Presentation on theme: "Structural Steel Design"— Presentation transcript:
1Structural Steel Design T. Michael Toole, Ph.D., P.E.Daniel TreppelStephen Van NosdallBucknell University
2Learning Objectives Summarize the Prevention through Design Concept List reasons why project owners may wish to have PtD performed on their projectsList reasons why structural engineers may wish to consider performing PtDIdentify three or more examples of PtD when designing structural steel buildings.
3Instructions for Instructors TopicSlide #sApprox. minutesPrevention through Design Concept5-2730Steel Design, Detailing, and Fabrication Process28-3310Steel Erection Process34-38Specific Steel PtD Examples39-7450Recap and Citations75-805Dear Instructor,This presentation file is intended to facilitate the incorporation of Prevention through Design concept into your steel design course. The file is organized to make it easy for you to use the slides that fit the number of hours of instruction that your course schedule allows. Slides __ through __ introduce the PtD concept and can be covered in approximately __ minutes. Slides __ through __ use AISC materials to summarize the design, detailing and fabrication process. Slides __ through __ use AISC materials to summarize the steel erection process. Some instructors will wish to use the two sets of process slides earlier in their course, well before they explicitly cover PtD. Slides __ through __ provide specific examples of Prevention through Design opportunities in structural steel engineering from a research report published by the Construction Industry Institute and the Detailing Guide For Erector’s Safety & Efficiency published jointly by the National Institute of Steel Detailing and the Steel Erectors Association of America.Each slide is accompanied by a set of speaker notes, that is, a “script” that you can read aloud while the slide is projected on the screen. If you show the presentation file in slideshow mode (click in F5), the audience will not be able to see the speaker notes. If you click on “Use Presenter View” on the Slide Show tab, your monitor will show the speaker notes but the projected image will not.You will probably wish to modify the following Overview slide to reflect the topics that you will cover.1
4Overview Prevention through Design Concept Steel Design, Detailing, and Fabrication ProcessSteel Erection ProcessSpecific Steel PtD Examples(Note to Instructor: You will probably wish to modify this slide and the speaker notes below to reflect the topics that you will cover. For example, you could delete the topics that you will not cover or italicize the topics you do not cover and make the presentation file available to the students to let them review outside of class topics not covered in class.)This is an overview of what the Prevention through Design topics that we will cover. Many of you are probably not familiar with the concept of Prevention through Design so we will spend a few minutes discussing what the concept is. Next we will summarize the structural design, detailing and fabrication process that we have discuss from time to time in this course. Similarly, we will summarize the steel erection process, which has also come up in class previously. Finally, I will show you some specific ways that structural engineers and detailers can incorporate Prevention through Design into their steel designs.
5Introduction to prevention through design Let’s start by introducing you to the Prevention through Design concept.
6What is Prevention through Design? Eliminating work-related hazards and minimizing risks associated with…Construction or ManufactureMaintenanceUse, re-use and disposalFacilitiesMaterials andEquipment…ofPrevention through Design (PtD) is an emerging risk management technique that is being applied successfully in many industries, including manufacturing, healthcare, telecommunications and construction. The concept is simply that the safety of workers throughout the life cycle is considered while the product and/or process is being designed. The life cycle includes the construction or manufacturing, operations, maintenance and eventual disposal of whatever is being designed, which could be a facility, a material or a piece of equipment.PtD processes have been required in other countries for several years now, but in the U.S. it is only being adopted on a voluntary basis. The National Institute for Occupational Safety and Health (NIOSH) is spearheading a national initiative in PtD and partnering with many professional organizations to apply the concept to their industry and professions. The Occupational Safety and Health Administration (OSHA) in very interested in PtD but is not currently considering making it mandatory.In construction, PtD represents a change from custom and practice whereby design professionals (that is, architects and/or engineers), and typically the project owner (that is, the client), become involved in reducing the risk of injuries or other health hazards throughout the life of a project, beginning at the earliest stages of a project’s life cycle. PtD is thus the deliberate consideration of construction and maintenance worker safety in the design phase of a construction project. PtD processes in construction have been required in the UK for over a decade and are being implemented in other countries such as Australia and Singapore.It is important to note that the PtD concept applies only to the design of the permanent facility, that is, to the aspects of the completed building that make a project inherently safer to build. PtD does not focus on how to make different methods of construction engineering safer. For example, it does not focus on how to use fall protection systems, but it does include consideration of design decisions that influence how often fall protection will be needed. Similarly, PtD does not address how to erect safe scaffolding, but it does relate to design decisions that influence the location and type of scaffolding needed to accomplish the work. Design professionals are in a position for decision-making and influencing to help improve construction safety in these and many other areas.For example, when the height of parapet walls is designed to be 42”, the parapet acts as a guardrail and enhances safety. When designed into the permanent structure of the building and sequenced early in construction, the parapet at this height acts to enhance safety during initial construction activities and also during subsequent maintenance and construction activities, such as roof repair. Without this consideration, constructors are solely responsible to design, prepare, and implement other temporary safety measures even if the design hinders the ease in which they are utilized.
7Successful Firms Using PtD Design Builders:URS/Washington GroupJacobsParsonsFluorBechtelOwners:Southern CompanyIntelThis slide lists some of the major American design-builders and owner corporations with PtD initiatives or established programs. In some cases, PtD was initiated by the CEO as part of safety being a top corporate value. In other cases, PtD was originally undertaken because it was required on the firm’s european projects then spread to american operations. Common components of these firms’ programs include providing design engineers with construction site safety training, PtD checklists and safety constructability reviews. These and other firms will be looking to hire structural engineers who are willing to learn how to perform PtD.10
8Why Prevention Through Design? Construction is dangerousDesign does affect safetyEthical reasonsPractical benefitsThe next few slides will show there are many reasons why owners and design professionals should be motivated to have PtD performed on a project.
9Typical Annual Construction Accidents in the U.S. 1 Construction is one of the most hazardous occupations7% of the US workforce but 21% of fatalitiesAbout 1,000 deathsAbout 200,000 serious injuriesUnfortunately, as many of us know, construction is one of the most dangerous industries to work in. In the U.S., construction typically accounts for just under 200,000 serious injuries and 1000 deaths each year. The fatality rate is disproportionally high for the size of the construction workforce. But statistics like these do not tell the whole story. Behind every serious injury, there is a real story of an individual who suffered serious pain and may never fully recover. Behind every fatality, there are spouses, children and parents who grieve every day for their loss.Because we all recognize that safety is an inherently dangerous business, all of us—including architects and engineers--must do what we can to reduce the risk of injuries on the projects we are involved in.
