How to Manage Concrete Assets

Every now and again our industry endures a fatal accident involving the collapsing of a concrete grain bin. The heartbreaking news creates a shockwave throughout the town and surrounding communities, causing area elevators to suddenly question the sturdiness of their own structures. At this point a local engineer is called to examine the foundation, walls and roof. But if the facility doesn’t have a document called a baseline, the engineer is forced to act as a detective investigating a crime scene. Cracks, fissures and spalling can happen for a variety of reasons, and without the full history of the bin, it is anyone’s guess how the problem arose and how to fix it.

Sunfield Engineering，Inc。总裁Dick Kobetz说，一个良好的基线，这是一系列记录和数据，显示了自建筑物以来垃圾箱的演变，是维护滑滑混凝土结构的关键方面之一。如果您需要让工程师检查设施，则已经准备好的基线将有助于工程师诊断问题并设计解决方案。

当正确设计时，混凝土垃圾箱实际上是零维护资产；但是，应在施工之前和每年进行一些步骤，以确保垃圾箱将在未来几年内发挥作用。

Pre-construction considerations

The first step in ensuring the longevity of a concrete structure is properly assessing the ground on which you want to lay the structure’s foundation.

在开始在任何项目上施工之前，重要的是聘请一名岩土工程师来调查该地区。他们将使用土壤钻孔进行岩土工程报告，以确定存在哪种类型的土壤，基质，地质布局是什么以及可以在潜在的建筑工地中放置多少重量。

“People with small projects or plans to build lighter structures may be tempted to skip this step,” says Kobetz. “The $8,000 to $12,000 required to hire a geotechnical engineer might sound like a lot, but the truth is that’s the cheapest insurance you’ll ever buy for a structure.”

开始一个项目土壤不足会导致佛undation damage later on, a problem that is nearly impossible to fix once the structure is fully built and in use.

Kobetz还建议每次将新结构添加到该设施中时进行岩土技术报告。他说：“您可能需要在附近添加一个结构，并认为您几年前有一份岩土技术报告，因此可以肯定地依靠该报告。”“但是，必须从确切地建造新结构的地方获得钻孔，因为即使在似乎岩土技术条件可能是同质的地区，大自然母亲也会扮演各种肮脏的技巧。甚至50英尺进一步可以产生很大的不同。”

Once the geotechnical report deems the area fit to build on and the structure is erected, keep the report with your baseline. In addition to the geotechnical report, drawings, photos, a history log and information gathered through annual inspection should be included.

创建基线

良好的基线应由几个关键数据组成。保留在基准中的文件示例包括：

• Survey of the property

• Geotechnical reports

• Facility drawings including the original drawings as well as depictions of modifications to existing structures and new structures

•施工规格和操作文档

• Existing engineering reports or structural analyses

• Bin chart with information such as drawings of the configuration, dimensions and a list of associated equipment, such as side draws or flow devices

• Dated photos of the exterior and interior of the structure (and any areas of specific concern) to document current conditions and provide a basis for future comparison

•历史记录

跟踪历史

A properly designed, constructed and operated concrete structure may last up to 100 years, but it will probably endure many changes before its useful life is over. Changes in the bin over time are not cause for concern alone, but not monitoring the changes or understanding why they occurred can cause problems.

A history log can be crucial because it will tell you if or how much an aspect of the bin has changed since construction. Kobetz suggests using a logbook or spreadsheet to document the history of the plant including new information and events such as unusual weather, structural failures or accidents.

Unusual weather events can have an impact on concrete structures. Events to document include extremely high or low temperatures, excessive rain and/or flooding, ice and snow storms, high winds, tornados, hurricanes and earthquakes.

基础墙，隧道，坑和垃圾箱底部的结构故障也应与失败和随后的修复一样。

还应包括工厂的事故，包括火灾，爆炸或碰撞。

照片可以极大地帮助讲述设施或结构的历史。例如，在拍摄裂缝的照片时，请在其附近放置磁带尺寸，并约会每张图片，以评估裂缝的进度随着时间的流逝。

Documenting what type of material was being stored in the bin at a certain point in time can also help engineers understand the history of the bin. Bins and silos are structurally designed to handle different physical characteristics between free-flowing and millstock ingredients. Ensuring that the right ingredients go into the right bin will help avoid causing damage to the structure.

In addition to documenting events as they happen, it is important to conduct annual inspections and add any reports of unusual or troubling findings.

