Tie Rod

Tie Rod is an independent steel structural fitting widely used in concrete formwork fastening systems. It consists of rod body, threaded sections and matching fastening nuts. Each structural part undertakes separate mechanical functions, and the whole assembly can realize formwork tensioning and positioning independently without extra auxiliary parts. Carbon structural steel is used as primary raw material. According to structural styles, tie rods are divided into integral one‑piece type and assembled combined type. Integral tie rod is wholly embedded inside concrete for one‑time use. Assembled tie rod comprises middle embedded section and detachable outer threaded segments, and the outer segments can be disassembled and recycled after concrete hardening. Thread sections are mostly processed by thread rolling craft, improving surface hardness of thread teeth and enhancing wear resistance for repeated assembly and disassembly. Fastening nuts are manufactured by forging or casting processes, and their structural integrity ensures stable clamping force under lateral concrete pressure. Positioning cones and plastic sleeves can be matched to control wall thickness and simplify later surface repair work of concrete members.

Multiple surface anti‑corrosion treatments adapt to different construction environments. Hot‑dip galvanizing forms dense zinc‑iron alloy protective layers covering rod body and thread teeth. This coating resists erosion from rainwater, humid air and salt fog, suitable for long‑term outdoor and underground construction scenarios. Electro‑galvanizing produces relatively thin zinc layer on steel surface, applicable for short‑cycle construction projects with low corrosion risk. Black oxide finish applies to temporary dry‑condition projects without strict anti‑corrosion requirements. Paint finish is rarely adopted for threaded parts, because paint layers are easy to peel off under thread friction and concrete impact. Different from water stop tie rod equipped with intermediate water‑stop plate, ordinary tie rod only provides tension fastening function without built‑in waterproof structure, and is mainly applied for non‑waterproof concrete wall structures. It bears lateral expanding force generated by fresh concrete, keeps fixed gap between two formwork panels, and prevents formwork bulging and displacement in pouring process.

Core dimensional parameters determine practical mechanical performance. Rod body diameter is a critical indicator of tensile load grade, and larger diameter corresponds to higher ultimate tensile capacity. Effective rod length shall match designed wall thickness plus formwork panel thickness and on‑site operating space. Thread specification must be consistent with supporting nuts. Mismatched threads will cause poor meshing, insufficient clamping force and component slipping. This product is compatible with timber formwork, steel formwork and various combined formwork assemblies. Dimensional tolerances shall comply with corresponding international technical specifications to guarantee reliable physical fitting during on‑site assembly.

Prior to construction deployment, visual inspection and sampling mechanical tests shall be implemented as independent inspection workflows. Visual examination covers rod bending deformation, surface cracks, thread tooth damage and anti‑corrosion layer peeling. Recycled tie rod segments require stricter inspection standards. Even with intact outer appearance, invisible metal fatigue may accumulate after repeated load cycles and cannot be judged merely through surface observation. Sampling tensile tests verify ultimate bearing capacity and anti‑deformation performance. Components with permanent bending, thread slipping and structural cracks must be screened out and scrapped, and shall not be mixed into construction usage. Secondary modification operations including cutting, welding and hole‑drilling on finished tie rod are prohibited. Unauthorized alteration will change original steel section characteristics and weaken overall tensile performance of the component.

Assembled tie rod supports cyclic reuse. After concrete curing and formwork dismantling, detachable outer threaded segments can be unscrewed and recovered. Concrete mortar, dust and foreign residues attached to thread grooves need thorough cleaning before next installation. Impurities trapped inside thread gaps will cause nut jamming and interfere with normal assembling and clamping effect in subsequent service cycles. Finished components shall be stored in dry and ventilated surroundings, sorted and stacked by specification, avoiding long‑term rain soaking and direct contact with damp soil. Improper on‑site operations include selecting insufficient rod diameter, mismatching rod length with wall thickness, insufficient tightening of nuts and over‑limit load application. These improper operations may trigger formwork bulging, rod fracture and dimension deviation of concrete walls. As an independent tension‑bearing fastening unit of formwork systems, its structural integrity and mechanical stability directly affect formwork safety and concrete forming accuracy, and constitute essential preconditions for conventional concrete wall construction.