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 Page 1


                                                        
 
 
GANTRY GIRDER 
 
Introduction 
 
In manufacturing plant it is essential to provide overhead travelling crane to transport heavy 
components of machines from one place to another. The movement of the load is of three 
dimensional nature. The crane is required to lift heavy mass vertically and horizontally, also 
the crane with load is required to move along the length of the shed. The cranes are either 
hand-or-electrically operated. The crane moves on rails which are at its ends. The rails are 
provided on a girder known as a gantry girder. The gantry girder spans over gantry columns. 
If capacity of crane is moderate, the gantry girders rest on brackets connected to roof column 
of industrial shed. 
 
Characteristics 
 
? Design of gantry girder is a classic example of laterally unsupported beam 
? It is subjected to in addition to vertical loads and horizontal loads along and perpendicular 
to its axis 
? Loads are of dynamic nature and produce vibration 
? Compression flange requires critical attention  
 
Codal Provisions 
 
? Partial safety factor for both dead load and crane load is 1.5 (Table 4, p.29) 
? Partial safety factor for serviceability for both dead load and crane load is 1 (Table 4, 
p.29) 
? Deflection Limits (Table 6, p.31) 
Category Maximum Deflection 
Vertical deflection ? Manually Operated – Span/500 
? Electric operated- Span/750 upto 50t capacity 
? Electric operated- Span/1000 over 50t capacity 
Lateral deflection Relative displacement between rails supporting 10 mm or crane- span/400 
 
Other Considerations 
 
? Diaphragm must be provided to connect compression flange to roof column of industrial 
building to ensure restraint against lateral torsional buckling at ends. 
? Span is considered to be simply supported to avoid bumping effect. 
 
Design Steps 
 
The design of the gantry girder subjected to lateral loads is a trial-and-error procedure. It is 
assumed that the lateral load is resisted entirely by the compression top flange of the beam 
and any reinforcing plates, channels, etc. and that the vertical load is resisted by the combined 
beam. Various steps involved in the design are as follows: 
 
1. Maximum wheel load is to be calculated. The wheel load is maximum when the trolley is 
closest to the gantry girder. This load is to be correspondingly increased for the impact. 
 
Page 2


                                                        
 
 
GANTRY GIRDER 
 
Introduction 
 
In manufacturing plant it is essential to provide overhead travelling crane to transport heavy 
components of machines from one place to another. The movement of the load is of three 
dimensional nature. The crane is required to lift heavy mass vertically and horizontally, also 
the crane with load is required to move along the length of the shed. The cranes are either 
hand-or-electrically operated. The crane moves on rails which are at its ends. The rails are 
provided on a girder known as a gantry girder. The gantry girder spans over gantry columns. 
If capacity of crane is moderate, the gantry girders rest on brackets connected to roof column 
of industrial shed. 
 
Characteristics 
 
? Design of gantry girder is a classic example of laterally unsupported beam 
? It is subjected to in addition to vertical loads and horizontal loads along and perpendicular 
to its axis 
? Loads are of dynamic nature and produce vibration 
? Compression flange requires critical attention  
 
Codal Provisions 
 
? Partial safety factor for both dead load and crane load is 1.5 (Table 4, p.29) 
? Partial safety factor for serviceability for both dead load and crane load is 1 (Table 4, 
p.29) 
? Deflection Limits (Table 6, p.31) 
Category Maximum Deflection 
Vertical deflection ? Manually Operated – Span/500 
? Electric operated- Span/750 upto 50t capacity 
? Electric operated- Span/1000 over 50t capacity 
Lateral deflection Relative displacement between rails supporting 10 mm or crane- span/400 
 
Other Considerations 
 
? Diaphragm must be provided to connect compression flange to roof column of industrial 
building to ensure restraint against lateral torsional buckling at ends. 
? Span is considered to be simply supported to avoid bumping effect. 
 
Design Steps 
 
The design of the gantry girder subjected to lateral loads is a trial-and-error procedure. It is 
assumed that the lateral load is resisted entirely by the compression top flange of the beam 
and any reinforcing plates, channels, etc. and that the vertical load is resisted by the combined 
beam. Various steps involved in the design are as follows: 
 
1. Maximum wheel load is to be calculated. The wheel load is maximum when the trolley is 
closest to the gantry girder. This load is to be correspondingly increased for the impact. 
 
                                                        
 
 
2.  Maximum bending moment in the gantry girder due to vertical loads is to be computed. 
This consists of the bending moment due to maximum wheel loads (including impact) and 
the bending moment due to dead load of the gantry and rails. The bending moment due to 
dead loads is maximum at the centre of the girder, whereas the bending moment due to 
wheel load is maximum below one of the wheels. For simplicity, the maximum bending 
moment due to dead load is directly added to the maximum wheel load moment. 
 
