A New low-carbon concrete binder consisting of recycled cementitious powder produced from fresh ready-mixed concrete waste is focused. Dehydrated sludge powder (DPS) is utilized as supplemental cementitious material in combination with Portland cement. This study introduces quality controlling scheme by adopting apparent specific surface area in DPS, which clearly indicates quality of DSP in terms of such as strength contribution after hardened. Experimental findings to reveal article size distribution, remaining unhydrated cement amount, and corresponding compressive strength development demonstrated that apparent specific surface area clearly illustrates quality of DSP with solid physical background.
Since the Great East Japan Earthquake in 2011, the emission rate of fly ash (FA) has increased. Because FA can be used in numerous applications, such as a concrete ingredient, this study concerns the possibility of expanding the use of FA in concrete structures. The effects of the binder type, carbonation, and presence of external water on the rebar corrosion was investigated. Experimental results indicated that the use of FA had a small effect on rebar corrosion. Moreover, rebar corrosion rapidly progressed in the presence of both carbonation and external water; thus, it can be suppressed by excluding either one.
Slump, an index that indicates the consistency of fresh concrete before it sets, is one of the most important quality measurement criteria. Fundamental technology that contributes to stabilized concrete manufacturing to instantly predict the slump of mixed concrete with high accuracy using Artificial Intelligence (AI) has developed. In this experiment, the method using deep learning and image recognition techniques of AI could to predict the slump from an image of concrete mixing in a mixer, with an extremely high accuracy rate of over 99% within a measured value ± 2.5 cm.
This study optimized the binder composition for making 300N/mm2 ultra-high-strength concrete. The use of silica fume with a replacement ratio of 24%, which contained 50% coarse silica flour, attained both high compressive strength and high fluidity. The newly developed chemical admixture showed excellent dispersibility down to 10% water-to-binder ratio, which improved concrete workability, mitigated the delayed setting times, and resulted in 30% less shrinkage and 7% strength gain. For the design strength of 300N/mm2, satisfactory strength and workability can be reached with the specific aggregates and curing scheme reported in our previous study.
This study conducted practical development of 300N/mm2 precast concrete. As a result, the followings were found to be important, lengthen mixing time for fluidity and strength development, sufficiently deforming of the specimen using vibrator, deforming by pressurizing and depressurizing with squeeze-type pump before casting the member, and protecting form direct steam in AC-curing tank. In addition, strength development can be evaluated by effective-age of over 20°C, and the curing patterns that can achieve compressive strength of 300N/mm2 and small shrinkage is to shorten the 90°C steam-curing time and apply 180°C AC-curing over 4 hours or 150°C AC-curing over 12 hours.
A new type admixture was developed for a non drying-shrinkage type concrete. The properties of hardened concrete using this admixture and expansive additive were studied by laboratory test and mock-up test. Drying-shrinkage of the non drying-shrinkage type concrete using this admixture was more than 40% less than ordinary concrete. Properties of this hardened concrete, such as compressive strength were determined by this experimental tests. Effect of restraining cracks by using this admixture and expansive additive was verified by test on drying shrinkage cracking of restrained concrete, and mock-up wall test with opening. Furthermore, this concrete was applied to five buildings.
Among the researches on the workability of high fluidity concrete and the quality evaluation of the resulting structure, the full-scale mock experiment of columns and walls of RC structure was carried out and reported in this paper as the Part 2. Also the characteristics of the high fluidity concrete were compared with those of the concrete using general slump control and with those of compaction-free concrete through literature survey. As a result, it was quantitatively clarified that the characteristics of the high fluidity concrete can be positioned between those of the general concrete with slump control and the compaction-free concrete.
Basic physical properties and weatherability were evaluated in order to evaluate the practicality of the fluororesin powder coating. As a result, the basic physical properties of various powder coatings were almost the same as those of solvent-based fluororesin coatings (PVDF). As a result of the accelerated weather resistance test and outdoor exposure test in Okinawa, a difference in weatherability was observed depending on the type of powder coating, and a fluororesin powder coating with the same performance as PVDF was confirmed. One of the causes of deterioration of the powder coating was presumed to be photocatalytic reaction.
The method for construction management for construction woks of polyurethane waterproofing membrane being improved in repair work site was described in this research. The effectiveness of the method was confirmed by being applied to subsequent repair works. To check the quality of repair work of polyurethane waterproofing membrane, thickness of membrane was verified. The aging condition was also inspected for ensuring aged membrane.
