Research On The Influence Of New Codes On Reinforcement In Reinforced Concrete Structure

In the revision process of codes2010version, in order to examine the applicability of the amendments, specification group originated several units to execute some structural test design according with procedures of manuscript, analyze the reasons of the change in the analytical results of calculation and the reinforcement, and put forward opinions and suggestions. By the formally promulgation and implementation of codes for structure design such as Code for seismic design of buildings(GB50011-2010), Code for design of concrete structures(GB50010-2010) and Technical specification for concrete structure of tall building(JGJ3-2010), researching the influence of new codes on reinforcement in reinforced concrete structure has high application value and engineering significance. This paper briefly introduces the main revised points of the2010codes in the design of concrete structures, conductes analysis on the common type of concrete structure instance and quantitative analysis in the amount of reinforcement. Some design recommendations and problems which should be noted in design are given. The major researches are as follows:1) The developing history of concrete structure design code is sorted out. Main revised topics in2010codes are pointed out and the development in the field of building structures CAD analysis software is reviewed in China since the1970s.2) Combined with major code amendments to slabs, beams, columns, walls, including the reinforcement of different cross-thick slabs, minimum ratio of reinforcement for slab, calculation of shear capability, checking of serviceability limit states, adjusting the column internal forces,the axial compression ratio and minimum ratio of reinforcement for concrete columns, strength design and detailing of wall, and so on.Through the qualitative and quantitative analysis of clause and case comparison, In this paper the differences of the component design and the amount of reinforcement between the old codes and the new are given. The corresponding data charts are presented. The general variation of the number of components reinforced is given. The existing main problems of "strong column weak beam" are pointed out.And the appropriate design recommendations are given.3) Combined with foreign codes, a more in-depth comparative analysis was conducted on the second order effect between the old codes and the new. Considering the difference of the structure lateral displacement for calculating the P-δ effect, an improved method to calculate the P-δ effect is proposed.4) In order to study the application of high strength steel reinforcement, many engineering examples of concrete structure are designed using different reinforced grades. The general changing patterns of steel consumption in slabs, beams, columns, walls are given.5) A method of different structural analysis program model data transformation is established through the intermediate structure of the generic model data description. Using this method, an interface program is developed to convert PKPM structure model to the ETABS e2k input file.Through several engineering examples’ comparison,including structural mass, the vertical reaction force, structural displacement,seismic action and components’internal force and reinforcement, the correctness and feasibility of the model transformation method and model conversion are verified.6) Several structural analysis software are used for the structural calculation and analysis of ten engineering examples,including the frame structure, bent structure, shearwall structure, the frame shearwall structure and frame-corewall structure. The comparison shows that the indicators of the mechanical properties by the different procedures are basically identical. The differences of steel consumption based on different schemes are given.The main factors coursing the numerical differences are analyzed. The conclusions of engineering reinforcement changes are as follows: Every project is different due to the structural types, functionality, load, materials, and seismic design grade of structural members and so on, so the change range of steel consumption is different. If reinforced materials are same,according to the comparison between the old codes and the new, a slight fluctuation appears about the change range of steel consumption. The steel consumption of slabs is decreased slightly.The reduce range is basically less than2.5%. When using HRB400, the reduction of slabs will be more.The longitudinal reinforcement of most of beams is reduced slightly. The increasing range of beam transverse reinforcement is about5.0%.The steel consumption of column longitudinal reinforcement is increased significantly.But the increasing range of different structural types is different significantly. In general case, the increasing range of frame structure is between10.0%to15.0%and the increasing range of the other structural types is less than8.0%. The range of wall steel consumption changes generally in10.0%. To replace the low-strength reinforcement with high-strength reinforcement, the steel consumption is reduced significantly. In general case,the steel consumption of shearwall structure is decreased about5.0%and it is decreased more than10.0%in other structural types.In summary, the paper focuses on the influence of2010codes on reinforcement in reinforced concrete structure.Though the comparison of the qualitative analysis with provisions and quantitative analysis with engineering examples, the differences of the reinforcement between the old codes and the new are given by chart.The general changing patterns of the application of high-strength reinforcement are drawn. The main factors coursing such differences are analyzed.These can be the technical reference for designers and technologists.