Written on 19 août 2011.
Jorge de Brito, Technical University of Lisbon, Portugal Sonia Santos, BRISA, Portugal Fernando A. Branco, Technical University of Lisbon, Portugal Guidelines that relate to the design of concrete road and railway bridges are presented in this paper in order to guarantee the durability of bridges through easier inspection procedures -- the concept of inspectionability. The main characteristics that must be conferred on these structures, in order to facilitate access to all of their elements which are most prone to inspection/maintenance, are defined. In this context, access to the bridge elements and the equipment installed (bearings and joints) is paramount. The inspection auxiliary means are classified by traditional methods, by specific design detailing and by specific inspection equipment. Each of these groups is described and examples of their use are presented.
Written on 19 août 2011.
H. Otsuka, Graduate School of Civil Engineering, Kyushu University T. Wakasa, New Structural Engineering Ltd J. Ogata, Ingerosec Corporation W. Yabuki, Graduate School of Civil Engineering, Kyushu University D. Takemura, Graduate School of Civil Engineering, Kyushu University Following recent developments in prestressed concrete bridges, this paper examines extradosed and cable-stayed structures, particularly with regard to the evaluation of seismic performance and the economical considerations in a seismic region, and provides designers with guidance for choosing the most appropriate structure.
Written on 19 août 2011.
J. Moksnes, Honorary president fib, Norway M. Maage, Selmer Skanska, Norway This paper presents the costs and the associated added value and profit for a selection of concrete research and development (R&D) programmes in Norway during 1980-2000. The estimated figures give a ratio of added value, or return on investments, to costs equal to 19. This ratio is remarkably high and demonstrates that industry based R&D can be a profitable investment. The major beneficiaries of the added value are the clients of the industry and society, through reduced costs and better products and solutions.
Written on 19 août 2011.
No abstract.
Written on 19 août 2011.
Mounir Khalil El Debs, University of Sao Paulo at Sao Carlos, Brazil Aline da Silva Ramos Barboza, Federal University of Alagoas, Brazil Anamaria Malachini Miotto, Tuiuti University of Parana, Brazil Bearing pads are used in precast concrete connections to provide a more uniform distribution of contact stresses over the bearing areas and to allow relative movements between precast concrete elements, in order to prevent cracking at the connection area. This paper presents the study of an alternative material made with styrene-butadiene latex modified on Portland cement mortar, polymeric fibres, and, eventually, lightweight aggregate (vermiculite). The developed material showed a good compression strength and low elasticity modulus. These characteristics make it suitable for use as bearing pads in precast concrete connections, such as beam-to-column connections or wall-to-wall connections. The paper shows the main characteristics of this material and the application and tests on: (a) beam-to-column connections and (b) samples that reproduce a wall-to-wall connection.
Written on 19 août 2011.
Mounir Khalil El Debs, University of Sao Paulo at Sao Carlos, Brazil Aline da Silva Ramos Barboza, Federal University of Alagoas, Brazil Anamaria Malachini Miotto, Tuiuti University of Parana, Brazil Bearing pads are used in precast concrete connections to provide a more uniform distribution of contact stresses over the bearing areas and to allow relative movements between precast concrete elements, in order to prevent cracking at the connection area. This paper presents the study of an alternative material made with styrene-butadiene latex modified on Portland cement mortar, polymeric fibres, and, eventually, lightweight aggregate (vermiculite). The developed material showed a good compression strength and low elasticity modulus. These characteristics make it suitable for use as bearing pads in precast concrete connections, such as beam-to-column connections or wall-to-wall connections. The paper shows the main characteristics of this material and the application and tests on: (a) beam-to-column connections and (b) samples that reproduce a wall-to-wall connection.
Written on 19 août 2011.
Stefan L. Burtscher, University of Technology, Vienna Johann Kollegger, University of Technology, Vienna It is well known from literature that heterogeneous granular materials exhibit a size effect under tensile loading. Thus, the strength determined in experiments is not a material property. Some experiments have been performed regarding the size effect in tension whereas very few experiments have been performed in compression. However, compressive loading of concrete is more important because concrete is applied in structural systems to carry load in compression and not in tension. Furthermore, a compressive failure in a load-carrying member is more brittle, and in most cases more dangerous, than a tensile failure. Experimental investigations on the size effect are therefore needed. Experiments from literature on column-like specimens under compressive loading were performed up to a size range of 1:4. The size range of a series of geometrically equal specimens is given by the amplification factor of a characteristic dimension from the smallest to the largest specimen size. Obviously large size ranges are advantageous for experimental studies on size effect. The largest size range (1:16) of experiments on concrete under compressive loading carried out so far will be presented in this paper. This series was performed in one of the largest testing facilities available. A size effect on nominal strength was detected. The results are compared with the two most common size-effect laws.
