SINGAPORE INSTITUTE OF ARCHITECTS (SIA) Design-for-Safety (DfS) Handbook

Transcription

1 01. In this pocket guide we seek to provide a simple, step-by-step approach to Design-for- Safety (DfS) in accordance with the DfS principles presented in the WSH Council s Guidelines to Design for Safety in Buildings & Structures. A project s DfS exercise should aim at invoking a systematic and disciplined approach to giving attention to risks borne out of the design of a building. DfS draws upon the professional pride and moral duty of designers to be responsible in the designs they prepare. In seeking to optimise the effectiveness of the DfS process, it is intended to be applied as an integral and natural part of the normal design process. The DfS process should be aimed at promoting effective and creative outcomes which are meaningful and to-the-point. The DfS process should avoid overly contrived, tedious and onerous procedures which are counter-productive. The DfS process is not intended to create paperwork for its own sake, nor to breed resentment by becoming a demoralising burden of formality. The DfS process should encourage willing involvement and creative contributions by designers. 02. The key objectives of DfS are : 1. the avoidance or mitigation of risks arising from the design of the building, and 2. the awareness of affected persons of (i) significant risks arising from the building development that they will need to face and address, and (ii) safety measures provided in the building development that they can make use of to address the safety risks they face. Affected persons are those who are affected by the building (including those persons who construct, alter, demolish, occupy, or maintain the building, or persons who visit or are proximate to the building). Different sets of affected persons exist at the different stages of a building development s life (ie construction, use/occupancy/maintenance/alteration, and decommissioning and demolition), and each stage should be considered for DfS purposes. 03. We approach DfS in regard to two principal design exercises: 1. Selection of Site. 2. Design of the building development. 04. For selection of Site, the safety-feasibility of a proposed Site should be determined. Page 1 of 13

2 The safety-feasibility should comprise the acceptability of the proposed Site relative to tolerances for safety risks. The safety feasibility should consider: (a) The safety-risk-impact of the proposed type and scale of building development on the surrounding context. (b) The safety-risk-impact of the surrounding context on the proposed type and scale of building development. (c) The safety-risk-impact of the existing Site conditions and dimensions on the proposed type and scale of building development. 05. For design of the building development: (1) the significant risks of a proposed design for the building development should be determined, and (2) opportunities to design-in safety measures should be identified and taken.. The affected persons need to be made aware of significant risks and the safety measures relevant to them. The significant risks are those which: #1. Are not a commonly encountered and understood risks, and require special methodology to address the risks, and #2. Are not obvious to the risk-facer, and #3. Are of a significant severity level (eg debilitating or fatal injury or illness). 06. In identifying significant risks, the designer(s) should seek to describe the risk/hazard in terms of: > Affected Person > Activity / Task -- eg specific type of construction or maintenance work > Risk Source -- eg working at height > Conditions of Risk Exposure eg difficulty of access to work > Kind of Accident / Harm eg injury or death from falling 07. The building s significant risks and the opportunities for safety measures are identified through DESIGN REVIEW by the building s designers. Design Review involves: Page 2 of 13

3 (A) looking at the proposed building design, (B) at different stages of design development, (C) from different perspectives, in order to brainstorm for significant risks and opportunities for safety measures. Identified significant risks should be assessed, and the risk omitted or risk level reduced where possible. 08. Design Review should be conducted at the various stages of design development (before and during construction), such as: (i) Concept Design (ii) Schematic Design (iii) Development Control (DC) Plans (iv) Developed Design (v) Building Plans (BP) (vi) Working Drawings and Specifications and Preliminaries (for tender/pricing and construction) (vii) Shop Drawings and Method Statements [by contractors ie throughout the construction stage] Design Review should be carried out on: (a) designs for the Permanent Works (b) designs for temporary facilities (eg show flats) (c) designs for Temporary Works and work approach/methodology (d) design revisions to (a)-(c). Design Review should include for: (i) designs by the Architect. (ii) related designs by other consultant designers (iii) related designs by specialist contractors (iv) related designs by general/trade contractors 09. Note that the Architect is part of a team of designers who should consider various modes of design in a coordinated manner, including: (i) Site selection. (ii) Design of the permanent works (building development, including Site planning). - by principal designers (including architects, engineers and other consultants) Page 3 of 13

4 (iii) (iv) - by specialist design-&-install contractors Design (including selection or prescription) of temporary works. - by principal designers (including architects, engineers and other consultants) - by contractors Design (including selection or prescription) of the approach and methodology of work. - by principal designers (including architects, engineers and other consultants) - by contractors 10. Design Review should involve examination of all modes of design information that represents the design, including: (a) BIM models / architectural drawings, (b) Schedules / tables of data (c) Specifications, annotations and legends (d) Preliminaries, site management specifications, etc. (e) Physical models, artists impressions and 3D images. (f) Mock-ups, prototypes and materials samples. (g) Product literature / brochures 11. Brainstorming should be carried out with the permutations of the following considerations in the back of the designer s mind (A) Design Review should involve examination of the design information from different perspectives, such as: (a) Building elements (b) Building materials (c) Layouts, configurations, dimensions and proportions (d) Scale (Site, Building, Rooms/Spaces, Elements, Components) (e) Work approaches & methods. (B) Design Review should consider the various different modes of hazard / accidents, such as those outlined in Appendix The modes of hazard / accidents, such as those outlined in Appendix 1 can be seen as having the following underlying factors: Page 4 of 13

