Abstract:MJS method, invented by Japanese in 1990s last century, is a new all-round type reinforcing and consolidation method for ground improvement. Since 2008 when MJS method is introduced to China, MJS method has been widely used in the field of pit excavation, structure protection and ground improvement with good results. The main purpose of this article is to review and introduce MJS method fully relatively, including invention background, principle, characters, technics, equipment etc. In addition, applications of MJS method in Japan and China are reviewed, especially the great achievement in our country. By reading this article, readers will understand MJS method comprehensively.

Abstract:For the proposes of fragility analysis, a typical configuration of multi-span simply supported concrete box girder bridges are selected as analytical object from the statistics of as-built high-speed railway bridges in China. A set of bridge samples, in which five uncertain parameters are considered, are established using the trial and error method based on the Latin hypercube sampling. A portfolio of recorded ground motions divided into bins are assembled, and matched with bridge samples. Then nonlinear time history analyses are performed to capture the responses of structure. Damage states of bridge components are defined, and probabilistic seismic demand models are formulated by quadratic regression analysis for the ratios of the capacity and demand. Fragility curves of bridge components are developed consequently and the fragility of bridge system is evaluated using a single estimate for the second order bounds method. The results show that PSDMs formulated by quadratic regression are better than that by traditional linear regression. The expansion bearing and the column piers of this bridge type are fragile under earthquake excitation. A single estimate for the second order bounds method is preferable to evaluate the fragility of bridge system, and is easier to use than the first order bounds method.

Abstract:The control of settlement after construction of subgrade for high speed railway is a difficult problem, and the study of dynamic load is still in the stage of numerical calculation and experiment. Therefore, relying on the construction and operation monitoring data of Shanghai-Nanjing intercity railway, test values of settlement under the action of dynamic load are used to analyze the settlement characteristics caused by dynamic load based on the method of separating the settlement caused by static and dynamic load. The results show that settlement caused by dynamic load has limited contribution to the operation data of the settlement, while it is not the main reason causing settlement large. Different geological conditions and construction of embankment height have little influence on the settlement caused by dynamic load. Settlement rate caused by dynamic load is faster and reaches the maximum in the early development of the operation, then gradually decreases. The settlement tends to be stable after operation four years is about 2~3 mm.

Abstract:In order to improve seismic behavior of one-shaped concrete squat shear wall with built in vertical steels in the rectangular section, two concrete squat shear wall specimens were designed and fabricated with an aspect ratio of 1.0, which enhanced by horizontal steel plates other than built-in vertical steels in the sections. Mechanical behaviors of those specimens were tested under reversed cyclic lateral loads and a constant vertical load. The test results were compared with a specimen without enhancement of horizontal steel plates, which indicates that the peak lateral loads of specimens with steel plates are improved significantly. The ultimate drift ratios of specimens with steel plates are improved by 20% and are larger than 1/100, which meets the relevant specifications. Steel plates change the failure modes of specimens, and the total energy dissipation of specimens with steel plates are improved substantially. The enhancement should be kept in a suitable range, otherwise new weak areas will be formed if the horizontal steel plates are too strong.

Abstract:The expression for the energy of rockburst is derivated based on the Energy Balance Theory. The influencing factors, which accounts for the location,area and the averaged ejection velocity of rock fragments of rockburst zones of underground rockmass are determined quantitatively. It was found that the area of rockburst zones and the averaged ejection velocity of rock fragments decreasing as the increase of lateral pressure coefficient when the ratio of the horizontal stress and vertical stress of surrounding rock is less than 1, otherwise on the contrary. The area of rockburst zones decreases as the increasing diameter of grain of rock, and the ratio of modulus before and after peak loads and density of cracks, fracture toughness of rock, but those increase with the increasing Poisson's ratio. The averaged ejection velocity of rock fragments decreases with the increase of diameter of grain of rock, Poisson's ratio, the ratio of modulus before and after peak loads, but increase with fracture toughness of rock, and increase firstly but then decrease, and towards a fixed value with increasing density of cracks. The proposed approach provides a new idea for the quantitative analysis of rockburst.

