Installation and Usage Guide for Aluminum Formwork Large Diagonal Braces

From Zero Foundation to Safe and Efficient Construction

Preface

For construction workers who are new to aluminum alloy formwork systems, the large diagonal brace (also known as the diagonal brace rod or adjustable diagonal prop) may be one of the most "troublesome" yet critically important components. The large diagonal brace is the core structural member that ensures the verticality, flatness, and overall stability of aluminum formwork wall panels, and directly affects the quality of concrete forming and construction safety.

This guide uses plain language and intuitive step-by-step instructions to help users with no prior experience quickly master the installation and operation of large diagonal braces.

I. What Is a Large Diagonal Brace and What Does It Do?

Simple Analogy:

A large diagonal brace is like the guy rope of a tent. Without it, the tent collapses in the wind; without the large diagonal brace, the aluminum formwork wall panel will be pushed out of plumb or even collapse under the enormous lateral pressure during concrete placement.

Technical Principle:

One end of the large diagonal brace connects to the back waler (or formwork rib plate) of the aluminum formwork wall panel, while the other end is anchored to the floor slab below. By adjusting the length of the diagonal brace, the verticality of the wall panel is corrected while simultaneously resisting the lateral pressure generated during concrete placement.

Core Functions:

• Verticality Adjustment: Through telescopic adjustment, the wall panel is maintained at 90° perpendicular to the floor.
• Lateral Pressure Resistance: Prevents the wall panel from bulging outward or shifting laterally during concrete placement.
• Anti-Flotation and Anti-Overturning: Prevents the formwork from floating upward or tipping over as a whole.

II. Components of a Large Diagonal Brace

A standard large diagonal brace assembly consists of the following components:

Beginner's Tip: Upon receiving the large diagonal brace, manually rotate the adjusting turnbuckle by hand to get a feel for the extension/retraction directions. Typically, turning clockwise shortens the brace and counterclockwise lengthens it (this may vary; verify with the actual component).

III. Installation Procedure for Large Diagonal Braces

Preparatory Work

• Tools: Tape measure, spirit level (or plumb bob/total station), wrench, chalk
• Inspection: Verify that the large diagonal brace is free from bending or deformation, the turnbuckle rotates smoothly, and all connecting pins are present.
• Note: The floor slab must have already hardened and reached sufficient strength, and the rebar chairs must be pre-embedded in place.

Step 1: Determine the Diagonal Brace Installation Positions (i.e., Rebar Chair Positions)

Basic Rules:

• Single wall panel length ≤ 1.6 m: Install at least 2 sets of diagonal braces per wall panel face.
• Placement: No more than 600 mm from the wall end, with equal spacing in between; brace spacing ≤ 2,000 mm.
• Diagonal braces shall be arranged symmetrically on both sides of the shear wall panel.
• The centerline of each rebar chair shall be approximately 1.2 m from the wall edge, avoiding conduits embedded in the slab surface.

Step 2: Fix the Bottom of the Diagonal Brace (Floor End)

• Hook the bent-hook right-hand-thread bolt onto the rebar chair.
• Tighten the conical nut until the rebar cannot be pulled out of the hook.
• Critical Check: Confirm that the hook opening is closed and the rebar chair cannot disengage.

Common Error: Forgetting to tighten the conical nut, causing the diagonal brace to detach from the rebar chair. Always ensure the conical nut is fully tightened.

Step 3: Connect the Top of the Diagonal Brace (Wall Panel End)

Prerequisite:

The aluminum formwork wall panels must be fully assembled and provisionally positioned, and the square hollow section tube (transverse stiffening tube) must already be installed.

• Insert the locking pin at the top of the diagonal brace into the edge rib hole of the wall formwork.
• Insert the pin clip and drive it tight.
• Check: Ensure the included angle between the long tube of the diagonal brace and the floor is 45°–55°, and the included angle between the short tube and the floor is 10°–15°.

Beginner's Technique: If the brace length does not allow the pin to align with the hole, do not force the formwork panel. Instead, adjust the turnbuckle to change the brace length so that the connection bracket aligns naturally.

Step 4: Preliminary Adjustment of All Diagonal Braces

Following the sequence of "center first, then ends," adjust all diagonal braces to a state where they are "just bearing without applying force." At this point, the wall panel is approximately in position but fine adjustment of verticality has not yet been performed.

