Through-Wall Bolt

A through-wall bolt(also known as a through-bolt or anchor bolt)is a type of fastener designed to penetrate entirely through a structure(e.g.,walls,slabs,or panels)to secure objects on both sides.Unlike surface-mounted anchors,it provides bidirectional load transfer,making it ideal for heavy-duty applications requiring high pull-out and shear strength.

Key Features&Components

Material:

Typically made of carbon steel(Grade 5 or 8),stainless steel(304/316 for corrosion resistance),or hot-dip galvanized steel.

Design:

Threaded Shaft:Fully or partially threaded for nut fixation.

Sleeve/Washer System:Includes washers,sleeves,or spacers to distribute load and prevent crushing of brittle materials.

Head Types:Hex head,countersunk,or custom designs for flush mounting.

Load Capacity:

Designed to withstand tensile(pull-out)and shear(lateral)forces.

Capacities range from 10 kN to over 100 kN,depending on diameter and embedding material.

Types of Through-Wall Bolts

Mechanical Expansion Bolts:

Use sleeves that expand against the wall under torque for grip.

Example:Wedge anchors,sleeve anchors.

Chemical Anchors:

Inject epoxy resin into drilled holes for adhesion-based bonding.

Use:High-load applications in cracked concrete or hollow materials.

Through-Bolt Kits:

Include long bolts,nuts,washers,and sleeves for modular assembly.

Example:Hollow-wall anchors(e.g.,for masonry or drywall).

Seismic Through-Bolts:

Engineered for dynamic loads in earthquake-prone regions.

Applications

Structural Steelwork:Connecting beams,columns,or brackets to concrete/masonry.

Facade Systems:Mounting cladding,sunshades,or signage to building envelopes.

MEP Installations:Securing pipes,ducts,or equipment to walls/ceilings.

Civil Infrastructure:Bridge railings,tunnel fixtures,and retaining walls.

Installation Process

Drilling:Create a hole through the entire structure using a diamond-core or rotary hammer drill.

Cleaning:Remove dust and debris from the hole(critical for chemical anchors).

Insertion:Place the bolt through the object and the wall.

Fastening:Tighten the nut on the opposite side to achieve design torque.

Curing:For chemical anchors,allow resin to harden before loading.

Advantages

Bidirectional Load Transfer:Distributes stress evenly across the structure.

Versatility:Suitable for concrete,masonry,brick,and composite materials.

Reusability:Mechanical bolts can often be removed and reinstalled.

High Reliability:Minimal risk of pull-out under vibration or dynamic loads.

Limitations

Complex Installation:Requires precise drilling and alignment.

Material Damage:Penetration may compromise waterproofing or insulation if not sealed.

Corrosion Risk:Uncoated steel bolts rust in damp environments.

Technical Standards

ASTM F1554:Standard for anchor bolts used in structural applications.

EN 1992-4:European design rules for fastenings in concrete.

IBC/OSHA Compliance:Required for seismic and wind-load regions.

Selection Criteria

Load Requirements:Calculate tensile/shear forces and safety factors.

Substrate Material:Choose bolts compatible with concrete strength,hollow walls,etc.

Environmental Conditions:Opt for stainless steel or galvanized bolts outdoors.

Accessibility:Ensure tools and space exist for installation.

Safety Notes

Inspection:Check for cracks,corrosion,or deformation before use.

Torque Control:Use calibrated tools to avoid under/over-tightening.

Sealing:Apply waterproofing(e.g.,silicone)around penetrations in exterior walls.

Conclusion

The through-wall bolt is a robust fastening solution for critical structural and non-structural connections.Its ability to transfer loads through entire assemblies makes it indispensable in construction,infrastructure,and industrial projects.Proper selection,installation,and maintenance are essential to ensure safety and longevity.