How Lean Design And Lean Construction Can Partner For The Best Results – Cập nhật kiến thức mới nhất năm 2024
Diễn đàn duy nhất dành cho toàn ngành, đa lĩnh vực để tìm kiếm và chia sẻ kiến thức về quy hoạch, thiết kế, kiến trúc, cơ khí, công nghệ thông tin, công nghệ xây dựng và vận hành các tài sản được xây dựng.
Between January 2012 and early 2014, more than 500 Indian migrant workers and 382 Nepalese died in Qatar performing construction work connected to the 2022 World Cup. Zaha Hadid, the architect who designed the Al-Wakrah stadium, declared:
“I have nothing to do with the workers. I think that’s an issue the government – if there’s a problem – should pick up. Hopefully, these things will be resolved.” Asked if she was concerned, she added “Yes – I’m not taking it lightly, but I think it’s for the government to look to take care of. It’s not my duty as an architect to look at it. I cannot do anything about it because I have no power to do anything about it. I think it’s a problem anywhere in the world.” (The Guardian, James Riach, 25 Feb 2014)
Ms. Hadid was roundly criticized for this opinion, but with the fragmentation of the building industry – especially the separation between the What (Design) and the How (Building) – some designers might agree with that statement. How can lean practices bring these two together? Lean building methods and the Last Planner System® were first introduced into the construction phase, where productivity specialists studied weekly plans at jobsites and determined that only 54% of tasks were ever completed as scheduled. Their original purpose was not a reaction to safety issues. Rather, how could “Last Planners” – typically foremen responsible for directing work onsite and assigning manpower and materials – work together to better sequence the work and handoffs between trades for a more productive work week?
Teams on Last Planner projects later realized that safety incidents had been greatly reduced compared to non-Last Planner projects. Many believe that this is due to the increase in “planned” work and fewer surprises from unexpected constraints. If you are told in the morning to install lights in the lobby, but you were planning on working in the classrooms, you may not have the right ladder size. Do you try to find the taller ladder, or do you “make do?” But what if you already planned last week where you would be working today?
One enterprising contractor noticed a peculiar coincidence when researching his company’s jobsite safety incidents. While the nature of each accident appeared unrelated, the description of these incidents usually began with these words: “I was planning to do X today, but then Y happened, so I directed my crew to do Z.” Unplanned work often became unsafe work, so the superintendent asked foremen to carry work plan books in their pockets. When something unexpected happened, foremen were asked to write down the new task, decide how the work was to be done, and include a safety plan before proceeding. Through this effort, they decreased both quality issues and safety incidents.
If better planning your workflow results in safer and more high-quality work, what happens when you concentrate on making work safe first? There is a false assumption common to many industries that safety and lower costs exist in opposition to each other – but is that actually true? When Paul O’Neill took over as CEO for the aluminum manufacturing company Alcoa, it already had a safety record superior to others in the industry. He announced that his primary goal would be ensuring zero injuries. His team deduced that things go wrong because of an insufficient understanding of how to make the process right. He insisted that within 24 hours of anyone getting hurt, or even having a close call, the business unit president had to notify O’Neill wherever he was in the world.
Within two days, they had to report what the initial investigation had revealed about the root causes and what would be done to prevent the problem from recurring. Leaders were required to solve problems and spread knowledge. Skeptics initially concerned about the cost of this new program soon observed improvements in quality, yield, defects, efficiency, cost, stock prices, and profits. Reviewing safety had opened a window into all the underlying factors that compromised Alcoa’s performance in those typical corporate measures (High Velocity Edge, Steven Spear). Work flows were redesigned, equipment was upgraded, and better work methods promoted throughout the company.
Lean and the Last Planner System concentrate efforts first on making workflow. Last Planner started with the collaborative creation of weekly work plans, and expanded to daily huddles (to ensure the weekly work plans are followed), phase planning (to ensure milestones are reached in the best manner for everyone), and make ready planning (ensuring when tasks reach the weekly work plan, they are not constrained). The last level of the Last Planner System that Lean practitioners began to study was milestone scheduling – a part of master planning that includes not just construction, but the design phase as well.
Prevention Through Design
Design is the ultimate exercise in “planning” work, and therefore should have a close connection to safety on the jobsite – consider the claim that 22-60% of all construction accidents originate in design (John Gambatese, Oregon State University). It is difficult to trace all accidents back to their origin, but it is worth considering how a contractor falling from a roof may have been better protected if the construction of the project had been better thought-out at the beginning of design, when nearly all changes are still possible. The design can dictate (or at least suggest) the sequence of construction, how work gets done, what materials get used, how easy it is to access different areas, and what equipment is required. Without input from operations in the field, dangerous conditions, ergonomically unsound practices, and missed opportunities for streamlining design abound, along with the usual annoyance of incomplete documents. As constructability suffers, quality will also be at risk. The harder the design is to build, the more expensive as well – and the larger the threat to the schedule; this dynamic motivates the trades onsite to speed work up in ways that may be dangerous to life and limb in addition to quality.
