International Journal of Civil Engineering
Volume:18 Issue: 9, Sep 2020

Many historical masonry towers belong to architectural heritage. Their preservation is still a critical issue in several countries. In fact, the experience of past earthquakes has shown that even earthquakes of moderate intensity can cause the collapse of these historical structures due to their slenderness together with irregularities, openings, leaning phenomena and adjacent lower buildings. The damage and changes suffered over the centuries, and the complex behaviour of the materials makes the performance of this type of structures more uncertain, and the seismic analysis and the remedial measures to achieve their protection a very complex task. This paper presents a complete study (from the on-site diagnostic investigations to the seismic assessment and non-invasive strengthening) of an ancient masonry tower in Torre Orsaia (Southern Italy). The paper, through the discussion of the case study, shows effective procedures to assess the seismic safety of masonry towers and plan interventions without too time- and cost-consuming processes. The results have established that the deep and wide cracks on the belfry are due to the loss of tension of the ancient tie-rods. The seismic safety of the tower has been carried out using three levels of analysis: LV1 (evaluation with simplified models), LV2 (analysis of local collapse mechanisms) and LV3 (global analysis). The analyses have shown that the critical mechanism is the simple overturning of the masonry piers of the belfry due to the ineffective tie-rods. The corresponding safety index in terms of peak ground acceleration is 0.305. To avoid this undesired mechanism and, at the same time, fully close the cracks, a strengthening intervention based on stainless steel reinforcing rings has been developed. This chaining system avoids the local mechanisms of the piers of the belfry and allows developing global mechanisms. After retrofit intervention, the seismic analysis has shown that the safety index increases to 0.716 for the LV2 analysis and 0.793 for the LV3 analysis.

Sixteen cold-formed steel channel columns with different combinations of edge and web stiffeners under axial compression forces up to failure were numerically investigated using finite element (FE) analysis program, ANSYS. The behavior characteristics; the ultimate load, stiffness, ductility and energy absorption have been selected and separately analyzed in relation to column parameters. To determine the single-performance optimization of each characteristic, Taguchi method was applied. The multi-performance optimization was also investigated using Taguchi method coupled with grey relational analysis to achieve the favorable column characteristics and to investigate the multiple-performance characteristics index of each column. The results indicated that for multi-response and a single response, the predicted results are confirmed and the errors in the predicted values using the Taguchi method with respect to the numerical values using ANSYS are acceptable and also they indicated that broken straight line web stiffener factor (WS3) was the highest contributing parameters for variation of the ultimate load of CFS columns.

In typical square tubular joints, the most common failure mode is local yielding or buckling of the chord at the brace/chord intersection. Thus, in the current paper, a collar-plate, as external reinforcement, is welded around the weld toe to increase the stiffness of the chord surface. Firstly, theoretical formulas, based on the yield line principle which is often used to examine thin-walled members suffering from local collapse mechanisms, for calculating the capacities of the collar-plate-reinforced square tubular T-joints under axial compression and in-plane bending are deduced. Then, experimental tests and finite element (FE) simulations are carried out on square tubular T-joints reinforced with collar-plates. The experimental results showed an improvement in the bearing capacity of SHS joints reinforced with collar-plate by 78 and 89% compared with the corresponding un-reinforcement joints. The FE results, as well, proved that using the collar-plate reinforcement is an efficient method to improve the static strength of a square tubular T-joint under either axial compression or in-plane bending. Finally, through the comparison between the FE results and the theoretical formulas, the validation range of the formulas for predicting the strengths of the collar-plate-reinforced square tubular T-joints is specified. For the joints under axial pressure, the validation range of the proposed formula is 0.45 ≤ βc ≤ 0.8, 2γ  ≥ 20 and τc ≥ 1.5, while for the joints under in-plane bending is βc ≤ 0.8, 15 ≤  2γ  ≤ 30 and τc ≥ 1.50.

Quantitative and parametric investigations of the flexural robustness of seismically designed reinforced concrete (RC) building frames under column loss were conducted in this study. A robustness index expressed as the product of the seismic coefficient and the resistance ratio was proposed for the evaluation. Under column-loss conditions, the building frame may not sustain the effective seismic weight using the flexural mechanism as the robustness index is smaller than one. Analytical formulae of the robustness index for the three-dimensional frame model were derived using the energy method and plastic analysis technique. Seven moment-resisting RC building frames with different structural parameters were designed. Nonlinear static analyses were performed to investigate the effects of the span length, number of stories, and seismic coefficient on the robustness index. The results indicated that among these parameters, the span length was the most critical factor. The robustness index decreased with an increase in the span length. For the five-story building frames, it decreased to smaller than 1.0 when the span length increased from 4 to 6 m or larger. Nevertheless, the robustness index was approximately directly proportional to the seismic coefficient and number of stories. It was doubled as the seismic coefficient or number of stories increased from 0.1 to 0.2 or five to ten, respectively. Numerical verification confirmed that the proposed analytical formulae can provide conservative robustness evaluation for seismically designed RC building frames.

