Experimental Analysis of Cracking Behavior of ConcreteBeams Reinforced with High Strength Bars

Eight concrete beams reinforced with 500MPa steel bars and four reinforced with 400MPa ultra fine grain steel bars were tested under two point symmetrical concentrated static loading to observe the details of crack pattern development on these beams and investigate their cracking characteristics. It was shown that the cracking behavior of the beams with high strength bars was essentially similar to that of common RC flexural members, whereas the computed crack widths using the formula adopted in the Code for Design of Concrete Structures GB 50010 2002 exceeded that of the experiment under the normal service. Furthermore, the formulas for crack spacing and crack width specified in GB 50010 2002 were evaluated through the experimental results and previous studies of sixty seven concrete beams reinforced with high strength bars. On the basis of the calculation model in GB 50010 2002, revised formulas for crack spacing and crack width were proposed. The values calculated by revised formulas were in good agreement with the test results.     

Seismic Assessment of RC Frame Structure Based on New Design Codes

The national structural codes GB50010-2002 and GB 50011-2001 have been modified in many aspects compared with the old ones. To verify the effectiveness of structural capacity design provisions in the new codes, firstly, two typical RC frame structures of Grade 2 in intensity-category 8 and Grade 1 in intensity-category 9 are designed according to the new codes. Then, nonlinear dynamic analyses of the two structures are carried out under excitations of several ground motions with the fortification and rare intensity levels. With the analysis results the availability of strong column weak beam is checked carefully, which is desirable with capacity design measures of RC frame in Chinese new structural design code. The conclusions drawn from the analysis are helpful to structural design and local modification of the codes.     

Experimental Analysis on Bending Capacity of Unbonded Prestressed Concrete Beams with HRBF500 Steel Bars

The bending capacity tests on ten simple supported beams were conducted to investigate the damage characteristics, prestress increment, beading capacity and displacement ductility of unbounded prestressed concrete beams with HRBF500 steel bars. The results show that the HRBF500 steel bars has yielded before the limit state. The concrete in compression zone crushes upon the broken of the beams, which shows a sudden damage mode. The measured ultimate stress increments of unbounded tendons are in linear relationship with the comprehensive reinforcement ratio index, while the values of the ultimate stress increments are obviously higher than those values specified in the code GB50010-2010, and the average ratio of predicted values to testing values is about 0.35. The mid span deflection upon yielding of the beams is large, while the displacement ductility is bad and the average value of the displacement ductility ratio is 1.67. The displacement ductility ratio decreases with the increases of the comprehensive reinforcement ratio index. Based on the experimental results, the proposed calculation formula of ultimate stress increments of unbounded tendons was established, and it is in good agreement with the experimental results when the testing value is less than 450 MPa.     

Current Situation and Prospects of Atrium Smoke Management Research

This paper surveys the current situation of atrium smoke management research at home and abroad. Recent research such as the types and configurations of atrium buildings, atrium smoke management system, smoke exhaust system modes and smoke exhaust effectiveness, atrium smoke filling process and its time constant, pre_stratification and detection, air flow for smoke control between the atrium and adjoining space, sprinkler effect are discussed. Regulations of atrium design and some problems in current national code (Code for Fire Protection Design of Tall Buildings GB50045-95) are also discussed and areas of further research are specified.     

600 MPa高强钢筋与混凝土的粘结锚固性能试验研究

为研究600 MPa高强钢筋与混凝土粘结锚固性能,设计了72个棱柱体试件进行拉拔试验,对600 MPa高强钢筋粘结锚固的破坏形态及粘结应力分布进行分析,通过建立基本粘结滑移关系及位置函数,确定600 MPa高强钢筋在混凝土结构中的粘结滑移本构关系。采用一次二阶矩法进行可靠度分析,提出锚固长度设计建议。研究表明：600 MPa高强钢筋粘结锚固的破坏形态及粘结应力分布与普通钢筋类似且粘结锚固性能良好,《混凝土结构设计规范》（GB 50010—2010）基本锚固长度计算公式依然适用于600 MPa高强钢筋。     

Test Study on the Synthetic Control of Shrinkage Cracking on the Base of Cement Stabilized Crushed Rock

To optimize properties of the crushed rock is a simple and effective method to control the reflective cracking.There are some measures to reduce the shrinkage of the crushed rock,such as: decreasing water content and cement percentage,reducing surface tension of water.The test study shows that shrinkage resistance of the crushed rock base can be improved by mixing with fly ash,water reducing agent and shrinkage reducing agent each other,it will be better for the crushed rock to mix with fly ash,water reducing agent and shrinkage reducing agent proportionally.     

