SAVE MONEY BY USING CONSTRUCTABILITY CONCEPTS
The objective of this procedure is to make optimum use of construction knowledge and experience in planning, design, procurement, and field operations to achieve overall project objectives.
A common view of design guidelines involves only:
- Determining more efficient methods of construction after mobilization of field forces;
- Allowing construction personnel to review engineering documents periodically during the design phase;
- Assigning construction personnel to the engineering office during design; and
- A modularization of pre-assembly program.
In fact, each of these represents merely a part of the optimization process. Yet only through effective and timely integration of construction input into planning, design, and field operations will the potential benefits of optimization be achieved.
The planning/execution phases for a typical major industrial project involve conceptual engineering, detailed engineering, procurement, construction, and start up.
Construction optimization analysis should begin during the conceptual stage, at the same time as operability, reliability and maintainability considerations surface.
It can then continue through the remaining phases. Planners must recognize that the payoff for optimization analysis is greatest in the earliest phases of a project, growing progressively less, but never ceasing, until the end of the project.
In modern engineering jargon this process of design optimization is called constructability.
Constructability analysis is a form of both Value Engineering (VE) and Value Analysis (VA) that focuses mainly on the construction phase.
Constructability decisions are oriented toward:
- Reducing total construction time by creating conditions that maximize the potential for more concurrent (rather than sequential) construction, and minimize rework and wasted time;
- Reducing workhour requirements by creating conditions that promote better productivity or creating designs that demand less labor;
- Reducing cost of construction (and tools) by reducing requirements for such equipment, creating conditions that promote more efficient use of the equipment, and minimizing the need for high-cost, special purpose equipment;
- Reducing materials costs through more efficient design, use of less costly materials, and creation of conditions that minimize waste;
- Creating the safest work place possible, since safety and work efficiency go hand in hand; and
- Promoting total quality management (TQM).
Essential Elements Of Constructability
Three elements must be present if a constructability program is to realize its full potential.
Constructability must be viewed as a program that requires proactive attention. The mistaken idea that constructability is a review of designs by someone familiar with construction is totally wrong.
By the time designs are ready for review, it may be too late to change anything, and, if such changes are made, they will be costly.
Instead, individuals with a knowledge of construction must jointly participate with the other interested parties owner, engineer, operator, and maintainer- to brainstorm concepts and approaches before they are committed to a drawing.
In other words, constructability is a component of planning that must be included in all phases.
Constructability is a team effort. Only if the interests of all parties are jointly represented in all decisions will the optimum solution be realized. Reducing construction costs is certainly an important objective, but doing so must not compromise other needs.
Constructability must have management commitment and support. The time and resources needed for such a program must be made available if the program is to be a success.
A Constructability Program
While no single program will fit every program, the consensus is that most successful constructability programs have the following elements:
- Clear communication of senior management commitment to the program;
- Single-point executive sponsorship of the program;
- An established ministerial policy and program, as well as tailored implementing programs for each project;
- A ministry database compiling lessons learned and examples;
- Orientation and training as needed; and
- Active appraisal and feedback.
Constructability works best when it is an accepted part of the way an organization operates. If the subject is given enough emphasis and attention over time, it becomes ingrained within the organization reaching what it can be called a constructability culture.
Every staff person must feel part of the system, since their input is frequently sought in constructability brainstorming session and their ideas are welcome additions to the database.
The Management Approach
Recognize that startup and construction drive engineering and procurement scheduling.
- Develop a network schedule as early as possible; and
- Include engineering and procurement packages in the control schedule.
Use contracting and management approaches that promote construction efficiency.
- On engineering-procurement-construction projects executed on a fast-track basis(overlapping phases), use single management of the total effort from the outset of conceptual engineering;
- Use construction contract packages of a quality that will allow fixed-price bidding as a means of reducing or eliminating the problems associated with changes;
- Do not start on a work package until the availability of all required resources is assured (personnel, materials and support equipment.);
- Work with the owner to use any existing facilities or services rather than creating duplicate ones for the construction period;
- When packaging designs for specialty subcontracting, consider normal jurisdictional lines so that packages logically fit the specialty contractors involved an do not require sub-tier subcontracting;Plan the release of contracts to take advantage of favorable construction weather;
- Provide adequate planning time for contractors and subcontractors in the bidding-award process;
- Keep the control schedule at a summary level;
- Ensure that project milestones are reasonably attainable considering both construction and procurement time;
- Do not impose unnecessary hold points for quality checks;
- Keep requirements for owner involvement in the project(such as reviews and approval) to a minimum;
- Issue instrumentation, piping and insulation packages as early as possible, since these require the most field time to execute;
- Use a contract form that incorporates incentives designed to reduce construction costs. For example, include Value engineering (value analysis) clauses that provide for sharing in savings engendered by adopting cost improvement suggestions made by the contractor;
Ensure that project requirements and conditions are understood.
