Structural damage caused to RC buildings by tunnelling work

Nagli pomaci u tlu mogu dovesti do oštećenja armiranobetonskih građevina. Takvi pomaci mogu između ostalog biti uzrokovani gradnjom tunela, pa se utjecaj takve gradnje treba uzeti u obzir u postupku projektiranja građevina. U ovom se radu na primjeru postojeće bolničke zgrade analiziraju konstrukcijska oštećenja armiranobetonske građevine uslijed naglih pomaka tla. Kako bi se dobili što točniji podaci za potrebe analiza, primijenjen je multidisciplinarni pristup radi povezivanja raznih inženjerskih disciplina koje su sudjelovale u ovom istraživanju.Structural damages to RC (Reinforced concrete) buildings occasionally occur as a consequence of sudden ground movements. One of these is effect of tunnel excavation on the structures and the design process should be carried out by taking the effect into account. In this study, the structural damages caused by the impact of sudden movement emanating at the ground were investigated for a selected hospital building. Within the scope of this study, it was aimed to obtain the most accurate data by combining different engineering disciplines through a comprehensive approach

Effect of gallic acid addition on some mechanical properties of self-adhesive resin cements

Self-adhesive resin cements (RCs) activate matrix metalloproteinase (MMP) and cathepsin-related collagen degradation, and gallic acid (GA) inhibits the activity of both MMPs and cysteine cathepsins. The purpose of this study was to evaluate the setting time, biaxial flexural strength, and Vickers hardness of self-adhesive RCs after the addition of two different concentrations of GA. RelyX U200 (3M ESPE) and Panavia SA (Kuraray) were modified with 0.5 and 1 wt% GA. The setting time of five samples in each RC group was assessed using a thermocouple apparatus as described in the ISO 4049 test. Biaxial flexure strength was measured using a universal testing machine until failure. Vickers hardness was measured with three randomized indentations on the surface of each resin disc. RCs without GA were used as control. Data were analyzed using a one-way analysis of variance and Tukey’s HSD test (α = 0.05). The setting times ranged from 2.4 to 4.6 min for RelyX and from 4.9 to 6.0 min for Panavia. The biaxial flexure strength ranged from 76.5 to 109.7 MPa for RelyX and from 73.3 to 108.2 MPa for Panavia. Vickers hardness values ranged from 41.6 to 58.6 for RelyX and 27.2 to 33.6 for Panavia. The addition of 0.5 and 1 wt% GA to improve durability of resin-dentin bonds had no adverse effects on setting time, whereas the biaxial flexure strength and Vickers hardness values for the tested materials were significantly reduced.</p

Seismic load tests on exterior beam-column connections of existing RC structures

U radu su izneseni prijedlozi za poboljšanje svojstava spojeva greda-stup postojećih AB konstrukcija uslijed potresnog djelovanja. Analizirana je uporaba betona niske čvrstoće, glatkog armaturnog čelika bez spona u spojevima te je ispitano ponašanje spojeva u uvjetima pod cikličnim opterećenjem. U okviru eksperimentalnog istraživanja proizvedeno je i ispitano pet uzoraka s različitim rasporedom armature. Na temelju rezultata zaključeno je da su kritični parametri koji određuju svojstva postojećih konstrukcija, raspored spona u spojevima i upotreba kuka za sidrenje uzdužne armature koje su savijene pod kutom od najmanje 90°.Suggestions for improving seismic performance of beam-column connections of the existing RC structures are presented in this paper. The use of low-strength concrete with plain bars without stirrups in joints is analysed, and behaviour of joints in the aforementioned conditions under cyclic load is investigated. Five specimens with different reinforcement configurations were produced and tested in the experimental process. Based on results, it was concluded that critical parameters for the performance of existing structures are: stirrup arrangement in joints, and the use of at least 90-degree hooks in longitudinal reinforcement of beams

Determination of the effectivity of composite members on structural behavior through different combinations

The majority of the existing building stock has reinforced concrete load-bearing systems and relatively few buildings are steel-framed. On the other hand, composite frames are less preferred compared to these two types of structures. However, the effect of composite members (beams, columns, slabs) on the structural behavior of steel-framed buildings is still not fully known. Therefore, it is necessary to examine the structural behaviors of buildings with composite members. Therefore, the current paper examines the effectivity of composite members on structural systems. Three different building models with i. composite beams and composite col-umns, ii. steel beams and composite columns, and iii. composite beams and steel columns were numerically examined. The required profile types (size) for the structure models were determined by linear analysis considering the Eurocode 4 and AISC guides. Seismic performances of the structure models were then determined through nonlinear analyses. Finally, seismic performances of the three models were compared and the impact of composite members on the structural performance was determined. The results of this paper are believed to make a valuable contri-bution to the literature by determining the effect of composite members on the structural behavior of low-rise buildings through nonlinear analysis