Computational Seismic Analysis of Dry-Stack Block Masonry Wall

In this research the computational modeling of Dry-Stack Block Masonry (DSM) walls subjected to cyclic monotonic loading testing is done. The analytical results were compared with experimental test results of the unreinforced and unconfined DSM cantilever walls subjected to lateral loading along with a constant axial load. ABAQUS has been used for Finite Element Modeling and analysis of the wall. Various material properties are defined for the wall in the software and modeled as a homogeneous material. The proposed numerical models had a good correlation with the experimental data. The test results discussion includes failure moods, load displacement curves, and stress/strain profile. Doi: 10.28991/cej-2021-03091668 Full Text: PDF

Seismic performance of circular columns from an existing RC building constructed in 1969

<p>Experimental work was performed using two circular columns taken from a reinforced concrete (RC) building constructed in 1969. The diameter of each column was 550 mm, and the average concrete strength obtained from the material tests was 11.3N/mm2. The columns were subjected to reversal loading with displacement control under constant axial load to evaluate the validity of the equations currently used for seismic evaluation. The damaged columns were repaired with epoxy resin injection to investigate the effect of repairs after earthquake events. The final collapse mechanism was the shear failure mode after flexural yielding. The maximum strength of the retrofitted columns was approximately 1.1 times that of the original columns. Three-dimensional nonlinear finite element analysis was conducted using ‘‘FINAL’’. The minimum principal stress of the circular columns with low-strength concrete was also examined.</p>

SEISMIC RETROFITTING OF REINFORCED CONCRETE SHEAR WALL USING CARBON FIBER REINFORCED POLYMERS (CFRP)

In this paper, the experimental results of a partially retrofitted non-compliant with code concrete shear wall using uni-directional carbon fibre reinforced polymer (CFRP) are introduced. The common deficiencies in the wall were insufficient reinforcement, un-confinement at boundary zone, the lake of in-plane stiffness, and ductility. The adopted retrofitting technique consists of the CFRP strips bonded to both wall face with mesh anchors installed in the wall panel and foundation to avoid debonding. The wall was tested before and after retrofitting under a constant axial load, and the displacement control lateral cyclic load was applied to the head beam level. The retrofitted wall showed satisfactory results in terms of drift and shear strength. The test results include the failure pattern, load-displacement behaviours, and deflected shape.

Strength Assessment of wedges in the Splice Zone of the Column

Splice zone is the lower base of cross-section and a part of column which is also known as lower hinge zone. It is the weaker part of the column so additional reinforcement should be required every time in case of regular pad footing. The presented research provides a way of strengthening the reinforced concrete column by applying wedges at the splice zone. The work is focused on the base cross-section of an isolated footing against deflection, stresses, bending moment, etc. By implementing the proposed work, we can avoid critical damage at the base cross-section of the column & it also provides more stability, thus make splice zone stronger than earlier to withstand the resistance. The two sets of footings are considered in which one is regular pad footing & the other is pad footing strengthened by applying wedges in the splice zone. Both of them are tested under constant axial load and moment. The static structural analysis is done by using finite element analysis in ANSYS 2016 software. Further we will observe the deflection, stresses & also the overall effects of applying wedges with multiple height & size at the splice zone of the column.

Confinement Effect of Reinforced Concrete Columns with Rectangular and Octagon-Shaped Spirals

Conventional spiral-type transverse reinforcement is effective at increasing the ductility and the maximum strength of reinforced concrete (RC) columns because it confines the inner concrete and the longitudinal reinforcement. However, when arranging crossties in a RC column with spirals, problems such as mutual interference with longitudinal reinforcement, overcrowding of reinforcement, and deterioration of constructability occur. Furthermore, the loosening of 90 and 130-degree standard hooks due to the lateral expansion of concrete causes buckling of the longitudinal reinforcement. This paper describes the ability of a newly developed spiral-type transverse reinforcement with various yield strengths to confine RC columns subjected to cyclic lateral load and constant axial load. The ductility capacity, energy dissipation, and effective stiffness of RC columns confined by the developed spiral-type transverse reinforcement were compared with those of RC columns confined by typical rectangular reinforcement. The experimental results showed that RC column specimens with the developed spiral-type transverse reinforcement have better performances in terms of ductility capacity and energy dissipation, even though the amount of reinforcement used for the specimens decreased by about 27% compared with the specimen with typical rectangular reinforcement.

A Numerical Investigation on Behavior of Column Base Plates with Different Configurations

Base plates are one of the most important types of connections in structures. Due to complicated steel-concrete interaction, simple assumptions of the stress distributions are usually employed for designing the connection. Simple assumptions of compressive stress distribution in concrete may accelerate the design procedure, but they may lead to overdesign results. In this study, six different types of base plates with different configuration were studied numerically using a commercial Finite Element (FE) software and the numerical model was calibrated with an experimental test. The models were subjected to a constant axial load and then a monotonic moment loading was applied. To investigate the effects of the axial load, several axial load level were considered for each configuration. As a result, moment-rotation curves of these base plates, including their rotational stiffness, in the absence and presence of the axial loads, were compared. Moreover, the stress distribution in the concrete was studied in the FE models. For all cases, the stress distribution in the concrete was semi-triangular with the maximum stress between the column flange and the edge of the plate. Based on numerical results, some concepts of simplified assumptions were proposed to find the stress distribution of the base plates. These assumptions are more realistic than current assumptions in structural specifications.

Performance of low rise concealed truss composite shear walls with external columns

A review on the previous studies shows that limited analytical or experimental studies on the low-rise concealed truss shear walls with external columns under monotonic loading have already been conducted. The combination of concealed truss was welded to I-shaped steel frame and flat steel support. Two different aspect ratio composite shear walls were tested under static monotonic loading, and the failure mode, bearing capacity, ductility and stiffness were explored. A finite element model was developed and used to simulate the composite shear walls under constant axial load and lateral loading. The comparison of test results confirmed that the finite element model could predict the behavior of composite shear walls accurately. Meanwhile, stress analyses of the specimens were studied to simulate stress distribution of reinforcement, and to analyze the steel of composite shear wall with external columns at different loading stages. Taken together, this study could be a basis for developing an accurately simplified model.