A case study was conducted on the planning for early age curing in cold weather concreting. The temperature and the period of the early age curing corresponding to the mix proportion of concrete were examined for the various places in Hokkaido. As a result, it is desirable the planned temperature during early age be lower than 15C. In colder areas of Hokkaido, it can’t be constructed without continuous heating curing. In warmer areas of Hokkaido, continuous heating curing may not be necessary if the early age curing is conducted.
The purpose of study was to clarify the quality of plywood for concrete formwork with reuse of forms and the finish of concrete surface using reused plywood. In this study, an experiment on influence of reuse (up to 4 times) of plywood for conventional formwork at building construction site was carried out. Regarding the influence of reuse on the quality of plywood, bending strength, bending Young’s modulus, and surface roughness were investigated. In addition, the influence of reused plywood on gloss, color unevenness, and water absorption of the concrete surface was investigated. Moreover, in order to confirm the influence of reuse of plywood at construction site, the results of this experiment at building construction site were compared with the results of laboratory experiment conducted so far.
In this report, we conducted a questionnaire for pumping constructors to clarify the actual condition of work with placing booms. As a result, although JIS A 8612 limits the accessories that can be connected to placing booms tip depending on the shape of placing booms tip, it was suggested that the actual work depends on the construction conditions and the quality of pumped concrete than the shape of placing booms tip. In addition, equipment that exceeds JIS A 8612 limits has be often connected, which was particularly noticeable for concrete pump with long placing booms.
In this study, focusing on the quality control and the inspection for 3D printing used in construction, the extrudability and the buildability of cementitious printing materials were investigated. In particular, the unique test methods to evaluate these two qualities were invented and tested out, and the extrusion test and the lamination test by a real 3D printer were also performed concurrently. As the result, it turned out that the extrudability and the buildability of 3D printing materials can be generally evaluated by the test methods invented by authors.
In this study, a verification experiment was carried out on a survey method in which an infrared thermograph was installed in a drone that has already been widely used for surveying the exterior wall, and the accuracy of the exterior wall diagnosis and the examination procedure were examined. As a result, it was clarified the points to be noted for the external wall survey by the Infrared thermograph mounted on the drone, and the need to improve the Infrared thermograph mounted on the drone.
The aim of this study is to investigate the behaviors of corrosion-induced concrete spalling/falling from fair-faced RC walls and to propose risk assessment methodology for them based on visual inspection. Accelerated corrosion tests show that detectable concrete spalling/falling occurs when cover depth is under 30mm and that rapid increase of concrete spalling/falling follows increase of surface cracking. We propose a framework of criteria for detecting the symptom of the rapid increase, where deterioration degree of inspected walls is divided into 3 stages based on crack index Ic . The criteria for Ic is determined by average cover depth of the walls.
Dynamic loads by various equipment running on actual building floors are causes of flaws of floor surface. In this research, influence of types of floor covering sheets and adhesive and water content in concrete slab on floor durability against the dynamic loads was examined experimentally. As a result, although there is a limited range, combinations of the floor covering sheets and the adhesive and the water content in concrete slab to prevent the flaw were organized according to each characteristic of the dynamic loads by running casters, dragging of caster locked and twist involved with turn of caster.
Foamed plastic insulations installed into buildings are now expected to be long-lasting materials. However, in recent years, it has been reported that the foamed plastic insulation installed in the high-humid environment, such as under waterproof sheets on a rooftop, absorbs moisture and subsequently increases the thermal conductivity. The mechanism of moisture absorption is not sufficiently clear, and the test method for thermal conductivity of building insulating materials does not consider the influence of humidity. This study observed both moisture absorption and changes of physical properties of foamed plastic insulations after exposed at high humidity and discussed the moisture-induced deterioration.
3D data on unfilled portion in 2 organic adhesive post-installed anchor specimens with intentional unfilled portion is obtained from neutron imaging technology. Image analysis is implemented using above 3D data and length of unfilled portion along re-bar is evaluated quantitatively. After that investigation, length of unfilled portion in some heated adhesive post-installed anchor specimens is predicted using above evaluation method. Finally, those specimens are cut to check the unfilled portion.
This paper reports on the influence of environmental temperature on pull-out properties of post-installed mechanical anchor. And the follow conclusions were found. As the environmental temperature rises, maximum load tends to decrease, and the drop of the load becomes approximately linear. There is relationship between the maximum load and the compressive strength under the heated condition less than 100°C.
In this study, we proposed a method to determine the frictional resistance by pushing the CFRTP socket at a temperature above Tg and changing its shape without heating it to the melting temperature. Since the surface of the strand and socket were heated to a temperature above Tg, it was confirmed that they were bonded, and the initial behavior was adhesive resistance. However, pull-out tests and observations using CT and digital microscope have confirmed that the frictional resistance after yielding does not cause brittle fracture.
