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The role of curing period on the engineering characteristics of a cement-stabilized soil

Abstract

Very often, pavements constructed in an economical manner or matching surface elevations of adjacent lanes cannot be designed for the soil conditions of the existing subgrade. Therefore, there is a need to stabilize the soil with an appropriate chemical substance in order to increase its strength to a satisfactory level. For the enhancement of subgrade soil strength characteristics, lime and cement are the most commonly used stabilizers. An experimental program was directed to the evaluation of a clayey soil and its mixtures with different cement contents performing tests on the index properties, the moisture-density relation, the unconfined compressive strength, and linear shrinkage. There is a definite improvement in strength. The time interval used to cure the prepared specimens affected positively both strength and plasticity features of the mixtures. A comparison with mixtures of the same soil with lime has been made, because of the wide use of lime in clay soil stabilization projects.

Open access
The safe road transport system approach

Abstract

More than 1,24 million people die each year on the worlds roads and between 20 to 50 million suffer from nonfatal injuries. The UN Road Safety Collaboration Meetings under the leadership of WHO developed the Programme for the Decade of Actions for road safety taking nations into the responsibility of improving their accident figures by the five pillars of a national Road Safety Policy, safer Roads, safer Vehicles, safer Road Users and Post Crash Care. It is this Safe System Approach that takes into consideration the land use, infrastructure and transport planning, road user’s abilities and limitations and the close cooperation of all governmental and none governmental stakeholders involved.

Following the European Transport Safety Council's (ETSC) 8th Road Safety Performance Index Report on Ranking EU Progress on Road Safety; June 2014 Romania has made progress during the last 10 year but had still the highest fatality rate of 93 fatalities per 1 million inhabitants in Europe. [1]

The contribution will present the main activities of the fife pillars with a focus on PIARC's Road Infrastructure Management tools to improve safety and function of the road infrastructure based on the experiences with the land use problems in Asian, African and European countries.

A GPS based accident data system will help researchers and practitioners to improve their countries road safety.

The report will show the important steps for safer roads which had been developed in Romania and how actions of short and long term measures on all five pillars have reduced the number of traffic victims remarkable in Eastern Germany after reunification and in addition how the hierarchy of motorways, 2+1 express roads, the rural roads and traffic calming in built up areas, have improved the economic development of cities and villages in a safe way.

Open access
Comparative design of the superstructure of timber bridges, using norm np 005 - 2003 and provisions of european standards

Abstract

The norms and standards for design of timber bridges, as well as other structures built from this material, were obsolete, design standards that were used dated from 1978 to 1980. The introduction of European Standards has created a new legislative framework in the field of designing and building timber bridges. Currently the design of such constructions use Norm NP 005-2003 and SR EN 1995-1-1: 2004 Eurocode 5: Design of timber structures. Part 1-1: General. Common rules and rules for buildings, SR EN 1995-2: 2005 Eurocode 5: Design of timber structures. Part 2: Bridges, along with their national annexes. The aim of this paper is to analyze the design of the beams for timber bridges in parallel, using on one hand Norm NP 005 - 2003, and on the other hand provisions of European standards. The design requirements for both norms as well as the results of a case study for a structural element of a timber bridge will be presented.

Open access
Constructing better roads with asphalt rubber

Abstract

Brazilians mixtures containing asphalt rubber were evaluated by mechanical laboratory tests. A conventional mixture with asphalt CAP-50/70 was produced as a mixture control. With the aim of compare the Brazilians mixtures performance, a Portuguese asphalt rubber mixture was tested as well. The testing set involved the determination of the mechanical properties, fatigue and permanent deformation, of asphalt rubber produced by wet process through two different systems: continuous blend and terminal blend. The asphalt rubber morphology was evaluated in order to determine the compatibility of the systems. The asphalt rubber mixtures exhibit good resistance to permanent deformation and prolonged fatigue life in relation to mixture control. Therefore it is concluded that the application of asphalt rubber alters the characteristics of asphalt mixture in a very beneficial way.

