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  • Author: Jacek Selejdak x
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Abstract

In designing of reinforced concrete bridges are often used pre-cast of pre-tensioned or post-tensioned prestressed members. In professional practice, when designing bridge span pre-cast of pre-tensioned prestressed beams IG type, different axial beams spacing’s are used and they are joined by a reinforced concrete slab. The paper presents a comparative analysis of an influence of the axial spacing of IG type beams in the cross-section of the bridge, on the bridge span effort, using standards PN-85/S-10042 and PN-EN 1992-2:2010. The optimal axial spacing of pre-cast IG type beams is presented, while maintaining the standard conditions of ULS (Ultimate Limit State). Such a solution has a positive impact on the costs of the entire project, significantly lowering the global investment cost.

Abstract

A genetic algorithm is proposed to solve the weight minimization problem of spatial truss structures considering size and shape design variables. A very recently developed metaheuristic method called JAYA algorithm (JA) is implemented in this study for optimization of truss structures. The main feature of JA is that it does not require setting algorithm specific parameters. The algorithm has a very simple formulation where the basic idea is to approach the best solution and escape from the worst solution. Analyses of structures are performed by a finite element code in MATLAB. The effectiveness of JA algorithm is demonstrated through benchmark spatial truss 39-bar, and compare with results in references.

Abstract

The paper investigates and compares a selected issue of Serviceability Limit State (SLS) of simply supported reinforced concrete (RC) beams subjected to various values of flexural stresses. Characteristic crack widths of beams reinforced with various types of bars were calculated. Beams reinforced with Glass Fiber Reinforced Polymer (GFRP), Carbon Fiber Reinforced Polymer (CFRP) and Aramid Fiber Reinforced Polymer (AFRP) were examined. The computational analysis of beams reinforced with FRP bars was based on Italian guideline for the design (CNR-DT 203/2006) and in accordance with the EC2 (EN 1992-1-1:2004). Based on the conducted analysis, the effect of changing the service live load on the increase in crack width was presented.

Abstract

In this work on the basis of the developed and tested mathematical model, the numerical experiment is conducted in order to study in more detail the specifics of performance of concrete beams` with combined reinforcement. For this purpose nine series of reinforced concrete beams with different combination of steel bars (A400C, At800, A1000) and ribbon reinforcement (C275) were modeled. In the developed series two classes of concrete were used: C50/60, C35/45. The functions derived on the basis of mathematical modeling allow us to determine the recommended percentage of high-strength reinforcement of common reinforced concrete structures with single reinforcement. Therefore, the possibility is obtained to reduce the total structures` reinforcement percentage, increasing their deformability by the specified value without affecting the bearing capacity.

Abstract

In this article presented results of researching corrosion of steel bars in aggressive environment in time under loading. For researching were used special equipment. The experience and research works shown that steel bars in the crack cross-section area can be corrode. With increasing width of crack in re-bars and power of aggressive of environment increased the level of corrosion and decreased time of progress. The level of danger of corrosion in the crack in depend of specialty of steel bars. It is geometry parameters of steel bars and characteristic of corrosive behaviour. The general tendency of the influence of various defects on the strength of steels is widely studied experimentally and theoretically only for geometrically correct stress concentrators. For damages that are irregular in shape, such as corrosion ulcers, significantly less researching in each case must experiment to find their effect on the mechanical properties of steels. In this work the influence of simultaneous action of the aggressive environment and loading on strength of steel re-bars has been described.

Abstract

Formwork systems are necessarily used in the implementation of the RC (reinforced concrete) structures. Formworks are required regardless of whether a construction is monolithic or prefabricated and used to form the engineering and general structures or structural elements, such as abutments, supports and decks of the bridges, tanks and retaining walls, but also industrial and accommodation facilities etc. Ensuring the OHS (occupational health and safety) during transport, assembly and disassembly of formworks is a necessary condition for the execution of RC works in a safe and economical way. The paper presents the analysis of the safety requirements for formworks. Furthermore, the general requirements for the execution of the formwork structures were discussed. The most common organizational and technological mistakes and cased of neglects related to the operation of the formwork which lead to infringement of the OHS regulations were also identified.

Abstract

Remarkable place of reinforced concrete structures in construction field has been noted in wide number of recent researches. Subsequently, their degradation due to aggressive environment has become the topical problem nowadays. Therefore, the formulation of reliable technique for corroded element strength decrement is of great importance, and could be achieved only with the use of complex experimental and theoretical analysis. In this article an attempt is made to propose the mathematical approach to corrosive process modelling, taking into consideration the specifics of its development. According to thorough literature review on existing studies, main specifics of the process were indicated for further suppositions and assumptions formulation. Accordingly, the complex theoretical investigation with corresponding mathematical computations was conducted and results of analytical modelling were discussed. As the initial data for analytical modelling results of previously conducted experiments were used. Analysis of the obtained results shows rather high correspondence with the real conditions of structural element exploitation, taking into consideration material anisotropy and complexity of the corroded zone spread along the rebar cross-section. Proposed methodology for limit force decrease evaluation in general demonstrates reliable results and could be used for further evaluation of corrosion impacts on reinforced concrete elements bearing capacity.