Research On The Test Design And Evaluation Method Of The Safety Of The Existing Building Curtain Wall

As the outer protective structure of the building curtain wall,with th e increase of its service age,the curtain wall bearing the external load will cause safety problems such as panel breakage,loosening of the supporting boundary,reduction of natural frequency,aging of sealant and corrosion of connectors.Considering the particularity of the curtain wall itself,the existing curtain wall inspection procedures mostly focus on inspection and observation methods,which are subjectively affected by the inspectors,and the existing curtain wall safety inspection and evaluation lack practical engineering experience and a complete safety evaluation system.In view of this,it is particularly important to analyze and summarize the failure modes and safety hazards of curtain walls,optimize curtain wall design and test methods,and improve a set of simple,applicable and reliable existing curtain wall safety evaluation systems.This paper selects two different specifications of hidden frame curtain walls to carry out physical performance tests,analyzes the causes of the differences in physical properties of the two curtain walls,and provides suggestions for the design of curtain wall specifications in the project;studies the design theory of single-span and double-span structure of columns when designing for wind pressure,and calculates The bearing capacity and deformation of the curtain wall panels,beams and double-span columns under wind load;ANSYS software is used to establish a three-dimensional calculation model of the fully hidden frame curtain wall,and the static analysi s of the curtain wall glass panels,columns and beams is carried out,and the wind pressure resistance test is carried out.The results and theoretical analysis values are compared and analyzed;the vibration test is designed to dynamically change the four sides of the glass panel from tightness and looseness,the natural frequency value of the curtain wall under various constraints is measured,and the finite element software is used to simulate and verify the excitation test,and draw the curve to obtain The critical value of the natural frequency of the curtain wall is divided into safety zones for the preliminary evaluation of the safety of the curtain wall;through a large number of test simulations and data analysis,the safety evaluation index is desi gned,and a feasible curtain wall safety evaluation plan is proposed to study the safety of the envelope structure and formulate the safety of the existing curtain wall Sex identification standards provide a scientific basis.In this paper,through theoretical analysis,experimental research and software simulation,the design optimizes and perfects the existing curtain wall safety performance test method and evaluation plan.The main contents and results of the research are listed as follows:(1)Study the material properties of the curtain wall,detailed the on-site test methods of the curtain wall to ensure the operability and integrity of the curtain wall inspection;design the physical performance test of different specifications of the curtain wall,elaborate the test basis and design theory to ensure the smooth progress of the physical performance test of the curtain wall;And calculate the load and action effects of the curtain wall structure,and design the excitation test of the natural frequency change when the boundary constraint changes.(2)The physical performance test of two types of curtain walls with different specifications was carried out according to the specifications.The test found that the difference in air penetration between the inte gral part and the openable part of the two specimens under a pressure difference of ±50Pa was 6% and 3.5%,respectively.There are many glue joints and the openable part is not sufficiently sealed.To ensure the airtight performance of the curtain wall,it is recommended to adopt the two-plate design of the test piece;The openable and fixed parts of the two specimens were continuously sprayed with water for 900 s under the design pressure,and no serious leakage occurred.The surface of specimen one was weak.The sealant of specimen two of the curtain wall may be hardened and cracked.Piece one specification design;During the wind pressure test,the deflection value of the curtain wall increases linearly with the increase of the pressure difference.Due to the failure of the silicone rubber and the different panel sizes,the deflection has a little deviation.It is recommended that the larger wind pressure area adopts a curtain wall test piece design to ensure the curtain wall structure Safety.(3)Relying on the hidden frame curtain wall example,according to the local design wind pressure and site conditions,calculate the stress and deflection values of the curtain wall panels,beams and double-span columns under wind load to obtain the load-bearing capacity and deformation of the curtain wall;research and analyze the use of curtain wall columns The structural design theory of single-span beam and double-span beam model,the difference between the deflection value of the double-span column structure and the measured wind pressure is 23%,which is smaller than the single-span design difference,which proves the feasibility of the double-span design of the column;it is recommended that the curtain wall column is wind-resistant Adopting a double-span design in the design can greatly reduce the amount of aluminum alloy material,and truly simulate the on-site force state of the curtain wall to ensure that the structure meets the requirements of load-bearing safety.(4)Using ANSYS software to simulate the force state of the curtain wall under wind load based on the engineering test data,establish a three-dimensional finite element calculation model of the curtain wall specimen 1,and compare and analyze the theoretical value,finite element simulation value and actual measured value of the curtain wall The deviations appearing;the theoretical value of the panel and the numerical simulation have a negative deviation of about 30% and 20% respectively from the measured deflection of the wind resistance,indicating that the static analysis can simulate the reality of wind pressure,which can improve the efficiency of the dynamic analysis of the curtain wall structure;the column theory The calculated value and the simulated value are 31% different from the measured deflection value but the overall deflection differs by about 10%,indicating that the deformation of the curtain wall is an integral deformation including the deformation of the frame,structural glue and panel;the maximum deflection of the aluminum alloy column of the curtain wall appears in the middle of the column.The stress concentration effect of the actual structure further proves that the finite element numerical simulation results are true and reliable.(5)The TY19-GWVs system is used to conduct t he glass curtain wall vibration test,and the natural frequency attenuation law when the boundary constraint of the curtain wall is changed from strong to weak is obtained;the finite element software simulates and verifies the excitation test of the curta in wall,and the difference between the natural frequency value and the test result is less than 2.70%,which proves that finite element simulation can reduce errors and improve analysis efficiency;compare the natural frequency curves of the three types o f panels,it is recommended that the aspect ratio of the new curtain wall panel is designed to be close to 1 to reduce costs and avoid resonance;draw the natural frequency under ANSYS static and modal analysis Change curve,get the critical value of natur al frequency from the bearing capacity fg or deflection limit df.lim,use [critical value,upper limit] to evaluate the safety of the curtain wall;draw the relationship curve between the safety state of the curtain wall and the four-side support state and the natural frequency,According to the curve,the safety status of the curtain wall under each constraint condition can be accurately judged.(6)Through analyzing the failure modes of curtain wall materials,structure and function,studying the plan in detail in the design stage and strictly controlling deviations during construction;analyzing the causes of curtain wall safety problems,conducting experimental research and simulation verification for various problems,and passing the design of curtain w all safety Performance evaluation indicators,summed up and perfected a set of existing building curtain wall safety testing methods and evaluation programs.The applicability of the evaluation system is verified through examples of curtain wall safety tes ting,which provides a theoretical basis for the safety evaluation of the enclosure structure,and ensures that the results of the curtain wall safety research are complete and reliable.Formulate to provide scientific basis.