Abstract:Using shear overstrength factors is one of key earthquake resisting measures for reinforced concrete (RC) frame members,which aims to ensure the safety of structures under rare earthquakes. The shear overstrengh factors for different seismic grades have been provided in Chinese code,while little research has been conducted up to date which focused on the actual effect of shear overstrength factors. Three regular RC frame structures were designed according to the current code,which respectively located in intensity region 7(0.15g),8(0.20g) and 9(0.40g). Nonlinear dynamic analyses under rare earthquakes were finished.The ratio of the shear demand under rare earthquakes to the average shear capacity for beams and columns was calculated to identify the effectiveness of the shear overstrength factor. The rule is that the ratio of more than 90% components are less than 1.0. The adjustments were made in the case when the shear overstrength factor did not meet to the rule,which continued until that the factor is up to grade. The result proves that shear overstrengh factors for RC frame beams can keep on; the shear overstrength factors for first seismic grade is oversized,while that for second and third seismic grades can not satisfy the shear demand. Two sets of schemes for column shear overstrengh factors are proposed based on further analysis.

Abstract:An experimental investigation was conducted to study the shear strength and cracking behavior of beams made with self-consolidating concrete (SCC) as well as normal concrete (NC). A total of 12 flexurally reinforced concrete beams which consist of 8 beams with self-compacting concrete and 4 beams with normal concrete, with no shear reinforcement, were tested under mid-span concentrated load until shear failure occurred. The main variables in the test are concrete strength and shear span ratio. While, based on the test data in this study, several shear strength models:GB 50010-2010, Zsutty' formula, ACI 318-11 were analyzed and compared. The shear experimental test data of 130 self-consolidating concrete and 798 normal concrete simply-supported rectangular cross-section beams without web reinforcement were collected to compare the shear capacity between SCC and NC beams. The results show that:In terms of crack morphology, crack progression, the behavior of the SCC and CC beams is virtually identical, and the inclined section of SCC beams are more smooth; The calculated results of Zsutty' fit are closest to the experimental results; the results of GB 50010-2010 are also in good agreement, but are not safe; the deviation of ACI 318-11 is larger; and the ultimate shear strength of SCC beams is found to be slightly lower than the NC beams.

Abstract:The in-situ test was carried out for the environmental vibration response of the surrounding buildings and the ground caused by high speed railway trains, the spectrum analysis method was used to study vibration characteristics of the surrounding buildings and ground. The environmental vibration levels of high speed railway was analyzed and evaluated in combination with the vibration control standard of urban railway. The results of study show that the environmental vibration frequency caused by the 270 km/h high-speed trains is mainly concentrated on the range of 25~60 Hz.The vertical vibration of building is larger than the horizontal vibration, the maximum of Z-level of vertical vibration is 70.62 dB. The second vibration in the building has a obvious height amplification effect, the maximum Z-level of vertical vibration on the top floor of the building is about 1.094 times of that on the first layer. The ground vibration is obviously larger than that of the surrounding buildings, but the similar changing law is shown between the ground and the building, the maximum of vibration level of division frequency on the ground can up to 92 dB, but the maximum of vibration level of division frequency on the buildings can only up to 80 dB. The environmental noise of high speed railway is up to 92.8 dB, more than the severe pollution standards of city environmental noise. Environmental noise pollution caused by high speed railway is greater than the impact of environmental vibration, the corresponding noise reduction and sound insulation measures should be adopted to effectively control the level of environmental noise.

Abstract:In order to investigate the fatigue behavior and fatigue life prediction method of butt weld on cast steel joint, a series of fatigue tests were conducted on welded specimens of cast steel and hot rolled steel with a common welding type. Relationships between stiffness, displacement and fatigue life stage were obtained. Fatigue failure mechanism was revealed based on the phenomenon of fatigue process and fracture surface observation resulted by scanning electron microscope (SEM). In addition, fatigue life prediction was carried out with effective notch stress method (ENSM). In consideration of the influence of mean stress and residual stress, improved effective notch stress method (IENSM) was proposed, and the predicted values were compared with the test data. The result shows that:The fatigue process of butt weld on cast steel joint can be divided into two stages:stable stage and fracture stage. The stable stage possesses more than 80% fatigue life, while the fracture stage maintains less than 20%. ENSM can predict the changing trends of the fatigue life to some extent, but the results are non-conservative for engineering. However, IENSM can provide safe assessments.

