The effective use of fly ash has been actively studied in various fields, and it became clear that making concrete aggregates with fly ash should be one of the most effective way. We have developed "High Strength Artificial Aggregate" (hereinafter called FA aggregate) made of fly ash which has a dense structure and low water absorption. In this report, we studied on fireproofing performance of concrete using FA aggregate in comparison with those of concrete using natural aggregate (hereinafter called NA aggregate) and artificial lightweight aggregate in the market (hereinafter LA aggregate). To evaluate the fire resistance of concrete using FA aggregate, we conducted the fire test with specimen and fire test with RC concrete beam. Following test results are obtained. (1) In decreasing rates of compressive strength and elastic modulus of the small specimens after heating, there's little difference due to the type of aggregates. (2) The temperature of the central part in the RC concrete beam with FA aggregate is slightly higher than that of NA aggregate. (3) The deformation of the RC concrete beam with FA aggregate is somewhat larger than that with NA aggregate, but it does not exceed the limit. (4) It is confirmed that the concrete using FA aggregate has sufficient fire resistance compared with the concrete using NA aggregate.

View full abstract

The durability of concrete is greatly influenced by the physical properties of the hardened cement paste. The physical properties of hardened cement paste are dependent on the degree of hydration and porosity of hardened cement paste. Therefore, it is important to measure the degree of hydration and porosity of hardened cement paste correctly. Measuring them, some methods are proposed, XRD, point counting or TG/DTA as example. Then, in this research, with Backscatter electron image (BEI) and Energy dispersive X-ray analysis (EDX), the degree of hydration and porosity of hardened cement paste are measured, and clarifying the distribution of the composition. By using BEI and EDX together, as a result of applying the method, the degree of hydration and porosity of hardened cement paste were clarified and the distribution of a compound was clarified further.

View full abstract

In order to evaluate influences of rain on carbonation process of concrete structure, an analytical model was proposed for predicting carbonation process coupled with heat and moisture transfer, particularly liquid movement. The accelerated carbonation experiment under the isothermal condition in a literature was simulated by using the proposed model, in which the coefficients of moisture transfer and CO_2 diffusion were estimated by comparing the simulation results with the experimental results. By using the coefficients corresponding to the water cement ratio and the curing condition, this model can predict carbonation progress well. The simulation results also showed that the liquid transfer significantly influenced the carbonation process even under the rainless condition such as evaporating process after placing.

View full abstract

In pressure equalizing wall design, it is important to know the degree of pressure drop due to pressure change lag inside the wall cavity against fluctuating wind pressure, especially with cavities having small vent area / cavity volume ratios. In this paper, a method for estimating internal pressure change with time was proposed, in which fluctuating external pressure is replaced by a series of short time stepwise pressure changes, and internal pressure is given by accumulating calculated results for each step for which equations expressing pressure change inside a single vent cavity based on Boyles law are applied. Measured and estimated internal pressure responses obtained for wall cavity models were in good agreement, both under cyclic and random fluctuation of external pressure.

View full abstract

It is a subject important for global environment preservation to recycle materials from demolished buildings. However, contrast with the amount of reduction of an environmental impact and the change of expense is important. These both are grasped and environmental accounting is in the technique of making an action judgment. Here, it focus on recycling of construction generating wood, various kinds of evaluation techniques were compared and environmental performance has been grasped quantitatively. And the optimal processing system was considered.

View full abstract

This study aims at configuring the input wave, as a substance, so as to evaluate the seismic resistance of free-access floors. Approach used in this study is described in procedural manner as follows; At first, the behavior of specimen is observed, imputing real seismic waves, which is picked up on behalf of free-access floors. Next, as abstracted parts impacting the behavior of specimen by real seismic waves, input waves are obtained. And then, simple vibration table is made to reproduce input waves. Finally, it is configured that an input wave for evaluating the seismic resistance of free-access floors, substituted for real seismic waves.

View full abstract

This paper discusses simplified theories on seismic peak response evaluation and preliminary design of elasto-plastically damped building. The theories are based on the single-degree-of-freedom (SDOF) idealization of multistory building structure, and produce the so-called "control performance curve" expressing the seismic performance as a function of stiffness parameter, ductility demands, and response spectrum. The curve is used to find desirable stiffness balance between damper and other elements of the SDOF model. A rule to convert the SDOF design to multistory design, with a consideration to distribute damper stiffness over the building height, is also presented. Accuracy of proposed design approach is demonstrated via numerous time history simulations of a wide range of multiple-degrees-of-freedom (MDOF) models.