10Design Contribution to Occupational Fatalities: Australian Study 2000-2002 Main finding: design continues to be a significant contribution to work-related serious injury.37% of workplace fatalities involved design-related issues.In another 14% of fatalities, design-related issues may have played a role.Several studies around the world have demonstrated that design can directly affect the safety of a construction site or process. The Australian Government investigated the “design-related” root causes of their work-related fatalities. Seventy-seven (37%) of the 210 identified workplace fatalities definitely or probably had design-related issues involved. In another 29 fatalities (14%), the circumstances were suggestive that design issues were involved.Driscoll, T.R., Harrison, J. E., Bradley, C., Newton, R.S. (2005)
11Accidents Linked to Design 22% of 226 injuries that occurred from in Oregon, WA, and CA linked partly to design 242% of 224 fatalities in U.S. between linked to design 2In Europe, a 1991 study concluded that 60% of fatal accidents resulted in part from decisions made before site work began 363% of all fatalities and injuries could be attributed to design decisions or lack of planning4Research conducted in the U.S., Europe and other regions has also shown that design does affect the inherent risk in construction a facility. Doctoral research by professor Mike Behm at East Carolina State linked design to 22% of injuries that occurred in western states and 42% of fatalities across the country. European researchers found that nearly two-thirds of fatalities and injuries were linked to design. So we know that design does make a difference in construction safety.
12Ethical Reasons for PtD National Society of Professional Engineers’ Code of Ethics:Engineers shall hold paramount the safety, health, and welfare of the publicAmerican Society of Civil Engineers’ Code of Ethics:Engineers shall recognize that the lives, safety, health and welfare of the general public are dependent upon engineering decisions…Some safety professionals and design professionals believe that PtD is clearly an ethical duty. Nearly all national engineering societies included in their code of ethics a statement similar to the one shown here for the National Society of Professional Engineers: “Engineers shall hold paramount the safety, health, and welfare of the public.” ASCE goes one step further and explicitly states that engineering decisions directly affect safety. Yet these organizations, as well as the American Institute of Architects, refer to protecting the “public”. Why? Because the public cannot possess the knowledge of forces and stresses and other risk-related issues that engineers can. But the same is true for many construction and maintenance workers. These people are human too and deserve the same consideration for their health and safety.7
13Hierarchy of ControlsEngineers are vital to minimizing occupational risks through the application of the hierarchy of controlsThe engineering design process provides the framework for the application of prevention through design(Mike T. will appreciate it if one of the professional safety members of the team writes the speaker notes for this slide. He thinks the graphic should be cropped to eliminate white space and increased in size to allow audience to read the text.)
14ConstructabilityConstructability is an evaluation of how reasonable the design is to construct in terms of:CostDurationQualitySafetySafety is an often neglected aspect of constructabilityMost designers know that what may look great on paper might not be feasible in the field, or may cost the owner more to construct than is necessary. Most designers therefore acknowledge that an important part of the design process is to evaluate the design’s constructability, that is, to what extent can the design be constructed at a reasonable price, quickly and of high quality. Looking at the two building in the photos, the building in the top photo was clearly easier to build than the one in the bottom photo. What some designers do not realize or do not acknowledge is that safety is also an important part of constructability. Don’t all clients want their designs to be as safe as possible to build? What client would not care if a design is much more risky to build than is necessary? Accidents cost money, delay construction and may result in bad press for the owner.
15Issue for Construction Trade contractor involvement PtD Process 6Design KickoffDesignInternal ReviewIssue for ConstructionExternal ReviewTrade contractor involvementEstablish design for safety expectationsInclude construction and operation perspectiveIdentify design for safety process and toolsQA/QCCross-discipline reviewFocused safety reviewOwner reviewThis graphic depicts the typical PtD process. The key component of this process is the incorporation of site safety knowledge into design decisions. Ideally, site safety would be considered throughout the design process. It is recognized, however, that a limited number of progress reviews for safety may be more practical. The required site safety knowledge can be provided by one or more possible sources of such safety constructability expertise, including trade contractors, an in-house employee, or an outside consultant. In the future, perhaps state and federal OSHA employees may provide such expertise.This graphic points to a less obvious benefit of PtD: the communication between designers and constructors that is typically required to facilitate PtD. Such communication during design typically also leads to discussion of how to better value engineer the design or to reduce construction duration.1 Gambatese
16Success will only be achieved by integrating occupational safety and health with engineering design processStageActivitiesConceptual DesignEstablish occupational safety and health goals, identify occupational hazardsPreliminary DesignEliminate hazards, if possible. Substitute less hazardous agents / processes, and establish risk minimization targets for remaining hazards. Assess risk and develop risk control alternatives.Detailed DesignSelect controls. Conduct Process Hazard Reviews.ProcurementDevelop specifications and include in procurements. Develop “checks and tests” for factory acceptance testing and commissioningConstructionConstruction site safety and contractor safety.CommissioningConduct “checks and tests” including factory acceptance. Pre-start up safety reviews. Development of SOPs. Risk / exposure assessment. Management of residual risks.Start Up and OccupancyEducation. Management of change. Modification of SOPs(Mike T. will appreciate it if one of the professional safety members of the team writes the speaker notes for this slide.)
17Safety Payoff During Design Considering Safety During Design Offers the Most Payoff 5HighConceptual DesignDetailed EngineeringAbility to Influence SafetyProcurementConstructionMost owners and design professionals know intuitively that the earlier in the design process that cost is considered, the easier it is to achieve cost effectiveness goals. The same is true for construction duration and quality. Your ability to influence a project criteria decreases as the design and construction progresses. The same principle is true for construction safety. The earlier in the project life cycle that safety is considered, the easier it is to reduce hazards. This concept is in contrast to the prevailing methods of planning for construction site safety, which do not begin until a short time before the construction phase, when the ability to influence safety is limited.Start-upLowProject Schedule
18Benefits from PtD Reduced site hazards so fewer injuries Savings from reduced workers compensation insurance costsIncreased productivityFewer delays due to accidentsEncourages designer-constructor collaborationPtD is believed to result in a wide range of benefits, some obvious to industry professionals and some less obvious. For example, when a project has been designed with construction worker safety in mind, there will be fewer hazards on site to managed and few injuries and fatalities will result. Reduced injuries will result in reduced workers compensation insurance, which will accrue directly to the owner on projects with an owner controlled wrap up insurance program. Many professionals believe also PtD leads to improved productivity because workers face fewer hazards, which will reduce labor costs and therefore reduce total costs to the owner. Accidents always delay construction progress in some way, so safer designs lead to fewer project delays.