Evaluating roof snow load is an important problem for building design in snowy regions. A semi-full-scale building model was developed to obtain validation data for the model for evaluating roof snow load. The building model was placed in an observational field in Nagaoka City, where extensive weather conditions were measured. The seasonal change in the roof snow load was directly measured by a load cell installed between the pillars and beams. The water runoff from the roof was recorded at the drainpipe. The effectiveness of the measurement system was demonstrated with observation data from the winter of 2018–2019.
This paper reports the results of field investigation with wooden residential houses in Mashiki Town that were damaged in the 2016 Kumamoto Earthquake. Interviews of earthquake victims were conducted to investigate the house plans of seven damaged houses. Based on these plans, earthquake response analysis was conducted to simulate the direction of damage of the seven damaged houses. It was found that the load-bearing walls in the longitudinal direction of some damaged houses were inadequate to withstand the strong motion during the 2016 Kumamoto Earthquake between east, northeast and west, southwest, which was responsible for the damage of many house.
A series of tests for an unit-type curtain wall system were conducted in order to develop (a) a seismic monitoring technology installed in curtain wall systems and (b) a numerical model representing the seismic behaviors of curtain wall systems. A gyro sensor was adopted to assess the rotation distributions of the mullion. This instrumentation demonstrated the bending deformation distributions of the mullion. A numerical model focusing on the in-plane direction was developed by beam and 1-D spring elements. Regarding the mullion deformations, the numerical analysis of the proposed model evaluated the test results within an error of about 10%.
We measured human-induced walking vibrations in an over-road hospital connecting-bridge. When walked upon at a fixed frequency by 4 people, the passage had a livability equivalent to the performance required of a typical residential building. Even when walked upon with 12 people, the performance was such that the impact on the habitability of patient room is small. In addition, the dominant frequency and damping constants were extracted from the Fourier spectrum of recorded vibrations. In the vertical direction, the natural frequency and the damping constant were estimated to be 9 Hz and 3.26% respectively.
The seismic isolation structure has a habitability problem that it tends to be vibrated when it is always used. Therefore, we have newly developed a seismic isolation device that controls vibration in the infinitesimal range. The seismic isolation device is an elastic slide bearing and an oil damper integrated, and the performance of the damper in the infinitesimal vibration range was confirmed by vibration tests. We confirmed the effect of adopting it in a building by analysis. We also conducted dynamic tests to verify the performance of the seismic isolation device and put it into practical use.
The indoor damages and shaking of high-rise residential buildings to pulse-type ground motions are investigated using questionnaire survey to residents after the 2018 Hualien, Taiwan, earthquake. Answers are compiled by three levels of stories in each building. Intensity of floor shaking and action difficulty in the northeast area are the strongest among three areas. Indoor damages including height-wise distribution of wall paper cracks were similar to those of the 2016 Kumamoto where pulse-like ground motions hit to high-rise buildings, rather than those in the Kanto area during the 2011 Tohoku earthquake.
This report describes the influence of the seismic source location of interplate earthquake on the evaluation of long-period ground motion in the Tokyo metropolitan area. Source points are arranged at every 10 km in the seismic fault plane on the plate boundary off Ibaraki and Chiba prefecture, along the Sagami and the Suruga Troughs. Reciprocal theorem is applied for the 3-D finite difference method to evaluate ground motions at target sites from many source points. We also examine influence of low-velocity sediments in the Philippine Sea Plate region on long-period ground motions in the Tokyo metropolitan area.
Recent studies predict that Nankai-Trough earthquake to be a huge one. As a mitigating measure, passive dampers are widely adopted to control structural vibrations of buildings. These devices work effectively against the inter-story shear deformation of the building frame. In contract, they are less effective when building deformation is mainly characterized as flexural or bending deformation. It is, therefore, important to study the effective damper deformation in order to evaluate vibration control performance. This paper aims to clarify the relationship between the effective damper deformation and damper ductility demand when the damper works effectively.
In recent years, there has been an increase in the application of the jet grouting method under existing buildings. In order to reduce the environmental load and rationalize construction, the authors have developed a technology to reduce the amount of sludge discharge by reducing the amount of cement milk injected into the ground. As a result of in-situ experiments, the amount of sludge discharge was reduced by 30%, and it was confirmed that the improved diameter, strength, and coefficient of variation were equivalent to those of the conventional specifications.