Written on 19 août 2011.
Stefan L. Burtscher, University of Technology, Vienna Johann Kollegger, University of Technology, Vienna It is well known from literature that heterogeneous granular materials exhibit a size effect under tensile loading. Thus, the strength determined in experiments is not a material property. Some experiments have been performed regarding the size effect in tension whereas very few experiments have been performed in compression. However, compressive loading of concrete is more important because concrete is applied in structural systems to carry load in compression and not in tension. Furthermore, a compressive failure in a load-carrying member is more brittle, and in most cases more dangerous, than a tensile failure. Experimental investigations on the size effect are therefore needed. Experiments from literature on column-like specimens under compressive loading were performed up to a size range of 1:4. The size range of a series of geometrically equal specimens is given by the amplification factor of a characteristic dimension from the smallest to the largest specimen size. Obviously large size ranges are advantageous for experimental studies on size effect. The largest size range (1:16) of experiments on concrete under compressive loading carried out so far will be presented in this paper. This series was performed in one of the largest testing facilities available. A size effect on nominal strength was detected. The results are compared with the two most common size-effect laws.
Written on 19 août 2011.
L. F. A. Bernardo, Lecturer, University of Beira Interior, Covilhã, Portugal S. M. R. Lopes, Assistant Professor, FCTUC, University of Coimbra, Portugal This paper describes an experimental study on the flexural ductility of high-strength concrete beams. Nineteen isostatic beams, simply supported, were tested in the course of this work. Two symmetrical concentrated loads were applied to the beams at intervals of approximately one-third of the span. Ductility was studied by defining certain parameters, which have been termed ductility indexes. The main variables in this study are the compressive strength of the concrete and the longitudinal tensile reinforcement ratio. The results of the tests are examined and discussed, and some conclusions are drawn. The test results were compared with recommendations suggested by codes of practice and again conclusions are drawn.
Written on 19 août 2011.
Eva M. Eichinger, Vienna University of Technology, Institute for Structural Concrete, Vienna, Austria Thomas Petraschek, Vienna University of Technology, Institute for Structural Concrete, Vienna, Austria Johann Kollegger, Vienna University of Technology, Institute for Structural Concrete, Vienna, Austria In order to assess the influence of the bond action between wires, injection grout and the surrounding concrete on the ultimate load of damaged post-tensioning tendons more accurately, a series of tensile tests on tendons, which were built using old wires from a demolished bridge, was carried out. Wire breakage was included in the tendons at specified patterns. The results of the test series show that tendons with damaged or broken wires are able to carry a very high percentage of the ultimate load of an undamaged tendon. Even in situations where no confinement of stirrups in the surrounding concrete is present, the load-carrying capacity of tendons with broken wires is excellent. If the distance between the wire breakages is about half the anchorage length, the decrease in strength is about 20%. The results of these tests will be used to assess the tendon strength in comparable bridge structures where damage to the tendon is likely to be present.
Written on 19 août 2011.
Anders Ansell, Postdoctoral fellow, Department of Civil and Architectural Engineering, Royal Institute of Technology (KTH), Stockholm, Sweden Johan Silfwerbrand, Director, Swedish Cement and Concrete Research Institute (CBI), Stockholm, Sweden During early age, concrete is vulnerable to disturbance from vibrations of large magnitudes. Today, conservative vibration limits are used as standards, and guidelines provide little information. The literature cited in this study contains experiences and results from the construction and civil engineering field, in-situ testing, laboratory testing and computer modelling. On the basis of the reviewed literature, recommended maximum vibration levels for young and early-age concrete are given.
Written on 19 août 2011.
K. Diamoutene, Wroclaw University of Technology, Poland M. Kaminski, Wroclaw University of Technology, Poland The results of experimental research carried out on reinforced-concrete storage silos and of a numerical analysis of the temperature distribution in the silo wall are presented. Temperature fields in the structure were determined and the finite element method was applied to analyse the forces and moments generated by the thermal fields.
