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Instruction Manual for HILTI models including: HUS4-MAX, HUS4-MAX Bonded Screw Anchor, Bonded Screw Anchor, Screw Anchor, Anchor
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DocumentDocumentPOST-INSTALLED BONDED SCREW ANCHOR, AN INNOVATIVE TECHNOLOGY Advantages, Application and Design Version 2.0 January 2025 Post-installed Bonded Screw Anchor, an Innovative Technology TABLE OF CONTENTS 1. Introduction 2 2. Post-installed anchors the advantage of a combined system 3 2.1 Post-installed mechanical and bonded anchors 3 2.2 Difference between post-installed mechanical and bonded anchors 3 3. Bonded screw anchor HUS4-MAX 4 3.1 Understanding the bonded screw system 4 3.2 How to install HUS4-MAX system 5 4. Regulatory framework and qualification 6 5. Design method as per EN 1992-4 and EOTA TR 075 7 5.1 Design verification against static loading as per EN 1992-4 7 5.2 Combined pull-out and concrete cone failure as per EOTA TR 075 8 5.3 Design verification against seismic loading 10 5.4 Design verification against fire loading 10 6. Design Examples 10 6.1 Design example against static loading 10 6.2 Design example against seismic loading 12 7. Advantages of using HUS4-MAX for suitable applications 13 8. Conclusion 14 9. References 15 1 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology 1. INTRODUCTION Fastening technology is becoming increasingly important in civil structural engineering worldwide, seeing widespread use in connecting a large variety of structural and non-structural components. Anchors can be grouped into cast-in mechanical, post-installed mechanical, or post-installed bonded systems, with the choice of system depending upon a specific application's load and durability demands. Appropriate selection, design and on-site execution of post-installed anchors becomes crucial to help mitigate the risk of accidents or structural failures that may cause damage to life, property or equipment. At Hilti, we aim to combine better specifications and jobsite practices. For the engineer, our solutions help make specifications higher performing and value engineered while, for the contractor, they help make jobsite practices faster, simpler, safer and more sustainable. Drawing many years' expertise and a passion for innovation, we are excited to share our latest innovation and technology. This article presents a novel technology for anchoring in post-installed steel-to-concrete fastenings: the bonded screw anchor Hilti HUS4-MAX. This hybrid anchor system utilizes the properties of both mechanical and bonded anchors, where the mechanical component is a Hilti HUS4 concrete screw and the bonded component is a Hilti HUS4-MAX capsule (polymer resin, hardener and aggregates in a defined mix ratio). This article describes the working principle of hybrid anchors (Chapter 3), the regulatory framework and qualification as per EAD 332795 [1] (Chapter 4), detailed design methods according to latest EOTA TR 075 [2] in collaboration with EN 1992-4 [3] (Chapter 5), design examples (using PROFIS Engineering software) (Chapter 6), and advantages of bonded screw anchors for various applications (Chapter 7). The article provides guidance to engineers involved in designing post-installed bonded screw anchors for steel-to-concrete fastenings. Furthermore, it is also useful for contractors and their in-house technical teams, as well as others who are directly or indirectly associated with such fastening applications. Fig. 1.1: HUS4-MAX for steel-to-concrete baseplate application 2 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology 2. POST-INSTALLED ANCHORS THE ADVANTAGE OF A COMBINED SYSTEM 2.1 Post-installed mechanical and bonded anchors The load-transfer mechanisms for various fastening systems are typically identified as mechanical interlock, friction and adhesive bond mechanisms. Post-installed anchors transfer load from the baseplate to the concrete through different working principles. They may be broadly classified as mechanical and bonded anchors. Mechanical anchors derive their strength from principles like friction and keying between steel and concrete. On the other hand, bonded anchors derive their strength from the bond along the interfaces between steel-adhesive and adhesive-concrete. The first category includes expansion anchors (e.g. Hilti