STRUCTURAL AUDIT REPORT

PROJECT NAME                        : ANALYSIS  of EXISTING CNG PUMP  CANOPY                         

PROJECT LOCATION              : SONIPAT, HARYANA

STRUCTURAL CONSULTANTS

O.B Developers

(STRUCTURE AUDIT AGENCY)

F-14, Kalkaji main road

new delhi-110019

MOB: +91-9717924616

structureauditagency@gmail.com

WWW.STRUCTUREAUDITAGENCY.COM

1. INTRODUCTION

The structure is a CNG FILLING STATION CANOPY located at SONIPAT, HARYANA. In this report the design data sheet is attached along with various factors that are taken into account while analysis and design of the structure.

1.   VARIOUS CODE REFERED DURING ANALYSIS AND DESIGN

 (i)        IS 800            

(ii)        IS 875

1.   AUDIT WORK DONE AT SITE.

• As Built Drawings Preparation
• Thickness Reduction Test / Corrosion Impact Test

As per the NDT test we found that the members are suffering from corrosion which leads to reduction of 1.5mm thickness in structural members as per corrosion impact test.

1.   SUMMARY OF STABILITY ANALYSIS

• Over all the structure is found to be unsafe and retrofitting is needed
• Apart from retrofitting the rust from the existing members need to be removed and an anti-corrosion paint need to be applied over it.

ANALYSIS AND DESIGN DATA

FOR

CNG PUMP

2.1     Method of structural adequacy analysis and design parameters

The safety of a Canopy Structure against WIND will depend upon the architectural and structural configuration of the entire canopy, its location and exposure to wind. The methodology of the Structural analysis, design and detailing of the structural framework will be aimed to achieve stability in each aspect and its satisfactory performance under wind lading. Due consideration has been given to the aspect of fabrication and connection. Any weakness, if left in the structure, either in the design or in the fabrication will be fully reflected during the postulated design wind loading for the wind zone in the earthquake code IS: 875 Part III.

• Assumptions in static analysis

The basic assumptions in static analysis methodology are as follows:-

1. The behaviour of the structure is assumed to be perfectly linear and deformations are small
2. All joints are rigid
3. The members are subjected to axial, flexural and shear deformations
4. The force deformation relationship remains linear during the entire load regime.
5. Most critical LOAD COMBINATION has been assigned to assess it utility and retrofitting.

• Mathematical Modelling

The structure is idealized as a 3-D space frame model. The beams and columns are modelled as trussed structure. The columns are idealized to be fixed at the foundation level.

2.2     Loads for Superstructure and Sub structural elements:

1. Steel                                                               : Fe250
2. Density of Steel                                              : 78kN/m³
3. Self weight factor                                           : 1
4. Terrain Category                                             : 2
5. Wind Pressure on the purlins                          :1.788 kN/m

2.3     Materials properties data for static analysis                                           

• Steel Sections

            Conforming to IS 808 -1989

            Yield strength F_y                                 :           250 N/mm²     

            Static modulus of elasticity E_s            :           2 x 10⁵ N/mm²

2.4     Load Factors for Plastic Design of Steel Structures

Combination of Loads considered in analysis: The structural design has been carried out in accordance with the provisions of the codes IS: 800-2007 for plastic design of steel structures, whereas IS: 875(Part-III) has been used to calculate design wind pressure on purlins.

In the plastic design of steel structures, the following load combinations shall be accounted for:

1. 1.5 (DL+ WL) (for limit state of strength)
2. 1.0(DL+ WL) (for limit state of serviceability)

Fig. 2.1 Loading on the Canopy Model conforming Codal Provisions

Fig. 2.2 Load combination used in the analysis of the Canopy Model conforming to IS: 800-2007

• SUMMARY OF MEMBER adequacy analysis in Staad.Pro

• 

Blue members 1<utility ratio <1.2 Red Members utility ratio >1.2

MEMBER ADEQUACY FOR LARGE FILLING STATION

3.1.1     RESULTS AND DISCUSSION

S.No	Analysis Result as per IS 800, IS 875, IS 1893	Recommendations	Retrofitting Details
1.	ISMC 75 member provided as PURLIN have been found to have utility ratio above 1.2. Refer Fig. 3.1.3	All such member having utility ratio above 1.2 should be replaced by member having utility ratio less 1.2	ISMC 75 Purlin in the Cantilever portion of Canopy have been replaced by ISMC 125 Refer Fig. 3.1.5
212	ISA 75x75x8 provided in the Ridge Beam Truss along the Canopy have been found to have utility ratio above 1.2 .Refer Fig. 3.1.4	All such member having utility ratio above 1.2 should be replaced by member having utility ratio less 1.2	ISA 65x65x8 member size has been provided as diagonal bracing in the Ridge Beam Truss in addition to diagonal bracing present already Refer Fig. 3.1.6
3 3.	Deflection at various location were far beyond the Permissible deflection as provided in IS:800-2007  Refer  Fig 3.1.9	Retrofitting is recommended	In order to control the deflection at such location typical diagonal bracings have been provided :- ISA 110x110x8 have been provided in plan form at Cantilever Panels.           Refer Fig. 3.1.7At Panels other than Cantilever Panel ISA 75x75x8 have been provided in plan form. Refer  Fig 3.1.8
4.	Rotation at the junction of column and truss beam carrying purlins is severe. Refer  Fig 3.1.9	Retrofitting is recommended	ISMC 300 @300 C/C has been provided on the both sides to tie down the beams supporting purlins to column, eventually adding stiffness in the plane of rotation. Refer Fig.3.1.10
3.1.2   MEMBER UTILITY DETAILED REPRESENTATION Fig. 3.1.3 ISMC 75 member provided as PURLIN having utility ratio above 1.2     Fig. 3.1.4 ISA 75x75x8 provided in the Ridge Beam Truss along the Canopy having utility ratio above 1.2                            Fig 3.1.5 ISMC 75 Purlin in the Cantilever portion of Canopy have been replaced by ISMC 125                                                                                       Fig 3.1.6 ISA 65x65x8 member size has been provided as diagonal bracing in the Ridge Beam Truss in addition to diagonal bracing present already   3.1.3   RETROFTTING DETAILED REPRESENTATION            Fig 3.1.8 ISA 75x75x8 provided in plan form  Fig 3.1.7 ISA 110x110x8 provided in plan form        Fig 3.1.9 Deflection diagram of structure at severe Load Combinationmbefore retrofit Fig 3.1.10 ISMC 300 @300 C/C provided to control rotation   ISMC 300                          Fig 3.1.11 Deflection diagram of structure at severe Load Combination after retrofit     3.1.4    3-D RENDERED PERSPECTIVE OF THE MODEL   Fig 3..1.12  Rendered Perspective of Model of  Large Filling Station