- Make certain that field conditions are accurately reflected on design documents;
- Identify all access routes and any limitations on their use;
- Be sure that all parties understand their roles and responsibilities with regard to providing equipment, the use of project areas and facilities, security and gate control, administrative policies, etc;
- Identify disposal areas for excavations, vegetation, non-hazardous waste and hazardous waste; and
- If working in or adjacent to an operating facility, identify all constraints that the situation presents.
Emphasize standardization and repetition.
- Standardization and repetition maximize application of the learning curve to the work force, permit volume buying of materials, and simplify purchasing and warehousing.
- Standardize structural members, foundations, bolt sizes, and other components as much as possible;
- Dimension concrete components to take advantage of readily available commercial form sizes;
- Repeat designs throughout the facility. This will reduce design costs while promoting the learning curve effect during construction;
Take maximum advantage of readily available, off-the-shelf materials and components.
- Maintain access to commercial catalogs of equipment and materials;
- Make maximum use of vendor representatives to assist in item selection;
- Survey the area to determine which materials are most readily available locally;
- Require procurement specialists to publish bulletin on a regular basis, identifying materials and items in short supply on the world market and approximating order-ship-deliver lead times of all equipment and materials regularly used in the contractor work; and
- Consider using pre-engineered structures in lieu of specially designed structures.
Choose configurations that facilitate or simplify handling and erection.
- Require design engineers to develop recommended construction methods and include them with the design. This will force them to think constructability;
- When designing steel members and connection, remember that erection is much easier if a member to be connected to another can be temporarily positioned on top of the in-place member or on a pre-installed seat on that member before bolting or welding;
- Take advantage of modularization. Vendor-assembled modules are produce under more favorable conditions than those in the field. This ensure better quality while reducing field erection time;
- Use designs that employ pre-cast concrete components which can be cast in a controlled environment, delivered to the project when needed without intermediate handling, and directly installed;
- Avoid components that require special care and handling in the field;
- Create designs that do not require special care and handling in the field;
- Include special foundations in the design o structures for mounting climbing cranes and elevators if such equipment will be used during construction;
- Locate heavy and/or bulky items within structures so that as many as possible can be hoisted from a single location of the lifting equipment;
- Maximize the use of straight runs and perpendicular tie; avoid curves(particularly complex curves) and angles;
- Consider limitations of standard transport and lifting equipment when designing components. If necessary, design over-size items so they can be fabricated, transported and erected in parts;
- Use designs that minimize the need for temporary structures such as forming, shoring, bracing, and tie-downs;
- For multiple electrical and piping systems, consider using common utility tunnels or conduits through which multiple system can be installed (and easily removed or expanded later if necessary) rather than using direct embedment or multiple conduits;
- For multiple foundations in the same are, establish the same bottom elevation for all foundation so that excavation can be handled on a mass basis rather that individually;
- Design engineered items so that they can be dressed out on the ground for installation. In other words, design any components that cross several items(such as ladders or raceways) so portions of them can be pre-assembled with the engineered item to create a module;
- Design electrical/instrumentation connections with plug-in configurations rather than a labor-intensive connection;
- For complex wiring networks, specify the use of wiring harnesses that are factory assembled and coded;
- In lieu of cast-in-place reinforced walls, consider using the lift-slab technique;
- On multi-storied buildings with reinforced concrete floors, consider casting the floors one at a time on the lower deck and lifting them into position. This will eliminate many bracing and scaffolding requirements;
- In lieu of specifying concrete block wall using conventional masonry techniques(mortar between blocks), specify simple stacking of blocks followed by plastering of both sides with fiber-reinforced mortar. The result is a better-looking, stronger wall that can be constructed more quickly by less skilled personnel;
- When designing connections for hydraulic or other systems, create unique designs for each category of connection to avoid any potential for connection mixups in the field;
- When designing or specifying large components (such as vessels or rotating equipment), include lifting hooks or other handling devices/features in the design so field erectors will not have to improvise the rigging and handling;
- Provide designs for special measuring devices, templates, or other erection aids that may be useful for aligning or achieving tolerances;
Create designs that promote accessibility and provide adequate space for construction personnel, material, and equipment.
