Eğilme, kesme ve eksenel basın etkisindeki kolonların kayma dayanım kapasitelerinin belirlenmesi için deneysel bir çalışma
An Experimental study for investigation the shear carrying capacity of columns under combined bending, shear and axial compression
- Tez No: 39235
- Danışmanlar: PROF.DR. HASAN BODUROĞLU
- Tez Türü: Doktora
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Dayanıklılık, Kolonlar, Durability, Columns
- Yıl: 1993
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
ÖZET Bu çalışmanın amacı, eğilme momenti, kesme ve eksenel normal basınç kuvvetlerinin birlikte monotonik yüklemesi altında; kolon boyuna donatısının, etriye aralıklarının (özellikle kolon sarılma ve gövde bölgeleri), kolonun etkili yüksekliğinin [ho], çalışan yöndeki kenar boyutuna (derinlik) [D] oranının ve beton basınç dayanımının orta yükseklikli binaların alt katlarındaki kare veya dikdörtgen kesitli betonarme kolonların moment taşıma kapasitesine ve kayma dayanımlarına etkilerinin araştırılmasıdır. Konuyla ilgili geniş bir literatür araştırması yapılmıştır. Özellikle Japonya'da kullanılan ve Amerika Birleşik Devletleri'nde kullanılmaya başlanan Japon Sismik Endeks Yöntemi (JSEY)'nde verilen ikinci derece değerlendirmelerdeki E0 yapının davranışı ile ilgili alt endeksin hesabında kullanılan Qmu ve Qsu kolon kayma dayanımı yarı-ampirik formülleri ile; yapılan kolon testlerinde bulunan sonuçlar karşılaştırılmıştır. Bu çalışmada, 3 ayrı beton kalitesinde, 4012, 4014, 4016, 5016 ve 6016 boyuna donatıları, 08/5, 08/10, 08/12,5, 08/15, 08/20, 08/25 etriyeli, bir adet etriyesiz ve h0/D=1,6; 2; 3; 4 değerlerinin değişken olarak alındığı toplam 30 adet birebir ölçekli, 25cm x 25cm enine kesitli kolon test numuneleri üzerinde yapılan Laboratuvar araştırmalarının sonuçları verilmiştir. İstanbul Teknik Üniversitesi İnşaat Fakültesi Yapı Malzemesi Laboratuvarı'nda bulunan yükleme çerçevesi kullanılarak, kolon uç momentleri, kesme ve eksenel normal basınç kuvvetleri birlikte bütün numunelere monoton yükleme olarak uygulanmıştır. Bazı kolon test numunelerinin (9 adet) davranışları tek işaretli tekrarlı yük altında, bazı diğer kolon test numunelerinin (4 adet) davranışları da ters işaretli kolon uç momentlerinin kesme ve eksenel normal basınç kuvvetleri ile birlikte etkidiği monoton yükleme altında incelenmiştir. Test sonuçları ile Japon Sismik Endeks Yöntemi (JSEY) kullanılarak elde edilen kolon kayma dayanımı sonuçları karşılaştırılmıştır. Yurdumuz şartları göz önünde bulundurularak, orta yükseklikli betonarme bina kolonlarında,“JSEY”kapsamında önerilen kolon kayma yarı-ampirik formülünün kullanılabileceği görülmüştür. X 1 V
Özet (Çeviri)
Thirty column test specimens with four different groups were tested and compared with the codes of different countries. The seismic capacity of a column is closely related to its strength and ductility. In order to determine the shear carrying capacity of columns, a series of tests is conducted on full- scale specimens in the Structural Engineering Laboratories of Istanbul Technical University. The column is loaded axially with shear and bending moment to represent the actual loading conditions during an earthquake. In these tests, extremely short columns with three different low concrete strength, different shear reinforcement configurations, and different column height to depth (fVD) ratios are taken into account. Generally, columns failing in shear mode must be avoided. Most of the short columns, which are caused by the placement of the non structural walls, addition of some partitions due to architectural reasons, and mostly the needs of the window openings at the basement floors, are damaged and collapsed in shear. In this study, extremely short column is defined as a column with a clear height to depth ratio less than two. The purpose of this study is to investigate the effects of longitudinal reinforcement, stirrup's spacing, h0 /D ratio and concrete strength on shear carrying capacities in the square section columns under monotonically acting combined