Abstract:To investigate the influences of cyclic loading history to rate effect of water-saturated concrete under pressurized water environment, the conventional triaxial compression test was carried out in different strain rates(10^-5/s、10^-4/s、10^-3/s、10^-2/s)with the water-saturated concrete samples(in the water environment with 2MPa confining pressure)which had experienced different cyclic loading times(0、25、50、100 times), the change law and mechanism of the basic mechanical parameters such as peak stress, peak strain, elasticity modulus and energy absorption ability were analyzed. It was found that the peak stress, elasticity modulus and energy absorption ability of water-saturated concrete samples all increaseed at first and then decreaseed with the increasing times of cyclic loading, and the turning point of peak stress and energy absorption ability came close to the direction that cyclic loading times became bigger with strain rate increasing, but the peak strain decreased generally. The peak stress, elasticity modulus and energy absorption ability of the concrete samples which experienced same cyclic loading times all increased with the strain rates increasing and the rate effect was more conspicuous with cyclic loading times increasing, the elasticity modulus showed the change law on the contrary.

Abstract:To investigate the seismic behavior of steel reinforced concrete cross-shaped columns, five specimens with different axial compression ratio and form of steel layout were tested under low cyclic loading. Hysteretic curves, skeleton curves, ductility performance, rigidity degeneration, and energy dissipation capacity were analyzed. The effects of axial compression ratio and form of steel layout to specimens were compared and analyzed. The results showed that with axial compression ratio increasing, the bearing capacity of specimens became higher, but the ductility and energy dissipation capacity turn to be lower, and the rate of rigidity degeneration trended to be quicker. Compared with ordinary reinforced concrete cross-shaped columns, the hysteretic behavior of concrete cross-shaped columns reinforced when shape steel was improved, the rigidity, ductility performance, bearing capacity and energy dissipation capacity were enhanced, the degree of failure were alleviated. Therefore, the seismic behavior of steel reinforced concrete cross-shaped columns was improved significantly. The seismic behavior of specimens of T-shaped steel combined with square steel tube was superior to solid-web steel reinforced concrete cross-shaped column except rigidity degeneration.

Abstract:Three RC beams strengthened with carbon fiber reinforced polymer (CFRP) plate and one contrast beam were tested to investigate the flexural property. The effect of prestress and the anchorage on the performance was analyzed in terms of bending capacity, stiffness, development of crack, utilization rate of carbon fiber reinforced polymer plate. The test results showed that the prestressed CFRP plate can significantly improve flexural capacity of the specimens, utilization rate of CFRP plate, and deformation properties, decrease crack width, and the structural ductility was reduced which we should consider when designing reinforcing components. Two types of anchorage could meet the requirement of operational phase, Considering all aspects, the MJ-2 anchorage without slot was more applicable.

Abstract:To explore the influence laws of random eccentricity on seismic capacity reliability of RC columns with design reinforcements, the failure function and the formula of the influence coefficient of reinforcement are obtained and expressed by multiple normalized design parameters with an analytical method. Based on the requirements on column reinforcement in codes, the variation laws of the influence coefficient of reinforcement are analyzed with multiple design parameters(e.g. load effect ratios) within common ranges. Considering the random properties of eccentricity and the prescribed probability models of horizontal earthquake action, vertical gravity load, concrete strength and steel strength, etc., the seismic capacity reliability is obtained for RC columns with tension failure by the Monte Carlo method. The results indicate that the variations of the influence coefficient of reinforcement are large for different combination cases of design parameters; the seismic capacity reliability is improved less with the increase of reinforcement for the columns with a smaller influence coefficient of reinforcement; the reliability is improved dramatically with the increase of reinforcement for the columns with a larger influence coefficient of reinforcement.

Abstract:The damage extents identification of members in space truss is an important part in health detection of space trusses. It plays a decisive role for the safety and applicability of truss structure. Based on the location of members damage, through experiment and simulation method, the analysis method of use transient dynamic response for the study about the damage extents identification of members in four pyramid space truss is put forward. The displacement-time history curve is educed about the different damage extents of members' node, and the curve-fitting analysis is made using Matlab. It shows that the displacement-time history curve of members' node can approximate synthesis of linear in different damage extents. Through the analysis abut slope of the line and the damage extents of members, it can educe the relation about the slope value, displacement-time history curve about top chord, bottom chord, wed member both ends of the node, and the damage extents of members. It can accurately identified the damage extents of four pyramid space truss members by the relation, which can be referenced in the damage extents identification of members in truss structure of practical engineering projects.

