BRJ – Volume 59, Number 1–2, 2011

Alexander Tesar, Ludovit Nasch:
Multi-functioning in laminated wood vs carbon fiber composite . . . . . . . . . . . . . . . . . . . . . . . . 1 – 24
P. Rathish Kumar:
A study on behaviour of high performance Ferrocement composite under biaxial state of stress.  25 –  38
A. M. Rashad:
Chloride ion permeability of plain and blended cement concretes . . . . . . . . . . . . . . . . . . . . . . .39 – 52
R. Sreekala, K. Muthumani, N. Gopalakrishnan, K. Sathish Kumar:
Modelling flexural behaviour of polymer modified concretes . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 – 66
R. K. Agrawal, M. S. Hora:
Linear interaction analysis of infilled building frame – soil system subjected to seismic loading . . . 67 – 86
Francisco J. Cantu, Mijia Yang:
Innovative beam-to-column joint design of moment resisting steel frames in seismic regions . . . . 87 – 98
Michal Krchňák, Milan Sokol:
Analysis of reinforced concrete cross sec¬tions using strip method . . . . . . . . . . . . . . . . . . . . . 99 – 110
Martin Križma, Jaromír Petržala:
Influence of time factor on strains and deflections of composite elements with content
of crushed plastic aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  . . . . . . . . . . 111 – 124

Abstracts

Multi-functioning in laminated wood vs carbon fiber composite
Alexander Tesar, Ludovit Nasch

Multi-functioning and multi-optimization in the analysis of laminated wood vs carbon fiber composites are treated in the present paper. Multi-functioning is one of the key features enabling multiple functions to be carried out in integrated laminated wood vs carbon fiber composites and structures with their hierarchical configuration. Theoretical, numerical and experimental assessment of the problem is presented. The structural application on attractive shell structure designed with multi-optimization approaches suggested is submitted.
Keywords: bionics, carbon fibers, identification, laminated wood, multi-functioning, multi-optimization, structural response, ultimate behavior

Astudy on behaviour of high performance ferrocement composite under biaxial state of stress
P. Rathishkumar

The closer distribution and uniform dispersion of continuous and relatively small diameter wire mesh reinforcement in ferrocement transform brittle mortar into a high performance material distinctly different from ordinary reinforced con¬crete. The versatility of high performance ferrocement composites enables numerous applications in construction of stressed skin surface structures like domes, folded plates and funicular shells. An element isolated from such structures is a two-di-mensional element subjected to two in-plane normal stresses and one in-plane shear stress. The results of 72 high performance ferrocement hollow cylindrical specimens tested 36 each under biaxial state of compression-tension and tension-compression are presented in this paper. The test results revealed that with the presence of ten¬sile/compressive stress in one direction there is a reduction in strength in the com¬pression/tension in the orthogonal direction. An interaction diagram is proposed to estimate the strength of ferrocement in biaxial compression-tension. The relation¬ship between octahedral normal and shear stress is also proposed.
Keywords: ferrocement, biaxial, compression-tension, tension-compression, interac¬tion curve, analytical model

Chloride ion permeability of plain and blended cement concretes
A. M. Rashad

This study presents the rapid chloride permeability test results on a variety of concrete samples with totally ordinary Portland cement, the OPC, replacement by 0 %, 5 %, 10 %, 15 % and 20 % of metakaolin, MK, or silica fume, SF, in separate replacement by cement weight. Rapid chloride diffusion tests were performed accord¬ing to ASTMC1202-09 at different ages. The results indicate that concretes contain¬ing metakaolin or silica fume improve the chloride penetration resistance compared to those of plain Portland cement concretes. Also, it has been concluded that the silica fume replacement is more effective in making the concrete less permeable than the metakaolin one. In addition, the permeability of concretes decreases when their ages increase.
Keywords: chloride diffusion, durability, metakaolin, silica fume

Modelling flexural behaviour of polymer modified concretes
R. Sreekala, K. Muthumani, N. Gopalakrishnan, K. Sathishkumar

