Determination of permanent deformation of flexible pavements using finite element model

Nevezani zrnati materijal koji se koristi u savitljivim kolničkim konstrukcijama ponaša se elastoplastično pod utjecajem ponavljanih prometnih opterećenja. Trajne deformacije koje se javljaju na površini kolnika uslijed prometnog opterećenja jedan su od osnovnih problema koji negativno utječu na ponašanje kolničkih konstrukcija. Zbog toga su u novije vrijeme razvijeni brojni modeli za analizu trajnih deformacija, tj. za izračunavanje pojave kolotraga na kolnicima. Većina istraživanja koja se bave tim pitanjem temelje se na provedbi dinamičkih troosnih ispitivanja. U ovom je istraživanju deformabilnost nevezanih zrnatih materijala određena ispitivanjem prema metodi rezonantnog stupca. Također, umjesto određivanja ukupnih trajnih deformacija zbrajanjem izračunanih deformacija pojedinačnih slojeva kolnika, u ovom se radu na četiri različita tipa kolničkih konstrukcija provode dinamičke dvodimenzionalne osnosimetrične analize metodom konačnih elemenata kako bi se predvidjela ukupna trajna deformacija koja se javlja na površini kolnika nakon određenog broja ciklusa opterećenja. Nevezani slojevi za prvi modelirani tip kolničke konstrukcije sastoje se od prirodnog agregata. Nevezani nosivi sloj i/ili tamponski sloj preostalih triju kolničkih konstrukcija sastoji se od otpadnog materijala čelične zgure. Odnos trajnih deformacija i broja ciklusa opterećenja za sva četiri tipa kolničkih konstrukcija prikazan je na polulogaritamskim dijagramima. Za svaki je analizirani tip kolničke konstrukcije prikazana jednadžba trajnih deformacija.The unbound granular material used in flexible road pavements exhibits an elastoplastic behaviour under repetitive traffic loads. Permanent deformation occurring on pavement surface under traffic load is one of the main road pavement problems affecting road performance. Therefore, many permanent deformation models for calculating road pavement rutting have recently been developed by researchers. Most of these studies involve performance of dynamic triaxial tests. In this study, deformation characteristics of unbound granular materials are determined using the resonant column test. Then, instead of determining the total permanent deformation by summing up the calculated permanent deformations obtained in each pavement layer, dynamic 2D axisymmetric finite element analyses are performed for four different pavement cross sections to predict the total permanent deformation occurring on pavement surface under certain load cycles. The first modelled cross section of unbound granular material consists of natural aggregate. The base and/or subbase of remaining three cross sections consists of steel slag waste material. The permanent deformation versus load cycle is presented for four multi-layer road cross sections using semi logarithmic graphs. Finally, the permanent deformation model equation is developed for each pavement cross section using their fitting curves

Effect of curing time on selected properties of soil stabilized with fly ash, marble dust and waste sand for road sub-base materials

The properties of sub-base filling materials in highway construction are essential, as they can determine the performance of the road in service. Normally, the existing materials are removed and replaced with new materials that have adequate load-bearing capacity. Rising environmental concern and new environmental legislations have made construction professionals consider other methods. These methods include stabilizing the existing materials with other additives to improve their performance. Additives can be waste materials generated by different industries. In this work, the existing excavated soil is stabilized with waste materials. The wastes consisted of fly ash, marble dust and waste sand. The percentage addition of waste materials was 5%, 10%, 15% and 20% (by mass) of the existing soil. The soil/waste specimens were cured for 1, 7, 28, 56, 90 and 112 days before testing. Testing included the dry unit weight and unconfined compressive strength ( qu) as well as X-ray diffraction analysis and scanning electron microscopy observation. Also, the California Bearing Ratio values were obtained and are reported in this investigation. The results showed that the qu values increased with the increase in waste materials content. Also, there is tendency for the dry unit weight to increase with the increase in waste materials

Models for Energy Efficiency Obligation Systems through different perspectives

As environmental problems such as global warming has become increasingly prevalent, and with the rise in foreign dependence on fossil fuels, energy efficiency and energy saving programs and research have risen. This global focus on energy efficiency has accelerated studies on this subject in order to decrease foreign dependency on fossil fuels, to protect the environment, to minimize the effect of energy costs to national economies, and to assure the energy supply. With increasing population and fast economic development, energy consumption in Turkey has increased significantly. Therefore, current policies need to be updated and additional measures need to be implemented. The Energy Efficiency Strategy document states that Turkey aims to decrease its energy intensity by 20% by 2023, and accordingly new policies and strategies are being carried out in every sector to achieve this result. The uninterrupted, cost-effective, and globally sustainable energy supply is at the heart of national energy policies globally. The Energy Efficiency Obligation Scheme (EEOS) is among the fundamental tools created to increase energy efficiency in the European Union (EU). Many EU countries have successfully implemented EEOS, and further white certificate markets as a central tool for increasing energy efficiency. For example, Italy has seen particularly positive achievements with a white certificate market by avoiding consumption of 6.7 million tons of oil equivalent (TOE). The implementation of National Energy Efficiency Action Plan (NEEAP) in terms of energy saving was a great step in Turkey. In this document, EEOS has been analyzed in detail. All of these studies are expected to shed light on the energy efficiency liability system to be implemented in Turkey in the future. For this purpose, it is thought that the inclusion of energy service companies into these models will have a positive effect on the success of the system. Within the scope of this study, it has been concluded that energy resources and technologies should have the flexibility to be localized and to resist unexpected changes. Another reason to encourage incentive policies in energy efficiency will be to reduce energy importation.WOS:0006324682000032-s2.0-8509591691