Structural Behavior of steel frame Inﬁlled with Ferrocement Precast Panel S ubjected to Lateral Load

Background : When a severe earthquake ground motion hits the structure even if it doesn’t collapse it may undergoes inelastic deformations. Steel structure inﬁlled with precast panels becomes less eﬃcient when subjected to large lateral loads like strong wind and earthquake. Hence assessment of actual performance of steel frames provided with inﬁlls in the event of earthquake is essential. Methods : In the current study, a prototype model of steel frame size 4m x4m bay & 4m height with G+2 story is scaled down and subjected to lateral seismic load by conducting shake table test to assess modal frequencies, the same structure is modelled in Hypermesh and analyzed in Nastran, ETABS software. The results obtained are validated for a 16X16m bay of 4m height commercial complex of G+9 Multi-storeyed structure inﬁlled with Ferrocement Precast panels analysed in ETABS software for base shear, response spectrum and pushover analysis to assess the performance of the structure. Findings : The frequency from modal analysis was found to be 45.21 Hz, for G+2 storied model in ETABS, values obtained for frequency, base shear, performance point of the structure are in appreciable. Novelty : As per the traditional earthquake design methods, structures are designed for less forces than maximum considered for earthquake. The overall performance of the structure is found to be safe even inﬁlled with Ferrocement precast panels. Advantages : Ferrocement panels as inﬁlls has beneﬁt as they are slender from structural point of view. Compared with steel bare frame dynamic behavior of bare steel frame which is inﬁlled with Ferrocement precast panel subjected to lateral loads is high that helps in assessing the damage in the event of an earthquake in critical zone V.


Introduction
In recent days design and structural evaluation of the building systems subjected to lateral loads plays an important role.RCC and steel structures are constructed with various types of infills (1) .Precast Infilled panels are more often used for partitioning and covering building areas such as walls (2) .Steel frames infilled with precast panels are most widely used forms of multistory commercial construction the masonry walls are constructed after the basic frame work of beams, columns and slabs have gained sufficient strength.Various types of infills are used in which Ferrocement precast infills play a pivotal role these days in buildings as infilled wall (3) .The internal forces developed depend on the originating forces which depend on the lateral strength and deformability criteria of the constituent member elements (4) .Design forces depend upon the accuracy of the method employed in their analytical determination.Efforts are being made by researchers to develop more efficient structural system strong enough to resist against lateral loads.
In the current work the behavior of steel frame infilled with Ferrocement precast panel is studied on a G+2 story 4X4 m bay with story height 4m is analyses both experimentally and analytically (1) .An attempt has been made in this research towards analytical solution.Analysis is carried out using ETABS software for the G+9 storied 16x16m and 4m story height (1) .Steel frames with Ferrocement Precast panel infill employed to assess the seismic behavior of the structure (5) .The amount and location of infill panels greatly affect the natural frequency of the structural system the information of plastic hinges, Performance point and response of the structure can be analysed and the pretended results may provide the possibility of damages on the structures (4) .

Objectives
The basic objective of the study is to analyse the behaviour of steel structure with Ferrocement precast panel infilled all around the four sides of the steel structure under seismic loading and to experimentally compare the results by shake table test and Hypermesh model in Nastran and ETABS software's.
• To assess the suitability of the Beams, columns sections for a G+2 and G+9 storied building.
• To evaluate the performance of Steel bare frame infilled with Ferrocement precast panel under seismic loading for the scaled down prototype.• To calculate modal frequencies and time periods of the infilled framed steel structure.
• To assess the performance of the infilled structure using pushover analysis and response spectrum method.

Methodology
Several methods of seismic analysis were adopted the below figure shows the seismic method of analysis and it is analyzed using IS1893 2002 and 2016 IS codes .