Unfortunately, designers often don’t consider the construction implications of their designs when issues should be obvious. Consider the problem of installing and replacing light fixtures over stairwells or in high, inaccessible places. As an architect placing lights on a Reflected Ceiling Plan, I seldom thought about anything but aesthetics. The lighting engineer finalized the plan with the proper calculations. I rarely saw builders installing lights, and only heard vague complaints during weekly Construction Administration walks. But as a quick survey of Google Images shows, builders get dangerously creative trying to install the work as shown in the design documents.
As an architect with typically little builder input in design, I picked up complaints at random. For example, within our public recreation centers, we often used 8×16 CMU walls for durability. To add some interest, we asked for center scoring on these walls in certain locations to imitate an 8×8 grid. Occasionally, I would make a notation in the documents for this center scoring on both sides of the same CMU wall. This caused real heartburn with alignment. “Please don’t put center scoring on both sides of a wall – we have been fighting it all day!” One CM exclaimed. If he hadn’t experienced this issue the day I appeared onsite, I may have never heard about it. If my firm hadn’t had weekly staff meetings on Monday, I may have never informed any of the other project architects. If we wish to properly design and plan our work, this ad hoc system is not the way to do it!
When it comes to safety on site, most of us commonly tend to think of (and rely on) Personal Protective Equipment (PPE). But while necessary, this is actually the least effective method for keeping workers safe. At least half of contractors questioned by researchers identified design as a factor that negatively affected health and safety on site. The National Institute for Occupational Safety and Health has created the following diagram to rank which practices create the safest designs to build. The most effective strategy is to eliminate the hazard entirely.
What would that look like for an architect and his project team?
According to OSHA, most fatal accidents involve falls, being struck by objects, or being caught between objects, including unsafe access. Eliminating risks by changing the design and avoiding features that create these hazards is key. We should provide safe, permanent access for construction, operations and maintenance, consider offsite prefabrication where many trades must work in the same space, understand access needs and exposure to falls, and determine easier methods of construction at the beginning of design, when it is easiest and cheapest to study and incorporate alternatives.
Last Planner efforts have been shown to decrease safety incidents, but these efforts are usually concentrated in the last two hazard categories – Administrative Controls and PPE – where safety controls are least effective. New Lean design practices that bring contractors and trades into the earliest phases of design, such as Target Value Delivery (TVD) and Set-Based Design, offer the perfect structure for eliminating or replacing traditional hazards. Cross-functional teams can be formed to discuss various construction systems, including the placement and orientation of equipment to permit safe access, installation, and maintenance. What dimensions are required for access? What kind of supports, sequences, and connections are required? What surrounding exposures must be mitigated? Prefabrication and modularization can dramatically reduce construction injuries over “stick-built” construction, but these opportunities must be planned in the initial stages of design; constructability reviews that start after the 30% design stage have significantly lower potential for designing facilities that are easier and safer to construct (Gambatese).
Designing with a better understanding of the building process would make our projects easier and safer to construct, increase quality, decrease the schedule, and lower costs. All of this would allow designers to keep more of the features they love. Cross functional teams working within the TVD framework can be formed to study and propose alternatives for the main scopes of work that comprise 80% of costs: Exterior skin and fenestration, mechanical, electrical, plumbing, and structure. Set-based design can be used to produce, explore, and select the best alternatives for each scope. Everyone in the building industry would benefit, but how do we begin?
A New Approach to Design
We can start by considering common problems project teams face every day and finding ways to improve the process of design and construction to avoid these issues in the future. Recently, a builder was constructing a YMCA recreation facility with a structure that combined precast and CMU walls topped by steel joists with metal decking for the second floor and roof. The steel structure was connected to the walls by a confusing combination of steel embeds and plates that were often incorrectly located and had to be removed and replaced after a lengthy RFI process. From the number of mistakes in the layout of these embeds, it seemed clear that the design itself was confusing for the wall manufacturers. It was also difficult for the contractors to determine that these embeds were in the wrong location in the first place until they were already in the process of building the structure and had to stop. As designed, the composition certainly withstood all the required forces established by the structural calculations, but it was very difficult to build, impacting the schedule and with it, quality.
The structural engineer was periodically onsite and helpful when it came to answering questions, but didn’t have much experience in building facilities of this type. Luckily, the same design team and builder were scheduled to create a second facility nearby; the designers and superintendent improved the second design in time to build the new recreation center with fewer problems. It is rare that we get such an opportunity, but enterprising designers and superintendents can find their own ways to improve new design projects by taking the time to examine what builders found difficult about previous projects.
