CN110189044A - Bearing capacity detection method after a kind of Mid and minor spans prestressed concrete beam bridge excessive fire - Google Patents
Bearing capacity detection method after a kind of Mid and minor spans prestressed concrete beam bridge excessive fire Download PDFInfo
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Abstract
The invention belongs to Bridge Inspection field, bearing capacity detection method after specially a kind of Mid and minor spans prestressed concrete beam bridge excessive fire, detailed process is as follows: dividing detection zone and simultaneously numbers；Obtaining each survey area includes that concrete color, rebound value, hammering reaction, fire crack, concrete fall off the measured values of area and depth 5 class evaluation indexes totally；It identifies that grading meter calculates the damage scale of the 5 class evaluation index according to area's impairment scale is surveyed, takes Synthetic Scale D of the peak as the survey areai；Calculate each survey area weights omegai；Take excessive fire complex damage scale Z of the weighted average of all survey areas Synthetic Scale of every beam as the beam；Bearing capacity reduces percentage after determining excessive fire according to the section where Z.The present invention avoids finite element method complicated after over-firing, fast quantification obtains structural limits bearing capacity reduced rate, it is easy to implement, feasibility is high, result credibility is big, to obtain Residual Loading Capacity, reappraise whether structure needs repairing and reinforcement to put back into, or provide reference to remove to rebuild.
Description
Technical field
The invention belongs to Bridge Inspection fields, especially armored concrete damage detection technology field, specially one
Bearing capacity detection method after kind Mid and minor spans prestressed concrete beam bridge excessive fire.
Background technique
Highway is the lifeblood of Regional Economic Development, and bridge crosses over the important connection in rivers valley as highway
Line plays great function in shortening communication distance.Due to Freeway Traffic Volume and petroleum resources freight volume
It increases sharply, the frequency that traffic accident causes fire is higher and higher, brings to bridge structure safe and greatly endangers.As current application
Most commonly used building structural materials --- armored concrete will occur a series of physical chemistry and become when by fire effect
Change.With the extension of bridge fire duration, the yield stress of reinforcing bar and concrete is constantly reduced, ultimately cause Spallation of Concrete,
Reinforcing bar fusing, seriously destroys the stress performance and anti-bending bearing capacity of bridge, it could even be possible to structural failure is caused to be sent out when serious
Life is collapsed.To reduce economic loss caused by bridge fire, guarantees the safety of people and resume traffic as early as possible, need root
According to field investigation data rapidly to impaired bridge carry out bending bearing capacity assessment (according to correlative study, beams of concrete after excessive fire
Based on bridge is mainly destroyed with bending bearing capacity), to determine the processing scheme after bridge fire as early as possible.
Oneself bridge for building up of China, Short/Medium Span Bridge occupy larger specific gravity, and such bridge is mainly prestressed concrete
Native beam bridge rationally assesses the degree of injury of prestressed reinforced concrete structure after fire, not for reinforced concrete structural element
With degree of injury make reasonable damage diagnosis, be of great practical significance and economic significance.Based on the strength of materials
Transformation rule at high temperature, analyzes ordinary reinforced concrete bridge after by fire, concrete progressive damage depth and surplus
Remaining bearing capacity rapidly assesses load carrying capacity of bridge with the variation course of fire duration, has engineering significance.
Damage Assessment Method and monitoring technology can detect the presence of structural damage, position, and predict the structure residual longevity
Life, while also providing fundamental basis for the lesion assessment of fire later period structure and reinforcing countermeasure.The common experience estimation technique both at home and abroad
The damage check of Concrete after Fire beam is carried out with cross-validation method.For example, CN201710216585.4 is related to Coupled Numerical mould
The Concrete after Fire bridge security status assessment method of quasi- technology, traditional detection method and numerical simulation analysis are combined,
Propose the detection of Concrete after Fire beam bridge and appraisal procedure.CN201580068902.1 is provided for predicting that fire is damaged coagulation
The system and method for the remaining service life of soil structure, by comparing the number in sample XRD data and standardized data library (DB)
According to the remaining service life for carrying out quick predict fire damage concrete structure.It is mixed that CN201710383220.0 discloses a kind of fire
The method for electrochemically determining of solidifying soil reinforcing bar damage, establishes the electrochemically determining criterion of Fire simulated furnace reinforcing bar damage, then transports
Diagnostic assessment has been carried out to practical Fire simulated furnace structure with above-mentioned criterion and assistant analysis model.CN201811430868.X and
CN201711000789.0 is related separately to based on the reinforced concrete simple-supported beam fire damage for improving support vector machines and vibration measurement
Hurt recognition methods, greatly reduces the quantity of training sample when damage is accurately positioned, significantly improve diagnosis efficiency, recognition result
Reliability it is higher.Many researchers also use Ultrasonic Nondestructive method, infrared thermal imaging detection method, checking spring range method,
Ultrasonic-rebound method carries out Fast nondestructive evaluation identification, as CN201811058971.6 is disclosed based on ultrasonic infrared multiple
Close the quick check and evaluation identification method of concrete structure Fire-damaged of detection technique.
