Volume 3 Issue 2
Authors: Giuseppe Campione; Giovanni Minafò; Calogero Cucchiara
Abstract: Granite, marble and heavy stone columns have been used in the architects from all the ages to answer to both aesthetical and structural requirements in ancient churches and historical buildings. Such materials offer great visual impact and have mechanical properties that allow their use in construction and to obtain bright and slender structures. Marble is a very high strength but brittle material. It often occur that marble or granite columns of historical building are cracked along their height due to external actions and the risk of buckling occurs. Because this kind of failure is sudden and very brittle in stone and rocks, an immediate strengthening of the columns is needed. Among e temporary strengthening technique consisting in steel collaring with wood spars and steel wires is of interest. This technique was widely utilised by Firemen and Civil protection during the earthquakes occurred in Italy in the last years, but very few experimental and theoretical researches are available on this topic. In this paper the interest was on this technique and an experimental program based on compressive tests on monolithic and cracked marble columns with circular cross-section reinforced externally with wood spars and steel wires was carried out. A simple model based on the determination of the critical load of an elastic beam on elastic springs is able to take into account the steel collaring. The results obtained highlight that from a theoretical point of view, the presence of steel collaring in cracked column increases the critical load, ensuring monolithic behaviour, while from the practical point of the view the technique is very cheap and easy to apply in temporary strengthening of cracked columns.
Keywords: Marble Column; Steel Collars; Compression; Cracked Columns; Strengthening
Authors: Giuseppe Campione; Calogero Cucchiara; Alessia Monaco
Abstract: In the present paper, an analytical model is proposed that is able to determine the shear resistance of high strength reinforced concrete beams with longitudinal bars, in the presence of transverse stirrups. The model is based on the evaluation of the resistance contribution due to beam and arch actions. For the resistance contribution of the main bars in tension the residual bond adherence of steel bars and the crack spacing of R.C. beams are considered. The compressive strength of the compressed arch is also verified by taking into account of the biaxial state of stresses. The model was verified on the basis of experimental data available in the literature and it is able to include the following variables in the resistance provision: - geometrical percentage of steel bars; - depth-to-shear span ratio; - resistance of materials; - crack spacing; - tensile stress in main bars; - residual bond resistance;- size effects. Finally, some of the more recent analytical expressions able to predict the shear and the flexural resistance of concrete beams are mentioned and a comparison is made with experimental data.
Keywords: Shear-Moment Interaction; High-Strength Concrete; Shear Resistance; Flexural Resistance
Authors: Rou-Xuan Lee; Nyuk-Hien Wong
Abstract: Gross Building Coverage Ratio (GBCR) is one of the urban morphological variables that have an effect on microclimate within the urban canopy level (UCL). It is usually defined as the ratio between gross ground floor area covered by all buildings to a given site area. The impact of different morphological scenarios for GBCR variation on external ventilation levels within a typical high-rise Housing and Development Board (HDB) residential estate (or precinct) in Singapore is analyzed through a parametric study exercise. This is done by utilizing three-dimensional numerical simulations with the Reynolds-averaged Navier-Stokes (RANS) Realizable k-ε turbulence model (RLZ) from the commercial computational fluid dynamics (CFD) code Star-CCM+. Wind tunnel tests were carried out in order to validate the simulation software’s accuracy before put in use for the parametric study. Both the study results agree reasonably well here. External ventilation levels are quantified using the area-averaged Wind Velocity Ratio (VR) index, an indication of the average outdoor ventilation potential within an estate at a certain level. Two types of common HDB block types in Singapore are examined – point and slab blocks in three types of configurations: (i) random, (ii) group and (iii) courtyard. Measurements are taken at both the pedestrian and mid-levels under different wind orientations. From the study results, consistent trends can be observed as using the same GBCR value produces different results of average outdoor wind speed within an estate or precinct, under different block types, wind orientations and configurations.
Keywords: Gross Building Coverage Ratio (GBCR); Morphological Variables; Wind Velocity Ratio (VR); Outdoor Ventilation; High-Rise Residential Estate; Parametric Study; Computational Fluid Dynamics (CFD)
Authors: Sayed Hemeda
Abstract: The present integrated geophysical techniques were done to access the amount of hazards at Abu Serga Church in Cairo. The present work helps understanding the amount of hazards that Abu Serga Church suffers. Abu Serga Church is located within Cairo city and is considered one of the oldest Churches found in Egypt. The Church suffers moderate hazard but high risk in terms of seismic, geotechnical and environmental hazards. In the present research, the author tries to know how the most ancient church in Egypt should respeond in event of earthquakes. For this, besides the deterministic characterization of acceleration and seismic intensity, the author had conducted spectral studies of the soil and the structure itself with respect to seismic hazard. The aim of Geotechnical and geophysical field and laboratory tests is to define the physical, mechanical and dynamic properties of the building and the soil materials of the site where the church is founded. All these results together with the seismic hazard analysis will be used for the seismic analysis of the church response in the framework of the rehabilitation and strengthening works foreseen in a second stage. The author present herein the most important results of the field campaign and the definition of the design input motion.
Keywords: SHA; PGA; Microtremors; Natural Frequency; Abu Serga Church- Cairo; Geotechnical; Geophysical Campaign