Step 5: Fine Adjustment of Verticality (Critical Operation)

This is the most patience-demanding step in the entire construction process.

Typical Procedure (using a single wall panel as an example):

1. Hang a plumb bob at each end of the wall panel (or use a 2-meter straightedge with spirit level).
2. Read the deviation — for example: the top of the wall panel is leaning outward by 5 mm.
3. Adjustment Principle: Whichever direction the wall panel leans, tighten the diagonal brace on the opposite side.

• If the top of the wall panel leans outward → tighten (extend) the inner diagonal brace.
• If the top of the wall panel leans inward → loosen (shorten) the outer diagonal brace.
• 4. Rotate the turnbuckle only 1–2 turns at a time, then re-measure, gradually converging on the target.
• 5. Once both ends are plumb, check whether the middle of the wall surface is flat (using a straightedge); if any unevenness exists, adjust the middle diagonal braces.

Practical Rhyme:

"Top leans out — extend and push; top leans in — shorten and pull.

One turn, two turns, take it slow; measure and adjust, don’t rush to go."

Step 6: Lock and Re-inspect

1. Once verticality is within tolerance, tighten the locking nut on each diagonal brace.
2. Re-measure with a spirit level or straightedge to confirm no displacement has occurred due to the tightening action.
3. Shake each diagonal brace by hand — it must be completely rigid with no movement.

IV. Key Precautions During Use (Safety First)

✅ Mandatory Requirements

❌ Strictly Prohibited Actions

• Never use diagonal braces to forcibly "pull" or "push" a wall panel that has already been cast (adjustments may only be made before the concrete reaches initial set).
• Never install diagonal braces on one side only (unless the other end of the wall panel has sufficiently rigid support).
• Never remove diagonal braces prematurely (removal is only permitted after concrete strength reaches ≥ 75% of the design value, generally ≥ 48 hours after casting).
• Never hang heavy objects from diagonal braces or use them as a climbing ladder.
• Never cut or weld diagonal brace components without authorization.

V. Quick-Reference Troubleshooting Guide

VI. Removal and Maintenance

Removal Sequence (Reverse of Installation)

• Confirm that the concrete strength has reached the required value.
• First loosen the locking nut, then rotate the turnbuckle to relieve the load on the diagonal brace.
• Remove the pin clip from the top of the diagonal brace, allow the locking pin to withdraw from the hole, and detach the diagonal brace.
• Remove the bottom of the diagonal brace: first loosen the conical nut to disengage the bent hook from the rebar chair.
• Finally, cut out and remove the rebar chair.

Routine Maintenance Points

• After each use, remove all cement residue from the diagonal brace (especially the turnbuckle threads).
• Check monthly whether the turnbuckle and nut engagement is smooth; apply machine oil promptly to prevent rust.
• If the main pipe is found to be bent or deformed by more than 1/500 of its length, or shows visible cracking → take it out of service immediately.
• Pin clips are consumable parts; any that are lost or deformed must be replaced immediately.

VII. Operation Rhyme for Zero-Experience Teams (Recommended for Posting on Site)

Before installation: Check all components, clear the floor, embed rebar chair

During fixing: Anchor the base, set the angle, arrange symmetrically

During adjustment: Loosen the lock first, rotate slowly, measure and adjust simultaneously

Before placement: Full re-inspection, tighten locking nuts, no movement when shaken

During removal: Wait for strength, relieve load first, then remove base anchors

Keep in mind: Diagonal braces are tough, but safety comes first — never be careless!

Conclusion

Large diagonal braces may look like nothing more than a few iron rods, but within the aluminum formwork system they play the role of the "anchor of stability." For users with no prior experience, do not be intimidated by what may seem like complex operations — follow the four-step cycle of "Measure → Adjust → Lock → Re-inspect" with sufficient patience, and you will be proficient after two or three hands-on sessions.

If you encounter special situations not covered in this guide during actual use (such as non-rectangular wall panels, extra-high floors, or complex site conditions), be sure to consult the project’s technical lead or contact the aluminum formwork manufacturer’s technical support. Never take risks based on experience alone.

Safety is never a minor matter — every brace and every rod bears a thousand kilograms of responsibility.