EXAMPLE 2.7.1. OVERHANG DESIGN CASE 1

Using the previous example, design the deck overhang for the cast-in-place reinforced concrete deck. The parapet has been crash-tested and is deemed to have the capacity for the TL-4 load level.

[TL-4: Test Level Four: Taken to be generally acceptable for the majority of applications on high speed highways, freeways, expressways, and Interstate highways with a mixture of trucks and heavy vehicles.]

Materials used are the following:

Slab:                   Normal weight concrete, f'c = 27.58 MPa

                                                              fy   =  413.69 MPa
Wearing surface:   Asphalt concrete

Thickness of future wearing surface:         60mm

Thickness of top integral wearing surface: 12mm

Load modifier,   =1.80

DECK PARAMETERS

     Top cover           = 40mm

     Bottom cover      = 25mm

Using Normal weight concrete (f'c = 35 MPa), 

                                              ' or taking the unit weight,

                                        

Future wearing surface uses Asphalt concrete:

                                    or using the unit weight: 

                                               

From the previous solutions, the overhang was assumed to be 50% of S

            

DECK OVERHANG THICKNESS. AASHTO 13.7.3.1.2 specifies the minimum thickness according to different conditions:

• 200mm for concrete deck overhangs supporting a deck-mounted post system 
• 300mm for side-mounted post system
• 200mm for concrete deck overhangs supporting concrete parapets or barriers

Assume  

PARAPET PARAMETERS

Weight per foot of parapet,   

Base width, 

Parapet height, 

BRIDGE RAILING PROPERTIES

The railing would need to be divided into portions for moment capacity calculations.