The study deals with the damage control system of wooden houses using wood friction-based dampers subjected to earthquake motion. In this study, wood friction joints were developed to introduce damping into wood shear walls. Shaking table tests were also conducted to investigate the seismic performance of two-story timber structures composed of plywood shear walls, plasterboards and timber shear walls using high damping devices. The purpose of this study is to propose an estimation method of the required quantity of the friction damper to satisfy the restriction value of the story drift angle for the continued use after earthquake motion.
A simple calculation method is proposed for predicting the elastic and plastic behavior of moment resistance timber frames without using non-linear numerical analyses by wire frame modelling. The behavior of timber frames which have multiple stories and spans can be calculated by hand or spreadsheets based on flexural stiffness of members and spring behaviors of joints. The accuracy of the calculation method have been verified by comparing calculation results with results of experiments and non-linear numerical analyses under several different conditions. This calculation method can be used for estimating the structural behavior of timber frames as well as numerical analyses.
The CLT buildings using moment-resisting joint composed of CLT walls and composite glued laminated beams(hereinafter “CLT wall-beam joints”) show better seismic performance due to the moment-resisting joints of the wall and beam joints, in addition to the CLT wall and base joints. Therefore, this study aimed to address the following issues: 1) to propose a calculation method to predict the bending performance of CLT wall-beam joints from the performance of a single connector, 2) to confirm the performance of a single connector and the CLT wall-beam joints by testing, and 3) to compare the test results with calculation results.
NLT (Nail-Laminated Timber) fabricated with dimension lumber tightly nailed together and widely used in North American countries is one of mass timber materials. In order to utilize this material in Japan, a manufacturing and the design methods were developed in this research. Full-scale tests were conducted to verify the design method and obtained satisfactory results that the experimental values of the stiffness and the ultimate strength were a little higher than the calculated values.
We developed a timber semi-rigid frame construction system composed with coupled glulam members jointed by screws with steel side plate and high-tensile bolts. We conducted cyclic loading test for the single screwed joint of glulam with steel side plates, tensile test for the full-thread screwed joint embedded in glulam using reinforcement to restrain splitting failure of glulam, the bending tests for the moment resisting joints to confirm the characteristics of the failure behaviors, the reinforcement efficacy by the full-thread screws and the estimability of their mechanical behaviors from single screwed joint properties.
In this study, several shapes of connection between columns and Nageshi beams with reinforcements were proposed and experimentally verified as a seismic reinforcement method for traditional wooden buildings. All specimens showed stable restoring force characteristics with no brittle fracture until the ultimate deformation state. In the case of specimens with gaps between the Nageshi beams and timbers filled in the gaps, there was almost no decrease in the strength when the gaps was small. When the orthogonal Nageshi beams was used, the yield load was about 40% to 50% of the calculated value, assuming an ideal condition.
Seismic performance of timber shear walls is generally confirmed through experiment which is provided in the standard. However, the strength and deformation capacities are clearly related to the loading protocol, and such a fatigue behavior is not well-understood so far. In this paper, plywood sheathing wall having 12mm thickness of plywood is tested, and the fatigue behaviors coming up on force-deformation relation and equivalent damping ratio are evaluated.
I conducted comprehensive research to clarify the issues related to seismic safety of group of historic buildings in Hanazawa village. First, I focused on the ground and the masonry retaining wall, and clarified their basic characteristics from field surveys. Next, in order to recognize structural characteristics of traditional buildings, I carried out the visual investigation to confirm the wall plan and the situation of expansion/renovation, and the microtremor measurement for the buildings. Furthermore, the seismic performance of traditional buildings was verified by calculating the response and the limit strength, and the response values to a large earthquake were clarified.
In order to investigate the structural performance of the CLT-S hybrid structure with several types of CLT-S connections to improve the hysteresis behavior, experiments of CLT-S hybrid structure frame were conducted. In the new CLT-S connections, the reduced section parts of inserted steel plate restrained for buckling provide improved behavior against cyclic axial forces due to bending moment in CLT panels. From the experiment result, it was found that the new CLT-S connections improve hysteretic property of the frame and energy dissipation efficiency compared to the existing connections.
Mechanical properties of new origami inspired reinforcing and hysteresis-damping device using thin steel plates are proposed and investigated. Results of FEA and full-scale experiments are indicated and discussed. FEA showed better stiffness, yield strength and efficient plasticized area of the device than simple flat pates, due to three-dimensional geometrical resistance system. The experimental results agreed well with the FEA results. Damping of the device is also examined and discussed.
The authors conducted horizontal loading experiments on a two-layer fishbone-shaped model consisting of timber assembly columns, CLT floors and glued in rod joints as a basic research on the development of a wooden flat slab structures for medium-scale buildings. Horizontal loading experiments show the kinematical properties of wooden flat slab structures. Further, semi-rigid joint frame model considering bending stiffness and shearing rigidity was constructed and the applicability of semi-rigid joint frame model was verified by conducted load incremental analysis.
