Safety and Stability of Structures with Semi-Rigid Connections of Members in Nodes

The structural design of a system in which connections of members are absolutely rigid or perfectly pinned has been thoroughly worked out in the existing literature. In real structures in general, and particularly in the precast ones, connection in joints may be partially rigid, which can have a significant impact on the change of stresses and strains in the structure, i.e. on the stability and security of the structure.Testing of engineering structures, i.e. conditions that must be met so that they remain in stable equilibrium position is of special importance. To determine the limit state of stability in use are experimental and analytical methods based on static, dynamic and energetic principles.This article presents the methods used to ensure technical safety and security, as well as additional safety conditioned by public and social reasons. The functional damage and fatigue are discussed, as well as the concept of the projected lifespan of the structure. Increased strength provides a higher degree of security, although many factors are variable

Static Design of Systems with Semi-Rigid Connections Based on Experimental Investigation of the Full Scale Structure

The paper presents the basic theory and corresponding equations for calculation of the static influences of the structures with semi-rigid connections in joints. The static design of system in which connections of members are absolutely rigid or perfectly pinned has been thoroughly worked out in the existing literature. In real structures in general, and particularly in the precast ones, connection in joints may be partially rigid, which can have a significant impact on the change of stresses and strains in the structure. In the world there are several procedures, with different approaches, to the structural design with semi-rigid connections, however, it is proved that they all lead to the same results. All of these approaches in addition to theoretical deal with experimental analysis of results. According to the approach that will be presented in this paper, typical prefabricated structures "Minoma" 1, "Minoma" 2, and "Minoma" 3 with span of 12m, 20m and 27m respectively, and the height of the column up to 9m, have been experimentally analyzed. A numerical example will be given and discussed, where bending moments due to a given load, as well as due to input force in the tensioner, have been calculated for defined levels of rigidity of connection using the deformation method. The obtained superimposed bending moment diagram will be analyzed too

SEIZMIČKA ANALIZA RAMOVA SA POLUKRUTIM VEZAMA U SKLADU SA EC8

Up to date research has pointed out that most of the structural connections of reinforced concrete (RC) frames, particularly precast ones, behave as semi-rigid. Therefore, it is of great importance to develop an analysis method which takes into account the connection rigidity. For that purpose matrix formulation of the deformation method is used in this paper, and the effect of rigidity of connections on the structure response is included by stiffness matrix for semi-rigidly connected member. The elements of this matrix are functions of the fixity factors at the ends of members. The proposed method is applied in seismic analysis of the precast RC frame structure of the existing industrial hall according to Eurocode 8 (EC8).Dosadašnja istraživanja su pokazala da se većina konstruktivnih veza armiranobetonskih (AB) ramova, posebno montažnih, ponaša kao delimično krute. Zbog toga je od velike važnosti razviti metod analize koji uzima u obzir krutost veze. U ovom radu je za to korišćena matrična formulacija metode deformacije, a uticaj krutosti veza na odziv konstrukcije obuhvaćen je matricom krutosti za delimično kruto vezani štap. Elementi ove matrice su funkcije stepena uklještenja na krajevima štapova. Predložena metoda je primenjena u seizmičkoj analizi prefabrikovane AB ramovske konstrukcije postojeće industrijske hale u skladu sa Evrokodom 8 (EC8)

Znaczenie stężenia NT-proBNP w określaniu rokowania i ocenie diagnostycznej u chorych z ostrymi zespołami wieńcowymi