19Business ValueThe AIHA Value Strategy* demonstrated the most significant business contributions result from…Anticipating worker exposures and designing process improvements to reduce or eliminate these exposuresAligning health and safety interventions with business goalsIntegrating health and safety risk management requirements into the design processFacilities, equipment, tools, processes, products and work flows…resulting in significant contributions to business profitability(Mike T. thinks there is too text on this slide and the smallest font is too small.)Companies that have implemented PtD programs experience world-class injury and illness rates and lower workers’ compensation expenses. However, the business value of PtD does not end there. In the Value of the Industrial Hygiene Study, “Demonstrating the Business Value of Industrial Hygiene” (aka, The Value Study), significant business costs savings are associated with hazard elimination and the application of engineering controls to minimize risks.*www.ihvalue.org
20OSHA Regulations ‘‘Code of Federal Regulations’’ (29 CFR 1926) States can have more stringent regulationsUpdated annuallyAll employers, include structural design firms, are required by law to provide their employees with a safe environment and training to recognize hazards that are present and equipment or other means to minimize or manage the hazards. Engineering employees historically have not received training on hazards or the federal OSHA standards because they were rarely exposed to jobsite hazards. With the increasing site roles that design engineers are playing—such as part of a design-build team—it is becoming increasingly important for design engineers receive construction safety training that includes federal or state construction safety standards.The written standards that govern most employers are enforced by the federal Occupational Safety & Health Administration (OSHA) and are found in Title 29 Part 1926 of the Code of Federal Regulations. Structural steel is covered in Subpart R. These regulations apply to every state that does not have their own set of regulations. (The OSHA Act encourages States to develop and operate their own job safety and health programs.) OSHA approves and monitors State plans. (State Plans must issue job safety and health standards that are "at least as effective as" comparable federal standards within six months of federal issuance. State Plans also have the option to promulgate more stringent standards or standards covering hazards not addressed by federal standards.)
21A new version of the federal construction safety standards is issued periodically but the vast majority of sections do not change. Because the sections have been written by different authors over decades, the writing and detail of each section varies widely. Some sections seem vague while others are overly detailed, and different sections can appear to contradict each other 9. To help steel design and construction employers determine what their employee safety responsibilities are, OSHA maintains webpages that contain interpretations and clarifications of the federal standards and provide access to eTools that may adopted on a voluntary basis. This slide shows the steel erection eTool, which helps communicate the requirements of Subpart R.Steel Erection eTool Website, Available at
22Construction Hazards 7, 8 Falls Ergonomics/Musculoskeletal Injuries Falling ObjectsTripping(Note to Donna and team: This slide was modified by my students based on a slide grabbed from another file. The speaker note text needs to be improved but I am having trouble writing better text. I would appreciate suggestions from team members with stronger general safety backgrounds.)There are a myriad of hazards on a construction site that can potentially cause great harm or even death. While the most common hazards will be addressed, it is worth knowing that hazards exist everywhere, not always where they are expected or anticipated. Even minor hazards can cause major damage if an unfortunate set of circumstances are present. This is why every hazard that can be addressed should be addressed as best possible.Falling, whether from an elevated height or not, can always cause serious injury. Falls are considered the most prominent danger on sites and will be discussed in depth on a later slide. Musculoskeletal injuries involve damage to your skeleton or muscles and are usually the product of strenuous activity. On a construction site, common culprits are heavy lifting and working in awkward positions (common for bolters and welders). Falling objects is the danger of being struck by an object that has fallen from a higher story. Whether a structural member of a simple wrench, these can cause great damage or even death if one is not adequately protected (and can still hurt even if they are). Personal protection equipment (PPE) is of great use here. Tripping is a hazard that is found in everyday life, but the elevated height and proximity to dangerous equipment can make tripping deadly on a construction site. There are other sources of common injury, such as spatial issues, which could include, getting your hands stuck while making a connection, hitting your head on an object with low head clearance, or cutting yourself on sharp corners.
23FallsNumber one cause of construction fatalities; in 2004, they accounted for 445 of 1,234 deaths, or 36 percent 7Common fall situations include making connections, walking on beams or near openings such as floors or windowsFall protection for steel erection required at height of 15 feet above a surface 10Causes include slippery surfaces due to water, ice or oil, unexpected vibrations, misalignment, and unexpected construction loads.Falls are the number one cause of deaths in the construction industry. Falls from any height can be fatal, and due to the nature of steel construction, workers are often high off the ground. For structural reasons, the taller cross sections of W-shapes are usually chosen for beams, but the flanges on these beams are usually only a few inches wide. Even so, beams are often walked across by workers to get to various places on the structure, but without fall protection, walking across beams can be a deadly hazard. Really any place with an opening is a hazard, simply because if it is an opening, you can fall through it.Fall protection is highly recommended and often required in most scenarios involving heights. For steel construction, OSHA requires fall protection at height of 15 feet above a surface (for other construction phases it is 6 feet).This slide indicates there are many causes that can lead to falls.
24Personal Protection Equipment (PPE) Last line of defense against injury 4Includes but not limited to:HardhatsSteel-toed bootsSafety glassesGlovesFall harnessesPersonal Protection Equipment (PPE) are items worn by the individual themselves as a LAST line of defense against injury. OSHA-required PPE can include hardhats, steel-toed boots, safety glasses or safety goggles, gloves, ear muffs, full body suits, respiratory aids, face shields, fall harnesses, etc.