View full abstract

The interaction of building and foundation is important when considering dynamic behavior of the building structure during an earthquake. Many buildings were collapsed by destruction of columns in compression or foundation failure in compression also. There is almost no building that was collapsed by tension failure of columns or uplift of the basement from foundation. We will discuss about shaking tables tests and numerical analysis for two-story model and four-story model on elastic spring foundations, with considering uplift motion.

View full abstract

We propose a method for estimating the minimum weight of a 3D steel frame from a set of optimal solutions of 2D frames. The characteristics of the optimal solutions of 2D frames are studied by changing the number of spans, the span lengths, and the level of external loadings. Based on the results of this study, we propose a parametric model to estimate the optimal solutions of a variety of 2D frames. Combination of these parametric models enables us to estimate the optimal solution of a 3D frame. We demonstrate the validity of the proposed method through a numerical example of a 5 story building.

View full abstract

When slender steel piles beneath buildings experience high axial compression forces as a result of vertical loads increased by P-Δ effects with inertia forces acting on the buildings and then the soil liquefies, buckling of the piles may occur even thought they are restrained laterally by the liquefied soil. This paper describes the evaluation of the buckling length of slender piles in liquefied soil with the unified and triangular distributions of the coefficient of the subgrade reaction. The relationship between the buckling length of the slender piles and the soil-pile interaction is presented.

View full abstract

The report describes about analyzing the scope of rigid floor assumption of wooden structure. The full scale single-story buildings were flat size of 4P-wide by 4P-wide by one-floor (3,640mm-long by 3,640mm-long by 2,578mm-height) and were different in eccentricity ratio. We grasped twist behavior by the static-loading test being carried out on these buildings. We studied the scope of rigid floor assumption by comparing analyisis values from matrix varied floor stiffness and shapes with calculated values by correction coefficient calculated with rigid assumpion.

View full abstract

This paper studies a breaking point of linear distribution of strains over the depth of high strength R/C column section under high axial compression and lateral loading reversals. Based on 34 test data, it was confirmed that the breaking point of the linearity corresponded to 0.85 maximum strength point of the load-displacement curve and the tangent stiffness of the breaking point was approximately equal to 1/3 of the initial stiffness. Use of the breaking point for 4point-4 line (quadri-linear) model of the restoring force characteristics can construct more accurate model than traditional tri-linear model.

View full abstract

The aim of this paper is to propose an estimation method for long-term defection of reinforced concrete slabs, due to rigidity decrease caused by cracking, creep, shrinkage of concrete and slippage of tensile re-bar at fixed edges. Compared to previous methods, a new method of creep estimation influenced by shrinkage progress is introduced and estimation of creep and concrete stress is processed with numerical step by step method. Compared to those experimented in Japan, the calculated mid-long term deflections based on the calculated aging strain supposing shrinkage as triangular distribution are proved to be good upper limits to actual deflections of experimented fixed-end slabs.

View full abstract

The bond splitting strength of beams with recycled aggregate concrete was investigated. Since the rate of water absorption of recycled aggregate in recycled aggregate concrete is large, drying shrinkage cracks tend to occur. These drying shrinkage cracks are closely related to drying shrinkage percentage. So in this research, recycled aggregate concrete to which a shrinkage reducing agent was added to control the drying shrinkage percentage was used. As a result, the drying shrinkage percentage of recycled aggregate concrete containing the shrinkage reducing agent was smaller than that without the agent, confirming the effect of the agent. In beams made with recycled coarse aggregate containing the agent, few drying shrinkage cracks occurred. The bond splitting strength of lap splices was examined. The bond splitting strength with recycled coarse aggregate increased when the shrinkage reducing agent was added because concrete strength increased.