Fig 1. Seismic analysis methods
A detailed literature review is carried out based on the objective of the study.A prototype frame of G+2 story is considered which is of 4x4m bay with a story height of 4m which is modelled in ETABS and a particular frame is scaled down to 1:1 scale to suitably to conduct shake table test to carry seismic analysis.The experimentation gives the modal frequencies for the suitable excitation.The same model is modelled in Hypermesh software and analysed in Nastran, ETABS software's.Results obtained are https://www.indjst.org/validated to the G+9 story 16X16m 4x4 bayed model with 4m height commercial building infilled with Ferrocement precast panels for all stories modelled in ETABS which is in earthquake zone V of medium soil (5).The seismic, response spectrum analysis, steel design check ,Base shear, story drift is carried out using ETABS software and conclusions are drawn on the basis of the behavior After the analysis is completed (1) , hinge status, Capacity spectrum curve and performance point is obtained.

Results and discussion
For experimental purpose a 3 floors 3D model is considered from the prototype structure and modelled separately in ETABS software and is scaled down to prepare the experimental model.The prototype is scaled down for a scale factor of 11 and steel sections are used for the model.And conducted for shake table test to assess the dynamic behavior of the structure when infilled with precast panels by placing accelerometers at respective floors as shown in the experimental setup.
The following table shows the results obtained in ETABS, Nastran and experimentation for G+2 storied model infilled by Ferrocement infilled panels.From the above Table 2 we can observe the first natural frequency as 42.09Hz for prototype and 47.47 from Nastran and 45.21 from ETABS analysis.Base shear is an estimate of the maximum expected lateral force that will occur due to seismic ground motion at the base of a structure.Analysis is carried out in ETABS on a 16x16m bay 4m height G+9 storied commercial building to assess the base shear, Pushover analysis, and Response spectrum analysis and performance point of the structure.
The following are the results obtained after analysing in ETABS software for G+9 storied infilled with Ferrocement precast panels framed model.
The base shear on the structure by seismic coefficient method is found to be 1916.77kNand by response spectrum method is found to be 1916.77kN along both X and Y directions by ETABS and manual calculations is 1907.6kNwhich are approximately nearer.Story shear reaction of bare frame infilled with Ferrocement precast panels by manual calculation of G+9 storied structure from the above graph we can observe that there is gradual rise in base shear values as the stories rise (6)

Hinge result at performance point
Figure 10 shows hinge status at the performance point in X and Y direction respectively.
Hinges formed in the structure are under the immediate occupancy state hence the structure is safe.Formation of plastic hinges at elements ends, Ferrocement precast panels are analysed for collapse that simulates the possibility of failure of connection between panels and steel frames.https://www.indjst.org/

Table 1 .
Structural details of prototype Particulars Value Particulars Value Number of stories ISMC400 + 12mm flats columns G+2 Number of stories ISWB 200 + 12mm flats Beams G+9 Each Storey height 4m Density for slab of RC panel 25kN/m 3 Number of bays in x -y scaled down model -2mm flat plate for entire beam and columns as I section fabrication Bricks were suitably scaled down.

Fig 4 .
Fig 4. Elevation of G+9 storied Steel bare frame infilled with Ferrocement precast panels on all sides.

Fig 5 .
Fig 5. Model shape for the natural frequency -displacement plot for modal frequencies of steel bare frame infilled with Ferrocement precast panels contour plot in Nastran software

Fig 6 .
Fig 6.Base reaction of bare frame infilled with Ferrocement precast panels manual calculation for Ferrocement precast panel infilled G+9 storied structure

Fig 9 .
Fig 9. Performance Point by ETABS of Ferrocement precast panel infilled G+9 storied structureFrom the above graph Performance point of the structure is calculated by ASCE 41-13 NSP method and FEMA 440 EL method the performance point for Spectrum Curve in X and Y directions respectively X-Direction = Performance point by ETABS is 19761.77kN , 44.81 mm Y-Direction = 21275.39kN , 42.469 mm(7).

Fig 10 .
Fig 10.Hinge status at performance point

Table 2 .
Modal Frequency details for Steel bare frame with Ferrocement precast infill panel