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Abstract: This paper presents the analysis of a steel connection. The analysis is performed using solid finite element and is compared to the experimental test performed in the laboratory. During the analysis special attention should be paid to the deformed shape revealed by the finite element analysis which also shows the distribution of stresses in the elements Key-Words: deformed shape, strengthen, strain gauge, boundary conditions, stresses. 1 Introduction Steel structures are used in different fields of civil engineering as: roofs, halls for production, exhibition halls, towers for radio and TV transmission, pipes, bridges, foot bridges, high-rise buildings. 52582
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Maintenance, repair and strengthening of existing steel structures are important activities for civil engineers. Many experts and consulting engineering firms are concerned with analysis of existing steel structures and the design and execution of repair and strengthening measures.
Steel structures are found in the world in many fields. A part of these steel structures are near the end of their service life. Processes of the deterioration are the result of steel corrosion, deficiency and inclusions in welding, cracks in the welding, buckling of elements and local deformations of elements, defects in micro structure of steel which have generated by different causes.
The deterioration processes, their causes and the counter-measures to remove, reduce or retard their actions, the methods to repair the damage that they caused, have been frequently analyzed for steel structures and steel bridges. Repair measures aim to re–establish a structure’s capability to accept the actions for which it was designed with sufficient safety and durability. Repair measures can usefully extend the service life for deteriorated steel structures. The need of repair may also arise due to errors in design, construction and maintenance, or due to accidental damage.
The usual aim of strengthening of existing steel structures is to allow for increased actions. The need to strengthen a structure may also impose higher functional requirements than those anticipated in the original design. Steel structure should be replaced only when it has been established that repair or strengthening measures are not technically feasible or economically reasonable. 2 Diagnostic of steel structures Actual procedure for diagnostic of steel structures is obtained by long experience in reconstruction and monitoring technical conditions, making diagnosing activities systematic, unifying methodology of diagnostics and informing on necessary equipment by instruments. It assumes gathering of continuous documentation about the structure as a background for proposing of a way for reconstruction.
Existing steel structures can be affected by different (various) deteriorations. Repair interventions can vary considerably in scope. Minor interventions should be undertaken during routine maintenance. Structures must be cleaned regularly of mud, weeds, debris, salt and other aggressive substances. The aggressive substances can initiate the progressive deterioration of steel structures. Drainage systems must be regularity cleaned and repaired. Repairing of small deterioration due to corrosion is common for steel structures. In these cases surface layer or paint cover is thin and steel has no protection.
When more complicated repairs are made to an area of major damage the process is called rehabilitation. Replacement of corroded bars is such a rehabilitation repair. The replacement bars are welded to bound existing bars. It should be noted that, during performing of this type of repair, the structure may need to be temporally supported. Cracks in the weld should be backfilled by additionally injected weld, which increases the durability of the structure. The repair can be controlled by ultrasonic devices and by coring. Before a decision to strengthen is made, the remaining capacity of structure should be determined. After technical expertise, alternative measures to increase the capacity of structure should be considered. Strengthening is usually the most serious intervention. When the live load is small in comparison with total actions, after strengthening additional live load can be supported. This is the case when the dead load is relatively high, as is typical for concrete structures. The safety condition of structure can be written as the effects of actions Sd should not exceed the corresponding design values of structure’s resistance Rd, dd RS ≤ (1) If the effects of actions on the structure were to exceed Sd, the structure will need to be strengthened accordingly. Strategies for strengthening existing structures can be classified into two groups.