Analytical Investigation on Progressive Collapse of 3-D Reinforced Concrete Frames Under High Temperature

Satyanarayanan²

2023

JSFE

Self Cite

PurposeThis study delineates the effect of cover thickness on reinforced concrete (RC) columns and beams under an elevated fire scenario. Columns and beams are important load-carrying structural members of buildings. Under all circumstances, the columns and beams were set to be free from damage to avoid structural failure. Under the high-temperature scenario, the RC element may fail because of the material deterioration that occurs owing to the thermal effect. This study attempts to determine the optimum cover thickness for beams and columns under extreme loads and fire conditions.Design/methodology/approachCover thicknesses of 30, 40, 45, 50, 60 and 70 mm for the columns and 10, 20, 25, 30, 35, 40, 50, 60 and 70 mm for the beams were adopted in this study. Both steady-state and transient-state conditions under thermomechanical analysis were performed using the finite element method to determine the heat transfer through the RC section and to determine the effect of thermal stresses.FindingsThe results show that the RC elements have a greater influence on the additional cover thickness at extreme temperatures and higher load ratios than at the service stages. The safe limits of the structural members were obtained under the combined effects of elevated temperatures and structural loads. The results also indicate that the compression members have a better thermal performance than the flexural members.Research limitations/implicationsNumerical investigations concerning the high-temperature behavior of structural elements are useful. The lack of an experimental setup encourages researchers to perform numerical investigations. In this study, the finite element models were validated with existing finite element models and experimental results.Practical implicationsThe obtained safe limit for the structural members could help to understand their resistance to fire in a real-time scenario. From the safe limit, a suitable design can be preferred while designing the structural members. This could probably save the structure from collapse.Originality/valueThere is a lack of both numerical and experimental research works. In numerical modeling, the research works found in the literature had difficulties in developing a numerical model that satisfactorily represents the structural members under fire, not being able to adequately understand their behavior at high temperatures. None of them considered the influence of the cover thickness under extreme fire and loading conditions. In this paper, this influence was evaluated and discussed.

Section: Methodsmentioning

confidence: 99%

Study on optimum concrete cover thickness in RC beam and columns under high temperature

Satyanarayanan²

2023

JSFE

Self Cite

“…24 The dimensions and the reinforcement details were assumed from the previous research. 19,26,27 The height of the frame lay at 3000 mm C/C, bay length and width (both X and Y-directions) measured 3000 mm C/C. The cross-sections of the beam measuring 300 × 300 mm, for column 400 × 300 mm, and a slab thickness of 150 mm were allocated.…”

Section: Finite Element Modellingmentioning

confidence: 99%

Effect of thermal expansion on three-dimensional reinforced concrete frames under high temperature

Proceedings of the Institution of Mechanical Engineers, Part C:

Satyanarayanan

2023

When exposed to high temperatures, reinforced concrete members undergo major changes in their properties which in turn affects their structural performance. Fire accidents in frame structures at local or global level may lead to collapse of structures. Structural fire has dire consequences like collapse of structures, colour changes, spalling of concrete and failure of essential elements. It is essential to study the conduct of reinforced concrete frame under thermal expansion in order to understand fire-induced collapse of concrete structures. This study observes how a three dimensional single-bay single-storey reinforced concrete frame is performed under thermo-mechanical analysis in ABAQUS (FEA). The paper aims to note the effect of slab and infill wall with respect to thermal expansion. The paper also discusses the main findings regarding the structural performance, structural leading conditions and structural stiffness of the reinforced concrete frame with slab and infill wall under thermal expansion. The results found that the infill frame has better stiffness and performs well under fire conditions.

“…Transient heat analysis was performed using the finite element software ABAQUS v6.14. The concrete section was modeled as a 3-D deformable element, and reinforcements were modeled as wire elements [46][47][48]. M30 grade of concrete with a damaged plasticity model and Fe500 grade of steel was taken for the finite element analysis [49].…”

Section: Biomimicked Geometriesmentioning

confidence: 99%

Experimental Investigation on the Heat Dissipation and Postfire Structural Performance of a Reinforced Concrete Column with Biomimicked Geometry

Satyanarayanan

2022

Fire

Cactus plants are prevalent in hot terrain locations. The spines in the cactus plants have an important function in preventing water evaporation. The strong pointed spines serve to distribute heat and prevent internal moisture loss owing to high heat. This paper addresses the biomimicking of a cactus plant to a reinforced concrete column. Columns are one of the most predominant elements in a structure and are responsible for maintaining the stability of the structure. Under the occurrences of fire, columns are the most affected, and the failure of the same could eventually steer to global collapse of the structure. In this study, various geometries were adopted based on the cactus plant, and the heat dissipation characteristics were studied. Finite element analysis was used to determine the optimal form based on the heat dissipation. The optimized shape was tested experimentally using a high-temperature localized heating element. Five column specimens were considered for experiments and named C (conventional nonheated column), C1 (conventional heated column), C2 (mimicked column), C3 (mimicked column with rebar in cone), and C4 (mimicked column with rebar in cone (quenching)). The heat-dissipating nature was observed, and the structural aspects were tested aftermath. The results reveal that the quenched specimen depicts better heat dissipation than the other specimens and eventually maintains the stability of the specimen throughout the height.