3. Maximum shear force is to be calculated. This consists of the shear force due to wheel 
loads and dead loads from the gantry girder and rails.  
? Generally an I-section with a channel section is chosen, though an I-section with a plate 
at the top flange may be used for light cranes.  
? When the gantry is not laterally supported, the equation to be used to select a trial 
section is as follows: 
Zp = Mu/fy ...............................................................................................(1) 
Zp (trial) = kZp, (k = 1.4-1.5) ....................................................................(2) 
? Generally, the economic depth of a gantry girder is about (1/12)th of the span. The 
width of the flange is chosen to be between (1/40) and (1/30)th of the span to prevent 
the excessive lateral deflection. 
 
4. The plastic section modulus of the assumed combined section is found out by considering 
a neutral axis which divides the area in two equal parts, at distance y to the area centroid 
from the neutral axis. Thus, 
Mp = 2fyA/2y = Ayfy,           where Ay = plastic modulus Zp ............................(3) 
 
5. When lateral support is provided at the compression (top) flange, the chosen section 
should be checked for the moment capacity of the whole section (clause 8.2.1.2 of IS800): 
Mdz = BbZpfy/? mo = 1.2Zefy/?mo ....................................................................(4) 
Above value should be greater than applied bending moment. The top flange should be 
checked for bending in both the axes using the following interaction equation: 
(My/Mndy) + (Mz/Mndz)  = 1 ........................................................................(5) 
 
6. If the top (compression) flange is not supported, the buckling resistance is to be checked in 
the same way as in step 4 but replacing fy with the design bending compressive stress fbd 
(calculated using Section 8.2.2 of the code). 
 
7. At points of concentrated load (wheel load or reactions) the web of the girder must be 
checked for local buckling and, if necessary, load carrying stiffeners must be introduced to 
prevent local buckling of the web. 
 
8. At points of concentrated load (wheel load or reactions) the web of the girder must be 
checked for local crushing. If necessary, bearing stiffeners should be introduced to prevent 
local crushing of the web. 
 
9. The maximum deflection under working loads has to be checked. 
 
10. The gantry girder is subjected to fatigue effects due to moving loads. Normally, light-and 
medium-duty cranes are not checked for fatigue effects if the number of cycles of load is 
less than 5 x 10
6
. For heavy-duty cranes, the gantry girders are to be checked for fatigue 
loads (see IS 1024 and IS 807). Refer section 13 of the code for design provisions for 
fatigue effects. The fatigue strength is to be checked at working loads. 
Page 3


                                                        
 
 
GANTRY GIRDER 
 
Introduction 
 
In manufacturing plant it is essential to provide overhead travelling crane to transport heavy 
components of machines from one place to another. The movement of the load is of three 
dimensional nature. The crane is required to lift heavy mass vertically and horizontally, also 
the crane with load is required to move along the length of the shed. The cranes are either 
hand-or-electrically operated. The crane moves on rails which are at its ends. The rails are 
provided on a girder known as a gantry girder. The gantry girder spans over gantry columns. 
If capacity of crane is moderate, the gantry girders rest on brackets connected to roof column 
of industrial shed. 
 
Characteristics 
 
? Design of gantry girder is a classic example of laterally unsupported beam 
? It is subjected to in addition to vertical loads and horizontal loads along and perpendicular 
to its axis 
? Loads are of dynamic nature and produce vibration 
? Compression flange requires critical attention  
 
Codal Provisions 
 
? Partial safety factor for both dead load and crane load is 1.5 (Table 4, p.29) 
? Partial safety factor for serviceability for both dead load and crane load is 1 (Table 4, 
p.29) 
? Deflection Limits (Table 6, p.31) 
Category Maximum Deflection 
Vertical deflection ? Manually Operated – Span/500 
? Electric operated- Span/750 upto 50t capacity 
? Electric operated- Span/1000 over 50t capacity 
Lateral deflection Relative displacement between rails supporting 10 mm or crane- span/400 
 
Other Considerations 
 
? Diaphragm must be provided to connect compression flange to roof column of industrial 
building to ensure restraint against lateral torsional buckling at ends. 
? Span is considered to be simply supported to avoid bumping effect. 
 
Design Steps 
 
The design of the gantry girder subjected to lateral loads is a trial-and-error procedure. It is 
assumed that the lateral load is resisted entirely by the compression top flange of the beam 
and any reinforcing plates, channels, etc. and that the vertical load is resisted by the combined 
beam. Various steps involved in the design are as follows: 
 
1. Maximum wheel load is to be calculated. The wheel load is maximum when the trolley is 
closest to the gantry girder. This load is to be correspondingly increased for the impact. 
 
