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ABSTRAK

EFEK RESIDUAL STRESS TERHADAP KINERJA ELEMEN

LINK PADA STRUKTUR RANGKA BAJA BERPENGAKU

EKSENTRIK

Oleh

KURDI

NIM: 35013004

(Program Studi Doktor Teknik Sipil)

Efek tegangan sisa terhadap kinerja elemen link pada struktur rangka baja

berpengaku eksentrik penahan gaya lateral seperti beban gempa diteliti. Pengujian

secara eksperimen dilakukan dengan dua tahapan. Tahap pertama, sebanyak

delapan sampel dari elemen link diukur tegangan sisa dalam arah transversal,

longitudinal maupun normal. Besaran dan distribusi tegangan sisa diukur secara

eksperimental dengan cara Neutron Diffraction Method menggunakan alat DN1

PSTBM BATAN. Verifikasi secara numerik dengan uncouple transient thermal

static structural analysis dilakukan. Parameter geometri link seperti parameter

kondisi tumpuan saat pengelasan, luas daerah k, tebal pelat badan, jumlah lasan

dan jarak pengaku diteliti dalam penelitian ini. Selanjutnya, hubungan besaran

tegangan sisa dengan parameter dominan diusulkan untuk perbaikan kinerja dari

elemen link.

Tahap kedua sebanyak tiga link pendek yang telah diukur tegangan sisa diuji

menggunakan beban siklik sesuai denga pola pembebanan AISC 341-10. Satu link

merupakan link standar yang didesain sesuai AISC 341-10 dan dua link

modifikasi pada pelat pengaku badan. Perilaku elemen link dipelajari terutama

pengaruh tegangan sisa terhadap kinerja link. Hasil pengukuran menunjukkan

bahwa di dan sekitar area pengelasan antara pelat pengaku dengan pelat badan

serta pelat sayap atau yang biasa dinamakan daerah k menghasilkan tegangan sisa

tarik yang tinggi dan menjadi awal dimulainya crack saat beban luar diberikan.

Pemahaman yang baik mengenai besaran dan distribusi tegangan sisa saat desain

dan proses pengelasan dari elemen link terutama di daerah k, dapat meningkatkan

kinerja elemen link karena fraktur di daerah k dapat diperlambat, sehingga syarat

kapasitas inelastik sesuai AISC 341-10 dapat dicapai.

Temuan dari hasil elemen link modifikasi menghasilkan peningkatan parameter

kinerja link yaitu nilai daktilitas sebesar 30,90%, rotasi plastis sebesar 14,29%,

nilai overstrength sebesar 10,00% serta energi disipasi sebesar 41,56%

dibandingkan dengan link standar. Hasil pengujian eksperimental juga

menunjukkan bahwa nilai overstrength SNI 1729-2015 dan AISC 341-2010 tidak

cukup konservatif (tidak aman) terhadap nilai overstrength pengujian. Hal ini

menyebabkan desain elemen di luar link menjadi tidak aman sehingga harus

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diperkuat. Dari hasil penelitian ini, nilai overstrength untuk desain kekuatan

elemen di luar link (bresing, kolom, balok diluar link), diusulkan untuk dinaikkan

15% dari nilai overstrength SNI 1729-2015 dan AISC 341-2010.

Kata Kunci : tegangan sisa, link pendek, metode difraksi neutron, sruktur rangka

baja berpengaku eksentrik, daerah k.

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ABSTRACT

RESIDUAL STRESS EFFECT ON LINK ELEMENT OF

ECCENTRICALLY BRACED FRAME

By

KURDI

NIM: 35013004

(Doctoral Program of Civil Engineering)

This study determined the residual stress effects on the link element performance

of eccentrically braced frame as lateral force shields for earthquake loads.

Experimental tests were conducted in two stages. In the first stage, residual

stresses were measured in eight samples of the link elements in transversal,

longitudinal and normal directions. The magnitude and distribution of residual

stresses were measured experimentally by Neutron Diffraction Method using the

DN1 PSTBM BATAN tool. Verification was performed numerically using the

uncouple transient thermal static structural analysis. The study takes into account

the link geometry parameters, for example, the support condition during welding,

the extent of k area, the thickness of web plate, the number of welding and the

distance of stiffeners. Furthermore, the relationship between the magnitude of

residual stress with the dominant parameters was suggested for improvements of

link element performance.

In the second stage, the three shear links that had prior measurement of residual

stresses were tested using the cyclic loading as in the AISC 341-10 loading

pattern. The first link is the standard link designed as is the loading pattern of

AISC 341-10, whereas the other two links are modified links on the web plate

stiffeners. The behaviour of link element was studied with emphasis on the

influence of residual stresses to the link performance. The results of

measurements showed that the area on and around the welding area between the

stiffeners plate with the web and flange plates, or is commonly known as the k

area, generated high residual tensile stresses, hence initiated cracks during

external loading.

A good understanding on the magnitude and distribution of residual stresses

during the design and welding processes of the link element, particularly on the k

area, may increase the link performance as fractures on the k area may be

hampered, therefore could meet the requirements for inelastic capacity as set

forth in AISC 341-10.

Findings from the modified links resulted in overall increases of the parameters of

link performance, namely the ductility (30.90%), plastic rotation (14.29%),

overstrength value (10.00%) and dissipation energy (41.56%), compared to the

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standard link. The results of experimental tests also showed that the overstrength

values of SNI 1729-2015 and AISC 341-2010 were unlikely to be conservative

(unsafe) compared to the overstrength values in the tests. This has caused the

design of element outside of the link to be unsafe, therefore it has to be

strengthened. The research results of the overstrength value for the design of

resistance in the element outside of the link (bracing, column, beam outside of the

link) was suggested to increase 15% from the overstrength value of SNI 1729-

2015 and AISC 341-2010.

Keywords: residual stress, shear link, neutron diffraction method, eccentrically

braced steel frame structure, k area.