Open access
Design and research on the first polish FRP composite road bridge

Abstract

The main goal of the research project was to develop and demonstrate the first Polish FRP composite road bridge, starting from concept design and material research, and going thru manufacturing technique selection, detailed FEM analysis and structural testing of elements. The R&D project comprises also the proof test of the completed bridge as well as structural monitoring in exploitation period. The objective of the paper is the description of the bridge and its structural solutions, i.e. FRP box girders and lightweight concrete deck slab acting compositely. Further the FEM analysis of the girder and the bridge span made on design stage has been presented. The VARTM manufacturing technique was used for girders production. Its main steps have been also presented. Finally the research on the new FRP box girder with LRC slab (hybrid girder) has been briefly showed. The full scale prototype girder with the total length of 22 m was tested to evaluate its carrying capacity, modes of failure, basic dynamic parameters as well as overall behaviour under ultimate static load. The FRP girder met the prescribed serviceability and safety criteria. The FEM model of the girder was validated against testing results and was further used for bridge design. Thanks to R&D project the first Polish FRP bridge is likely to be built late autumn 2015. The output of the research project gives a very promising future for the FRP composite bridge application. The research works showed in the paper have been partially financed by the Polish National Centre for Research and Development in the frame of the research project “ComBridge” (www.com-bridge.pl).

Open access
Influence of aggregate gradation on hma mixes stability

Abstract

The load transfer capacity of pavements is to a great extend influenced by aggregates. About 85% of the total volume of hot mix asphalt (HMA) mixtures consists of aggregates; thus, they are greatly influenced by aggregate properties like angularity (shape), roughness (texture), and gradation. Aggregate gradation controls the structure of voids. Current specifications for aggregate properties in HMA pavements require the aggregate blend to fall within a specified range of gradation values. Although the abovementioned requirement has ensured the construction of high quality HMA pavements, the properties are largely empirical and they are not based on performance-related tests. Marshall Stability is in principle the resistance to plastic flow of cylindrical specimens of a bituminous mixture loaded on the lateral surface. It is the load carrying capacity of the mix at 60oC. Aggregates with different gradations from the broader area of Xanthi, Northern Greece, have been used to prepare specimens for stability testing of hot asphalt mixtures in the laboratory. The research focused on the evaluation of the influence of aggregates in the overall stability characteristics of the mixtures. The maximum stability value has been obtained with an open-graded mixture having 5% asphalt and aggregate size 2.36 mm. However, the stability of the dense graded mixture is higher than this maximum value.

Open access
New experiences with foamed bitumen asphalts in hungarian road building

Abstract

The use of low temperature (LT) asphalt products can result in a significant decrease of temperature required for asphalt production. This reduces energy costs and consumption. Moreover, safety during asphalt production and laying improves because the amount of potentially harmful vapours and aerosols decreases. Temperature decrease, in addition to the above, reduces the short-term ageing of bitumen in the asphalt production process, and ultimately has a positive impact on the durability of pavements.

COLAS Group in Hungary considers propagating the use of low temperature sorts of asphalt in road construction in Hungary as a high priority innovation task

Between 2012 and 2014, COLAS Group equipped its asphalt mixers with units from different manufacturers, capable of producing foamed bitumen, at four COLAS Group mixing plants in Hungary.

This was followed by several test production runs and course laying with asphalt mixes containing foamed bitumen. Some of the foam asphalt mixes were produced and laid at low temperatures. The other part of the mixes were produced at conventional temperature and were layed after 2 - 2.5 hours of transport. The test asphalt mixtures were made with 50/70 and 10/40-65 modified bitumen also containing 10-20% RA.

We compared the compactability of foamed bitumen mixtures produced with four different foaming kits. We produced Marshall specimens at various compaction temperatures, tested the bulk densities of the specimens, then represented the bulk densities subject to the compaction temperature. We established the following:

the Marshall bulk density (better compactability) of foamed bitumen asphalt mixes is higher for all asphalt types compared to the normal bitumen mixtures,

higher Marshall bulk density of foamed bitumen asphalt mixes can be achieved both in normal (50/70) and modified bitumen mixtures (25/55-65,10/40-65),

better compactability of foamed bitumen asphalt mixes is independent of the type of the foaming kit. It works for all types of foaming kits.

Open access
“Bowstring” Arches in Langer System Without Wind Bracing

Abstract

Arch bridges are slender structures and can be efficiently used in the range of medium to large spans. These structures have an improved aesthetic aspect and in the same time a low construction height, with obvious advantages regarding reduced costs in the infrastructuers and their foundations.

For this type of structures usually composite or orthotropic decks are used. Lately, innovative solutions have been used in designing arch bridges, especially discarding the top wind bracing system. The level of axial forces and bending moments in the arches and tie imply the design of sections with sufficient stiffness and strength in both directions in order to ensure the general stability of the arches, without the need for top wind bracing. Moreover, the cross section of the arches is not constant, but shifts in accordance with the variation of the bending moments, in order to ensure their lateral stability.