HST3), drop-in anchors (e.g. Hilti HKD), undercut anchors (e.g. Hilti HDA) and concrete screws (e.g. Hilti HUS4). The second one includes capsule anchor systems (e.g. Hilti HVU2) and injection systems (e.g. Hilti HIT-RE 500 V4). Given the large variety of anchor systems available on the market today, design or installation professionals may find it difficult to select the appropriate anchor for a specific application. The most appropriate fastening system should be selected by considering jobsite and construction conditions, since individual systems have inherently different characteristics, advantages and drawbacks depending on the application requirements. 2.2 Difference between post-installed mechanical and bonded anchors The main criteria to consider before choosing between post-installed mechanical and bonded anchors (depending on the jobsite requirement and design conditions) are shown in Table 2.1. Table 2.1: Key points for proper selection of anchors Working principle Anchor loading conditions Edge and spacing requirement Base material condition Hole cleaning Water tightness Embedment depth Installation and inservice temperature Creep behavior Mechanical anchor Mechanical interlock or friction Immediately Large edge and spacing distance (except screw and undercut fasteners) Strong and stable base material that can withstand the installation forces Less sensitive to intensity of hole cleaning Not fit for use in water-filled concrete Limited variation in embedment depths Not relevant Not relevant Chemical anchor Bonding Require certain curing time to be loaded fully Suitable for smaller edge and spacing distances Suitable also for low-strength base material More sensitive to intensity of hole cleaning Water tightness is ensured by some approved systems Flexibility of embedment including larger and variable embedments More sensitive to high temperature Significant effect due to sustained load Due to the contrasting advantages and drawbacks of mechanical and chemical anchors, there is a demand for an anchoring technology which can combine the benefits of both mechanical and chemical anchors, i.e. the latter's higher performance in terms of load resistance, edge distance and spacing, with the former's installation simplicity and productivity. 3 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology Hilti bonded screw anchors, obtained by combining HUS4 screws with HUS4-MAX chemical capsules, achieve this because they benefit from the dual action of both mechanical undercutting and the effect of chemical technologies through a hybrid solution. 3. BONDED SCREW ANCHOR HUS4-MAX The bonded screw anchor HUS4-MAX is a hybrid system that uses a concrete screw (anchoring system based on mechanical interlock or undercut) and a chemical system (anchoring based on adhesion and micro-keying). The bonded screw anchoring system employs a concrete screw alongside a foil capsule filled with two components bonding material. The capsule contains a polymer resin, hardener and aggregates in a defined mix ratio. The mechanical screw element helps to create a secure hold within concrete, whereas the adhesive component surrounding the screw enhances the anchor's stability and load bearing capacity. 3.1 Understanding the bonded screw system To enable a better understanding of the bonded screw anchor and the benefits of combining mechanical bonded anchors, the following situation can be observed: if the polymer/mortar was completely removed, the residual anchoring system would be a pure concrete screw transferring the load by mechanical interlock via the thread cut into the walls of the borehole (Fig. 3.1). Conversely, the conditions which negatively influence the bond behavior, for example borehole cleaning, temperature of the base material, sustained loads, etc. are mitigated by the concrete screw. On the other hand, the load carrying behavior of the screw anchor is dependent on the borehole tolerances, which may weaken the interlock mechanism, especially when concrete is cracked in instances such as seismic conditions. This sensitivity is reduced by the presence of the adhesive mortars between the threads. The Hilti HUS4 screw used with a HUS4-MAX capsule is not as sensitive to the unfavorable parameters which are in general valid for bonded and screw anchor systems. However, this is only possible if the