Study on Effect of Longitudinal Reinforcement Ratio on Shear Behavior of Restrained Beams with Web Reinforcement

In this paper, five restrained beams with web and different longitudinal reinforcement ratio as well as above longitudinal reinforcement truncated were tested under static point loads. On this basis, the overall process of cracking development under shear and the effect of longitudinal reinforcement ratio on shear strength was investigated     

Test Study on the Small Span-to Depth Ratio Seismic Coupling Beams with Low Reinforcement Rate by New Reinforcement Scheme

Coupling beams are the key elements of plastic energy dissipation mechanisms in coupled walls.However,the design of the small span-to-depth ratio coupling beams with high ductility is still one of the problems not solved effectively in domestic and foreign seismic reinforced concrete structure design.The research group,where the authors of this paper are,brings forward a new reinforcement scheme with adding diagonal and rhombic bars to traditional reinforcement in the foundation.Test results prove that it is an effective way to solve the problems for it has good seismic performance and is easy to be constructed.This paper puts great emphasis on introducing the trial results and principal rules that are deduced from the test results of second set of specimens with low reinforcement rate.     

A Macro Model of Seismic Coupling Beams with Small Aspect Ratio Adopting New Reinforcement Arrangement Scheme

A new reinforcement arrangement scheme was suggested to provide satisfactory seismic performance and good workmanship for the coupling beams with small aspect ratio. Coupling beams with small aspect ratio are counter flexural deep beams with both ends restrained, in which the Bernoulli hypothesis are not valid. Although their load bearing capacity can be predicted with the strut-and-tie model developed recently, how to simulate this kind of beams adopting new reinforcement arrangement is still a problem. A macroscopic strut-and-tie model is thus presented for these coupling beams. Good agreement with experimental results is achieved.     

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.     

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.     

Calibration of Seismic Provisions for RC Frame in Different Earthquake-Intensity Regions in China

With examples of three 6-storey RC frames by using an elasto-plastic dynamic analysis program PL-AFJD of plane frame, developed by the second author of this paper, the frames designed for different earthquake-intensity regions (intensity category 7, 8, 9 respectively) are analyzed nonlinearly under four ground motions at the action of rare earthquake. Three frames strictly conform to the National Standard GBJ10-89 and the dimensions of columns are changed once along the height. The structure designed on intensity category 7 shows a relatively small response, which could be sustained by the structure. Though the hinge formation in columns can not be prevented, the inelastic deformation of columns is not serious, the structure at intensity category 9 exhibits a relative strong response, but the deformation of most columns is within the capacity and the trend to form a soft-storey does not appear. It is the structure at intensity category 8 that shows a severe response. Though the visible soft-storey can not be found, the deformation of some columns is beyond the capacity of inelastic hysteretic deformation under certain inputs, which indicate the possibility of local collapse.The elementary analysis results demonstrate the different effectiveness of seismic provisions for three different earthquake-intensity regions, which may be a reference to the amendment of National Design Standard.     

Experimental Research on the Seismic Behavior of the Interior Joint with High Shear - Compression Ratios in the Frame

The reversed cyclic loading tests of 5 nearly full-scale beam-column assembly specimens with high shear-compression ratio under different axial loads in reinforced concrete plane frames have been completed,which cover the shortage in the field of high shear-compression parameter among seismic joint experiments in the world.Based on relatively complete measuring and analyses of the law for the bond and slip of the beam bar through the joint,the stress of the level stirrup legs and hysteretic dissipated energy and the change of rigidity,the characteristic of shear transfer mechanisms and damage development and comprehensive seismic behavior of the assembly are proposed in this paper.It makes it possible to improve design codes and to establish relatively reasonable analytic modes and hysteretic modes in inelastic dynamic response analyses of the frame.     

配置500 MPa纵筋钢筋混凝土框架顶层端节点抗震性能试验研究

按照《混凝土结构设计规范》(GB 50010—2010)设计了6个配置500 MPa纵筋的钢筋混凝土框架顶层端节点,并进行了低周反复加载抗震性能试验,验证了规范规定的抗震措施对配置500 MPa钢筋的顶层端节点的有效性,分析了配置500 MPa级钢筋的顶层端节点的受力特点、节点区的破坏形态以及节点的综合抗震性能,并与受力条件基本相同的配置HRB335级纵筋节点的受力性能进行了对比,对采用不同延性指标评价配置不同强度钢筋节点的延性性能差异进行了讨论。     

Research on Seismic Behavior of Frame with T shaped SRC Columns

Referring to the criterion of seismic fortification intensity 8 specified by national seismic design code, a /2 scaled model of single span and two story frame composed of RC beams and T shaped steel reinforced concrete (SRC) columns has been made. A seismic evaluation was performed by the quasi static testing, including failure pattern, stiffness degradation, ductility and energy dissipation. The experimental results show that the frame has good seismic behavior, and section steel in the columns plays an important role in earthquake resistance. On the basis of experimental study and analysis, it concludes that the seismic behavior of frame with SRC special shaped columns can satisfy the requirements of seismic fortification.      

