Subject reviewDue to their slenderness, pedestrian bridges may vibrate significantly under pedestrian traffic. Many researches in the past few decades deal with the problem of predicting the vibration response induced by human activity reliably. Most of the codes in the field of footbridge design define certain pedestrian comfort criteria which have to be satisfied to fulfil the serviceability in relation to vibration. The main disadvantage of the current European codes (Eurocodes) is lack of defined dynamic models of pedestrian loads for the serviceability state verification in relation with vibration. In this paper a design procedure (with load models recommendation) for verification of the serviceability limit state related to vibration due to pedestrians is proposed. According to the proposed procedure the serviceability verification on a model of a reinforced concrete pedestrian bridge in the Maksimir Park in Zagreb is conducted. Keywords: pedestrian bridge; pedestrian load models; serviceability verification Dokaz graničnog stanja uporabljivosti pješačkih mostova pod pješačkim opterećenjemPregledni članak Pješački promet može izazvati značajne vibracije vitkih pješačkih mostova. U proteklih nekoliko desetljeća mnogi se znanstvenici bave problemom pouzdanog predviđanja dinamičkog odgovora (vibriranja) mostova izazvanog ljudskim kretanjem. Većina normi za projektiranje mostova definira određene kriterije koje je potrebno zadovoljiti da bi bilo dokazano granično stanje uporabljivosti vezano uz vibriranje. Osnovni nedostatak važećih europskih normi (Eurokodova) je nedostatak definiranih modela pješačkih opterećenja za koja se provodi dokaz graničnog stanja uporabljivosti vezanog uz vibriranje. U radu je predložen postupak proračuna pješačkih mostova (s preporučenim modelima pješačkog opterećenja) u području graničnog stanja vibracija uzrokovanih pješačkim opterećenjem. Koristeći predloženi postupak proveden je dokaz graničnog stanja uporabljivosti na modelu armiranobetonskog pješačkog mosta u parku Maksimir u Zagrebu.

Original scientific paper In the current European Code EN 1992-1-1 a truss model with variable inclination angle of concrete compressive struts with a quite wide range of inclination angle, from 21,8° to 45°, is intended for use for shear design of reinforced concrete beams. However, some researches and recommendations indicate special attention when choosing the lower bound of inclination angle of the concrete compressive struts, due to the reduced compressive strength of cracked concrete. This work reviews theoretical background and shear design methods of reinforced concrete beams. Relation of the shear resistance to crushing of the compressive struts as a function of their inclination angle has been investigated through a parametric study, where three different approaches have been used in order to limit stresses in the compressive struts. Based on the comparison of results from the analysis a recommendation for shear resistance calculation of reinforced concrete beams in dependence on concrete strength in compressive struts of the truss model is given. Keywords: compressive struts inclination angle; shear; truss model Nosivost armiranobetonskih greda na poprečne sile po kriteriju čvrstoće betonskih tlačnih štapovaIzvorni znanstveni članak U aktualnoj europskoj normi EN 1992-1-1 za dimenzioniranje armiranobetonskih greda na poprečne sile predviđa se uporaba rešetkastog modela sa slobodnim odabirom nagiba betonskih tlačnih ispunskih štapova u širokim granicama, to jest od 21,8° do 45° prema osi grede. Međutim, postoje istraživanja i prijedlozi koji upućuju na oprez kod odabira donje granice nagiba ispunskih tlačnih štapova s obzirom na umanjenje tlačne čvrstoće raspucanog betona u hrptu armiranobetonskih elemenata izloženih poprečnim silama. U radu je dan pregled teorijskih postavki i metoda proračuna armiranobetonskih elemenata na poprečne sile. Provedena je parametarska analiza nosivosti na poprečne sile pri drobljenju tlačnih štapova kao funkcije njihovog nagiba. Pri tom su korištena su tri različita pristupa za ograničenje naprezanja u tlačnim štapovima. Na temelju provedene analize i usporedbe rezultata u radu je dan prijedlog za određivanje nosivosti armiranobetonskih greda na poprečne sile po kriteriju čvrstoće betona ispunskih tlačnih štapova rešetkastog modela.

In this paper, the influence of sampling interval on reliability of damage detection and damage localization based on comparison of deflection influence lines and their derives (slope and curvature) for intact and damaged state is investigated. The numerical analysis is conducted on a simply supported beam with one damaged section for different sampling interval and different position of sampling points to damaged section.

A new structural damage estimation procedure using grey relation coefficient and curvature of displacement influence line in beams using sparse measurement is proposed in this paper. The method is based on static structural response which can be obtained using single sensor. Determination of damage location as well as determination of corre­sponding damage severity can be easily calculated with simple arithmetic operations, which is the main advantage of the proposed method. Conducted numerical simulation for different damage scenarios and various measurement sparseness and experimental validation confirm the effectiveness of proposed damage severity estimation procedure.

Original Scientific PaperAll dynamic pedestrian load models for serviceability control on pedestrian bridges which can be found in Eurocodes (EC)