is 55%, but the compressive strength of concrete used blast furnace slag fine aggregates is lower when water cement ratio is below 40%. Young's modulus of concrete using the blast furnace slag fine aggregate is higher than concrete used sand. The relationship between compressive strength and porosity of concrete used blast furnace slag fine aggregates is very consistent with common strength-porosity equation about concrete as well as the concrete used sand.

抄録全体を表示

In this study, a series of experiments on drying shrinkage of porous concrete was carried out to examine the influence of various factors, i.e. void ratio, rock type and size of aggregates, compaction strength level, etc. It was found that the influence of designed void ratio and rock type of the aggregate on the final amount of drying shrinkage of the porous concrete was significant, while the effect of compaction strength level was insignificant. Based on the experimental results, a geometrical model of the porous concrete was proposed to represent the drying shrinkage characteristics. It seems possible to predict the influence of the various factors on the drying shrinkage characteristics by using the proposed model.

抄録全体を表示

The risks of falling at construction sites are primarily caused by a lack of physical stabilities of the workers. In order to ensure their safety and develop better safety guidelines, this study evaluated the various aspects of high-risk activities involved with scaffolding steps by measuring not SD (semantic differential value) but three physical quantities; latitude between minimum and maximum absolute acceleration value, fractal dimension, vacillate value lead from small, wearable and three-dimensional accelerometers.
The findings are as follows:
1) Avoid rushing up and down the stairs.
2) Take an extra precaution right before entering the stairs.
3) Make the height between each step as small as possible.
Furthermore, the evaluation method based on the three physical quantities proposed above seems useful in terms of ensuring safety at construction sites.

抄録全体を表示

Cement concrete material industry, as one of the most resource and energy intensive industries, is facing crucial social demand in the improvement of energy efficiency and reduction of carbon dioxide emission. However, little effort has been made until now to estimate the energy consumption in production processes of ready-mixed concrete plants. (abbr. RMC plants) In this paper, quantification method for electric consumption of RMC plants is proposed using easy-to-use measurement equipment. Electric consumption has been found to depend on the operation time of RMC plants as well as the production amount and concrete types. Energy-saving method without reduction of production amount or replacement of facilities is proposed using the above mentioned time-dependency.

抄録全体を表示

Two kinds of directional retroreflective materials are manufactured, which are designed to show abrupt change in reflectance at the incident angle (Θ) of around 30 degrees. The measured solar reflectances are 17.7 percent for Θ ≥ 40 deg. and 39.0 percent for Θ ≤ 20 deg. for one type; 54.4 percent and 40.8 percent for the other. Building materials having these kinds of incident angle dependences can be used as cool roofs free of side effect; they can be high-reflective exclusively against summer sunlight, and low-reflective against other light sources, such as, winter sunlight, headlights of cars, and street lights.

抄録全体を表示

Steel frames are usually designed with a column overdesign factor (COF) to ensure the preferable failure mode, which is yielding of all beams in flexure prior to the yielding of columns. In the present study, in consideration of the uncertainties of earthquake loads and the strengths of structural members, the failure modes of multistory ductile frame structures are investigated probabilistically. The first-order reliability method (FORM) and the dimension reduction integration (DRI) method with fourth-moment standardization are applied in the investigation. The Ai distribution of load along the height of the frame is taken into account. By comparing the Ai distribution and the triangular distribution results, it is observed that the target COF requirement is affected by the load distribution. To evaluate the target COF requirement that probabilistically avoids undesirable story collapse modes, the system reliability must be considered. In the present paper, the concept of system reliability is introduced in the determination of the target COF. It is observed that the target values of COF considering system reliability are higher than those of the most likely failure mode. This study was conducted for different reliability levels and the corresponding COF values are presented in this paper.