Existing method, which mainly passes through the huge finite element method of calculation amount just, can obtain more accurately as a result, due to pre-
The different geometric cross section type of prestressed concrete component and fire exposure, and material property and mechanical property right and wrong in section
Uniformly, it after this makes every bridge excessive fire, after being both needed to on-site test, models again, cannot quickly obtain the degree of injury of bridge
And Residual Loading Capacity, there are the secondary danger collapsed, and carrying out the disaster relief to rescue personnel makes troubles.And existing detection side
Method lacks quantitative assessment for prestressed reinforced concrete construction ultimate bearing capacity after excessive fire, and ultimate bearing capacity this important finger
It marks, is the important evidence for reappraising whether bridge needs repairing and reinforcement to put back into, or being dismounting reconstruction.
Summary of the invention
It is an object of the invention to overcome the deficiencies in the prior art, by carrying out appearance inspection to prestressed concrete beam bridge
On the basis of survey, material test, ultimate bearing capacity test and finite element modelling, using the methods of statistical regression, examine simultaneously
Durability reparation and visual condition after worry calamity, and it is consistent with 5 grades of classification in current highway bridge technology status assessment standard
On the basis of, it proposes bearing capacity detection method after a kind of Mid and minor spans prestressed concrete beam bridge excessive fire, avoids complicated after excessive fire
Finite element method, fast quantification obtain structural limits bearing capacity reduced rate, for bridge strengthening be transformed foundation is provided.
Bearing capacity detection method after a kind of Mid and minor spans prestressed concrete beam bridge excessive fire of the present invention is specific to flow
Journey is as follows:
(1) it divides detection zone and numbers, the prestressed concrete beam bridge after excessive fire is divided and surveys area and numbers, divides and surveys
Consider that across footpath and deck-siding, survey area should not exceed 0.25m when area2, the every area Pian Liangce sum n is not less than 40；
(2) each survey area Testing index, including concrete color, rebound value, hammering reaction, fire crack, concrete are obtained
The measured value of area and the depth of falling off totally 5 class evaluation indexes；
(3) each survey area Synthetic Scale D is calculatedi, the 5 class evaluation index is calculated according to area's impairment scale identification grading meter is surveyed
Damage scale, take Synthetic Scale Di of the peak as the survey area；
(4) each survey area weights omega is calculatedi, each weights omega after surveying area's excessive fire is calculated according to formula 1i；
In formula: Sud,i--- basic combined effect group is acted under ultimate limit states at i-th of survey district center position
Close design value；Using " highway bridge and culvert designs general specification JTG D60-2015 " 4.1.6-1 formula when calculating:
ηi--- consider web shearing resistance amplification coefficient, if the i-th lateral areas center apart from pivot distance less than 0.25 times across
Diameter, ηi1.2 are taken, otherwise takes 1.0；
The survey area sum of n --- division；
(5) calculated prestressing force concrete beam bridge impairment scale Z, according to the synthesis of 2 calculated prestressing force concrete beam bridge of formula
Impairment scale Z, the value are final impairment scale,
(6) according to the section of complex damage grade Z, prestressed concrete beam bridge excessive fire bearing capacity reduced rate is determined.
In the present invention, tensile region and compressive region are divided into the prestressed concrete beam bridge survey after the excessive fire.
In the present invention, consider evaluation index deterioration degree to the difficulty of bridge structure bearing capacity, durability and subsequent reparation
Easily, evaluation index is divided into concrete color, rebound value, hammering reaction, fire crack, concrete fall off area and depth 5 totally
Class, wherein color change, the attainable highest scale of rebound value evaluation index institute are 3, hammering reaction, fire fracture evaluation index
The attainable highest scale of institute is 4, and the attainable highest scale of area and depth evaluation index institute that falls off is 5.