combination of thread geometry and characteristics of the adhesives are balanced as exemplified by the Hilti HUS4 screw with HUS4-MAX capsule and validated by the qualification tests as per EAD 332795 [1] (see Section 4). a) HUS4 screw anchor with HUS4-MAX capsule b) HUS4 screw in concrete after removal of mortar Fig. 3.1: Condition assuming removal of mortar from HUS4-MAX anchor If only the mechanical HUS4 screw anchor is embedded in concrete, the load transfer occurs as shown in Fig. 3.2. The screw transfers the load to the concrete through the mechanical interaction between its threads and the concrete. The thread portion of screw is more vulnerable due to stress concentration at the tip. The load-carrying mechanism is based on the balancing of external tension force, N, with the local bearing pressure between the threads and the concrete, R, along the embedment. 4 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology Note: Please refer to Instructions for use (IFU) for more details regarding installation a) HUS4 anchor under tension load b) Enlarged view of interaction between threads and concrete Fig. 3.2: Load transfer mechanism for HUS4 screw anchor The use of capsule HUS4-MAX with the screw helps to distribute the stress through a bond mechanism and can provide better resistance than only a screw anchor. Hence, the HUS4-MAX anchors can help mitigate the risk of generating peak stress in threads and variables affecting mechanical behavior, such as concrete quality. 3.2 How to install HUS4-MAX system The Hilti HUS4-MAX is installed in the following way: Preparation: a hole of the appropriate size and depth is drilled into the base material by hammer drilling using a suitable drill bit. Placing of capsule: the HUS4-MAX capsule is placed in the drilled hole. Insertion: the anchor is then inserted into the drilled hole using an impact screwdriver. When driving the concrete screw into the hole, the foil capsule is shredded but also compressed. The resin hardener and aggregates are mixed and the annular gap around the concrete screw and the thread cut into the wall is filled with the polymer matrix, also filling eventual cracks in the concrete. The quantity of the polymer materials in the foil capsule is specifically selected to fill the borehole without pouring out. Chemical bonding: the resin capsule bonds with the surrounding material, enhancing the anchor's resistance and stability. a) Drilling of borehole b) Placing of HUS4-MAX capsule c) Insertion of screws d) HUS4-MAX is installed Fig. 3.3: Installation of HUS4 MAX anchor with capsule 5 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology 4. REGULATORY FRAMEWORK AND QUALIFICATION The qualification of post-installed anchors refers to the process of evaluating their performance and suitability for a specific application. The qualification of anchors depends on multiple steps/processes: manufacturer's documentation, third-party testing, quality control and environmental considerations. The essential characteristics of the product are included in the European Technical Assessment (ETA) and used in the design as per EN 1992-4 [3] or the applicable Technical Report (TR) issued by the European Organization for Technical Assessment (EOTA). The qualification of post-installed anchors described in this chapter is based on EOTA EADs. Since bonded screw anchors function differently to purely mechanical or bonded systems, they can neither be assessed according to EAD 330499 [4], used to assess chemical anchors, because the external thread diameter of the steel element is larger than the drill hole diameter, nor according to EAD 330232 [5], which deals with the assessment of mechanical anchors due to differences in specific essential characteristics such as combined pull-out and concrete failure and influence of sustained load 0. Therefore, this requires a new qualification process and a specific design method. The new EAD 332795 [1] has been introduced to cover the assessment of post-installed bonded screw anchors. The assessment criteria (Table 4.1) for a bonded screw anchor considers robustness aspects relevant for mechanical and bonded anchors. The performance is based on the concrete, screw performance and mortar combination. Table 4.1: Different parameters covered in EAD 332795 Parameter Minimum diameter Minimum and maximum embedment