Preventative maintenance scheduling

One positive trend on the rise within the industry over the past 30 years is the notion of a preventative maintenance program, where all pieces of equipment and their components are inspected on an annual, quarterly or monthly basis.

These inspections are recommended not only to avoid structure collapse, but to ward off less fatal problems that still have a big impact on your business. Properly maintained bins will prevent water and dust penetration, cutting down the potential development of molds, toxins, other contaminants and pests.

If a facility has a good record of performance or is new, inspecting concrete structures once a year should be appropriate. In general, you want to check for water seapage or spalling, cracks, corrosion and particles or aggregate (stones) in the product stream.

但是，确定要关注的裂缝可能很棘手。在满载的混凝土结构中，经常间隔的垂直裂纹是正常的。垂直的裂缝，宽度超过1/32英寸，长5英尺，应升高危险信号，并表明更严重的结构障碍。

It’s important to schedule your annual inspection for while the bin is full.

“You want to look at the outside when it’s actually under load and being distressed,” says Kobetz. “In a concrete bin, once you empty it and take the load off of it, signs of distress or a crack that might be visible during unloading might appear much smaller when the bin is empty and may possibly become invisible.”

Additional items to look for include areas of exposed rebar combined with long vertical cracks over 1/16 inches wide, egg shaping of round silos and leaking hoppers. Egg shaping occurs when a bin that has been designed to discharge concentrically begins discharging eccentrically either by improperly using off-center floor gates or through the installation of a side-draw without proper structural modifications to the silo.

The bin roof, deck, floor and grating should also be inspected annually as well as any time modifications to the structure have been made. On the roof and deck, corrosion is a common issue to watch out for. Corrosion can stem from water pooling on the roofs or poor housekeeping.

正常见证地板上的裂缝并磨碎，但是如果添加了一块设备后突然出现裂缝，Kobetz建议打电话给专业工程师检查裂缝。

A thorough bin inspection may take around four hours every year and can translate to major savings by identifying construction problems and operator errors early on before a system failure occurs.

坚持设计

One of the most commonly overlooked ways to maintain concrete structures is to simply use the bin according to design specification and only for its intended purpose.

No process further emphasizes this than the discharge design. A bin that’s been designed to discharge concentrically will have a discharge gate in the middle and additional gates closer to the walls, which are intended for cleanout purposes only. If the middle gate becomes plugged, do not open a clean out gate to discharge from because it will create an eccentric flow situation.

这可能会通过抛弃垃圾箱内的压力平衡并将重量转移到结构的一侧，从而损害垃圾箱的设计。

Concrete structures that are properly designed and operated can last well over 50 years, and newer construction methods and materials can extend that figure even further. In some cases the function of the structure becomes obsolete before the structure wears out. But in other cases construction errors can lead to a collapse in as little as four or five years.

System failure

Failures in slip-form concrete structures, although rare, can occur as a result of design error, construction error, operator error or a combination of these factors.

Today building codes are in place to help keep facility workers safe. Concrete bins are designed to meet the Building Code Requirements for Structural Concrete (ACI 318), and Standard Practice for Design and Construction of Concrete Silos and Stacking Tubes for Storing Granular Material (ACI313) as established by the American Concrete Institute. Generally, the drawings for the facility must be submitted for a building permit and must be sealed by a Registered Professional Engineer.

Although there are building codes and regulations in place, if your structure is older and has signs of prior distress and deterioration that are not accelerating, or if the facility is 25 to 30 years old and you are concerned about its age and integrity, you may want to contact a professional engineer.

The engineer can work with a testing company to determine the most cost-effective method for identifying the volume and placement of reinforcing steel in your structures. Based on the testing data and knowledge of your operations, the engineer can perform the structural analyses to determine the soundness of the structure.

Kobetz指出，即使在较旧的结构中，也不是每个裂缝或剥落都是灾难或引起关注的原因。“如果您定期监控滑动形式的混凝土结构，并且没有观察到任何困扰或恶化的迹象，则没有用于专业检查或测试的技术理由；观察变化时，您应该继续监视结构并联系工程师。”

维护混凝土结构是一项简单的任务，即设施经理需要相对较少的时间。这也是可以管理要管理的所有其他方面的东西。每年都要花时间检查您的结构并更新基线，如果出现问题的话，可以为您的工程师提供愉快的态度，并为您的工程师提供重要文档。