Experimental Study on, Small Span to Depth Ratio Coupling Beams withNew Reinforcement mewt Scheme and Design Method

Coupling beams combining two coupled walls are the primarily energy dissipating elements in the coupled walls and play a key role in improving ductility. It is proved by the test outcome at home and abroad that the shear failure happening early cannot be     

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.     

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.     

Inelastic Seismic Response of Reinforced Concrete Frame Structures Reinforced with HRB500 Steel Bars

To achieve sustainable development of construction industry, the application of HRB500 reinforcement with high strength and high ductility in RC structures is being promoted in civil and structural engineering in China. But few studies focus on seismic behaviors of RC structures reinforced with HRB500 bars. In this analysis, three RC frame structures on the Zone of Fortification Intensity 8 (0.3g) in China reinforced with HRB500, HRB400 and HRB335 bars respectively, are designed confirming to the latest draft of the revising Code for the Design of Concrete Structures. Then inelastic seismic response analyses of the three frames with multiple inputs of ground motions are conducted. The seismic response rules and seismic performances of the RC frame reinforced with HRB500 bars are compared with those frames reinforced with HRB400 and HRB335 bars. The analytical results indicate that under ground motions in rare earthquake level, the maximum displacements of the frame reinforced with HRB500 bars are roughly the same as those of the frames reinforced with HRB400 and HRB335 bars, while the rotation ductility demand of elements in the former structure is smaller than those of elements in the latter structures. It is also found that the frame reinforced with HRB500 bars develops a plastic energy dissipation mechanism that is dominated by beam hinges under major earthquake, and the maximum inter storey drift of the frame can satisfy the requirement in the Code for the RC Frame Structures.     

HDPF加固钢筋混凝土柱抗震性能试验研究

为了研究高延性聚酯纤维加固钢筋混凝土柱的抗震性能,共进行了7根柱的低周反复试验,其中,3根在未加固状态下进行试验,4根柱粘贴高延性聚酯纤维加固后进行试验,针对位移延性系数、等效粘滞阻尼系数、总耗能、承载力和纤维带的应变进行了研究与分析。研究结果表明：未加固柱的承载力、耗能能力和延性都比较低,采用高延性聚酯纤维加固后的试件裂缝发展缓慢,加固后柱的承载能力、耗能能力、延性均有不同程度地提高;在塑性铰区域内增加局部配筋,能够提高纤维布的约束效果。     

Strut-and-tie Model for Reinforced Concrete Corbels and Reinforcement Design

In American code for design of Concrete Structures (ACI 318-08), the strut-and-tie model method was used as a normative appendix for D-region design of reinforced concrete members. The constituent of the strut-and-tie model was introduced. Calculation of internal forces in struts, ties and node zone were proposed according to the design parameters (loading, concrete strength, steel strength) of the current Chinese code (GB 50010-2010).Then the design procedure was provided. Strut-and-tie model design method for reinforced concrete corbels was proposed following Chinese code parameters which degree of safety was compared with in ACI 318-08 through an example. The compared result shows that the proposed method can be used for the design of reinforced concrete corbels with clearer mechanical concepts and easier calculations.     

Test on Seismic Behaviors of Reinforced Concrete Beams Composite Rehabilitation with Bonded Carbon Fiber Reinforced Polymer and Steel Plate

Neither the Carbon Fiber Reinforced Plastic nor the steel plate strengthening concrete components shows sufficiency in improving the structures' seismic behaviors independently, while they complement each other by the way of composite strengthening. Six reinforced concrete beams, five of which are strengthened, were comparatively and experimentally tested under low frequency cyclic load to investigate their mechanical performances such as characteristic of resilience, hysteretic curve, seismic behaviors, skeleton curve, degeneration of rigidity and loading capacity. It is indicated that the way of composite strengthening can boost the beams′ ultimate bearing capacity, ductility and deformability capacity effectively, and it can delay rigidity degeneration and improve the seismic behaviors of the beams. Also, the CFRP and steel plate can work together very well.     

Deformation Capacity and Amount of Confining Reinforcement in Potential Plastic Hinge Regions of Rectangular Hollow Bridge Piers

Quasi static test results of 71 rectangular hollow bridge piers were collected to study the deformation capacity and amount of confining reinforcement in the potential plastic hinge region of the bridge piers. The deformation capacity of the hollow bridge piers with different failure modes were analyzed, and current codes provisions for the amount of confining reinforcement in hollow bridge piers were evaluated. Then, main factors influencing the deformation capacity of the piers were discussed based on multiple linear regression analysis and correlation analysis. At last, design equations based on Caltrans code of required confining reinforcement for rectangular hollow bridge piers were proposed. It is found that both the Caltrans and ACI codes show great reliability for the flexural failure mode and deformation capacity of the hollow bridge piers while the Chinese JTG/T B02-01-2008 code is unsafe. Also, the deformation capacity of the hollow bridge piers increases with the increase of the transverse reinforcement, longitudinal reinforcement, and web width, and decreases with the increase of the axial load ratio.