Abstract:In order to facilitate the calculation of the vertical natural frequency of the asymmetric suspension bridge of the two towers, the Rayleigh method is used to derive the approximate expression of the first order bending vibration frequency under the influence of the stiffness of the main tower. The influence of the stiffness of the expression, and finally the feasibility of this formula is verified. The results showed that the stiffness of the main tower has an effect on the first-order symmetrical vertical bending frequency of the structural system and has no effect on the first-order anti-symmetrical vertical bending frequency. The main tower stiffness can be calculated by the influence coefficient of the main tower. The degree of error between the solution and the finite element solution is in the allowable requirement of the initial conceptual design stage. The approximate expression of the fundamental frequency is deduced in this paper.

Abstract:The light-gauge tube truss beam is formed by connecting the upper chord, the lower chord, and the Z clip through screws. The failure of the tube truss beam is mainly due to the local buckling of the upper chord, not the tensile yielding of the lower chord. In order to make full use of the material, reduce project costs and manufacture the lower lord more easily, a new type of tube truss beam with U-shaped lower chord is proposed in this paper. Firstly, three tube truss beams with different forms of the lower chord are tested, the effect of upper and lower chord section form, sectional area and stiffness on failure mode, bending stiffness and ultimate bearing capacity of the whole truss beam are examined. Secondly, the finite element analyses of six tube truss beams are carried out, considering different section forms, sectional areas and opening directions of the lower chord. Testing and finite element analysis results have verified the feasibility of using the U shaped lower chord,and the normal U shaped section is better than an upside down one.

Abstract:In order to investigate the feasibility and effect of expansive soils improved by industrial waste that iron tailings sand, the basic physical properties and swelling characteristics and unconfined compressive strength of improved soil were study by laboratory test.Besides,by means of SEM,the microstructure of series of samples is studied.The result of test indicated that the marginal moisture content and plasticity index of improved soil decrease with the increase of tailings sand content; free swelling ratio and loaded swelling ratio and swelling pressure also decrease with the increase of tailings sand content.The unconfined compressive strength and cohesion increases with the increase of tailings sand content,but it decreases when tailings sand content more than 30%;internal friction angle increase with the increase of tailings sand content. It was found that the structure of improved soil in the most stable state when tailings sand content is 30% by observing the results of SEM.It is shown that the effect of expansive soils improved by iron tailings sand is obvious.So for the improvement of expansive soils provides a new method. Considering all the indicators, the optimum content of iron tailings sand that improved expansive soils should be 30%.

Abstract:Multi-zone airflow modeling uses some simplifying assumption which ignores the influence of airflow rate by different door position. And it would lead to large error in airflow rate calculation. This paper compares airflow rate through the models with door position in the middle and at the sides in different window opening ratio conditions by wind tunnel experiment. After comparing simulation model result with experimental model result, the numerical simulation is researched in different conditions:no door、front door、back door、front and back doors. The airflow rate through the models with different doors position is compared. Experimental results show that the effects of airflow momentum can't be ignored but only the window opening ratio small enough, or the free space jet or confined space jet models need to be compared, and the largest jet length is used to optimize multi-zone airflow model's results.

Abstract:A theoretical and experimental measurement analysis on air filter of fan coil unit and fresh air system was conducted through establishing a mass balance equation. In this paper, a certain building in Xi'an is taken as an example, the outdoor PM2.5 concentration is calculated based on "no assurance of 10 days". The results show that the synthetic fiber of G3 or G4 air filter can be used in return air of FCU when the fan pressure is 50-80pa, and the G2 or G3 air filter can be used when the pressure is 30-50pa. Meanwhile, G4 and F7 or F8 two-stage filtration can be used in fresh air system when equivalent filtration efficiency air purifier should be installed.