25PtD Process Tasks 11, 12 Perform a hazard analysis Incorporate safety into the design documentsMake a CAD model for member labeling and erection sequencingAn earlier slide showed a graphic of the PtD process. This slide provides more details. Before, during or after the conceptual design of a building is performed, a hazard analysis can be performed. A hazard analysis consists of the designer meeting with field professionals and performing a constructability review, which consists of looking through the entire design for any hazards and addressing those hazards. By getting a field professional’s review, the designer gains valuable tacit knowledge and experience about design aspects that can lead to unnecessary risks. We will shortly see a set of slides that provide specific examples of unnecessary hazards that can be designed out.The safety constructability input received during conceptual design can be used to guide the detailed design drawings and specifications. Additional safety constructability review should occur as the detailed design nears completion. Sometimes the drawings that result from a PtD process look the same as typical construction drawings but they are inherently safer to construction. Other times, drawings include special details and labels to make it easier for the workers to erect the drawings safely.The construction documents can be supplemented with graphical models and tables that contribute to safe erection. For example, a CAD file can be used to label steel members for safe erection sequencing. A BIM model helps ensure spatial problems are found before construction. Having everything labeled on drawings when sent to the mill will ensure there is no confusion about where each piece is to be installed. Using a program can also help to ensure that sequencing is as efficient as possible, but that the intermediate structures are safe. New programs such as BIM are able to show the final layouts of buildings, and can detect any spatial problems before construction starts. Although BIM is still a relatively new technology, it use is growing at a very rapid rate.
26Designer Tools Checklists for Construction Safety 13 Design for Construction Safety Toolbox 14Construction Safety Tools from the UK or AustraliaCHAIR 4Most designers have not been trained in construction site safety or on how to perform PtD. It is therefore critical that they be provided with tools to facilitate the process.A PtD checklist alerts designers to common design elements that can lead to unnecessary hazards and identifies design options that are inherently safer. An example checklist is provided on the next slide.The Design for Construction Safety Toolbox was developed by a Construction Industry Institute-sponsored research team that included leading PtD academics. This Toolbox was recently updated by Professor Jimmie Hinze at the University of Florida.The UK and Australia make available on the web valuable PtD tools that reflect their experiences with PtD legislation and voluntary initiative. For example, CHAIR (Construction Hazard Assessment Implication Review) is an Australian tool and is methodology that systematically combines brainstorming and decisions to gradually rid the design of unnecessary hazards.
27Example ChecklistLike many PtD checklists, this example checklist includes hazards associated with both construction and maintenance.
28Design, Detailing and Fabrication process SteelDesign, Detailing and Fabrication processThis section summarizes the steps from design through fabrication.
29Three Entities Associated with Design EngineerDetailerFabricatorDesign process across the U.S.There are three different bodies that help design structural steel.:The Engineer creates the overall structural design, calculates loads according to building codes, determines the layout and sizes of structural steel members, and often designs the connections between members.The Steel Detailer takes contract documents and transfers relevant information to the shop drawings. In some cases, especially on the East Coast of the US, the engineer will delegate the task of connection design to the steel detailer. This is not allowed on the West coast, since the seismic activity in the area requires stricter design standards. The AISC has regulations for the necessary parts of connection design before being delegated, such as load calculations. Sometimes the steel detailer’s PE will stamp the connection drawings. The Steel Fabricator completes the shop and erection drawings and uses them to fabricate steel members.The use of Building Information Modeling (BIM) software by all parties facilitates more efficient collaboration and with fewer errors.
30Design Phase Owner tells A/E requirements for building Designer runs analysis on design according to building codesBuilding is designed for:Safety, serviceability, constructability, and economyFinal Design Specifications and Drawings are given to clientDesign calculations are safely stored by designerThe design process begins when an owner decides that he wants to build some new facility and identifies an architect or engineer to design it. In most buildings an architect will be in charge of the main design, but a engineer will be in charge of the structural system. The owner will communicate necessary design criteria to the AE, and the engineer will perform design and analysis based on building codes, such as the IBC (International Building Code). Common design criteria include: 1) Occupant safety—ensuring the structure will not fail and fall down under design loads; 2) Serviceability ensures that the structure performs well enough for use as it was intended and does not for example, result in excessive vibration or beam deflection; 3) Economy ensures the building will not have excessive cost, and 4) Constructability ensures that the structure can be built without excessive construction difficulties and includes construction safety.The design will require multiple iterations until the designer feels the structure is as good as it can be, and then gives the client his final design specifications and drawings. Meanwhile, all design calculations are stored in the designer’s vault. It is important to have neat, clear calculations saved as evidence of a good design.
31Detailing 15The fabricator receives the engineer’s drawings; then they will be programmed into computer software to help visualize the connections15 Daccarett, V., and T. Mrozowski. "Structural Steel Construction Process: Technical.”15 Daccarett, V., and T. Mrozowski. "Structural Steel Construction Process: Technical.”Shop Drawings 15While detailing, the fabricator makes drawings containing specific information about how to fabricate each memberSteel detailing involves identifying the specific dimensions of every aspect of a structural steel member and connection, including bolt holes, cut outs, web stiffeners, etc. Detailing is a critical step between the design and fabrication that typically involves tolerances of tenths of an inch. A small mistake in just one dimension can result in thousands of dollars of additional labor and crane time to resolve. While some detailing is still done manually, many detailers today create elaborate computer models of a structural steel frame and connections using sophisticated 3D detailing software. These models can then be passed on to the Fabricator to allow efficient computer numerically-controlled fabrication.
32Fabrication15 To achieve its final configuration the steel may be: Cut ShearedPunchedDrilledFitWeldedEach final member is labeled with apiece mark, length, and job numberfor identificationAfter the fabricator has manufactured or purchased the specific structural shape called for, the piece is finalized for erection in the fabrication shop. Specifically, to achieve the final configuration shown in the detailed shop drawings, the steel may be cut, sheared, punched, drilled, fit, and welded so that it has the proper length, holes, and connection plates. Some fabrication shops are better equipped for certain types of connections, so if the detailers design a connection, they will design such that they will be able to easily fabricate the connections, saving the owner time and money. Finally, each piece is labeled with a piece mark, length, and job number so it can be identified and properly installed.
33Transportation Members are transported via: Flatbed truck Train WaterwaysTransportation is one of the limiting factors on beam/column length. After fabrication members are transported by flatbed truck, waterways, railroad, or probably a combination of the three. Steel manufacturers will often try to locate themselves near a waterway or railway for transportation purposes.cs.trains.com/trccs/forums/p/161645/ aspx
34Erection Process Steel This section summarizes the typical structural steel erection process. Many of the text and photos have been taken from the excellent instructor aids that the AISC makes available to instructors on their website.