View full abstract

This paper presents the results of an experimental verification on a full-scale three story 'weld-free' structure, which is proposed as an innovative steel frame adopting mechanical joints equipped with buckling-restrained type knee brace dampers for wide-flange moment frames. Major findings are as follows: (1) The weld-free structure exhibits stable hysteresis behavior under 0.04 radian drift angle in-plane, (2) The yield mechanism by plastification of dampers and column bases meet the target mechanism, (3) The structure collapses by overall buckling of dampers and lateral-torsional buckling of beams but the maximum drift angle attained 0.10 radian preserving sufficient lateral resistance.

View full abstract

The super high strength bolt which has about 1400N/mm^2 tensile strengthof is developed. In this super high strength bolt, the shape of the bolt thread bottom and the shape of imperfect tfread are improved so that this super-high strength bolt may improve the performance to delayed fracture. Though the cause of the delayed fracture and the fatigue fracture is different, the parts improved to the delayed fracture is expected to bring good results for fatigue strength. In this paper, the fatigue strength of super high strength bolts is described. The shape of bolt thread bottom, the bolt strength, and the kind of the bolt material are taken as test parameters. And from the test results, the results of considering the influence that these test parameters give to fatigue strength are described.

View full abstract

This paper presents an experimental study on new moment frame connections designed to restrict damage to specific connection elements placed at the bottom flange of the beam. Composite effects and damage to the concrete slab were addressed in these tests. Composite action led to a roughly 98% increase in initial elastic stiffness and 20% increase in yield strength. Meanwhile, the plastic strain at the specific connection elements was increased by only 20%, indicating that the plastic rotation capacity of the connections was hardly affected by the presence of the concrete slab. And the feature of the design forcing the connection to rotate about the top flange was beneficial in reducing damage to the concrete slab.

View full abstract

Authors had proposed the brace that strength, remained plastic deformation capacity and energy absorption capacity can be easily evaluated under seismic loading. Proposed brace consists of slender rod and tensile connected end with beveled washer and wedge. There is no buckling in the brace. The wedge slides between washer and stand so as to prevent the looseness of brace due to axial plastic deformation under repeated lateral loading. To improve the plastic deformation capacity of the brace, new tensile connected end with beveled washer and wedge are proposed. To show the mechanism and performance of the brace, the repeated lateral loading tests are performed on one story one bay frame with tensile connected brace with wedge device. Results and conclusion obtained from loading tests are summarized as follows. 1) The perfectly elasto-plastic hysteresis are observed until slide displacement of wedge reaches its maximum value. 2) Story shear, strength and energy absorption capacity are easily evaluated. 3) The remained plastic deformation capacity after earthquake can be evaluated by means of checking total slide displacement of the wedge. 4) Using new tensile connected end with beveled washer and wedge, it is possible to enhance the plastic deformation capacity.

View full abstract

As well known, concrete-filled tubular (CFT) columns have excellent capacities for the plastic deformation and energy absorption even under high compression. In order to use the capacities of CFT columns in moment-resistant frames, a new yield mechanism is proposed where some columns are permitted to yield. In that case, the attention should be paid for the frame instability such as story pancake crush. A column-to-beam strength ratio defined at a floor level will be one of effective parameters to control the frame stability. From this point of view, the minimum requirement of the ratio is investigated by time-history dynamic responses of the maximum deformation and the damage in CFT columns of frame models with various number of stories or bays, and arrangement of columns to permitted to yield.

View full abstract

This study is an experimental confirmation of torsional behavior of alminium alloy sandwich panels. Five series of panels were tested. And these are grouped into three classes such as adhesive brazed and urethane panels. Adhesive panels consists of two series with different sizes of honeycomb core. Brazed panel consists of two series with different types of cores such as honeycomb and round core. Explanations of initial stiffness, ultimate strength and inelastic behavior are tried by the method of simple multi-cell substitution.

View full abstract

It is natural to treat a building structure as a three-dimensional body when considering its behaviour in a fire, because fire is a phenomenon involving three-dimensional thermal expansion. This study takes further our proposal of an analytical method involving the unitary division of structure as an approach to the problem of the increase in the number of nodes which occurs in the three-dimensional analysis of a building frame. The study presents a three-dimensional thermal stress analytical method which takes account of the thermal expansion of a floor slab exposed to fire by conceiving the floor slab as a grid of intersecting beams. The theoretical results agree well with those recorded in experiments in which a full scale frame was exposed to vehicle fire.

View full abstract