                                                        
 
 
2.  Maximum bending moment in the gantry girder due to vertical loads is to be computed. 
This consists of the bending moment due to maximum wheel loads (including impact) and 
the bending moment due to dead load of the gantry and rails. The bending moment due to 
dead loads is maximum at the centre of the girder, whereas the bending moment due to 
wheel load is maximum below one of the wheels. For simplicity, the maximum bending 
moment due to dead load is directly added to the maximum wheel load moment. 
 
3. Maximum shear force is to be calculated. This consists of the shear force due to wheel 
loads and dead loads from the gantry girder and rails.  
? Generally an I-section with a channel section is chosen, though an I-section with a plate 
at the top flange may be used for light cranes.  
? When the gantry is not laterally supported, the equation to be used to select a trial 
section is as follows: 
Zp = Mu/fy ...............................................................................................(1) 
Zp (trial) = kZp, (k = 1.4-1.5) ....................................................................(2) 
? Generally, the economic depth of a gantry girder is about (1/12)th of the span. The 
width of the flange is chosen to be between (1/40) and (1/30)th of the span to prevent 
the excessive lateral deflection. 
 
4. The plastic section modulus of the assumed combined section is found out by considering 
a neutral axis which divides the area in two equal parts, at distance y to the area centroid 
from the neutral axis. Thus, 
Mp = 2fyA/2y = Ayfy,           where Ay = plastic modulus Zp ............................(3) 
 
5. When lateral support is provided at the compression (top) flange, the chosen section 
should be checked for the moment capacity of the whole section (clause 8.2.1.2 of IS800): 
Mdz = BbZpfy/? mo = 1.2Zefy/?mo ....................................................................(4) 
Above value should be greater than applied bending moment. The top flange should be 
checked for bending in both the axes using the following interaction equation: 
(My/Mndy) + (Mz/Mndz)  = 1 ........................................................................(5) 
 
6. If the top (compression) flange is not supported, the buckling resistance is to be checked in 
the same way as in step 4 but replacing fy with the design bending compressive stress fbd 
(calculated using Section 8.2.2 of the code). 
 
7. At points of concentrated load (wheel load or reactions) the web of the girder must be 
checked for local buckling and, if necessary, load carrying stiffeners must be introduced to 
prevent local buckling of the web. 
 
8. At points of concentrated load (wheel load or reactions) the web of the girder must be 
checked for local crushing. If necessary, bearing stiffeners should be introduced to prevent 
local crushing of the web. 
 
9. The maximum deflection under working loads has to be checked. 
 
10. The gantry girder is subjected to fatigue effects due to moving loads. Normally, light-and 
medium-duty cranes are not checked for fatigue effects if the number of cycles of load is 
less than 5 x 10
6
. For heavy-duty cranes, the gantry girders are to be checked for fatigue 
loads (see IS 1024 and IS 807). Refer section 13 of the code for design provisions for 
fatigue effects. The fatigue strength is to be checked at working loads. 
                                                        
 
 
 
 
 
 
Page 4


                                                        
 
 
GANTRY GIRDER 
 
Introduction 
 
In manufacturing plant it is essential to provide overhead travelling crane to transport heavy 
components of machines from one place to another. The movement of the load is of three 
dimensional nature. The crane is required to lift heavy mass vertically and horizontally, also 
the crane with load is required to move along the length of the shed. The cranes are either 
hand-or-electrically operated. The crane moves on rails which are at its ends. The rails are 
provided on a girder known as a gantry girder. The gantry girder spans over gantry columns. 
If capacity of crane is moderate, the gantry girders rest on brackets connected to roof column 
of industrial shed. 
 
Characteristics 
 
? Design of gantry girder is a classic example of laterally unsupported beam 
? It is subjected to in addition to vertical loads and horizontal loads along and perpendicular 
to its axis 
? Loads are of dynamic nature and produce vibration 
? Compression flange requires critical attention  
 
Codal Provisions 
 
? Partial safety factor for both dead load and crane load is 1.5 (Table 4, p.29) 
? Partial safety factor for serviceability for both dead load and crane load is 1 (Table 4, 
p.29) 
? Deflection Limits (Table 6, p.31) 
Category Maximum Deflection 
Vertical deflection ? Manually Operated – Span/500 
? Electric operated- Span/750 upto 50t capacity 
? Electric operated- Span/1000 over 50t capacity 
Lateral deflection Relative displacement between rails supporting 10 mm or crane- span/400 
 
Other Considerations 
 
? Diaphragm must be provided to connect compression flange to roof column of industrial 
building to ensure restraint against lateral torsional buckling at ends. 
? Span is considered to be simply supported to avoid bumping effect. 
 
