Betonarme perdenin patlama etkilerine karşı lineer olmayan düzlem dışı davranışı
Out of plane nonlineer behavior of reinforced concrete shear wall
Yazar: ŞENER KÖLEMENOĞLU
Danışman: PROF. DR. KUTLU DARILMAZ
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Yapı Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2021
Konu: İnşaat Mühendisliği = Civil Engineering

Özet:
Günümüzde sanayi ürünlerine olan talebin yükselmesi ile birlikte bu ürünlerin üretim sürecinde bulunan patlayıcı maddelerin kullanımı artmış ve ulaşılması kolay hale gelmiştir. Bu durum patlama gibi yapılara ciddi hasarlar verebilen riskler arttırmaktadır. Bu sebeple patlamaya dayanıklı yapı tasarımını konu alan araştırmalar endüstriyel tesislerin artması ile yoğunlaşmıştır. Yapılan araştırmalara bakıldığında, patlamanın yapı üzerine etkisi genel olarak eleman bazında değerlendirilmektedir. Ülkemizde ve dünyada patlamanın yapılar üzerine etkisini eleman bazında inceleyen araştırmalar, genellikle tek serbestlik dereceli sistemler ya da sonlu elemanlar yöntemi ile kurulan detaylı modeller üzerinden yapılmıştır. Bunun yanında basınç-itme diyagramları olarak adlandırılan, yapının idealize patlama yüklerine karşı kapasitsini ifade eden eğriler, patlamanın etkilerini inceleyen birçok araştırmanın içeriğinde bulunmaktadır. Bu eğriler sayesinde elemanın patlama etkileri altındaki davranışı kolaylıkla yorumlanabilmektedir.
Yapılan literatür taraması sonucunda, betonarme elemanların patlama etkilerine karşı lineer olmayan davranışını, kolaylıkla modellenebilen çok serbestlik dereceli çubuk modeller üzerinden inceleyen araştırmalar oldukça az olarak gözlemlenmiştir. Bu çalışmada betonarme bir perdenin çok serbestlik dereceli modeli kurulmuş, lineer olmayan davranış için eğilme mafsalları tanımlanmış ve patlama durumlarına maruz bırakılmıştır. Birçok araştırmada olduğu gibi sonuçlar elde edilen basınç-itme diyagramları üzerinden verilmiştir.

Abstract:
Nowadays, due to the increase in the demand for industrial products, the use of explosives in the industrial process of the products has increased and it has become easy to reach, which leads to increase the risks that can cause serious damage to structures such as explosions. For this reason, research on blast resisting design has intensified with the increase in industrial facilities. 
Considering the researches, the effect of the explosion on the structure is generally evaluated on an element basis. Studies examining the effects of explosions on structures in our country and in the world, have generally been carried out on single degree-of-freedom systems or detailed models established with the finite element method. In addition, curves that express the capacity of the structure against idealized explosion loads, called pressure-impulse diagrams, are in the content of many studies examining the effects of blast. According to these curves, the behavior of the element under explosion effects can be easily interpreted. 
As a result of the literature review, very few studies have been observed that examine the nonlinear behavior of reinforced concrete members against explosion effects through easily modelled multi-degree-of-freedom non-linear systems. Main aim of this study is research the modelling technique of blast and examining the effect of blast on the multi-degree-of-freedom non-linear reinforced concrete systems.
In this study, a multi-degree-of-freedom model with nonlinear bending hinges of a reinforced concrete shear wall was constructed as a frame member. The wall was fixed at two ends, and had three bending hinges at supports and span sections. In order to determine reinforcement of shear wall, push-over analysis was done. According to push-over analysis, shear capacity of the wall in out-of-plane direction was adjusted by choosing the transverse reinforcement as a equal to bending capacity. As a result, shear wall collapsed under the push-over analysis due to shear at the same time that the bending capacity of all hinges were reached.
Due to bending hinges, model was behave non-linear in bending but, it behave linear in shear on out-of-plane direction. Behavior of bending hinges were calculated from the material stress-strain behavior. Concrete class was chosen as a C30, and reinforcement material properties were taken from the S420 class steel.
30 different blast scenarios were determined in order to expose to shear wall in out of plane direction. When the scenarios were determined, nine different scaled distances and four different explosive amount were used. Therefore, scaled distance and explosive amount would be attributed to results of the analysis. In addition the scenarios, three pressure-impulse diagrams which represent the limits yielding of the hinges, collapsing of the hinges and reaching the shear capacity of the member respectively were modelled. Thus, analysis can be compared with pressure-impulse diagrams. 
There were five different zone in the pressure-impulse diagrams due to 3 different curves. Each zone represented if upper curve limits reached or not. One of them was the safe zone which below all curves. Other one was the zone between shear and yield curves which determine the area to yield without collapse. The third one represented shear collapse without yield because it located on the behind the yield curves. The fourth one was the zone between the shear and bending failure curves which represent the shear failure after the yielding of the hinges. And the last area represented the collapse from bending or shear after the yield.
30 different blast scenarios pressure-time curves were obtained and defined on the shear wall out-of-plane direction as a time history pressure load. Then, analysis was done as a non-linear time history. According to analysis, four different results were observed, which were different from the pressure impulse diagrams. These were the result that shear collapse without yield, shear collapse with yield, yield without collapse and elastic behavior, respectively. 
When the result of the non-linear time history analysis of blast scenarios and pressure-impulse diagrams were compared, two situation were drawn the attention. One of them was the bending collapse was not observed in the time-history analysis. The other one was that some time-history results of blast scenario were not fitted with the pressure-impulse diagrams.
According to numeric study and literature review, it can be said that although the shear capacity of the modelled shear wall is equal to bending capacity, impulsive load like blast leads to collapse due to exceeding the shear capacity, which is brittle. This can be attributed to mode shapes of the member. In impulsive regime, displacement profile of structural system leads to more increase in the shear demand of the support section rather than the push-over cases. Therefore, it must be said that the shear capacity of the member under the impulsive load like blast must be check even if the shear capacity is equal to bending capacity.