depth Installation temperature Design working life Base material Minimum thickness of base material Sensitivity to installation conditions Environmental conditions Loading types Description 6 mm 40 mm and 200 -40°C to +40°C 50 years Concrete strength C20/25 to C50/60 Uncracked and cracked concrete = 1.5 , 80 and (1 + ) Drilling method Drill hole cleaning Installation direction (vertical downward/upward and horizontal) Minimum edge distance and spacing Minimum curing time Freeze and thaw cycles In-service temperature High alkalinity and sulfurous atmosphere Hydrogen embrittlement Sustained load Seismic category C1 and C2 Characteristic displacements Values for short- and long-term loadings In the new EAD 332795 [1], the contributions of a mechanical concrete screw as per EAD 330232 [5] and bonding material as per EAD 330499 [4] are considered and the combined effect is assessed. The test 6 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology program contained within allows a detailed assessment of the essential characteristics of the product for all the potential failure modes, which are then published in the ETA of the related product. A fire resistance test is carried out and designed in a way that only the contribution of mechanical part is considered. The contribution of bond material is negligible and steel failure is decisive. Hence, EAD does not foresee the possibility to test the contribution of bond material. The presence of bonding material can compensate for the potential wear of the screw thread at the tip after installation, ensuring the load transfer now occurs at the deepest embedment point, which is different to simple concrete screws, for which the effective embedment depth is usually reduced following the provisions of EN 1992-4 [3]. To verify this, tests must be performed to check if the effective embedment depth used for the calculations of the concrete cone capacity (and related failure modes) can be considered equal to the nominal embedment of the fastener (usually the full length of the fastener) or if an intermediate value between the nominal one and the reduced embedment defined for concrete screws should be considered. Table 4.2: Essential characteristics and qualification criteria in EADs Load Static / quasi static Essential Technical characteristic parameters Relevant EAD Concrete pullout / combined failure Characteristic resistance, concrete influence, sustained load Concrete cone Effective failure embedment Installation Minimum concrete member thickness Temperature range Sensitivity to installation Curing time Seismic Pull-out / combined failure C1/C2 Pull-out or Fire combined failure Characteristic resistance, concrete influence, sustained load Characteristic resistance R30 to R120 Mechanical anchors EAD 330232 , , Bonded screw anchors EAD 332795 Bonded anchors EAD 330499 ,,/ , , 0 , 100, 0 = 0.85 ( - 0.5 - ) 80 = 0.85 ( - 0.5 - ) 80 = (80 , 1.5 (80 , 1.5 2) 2 , 1 + ) (100 , + ) T1 (-40°C to +80°C) Not required T1 (-40°C to +40°C) Required to be tested, however, it can be set zero if tests are performed immediately after setting T1 (-40°C to +40°C) varies depending on the bonding material ,, ,,/, ,, 0 ,, ,,, ,, 0, 5. DESIGN METHOD AS PER EN 1992-4 AND EOTA TR 075 5.1 Design verification against static loading as per EN 1992-4 Design verifications in EN 1992-4 [3] for static tension and shear loads are defined separately considering all relevant failure modes for post-installed anchors. In general, the calculation of resistances for bonded 7 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology screw anchors against failure modes except combined pull-out and concrete cone follow the equations given in EN 1992-4 [3]. The design criteria against pull-out failure for mechanical anchors and combined pull-out and concrete cone failure for bonded anchors are separately defined. Pull-out resistance of mechanical screw anchors: the characteristic resistance for mechanical screw anchors 0, is considered from the product relevant ETA. Combined pull-out and concrete cone resistance of bonded anchors: the equations of EN 1992-4 [3], which define the characteristic resistance to this failure mode for bonded anchors, use the characteristic bond strength () as the main input for determining the characteristic tensile resistance 0, of the anchor. However, EN 1992-4 [3] does