5 'RISK SOURCE: > Access > Ergonomics / Restricted Space > Material / substance > Objects > Tools & Method > Environmental CONDITIONS OF RISK EXPOSURE: for example... > Working at height > Restricted working space > Concealed working space > Flame / Heat > Thermal comfort > Light levels > Air quality > Pollutants 13. Some typical activities (ie modes of work) under which affected persons might be exposed to risk includes, but is not limited to: Construction (& A&A): -Transport / Delivery - Offload at Site - Storage on Site - Positioning / Lifting - Related Temporary Works - Installation - Testing & Commissioning - Cleaning Maintenance: - Servicing & Repairs & Cleaning - Replacement / Reapply / Renewal Page 5 of 13

6 14. Any significant risks that were not avoided in the initial designing should be identified and assessed, and the risk eliminated or reduced where possible (to achieve an acceptable level of residual risk, within established tolerances):. First priority is to change the relevant aspect of the design to eliminate the significant risk. Second priority is to change the relevant aspect of the design to reduce the significant risk, in order of preference: 1. by substitution with a different design, 2. with an engineered design solution (passive), 3. with an engineered design solution (active) eg built-in provisions for application of task-specific tools/equipment and processes, 4. by mitigating the risk level with application of administrative controls or 5. by mitigating the risk level with application of personal protective equipment (PPE). This process should consider risk v. benefits v. practicable alternatives. This process gives a conscious, deliberate, systematic and disciplined approach to DfS. 15. The affected persons need to be made aware of significant risks and the safety measures relevant to them. This is most effectively done by adding safety advisory notes to the design information that the affected persons will refer to. For example: (1) Advisory notes for construction workers is best integrated in the working drawings, shop drawings, specifications, method statements, etc to which they are referring in the course of their works. (2) Advisory notes for maintenance personnel is best integrated in the as-built drawings and/or operating procedure statements/instructions in operation & maintenance manuals. The advisory notes specifically seek to make affected persons aware of the significant risks they must address and the safety measures available to them in the course of their activities. Page 6 of 13

7 Advisory notes should: (A) Be placed as mark-ups on the actual design information so it is prominently highlighted and readily apparent to the affected person in the course of their activity (it should not be put in a separate document that is non-specific and detached, as these are usually put away on a shelf and collect dust). (B) Be clear and succinct, and preferably of a graphic mode (eg pictograms) which are effective for their ease of reading and understanding. 16. As a supplement to the advisory notes, the designer should also consider conducting briefing sessions for affected persons to verify that they have realised and understand the risks that are highlighted in the advisory notes. Such briefing sessions are best conducted at the time of passing-on the design information (and advisory notes ) to the affected person. Page 7 of 13

8 APPENDIX 1: - Modes of Hazards / Accidents The designers should keep the following modes of hazards / accident in mind when brainstorming to identify risks: According to MOM statistics, the most-occurring accidents in relation to construction works are 1. Falling from height 2. Struck by objects (moving objects) 3. Struck by objects (falling objects) 4. Caught in-between Objects 5. Collapse / Toppling Equipment (both Temporary and Permanent equipment) 6. Collapse / Toppling of Structure (load resisting elements, including Soil/Rock -- both Temporary and Permanent structures) 7. Slips, Trips and Falls A wide scheme of hazards / accidents would consider: RISK AGAINST SAFETY (INCL. HEALTH & WELL-BEING), relative to 'design objective' and 'design approach / solution' : ACCESS - Falling from height - Trapped or Confined Space (enclosed with limited access and/or egress / emergency exit) OBJECTS - Struck by objects (moving objects) - Struck by objects (falling objects) - Caught in-between Objects - Cut / stabbed by Objects - Strike against Objects - Stepping on Objects - Lifting or Manoeuvring Injury TOOLS / EQUIPMENT & METHOD / PROCESS - Collapse / Toppling Equipment (both Temporary and Permanent equipment) - Mechanical Injury - Ergonomic / Strain Injury - Tool Breakage / Failure - Tool 'give-offs' (dust, grit, splinters, fumes, noise, sparks, flame, heat, vibration, etc) - Electrocution - Heat / Thermal Injury Page 8 of 13