- Consider interstitial designs for buildings. This means providing space above all operating floors that is zoned for various operating systems. The vertical clearance in this space should be enough to allow for easy movement of workers. This design greatly simplifies construction, and facilitates future maintenance and upgrading;
- Locate electrical pull boxes with adequate space around them to simplify cable pulling;
- Size pipe racks to allow easy addition of new lines;
- Incorporate access openings in both exterior and interior walls;
- Provide for reasonable working space around all installed components;
Adapt designs and strategies to project location and time.
- In an area with a very short construction season or limited labor availability, make maximum use of factory-assembled modules and components that have been designed for rapid assembly;
- Consider local labor and specialty contracting capabilities;
- Select designs that best use these capabilities, since they will be less costly than imported capabilities;
- If the local population lacks needed skills, maximize the use of remote, off-site fabrication;
- In a union environment, consider jurisdictional rules and wage scales when selecting a design approach;
- Avoid designs whose construction is particularly weather sensitive;
- Avoid the use of materials expected to be in short supply or subject to unusual price inflation during the duration of the project;
Use realistic specifications.
- Do not require unnecessarily tight tolerances. For example, the imposition of ASTM or nuclear-quality specifications on ordinary construction can be overkill;
- Do not specify an expensive, hard-to-install material when another is far more economical. for example, PVC conduit is lighter, more flexible, and easier to work with than rigid conduit;
- Designers must learn to challenge each specification. Is it the best for the project at hand?;
- Maximize the use of performance rather than proprietary or descriptive specifications to five grater feasibility to the field;
- Minimize the number of specifications applying to the same type of work, such as concrete, bolt sizes, etc.;
- Consider field installation costs in the economic evaluation of material or equipment choices;
- Include in the specification file information on where and why a given specification is applicable. This will assist engineers in selecting the best specification for the job at hand;
- Maintain and continually update a file of lessons learned from previous projects. Make these the subject of training sessions;
- When possible, allow for alternates in case the primary method or item is not achievable;
- Include requirements for packing and shipping critical items that assure undamaged delivery of them;
- Specify testing methods and procedures that are reasonable for the field;
Assure quality and completeness of design deliverables (such as drawing and specifications).
- Be willing to hire outside expertise when the in-house staff does not have the talent or time needed to prepare quality deliverables;
- Establish a complete system of reviews and checks to ensure accuracy of dimensions, compatibility of drawings and specifications, and consistency of flow diagrams, piping and instrumentation diagrams, etc.;
- Use physical or computer models to be sure there are no interference among systems;
Incorporate safety in designs.
- Specify locations where beams and columns should be drilled to accommodate safety cables; and
- Design components to facilitate pre-assembly on the ground and lifting into final position in modular form.
Plan and develop the site to promote worker efficiency.
- Use cardboard cutouts that have been cut to scale to represent temporary construction facilities on an overall map of the site drawn to the same scale; brainstorm the best layout of the site to support construction;
- Provide for dust control on roads;
- Develop and stabilize all heavily used foot traffic areas around the construction site;
- Design the construction road network to isolate administrative traffic from traffic that directly supports construction activity;
- If space permits, develop a perimeter road around the site. This will help prevent traffic congestion and interference;
- Design laydown areas as a series of alternating roads and narrow laydown pads that allow any item in the laydown area to be handled using lifting equipment on the adjacent road;
- Shape all laydown areas for drainage, and construct a supporting drainage network. Stabilize surfaces where material will be placed and spray them with weed killer or cover them with plastic sheeting to prevent grass and weed growth. Make cribbing available for off-ground placement of materials;
- Do not allow long-term storage of any materials adjacent to a facility under construction. Leave clear space around its perimeter that is available for construction equipment and pre-positioning of materials needed for current work activity;
- Locate smoke- and dust-producing activities downwind from the center of construction activity;
- Locate/relocate portable facilities to minimize travel distances from worker concentrations;
- Regularly clean up an remove construction debris and garbage from work areas;
- Schedule work shifts to minimize interference with local traffic patterns and to avoid excessively hot portions of the day;
- Establish grids for construction electrical, gas, water and compressed air service with distribution points in convenient locations. Design connection trees that are modular and can be moved from distribution point to distribution point as needed;
- Have portable lighting sets available to illuminate work areas where natural illumination is poor;
Perform work when and where it is most efficiently accomplished.