The influence of bond-slip behavior, shown by pinched hysteretic curves in the inelastic response of degrading structural systems, is investigated in this paper. Inelastic response spectra are calculated and compared for deteriorating structures with and without manifestation of bond-slip. The response spectra are generated by using a smooth hysteretic model with distinct degrading parameters that are calibrated to the generic inelastic envelopes. In addition to the ductility demands, degraded residual strengths and stiffness of structural systems after an earthquake are considered as the relevant response measures. These measures can serve as design parameters for structures that should remain functional after an extreme event. Based on the response spectra analyses, it is found that nonlinear responses of degrading structural systems with bond-slip develop larger ductility demands and greater loss of strength and stiffness than the responses without bond-slip. Numerical results show that, ductility demand is increased up to 25–100% with consideration of slip in the model, as well as residual strength and stiffness decreased up to almost half.

Natural pozzolanas should be evaluated in terms of sustainability as well as their contribution to concrete durability. Therefore, the use of such materials in the production of cement as well as concrete industry has been gaining importance recently. In this study, the pozzolanic activities of ground trachyte and rhyolite, known as volcanic tuffs, were investigated in accordance with TS 25 standard. Pozzolanic properties of such materials, along with their pozzolanic activity indices, are investigated comparatively by the Frattini method, strength activity index, X-ray diffraction and thermogravimetric analysis. The morphologies of ground trachyte and rhyolite were also studied using SEM analysis. Based on the results obtained, the mortar samples containing blast furnace slag (BFS), fly ash (FA), trachyte and rhyolite were met the acceptable pozzolanic activity index at the end of 28 days with values of 90, 87, 89, 87, respectively. On the other hand at the end of 90 days, while the mortar samples containing BFS, FA and trachyte were met the acceptable pozzolanic activity index, that of containing rhyolite did not meet the acceptable pozzolanic activity index, with values of 93, 85, 87, 80, respectively. The pozzolanic activity index of the rhyolite was found to be quite close to that of the FA; however, the trachyte had a pozzolanic activity index close to the BFS. Comparisons of the methods implemented in the analyses were also conducted. According to the statistical evaluation of the test methods, it has been found that the relationships obtained using the direct methods as well as the indirect methods independently are highly correlated. Overall, it can be concluded that the ground trachyte may be utilized as a pozzolanas in the cement industry; however, the ground rhyolite does not meet some limits prescribed by the related standard.

The benefit of using a weir is that it allows flowrates to be measured and controlled in open channels and streams. The objectives of this research are: (1) to specify a suitable crest depth position as a control section for estimating the flowrate above a curved crump weir at ten different longitudinal slopes and (2) to compare the proposed flowrate versus measured and computational fluid dynamics (CFD)-simulated flowrates. In this research, the crest point of the curved crump weir was considered to be a control section, relating to the critical depth as a function of the crest depth. Experiments with eight different laboratory flowrates of flume were proposed at ten different channel slopes ranging from 0.0 to 2.5%. Statistical analysis of linear regression indicated that the relationship between critical depth and crest depth is 0.913 on average. Based on this finding, a new equation was derived to predict the discharge over the crump weir, which indicated an excellent match compared to the practical and CFD-simulated results (a maximum differences of 4% based on several standard error indexes and a one-way ANOVA). The CFD technique was performed to simulate the velocity and flow pattern of the curve crump weir based on the volume of fraction method. Six selective sections were tested along the flume with a total length of 1.36 m for a case study of 0.912 m3/h flowrate and zero bed slope to investigate and describe the water surface profile. The statistical analysis indicated insignificant differences between the measured and simulated water surface profiles, with a maximum difference of less than 15% observed at the section located at 0.69 m, while the average difference was 4.86% for all sections.

Asphalt binder is a complex viscoelastic material. It implies that based on temperature and loading, its behaviour changes from a viscous material to an elastic material. Modification and ageing further add to this complexity. Over the years, a number of studies have examined all the aspects of polymer-modified binders (PMB), but there is still work needed to correlate the viscoelastic behaviour of the PMBs to their morphological behaviour. So, in the present study PMBs are prepared by modifying VG-10 base binder with the help of styrene butadiene styrene and ethylene vinyl acetate. Binders were aged using rolling thin-film oven test and pressure ageing vessel. Viscoelastic and morphological evaluation of binders was carried out by using dynamic shear rheometer and scanning electron microscopy (SEM), respectively. The test results showed that polymer modification enhances the thermorheological complexity of the base binders, while ageing does not affect it. Linear viscoelastic limits of the binders were found to be decreasing after ageing and modification. Ageing degrades the polymer network so after ageing PMBs were found to be behaving similar to base binder. The SEM results support these results.