Tag: Bridge Engineering

The Flow of the River: What 2D Hydraulic Modeling Can Teach us about Movement

GIF image of 2D hydraulic modeling showing water under a bridge

Imagine trying to measure water in a beaker or in a measuring cup; it is stagnant and easy to follow the line of meniscus to see if it’s a ½ cup or 3/4. Then imagine measuring water in a river in order to build safer bridges; it tumbles over rocks, it changes speed, it experiences different water levels throughout a season.

Believe it or not, water movement is one of the most difficult phenomenon to solve. Yes, you can apply mathematics or numerical methods to solve complicated differential equations, but there are always some unknowns about turbulent flows (class 4 rapids) where general assumptions are made.

Rivers require intricate numerical models for river-type engineering problems, and I have been accepted to present on these intricate models at this years biennial National Hydraulic Engineering Conference (NHEC) in Columbus, Ohio. The Conference spans a week from 8/27 to 8/31, and I will be presenting on Friday, August 31st.

Per the NHEC website (https://www.ohio.edu/engineering/nhec/), the conference is themed “Advancing Hydraulic Engineering through Innovation and Resilient Design,” and will address the challenges that transportation agencies face to construct, maintain, sustain, and improve hydraulic structures in the physical, natural, social, and economic environments of today and tomorrow. At this conference, I will be presenting on Two-Dimensional (2D) Hydraulic Modeling with Tidal Boundary Conditions.

Modelers typically use computer software packages where you input topography, flows, roughness parameters, and hydraulic structures. The software package uses the input to solve mathematical equations. It seems simple enough, but a modeler needs to have a conceptual understanding of numerical methods and know the limitations of the software package being used.

Whenever you hear the term “3D,” you think of an object in a space that has 3-dimensions, right? Similarly, water moves within a 3-dimensional space, where there is a z-component (up, down), y-component (left, right), and x-component (back, forth). What if I were to tell you that the movement of water in the z-direction (up, down) is not considered?

What would that mean? Well, what that means is that mathematically, we are simplifying a very complicated problem:  we are restricting movement of water to flow/move in 2D, 2-directions (x and y) and that is what 2D hydraulics is all about. Similarly, a one-dimensional (1D) hydraulic model is defined when the y-direction is neglected and water is confined to moving in the x-direction.

2D hydraulic modeling is not that new and has been available in an academia setting since the 80s. But in recent years, tools to develop 2D models have been readily available to engineers. A 2D model can’t be developed for every problem that we tackle, but it allows us to accurately represent actual real world conditions, make less assumptions and judgment calls, and communicate and show visualizations of flow movement to stake holders.

Are you ready for the new NH MS4 Stormwater Permit?

Pond with lily pads

EPA Region 1 issued the revised New Hampshire Small MS4 General Permit on January 18, 2017. Affecting 60 New Hampshire communities, this new permit will make a significant change in stormwater management compliance when it takes effect on July 1, 2018.

This new permit imposes more stringent regulations for communities’ compliance in regards to how to manage stormwater.

Many community leaders have expressed concerns that the overlap with other regulatory requirements and the cost of meeting those requirements may not effectively achieve the desired results, and they are looking for integrated cost-effective approaches to meeting the new regulatory requirements.

Governor Chris Sununu has publicly spoken against the new MS4 permits, saying that they would severely impact municipalities and taxpayers, noting that “additional mandates contained within the new MS4 permit will prove themselves overly burdensome and enormously expensive for many of New Hampshire’s communities.”

If you live in community in Southern New Hampshire, chances are that this change affects you in some way. To see a list of affected communities, please visit the EPA website.

Hoyle, Tanner has experienced staff who are knowledgeable about asset management, SRF loan pre-application preparation, and MS4 permitting.

John Jackman, PE, asset management specialist

 

John Jackman, PE, is Hoyle, Tanner’s premier Asset Management Specialist. Although the CWSRF money cannot be directly used to support the MS4 program, using the asset management program to support documentation of municipal assets will be helpful in setting up a strategy for compliance related to the October 1, 2018 required filing date of the MS4 permit’s Notice of Intent.

 

Michael Trainque, PE, stormwater specialist

 

Michael Trainque, PE, has 39 years of environmental engineering experience.  Michael has been integrally involved in developing model stormwater regulations, identification, assessment and dry-weather sampling and testing of stormwater outfalls, as well as other aspects of stormwater management.

 

marshall

Heidi Marshall, PE has been assisting industries and municipalities with NPDES compliance since the 1990s when EPA published the initial stormwater requirements and can assist you with preparation of the Notice of Intent, developing or updating the Stormwater Management Plan, and can provide assistance with the required follow-up actions.

 

Hoyle, Tanner is equipped to help communities that are affected by MS4 regulation changes. We are immediately available to help with pre-application funding, notice of intent preparation for October, and setting up action plans to comply with MS4 requirements.

Let Hoyle, Tanner guide your community into a future with cleaner water. Contact John Jackman, PE for asset management application assistance, or for MS4 assistance, contact Michael Trainque, PE or Heidi Marshall, PE.

