Bilyeli kauçuk mesnetin değişik sıcaklıklardaki düşük yükleme hızları ve sünme altındaki davranışının belirlenmesi

TÜBİTAK MAG01.08.2010Sismik yalıtım sistemleri; köprü ayakları, havaalanları, hastaneler gibi yapılarda ve çok sayıdaki diğer yapılarda, tehlikeli depremlerin yıkıcı etkilerini önlemek veya azaltmak için ülkemizde birçok önemli yapıda kullanılmıştır. Çok soğuk kışlara veya günlük sıcaklık değişikliklerinin fazla olduğu yerlerde inşa edilen yapılarda bulunan kauçuk esaslı sismik yalıtıcıların davranışları zorlu çevre koşullarına göre değişebilmektedir. Düşük sıcaklıklarda kauçuğun sertleştiği ve yapılara aktarılan yükü arttıran yüksek rijitliğe neden olduğu çeşitli kereler analitik ve deneysel olarak gözlenmiştir. Bu nedenle onların farklı yük ve sıcaklık altındaki davranışlarının deneysel olarak da iyi anlaşılmasında fayda vardır. Bu araştırma son yapılan deneysel çalışmanın (bilyeli kauçuk mesnet adıyla anılan yeni geliştirilen sismik yalıtıcı) bir tamamlayıcısıdır. Yeni geliştirilen bilyeli kauçuk mesnetlerin üretilme kolaylığına ek olarak maliyet ve enerji dağıtma kapasiteleri gibi avantajlı tarafları vardır. Ancak onların düşük sıcaklıklardaki ve düşük hızlardaki davranışları henüz detaylı bir şekilde araştırılmamıştır. Farklı sıcaklık değerlerinde eksenel yük, basınç yükü ve yanal yer değiştirmeye maruz kalan bilyeli kauçuk mesnetlerin davranışı incelenmiştir. Bu çalışma sonucunda bilyeli kauçuk mesnetlerin soğuk iklim şartlarında ve sünmeden dolayı oluşabilecek olası ağır yer değiştirme davranışı hakkında bilgi verilmiştir.Seismic isolation systems are used in structures like viaducts, airports, hospitals and numerous other structures for preventing or diminishing destructive effects of hazardous earthquakes. Structures constructed in places having extremely cold winters or drastic daily temperature differences have formidable environmental conditions for elastomer based seismic isolators. It is well known from analytical and experimental studies that rubber stiffen at low temperatures and cause higher rigidity which increase the load effects transmitted to structure. Therefore, their behaviors under different load and weather conditions must be well understood. This research is a complementary of recent experimental study (newly developed seismic isolator called ball rubber bearing). Ball rubber bearings are newly developed seismic isolators and have advantageous sides like manufacturing convenience in addition to their costs and energy dissipation capacities. However, their behaviors at low temperatures have not been examined yet. Behaviors of ball rubber bearings exposured to different temperatures in presence of axial load, compressive load and lateral displacement are examined. In this study, information on structural response of ball rubber bearings at cold climate and creep conditions is established

Potential Use of Waste Marble Powder as Adhesive Filler in the Manufacture of Laminated Veneer Lumber

Ayrilmis, Nadir/0000-0002-9991-4800; Ozdemir, Serkan/0000-0002-0421-0430WOS: 000351941000135The waste powder produced during the manufacture of marble, which is presently mostly discarded in landfills, has the potential for higher-valued usage. Recycling marble waste powder will contribute to the protection of nature as well as economic gain. The potential use of waste marble powder as filler in the adhesive for manufacturing of laminated veneer lumber (LVL) was investigated in this study. With this objective, LVL panels were manufactured by adding marble factory waste powder in different ratios to polyvinyl acetate (PVAc) and urea-formaldehyde (UF) adhesives. The waste powders of beige marbles and travertine marbles were mixed by weight with adhesives in the percentage levels of 0%, 10%, 20%, 30%, 40%, and 50%. Physical and mechanical tests were performed on the specimens obtained from the LVL panels. According to the results obtained from the present study, as compared to the control specimens, higher mechanical performance was obtained with the waste beige marble powder at high contents and with the waste travertine marble powder at low contents with the PVA adhesive. A poorer mechanical performance was found in the travertine powder with the UF adhesive. The dimensional stability of LVLs containing travertine powder was better than that of the LVLs containing beige marble powder

Effect of dietary formic acid on the in vitro ruminal fermentation parameters of barley-based concentrated mix feed of beef cattle

This study aimed to determine the effect of 0 (FA0) and 1, 2, 4 or 8 mL/kg (FA1, FA2, FA4 and FA8) formic acid addition to barley-based concentrated mix feed on in vitro gas kinetics [gas production from quickly soluble fraction (agas), gas production constant rate (cgas), gas production of insoluble fraction (bgas), potential gas production (a + b)gas], methane production, organic matter digestibility (OMD), metabolic energy (ME), net energy lactation (NEL), pH, ammonia-N, volatile fatty acids (VFAs), total bacteria count and number of ciliate protozoa. The in vitro cumulative gas production, cgas, bgas, (a + b)gas, ME, NEL and OMD values and ammonia-N concentration were decreased by formic acid (P < .05). Formic acid supplementation increased in vitro methane production up to about 12% (P < .05). Total bacteria count and number of protozoa and molar concentrations of total VFAs, acetic, propionic and butyric acids decreased with formic acid supplementation (P < .001). The numbers of Isotricha spp. and Dasytricha spp. increased with high formic acid (P < .001). The numbers of Diplodiniinae and Entodiniinae decreased in FA4 and FA8 groups (P < .05). The results indicated that formic acid addition to feed decreased ruminal microbiota count, digestibility, proteolysis and molar VFA values also increased ruminal methane emission. Besides, formic acid supplementation could increase energy loss during ruminal fermentation of feed