not provide design instructions against combined pull-out and concrete cone failure specific to bonded screw anchors. For this reason, a new Technical Report issued by EOTA, the TR 075 [2], has been developed. This document provides the necessary adaptations of the design method proposed in the EN 1992-4 [3], according to the new parameters defined and assessed via the EAD 332795 [1]. The summary of design resistances for each failure mode is defined in Table 5.1 and Table 5.2. Table 5.1: Design scope in EN 1992-4 against tension loading Failure mode Steel failure of anchor Concrete cone failure Combined concrete cone and pull-out failure Scope in EN 1992-4 , value is given in the relevant ETA. , = 0, , 0, , , , , Mechanical anchors: , (taken from the relevant ETA) Bonded anchors: , = 0, , 0, , , , , Remarks No clear definition for bonded screw anchor is given in EN 1992-4. Refer to EOTA TR 075 for updated design considerations Table 5.2: Design scope in EN 1992-4 against shear loading Failure mode Steel failure of anchor without lever arm Concrete pry-out failure Concrete edge failure Scope in EN 1992-4 Remarks , value is given in the relevant ETA. Mechanical anchor: V, = 8 , , = 0, , 0, , , , , , , for bonded screw anchor is considered only for mechanical screw part 5.2 Combined pull-out and concrete cone failure as per EOTA TR 075 The resistance against combined pull-out and concrete cone failure for bonded screw anchors is detailed in EOTA TR 075 [2] and depends on the resistance of screw anchor as well as the property of bonding material. The combined resistance: the characteristic combined pull-out and concrete cone resistance, ,,/ for a group of bonded screw anchors is derived by calculating the resistance values of the screw anchor and bonding element separately and then the group effect is considered by combining the two: 8 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology ,,/ = ,../ + · ,,,/ = 1 - 1 - ,/ · , - , 1 EOTA TR 075, eqs. (1) and (12) EOTA TR 075, eqs. (3) and (13) The resistance of the mechanical part (screw element) is defined by ,../ and the resistance of the chemical part (bonding element) is defined by ,,,/. Both resistances are combined using a factor, ,/ to consider the contribution of bond property of bond material for uncracked/cracked concrete. Resistance of screw anchor: the characteristic resistance of single concrete screw, 0,,,/ is taken from the relevant product ETA. The resistance of the concrete screw part in a group of anchors is calculated by the following equation: ,,,/ = · 0,,,/ · ,, EOTA TR 075, eqs. (2) and (15) When a. different tension load acts on individual anchors in a group, the group effect is considered by the factor, ,, = 1 1+2·(/) 1 and , are calculated using the equations as mentioned in EN 1992- 4 [3]. n is the number of anchors in a group. Resistance of bonding element: the characteristic resistance of the bonding material 0,,,/ for a single anchor is taken from relevant product ETA. The resistance of the bonding material in a group of anchors is calculated by the following equation: ,,,/ = 0,,,/ , 0, , , , , Sustained load factor sus = 1.0 s0us EOTA TR 075, eqs. (5) and (16) EOTA TR 075 eqs. (6) and (17) sus = (s0us - + ,/)/,/ > s0us EOTA TR 075 eqs. (7) and (18) s0us is the factor which takes care of the effect of sustained load on the bond strength of anchors and is considered from the product relevant ETA. The factor (,/) for the contribution of bond property in uncracked/cracked concrete is calculated using the following equation and the value is 1.0. ,/ = 0,,,/(0,,, + 0,,,) EOTA TR 075, eqs. (4) and (14) The group effect of closely spaced anchors is considered by , and calculated using the equation as follows: , = g0,Np - cr,N0,5 g0,Np - 1 1 0, = - - 1 0,,,/ 1,5 , 1 EOTA TR 075, eqs. (9) and (19) EOTA TR 075, eqs. (10) and (20) , = 3 1,5 EOTA TR 075, eqs. (11) and (21) 3 = ucr,N = 11.0 and 3 = cr,N = 7.7 The characteristic spacing is determined using the equation: , = 4.1 0,,,,20/25 + 0,5 0,,,,20/25 3 EOTA TR 075, eq. (8) is the nominal diameter of the concrete screw and 0,,,,20/25 and 0,,,,20/25 are the characteristic resistances of the screw part and bond element for a single fastener in uncracked concrete of defined strength. 