In the present invention, is touched by naked eyes and auxiliary and judge Concrete after Fire color change situation one by one；Rebound value is straight
It connects and estimates concrete strength with rebound method, the case where for cannot directly be estimated with rebound method, consider test angle and test surfaces
Only rebound value is compared under amendment, and then judges degree of injury；Cored slab detection zone is hammered one by one using claw hammer, is led to
Cross echo, whether concrete surface leaves a trace, whether crushes slump judges the qualitative material cracking in Method Pre-stress Concrete Hollow Slab bottom, empty journey
Degree when detection, when to the hammering of each surveys area, covers the survey area, using the point of material degradation most serious as the survey area scale as far as possible；
By naked eyes and portable fracture width comparison card, the crack occurred in area is surveyed in detection one by one, only considers to split as caused by fire
Seam；It falls off depth capacity and area in conjunction with horizontal ruler, vernier caliper measurement concrete, depth estimates reading to 1mm, and area is accurate to
1cm2, concrete falling-off depth is measured indirectly by way of measuring web turning point to beam bottom distance in on-site test.
In the present invention, when actually detected, concrete color, rebound value, hammering reaction, fire fracture evaluation index are only to mixed
Solidifying soil does not fall off that survey area effective, if survey in area have occurred and that concrete falls off if only consider to fall off evaluation index.
In the present invention, for excessive fire after prestressed concrete beam bridge tensile region and compressive region, respectively according to Tables 1 and 2
The shown damage scale surveyed area's impairment scale D identification grading meter and count stating 5 class evaluation indexes in, 5 class evaluation index of the area Qu Ce
Synthetic Scale Di of the impairment scale peak as the survey area.In the present invention, adding for all survey areas Synthetic Scale of every beam is taken
Excessive fire complex damage scale Z of the weight average value as the beam.
In the present invention, according to the section of Z, inquiry table 3 determines prestressed concrete beam bridge excessive fire bearing capacity reduced rate.
Wherein, RimStrength test curve is corresponded to correspond to concrete grade used in prestressed concrete beam when carbonation depth is 0
Rebound value；δ is protective layer thickness；[2,2.5) impairment scale Z is represented more than or equal to 2, less than 2.5；[2.5,3.5) represent damage
Grade Z is more than or equal to 2.5, less than 3.5；[3.5,4.5) impairment scale Z is represented more than or equal to 3.5, less than 4.5；[4.5,5] generation
Table impairment scale Z is more than or equal to 4.5, is less than or equal to 5.
Table 1 surveys area's impairment scale D identification grading table-tensile region directly by fire
Table 2 surveys area's impairment scale D identification grading table-compressive region directly by fire
Prestressed concrete superstructure component damage state grade after 3 fire of table
Compared with prior art, bearing capacity is examined after Mid and minor spans prestressed concrete beam bridge bridge excessive fire of the present invention
Survey method, has the following advantages that and marked improvement: this method is easy to implement, and feasibility is high, and result credibility is big, and fast quantification obtains
Structural limits bearing capacity reduced rate is taken, finite element method complicated after over-firing is avoided, is Mid and minor spans prestressed concrete
Residual Loading Capacity is obtained after native beam bridge bridge fire, reappraises whether structure needs repairing and reinforcement to put back into, Yi Huowei
It removes to rebuild and reference is provided.
Detailed description of the invention
Fig. 1 bridge superstructure schematic diagram (unit: cm), plate spaning middle section in (a), (b) side plate spaning middle section, (c) half
Elevation；
Fig. 2 hollow slab girder bottom detection zone number schematic diagram (single-beam)；
Fig. 3 concrete locally becomes pink colour；
Fig. 4 concrete locally becomes khaki；
Fig. 5 inside concrete crack；
Fig. 6 fire leads to thick fracture network；
Fig. 7 fire leads to microcrack net；
Fig. 8 fire leads to thick fracture network；
Fig. 9 fire leads to microcrack net；
The 7th hole girder of Figure 10 respectively surveys area's damage scale figure；
The 8th hole girder of Figure 11 respectively surveys area's damage scale figure；
Each girder complex damage scale Z of Figure 12；
Figure 13 load placement figure；
The testing ground Figure 14；
Figure 15 typical damage form.