In this study, structural tests were performed on the specimens that contained the de-bond of longitudinal rebars at the four corners of the RC beam with a guaranteed hinge position. Through this test, it was confirmed that the de-bond of longitudinal rebars at the four corners of the RC beam does not significantly affect the structural performance of the RC beam member, including the restoring force characteristic and energy dissipation capacity. Moreover, the cracks were concentrated on the hinge-side of the de-bond area, and the number of cracks in the de-bond area was suppressed.
This report showed experiment results of beam-cloumn joint with different floor levels on beam. The purpose of this experiment is comparing the effect that the anchorage type exerts on ultimate shear strength of beam-cloumn joint. The experiment was conducted on one direction gradual increase loading, and two specimens with different anchorage types of the main bars of beam were designed. The conclusion is as follows: Compared to the specimen with development by 90-degree hook, the ultimate shear strength of the specimen with straight development was increased, however the strength was more dramatically deteriorated.
The Reduced Beam Section (RBS) is used as an effective method to improve deformation capacity on steel moment frames. However, study on flexural rigidity on composite beams with RBS has not been performed. This study proposes a useful method to calculate the equivalent flexural rigidity of composite beams with RBS on lower flange. The formulas were derived based on the energy method. FEM analysis was used to verify the theory. In addition, an eigenvalue analysis on a building model using the equivalent elastic beams with RBS was performed as an example.
In recent years, an architecture made of natural resources attracts more attention. In some areas of Europe, “Rammed earth’’ has already been used for building structure. To spread the rammed earth in Japan, the structural system with seismic resistant mechanism is needed. This study suggests composite structure with rammed earth and steel framework. In this paper, the horizontal loading test is conducted. From test result, specimen with rammed earth presents high strength and rigidity by comparing the steel specimen, that is, the combined effect is confirmed. Furthermore, the proposed analytical method of strength can estimate the test result.
Experimental and analytical investigations were conducted to obtain basic knowledge on the influence of the charge shape on the local failure of concrete slabs subjected to contact detonation. The results showed that the damage depth of the slabs varied depending on the charge shape, and the effective amounts of explosives based on Kennedy’s knowledge might be a useful parameter for evaluating the damage depth. However, it was considered necessary to develop another parameter to evaluate the flying velocity of the concrete fragments due to the spall failure.
In steel-framed buildings, the necessary fireproof coating is applied against an expected fire. There are many types of fireproof coatings, but in many cases sprayed rock wool is used. In recent years, many ceiling-less spaces have appeared in restaurants and the like, but in many cases, paint is applied on the spray rock wool from the viewpoint of design. Therefore, in this study, a material test was conducted to understand the effect of the paint applied on the sprayed rock wool of the fireproof coating on the fireproof performance.
In this report, the results of performance confirmation of fire-resistant wood members and beam-column joints, and the contents of application cases were reported. The main points are as follows. The refractory sheet was found to have the effect of reducing the temperature of the reinforced gypsum board. It was confirmed that the fire-resistant wood columns, fire-resistant wood beams, fire-resistant wood members, and column-beam joints made of Pc joint members incorporating fire-resistant foam sheets of heat-foamed material have 1 hour of fire resistance without carbonization in the core material.
There are few energy surveys targeting single-person dwellings such as dormitories. In this research, the energy consumption and the lifestyle of residents for university student dormitories were surveyed. As a result, it was found that the energy consumption per occupant was about 27 GJ / year when electricity was converted into primary energy. The relationship between the energy consumption of private rooms and the lifestyle of the residents was analyzed using the quantification type I, and what kind of lifestyle affected the energy consumption was examined.
Small-scale authorized nursery schools are receiving recognition as a promising solution to the problem of long waitlists for nursery schools. It was measured the amount of reduction in floor impact sound pressure level caused by the car-tire source using a reverberation room with upper and lower floors. It was possible to improve the performance of the amount of reduction in the floor impact sound pressure level by a maximum of 14 dB in the 63 Hz octave band when using pieces of storage furniture with tatami on top by using appropriate vibration control measures and sound insulation measures.
We have proposed a method for estimating the vibration acceleration level of the floor structure with high accuracy by preventing the mounted resonance of the carpet floor. In this paper, using the method proposed in this study, we conducted an experimental study on thick tatami, unlike carpets. As a result, it was suggested that when a tatami with polystyrene foam as the core material, which is generally and commonly used, is installed on the concrete slab, the mounted resonance is prevented and the vibration acceleration of the concrete slab is accurately calculated.