This paper studies a road bridge with parallel Bowstring arches, with a span of 108m and a carriageway 7.00m wide, sustained by a deck made up of crossbeams 2m apart and a concrete slab. The main beams are held by ties arranged in the Langer system, 10 to 14m apart from each other. The sag of the arches is 18m high.

The analyzed structure was proposed for construction in the city of Oradea and is used for crossing the “Crişul Repede” river, between Oneştilor street on the left bank and the Sovata, Fagului and Carpaţi streets on the right bank.

The performed analyses have the following two main objectives: to establish the critical load for which the failure of the arches occurs by instability and to underline the influence of different wind bracing systems on the bridge’s collapse loads respectively.

Open access
Comparative Study Between Experimental Results and the Numerical One of the Lateral Buckling Resistence for the Two Curved I Girders of a Curved Bridge Model

Rezumat

Articolul prezintă un studiul al rezistenţei la flambaj lateral pentru grinzile curbe utilizate la poduri.

Rezistenţa la flambaj lateral va fi evaluată printr-o analiză geometric şi fizic neliniară utilizând programul de calcul Lusas®, fară a considera imperfecţiunile de execuţie. Pentru a da veridicitate rezultatelor analitice, studiul numeric se va realiza pe unul din modelele fizice prezentate în lucrarea [1] care pune la dispoziţie valori ale încercărilor experimentale.

Geometria modelului fizic din lucrarea [1] se bazează pe o analiză dimensională a grinzilor curbe „I” utilizate în mod frecvent la poduri. Modelul fizic este alcătuit din două grinzi I curbe, dublu simetrice, prevăzute cu antretoaze şi contravântuiri la nivelul tălpilor. De antretoazele de capăt sunt sudate pe direcţia axei curbe două console scurte de lungime e .

Schema statică a structurii este grinda simplu rezemată cu console, ale cărei aparate de reazem sunt dispuse pe direcţia coardei. Consolele scurte vor fi încărcate cu prese hidraulice la o forţă P care are ca efect în grinda principală un moment încovoietor uniform având valoarea P *e şi forţă tăietoare zero.

Pentru analiza neliniară s-a folosit formularea Total Lagrange, împreună cu utilizarea metodei lungimii arcului modificat formulată de Crisfield. De asemenea s-a considerat comportarea neliniară a materialului.

Evaluarea rezistenţei la flambaj lateral constă în determinarea momentului încovoietor critic pentru care grinda îşi pierde stabilitatea. Comparaţia rezultatelor numerice cu cele experimentale preluate, confirmă posibilitatea evaluării numerice a rezistenţei la flambaj lateral pentru grinzile curbe.

Open access
Ecological Solutions Applied to Hot Mix Asphalt

Rezumat

Mixturile asfaltice sunt materiale compozite realizate din amestecuri de agregate naturale sau artificiale, filer și bitum, avȃnd la baza dozaje bine stabilite și o tehnologie adecvata astfel încȃt să rezulte un material rutier cât mai durabil posibil.

În urma studiilor efectuate pe plan internațional cât și pe plan național, s-a demostrat că se pot înlocui cu succes agregatele naturale cu zguri siderurgice sau de oțelărie, care prin prelucrare și sortare la dimensiuni necesare sunt cele mai adecvate din punct de vedere al proprietăților fizico-mecanice.

Mixturile asfaltice ecologice obținute prin înlocuirea agregatelor minerale cu zguri siderurgice vor intra în alcătuirea structurii rutiere, începand cu studiul pentru un strat de bază. Pentru evaluarea performanțelor mixturilor asfaltice în care agregatele naturale sunt înlocuite cu agregate artificiale, se va studia o mixtură asfaltică pentrul stratul de bază respectiv AB 31.5 pentru care se vor face încercări pentru trei rețete de mixturi asfaltice: mixtura asfaltică cu agregate minerale de carieră, mixtura asfaltică în care agregatele minerale vor fi înlocuite în proporție de 50 % cu zguri siderurgice și o mixtură asfaltică care va conține zguri siderurgice în proporție de 100%.

Încercările de laborator se vor face în cadrul Laboratorului de Drumuri din cadrul Facultății de Căi Ferate, Drumuri și Poduri, Universitatea Tehnică de Construcții București; rezultatele obținute vor fi detaliate sub forma de tabele și grafice, concluziile urmând a face aprecieri asupra performanțelor mixturilor asfaltice ecologice. Astfel, se vor stabili performanțele mixturilor asfaltice ecologice comparativ cu calitățile mixturilor asfaltice clasice, folosind următoarele încercări: determinarea densității aparente, a volumului de goluri, caracteristicilor Marshall și a modulului de rigiditate.

Open access