Study On Comparison And Selection Of Seismic Strengthening Schemes For Concrete Frame Structures

In recent years,China has proposed the twin carbon targets of "carbon peaking" and "carbon neutrality",and in this context,the concept of urban regeneration has been further developed.Urban regeneration refers to the shift from large-scale incremental construction in the past to a combination of stock upgrading and incremental structural adjustment,i.e.the reinforcement and renovation of existing buildings has become a priority in urban regeneration.As most cities in China are located in seismic zones,the strengthening and renovation of existing buildings is always closely linked to seismic strengthening.Among them,determining the optimal seismic strengthening solution is the key issue in the strengthening and renovation of existing buildings.Traditional seismic strengthening schemes rely on the subjective judgement of designers or simple comparisons of economic indicators,which are not scientific and comprehensive enough.In order to select the reinforcement scheme with the best overall benefit in a scientific and reasonable manner,this thesis proposes a quantitative multi-point comparison method for the seismic strengthening scheme of concrete frame structures.The main research contents and conclusions of this thesis are as follows:(1)For concrete frame structures,a multi-indicator quantitative selection method for seismic strengthening solutions is proposed,taking into account safety,economic and technical indicators.(1)A multi-indicator quantitative selection method is proposed for concrete frame structures.The quantitative selection method consists of the following: 1)Determine the evaluation indicators for the seismic strengthening solution,and divide the evaluation indicators into two categories: one is the necessary indicators,mainly referring to structural safety indicators;the other is the optional indicators,and the recommended optional evaluation indicators are construction convenience,economy,building suitability and energy saving and environmental protection.The optional indicators can also be increased or decreased on this basis.2)Evaluate the necessary indicators-structural safety indicators-for each alternative strengthening solution;3)Quantitative analysis of the optional indicators for each alternative strengthening solution;4)Determine the optimal seismic strengthening solution.(2)Propose an evaluation method for the necessary indicators-structural safety indicators.This includes the evaluation of structural safety sub-indicators,the evaluation criteria for structural safety and the calculation methods for structural safety.1)Determine the sub-indicators for the evaluation of structural safety indicators from two aspects: structural components and the overall structure.In the case of structural members,the reinforcement,axial compression ratio,plastic angle of beam ends and crack width are selected as sub-indicators;in the case of the overall structure,the period ratio,stiffness ratio,displacement ratio,ratio of shear bearing capacity,stiffness-to-weight ratio,shear-to-weight ratio and maximum inter-storey displacement angle are selected as sub-indicators.2)The evaluation criteria for each evaluation sub-indicator are determined according to the limit value requirements stipulated in the current national standards and codes.3)The calculation formulae given in the current national standard "Code for the Design of Reinforced Concrete Structures"(GB50367-2013)were used to calculate the reinforced structures,in which the strength utilisation factor was introduced for each reinforcement method to discount its strength,taking into account the synergistic working of the old and new members.The PKPM Identification and Reinforcement Module was used as an auxiliary tool for the calculation of structural safety.(3)Quantitative analysis of optional indicators for concrete frame structures,including the quantitative calculation of optional indicators,scoring of optional indicators,weighting of optional indicators and determination of the total score.1)Quantify the optional indicators of ease of construction,economy,building suitability and energy conservation and environmental protection into cost,man-days,loss of building space and carbon emission respectively,and give the corresponding calculation formulae for each indicator quantification;2)If the reinforcement solution with the best value(maximum or minimum)for an indicator is 100 points,then the score for the rest of the reinforcement solutions is the ratio of the quantified value for that indicator to the best value multiplied by 100,i.e.the quantified value for each indicator is dimensionless;3)The recommended weights for ease of construction: economy: architectural suitability: energy conservation and environmental protection are: 0.2:0.4:0.2:0.2;if there are special circumstances,the designer may make adjustments on this basis;4)Using the multi-indicator weighted summation method to obtain the total score,the total score is ranked in order of magnitude,and the one with the highest total score is determined to be the optimal seismic strengthening solution.(4)Using the multi-indicator quantitative selection method proposed in this thesis to determine the optimal seismic strengthening solution for the ward building of Suqian City Infectious Disease Hospital.The optimal seismic strengthening solution was determined to be a combination of the seismic reduction method and the component strengthening method.(5)To determine the optimal seismic strengthening solution for the standard frame structure model under two damage scenarios using the quantitative multi-indicator selection method for seismic strengthening solutions,and to study the influence of different damage characteristics on the optimal seismic strengthening solution.1)For an ordinary multi-storey building,when both the structural elements and the overall structure are severely damaged and deficient,a combination of the new shear wall method and the member strengthening method is the optimal seismic strengthening solution;2)When only some of the structural elements have insufficient load bearing capacity but the overall structure is not too damaged and affected,the member reinforcement method is the best choice.