Abstract:Excavated foundation of transmission line have been used in mountain weathered soft rock, including column excavated pile model, jar shape embedded model and belled shaft digged model. Field prototype tests of 17 group different models have been carried out for highly weathered argillaceous sandstone. The foundation load bearing characteristics and failure pattern are analyzed based on test data. Load displacement curves show that the distributions are linear for shallow foundation, but the distributions are slowly varying for deep foundation. Based on the surface displacement variation rules, the characterization of foundation overall damaging reflect the significant surface fracture, and the foundation and its surrounding soil are pulled out. The foundation rupture angle reduces quickly with the increasing of foundation depth. But the rupture angle remains constant when the foundation reach a certain depth. By calculation of the test data, the rock equivalent ultimate shear strength of weathered soft rock is 32 kPa. According to the ultimate uplift capacity of unit concrete volume, the economical benefit of the belled shaft digged model foundation is remarkable.

Abstract:In order to obtain frost heave and thawing settlement of frozen soils behavior, an underground connected aisle was studied through the model test based on similarity theory. The results indicate that, the soil temperature firstly decreases rapidly, then increases and maintains 0℃ for a while, at last continues to slowly rise to room temperature in the whole process. The soil pressure value goes up firstly and then goes down, and that of vertical pressure increases exponentially with the increasing of depth, meanwhile the distance from the freezing tube is more closer, the horizontal pressure is more bigger. Contrast with frost heave displacement, the thawing settlement value is greater, and the vertical displacement is more significant than the horizontal as well. In positive frozen period, the temperature reducing rate becomes slower, the greater depth and closer distance from the freezing hole, the greater decline speed and amplitude come up. Unlike vertical restriction soil always increases, the soil pressure value of unlimited presents a first increasing and then decreasing trend, while the variable rate is bigger with complete restriction situation.

Abstract:The lateral collapse-resistant capacity of the structure is the foundation of structure seismic performance assessment.Four seismic performance factors,namely,the yield ratio, the system overstrength factor, the ductility factor and the malleability factor, are used to evaluate lateral collapse-resistant capacity of 12 codified designed RC structures. The influences of the distribution of lateral loadings and seismic fortification intensity are considered in the Pushover analysis. Lateral collapse-resistant capacity of the structure is evaluated with capacity curve and seismic performance factors. The results show that lateral collapse-resistant capacity of the structure can be analyzed by seismic performance factors from two aspects, strength storage and deformability. The influence on lateral collapse-resistant capacity of the structure of lateral loadings increases with the rise of seismic fortification intensity and the height of structures. Seismic fortification intensity has little influence on the yield ratio and the malleability factor, but has major influence on the system overstrength factor and the ductility factor. With the increase of fortification intensity, the overstrength coefficient decreases and the ductility coefficient increases.

Abstract:In order to adapt to the requirement of sponge city construction for high durable pervious concrete, pervious concrete mixed with low-quality active mineral admixture and pervious concrete mixed with Polypropylene Thick Fiber(PPTF) are developed. In the early stage, basic performance studies have been carried out, and on this basis, it is continued to conduct durability studies under complex attack environments. By the method of full-immersion, experiments last for 300 d. Macro-observations involve the deterioration regularity of both compressive strength and flexural strength with attack time. Micro-observations involve microstructure of cemented layer by SEM and chemical composition of cemented layer by EDS. Under complex attack environments, the change of pervious concrete micro-structural is in accord with macro-mechanical behavior. Combined basic performance with durability, pervious concrete mixed with both low-quality silica fume and low-quality fly ash and pervious concrete mixed with zigzag PPTF of 3 kg/m³ are preferred recommended. This two kinds of pervious concrete meet the application requirement of light traffic pavements such as existing residential area road, sidewalk, city square, stadium, outdoor parking lot, landscape road, which durability is good.

Abstract:A stadium of primary school was taken as an example, by establishing the finite element model with ANSYS, the vertical vibration of long-span prestressed secondary beams floor system worked with different jumping frequency, number of persons and jumping numbers were analyzed. The results show that, compared with the measured values, the modified half-since-power model has a relative error of 12.98%, which is closed to the measured values; vertical vibration acceleration caused by different people jumping synchronously increases with number of persons rising; considering the people can't jump synchronously the multiplication factor is introduced to correct the jumping loads model.

Abstract:The sintered shale ceramsite lightweight aggregate was treated by the atmospheric pre-wetting and pressurized pre-wetting. The bonding properties of the lightweight aggregate concrete and the steel bar under different freezing and thaw cycles were investigated. The mechanical properties, bond strength, load-slip curve and bond toughness of the specimen under pre-wetting were analyzed. The experimental results show that the mechanical properties and ultimate bonding strength of the preheated wetting specimen were lower than those of the pre-wetting specimen, and the failure modes of the pre-wetting specimen were all fractured. The ultimate bond toughness of A_u decreases with the increase of freeze-thaw cycle, and the residual toughness of A₈₀ and A₆₀ is relatively flat, but the bond toughness of the pre-wetting specimen is higher than that of pressurized pre-wetting specimen.Under the freezing and thawing environment, the bond toughness degradation model and the degenerative model of the residual strength and compressive strength of the steel fiber lightweight aggregate concrete were established. The calculated values of the model were in good agreement with the experimental values.