35Unloading and Shake-Out 15 Steel members are unloaded from the trucks and placed on blocking to allow chokers to be easily attached.Shake Out: when members are sorted on the ground to allow for efficient erection.The members will most likely arrive at the site on a truck, at which point they will be unloaded. Depending on the job site location the members can all be unloaded and stored at the beginning of construction, or in more crowded urban sites may need to be continually delivered and immediately erected. If enough space exists the members are placed on steel blocking to allow the crane chokers to be attached to lift them into place. The members also are “shaken out,” which is a process of sorting on the ground to arrange the members in an order that is beneficial for erection efficiency.15 Daccarett, V., and T. Mrozowski. "Structural Steel Construction Process: Technical.”
36Picking and Hoisting 15 Cranes are used to lift members into place Columns have a hole at an end that is used to pick it upBeams have chokers tied around their center of gravity, and multiple beams can be lifted at once15 Daccarett, V., and T. Mrozowski. "Structural Steel Construction Process: Technical.”A crane is used to lift the members into place. Columns will have a hole located at the end to pick it up, and will be placed on a base plate to be secured in the ground. Beams have chokers tied around their center of gravity. Often times, there will be more than one choker supporting a beam, especially during initial bolting. Multiple beams can be lifted at the same time, as shown, to lessen the time required for the crane to be moving back and forth to pick up the members.
37Positioning and Initial Bolting 15 Each beam is lowered into place, and a worker will line it up correctly using drift pins. At least two bolts are attached before the crane releases the load (OSHA requirement).As the crane lowers the beam into place a construction worker will line up the connection using drift pins. After the holes are correctly aligned at least two bolts are installed and tightened with a spud wrench. They are not at full tightness as this stage is only temporary. After these bolts are installed the crane may release the load. This can be a very dangerous stage in the construction since it requires working with an unsecured beam getting most support from a crane.15 Daccarett, V., and T. Mrozowski. "Structural Steel Construction Process: Technical.”
38Final Bolting15Once everything is assured to be in the correct position, the final bolting is performed using a torque wrench or similar tool.Periodically, the structure is “plumbed up” to ensure the structure is within acceptable vertical and horizontal alignment. Once the structure is ensured to be within specification, final bolting occurs. A torque wrench or other device that applies a specific amount of tension is used to ensure that the proper tension is achieved in the final installation.15 Daccarett, V., and T. Mrozowski. "Structural Steel Construction Process: Technical.”
39Examples of Prevention through design SteelExamples of Prevention through designThis section provides a number of examples of how PtD can be applied to structural steel design. Nearly all of these examples were taken either from a research report published by the Construction Industry Institute and the Detailing Guide For Erector’s Safety & Efficiency published jointly by the National Institute of Steel Detailing and the Steel Erectors Association of America.
40Topics Prefabrication Access Platforms Columns Beams Connections Slide NumbersPrefabricationAccess PlatformsColumnsBeamsConnections-Bolts-WeldsMiscellaneousPtD examples and guidelines will be briefly covered for the structural steel components shown on this slide.
41Prefabrication 16 Shop work is often faster than field work Shop work is less expensive than fieldworkShop work is more consistent due to a controlled environmentShop work yields better quality than fieldworkLess work is done at high elevations which reduces the risks of falling and falling objectsOne of the easiest ways to increase safety to reduce the amount of fabrication and connections done in the field by increasing the amount of fabrication done in the shop and preassembling pieces of the structure. Prefabrication and pre-assembly allows more of the work to be done on grade rather than at dangerous heights. The prefabricated member will still need to be attached at the height it was intended for, so prefabrication will not eliminate the need to be high up, but it will reduce the time that workers spend at height. Prefabrication does have a setback. It is limited by the ability to transport and install pre-assembled pieces.Prefabrication also offers other practical benefits. In general, fabrication in controlled environments is of better quality and can be performed more quickly. Shop fabrication can be done on a table, can be done with machines, and can be done with automated equipment. Even without the safety implications, prefabrication is becoming more common due to its other, previously mentioned benefits, namely quality, time, and consistency.
42Example: Prefabricated Truss Less connections to make in the airSafer and fasterRoof trusses are one example of prefabrication that greatly decrease the number of connections that need to be made in the air, which is both safer for construction workers and allows the project to be completed faster. Other examples included prefabricated walls and the bridge segments and steel stairs shown here.
43Access Help Shop installed vertical ladders Bolt on ladders and platforms can be removed later, or kept for maintenanceAccess ladders and platforms can come shop installed or bolted on, which can be kept for maintenance or removed. The ladders help reach high places and the platforms help access connections and other areas that require work. The first way access ladders and platforms can help is by providing access to a connection that would other wise be very difficult to reach. This will improve the quality of whatever action is done there (for example, welding) and it will include safety. The safety is increased for two reasons: first, there is a less likely chance fall due to an overcomplicated action. An example of this would be using an access platform to work versus reaching out really far out to work. Second, the access platforms and ladders reduce the number of situations requiring awkward positions to do the work. As discussed earlier, awkwardly positioning your body repeatedly or for extended periods of time can cause musculoskeletal injuries.
44Column Safety Column Splices Holes for safety lines Base plates Being that they are very heavy and very tall, there are many ways in which columns can pose a danger to workers. Three problem areas will be addressed here.First, it is obvious that tall buildings require very long columns, but for both structural and transportation reasons they cannot be made as one huge column. Therefore, multiple columns are spliced together to reach great heights. This is why column splices exist, which will be discussed soon.Also, working with columns would be very dangerous without fall protection, but how can it be implemented? Shop fabricated holes for safety lines are needed and there are specific places that they should go.Finally, looking at that picture, it is clear that those columns are solely supported by their base plates. At the moment they are cantilevers. Ensuring that these base plates are secure and will not fail is also very important, especially after more members are on the structure.