9 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology , is the actual projected area and 0, is the ideal projected area of concrete cone. , considers the effect of edge distance for the anchors loaded in tension, , is the factor which includes the effect of reinforcement located in concrete and , considers the eccentricity of a load acting on a group of anchors. 5.3 Design verification against seismic loading The design method for post-installed anchors under seismic loading as per EN 1992-4, Annex C is applicable. For combined pull-out and concrete failure, the resistance value is determined according to EN 1992-4, cl. 7.2.1.6 and EOTA TR 075, cl. 3.2 using the respective characteristic mechanical resistance of the concrete screw 0,,,1 0,,,2, the respective characteristic bond resistance 0,,,1 0,,,2 given in the relevant ETA. 5.4 Design verification against fire loading The design method for post-installed anchors under fire exposure provided in EN 1992-4, Annex D is applicable. For fire resistance only the concrete screw capacity (without the contribution of the bond material) is considered. Instead of the combined pull-out and concrete failure, a pull-out verification according to EN 1992-4, section 7.2.1.5 as for mechanical anchors is performed. Regarding the verification of combined bond and concrete failure, the value of characteristic pull-out resistance of a concrete screw, ,,, should be taken from the relevant ETA. For determination of resistance against concrete cone failure, the effective anchorage depth is calculated according to EAD 330232, figure 1.14. = 0.85 ( - 0.5 - ) 80 Note: in the case of HUS4-MAX, only the mechanical screw part contributes to the resistance against fire. If there is a specific requirement of using a bonded anchor in a project, HUS4-MAX delivers better performance under fire exposure and can be a suitable choice over most of conventional bonded anchor solutions. 6. DESIGN EXAMPLES 6.1 Design example against static loading Project requirement: an I girder is connected to concrete wall using post-installed mechanical screw anchors. The 3D view of the applications is shown in Fig. 6.1. Geometry Concrete thickness Baseplate I profile Spacing between anchors Others Materials Design life Installation 250 mm 250x250x20 mm IPBi 140/HE 140 A 200 mm Concrete C20/25 50 years Rotary-hammer drilling / horizontal, dry Fig. 6.1: Baseplate connection using post-installed anchors 10 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology Note: Design resistances are considered from ETA 18/1160 [6] Note: For retrofitting applications, German National approval [7] is followed Design loads and anchor properties: Post-installed concrete screw anchors Hilti HUS4-H are used for connection. The details about design load and properties are given in Table 6.1. Table 6.1: Design load and anchor properties Type of anchor Specification of anchor Diameter of anchor Effective embedment depth Nominal embedment depth Mechanical HUS4-H 10 64 80 Results: The design has been checked in PROFIS Engineering software and the summary of utilization ratio is mentioned in Table 6.2. Table 6.2: Summary of utilization ratio using HUS4-H screw anchor Failure mode in tension Utilization [%] Steel 20 Concrete cone 59 Combined pull-out 58 Maximum utilization for combined action Failure mode in shear Steel Concrete pry-out Concrete edge Utilization [%] 13 10 49 79 Now, there is a requirement of retrofitting of the existing structure and design loads are modified as per revised design mentioned in Table 6.3. Table 6.3: Revised anchor loads and utilization ratios using existing HUS4-H anchors Failure in tension [%] Failure in shear [%] Steel 31 Steel 13 Concrete cone 89 Concrete pry-out 10 Concrete pull-out 87 Concrete edge 49 Maximum utilization for combined action 116 From the above table it is noted that the existing HUS4-H screw anchors are not suitable for the revised loads and the size needs to be increased to fulfil the design criteria. For the existing structure a possible solution is instead to add the HUS4-MAX capsule with the screw. This allows the use of the same borehole with a HUS4 screw and HUS4-MAX capsule, but increases the performance to a level suitable to the new load requirements. The design has been checked for HUS4-H screw anchors with HUS4-MAX capsule and the result is shown in Table 6.4. Table 6.4: Summary of results using HUS4-MAX anchors of size d10 x 85 mm Failure mode in tension Utilization [%] Steel 31 Concrete cone 79 Combined pull-out and concrete cone 75 Max utilization for combined action Failure mode in shear Steel Concrete pry-out Concrete edge Utilization [%] 12 8 48 98 11 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology Note: Design resistances are considered from ETA 18/1160 [6] The maximum utilization is within the allowable limit for the revised loads, hence the HUS4-MAX anchor is a suitable solution for this retrofitting application. 