Wind load

Wind load describes the forces caused by air movement that act on structures, components, machinery, and auxiliary structures. In demolition works, deconstruction, and natural stone processing, it is a central planning factor because even short gusts can set slender components, facade elements, trapezoidal sheets, or pre-separated concrete segments in motion. Anyone working with concrete demolition shear, hydraulic splitter, hydraulic demolition shear, or steel shear must consider aerodynamic effects: they influence cutting sequences, safety concepts, bracing, and the selection of work steps across all application areas-from concrete demolition and special deconstruction through building gutting and cutting to rock excavation, tunnel construction, and natural stone extraction. Products from Darda GmbH are frequently used outdoors or in partially open buildings; here, prudent wind load management determines stability, occupational safety, and process quality.

Definition: What is meant by wind load?

Wind load refers to the total of pressure and suction forces that wind exerts on a surface. It arises from wind speed, air density, and the shape of the body being flowed around. Wind pressure acts on windward sides, suction on leeward sides and at edges; in addition, gusts can cause dynamic additional loads. Typical parameters include gust speed at the relevant working height, the terrain roughness or exposure factor, as well as shape coefficient and shielding effects. Wind loads act not only on complete structures but are especially critical for temporary construction states: free-standing wall panels, detached facade fields, exposed reinforcing meshes, beam ends, protective walls, scaffolds, auxiliary guying, and deployed tools. For design and operations, both mean wind speeds and short-duration peak values with defined averaging times are relevant.

Influencing factors and characteristic parameters of wind load

The decisive influences are:

• Wind speed and gustiness: Gusts temporarily amplify wind pressure; gust structure changes with height and topography. Turbulence intensity and gust factor determine peak actions.
• Height above ground and exposure: At roof level or at building edges, wind loads are significantly higher than at ground level; open locations promote high impact pressures.
• Geometry and shape coefficient: Large, flat elements (concrete slabs, sheet fields, formwork) exhibit a pronounced “sail” effect; slender profiles are sensitive to suction at edges.
• Temporary construction state: Partially removed components, opened envelopes, and braced single walls are more wind-sensitive than the final structure.
• Vibration excitation: Gusts and vortex shedding can excite thin-walled or slender components to noticeable vibrations.
• Shielding and channeling: Neighboring buildings, scaffolds, and openings can either shield or channel the flow, creating locally increased pressures.
• Surface porosity: Grids, meshes, and perforated sheets exhibit reduced pressure coefficients compared to closed surfaces; porosity changes with work progress.

In practice, wind load is often considered via dynamic pressure, which is proportional to the square of wind speed. For construction site practice, it is often sufficient to classify permissible operating ranges with threshold values of wind speed, supplemented by object-specific safety measures. Calculation, assessment, and documentation follow recognized rules of technology; local regulations and standards must be taken into account, complemented by a project-specific risk assessment and clear permitting processes.

Wind load in concrete demolition and special demolition

During deconstruction of high-rise structures, dismantling and cutting processes alter the flow around the object. Exposed walls, facade elements, and top-near edge fields experience increased suction and pressure forces. Wind load then acts directly on the component and indirectly on the deployed equipment. If a slab is released from the assembly with a concrete demolition shear, it can be “presented” to the wind; this increases moments in gripping arms and mounts. Demolition concepts must therefore consider wind direction, the course of the day, and possible gust lines. Lifting and transfer phases are planned with tag lines and short lever arms to reduce unintended rotation under gusts.

Concrete demolition shear: gripping, holding, and cutting under gusts

With concrete demolition shear, the gripping strategy is the focus. Pre-tensioned, full-surface gripping reduces the exposed area. Gripping points must be selected so that the released segment cannot rotate into an unstable position. Controlled reduction of slab size minimizes the wind-exposed area. In corner and edge areas, suction peaks are to be expected; there, additional securing by tie-back anchoring or intermediate supports is advisable. The cutting sequence should proceed from windward to leeward so that released edges are not unnecessarily exposed to the flow. Where feasible, keep center of gravity close to the pivot and limit free-standing time windows between cuts to minimize gust exposure.

Wind load during building gutting and cutting

In the course of building gutting, breakthroughs, opened facades, and temporary openings are created through which wind channeling can occur. Thin sheets, panels, pipelines, and ducts are sensitive to pressure surges. When using hydraulic demolition shear, combination shears, or a cutting torch, cutting sequences are planned to prevent large sail effects from arising in the first place. When a cut edge is opened, the remaining residual cross-section is stabilized or the part to be separated is fixed with holding straps and tie-back anchoring. For separation work outdoors, increased spark travel and dust drift must be expected; shielding must be constructed to be wind-resistant. Openings are temporarily closed or baffled to reduce internal pressure differences and avoid pressure shocks.

Wind load in rock excavation and tunnel construction

In rock excavation, wind loads act primarily on machines, protective devices, and exposed blocks. When using hydraulic rock and concrete splitters, large-format blocks are created along natural joints, which can be exposed after release. If blocks stand free on a bench and are subsequently moved, their orientation to the wind direction is relevant; tall, slender geometries must be secured against tipping. In tunnel construction, the outside area at the tunnel portal is wind-loaded; in addition, tunnel ventilation near the portal can lead to directed flows. Temporary installations and barriers must be designed for these flows. Transition zones between outside atmosphere and tunnel ventilation require special attention due to possible flow reversals during weather changes.