flexure, shear, and axial compression. Detailed descriptions of the test column specimens, the loading and compression test frames, experimental set-up and testing procedures, experimental program, and the results with the interpretations are given. In the experimental program, 1/1 scale 30 test column specimens with 25cm. by 25 cm. cross section and four different height were tested. Available literature shows that a large number of tests have been performed to study the behavior and strength of concrete beams failing in shear. As compared to beams, few columns have been tested. Most of the past studies on shear behavior of reinforced concrete elements have mainly been experimental and concerned with the behavior under monotonic loading, few studies have actually been made in shear behavior under earthquake-induced load reversal. Post earthquake damage assessments of some of the buildings revealed that the damages were due to poorly reinforced structural elements and low concrete strength. One of the several methods to determine the seismic capacity of the existing buildings is the seismic screening method given in the Standard for Evaluating of Seismic Capacity of Existing Reinforced Concrete Buildings, 1977. This standard has been developed after the Tokachi-Oki earthquake in 1968, and complied under the XVsupervision of Japan Building Disaster Prevention Association, Ministry of Construction in 1977, and put into practice as a standard for classifying the earthquake resistance capacities of the existing reinforced concrete buildings in Japan. In this study, the standard is shortly called“Japanese Seismic Indexing Method-JSIM.”Adaptation of this method to other countries requires special care in predicting the seismic load carrying capacity of weakly reinforced columns with low concrete strength. In this study, shear carrying capacities of the test columns have been calculated in accordance with the semi-empirical formula proposed by JSIM given in Equation 1. Qsu = 0I053.pt0,23.(18+fc') M/Q.d + 0,12 where, Qs, at ag Pt B- d 0,85/\/p7fy~+0,1. N b.D 0,8.b.D 8 M/Q N shear strength (kilo-Newtons), ( CLU=QSU n+Qsu 12+Qsu2 area of tensile reinforcement (mm2), total longitudinal reinforcement area (mm2), tension reinforcement ratio, transverse shear reinforcement ratio (max.0,012), width of column section (mm), effective depth of column section (mm), 28-day cylinder compressive strength of concrete (MPa), yield strength of shear reinforcement (MPa), depth of column section (mm), shear span (mm), 1 < M/Q < 3; (M/Q s ho/2), axial compression force acting on column section (kN). (1) :+ Qsu,3) The results of the tests are compared with the calculated values according to JSIM as shown in Table 1. The nominal shear strengths of the test columns have also been calculated using the formulas given by some national building codes and comparison with the test results and JSIM values are given in Figure 1. The axial compression forces acting on the test specimens are kept as (0,11 ~ 0,25) x Nmax during the tests. The flexure strengths of the test columns Mu (N/mm2), have been calculated when Nmax > 0,4.b.D.f 'c > Ntest > 0.' wnere Nmax is given by using Nmax = b.D.f,c + ag.f y Mu = 0,8. at. fy. D + 0,5. Ntest. D. ( 1 - Ntest ) b.D.fc (2) (3) XVITable 1. JSIM shear strength values and test results with failure modes 3 en 3 «V l_ «I CD en «< 3 (0 > c cv (A t_ <D O -C !/) X (/I CO XVUThe shear force in a column failed in flexure Qmu, is the sum of the top and bottom end moments divided to clear height of the column: Omu = (Mut + Mub)/h0 (4) Qmu and Q^ values are compared to determine the failure mode. If Qsu is reached earlier than Qmu in a column then the shear strength is less than its flexural yield strength resulting a shear failure. 