6.2 Design example against seismic loading Project requirement: A pipe support is connected to concrete slab using post-installed chemical anchors. The 3D view of the applications is shown in Fig. 6.2. Geometry Concrete thickness Baseplate I profile Spacing between anchors Others Materials Design life Installation 200 mm 250x250x20 mm IPBi 140/HE 140 A 180 mm Concrete C20/25 50 years Rotary-hammer drilling / horizontal, dry Fig. 6.2: Baseplate connection using post-installed chemical anchors Design loads: Design is checked for seismic C2-elastic design for the loads shown in Table 6.5. Post-installed chemical anchors Hilti HIT-HY 200-A V3+HAS-U are used for connection and the details are as follows: Table 6.5: Design load and anchor properties Type of anchor Specification of anchor Diameter of anchor Effective embedment depth Chemical HIT-HY 200-A V3 + HAS U 8.8 12 170 Results: The design has been checked in PROFIS Engineering software and the summary of utilization ratio is mentioned in Table 6.6. Table 6.6: Summary of utilization ratio using HIT-HY 200 A V3 chemical anchor Failure mode in tension Utilization [%] Steel 26 Concrete cone 45 Combined pull-out and concrete cone 142 Maximum utilization for combined action Failure mode in shear Steel Concrete pry-out Concrete edge Utilization [%] - - 142 HIT-HY 200-A V3 + HAS-U anchors of diameter 12 mm do not satisfy the design criteria against the seismic loads. The thickness of concrete is 200 mm and max allowable depth for HY 200 anchor is 170 mm. Since the depth of existing anchors can't be increased, the HY 200 anchor of size M12 cannot be used. The option to satisfy the design is to increase the diameter. An increased size of M16 x 110 mm can fulfil the design criteria (refer to Table 6.7). As an alternative option, the design has been checked 12 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology using bonded screw anchors HUS4-MAX. A HUS4-MAX anchor of size d14 x 115 mm fulfils the design and the utilization ratios shown in Table 6.7. Table 6.7: Summary of utilization ratio using HIT-HY 200 and HUS4-MAX HIT-HY 200 (M16 x 110 mm) Failure mode in tension Utilization [%] Steel 14 Concrete cone 75 Combined pull-out and concrete cone 99 HUS4-MAX (d14 x 115 mm) Failure mode in tension Utilization [%] Steel 17 Concrete cone 71 Combined pull-out and concrete cone 96 Note: The increased size for the HUS4-MAX hybrid system to satisfy the design is still smaller than the required size for HIT-HY 200 for the same embedment depth. Also, installation of HIT-HY 200 is more time consuming in comparison to the HUS4-MAX anchor system, which helps to reach a more optimized solution with simpler installation. 7. ADVANTAGES OF USING HUS4-MAX FOR SUITABLE APPLICATIONS At Hilti, we combine better specifications and jobsite practices with our onsite support, helping to ensure that an application can be executed and installed as specified. The Hilti HUS4-MAX bonded screw anchor offers several advantages over many mechanical and bonded systems due to its characteristics: · High load capacity: bonded screw anchors provide excellent load bearing capacity, additional fire resistance and immediate loading like mechanical anchors. These anchors are suitable for a variety of secondary structural and non-structural applications, in uncracked and cracked concrete (C20/25 to C50/60), under static and seismic loading, and when fire resistance is a requirement. · Quick and efficient installation: installation is designed to be quick and straightforward, and requires less time compared to bonded anchors. This faster, simpler, safer installation with no requirement for cleaning the drilled hole, minimal impact of jobsite temperatures in virtually all conditions, adjustability, and removability in case of wrong installation helps increase productivity on the jobsite. · Optimized and