Background and aim: N terminal-proB-type natriuretic peptide (NT-proBNP) is synthesised and secreted from the ventricularmyocardium. This marker is known to be elevated in patients with acute coronary syndromes (ACS). We evaluated NT-proBNP asa significant diagnostic marker and an important independent predictor of short-term mortality (one month) in patients with ACS.Methods: NT-proBNP and cardiac troponin I (cTI) were assessed in 134 consecutive patients (median age 66 years, 73% male)hospitalised for ACS in a cardiological university department. The patients were classified into ST-elevation ACS (STE-ACS, n = 74) and non-ST-elevation ACS (NSTE-ACS, n = 60) groups based on the ECG findings on admission. Patients with Killipclass ≥ II were excluded.Results: The serum level of NT-proBNP on admission was significantly higher (p < 0.0005), while there was no differencein cTI serum level in the NSTE-ACS patients compared to STE-ACS patients. There was a significant positive correlation betweenNT-proBNP and cTI in the NSTE-ACS (r = 0.338, p = 0.008) and STE-ACS (r = 0.441, p < 0.0005) patients. Therewas a significant difference in NT-proBNP (p < 0.0005) and cTI (p < 0.0005) serum level between ACS patients who diedwithin 30 days or who survived after one month. The increased NT-proBNP level is the strongest predictor of mortality in ACSpatients, also NT-proBNP cut-point level of 1,490 pg/mL is a significant independent predictor of mortality.Conclusions: We demonstrated the differences and the correlation in the secretion of NT-proBNP and cTI in patients withSTE-ACS vs. NSTE-ACS. Our results provide evidence that NT-proBNP is a significant diagnostic marker and an importantindependent predictor of short-term mortality in patients with ACS.Wstęp i cel: N-końcowy fragment propeptydu natriuretycznego typu B (NT-proBNP) jest syntetyzowany i wydzielany przezmiokardium komór serca. Wiadomo, że stężenie tego wskaźnika jest podwyższone u chorych z ostrymi zespołami wieńcowymi (ACS). Autorzy ocenili znaczenie stężenia NT-proBNP jako istotnego wskaźnika diagnostycznego i ważnego niezależnegoczynnika prognostycznego śmiertelności krótkoterminowej (w ciągu 1 miesiąca) u chorych z ACS.Metody: Oznaczono stężenia NT-proBNP i sercowej troponiny I (cTI) u 134 kolejnych chorych (mediana wieku 66 lat, 73%mężczyzn) hospitalizowanych z powodu ACS na oddziale kardiologicznym szpitala uniwersyteckiego. Pacjentów przydzielanodo grupy ACS z uniesieniem odcinka ST (STE-ACS, n = 74) lub do grupy ACS bez uniesienia odcinka ST (NSTE-ACS, n = 60)na podstawie EKG wykonanego przy przyjęciu. Chorych w klasie Killipa ≥ II wykluczono z badania.Wyniki: Stężenie NT-proBNP w surowicy przy przyjęciu do szpitala było istotnie wyższe (p < 0,0005) u pacjentów z NSTE--ACS niż u osób z STE-ACS, natomiast surowicze stężenia cTI były podobne w obu grupach. Stwierdzono istotną dodatniąkorelację między stężeniami NT-proBNP i cTI u chorych z NSTE-ACS (r = 0,338; p = 0,008) i u osób z STE-ACS (r = 0,441;p < 0,0005). Stężenia NT-proBNP (p < 0,0005) i cTI (p < 0,0005) w surowicy różniły się istotnie między chorymi z ACS,którzy zmarli w ciągu 30 dni, a pacjentami, którzy żyli dłużej niż miesiąc. Zwiększone stężenie NT-proBNP jest najsilniejszymczynnikiem prognostycznym zgonu u chorych z ACS. Ponadto stężenie NT-proBNP powyżej progowej wartości 1490 pg/mL jest istotnym niezależnym czynnikiem prognostycznym zgonu.Wnioski: Autorzy wykazali różnice w wydzielaniu NT-proBNP i cTI między chorymi ze STE-ACS i chorymi z NSTE-ACS orazkorelacje między tymi wskaźnikami. Uzyskane przez nich wyniki dowodzą, że NT-proBNP jest istotnym niezależnym wskaźnikiemdiagnostycznym i ważnym niezależnym czynnikiem prognostycznym śmiertelności krótkoterminowej u chorych z ACS