Considerable research has been carried out in the recent years in the develop¬ment of models to simulate the inelastic responses of reinforced concrete elements. Availability of accurate models capable of representing the structural behaviour is the basic requirement to perform analysis and design of structural members. The enhancement of ductility and the post-peak behaviour are of special interest for the seismic design of structures. Modelling efforts have focused on the prediction of ul-timate strength in the case of earthquake design of structures. Design of flexural members requires flexural strength and ductility. Ductility analysis is seldom car¬ried out in normal design practice because no direct simple methods are available. Here an attempt is made to simulate the monotonic response of a natural rubber latex modified fibre concrete beam, which exhibits higher ductility. The results are compared with the response of normal strength concrete beam. An experimental in¬vestigation has been undertaken to understand the flexural behavior of the polymer-modified concrete. Polymer modified fibre concretes are found to be ideal for seismic application with its inherent structural characteristics. Analytical modelling of the beams was carried out in a user friendly finite element software to accurately pre¬dict the monotonic behavior of the beams which is considered to be the envelope of cyclic curve. The strains developed were found and are in good agreement with the theoretical results.
Keywords: ductility, concrete strain, flexural behavior, natural rubber latex modi¬fied concrete, finite element modeling

Linear interaction analysis of infilled building frame – soil system subjected to seismic loading
R. K. Agrawal, M. S. Hora

The building frame and its foundation along with the soil on which it rests, to¬gether constitute a complete structural system. In the conventional method of design, a structure is designed as an independent frame assuming unyielding supports and the interactive response of soil-foundation is disregarded. Such an analysis of frame-foundation-soil system may often lead to unrealistic and uneconomical solutions and sometimes, it may lead to failure. Also, the walls of building frames are usually considered as non-structural ele¬ments, therefore their interaction with the bounding frame is often ignored in the design. Now it is imperative to consider the seismic forces in the design of high rise buildings as occurrence of earthquakes has become frequent.
In this study, the building frame, infill, foundation and soil mass are considered to act as a single integral compatible structural unit subjected to lateral forces due to seismic effect. The physical modelling of the problem is achieved by finite element method using variety of isoparametric elements with different degrees of freedom. The un¬bounded domain of the soil mass has been discretized with coupled finite-infinite ele¬ments. The frame, the infill and the soil mass are considered to behave in act linear elastic manner. The static method according to Bureau of Indian Standard has been used to evaluate seismic forces.
Keywords: settable soil mass, differential settlements, coupled finite-infinite ele¬ments, interaction analysis, linear elastic analysis, seismic forces, infilled frame

Innovative beam-to-column joint design of moment resisting steel frames in seismic regions
Francisco J. Cantu, Mijia Yang

To attenuate the seismic response of stiff and low ductile steel frame configura¬tions, existing and standard beam-to-column joints have been reengineered. In this paper, several innovative joint designs are suggested to optimize the resistance of structures under dynamic forces. The target joints discussed in this paper are typical beam-to-column connections.
Keywords: beam-to-column connection, ductility, cyclic loading

Analysis of reinforced concrete cross sections using strip method
Michal Krchňák, Milan Sokol

An application of nonlinear analysis of the reinforced concrete cross-section under monotonic loading (bearing capacity) is presented in this paper. The analysis method used in the program is based on a strip method. A user friendly program was prepared in Delphi system (object Pascal). The main feature of this method is that the cross sec¬tion is discretized to a number of strips. These strips are analyzed separately using the stress-strain diagram. The paper describes implementation and algorithm of the method in our program and provides results of the analysis to a user as well. The user can view the results through the entire cross section analysis. The program has a user-friendly and intuitive interface which allows entering the characteristics of cross section easily, analyzing the problem and getting the graphical results as well.
Keywords: strip method, non-linear analysis, reinforced concrete, program, cross-section bearing capacity

Influence of time factor on strains and deflections of composite elements with content of crushed plastic aggregate
Martin Križma, Jaromír Petržala

Some results obtained within the frame of the EEAand Norwegian Finan¬cial Mechanisms – project No. SK 0081 – “Development of cement composites from electric and electronic plastic waste for application in building industry“– are pre¬sented in the paper. The project was solved in years 2009 – 2011. Its results contain the designs of cement composites with a content of crushed plastic aggregates, the solutions of some consecutive technological problems and typical mechanical and physical properties of the composites were determined. An influence of the time factor was taken into account at the determination of mechanical properties and also the cohesion of a dominant material with the concrete reinforcement was veri¬fied in the experimental program. The obtained results served as input data for the design of the modest structural elements – floor panels. The paper deals mainly with an influence of the time factor on strains and deflections of the composite ele¬ments with crushed plastic aggregates content. It is directly related to publications.
Keywords: cement composites, plastic aggregate, trial mixture, working character¬istics, floor panels, influence of time factor