Abstract:Water absorption of porous materials were influenced by sea salt. It would lead to changes of the efficiency of the low-energy buildings using passive evaporation cooling technology. To find the relations between the concentration and the water absorption characters, we conducted water absorption tests through partial immersion method with common porous fire-clay tiles and NaCl solution with different concentrations. Compared to the pure water case, tiles' capillary absorption coefficient was higher by 17.57% in solutions with the concentration of 3.5% by weight (same below), and lower by 12.17% in 26.3% solution. Pure water absorption reduced while concentration increased. Capillary saturated water content was lower in 3.5% solution than in pure water by 2.50%, and lower in 26.3% solution than in pure water by 16.18%. Continuous absorption for 24 hours, the pure water content was lower in 3.5% solution than in pure water by 3.18%, and lower in 26.3% solution than in pure water by 20.51%. In summary, salts would weaken the water absorption ability of the tiles. The higher the concentration of the solution was, the absorption would be weaker. As a result, water absorption of the tiles in the coastal saline environments would be different from the inland situation.

Abstract:Thermal conductivity is one of the most important hygrothermal properties of building materials which depends on temperature and moisture content. The one-variable linear function is usually used to describe the influence of either temperature or moisture content on the thermal conductivity when the other one is fixed. However, for real situations temperature and moisture content have simultaneous influence. The thermal conductivities of five typical building materials-expanded polystyrene (EPS), mineral wool, concrete, adhesive mortar and rendering plaster-were measured with the guarded-hot-plate apparatus at different temperature and moisture content. Results show that the two-variable linear function is sufficient to describe the coupled influence of temperature and moisture content on all studied materials. The interaction between temperature and moisture content is negligible. For weakly hygroscopic and capillary materials such as EPS and mineral wool, the two-variable linear function can be simplified to the one-variable linear function of temperature.

Abstract:Experiment was carried out to investigate the impact of natural aging of high reflective coating on its thermal insulation performance in hot-summer and cold-winter zone. White reflective coatings and gray coatings were applied respectively on two identical top-floor rooms of an office building in Chongqing with same floor area, envelope material and orientation. Thermal insulation performance was investigated by analyzing the records of three consecutive sunny day in July 2014 and July 2015. The results showed that reflectivity of reflective roof and thermal insulation performance decreased after one-year natural aging. When the room was conditioned with the setting point of 26℃, average temperatures of interior and exterior surfaces decreased by 3.2℃ and 4.2℃ respectively, and the energy consumption of air conditioners decreased by 0.03 kWh/m²·d in July 2014 compared with those in July 2015. When air-conditioners were off, there was a decrease of 2.5℃ in average indoor air temperature in July 2014 compared with those in July 2015.

Abstract:The air tightness of 5 different types of common used windows in Tianjin University were measured by blower window method; the measured windows including PVC single, PVC double, aluminum alloy casement, aluminum alloy sash and aluminum alloy slanting sash windows. We totally measured 15 windows with every type 3 windows. The pressure difference between window and outdoor air was controlled in 0~60 Pa during every test. According to the measured results, we compared the influence of window frame material, opening form, function time and outdoor environment on the performance of air tightness. With 5 Pa pressure differences, the infiltration rate of aluminum alloy slanting sash windows was 35~40 m³/h, others were 10~20 m³/h. The window air tightness had a great effect on window leakage coefficient C but less effect on pressure coefficient n, and the coefficient n of all the 15 windows was 0.5-0.6. The air tightness of the 15 windows was calculated through GB/T 7106-2008, the PVC double windows were the tightest with an infiltration rate of 5.17 m³/h·m², while the aluminum alloy slanting sash windows were worst and its infiltration rate was 17.9m³/h·m². Based on the results of 3 repeatability tests, we found the outdoor climate influence was negligible on the test results when the pressure difference was larger than 15 Pa. The time interval was one week for every repeatability test, most of the test error was less than 15% between every two tests.

Abstract:An experimental device is established in this paper, the operating condition of ground source heat pump under the condition of soil thermal imbalance in cold region in winter is simulated. The experiment studies the distribution characteristics of the frozen soil area around the buried pipe, and gets the average moving speed of freezing front. The results show that the distribution of frozen soil area is asymmetric. When the fluid inlet temperature is -15℃ and buried depth is 350,700 and 1 050 mm, the average moving speed of freezing front is 5,5 and 6.67 mm/h in the heat response areas of 40~60 mm, and the average moving speed of freezing front is 1.54, 1.82 and 1.82 mm/h in the heat response areas of 60~80 mm. The frozen soil to a certain extent in favor of heat transfer between buried pipe and surrounding soil, so the frozen soilshould be considered in the design of GSHP in cold area.