Construction Loading Analysis

2010 Contractor Engineer Conference

Bill DreherStructures Design ChiefWisDOT

• Standard Specification Change– 108.7.3 Loads on Structures

• Research Project– WHRP – Development of a Bridge Construction

Live Load Analysis Guide

108.7.3 Loads on Structures

(1) Demonstrate that all loads on structures within the project limits throughout the duration of the contract do not exceed the structural capacity of the structure. If the engineer directs, submit stamped and signed copies of analyses and associated calculations performed by a professional engineer (PE) registered in the state of Wisconsin to the engineer and to the department's bureau of structures. Do not begin construction operations or move a heavy load across a structure without the engineer's written authorization.

108.7.3 Loads on Structures

• Ensure safety and structural integrity

• Contractor is responsible for analyzing structures with applied construction loads

• Stamped and signed by Wisconsin P.E. when directed by engineer

• Information (including latest inspection reports) available via Highway Structures Information system

108.7.3 Loads on Structures

(2) If a PE's analysis is required, determine capacity at the operating load level using the same AASHTO specification the structure was rated under. Include materials, equipment, and other construction or vehicular loads in the analyses. If under public traffic, also include the Wisconsin standard permit vehicle (Wis-SPV) as shown in chapter 45 of the department's bridge manual. The structure must be capable of carrying a Wis-SPV load equal to or greater than 100,000 pounds in addition to construction loads. The engineer's written authorization must be accompanied by a copy of the analysis stamped accepted by department's bureau of structures before proceeding.

108.7.3 Loads on Structures

• Operating Load Factors

• AASHTO Specification– LFD

– LRFD

• Include Wisconsin SPV if carrying public traffic

108.7.3 Loads on Structures

(3) Except as required to accommodate public traffic or to complete the deck pour, do not operate heavy equipment or impose vehicular live loads on lanes adjacent to freshly placed concrete decks until it develops sufficient strength to open it to service under 502.3.10.1.

108.7.3 Loads on Structures

No heavy equipment or vehicle loads on lanes adjacent to freshly placed deck– Minimize vibrations that affect development of

concrete strength and bond to reinforcement

Research Project

WHRP – Development of a Bridge Construction Live Load Analysis Guide

Research Project

• Collins Engineering, Inc.

• Literature Review• Current information on the effects of

construction loads

• On-going research projects

• Data on equipment loads

• Studies on load distribution

Research Project

• Present Practices Survey• State DOT’s – existing spec’s or under

development

• Wisconsin Contractors – typical construction practices and equipment

– Please participate!

• Load Model Studies• Live load distribution factors

Research Project

• Analysis Guide/Handbook• Permissible analysis approaches and stress

limits

• Equipment loads

– Variable crane configurations

– Track, outrigger loads

– Impact effects due to equipment and operations (breaking concrete, pile driving)

Research Project

• Analysis Guide/Handbook• Guidance to control and minimize load effects

– Crane position

– Load transfer mats

Research Project

• Recommended special provisions and spec language

Questions?

Thank You!