RATIONAL DETERMINATION OF TNE BEAM AND COLUMN CROSS-SECTIONAL SIZES OF THE FRAME STRUCTURE IN A EARTHQUAKE ZONE

At the preliminary design stage of a building, it is neccssary to determine thebeam and column cross-sectional sizes of frame strtictures.According to some provisions of the"Building Aseismatic Design Code"(GBJ 11-89),main factors having influence on the beam andcolumn cross-sectional sizes are analyzed.and calculating formulas for the determination of the beam and column cross-sectional sizes which are satisfied the restrained condition of horizontal dis-placement of a building are derived in this paper.     

Influence of fine aggregate on initial shrinkage of high performance concrete

The type and percentage of sand affect the gradation of coarse fine aggregate and the amount of spare mortar in concrete, which further affects the resistance of fresh concrete to initial plastic shrinkage. Taking into account the engineering characteristics of sand in the area of Chongqing, P. R. China, three fine aggregates composed of superfine, medium, mixed and manufactured sand, are used to prepare high performance concrete (HPC). The effects of these three fine aggregates on initial plastic shrinkage crack are investigated. The results show that the HPC prepared with superfine sand possesses a higher initial shrinkage value than HPC prepared with mixed or medium sand. An optimal sand percentage is necessary to reduce the initial shrinkage cracking of HPC prepared with mixed or medium sand.     

Experimental Research on Seismic Shear Capacity of I-Shape Ductile Reinforced Concrete Structural Walls

The shear design formula for seismic shearwalls in the Chinese standard (Code for Design of Concrete Structures) have not been verified by tests yet, In order to compensate for it, the authors undertake the task of testing on the shear behavior of seismic shearwalls organized by the Code association. After discussing on the particular conditions controlling tests and philosophy in specimen designing, the results of the first group of tests on the seismic shear behavior of shearwalls, which are I-shaped and with relatively large scale and axial force ratio of 0.2 and tested under reversed cyclic horizontal forces, are introduced. The results are analyzed and discussed.     

《农村土地承包经营权要素编码规则》国家标准解读

农村土地承包经营权要素编码是开展农村土地承包管理的基础性工作。《农村土地承包经营权要素编码规则》(GB/T 35958-2018)于2018年9月1日开始实施,必将对规范农村土地承包经营权确权登记颁证工作和促进土地承包管理信息化建设发挥极其重要的作用。为便于国家标准GB/T 35958-2018使用者理解和执行,本文对标准的主要内容进行分析和解读。介绍了GB/T 35958-2018的编制背景,分析了标准的内容要素和层次结构,剖析了标准中农村土地承包经营权要素的代码结构、编码方法和赋码规则,揭示了GB/T 35958-2018与国内相关标准的关系,特别是与NY/T 2538-2014的内在关联性,指出了GB/T 35958-2018在应用过程中需要注意的若干问题,并就及时宣贯和修订国家标准提出了建议。研究可望深化对农村土地承包经营权要素编码的认识,促进GB/T 35958-2018在农村土地承包经营权确权登记颁证工作中的有效实施和规范应用。     

Behavior and Design of High-strength Bolt in Tensile Connection

The tensile strength of high strength bolt is affected by many factors, including prying force. The prying force can result in the increment of bolt force, for which the connection failed ahead of time. Several methods are presented for calculating the prying force. In the China's "Code for Design of Steel Structure" (GB50017), there is no formula for calculation of prying force and a factor of 0.8 is considered in formula for tensile strength of bolt for taking the prying force into account. It is proposed that the design value of tensile resistance for high strength bolt should be increased.     

Investigation on Shear Strength of Reinforced Concrete Beams without Web Reinforcement

On the basis of available testing data of simply supported reinforced concrete beams without web reinforcement under two-point concentrated loads,the dominant factors contributing to shear performance are identified,and the basic laws are correspondingly quantitatively described.The shear design equations of China Design Code of Reinforced Concrete Structures,ACI Code,together with two other expressions of shear of RC beams without web reinforcement,are thus calibrated to identify their accuracy in describing the shear mechanism of such members.     

Technology for Synthesis of Polymeric Aluminum Chloride Utilize Waste Alfoil

The technology for synthesis of polymeric aluminum chloride (PAC)utilizing waste alfoil is presented, the factors affecting the property of PAC such as the ratio of alfoil to hydrochloric acid to water, the reaction temperature, ripening time and the sequence of feed in raw materials are discussed, and the technology conditions of prepare PAC are determined. The technological process is simple, and the product qualities accord with the demands of GB15892-95.     