14 Steps for Preserving Steel Structures

Piermont, NH-Bradford, VT Steel Bridge

Preventative maintenance is defined as scheduled work at regular intervals with the goal to preserve the present condition and prevent future deficiencies. On bridge structures, this work is typically performed on structures rated in ‘fair’ or better condition with significant service life remaining. Minor repairs may be necessary to maintain the integrity of the structure and prevent major rehabilitation. Structures that are not maintained are more likely to deteriorate at a faster rate and require costlier treatments sooner than maintained structures; therefore, it is more cost effective to maintain structures to avoid replacement or major rehabilitation needs.

New England’s weather causes extreme conditions for steel bridge trusses, such as flooding, ice and snow. Corrosive de-icing agents are used in the winter, which can accelerate deterioration of exposed bridge elements. Preventative maintenance is critical for steel truss bridges to reach their intended design service life and, therefore, attain the lowest life-cycle cost of the bridge investment. Presented are minimum recommended guidelines for preventative maintenance of steel truss bridges.

Here are 14 actionable maintenance tasks to preserve historic truss bridges:

  1. General: Remove brush and vegetation around structure. Annually.
  2. Bridge Deck & Sidewalks: Sweep clean sand and other debris. Power wash with water to remove salt residue. Annually.
  3. Wearing Surface: Check for excessive cracking and deterioration. Annually. 
  4. Expansion Joint: Power wash with water to remove debris, sand and salt residue. Annually.
  5. Bolted Connections: Inspect for excessive corrosion or cracking of the steel fasteners. Check for any loose or missing bolts. Annually.
  6. Welded Connections: Check for cracking in the welds. Annually.
  7. Truss Members: Power wash with water to remove sand, salt and debris, particularly along the bottom chord. Give specific attention to debris accumulation within partially enclosed locations such as truss panel point connections or tubular members. Annually.
  8. Bridge Seats: Clean around bearings by flushing with water or air blast cleaning. Annually.
  9. NBIS Inspection: Complete inspection of all components of the steel truss bridge. Every 2 years unless on Red List.
  10. Painted Steel: Scrape or wire brush clean, prime and paint isolated areas of rusted steel. Every 2 to 4 years.
  11. Steel Members: Check for rust, other deterioration or distortion around rivets and bolts, and elements that come in contact with the bridge deck which may be susceptible to corrosion from roadway moisture and de-icing agents. Every 3 to 5 years.
  12. Bearings: Remove debris that may cause the bearings to lock and become incapable of movement. Check anchor bolts for damage and determine if they are secure. Every 3 to 5 years.
  13. Exposed Concrete Surfaces: Apply silane/siloxane sealers after cleaning and drying concrete surfaces. Every 4 years.
  14. Bridge & Approach Rail: Inspect for damage, loose or missing bolts, sharp edges or protrusions. Every 5 years.

Actions to Avoid

  • Do not bolt or weld to the structural steel members.
  • Do not remove any portion of the structure.
  • CAUTION! Paint may contain lead.

Additional resources can be found through the New Hampshire Division of Historical Resources website.

“Climbing” the Memorial Bridge

ensuring the safety of the traveling public across the country. You might not realize it, but chances are every time you get in a car you drive across one or more bridges. Per the federally enacted National Bridge Inspection Standards (NBIS) every bridge, big and small, old and new, needs to be inspected on a biennial basis. As you can imagine, this is a huge undertaking for each state’s department of transportation (DOT), and each DOT is looking to inspect bridges faster, more cost effectively, and in less disruptive ways as to not impact the day to day usage of the bridge.

A dynamic, rapidly growing bridge inspection method is to “climb” the structure using rope access techniques. Rope access can best be pictured as a mixture of rock climbing and bridge inspection. The inspector is suspended from two ropes and can either ascend, descend or climb along the bridge. Certain bridges can often have elements that are inaccessible or uneconomical to inspect with traditional methods, such as rigging or the use of under bridge inspection vehicles. Rope access can be tailored for countless geometric challenges, which allows for a detailed, hands-on inspection of every bridge element. In other words, rope access allows inspectors to go anywhere and see any part of the bridge.

Recently a team of five Hoyle, Tanner bridge inspectors including three SPRAT1 and/or IRATA2 rope access inspectors completed a bi-annual inspection of the Memorial Bridge in Augusta, Maine. This 2,100 foot long, 75 foot high historic deck truss bridge posed many challenges for bridge inspection access. Access from the ground below was limited because part of the bridge is over the Kennebec River, and access from above was prevented by a tall chain link fencing that runs the entire length of the bridge. Most importantly, this bridge is a vital transportation route in the heart of the state capital making closing all or part of the bridge to traffic undesirable. Utilizing rope access techniques, we were able to perform a hands-on inspection of every member of the bridge from below the deck and above the river. Rope access allowed for a faster and more cost effective inspection than the traditional methods typically used.

  1. Society of Professional Rope Access Technicians– North American body for developing rope access standards and practices.
  2. Industrial Rope Access Trade Association– Internationally recognized body for developing rope access standards and practices.