Cost issues can also be resolved by working together. An architectural team working in the Design Development phase for a new university building was faced with multiple rounds of “value engineering” (scope cutting) for the mechanical system. Every time they revised their drawings, they were again informed by the GC (after another week or three of waiting) that they were still $200,000 over budget. Having brought in at least three mechanical sub-contractors at various times for pricing (trying the trades’ patience, no doubt), they asked the owner if they could simply pick one of these subs to design the system within cost. The owner was a public entity, but since they had costs from 3 separate trade companies already, they agreed to allow an early selection. The design team asked the selected trade if they could help design the system below “$X” psf. The installer had little issue complying with this request. If the team had continued designing in the traditional manner, they would no doubt be “value engineering” even after 100% Construction Documents were issued.
Mechanical systems are often overdesigned, and therefore more expensive and harder to operate than they need to be. Architects don’t always ask many questions of their engineers – we are too busy trying to coordinate how to accommodate the ducts through the building structure. It makes sense that incorporating installer expertise up front would be a great advantage. Due to time pressures, some architects complain that they don’t have time to incorporate such expertise up front, but endless iterations to make components “fit” takes a lot of time and energy. If the actual installer places the final system as they plan to install it in a BIM model, the team can enjoy the added benefit that this design can be approved immediately by the architect and engineer, avoiding the submittal process entirely. How much time and aggravation would this save? Especially for architects, who never reserve enough fees for Construction Administration.
Even if some contractors aren’t usually involved in the design phase, design often spills over into construction as documents require changes. Changes that must be understood by the architect, redesigned, explored with multiple engineers, approved by the Owner, and priced before proceeding. Owners may balk at hiring trades upfront, believing in spite of all evidence that hard bidding projects gives them the best value. Architects are obliged to shorten design schedules, as owners mistakenly believe that quickly moving past design into construction will decrease the overall schedule.
Go Slow to Go Fast
How can we reimagine the design process to harness the entire project team’s expertise to create innovative projects, fit for purpose and for the best value? Consider how far a design team with builders could go when designing a multi-story tower with a steel structure. The structural cluster would consist of a cross-functional group including the architect, structural engineer, owner representatives for facility operations, and the steel erector. This group would review the design for constructability, beginning with a draft of the possible construction sequence. A safer, easier design might start with fewer construction steps, fewer components, standard elements, and lighter members for ease of handling. Connections could be welded in the shop instead of in the field.
Steel columns should safely stand on their own, providing temporary stability during construction. Column splices should be placed at a height between the average worker’s hips and shoulders for ease of installation. Holes in the flanges should be placed at the correct height to accommodate safety railings, and cross-bracing should be designed with rungs for ease of climbing. Permanent or temporary platforms can also be included for ease of erection and maintenance, and seats should ideally be provided for beams for ease of placement. Safe lifting points for structural members are key. How do you safely lift members in place, and can you use small batching to bring to the site just those members slated for timely installation, with information directing where each batch will be installed? A typical concrete column detail might ensure that the rebar sits on the concrete foundation instead of being spliced above the floor so that the rebar is also supported during construction. Connection points like sockets, brackets, and inserts can be placed to attach edge protection, including netting for floors and roofs. The team can plan to pour a hard, landscaped area immediately as construction begins for better lay space and a firmer footing for workers.
If we truly regard design and construction as one industry and act accordingly, we would plan our work using the collaboration necessary to recreate the “Master Builder” of yore. Specialists must work together to safely provide the innovation owners demand at the best price. By focusing on Quality in both design and construction, we can improve the schedule, costs, and scope of projects without compromising design features or the wellbeing of those who build them.
Ngoài các bài viết tin tức, bài báo hàng ngày của https://kythuatcongnghiep.com/, nguồn nội dung cũng bao gồm các bài viết từ các cộng tác viên chuyên gia đầu ngành về chuỗi kiến thức kỹ thuật, công nghệ xây dựng, cơ khí, kiến trúc và kiến thức quản lý, phát triển tổ chức doanh nghiệp,.. được chia sẽ chủ yếu từ nhiều khía cạnh liên quan chuỗi kiến thức này.
Bạn có thể dành thời gian để xem thêm các chuyên mục nội dung chính với các bài viết tư vấn, chia sẻ mới nhất, các tin tức gần đây từ chuyên gia và đối tác của Chúng tôi. Cuối cùng, với các kiến thức chia sẻ của bài viết, hy vọng góp phần nào kiến thức hỗ trợ cho độc giả tốt hơn trong hoạt động nghề nghiệp cá nhân!
* Ý kiến được trình bày trong bài viết này là của tác giả khách mời và không nhất thiết phải là https://kythuatcongnghiep.com/. Nhân viên tác giả, cộng tác viên biên tập sẽ được liệt kê bên cuối bài viết.
Các chuyên mục nội dung liên quan
- Bản tin số mới nhất | Góc chia sẻ kiến thức xây dựng & Kiến trúc và công nghệ xây dựng
- Trang chủ
- Xây dựng & Kiến trúc