45Column SplicesHave column splice around 4 feet above the working floor 17OSHA RequirementColumn splices are necessary for making very tall structures, as one very long column is neither transportable nor structurally desirable. However, the location of the column splice can make work very easy or very difficult. It is very beneficial to place the column splices about four feet above the working floor. This would place the splice near most workers’ chest, which eliminates any kind of awkward positioning such as bending over to work or reaching up to work. Placing the splices here also prevents connections from sharing the same place as the beam connections, which simplifies the tasks of putting the connection together and putting the splice together. This practice is so important that it is actually an OSHA requirement.Also, it is an efficient practice to use column splices every two stories. While one long column is not a good idea, neither is having too many column splices. A two story column is both structurally sound and transportable, which makes it a good length to choose.Courtesy Bucknell University Facilities
46Holes for Safety Lines 18, 19Include holes at 21 inches and 42 inches for guardrails.Additional higher holes can also be included for lifeline support.Safety lines are necessary for fall protection, but attaching oneself to a member a safety line can take some work if the member has not been prepared. There are a few ways to attach to a fall protection system. Steel cables can be strung between these holes, and the worker can tie off to the cable. This method has the benefit of mobility, as you can walk around and the tie off point will follow along the cable. Also, there can be tabs for installing safety handrails.The way that these practices can be improved is include these holes in the members during fabrication, so that these holes do not have to be made on site, or even worse, after the members have been erected. For the guardrails, include holes at 21 inches and 42 inches from the elevation of the floor. These heights should prevent workers from getting under the rail or over the rail. The installation of tie off points or the steel cables are facilitated by placing holes higher up (shown in the picture as 7 feet), making it overhead.It would be very beneficial to include these holes on the structural drawings because it will ensure that the fabricator knows to make them, and the GC will know they are there as well.19 NISD and SEAA, Detailing Guide For Erector’s Safety & Efficiency
47Base Plates 18, 19Column Base Plates should always have at least 4 anchor rods bolted in.OSHA RequirementAs one can imagine, when the columns have no beams attached to them, they are cantilevered, and when there are many stories of building on top of the column, the base is experiencing a significant moment. This is why proper base plate practice are crucial to construction safety. OSHA requires that there be at least four anchor rods bolted into the base plate. Columns should also be made to sufficiently resist a 300 pound eccentric load increase from the column face at the top of the column during construction, per the same OSHA requirement. This will first and foremost prevent the column from falling over or “rolling over”. It will also stabilize the column, meaning that slightly less temporary bracing will be needed.19 NISD and SEAA, Detailing Guide For Erector’s Safety & Efficiency
48Beams and GirdersWorkers walk on beams to get to connections or other columns, which makes falling a common hazard. Being mindful of the following can greatly increase safety:Beam WidthUse of CantileversAbility to Support LifelinesBesides carrying the floors loads to the columns, beams and girders often serve as a transportation route on a structure, as workers walk across them to get from place to place. Making this activity safer, whether though lifelines beam properties, or general design choice, should be a large priority for those interested in PtD.
49Beam Width 18For good walking surface, use a minimum beam width of 6 inches.As stated, beams are frequently traversed to get from place to place (until decking is installed), so providing a suitable walking surface would instantly make beams safer. Use beams that have a flange width of at least six inches for suitable footing. This may, however, be difficult to implement. Due to the desirable characteristics of beam members (such as a high moment of inertia about the x-axis), most beams have taller cross-sections with flanges that are not as wide.
50Use of Cantilevers18Minimize the use of cantilevers for the following reasons:Cantilevers are not good for tying offIt is harder to make connectionCantilevers are subject to several safety issues. Look at the photograph, and look at the set of cantilevers jutting out to the left. Now imagine that columns connected to them were not there. Since the ends are just free in the air, there would be no good place to tie off, the best being the beam on which the worker would be standing. Another issue is that since cantilevers will only be connected on one end, the members are going to be very unstable when making those connections, which makes it more difficult and more dangerous for the worker. Depending on the load going on the beam, it may require more than 2 preliminary bolts to help resist the moment. It also can be difficult to connect the bottom of columns to the free end of the cantilever.
51Ability to Support Lifelines 18, 19 Design beams near or above openings to be able to support lifelines.The contract drawings should make clear how many lifelines each beam can support, and at what locations they can be attached.It is important to designate how many people can tie off at one time, since you could unintentionally overload the beam. Identifying and/or designing needed anchorage points for fall protection systems such as body harnesses and lanyards is an example of how designers can use their understanding of structural engineering principles to make it easier for workers to use fall protections systems efficiently, both during construction and future maintenance. Specifically, designers can design floor perimeter beams and beams above floor openings to support lanyards, design lanyard connection points along the beams, and note on the contract drawings which beams are designed to support lanyards, how many lanyards, and at what locations along the beams.The idea of identifying anchorage points on construction drawings is in accordance with Appendix C to Subpart M (Fall Protection) from the federal OSHA standards for Construction, though it is listed as a non-mandatory practice:(h) Tie-off considerations (1) “One of the most important aspects of personal fall protection systems is fully planning the system before it is put into use. Probably the most overlooked component is planning for suitable anchorage points. Such planning should ideally be done before the structure or building is constructed so that anchorage points can be incorporated during construction for use later for window cleaning or other building maintenance. If properly planned, these anchorage points may be used during construction, as well as afterwards.” 20
52ConnectionsConnections are very important, but they can be very difficult to install during construction.There are two main methods of making connections:BoltsWeldsConnections can be one of the most difficult parts of construction when there are issues, and people can be hurt in the process. Keep in mind that when a connection fails, there is a significant probability that the member could fall. The two primary ways of making connections is through bolting and welding.
53Bolts For safe bolted connections, consider: Self-Supporting ConnectionsDouble ConnectionsErection Aids “Dummy Holes”Bolt SizesMinimum Number of BoltsAwkward or Dangerous Connection LocationsBolts are the most common method of making connections because they are cheaper and faster than welds. Like all connections, mistakes, whether in designing or in the process of bolting, can be very costly. The next few slides present specific examples of how careful design can increase safety.21 AISC “Bolting and Welding”
54Self Supporting Connections 18, 19 Avoid hanging connectionsConsider using beam seatsHanging connections are connections made where the member “hangs” from a tab, such as in the left most pictures. As one can imagine, until that connection is set, the only thing supporting the member being connected is the choker(s) from the crane. Its counterpart, self-supporting connections are connections that are made while resting on something other then the crane. As can be see in the second and third pictures from the left, the member is resting on an angle that is working almost like a tab. A beam seat is a shelf that is put on a column so that there is a tab on which the member (currently being bolted) can rest while the bolting is being done. This extra support allows the end of the beam to rest, which makes it much more stable than when just supported by chokers, and thus easier and safer to connect.19 NISD and SEAA, Detailing Guide For Erector’s Safety & Efficiency
55Double Connections 18, 19Avoid beams of common depth connecting into the column web at the same locationIf double connections are necessary, design them to have full support during the connection process.OSHA RequirementDouble connections are a major danger on the construction site, and they are most commonly caused by beams of common depth connecting into the column web at the same location (which is why you should avoid that if possible). The problem with double connections is that they share a common bolt, so until the bolt is secured on the threaded side, it can just be pushed out. However, should one absolutely need to make a double connection, there are ways to do it safer, and each way involves securing one member without affecting the other. The first way, shown in the picture, is to attach an angle to one member only and secure the bolts on that angle first. This way, even if bolts get pushed out, it is still supported by the angle. An second way of accomplishing this is to put an extra row of holes on one side and not the other, as seen in the next slide. This way, even if the bolts get pushed out, it is still supported by the extra row.19 NISD and SEAA, Detailing Guide For Erector’s Safety & Efficiency
56Alternate Double Connection The connection has four common bolts and two that are only for one beam.