code compliant solution: an optimized, high performing and value engineered solution for the relevant applications, with small edge distances and spacing typical of a screw anchor, compliance with European standards, plus full integration in Hilti PROFIS Engineering software, ensures an efficient and accurate design process. Hilti HUS4-MAX bonded screw anchors can be recommended for following applications: Primary and secondary structural connections: HUS4-Max is suitable in normal weight cracked and uncracked concrete (C20/25 to C50/60) under static, quasi-static and seismic (C1 / C2) loading. The highlight is provided by the double holding function (undercut and adhesion). Here are some examples showing application of HUS4-MAX anchors for medium to heavy duty applications in Fig. 7.1. 13 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology a) Column baseplate b) Steel staircase Fig. 7.1: Examples of primary and secondary connections Non-structural applications: even if the application is non-structural this does NOT mean there is NO safety relevance. The EOTA TR 075 [2] / EN1992-4 [3] is intended for safety related applications in which the failure of fastenings may result in collapse or partial collapse of the structure, which could cause risk to human life or lead to significant economic loss. In this context it also covers non-structural elements supported by, or attached to, new or existing buildings such as handrails, roofs and lightweight steel structures. For such applications the Hilti HUS4 screw and Hilti HUS4 bonded screw fastener provides you with the possibility of designing with the smallest edge and spacing distances as used with chemical anchors. In addition, even in connection with the mortar capsule, the Hilti HUS4 bonded screw fastener is still completely removable. Two examples of applications are shown in Fig. 7.2. a) MT support for electrical b) Handrail fixing Fig. 7.2: Examples of non-structural connections Bonded screw anchor HUS4-MAX is also a preferable choice for the connection of building equipment, building systems and machineries due to its flexibility and ease of installation. The double holding function and removability when changing the position of the equipment provides the advantage of being more flexible against functional changes. 8. CONCLUSION The concrete screw anchor Hilti HUS4 is the latest generation of the Hilti post-installed bonded concrete screw, which has been used in jobsites for temporary and permanent fastenings over many years. The latest Hilti HUS4 bonded screw fastener builds on this technology by pairing the screw with the HUS4MAX foil capsule that leads to a high performing, value engineered, optimized design specification connected to faster, simpler, safer and sustainable installation. It also provides greater flexibility to accommodate design changes: by adding the capsule, design challenges and limitations linked to one or the other technology can be addressed without compromising installation simplicity or productivity for the contractors on the jobsite. The best of both worlds for designers and contractors ... brought to you by Hilti. 14 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology 9. REFERENCES [1] EOTA EAD 332795-01-0601: Bonded screw fasteners for use in concrete, Brussels: EOTA, (in preparation). [2] EOTA TR 075: Design of bonded screw fasteners for use in concrete, Brussels: EOTA, (in preparation). [3] EN 1992-4:2018: Eurocode 2 - Design of concrete structures - Part 4: Design of fastenings for use in concrete, Brussels: CEN, 2018. [4] EOTA EAD 330499-02-0601: Bonded fasteners and bonded expansion anchors for use in concrete, Brussels: EOTA, 2024. [5] EOTA EAD 330232-01-0601: Mechanical fasteners for use in concrete, Brussels: EOTA, 2021. [6] ETA-18/1160: HUS4 Bonded screw, Bonded screw fastener for use in concrete, Berlin: DIBt, 16.01.2025. [7] General construction technique permit: Z-21.8-2137- Hilti HUS4 comcrete screw for temporary fastenings in concrete, Kaufering: DIBt, 21st December, 2021. 15 / 16 Post-installed Bonded Screw Anchor, an Innovative Technology Hilti = registered trademark of Hilti Corp., Schaan W4605 0125 © 2025 Right of technical and program changes reserved S. E. & O Hilti Aktiengesellschaft 9494 Schaan, Liechtenstein P +423-234 2965 www.facebook.com/hiltigroup www.hilti.group 16 / 16