Specific embodiment
Specific embodiments of the present invention will be further explained with reference to the accompanying drawing.
Embodiment 1
Embodiment 1 is related to Testing and appraisal method after certain bridge on highway excessive fire, and bridge overview is that 9 × 20m freely-supported is first opened
Prestressed concrete prefabricated board structure, two-way six-lane, Division range design, bridge overall with 34.5m, single width bridge setting 16 are hollow
Plate-girder, the bridge angle of cut are 52.74 degree, concrete grade C50.Infrastructure uses four-column type bridge pier, floor platform, cast-in-situ bored pile
Basis.Deck paving uses 10cm asphalt concrete pavement.Bridge be open to the traffic the time be 2007, under across certain provincial highway.Because of oil
Tank, which reaches the bridge and issues, makes trouble therefore turns on one's side and burn, immediately tank rupture, and occurrence of large-area burning over-fires the time nearly 2
Hour.Superstructure schematic diagram is shown in attached drawing 1.
1, region and number explanation are divided
It is obtained in order to facilitate on-site test initial data, follow-up study needs, hollow slab girder bottom is divided and numbered,
Specific coding rule is as follows:
Since small pile No. beam-ends acute angle is to span centre 1.5m divide survey area (longitudinal mono- lattice of 0.5m, lateral mono- lattice of 0.5m, each
Cored slab amounts to 70 areas Ge Ce；
Survey area number from small pile No. side be 1#, successively increased to big pile No. side, pile No. augment direction divide from left to right A,
B；Indicate that vertical bridge surveys area to 27# as 27A# surveys area, direction across bridge is left side survey area；It surveys area's number and sees attached drawing 2；
2, detection method and typical damage
(1) concrete color changes
It is touched by naked eyes and auxiliary and judges cored slab Concrete after Fire color change situation one by one, if having in survey area a
Other aggregate discoloration, then the color of the aggregate represents survey area concrete color change；When on-site test, only for concrete without de-
The area Luo Ce is detected；Typical damage is shown in 3~attached drawing of attached drawing 4 in on-site test；
(2) rebound value
Since the bridge concrete directly cannot be estimated concrete strength with rebound method by influence of fire, and age surpasses already
The unified strength test curve in whole nation 1000d range on probation out, therefore, this detection only (considers test angle and test to rebound value
Face amendment) it compares, and then judge degree of injury；Original design cored slab uses C50 concrete, when corresponding carbonation depth is 0
Rebound value Rim=43.83；When on-site test, falls off slight only for concrete or test rebound value without the survey area to fall off；
(3) hammering reaction
Using claw hammer one by one to cored slab detection zone hammer, whether left a trace by echo, concrete surface, whether
It crushes slump and judges the qualitative material cracking in Method Pre-stress Concrete Hollow Slab bottom, empty degree；When on-site test, when being hammered to each survey area, as far as possible
The survey area is covered, using the point of material degradation most serious as the survey area scale；It is hammered into shape only for concrete without the survey area to fall off
It hits；5~attached drawing of attached drawing 6 is to hammer the region core sample that Reaction degree is 3, and concrete is internal under fire temperature effect to have cracked；
(4) concrete fire crack
By naked eyes and portable fracture width comparison card, the crack occurred in area is surveyed in detection one by one, only considers to be led by fire
The crack of cause；Typical damage is shown in 6~attached drawing of attached drawing 7 in on-site test；
(5) concrete falling-off depth and area
It falls off depth capacity and area in conjunction with horizontal ruler, vernier caliper measurement concrete, depth estimates reading to 1mm, area essence
Really to 1cm2；Concrete falling-off depth can be measured in actually detected by indirect means, such as measures web turning point to beam bottom distance
Etc. modes, as far as possible raising measurement accuracy；Typical damage is shown in 8~attached drawing of attached drawing 9 in on-site test；
3, qualification result
Each area's damage scale of surveying is illustrated to see that 10~attached drawing of attached drawing 11, attached drawing 12 are hollow slab girder Comprehensive Assessment scale；Comparison
Figure 10~Figure 12, injuring rule coincide substantially, and respectively centered on R-7-1# beam, R-8-7# beam, degree of injury is gradually to two
Side reduces, thus can the preliminary judgement comprehensive evaluation it is feasible；R-8-7# beam Synthetic Scale is up to 4.8, and performance is bad after fire
Change is most obvious, and R-7-1# beam, the survey area that R-7-2# beam assessment scale is 2 are most, substantially not by influence of fire；
4, the verifying of method
(1) experimental rig and process
One is respectively taken to carry out carrying energy on the beam that complex damage scale is respectively 2 ± 0.2,3 ± 0.2,4 ± 0.2,5 ± 0.2
Power test, see Table 3 for details；According to appearance testing result, the damage of hollow slab girder web is less, is not burnt directly by fire source in fire process
It burns, shear resistant capacity is influenced little.In addition, concrete beam bridge fire destroys mainly curved according to the paper published
Based on folding destroys, therefore based on this experiment tested with bending bearing capacity.Loading device is loaded using reaction frame combination jack,
Using concrete block is expanded as anchor foundation, power transmission is carried out by fining twisted steel and lateral steelframe.Load placement is detailed in down
Attached drawing 13~14.