Design Steps 
 
The design of the gantry girder subjected to lateral loads is a trial-and-error procedure. It is 
assumed that the lateral load is resisted entirely by the compression top flange of the beam 
and any reinforcing plates, channels, etc. and that the vertical load is resisted by the combined 
beam. Various steps involved in the design are as follows: 
 
1. Maximum wheel load is to be calculated. The wheel load is maximum when the trolley is 
closest to the gantry girder. This load is to be correspondingly increased for the impact. 
 
                                                        
 
 
2.  Maximum bending moment in the gantry girder due to vertical loads is to be computed. 
This consists of the bending moment due to maximum wheel loads (including impact) and 
the bending moment due to dead load of the gantry and rails. The bending moment due to 
dead loads is maximum at the centre of the girder, whereas the bending moment due to 
wheel load is maximum below one of the wheels. For simplicity, the maximum bending 
moment due to dead load is directly added to the maximum wheel load moment. 
 
3. Maximum shear force is to be calculated. This consists of the shear force due to wheel 
loads and dead loads from the gantry girder and rails.  
? Generally an I-section with a channel section is chosen, though an I-section with a plate 
at the top flange may be used for light cranes.  
? When the gantry is not laterally supported, the equation to be used to select a trial 
section is as follows: 
Zp = Mu/fy ...............................................................................................(1) 
Zp (trial) = kZp, (k = 1.4-1.5) ....................................................................(2) 
? Generally, the economic depth of a gantry girder is about (1/12)th of the span. The 
width of the flange is chosen to be between (1/40) and (1/30)th of the span to prevent 
the excessive lateral deflection. 
 
4. The plastic section modulus of the assumed combined section is found out by considering 
a neutral axis which divides the area in two equal parts, at distance y to the area centroid 
from the neutral axis. Thus, 
Mp = 2fyA/2y = Ayfy,           where Ay = plastic modulus Zp ............................(3) 
 
5. When lateral support is provided at the compression (top) flange, the chosen section 
should be checked for the moment capacity of the whole section (clause 8.2.1.2 of IS800): 
Mdz = BbZpfy/? mo = 1.2Zefy/?mo ....................................................................(4) 
Above value should be greater than applied bending moment. The top flange should be 
checked for bending in both the axes using the following interaction equation: 
(My/Mndy) + (Mz/Mndz)  = 1 ........................................................................(5) 
 
6. If the top (compression) flange is not supported, the buckling resistance is to be checked in 
the same way as in step 4 but replacing fy with the design bending compressive stress fbd 
(calculated using Section 8.2.2 of the code). 
 
7. At points of concentrated load (wheel load or reactions) the web of the girder must be 
checked for local buckling and, if necessary, load carrying stiffeners must be introduced to 
prevent local buckling of the web. 
 
8. At points of concentrated load (wheel load or reactions) the web of the girder must be 
checked for local crushing. If necessary, bearing stiffeners should be introduced to prevent 
local crushing of the web. 
 
9. The maximum deflection under working loads has to be checked. 
 
10. The gantry girder is subjected to fatigue effects due to moving loads. Normally, light-and 
medium-duty cranes are not checked for fatigue effects if the number of cycles of load is 
less than 5 x 10
6
. For heavy-duty cranes, the gantry girders are to be checked for fatigue 
loads (see IS 1024 and IS 807). Refer section 13 of the code for design provisions for 
fatigue effects. The fatigue strength is to be checked at working loads. 
                                                        
 
 
 
 
 
 
                                                        
 
 
 
 
 
 
 
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FAQs on Design of Gantry Girders - Civil Engineering Optional Notes for UPSC

1. What are gantry girders used for in construction?
Ans. Gantry girders are used to support heavy loads, such as machinery or equipment, in various construction projects. They provide stability and structural support for overhead cranes or other lifting systems.
2. What materials are typically used in the construction of gantry girders?
Ans. Gantry girders are commonly constructed using steel or reinforced concrete due to their high strength and durability. The material choice depends on the specific requirements of the project and the load-bearing capacity needed.
3. How are gantry girders designed to withstand heavy loads?
Ans. Gantry girders are designed using structural engineering principles to ensure they can safely support the intended load. Factors such as material strength, beam size, and support structure are carefully considered to prevent structural failure.
4. What are the key design considerations when constructing gantry girders?
Ans. Key design considerations for gantry girders include the span length, load capacity, support structure, and environmental factors such as wind loads. These factors are crucial in ensuring the safety and stability of the gantry girder.
5. What are the advantages of using gantry girders in construction projects?
Ans. Gantry girders offer several advantages, including high load-bearing capacity, versatility in design, and cost-effectiveness compared to other structural support systems. They are commonly used in industrial settings for their reliability and efficiency.
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