Abstract

The high speed rail which connects Córdoba city to Málaga city (both placed in the south of Spain) is currently under construction. Across the alignmentimportant structures are being constructed, such as the eight-kilometer tunnels of the Valle of Abdalajis where a tunnelling machine is being utilized. Atthe beginning of the works, the machine used had reached an international record. The paper deals with the general aspects of construction procedures,and problems related to the execution stage of high speed railways, a fact that makes this project of international interest

Abstract

This paper provides a bibliographic review regarding some physical and mechanical properties of polypropylene fibers and their use in concrete. The inclusion of fibrous reinforcements in concrete is growing up. However this association is only experimental and some theoretical concepts which could help us to understand the interaction mechanism fiber-matrix are passed over. Therefore the new materials development potential and its experimental results comprehension are restricted. This paper has two purposes: 1) to present the concepts regarding composite materials and 2) to present the polypropylene fibers effect in the concrete plastic properties. The conclusion is that the low elasticity modulus and the high elongation of polypropylene fibers reduce the bleeding and plastic shrinkage cracking in concrete, enhancing the surface properties and the durability of hardened concrete products. This review intends to connect some experimental results to theoretical concepts about composite materials.

Abstract

Cost estimating of construction projects in Mexico is generally based on the unit price system. Usually, construction firms commit a great deal of effort to such a task giving little importance to the planning aspects of the project. Nowadays, it appears that while evaluating bidders, owners pay attention primarily to economic issues of the bids and to the completion date of the project, minimizing the importance of the planning function. In this paper a tool to build up comprehensive plan and budget for contractors from a unit price estimate called “AsigRec” is discussed. The tool discussed here is software that allows to show all cost concepts of a cost estimate broken down into a tree diagram. The tree diagram displays graphically the most common levels used to integrate cost estimates in Mexico in a hierarchically fashion: 1) project, 2) item, 3) unit price and, 4) resources. Concurrently, the program allows creating the activity work break down structure (AWBS) in an easy and convenient way. Once the AWBS is defined, it is possible to arrange graphically the way in which the resources established in the original cost estimate will be allocated to new activities. This can be done with the tool by defined vectors named Allocation Operations (AO). Furthermore, the tool generates an Activity Resource Accounts Catalog (CCRA in Spanish). The resulting CCRA could be much simpler than the original cost estimate, allowing an easier project control based on the contractor’s criteria or priorities. The end goal of the tool is to provide the contractor with timely and meaningful information in order to improve his decision making.

Abstract

The present research analyzed the properties of concretes made with Portland Pozzolan cement and recycled aggregate obtained of demolished concretesto be propused as an alternative to a potential lack of aggregate natural in urban areas. An experimental program was carried out to study the effect of theamount and type of cement and recycled aggregate type on the concrete properties. The results showed decreases in all the physical properties of recycledaggregates. Considering fresh concrete, the concretes made with recycled aggregates presented slightly lower values with respect to the natural aggregateconcretes. Similarly in hardened concrete, concrete made with recycled aggregate presented diminished values of strength and modulus of elasticity. Ithighlights that the total substitution of natural aggregate by recycled concrete, implies smaller losses to those presented in concretes with partial substitutionof aggregate. It is estimated that the mortar adhered to the surface of the aggregate of recycled concrete is the critical factor that affects the properties ofthe recycled aggregate concrete.

Abstract

Bogotá, the capital of Colombia is located in a plateau on the Eastern mountain chain of the Andes, whose subsoil is conformed by a quaternary lacustrinedeposit conformed mainly by layers of clays and silts with sand interleaves. The soft clays, present in a considerable area of the urban and potentially urbanzone, must carefully be studied so that the foundations solutions guarantee the stability and functionality of civil works. The study of constitutive modelshas had great evolution in academic means but its practical application in the design has been limited, mainly by its little diffusion and the necessity touse a greater number of parameters than the required ones in the traditional methodologies. The fundamental concepts of the Modified Cam-Clay (CCM)model, the necessary parameters and the capacity of the model are analyzed to reproduce the experimental results of a set of triaxial tests on reconstitutedsamples of Bogotá. Finally, the conditions under which the model better simulates the behavior of soil (normally consolidated) are identified and on whichvariables more work has to be done to obtain a more complete constituent model (anisotropy).

Abstract

In this article, a description is made of each one of the modules that are part of the System of Administration of Bridges of Colombia (SIPUCOL). This system

was implemented in 1996 by Invias (Colombian Government’s Roads Administration). Also it is showed their utility and benefit, by means of the statistical

evaluation of bridge components in two (2) different inspection periods. Each component was studied to determine their main damages, causes, the requiered

studies and the types of recommended repairs. The major damages that have been detected are caused by structural insufficiency (lack of load capacity),

decomposition, corrosion, infiltration and undermining. The studies that have been more frequently executed are those of load capacity, seismic vulnerability

and undermining. To solve the problem, bridge maintenance and rehabilitation activities have been increased in the last years.