9 PHYSICAL CONTEXT - Collapse / Toppling of Structure (load resisting elements, including Soil/Rock) (both Temporary and Permanent structures) - Slips, Trips and Falls - Glare / Reflection ERGONOMICS - Over exertion / strenuous movement - Restricted / Awkward Movement Space - Lighting - Ventilation / Air Quality HAZARDOUS MATERIALS / SUBSTANCES [incl in solid, liquid or gas, and as smoke, dust, mist, fumes (gas / vapour)] Exposure to Harmful Substances - Toxic / Poisonous - Asphyxiating - Allergenic - Explosive - Flammable - Corrosive - Oxidising - Radioactive Exposure to Biological Materials - Infectious / Biological Hazard (Pathogen) OPERATION / ACTIVITY - Electrocution - Exposure to extreme temperatures - Fire - Explosion - Drowning - Mechanical / Impact Injury ENVIRONMENTAL CONTEXT - Sanitation/hygiene - Pests / Infestations - Thermal Comfort - Noise Pollution - Smells / Odors - Sun / Glare - Rain - Wind - Lightning - Psychological Disturbance Page 9 of 13

10 ACTIVITY CONTEXT - Traffic Accident - Anti-social behaviour EMERGENCY SITUATION (Response & Preparedness: Escape / Refuge, Containment, Fighting / Arresting, etc) - Fire - Natural Disaster (Earthquake, Precipitation / Flood, Wind) - Violence / Disorderly Conduct - Biological, Chemical or Radiological Threat - Explosion / Bomb Threat - Vehicle Crash - Disease Outbreak - Health / Hygiene Threat Page 10 of 13

11 APPENDIX 2 - Design Review topics In conducting Design Review to identify risks, the designers can consider the following topics (as arrange here under the GUIDE 1, 2 & 3 classification of design review provided in the WSHC DfS Guidelines): > GUIDE 1 - Site Selection Site Feasibility Analysis - Impact on Site / Development by existing surroundings - Impact on Site / Development by environmental factors - Impact of Site / Development on surroundings/public - Existing Site Conditions - Conceptual/Schematic Site Planning - Constraints & Opportunities - Feasibility of Construction Operations & Site Management - Adjacent Structures - Ground / Soil Conditions > GUIDE 2 - Site Design Schematic / DC - Impact on Site / Development by existing surroundings - Impact on Site / Development by environmental factors - Impact of Site / Development on surroundings/public - Existing Site Conditions - Conceptual/Schematic Site Planning - Constraints & Opportunities - Feasibility of Construction Operations & Site Management Developed / BP - Adjacent Structures - Ground / Soil Conditions > GUIDE 2 - Detailed Design & GUIDE 3 - (i) Specialist Contractor Designs Schematic / DC Planning - Design of Permanent Works - Layouts / Configurations & Spatial use/function Developed / BP - Design of Permanent Works & Temp Facilities - Site Formation - Design of Permanent Works & Temp Facilities - Underground Services - Design of Permanent Works & Temp Facilities - Sub-Structure - Design of Permanent Works & Temp Facilities - Building Super-Structure & External Works Structures - Design of Permanent Works & Temp Facilities - Building Envelope - Design of Permanent Works & Temp Facilities - Internal & External Assemblies, Systems & Plant (Arch + M&E) Page 11 of 13

12 Developed / BP &/or Construction Contract Documentation - Design of Permanent Works & Temp Facilities - Materials, Fixtures & Detailing (Arch + M&E) - Design of Permanent Works - General Design Function Specialist Contractor: D&B Documentation Specialist Contractor: Shop Dwgs, Materials Selections & Method Statements > GUIDE 3 - (ii) Design of Temporary Works [for Construction] Types of Temporary Works & Approach to Methodology : Employer/ Consultant Design - Prescription/specification of Site Arrangements, Facilities and Scheduling requirements - Interim Works for Site Arrangements & Facilities Types of Temporary Works & Approach to Methodology : Contractor's Design - Interim Works for Site Arrangements & Facilities - Interim Works for construction of Permanent Works Page 12 of 13

13 APPENDIX 3 - PROJECT LIFE STAGE / STAKEHOLDER ACTIVITY MODE > Site Selection (Analysis of feasibility for the proposed development with respect to Safety & Health) (Stakeholders: Generally, as per the following project stages). > Before-Construction (Site Upkeep and Investigations / Surveys) (Stakeholders: Owner, Developer, Consultants, Surveyors and Investigators, Preliminary Works Contractors, General Public) > Construction (Stakeholders: Contractors, Employer & Consultants, Site Supervision Staff, Visitors & Inspectors, General Public) (Note: Excludes off-site manufacture, prefabrication and assessmbly, etc)... MOBILISATION / SITE SET-UP... DEMOLITION... SITE CLEARANCE... EARTHWORKS... EXCAVATION... SUB-STRUCTURE... SUPER-STRUCTURE & EXTERNAL WORKS... BUILDING ENVELOPE... ASSEMBLIES, SYSTEMS & PLANT (ARCHI & MEP)... FINISHES & FIXTURES... DEFECTS RECTIFICATION > Occupancy - Use (Stakeholders: Occupants & Visitors & Inspectors, Service Providers, General Public) > Occupancy - Maintenance (Stakeholders: Property Managers & Maintenance Contractors, General Public) > Additions & Alterations (Stakeholders: as above, for Construction + Use) > Decommissioning and Demolition (Stakeholders: as for Construction) Page 13 of 13