57Erection Aids “Dummy Holes” 18 Provide an extra “dummy hole” in the connection, where a spud wrench can be inserted.This is most appropriate when there are only two boltsCourtesy Bucknell University FacilitiesProviding a “dummy hole” is for erection purposes only. to avoid Erector being required to install a bolt in dummy hole. Providing a dummy hole allows a spud wrench to be inserted, keeping the member in place while the bolts are being installed. Usually a normal bolt hole could be used, but if there are only two bolts in a connection it is safer to have the dummy hole so that the spud wrench does not need to be removed with only one bolt holding the member.
58Bolt Sizes18 Use as few bolt sizes as possible It is usually cheaper to buy bolts in bulk rather than specifying a multitude of sizes to attempt to use less material or a lower strength. Additionally, if a large number of sizes is used it will result in confusion on the site as all the bolts will need to be carefully kept track of and properly installed. Should a mistake happen due to the many sizes a failure could happen, injuring workers.
59Minimum Number of Bolts 18 Use a minimum of two bolts per connectionOSHA RequirementWhile a single bolt may allow for some rotation of the member, a two bolt connection will not allow the member to rotate. Additionally, if a single bolt fails the member will still be held, and workers will not be hurt by the falling member. This will also make fixing the connection easier. It is worth noting that this includes preliminary bolting, so at no time may a member be supported by a connection with only one bolt.21 AISC “Bolting and Welding”
60Avoid Awkward or Dangerous Connection Locations 18, 19 Time-consuming and dangerousCan cause strainAttempting to bolt at awkward angles is both more time consuming and dangerous than at alternative locations. Overhead connections require the worker to strain themselves to reach it- in the top diagram the only way to get to the connection is putting a lift underneath it and working overhead. This can easily result in musculoskeletal injuries, such as a worker hurting his (or her) back.These situations can be avoiding just by thinking about how to better position the connection that will be made. In the example shown, the field connection has been moved from the overhang to the base plate, where the bolts can be installed at chest level and without needing any stretching as well.19 NISD and SEAA, Detailing Guide For Erector’s Safety & Efficiency
61WeldsWelding is when the base metal of the desired components is heated and fused together. For safe welded connections, you should consider:Avoiding Awkward or Dangerous Connection LocationsImmediate StabilityWelding LocationWelding MaterialWelding makes a connection by fusing the base metals with a filler material. Welders must go through extensive training to be able to weld in any situation, and a bad weld can be horrendous for a project. There are a few ways to ensure that the welds will be good, and safe to perform.ARC welds are common in the field, and run a current through the base metals to heat the material. MIG welding uses a gas shield and is continuously fed filler wire to make a weld. This is generally cheaper, better, and faster but can only be done with the equipment in a shop.
62Immediate Stability 18Provide pin-holed or bolted connections to provide immediate stability after placement of members.When working in the field bolts are preferable to welds. Bolted connections are stable as soon as the first two bolts are in, and secure as soon as the final bolting is done. Meanwhile, welds require more time for multiple passes to be made and during this time there is the danger of a piece getting disrupted, requiring the weld to be redone. Welds also require specific weather and temperature conditions to perform, so construction could be delayed if they are used. If a weld is improperly done there is the danger of the connection failing during construction as well.By using shop welds, this problem is avoided since the weld has been finished in a much better controlled environment, and the piece is ready for installation. The most preferable connection has a shop welded plate on a member to be field bolted.21 AISC “Bolting and Welding”
63Welding Locations 18Design to have welding performed in shop rather than in field If field welds are necessary, design should attempt to have them in convenient locationsWelding positions (i.e., flat, horizontal, vertical, or overhead) vary in their level of difficulty. Flat welds are done on top of a surface and are the easiest to perform. Horizontal and vertical welds are on the sides of a member and are more difficult since there is no support underneath. Overhead welds are the most difficult and dangerous from an ergonomic standpoint and should be avoided when possible.
64Welding Material 18Welding can be a fire hazard and can emit toxic fumes. Always be aware of what material is being welded.Welding involves melting the base metal, which requires very high temperatures. Welding can therefore be a fire hazard, especially when excess slag drops down.Also, certain material finishes should be considered when choosing a bolted or welded connection. Welding will destroy the protective coating that galvanizing provides. Galvanized steel includes zinc, which vaporizes at the temperatures used when welding. This “metal fume fever” can cause symptoms including fever, chills, thirst, headache, and nausea, lasting up to 2 days. Since airflow can be better controlled in a shop than on a job site it is advantageous to weld in shop. Also, it could be dangerous if the “metal fume fever” symptoms set in while the welder is high off the ground 22.
65Other Methods for Safer Construction Avoid Sharp CornersAccess ProblemsTemporary BracingCrane SafetyMember PlacementTripping HazardsThe following slides present miscellaneous ways to help prevent construction difficulties through design.
66Avoid Sharp Corners 19Corners can cause clothing or wires to get snagged resulting in falling objects or tripping hazards. They could also cause scratches or cuts.Sharp corners on plates can cause clothing or wires to get snagged, resulting in falling objects or tripping hazards. From an injury standpoint, a sharp corner can cause scratches or cuts. Two simple solutions are to cut off the sharp corner or to cover the corner with the bracing.19 NISD and SEAA, Detailing Guide For Erector’s Safety & Efficiency
67Access ProblemsA complicated connection will take much more time to complete, and are potentially more dangerous if they require awkward positioningProvide Enough Space for Making ConnectionsSmall Column Size AccessHand TrapConnections can become very crowded and complicated, and beyond being confusing sometimes the design makes their construction extremely difficult. These are some ways to ensure connections can be made.