Abstract:There is shallow and strong permeable stratum in dike foundation, which can form a prior seepage channel, and fluid head potential isn't weakened by this channel, it is easy to cause dike foundation piping failure, and the study of failure mechanism of dike foundation piping is not clear, it still needs further study. Sand tank test is used to simulate embankment foundation influent in this paper, water block stage is drived up in test, and observing the phenomenon of fine particle loss in sand, and the key parameters of seepage discharge, seepage gradient, piezometric tube head, grain composition of sand, cone resistance and settlement are analysed. The test results show that sand on the shallow and strong permeable stratum occur piping failure when water block stage increases to 48 cm. Piping failure is divided into steady seepage stage, internal erosion of fine particles stage, internal erosion of relative fine particles stage and piping failure expansion stage. The internal erosion of fine particles in process of piping failure, and cone resistance has reduced, sand has settled, and settlement heavily focus on internal erosion of relative fine particles stage. The porosity and permeability coefficient of sand, seepage discharge and seepage gradient increase when fine particle loss. This reseach results can offer theory reference for similar projects.

Abstract:It is helpful to investigate the non-uniform distribution of chloride after electrochemical chloride extraction by ascertaining the distribution characteristics of electric field during electrochemical chloride extraction. In order to study the effect of electric field on the migration of chloride ions, a shielded buried electrode array was used to ascertain the distribution characteristics of chloride and electric field around reinforcement nets. The results show that the electric field in concrete affects the migration of chloride ions, when a region with strong electric field, chloride ion migration rate is high, residual chloride ion concentration is low, when a region with week electric field, chloride ion migration rate is low residual chloride ion concentration is high.

Abstract:The triple-shear unified structured constitutive model is proposed for the undisturbed saturated clay in normal consolidation based on the disturbed state concept, in which the relative intact state is characterized by the non-linear elastic model, and the fully adjusted state is characterized by the elasto-plastic model built with the combination of the triple-shear unified failure criterion and the modified Cam-clay model in the critical state soil mechanics. The coordinate translation is presented to describe the influences of the cohesion on the soil mechanical properties better. The proposed model can overcome the shortcomings of the modified cam-clay model with the definite failure stress ratio without considering the soil cohesion, which can't reflect the practical differences of strength properties under different stress states and soil cohesion. The advantage is that the new model could show the practical effects under the different stress states acting on the saturated structured clay with different cohesion better. It is shown that it can describe the effects of intermediate principal stress, rang changes of stress and difference between tension and compression. In order to verify the model proposed here, comparisons between the numerical simulations and experimental results under conventional tri-axial compression to the Jiangxi undisturbed lateritic clay was made,which results show that the proposed model could reflect the mechanical and deformation characteristics of the Jiangxi undisturbed lateritic clay well.

Abstract:Model tests on the uplift bearing capacity of jet grouting soil-cement-pile strengthened piles (JPP for short) under four different combinations were carried out based on the self-developed large-scale pile foundation load test equipment system, the model piles were buried by sand pour method. The test results show that:1) different combinations have a great effect on uplift bearing capacity of JPP piles, lower combination carries the highest uplift bearing capacity, its bearing capacity is nearly 1.1 times of three-segment combination, nearly 1.3 times of two-segment combination, nearly 1.4 times of upper combination. 2) the total side resistance of lower combination is the maximum in four combinations under the ultimate uplift capacity. 3) in the process of uplifting test, axial force decreases along the pile depth under each load; the upper lateral resistance reaches firstly the ultimate value and tends to be stable, with the load increasing, the upper lateral resistance takes gradually a full play. (4) the lateral resistance increases gradually and reachs the ultimate value when the relative displacement is small for sand, upper lateral resistance tends to be stable after being ultimate value; lower lateral friction, however, has the increasing trend after reaching the ultimate. In the whole, the relationships between side friction and relative displacement show the hyperbolic model.

Abstract:Six rectangle steel tube confined concrete columns were investigated experimentally under axial compression. The experimental results show that:The rectangle steel tube can effectively confine internal concrete and obviously improve the peak stress. In addition, the descending branch of confined concrete stress-strain curve is gentler and the ultimate deformation ability of concrete is improved effectively. On the basis of experiments, a method to calculate the effective transverse confined stress provided by the rectangle steel tube was proposed through analyzing the strain of steel tubes and the stress state of core zone concrete. Furthermore, a model to determinate the stress-strain relationship of rectangle steel tube confined concrete under axial compression was put forward reference to the Mander's model. Computation results of the stress-strain curve of rectangle steel tube confined concrete were in good agreement with the experimental results.

