Analysis of G+5 Storeys Building With and Without Floating Column

In current period, several structures are being planned and built with structural complicatedness like building with floating columns on different floors and spaces. The buildings accompanying floating columns are extremely detrimental that is constructed in earthquake-prone regions. The current study analyses and compare the buildings with and without of floating column. The columns which are directly supported by a beam without any rigid base are known as floating columns. Various buildings have been constructed with floating columns in India. Typically, it is required to provide larger spacing between the columns to entertain the requirements of parking or reception lobbies. Some of the functional requirements of a building might be satisfied by providing the floating columns but the structural behaviour of the building changes abruptly. The beams that supported the floating columns require more flexure and shear demand than the surrounding beams. In addition, it leads to stiffness unevenness at a specific joint. Columns are the main structural elements that resist the lateral load in a rigid frame and have the importance in the performance of the building under earthquake load The storey’s stuffiness below the floating column is normally reduced. Therefore, an attempt has been made to analyse the performance of a G+5 storey building with and without floating columns and compare structural parameters such as horizontal displacement, storey drift and storey shear under seismic excitation using (ETABS) Software.

An experimental and analytical investigation of reinforced concrete beam-column joints strengthened with a range of CFRP schemes applied only to the beam

This paper investigates the experimental and analytical behaviour of beam-column joints that are subjected to a combination of torque, flexural and direct shear forces, where different Carbon Fibre Polymer (CFRP) strengthening wraps have been applied only to the beam. These wrapping schemes have previously been determined by the research community as an effective method of enhancing the torsional capacities of simply supported reinforced concrete beams. In this investigation, four 3/4-scale exterior beam-column joints were subjected to combined monotonic loading; three different beam wrapping schemes were employed to strengthen the beam region of the joint. The paper suggests a series of rational formulae, based on the space truss mechanism, which can be used to evaluate the joint shear demand of the beams wrapped in these various ways. Further, an iterative model, based on the average stress-strain method, has been introduced to predict joint strength. The proposed analytical approaches show good agreement with the experimental results. The experimental outcomes along with the adopted analytical methods reflect the consistent influence of the wrapping ratio, the interaction between the combined forces, the concrete strut capacity and the fibre orientation on the joint forces, the failure mode and the distortion levels. A large rise in the strut force resulting from shear stresses generated from this combination of forces is demonstrated and leads to a sudden-brittle failure. Likewise, increases in the beams’ main steel rebar strains are identified at the column face, again influenced by the load interactions and the wrapping systems used.

Displacement-based determination of BRBs in retrofitting an RC frame building

An RC frame school building was designed with lower fortification requirements than required. It collapsed in the 2008 Ms8.0 Wenchuan earthquake. This study evaluated the building’s deficiency and practiced a retrofit design based on traditional demand-capacity method but with a displacement-based (DB) procedure, in which target capacities were obtained from the equivalent single-degree-of-freedom (ESDOF) systems defined by target mode shapes of the MDOF system, and shear demands were assessed using an R- μ- T relationship to match different capacity levels. To make the DB procedure code-conforming, the retrofitting elements (BRBs) were simplified as bi-linear elements, with the two-phase parameters corresponding to the code’s two-stage requirements. Shear distribution to the MDOF building was also determined by displacement shapes. BRBs’ stiffness demands and sizes were from the difference of the required and available shear resistances. The effectiveness of the method was validated by time history analyses. Different earthquake level simulations showed that, the method realized the design goals but did not lead to over-retrofitting; the BRBs took most of the shear demand but would not induce other unexpected failures. So the method was suitable for retrofitting similar structures.

Shear Demands of Rock-Socketed Piles Subject to Cyclic Lateral Loading

The determination of internal pile reactions is critical to designing and assessing the structural performance of deep foundations. Internal shear and moment profiles strongly depend on lateral pile-soil interaction, which in turn depends on pile and soil stiffnesses as well as the stiffness contrast between soft and stiff strata, such as occurs at a soil/rock interface. At zones of strong geomaterial stiffness contrast, Winkler-spring-type analyses predict abrupt changes in the internal pile reactions for laterally-loaded foundation elements. In particular, the sudden deamplification of internal moments when transitioning from a soft to stiff layer is accompanied by amplification of pile shear. This “shear spike” can result in bulky transverse reinforcement designs for drilled shaft rock sockets that pose constructability challenges due to reinforcement congestion, increasing the risk of defective concrete on the outside of the cage. This paper presents an experimental research program of three large-scale, instrumented drilled shafts with simulated rock sockets constructed from concrete. Each shaft had a different transverse reinforcement design intended to bound the amplitude of the predicted amplified shear demand, with a particular em-phasis on performance of shafts with shear resistance less than the predicted demand and below the code minimum. Test results suggested that the shafts experienced a flexure-dominated failure irrespective of the transverse reinforcement detailing.

Irregularity Effects of Masonry Infills on Nonlinear Seismic Behaviour of RC Buildings

Despite extensive research studies, the seismic response of infilled reinforced concrete buildings remains an open problem due to both the complexity of the interaction between the infill and the frame and the large number of parameters involved. Thus, guidelines for both modelling and analysis are still lacking and the infill walls are normally treated as nonstructural components in seismic codes. However, it may be not conservative to neglect the influence of infills. In fact, the infill masonry walls may significantly affect the stiffness, strength, and energy dissipation capacity of RC buildings, even when they are regularly distributed. Recognizing this influence and its importance on the vulnerability of infilled frames, Eurocode 8 requires amplifying seismic action effects due to infills. In this paper, the effectiveness of the Eurocode 8 design provisions for infill irregularity in plan and/or elevation was investigated. To this aim, different in-plan layouts of infill walls were selected as marginal cases for which Eurocode 8 does not require amplification of the action effects due to the presence of infills, or the additional measures to counteract these effects are not mandatory. The seismic vulnerability of the infilled RC buildings was evaluated using nonlinear static and nonlinear dynamic analyses. Both cracking and crushing of masonry and stiffness and strength degradation were considered in the analysis. The effect of the layout of the masonry infills on the seismic response in terms of resistance and displacement was evaluated. Results show that in one of the case studies here examined, it is not conservative to neglect the influence of infill panels. In fact, structural failure due to torsion and soft-storey effects may occur even in cases where Eurocode 8 does not require the amplification of the action effects. Finally, the total shear demand on columns may be underestimated, even in cases where the code provisions for infills irregularity are not mandatory, and the additional shear demand in the columns induced by the masonry infill is very low.