抄録全体を表示

The authors attempt to visually express a lived load of buildings for advance decision making between owners and designers. Therefore, how a visual element perceives this view (area and position of brightness, size, sufficiency level ) was determined using a questionnaire that included the model photograph. Methods have been devised to determine whether the visual perception of a live load is possible, and if so, to what extent the view can be perceived.
The possibility of making an explanatory tool that expresses the best live load for a target was shown by changing the brightness and the size of the furniture according to the type of visual perception the target had. We made a prototype of the explanatory tool for trial purposes.

抄録全体を表示

For mitigating seismic damage of structures during disastrous earthquakes, we have to improve both the procedure for constructing source models for future earthquakes and the method for estimating strong ground motions. The empirical Green's function method (EGFM) is one of the most appropriate methods for estimating strong ground motions near source faults. We constructed the best-fit source models for observed data from the two inland earthquakes, the 2005 West-off Fukuoka earthquake and the 2007 Noto Hanto earthquake using the EGFM. We extended the EGFM to ground motion simulation at soft-layers sites, combining it with the nonlinear analysis in soft soil layers. As a result, the calculated motions on the ground surface underlain by soft layers agree reasonably well with the observed ones. It means that the EGFM is one of the most effective methods for predicting the strong ground motions at both soft-soil sites as well as hard-rock sites.

抄録全体を表示

In this study, we evaluate the influence of fault parameters on the ground motion characteristics and building response characteristics in the near-fault region, in order to develop the seismic design load for the Uemachi fault. We simulate ground motions in near-fault region changing several fault parameters using 3D-FDM. As results, the following conclusions are obtained. 1)Background of fault have little effect to near-fault pulse-like ground motion in the period range T>1.25s. 2)Peak ground velocity is affected by asperity size, rupture velocity, rise time, upper depth of asperity. 3)The pulse period on sedimentary layers depends on that of the bedrock and predominant periods of sedimentary layers. 4)The region where we should consider the influence of pulselike ground motions depends on the ratio of natural periods of buildings and pulse periods of the ground motion.

抄録全体を表示

The authors have proposed the tuned viscous mass damper system based on the fixed points theory, and have proved the validity of the theory and the analysis method through the vibration tests of the small scale test specimen. The testing program revealed that an increase in equivalent inertial mass of viscous mass damper and increase in input resulted in an excessive stresses in the supporting member, damper body and the primary structure connected to the damper. In this paper, authors built the rotation slipping mechanism into the main body of the full-scale tuned viscous mass damper with the spring member of 18,200kN/m and the equivalent inertial mass of 1,350ton, and tested the tuned viscous mass damper with the force restriction mechanism. Analysis parameters of the tuned viscous mass damper with the force restriction mechanism were evaluated accurately and the test results corresponded well with the analytical results. From the analysis results for a 1-story structure, it is shown that this restriction mechanism can effectively reduce the damper maximum force and the maximum response displacement is almost the same as the result obtained by a restriction-free damper.

抄録全体を表示

A model reduction method is proposed for an elastic high-rise building with viscous dampers subjected to earthquake ground motion. A set of story stiffnesses of the reduced model is found under the equivalent conditions that the original model without dampers and its reduced model possess the same fundamental natural frequency and fundamental mode shape. A reduced model of the time-dependent earthquake inertia force is also proposed by requiring the equivalence of displacements at representative floor levels in both models without inertia and damping terms. A set of damping coefficients and a set of relief loads of bilinear-type viscous dampers of the reduce model are found under the equivalent conditions that the original model with dampers and its reduced model possess the same lowest-mode damping ratio and energy dissipation mode shape. Numerical examples are presented to demonstrate the efficiency and accuracy of the proposed method. It is concluded that the proposed method can substantially reduce the number of degrees of freedom in the time history analysis within an acceptable accuracy.

抄録全体を表示

Dynamic centrifuge tests are conducted using soil-pile-structure models in order to investigate the seismic behavior of a building with semi-rigid pile head connections in liquefiable soil. The dynamic test results show that: (1) The semi-rigid pile head connection is effective for reducing the bending moment of a pile in liquefied soil; (2) The natural period of the soil-pile-structure system with semi-rigid pile head connections becomes longer than that of the system with rigid pile head connections during liquefaction; and (3) The hysteresis damping induced by the dynamic interaction between liquefied soil and piles in the system with semi-rigid pile head connections is larger than that in the system with rigid pile head connections.