1 test beam of subordinate list number and score
The key reaction of structure during test are as follows: as load increases, beam body amount of deflection constantly becomes larger, deformation from linearly by
It walks to nonlinear development；Crack occurs within the scope of span centre 5m first, and with the increase of loading capacity, crack is increasing, original
Crack gradually extends, and width is continuously increased, and cracking range is gradually to prolonging Shen at fulcrum；4 beam load termination conditions are tension master
Maximum perpendicular fracture width is more than 1.5mm at reinforcing bar.Typical damage -form sees below attached drawing 15.
(2) test result
Load carrying capacity test result, which summarizes, is shown in Table 5, knows that 2#, 3#, 4#, 5# beam ultimate bending moment successively reduce by table, wherein 5#
Ultimate bending moment does not over-fire the 76.4% of beam only, reduces up to 23.6%；2#, 3#, 4#, 5# beam ultimate bending moment correspond to deflection value gradually
It increases, i.e. excessive fire damage is more serious, and limiting damage gradually switchs to brittle break by ductile fracture, especially the most with 5# beam brittle break
Obviously, limiting damage amount of deflection is only 28.5% before over-firing, with Concrete after Fire superstructure component damage state above etc.
" structure serious calcination damage, structural-load-carrying capacity are largely lost, crisis mechanism safety, it is necessary to or necessary for the situation description of grade
Take immediately safety support, thoroughly reinforce or remove replacement measure " principle be consistent.
2 bending bearing capacity test result of subordinate list
It is fallen off 5 class such as area and depth based on conventional concrete color, rebound value, hammering reaction, fire crack, concrete
Testing index proposes a kind of Mid and minor spans excessive fire beam Damage identification method, by the feasibility of load carrying capacity test verification method,
Different damage hollow slab girder bending resistance failure modes are compared, are held to obtain residue after Mid and minor spans prestressed concrete beam bridge bridge fire
Loading capability, reappraises whether structure needs repairing and reinforcement to put back into, or provides reference to remove to rebuild.
Claims (7)
1. bearing capacity detection method after a kind of Mid and minor spans prestressed concrete beam bridge excessive fire, which is characterized in that detailed process
It is as follows:
(1) it divides detection zone and numbers, the prestressed concrete beam bridge after excessive fire is divided and surveys area and numbers, when dividing survey area
Consider that across footpath and deck-siding, survey area should not exceed 0.25m2, the every area Pian Liangce sum n is not less than 40；
(2) obtain each surveys area Testing index, including concrete color, rebound value, hammer reaction, fire crack, concrete fall off
The measured value of area and depth totally 5 class evaluation indexes；
(3) each survey area Synthetic Scale D is calculatedi, identify that grading meter calculates the damage of the 5 class evaluation index according to area's impairment scale is surveyed
Hurt scale, takes Synthetic Scale D of the peak as the survey areai；
(4) each survey area weights omega is calculatedi, each weights omega after surveying area's excessive fire is calculated according to formula 1i；
In formula: Sud,i--- basic combined effect Combination Design is acted under ultimate limit states at i-th of survey district center position
Value；Using " highway bridge and culvert designs general specification JTG D60-2015 " 4.1.6-1 formula when calculating:
ηi--- web shearing resistance amplification coefficient is considered, if the i-th lateral areas center is apart from less than 0.25 times across footpath of pivot distance, ηi
1.2 are taken, otherwise takes 1.0；
The survey area sum of n --- division；
(5) calculated prestressing force concrete beam bridge impairment scale Z, according to the complex damage of 2 calculated prestressing force concrete beam bridge of formula
Grade Z, the value are final impairment scale,
(6) according to the section of complex damage grade Z, prestressed concrete beam bridge excessive fire bearing capacity reduced rate is determined.