68Provide Enough Space for Making Connections 19 There may not be enough space for common tools These connections can be made better by clipping away portions or increasing distancesA connection with many bolts and different members joining can be difficult to connect. The design can be complicated and confusing and every piece installed means less space for workers to maneuver with. There may not be enough space for common tools to perform well, but these connections can be made better by clipping away unnecessary portions or increasing take-off distances.19 NISD and SEAA, Detailing Guide For Erector’s Safety & Efficiency
69Small Column Size Access 19 Small column depth can make connections difficult Access to bolts can be blocked by the column flanges Attach a tab to the columnSpecial consideration must be made for small column sizes, whose depth can make connections difficult. If the depth is small enough the flanges will not allow enough space to access the bolts, or may just not allow enough space for a spud wrench to rotate. By attaching a tab to the column or supplementing with stiffener plates the connection can be moved out of the flanges and can be easily made.19 NISD and SEAA, Detailing Guide For Erector’s Safety & Efficiency
70Hand Trap 19The situation shown can create a dangerous hand trap A solution is to cut out a section of the flange to allow access to the boltsThe situation shown, with a connection made at the intersection of two existing walls, can create a dangerous hand trap. Tools will not fit in the available space, so the only possible way to connect the members is by hand. Beyond being difficult, a worker’s hand could get stuck between the wall and column. One solution is to cut out a section of the flange to allow better access to the bolts. Depending on the amount of flange removed, there could be structural implications. Therefore, the structural engineer should definitely check that the removed material will not adversely affect the structure.19 NISD and SEAA, Detailing Guide For Erector’s Safety & Efficiency
71Know Approximate Sizes of Tools 19 “Knuckle-busting” – when workers’ knuckles get damaged from trying to fit their hands into a tight spaceIf the design is too cramped workers may not be able to use proper tools, and may need to figure out a complicated and hazardous way to make the design work. Making the cramped connections can result in “knuckle busting,” where workers hands can be hurt from rubbing against connection pieces. By knowing the tool sizes used, one can design such that there will not be issues with insufficient space.19 NISD and SEAA, Detailing Guide For Erector’s Safety & Efficiency
72Crane SafetyErection will require cranes to lift members into place, which can be difficult due to the site layout.It is very useful to put the site utilities on plans to assist with crane management.It is ideal to consult with the contractor when designing for crane safety.Cranes are essential for lifting steel members into place, but depending on how crowded the site is it can be complicated to figure out where to place them. Ideally the crane could lift all members without moving and without interfering with any other operations. The biggest danger in site layout are overhead power lines. When no load is attached the crane pick can swing, and if an overhead power line is hit it will conduct the current. While it is the contractor’s responsibility to deal with power lines, the designer can help facilitate the contractor’s task by including the power line locations on the plans.
73Member Placement 19All members must have enough space to fit between columns Not enough space can lead workers to tilt columns to make it fitWhen erecting the structure, some beams will need to be lifted and placed between two columns. Sometimes, the beam is not able to be fit between the two columns without moving the columns due to the width of the beam flanges. (An extreme example to show could be a piece of paper- If you have just enough space for the piece of paper, you can not have one end connected and rotate the other side in). In some cases, the column may be tilted to make the fit, which is dangerous as it could fall over if not performed under the direction of a competent person. In order to ensure the beams can be easily swung in, this table is provided in the Detailing Guide. The larger the width:length ratio, the more impact the corners of the beam will have when trying to swing it in. The table works by giving the increase in length required for a beam with a certain width trying to fit into a certain clear space.19 NISD and SEAA, Detailing Guide For Erector’s Safety & Efficiency
74Tripping Hazards 19Avoid having connections on top of beams and joistsTripping may only result in minor embarrassment, but it could also lead to a fatality if it results in a fall from a height. The steel design can help prevent tripping by avoiding connections on top of beams and joists. If acceptable, it is preferred to have the connection plate attached to the beam being installed rather than on the lower girder. There are an infinite number of other tripping hazards, such as shear studs, random objects or moisture from the weather, so careful management and planning must be taken to not make matters worse.19 NISD and SEAA, Detailing Guide For Erector’s Safety & Efficiency
75RecapPrevention through Design is an emerging process for saving lives, time and money.PtD is the smart thing to do. PtD is right thing to do.While site safety is ultimately the contractor’s responsibility, the designer has the most power to create drawings with good constructability.There are tools and examples to facilitate Prevention through Design.
76Help make the world a safer place Perform Prevention through Design on your projects For more information please contact National Institute for Occupational Safety and Health (NIOSH)800-CDC-INFO ( ) TTY: (888) Hours/Every DayDISCLAIMER: The findings and conclusions in this presentation have not been formally reviewed by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy.
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79Citations14 Gambatese, J. A., Hinze, J., and Haas, C. T. (1997). “Tool to design for construction worker safety.” J. Archit. Eng., 3(1): 32– Daccarett, V., and T. Mrozowski. "Structural Steel Construction Process: Technical.” American Institute of Steel Construction, AISC Digital Library. Powerpoint. (2002) <http://www.aisc.org/content.aspx?id=21252> 16 Toole, T. M., and J. Gambatese. (2008). "The Trajectories of Prevention through Design in Construction.” Journal of Safety Research 30(2): "OSHA Steel Erection ETool: Structural Stability." Occupational Safety and Health Administration. <http://www. osha.gov/ SLTC/etools/steelerection/structural.html> 18 Gambatese, J. A. Design for Safety. RS Construction Industry Institute, National Institute of Steel Detailing and Steel Erectors Association of America. Detailing Guide For Erector’s Safety & Efficiency. Volume II and National Institute of Steel Detailing. Oakland, California. Steel Erectors Association of America. Greensboro, North Carolina
80Citations20 United States Department of Labor, Occupational Safety and Health Administration. Regulations Part 1926 – Safety and Health Regulations for Construction, Subpart M – Fall Safety, Standard Number 1926 Subpart M App C – Personal Fall Arrest Systems - Non-Mandatory Guidelines for Complying with (d) 21 American Institute of Steel Construction. "Bolting and Welding." AISC Digital Library. Powerpoint. (2004). <http:// 22 Sperko Engineering Services, Inc. Welding Galvanized Steel -- Safely. (1999). <http://www.sperkoengineering.com/html/ articles/WeldingGalvanized.pdf>.