Natural stone extraction: safely handling large exposed areas

In natural stone extraction, splitting and cutting processes produce large-area slabs and blocks. When a block is released with hydraulic splitter and concrete splitter, care must be taken that it does not remain standing as a stele in the wind. Short cycles, reduced height, temporary bracing, and horizontal interim storage reduce the wind-exposed area. When transporting across exposed plateaus, lateral gusts must be considered; approach angles, turning points, and waiting areas are chosen so that no additional sail effects occur. Load orientation is selected to minimize the projected area perpendicular to the prevailing wind, and temporary edge protection prevents sliding or rocking due to gust peaks.

Special application: cutting torch and steel shear in outdoor use

Separating thin-walled tanks, silos, pipes, or steel sheets is particularly wind-sensitive. Thin sheets start oscillating even in moderate gusts and can buckle uncontrollably. Here, the cutting sequence serves as a load-guiding tool: first preserve stiffness, then release small segments. Fixed points and auxiliary beams secure residual fields against suction. If gases or vapors are expected, ventilation must be routed so that it does not create additional wind loads on thin-walled residual fields; protection radii and distances to ignition sources must be defined with care. Wind breaks, tack welds or temporary bolted connections, and tag lines reduce oscillations and stabilize residual fields until full separation.

Temporary construction states and wind stability

Temporary states are often decisive for design against wind. Opened building shells, partially gutted floors, or free-standing wall panels require tie-back anchoring, ballasting, or auxiliary frames. Hydraulic power packs and hydraulic hose line routing from Darda GmbH must also be positioned to be wind-resistant: avoid tripping and entanglement hazards due to fluttering lines, secure connections against mechanical overload caused by swinging. Scaffolds, work platforms, and protective canopies are designed for gust loads; on roofs and plateaus, edges with increased suction are particularly critical. Where necessary, temporary guying is pre-tensioned and monitored so that stiffness and damping remain sufficient during gust events.

Planning, design, and documentation

Effective wind load management begins with capturing the site climate: open or urban exposure, topographies with acceleration effects, obstacles, edges, and canyons. On this basis, thresholds for work stoppages are defined and documented in work preparation. Measurements with anemometers at relevant height, weather data, emergency routines, and release processes are part of the standard. Professional designs are carried out according to recognized technical rules and verified on a project-specific basis. The specifications in the operating manual of the equipment used must always be observed; they define safe operating limits and permissible conditions in wind.

1. Assess exposure and turbulence at working height, including shielding and channeling effects, and define monitoring locations.
2. Specify threshold values for start, pause, and stop of operations, with clear averaging intervals and gust criteria.
3. Equip the site with calibrated anemometers and implement continuous logging with time stamps for traceability.
4. Plan method statements and cutting or splitting sequences to minimize temporary sail areas and free-standing times.
5. Review and update limits and measures when geometry, exposure, or equipment changes.

Practical measures on the construction site

• Define weather windows, set threshold values, and continuously measure wind speed at working height.
• Plan cutting and splitting sequences to prevent large sail areas from arising; subdivide large elements early.
• Select gripping and attachment points so that released parts do not enter windward-leeward rotation; with concrete demolition shear, grip with full surface.
• Provide temporary tie-back anchoring, ballasting, and auxiliary frames for exposed components and install them in time.
• Treat open edges, roof edges, and corners as suction zones; provide additional securing measures there.
• Execute dust protection, spark protection, and noise control to be wind-resistant; secure shielding against fluttering.
• Secure hose and cable runs against swinging and pull-off; place hydraulic power pack in wind-sheltered zones.
• Consistently implement work stoppages when thresholds are exceeded; define responsibilities clearly and document.
• Use tag lines and short lifting radii to control components under gusts; avoid long free suspensions.
• Establish exclusion zones that consider possible drift of debris, dust, and sparks under prevailing wind.

Tool selection in the context of wind load

The choice of method influences the wind-exposed area and thus safety. In-situ crushing with a concrete pulverizer reduces the size of free-standing elements and decreases sail effects. Hydraulic splitter and concrete splitter enable controlled division of massive components or blocks before large single pieces are moved. Cutting and separation tools must be used so that remaining residual fields remain stable through their stiffness. The limits of the methods-such as heavily reinforced zones, residual stresses, or thin-walled sheets-must be planned for; additional securing or alternative cutting sequences are provided here. Selection is aligned with shortest possible exposure times and robust intermediate states that tolerate gust peaks.

Hydraulic splitter: wind-favorable sequences

Short splitting cycles, reduced component heights, and horizontal interim storage lower the wind load. Before final release, check the transport route: avoid deflections, bypass gust corridors, choose waiting areas away from the wind. Splitting wedges, cylinders, and bracing are arranged so that no undesirable torques from wind pressure arise. For benches and slopes, coordinate splitting direction with the prevailing wind to reduce projected area during handling.

Concrete demolition shear in building construction and deconstruction

Concrete demolition shear allows holding and size reduction in a single work step. In wind, set gripping arms and pivot points for short lever paths; grip as close to the center of gravity as possible. In edge zones with expected suction peaks, incremental opening of joints and immediate re-gripping with reduced exposed area is recommended. Continuous communication with lifting guidance ensures that transitions between gripping, cutting, and placing remain short and controlled even under changing gusts.

Occupational safety, organization, and responsibility

Wind is a variable influence; safe work requires clear responsibilities, training, and coordinated procedures. Operating limits are communicated in advance, interruptions initiated early. Personal protective equipment is supplemented with wind-suitable items (e.g., tight-fitting clothing, safety glasses with side shields). Legal requirements, recognized rules, and manufacturer instructions must be observed; concrete determinations are made project-specifically and depending on the situation. Toolbox briefings and dynamic risk assessments ensure that changing wind conditions are reflected promptly in work organization. This overview describes general principles and does not replace planning for individual cases.