200 150 in I u or in < u (A 100 50 TS500 ACI CAN NZ BS A1J Q t Q Q rn, test su mu Figure 1. Comparison of test results with JSIM and national building codes. XVUlIn the experimental program, a series of thirty test specimens including short columns, representing full-scale models of the columns in a medium-rise reinforced concrete building were designed considering (TS 500, 1984) and (Seismic Code, 1975); as shown in Table 2. The column is loaded axially together with shear and end bending moments to simulate the similar loading conditions during an earthquake. The test specimens were placed on the beam supports which are hung by the high strength steel rods to the loading frame upper beam as shown in Figure 2. Lateral loading acting on the test columns is applied monotonically. The reinforcement details of the column specimens with formwork dimensions and loading system are given in Figure 3. The yield strengths of the plain bars for the shear and longitudinal reinforcements are 285 N/mm2 and 300 N/mm2 respectively have been found by conducting tensile tests. In the scope of the experimental program, thirty column test specimens with a different clear height ( 40cm., 50cm., 75cm., 100cm J.three different concrete cylinder strength (lON/mm^MN/mm^^N/mm2), and different reinforcements were considered. The column test specimens were designed in order to determine the effects of: -three different series of low concrete strength, -different stirrup ties' details, -different shear reinforcement ratios varying between 0.00 to %0.90, -different tensile reinforcement ratios varying between %0.36 to %0.97, -different column height to depth ratios, 1.6 ; 2.0 ; 3.0 ; 4.0 respectively, and -loading type. LOADING FRAME CAPPING L0AOING BEAM COLUMN SPECIMEN7 SURP0P£RT SUPP0RTN C0MPRES|I0N Figure 2. Experimental set-up. XIXTable 2. Test column details o - c S Z V w IK a. w %.5 ** o II a S a ii *?» </> T) O u ut o «M O o M, <A S a» a » (A T7 <o <4 ^ <o «o <o <o <© 'O <o m -o (M fM fM «o *- ao n. ao s. r». o o o o e o e 8SS33S8S88889 u% m m m ____ _ N (M (M M e e o o o s»55»ll3lssaa im <m im im o o o a a ICIC!C)CSSSS < «w I i I s; o u uüuuuuuuuuu MUM.- N rt ?* ı« ^ K. > e ~ <* s s s s s s S S 3 İM İM fM s s s - * * M* <o r^ o u u u in u> «ı «SınnSPISıv e o a a o m m SS8SSSSS sunns t» « « a ı/* lA (AllAOOfMrMUtlA“» '^* ^ _ » » ^ ^ SS22SSSS ». *. ^ ^ (M N IC R § § u »- s s I s ? <> r> » o> o> » CO CO 0Q 0Q 00 00 fM fM o e o o o o ** -* m « f > » 8 8 O» ö> »?.. N K o o *a ırt If* If* s. n. S. §.”««N^ftıftl^ U<-- '»-U - -.. 1,1 « « M“ ”U â â i s im s s s a.* ı/t <o l* *» m m m» İM İM İM XX4J712 d - 21cm. CN.T.S.3 TEST NO. 13 i SECTION A-A Figure 3. Details of column test specimens The test results (Qmax test) are 9iven in Fi9ure 4 bV comparing the calculated values of Qsu according to JSIM. Short column test specimens failed in shear when the flexure strengths of the column sections are high enough compared with the shear strengths. It is also seen that the extremely short column specimens (test no. s: 25, 26, 27 and 28) failed in shear where the calculated shear strengths (Qsu) are less than the maximum applied shear force during the test (Qmax test). and much,ess il!?en Qmu snear force corresponding to the flexure strength of the column section. XXI200 50 100 150 200 Observed Shear Strength, Q _ CkNl Figure 4. Comparison of Qsu and Qmax,test Conclusion The experimental results showed that the columns fail in shear mainly when the hp / D ratio is less than or equal to 2 as shown in Figure 4. Beyond this value, failure occurs in flexure. The calculated values according to the shear carrying capacity (ultimate shear strength)formula using the JSIM, and the nominal shear strengths based on some national building codes with the test results are shown in Figure 1. It can be seen that the shear carrying capacity formulas given in the Japanese Seismic Indexing Method (JSIM) and in these national building codes are in good agreement with the test results. Therefore, it is concluded that the formula given in the Japanese Seismic Indexing Method-JSIM to determine the shear carrying capacity of the columns can be used for adopting this method to low-medium rise reinforced concrete buildings in Turkey. XXll
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