抄録全体を表示

The aim of this research is to clarify the moment resisiting performance and the feature of traditional joints, and to design according to an arbitrary size. First of all, five kinds of traditional joints were designed, examined, and the moment resisting performance and the feature were clarified. Next, the moment resisting performance of each joint was presumed based on the mechanical model. And the correspondence at the elastic stage with the test result was confirmed.

抄録全体を表示

This paper reports the results of evaluation on seismic performance for wooden houses of Kyoto-Kitayama Type in Miyama based on field survey and static loading test for mock test frames. Major findings from the research are as follows: (1) In the field survey, structural and vibration characteristics are clarified. (2) In the experiment, it is find out that structural factors founded on the specification of Miyama have different strength from the past restoring models: such as wooden wall, Sashigamoi and so on. (3) Applying the restoring model conducted the experiment results, the maximum change of yield base shear coefficient is 40%.

抄録全体を表示

Generally in Japanese style rooms, sheathed walls with uncovered post have widely been used instead of mud walls. The sheathing material is nailed and inserted in the frame with noggins. The formula to calculate the elastic strength, yield point, ultimate strength and the ductility factor has been derived for the sheathed wall, considering the elements of the shear resistance of the nail strucked in the noggins and frame, and the diagonal compression resistance of the sheathing material as truss action. In order to verify the formula, the shear racking tests of sheathed walls have been carried out where plywood and plasterboard have been used as sheathing materials. It is clear that the formula is sufficiently accurate to predict the elastic and plastic behavior of sheathed walls with uncovered post for structural calculation.

抄録全体を表示

Being insufficient seismic capacities of the existing buildings not designed in accordance with the current code, it is politically encouraged to improve their structural properties specified stiffness, strength and ductility. Conventionally, bare frames of the buildings are strengthened using of steel braces with a peripheral steel frame and many anchor bolts and grouting mortar are placed in their connections to transfer design loads. To develop new strengthening methods without the anchor bolts, a cyclic loading test of a one bay-two stories R/C frame strengthened with steel braces was conducted. The frame exhibited ductile response after constraining the beam elongation on the second floor.
By taking the constraint effect of adjoining slabs into account, it was showed that the response of the frame was improved and the shear capacity of each story can be evaluated by the proposed equations.

抄録全体を表示

A moment frame with bracing elements is one of efficient seismic-resistant structural system in elastic design, however, when the seismic input is larger than the buckling strength of braces, these undergo local buckling subsequent to overall buckling, and the concentration of plastic strain at local buckling area easily leads to brace fracture. The authors have previously proposed a brace fracture prediction method. In this paper, time-history response analyses for braced frames are carried out focusing on the brace fracture using the proposed method. A discussion follows fatigue distribution in the frame types, including the effect of the brace fracture itself.

抄録全体を表示

Cyclic loading tests of column bases in steel braced frames were conducted. Based on the test results, shear resistances governed by concrete edge failure of column base with various anchor spacings and reinforcement patterns were evaluated. Post-concrete edge failure behavior were also discussed to evaluate ultimate shear resistant mechanism considering the contribution of reinforcements around anchor bolts. In addition, shear resistance determined by steel yielding of anchor bolts was discussed taking bearing resistance of anchor bolt into account.

抄録全体を表示

In our previous papers, the new column support system is suggested, and it is shown that the columns base for the steel moment resisting frames never yield during large earthquake by the dynamic analyses. In this paper, the cyclic loading tests are performed for the partial steel frames with the embedded column base or our proposal new column support system. The columns for the proposal support system are shown to keep elastic by the large plastic range of the frames such as the angle of 0.05, even though the columns for the embedded column base become as much plastic as the beams.

抄録全体を表示