Abstract:Variation of mesoscopic pore structure for soft soils is the primary cause of the macroscopical deformation. In order to study the variation of mesoscopic pore structure of soft soil as well as the correlative mechanism with macroscopical deformation during electro-osmosis, some electro-osmotic experiments were performed using Hangzhou soft soils. Pore structure distribution features and water contents of the soils were monitored during the experiments. The results were explained from the qualitative and quantitative perspectives. Clay particles were re-arranged into sheet-packed structure with plane-plane surfaces. The soil pore contracted, with resulted to decreasing of the void ratio, meanwhile the pores turned smoother in spatial forms and less complex in structure. Moreover, void ratios of the soil were computed through water content and the results were smaller than the measured values, which illustrated the electro-osmotic dewatering was larger than compression amount of soil. The fundamental cause goes to the fact that electro-osmosis derives from the migration of water dragged by ions and fails to generate compression of the soil skeleton directly. Electro-osmosis is recommended to be combined with surcharge and vacuum preloading in real practice.

Abstract:Under the condition of different cement content and curing time of NaCl, grease, Pb(NO₃)₂ pollution in Wenzhou soft soil cement solidification processing, the strength of the soil have been improved. In order to further obtain the treatment effect of different contaminated soil during cement solidification process, unconfined compressive strength tests and microstructure studies were conducted on different cement solidified contaminated soil. The effect of pollution type, pollution content, cement content, curing time on the cement solidified soil strength characteristics was analyzed. Furthermore, the difference of the microstructure of cement solidified soil with different pollutants concentration was also analyzed. The results show that within a certain range, the NaCl concentration promotes cement solidification of the early strength; grease content makes the cement solidification soil strength reduce obviously and compressibility increase; after Pb(NO₃)₂ was dropped into the soil, the strength of the cement solidification is reduced in general. A linear relationship appears between the strength and admixing amount. The cement solidification soil strength enhances with the increase of cement content and curing time. Scanning electron microscopy(SEM) results indicate that the increase of contaminate leads to the rise of porosity and loose structure of the solidified soils.

Abstract:In order to verify the applicability and reliability of longitudinal reinforcing steel grouted connecting in prefabricated components of shale ceramsite concrete, specimens were tested under monotonic tension test, high strength cyclic load test and large deformation cyclic load test. The influencing factors on connection performance including the strength of shale ceramsite concrete and lapping length of steel were analyzed. The test results indicate that no slippage occurs in all specimens' longitudinal steel, and the ultimate failure of all specimens are steel outside the splice broken up or yielding. It is suggested that the lapping length of grouted steel should not be less than 1.0l_aE. When the lapping length of steel is greater than or equal to 1.0l_aE, the ultimate tensile strength of splice will be increased with the higher strength of shale ceramsite concrete. The grouted connecting is suitable for the reliable connection of longitudinal reinforcing steel in prefabricated components of shale ceramsite concrete, when it satisfies certain structural requirements.

Abstract:In order to determine the compressibility characteristics of bio-enzyme expansive soil, by a series of one-dimensional consolidation tests, the effect of consolidation pressure on compressibility attributions of bio-enzyme-treated, lime-treated and cement-treated expansive soil is scrtutinized, and voids ratio, compression coefficient and unit settlement are gained. The influence of compression pressure on bio-enzyme -treated expansive soil, lime-treated expansive soil, and cement-treated expansive soil is discussed. Bio-enzyme -treated, lime-treated and cement-treated expansive soil possesses different compressibility, which is embodied by e-p curve and coefficient compressibility The compressibility of expansive soil is improved by adding bio-enzyme, lime and cement. When the mass ratio between enzyme and water is 1:300, compressibility is minimum. Linear equations can describe the relation between unit settlement and unit loads:s_i=bp^_ia.

Abstract:A low cyclic reversed loading test was carried out on seven cross-shaped columns with 600 MPa reinforcement. The hysteric curve, skeleton curve, longitudinal reinforcement strain curve and stirrup strain curve of the specimen under low cyclic reversed loading were obtained. The results show that the hysteric curve is full, the symmetry is good and the energy dissipation capacity is good. With the increase of the stirrup ratio, the peak load and the deformation capacity are enhanced. With the increase of the axial compression ratio, the ultimate bearing capacity increases, and the energy dissipation capacity raises while the stiffness degradation accelerate. The load capacity of the 600 MPa reinforced specimen is larger than that of the HRB500 reinforced specimen, and the plastic deformation capacity enhances while the energy dissipation capacity reduces. By using the ABAQUS software, the finite element analysis of the specimen was carried out. The simulation results were in good agreement with the experimental results.