高性能混凝土板式构件的早期收缩特性及预测模型

以桥面板等高性能混凝土板式构件为研究对象,通过实验测试了板式构件不同截面厚度位置处早期收缩分布情况,探讨混凝土早期收缩变形与温度、湿度发展过程。结果表明,混凝土板式构件的内部厚度方向不同位置处的相对湿度随龄期都呈现逐渐减小趋势,并呈现两阶段特征,同时,混凝土板式构件早期收缩变形厚度方向不同步,导致板式构件表面产生拉应力,当拉应力大于当时混凝土的抗拉强度时,混凝土表面就会出现浅层裂缝,这与实际工程中发现的板式构件表面开裂情况相吻合。混凝土板式构件早期收缩变形与相同配合比混凝土的早期自由收缩变形进行比较,引入相对约束度并建立了混凝土板式构件早期收缩变形的预测模型,并验证了该模型的准确性,其特点是能预测高性能混凝土板式构件不同截面厚度位置的早期收缩变形,对控制混凝土桥梁板式结构的早期收缩裂缝具有实际意义。     

Effect of Varying Longitudinal Reinforcement Ratios on Shear Behavior of Reinforced Concrete Beams Without Web Reinforcement

Effect of varying longitudinal reinforcement ratios on shear behavior of reinforced concrete simply supported beams without web reinforcement was analyzed in this paper, with emphasis on both shear ultimate capacity and failure mode, on the basis of available testing data. Generic laws were thus obtained and codified methods, including ACI Code and China Design Code of Reinforced Concrete Structures, were evaluated as a result.     

Uncertainty Analysis of Long-term Deformation for Prestressed Concrete Beam

Owing to the randomness of shrinkage and creep of concrete, random analysis method should be adopted to give a reasonable result with probabilistic guarantee. Stochastic variables for long-term analysis with GL2000 model about creep and shrinkage of concrete were presented. Combining Monte Carlo sampling with the response surface method, the stochastic analysis model was performed which is on time-variant deflection of prestressed concrete bridge. The long-term deflection of a prestressed concrete bridge was analyzed by this model. Sensitivity analysis and parametric study were carried out. And the uncertainty of creep model, elastic modulus of concrete, magnitude of sustained load, and prestress forces are the most important factors for long-term deflection. Furthermore, controlling accuracy of prestress forces and delaying the loading time are helpful to inhibit long-term deflection.     

粉煤灰对高强混凝土收缩徐变的影响试验研究及其修正模型

粉煤灰对高强混凝土收缩徐变的影响直接关系到结构长期性能的合理确定。制作粉煤灰掺量分别为0、12%和24%的100 mm×100 mm×400 mm的C50混凝土棱柱体试件,在试验室条件下进行收缩及不同加载龄期的徐变试验,研究了粉煤灰对高强混凝土收缩徐变的影响。根据试验结果评估了目前常用的4种相关规范公式对高强混凝土收缩徐变的适用性,并引入粉煤灰影响系数以综合反映粉煤灰掺量和加载龄期对高强混凝土收缩徐变的影响,根据试验结果和现有研究成果提出了其修正模型。分析结果表明,JTG D 62和GL 2000推荐的收缩徐变预测模式与基准试件实测结果较为吻合,验证结论亦说明所引入的粉煤灰影响系数可应用于掺粉煤灰高强混凝土的收缩徐变预测。     

Experimental Study on the Extended Length of Negative Reinforcement Cut-in Phases in Continuous Beams

In this paper through the static loading tests of 6 inflexion zones and 2 cantilever zones in full-size constrained R/C beams, the stress performance in rebars cut-in-phases and subjected to negative moment is studied. The stress properties of extended length of rebars with different shear-span ratiosare analysed on basis of the full measurement of strain distributions combined with the investigation on state and regularity of the diagonal cracks development and series of new knowledge are obtained. It is found that current Concrete Design Code provisions on the extended length are inadequate for the high shear-span ratio and superfluous for the low shear-span ratio. The theoretical and experimental foundations are provided for determining proper value of extended length for rebars cut-in-phases.     

Analytical Method on Bi-directional Shearing Capacity of RC Framed Columns

The current analytical method on bi-directional shearing capacity of RC framed columns, the so called "over strength factor method", in the drafting "Design Code of RC structures", is carefully investigated. Limits of this method are presented and suggestions are put forward to modify it. On this basis, the simplified tri linear analytical method to determine bi directional shearing capacity is presented afterwards and the error of this method is given. Finally, the cases of design and check of the two methods are illustrated.     

升流式厌氧生物滤池与温室型人工湿地组合对农村生活污水处理的研究

针对中国农村分布分散、资金短缺,缺乏污水处理专业人员,而农村污水处理又是亟待解决的环境问题这一现状,笔者研究升流式厌氧生物滤池（UAF）与温室型人工湿地组合工艺低气温下处理农村生活污水的运行特点及效果。结果表明：UAF的最佳水力停留时间（HRT）为12 h,容积负荷0.632~0.936 kg/(m3?d),COD的平均去除率为56%,室外气温在-5~10℃（冬春）,温室型人工湿地的最佳HRT为3天,组合工艺COD总去除率平均为75%,BOD5总去除率平均达到84%,SS总去除率平均不低于93%,氨氮总去除率平均为63%,TP总去除率平均为46%,出水水质除TP外均满足GB 18918-2002《城镇污水处理厂污染物排放标准》1级B标准。该工艺具有低能耗、低投资、低运行费用、运行维护简单等优点,适合作为农村生活污水的处理工艺推广使用。