- Complicated process equipment is often best assembled in modules at a factory, requiring only positioning and connecting at the project site. This takes advantage of the factory environment, which generally has more skilled workers, better productivity, and better working conditions. Pay scales also may be more favorable. Module assembly can be accomplished in parallel with other construction work, which permits field construction schedules to be shortened;
- On-site prefabrication yards for forms, steel cages, and piping spools allow such work to be accomplished under the best conditions and, look for the yards to be weather-protected to allow work to continue during inclement weather;
- Work on the ground can be accomplished more efficiently and safely than in the air. For example, insulated components can be at least partially insulated while on the ground, with only the finish work left for the air;
- During construction of multi-level structures, pre-position installed equipment and other materials on the various levels as decks are completed to avoid later problems of access;
- In a congested area where multiple piping and electrical systems are competing for space, install the heavier, bulky components firsts, leaving the lighter, more flexible items for last;
- When building construction roads, include non-drainage culverts and ducts where future utility lines are expected to be located so that roads will not be cut up later to accommodate laying these lines;
- Fabricate like components, such as rebar cages, on an assembly line basis;
- Allow materials to be delivered to the site only during off-shift hours;
Minimize unscheduled and unproductive activity.
- Use detailed work package planning and adopt a philosophy of never starting on a work package until personnel, materials, and equipment availability is assured;
- Use separate crews for materials pickup and spotting at the point of use to keep the supervisor with the crew;
- Obtain old trailers to use in picking up and positioning materials to be used by crews. Materials can be moved directly from the trailers to the point of placement, thus eliminating multiple handling;
- To avoid the inevitable productivity degradation associated with rework due to changes, use a special crew within each craft to handle rework, thereby allowing the primary crew to move on to other first-time work;
- If special equipment, such as heavy cranes, must be rented to support certain phases of a project, concentrate the scheduling of work requiring this equipment into as short a time span as possible;
- Use bar codes or other codes to identify materials in storage. This will speed up identification time;
- For critical layouts, use two separate survey crews, each starting from the primary benchmark, to lay out construction. This will minimize the potential for layout errors;
- When storing materials in a laydown area, store them in order of retrieval. This will minimize damage and loss associated with handling and re-handling;
- Paint distinguishing marks (such as a North arrow or Top) on components to facilitate their final positioning. This will eliminate lost time due to misplacement;
- Assign laydown areas by discipline;
- Place tool boxes, tool rooms, parts lockers, etc. on wheels or skids to permit their relocation as work moves. Install lifting hooks on them so they can be handled with cranes;
- Use bar coding and computerized inventory control to speed tool issuance. This is even more effective if employee ID badges have a bar code so that the employees accessing the tools can be quickly identified;
- Consider using just-in-time materials deliveries from suppliers to eliminate the cost and effort of intermediate storage and handling;
- Employ work-saving tools/equipment and modern construction techniques.
- It is impossible to keep up with the market, since new and better technology is always introduced. Ask vendors to demonstrate their equipment. They are usually receptive to providing training as well;
- Use automatic welding machines, nail guns, cordless tools, laser levelers, craftsman stilts, etc.;
- Use commercially available material items designed to speed the construction process. for example, commercial forms are available for concrete work, and a complete family of high chairs, clips and other gadgets can speed the placement and tying of resteel. Comparable items are available for carpentry, electrical, and other work;
- Have a representative of the organization attend trade shows to learn what is on the market. Bring back literature and make it available to those with a need to know. Consider making a video tape using scenes from a trade fair or pictures from brochures with appropriate narrative, and distribute this video among the staff;
- Subscribe to trade publications, which contain many advertisements describing innovative products. Prepare a scrapbook of those with the most potential and make it available to the staff;
- Cut out articles from trade and other publications that describe innovate techniques used by competitors. Compile them in a scrapbook that is available to the staff;
Sequence work for optimum efficiency.
When the facility to be built includes repeated designs, try to schedule work on repeated elements in series to take advantage of the learning curve;
- Pre-position and temporarily lash heavy and/or bulky components within a structure when access is most favorable;
- On large concrete slabs, pour sections in checkerboard fashion to reduce the need for forms;
- Hold stairs and platforms early so they can be used in lieu of scaffolding and elevators;
- Schedule construction activity around the weather. For example, some building may be erected early to provide protected work space for later construction;
- With owner concurrence, construct selected permanent facilities early and use them for construction support;
Employ construction practices that emphasize safety.
- Erect stair towers early so they may be used for access during construction;
- Use remotely-activated release devices on rigging equipment so workers will no have to be hoisted to release them manually from equipment lifted into place;
- Have safety equipment vendors demonstrate available state-of-art safety equipment and provide any training needed;
- Install safety lines and other safety devices on structural members before they are lifted into position;
Employ Value Engineering principles to solve field problems.
- Describe the goal in terms of a verb and a noum (Example: move materials);
- Identify all options possible;
- Evaluate all options, eliminate those not practical, and make a short list of options with most potential;
- Evaluate the remaining options in detail;
- Select the best option;