2. bearing capacity detection method after a kind of Mid and minor spans prestressed concrete beam bridge excessive fire according to claim 1,
It is characterized in that, being touched by naked eyes and auxiliary in the process (2) and judging Concrete after Fire color change situation one by one；
Rebound value directly estimates concrete strength with rebound method, the case where for cannot directly be estimated with rebound method, considers test
Only rebound value is compared under angle and test surfaces amendment, and then judges degree of injury；
Cored slab detection zone is hammered one by one using claw hammer, whether left a trace, whether crushed by echo, concrete surface
Slump judges the qualitative material cracking in Method Pre-stress Concrete Hollow Slab bottom, empty degree, when detection, when to the hammering of each surveys area, covers the survey as far as possible
Area, using the point of material degradation most serious as the survey area scale；
By naked eyes and portable fracture width comparison card, the crack occurred in area is surveyed in detection one by one, is only considered as caused by fire
Crack；
It falls off depth capacity and area in conjunction with horizontal ruler, vernier caliper measurement concrete, depth estimates reading to 1mm, and area is accurate to
1cm2, concrete falling-off depth is measured indirectly by way of measuring web turning point to beam bottom distance in on-site test.
3. bearing capacity detection method after a kind of Mid and minor spans prestressed concrete beam bridge excessive fire according to claim 1,
It is characterized in that, when actually detected, concrete color, rebound value, hammering reaction, fire fracture evaluation index only to concrete not
Falling off, it is effective to survey area, if survey in area have occurred and that concrete falls off if only consider the evaluation index that falls off.
4. bearing capacity detects after a kind of Mid and minor spans prestressed concrete beam bridge excessive fire according to claim 1 to 3
Method, which is characterized in that tensile region and compressive region are divided into the prestressed concrete beam bridge survey after the excessive fire.
5. bearing capacity detection method after a kind of Mid and minor spans prestressed concrete beam bridge excessive fire according to claim 4,
It is characterized in that, the prestressed concrete beam bridge tensile region after the excessive fire, is commented according to the identification of survey area's impairment scale D shown in table 1
Grade meter counts stating the damage scale of 5 class evaluation indexes in, and the impairment scale peak of 5 class evaluation index of the area Qu Ce is as the survey area
Synthetic Scale Di；Wherein RimTo correspond to, concrete grade used in prestressed concrete beam when carbonation depth is 0 is corresponding to be surveyed by force
Curve rebound value, δ are protective layer thickness；
Table 1 surveys area's impairment scale D identification grading table-tensile region directly by fire
6. bearing capacity detection method after a kind of Mid and minor spans prestressed concrete beam bridge excessive fire according to claim 4,
It is characterized in that, the prestressed concrete beam bridge compressive region after the excessive fire, is commented according to the identification of survey area's impairment scale D shown in table 2
Grade meter counts stating the damage scale of 5 class evaluation indexes in, and the impairment scale peak of 5 class evaluation index of the area Qu Ce is as the survey area
Synthetic Scale Di；Wherein RimTo correspond to, concrete grade used in prestressed concrete beam when carbonation depth is 0 is corresponding to be surveyed by force
Curve rebound value, δ are protective layer thickness；
Table 2 surveys area's impairment scale D identification grading table-compressive region directly by fire
7. bearing capacity detection method after a kind of Mid and minor spans prestressed concrete beam bridge excessive fire according to claim 1,
It is characterized in that, inquiry table 3 is held after obtaining prestressed concrete beam bridge excessive fire according to the section where complex damage grade Z
Loading capability reduced rate；Girder does not comment 1 class after wherein over-firing；It is seriously destroyed after concrete girder fire, it is difficult to which reinforcement and repair needs
When removing or replacing, which directly can be chosen as 5 classes for excessive fire technology status grade F.
Prestressed concrete superstructure component damage state grade after 3 fire of table
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