Bolt Gauge Research Articles

Group resistances of tensile-loaded anchored-bolted connections with CFST columns: Tests, simulations, and theoretical models

The performance of the connections in concrete-filled steel tubular (CFST) columns fabricated with a group of two anchored blind-bolts under tensile forces is evaluated. Based on the bolt group arrangement, two sets of experiments, comprising eight full-scale specimens, were tested. Test parameters include the presence of concrete, bolt anchorage length, pitch distance, and gauge distance. Further, numerical models were developed, which, after validation, were used for parametric studies. Key findings indicate that bolt gauge distance, anchorage length, concrete grade, and column cross-section slenderness significantly influence the connection behaviour, but pitch distance has the least influence. Tube and concrete failure modes, as well as critical gauge and pitch distances, are identified, which govern tube deformation and concrete crushing zones. Finally, a bi-linear theoretical model is developed that can provide a fair prediction of the connection strength and stiffness.

Experimental response of semi-rigid reinforced concrete beam-column joints with bolted angle dissipating connections

Accelerated building construction is a challenge and opportunity for modern construction techniques such as prefabricated building. However, insufficient connection detail for precast structures resulted in serious damages (even collapse) in past earthquake, which significantly hit the further development of prefabricated building. With satisfactory seismic performance and minimal residual displacement, self-centering joint is an excellent alternative with respect to traditional prefabricated joint. In self-centering system, bolted connections are sufficiently utilized as energy dissipation system. However, the information about connection details is quite limited. Thus, a comprehensive experimental study was conducted to characterize the seismic behavior of semi-rigid reinforced concrete (RC) beam-column joints with bolted angle dissipating connections, namely, semi-rigid joints. Ten full-scale semi-rigid joints were tested under cyclic loading, taking the connection detail as variable. The main configurations of semi-rigid joints based on Eurocode 3 were angle thickness, angle stiffener, bolt diameter, column bolt gauge, rows of beam bolts, and grouting of beam bolts. The test results showed that, by adopting the ductile connection concept, it was possible to produce high ductility and abundant energy dissipation, control damages within the connection zone, and even achieve equivalent monolithic behavior through mobilizing a sufficient rigidity. Feasibility of replacing the damaged connection with a new one with the identical or higher capacity thus obtaining the equivalent or better performance with respect to the original tested joint is also evaluated. Finally, a theoretical model was proposed to evaluate the initial stiffness and bearing capacity of the joints. A good correlation was achieved as comparing to the test results. This research provides significant insight into the performance of precast semi-rigid joints and offers essential data for further investigation of developing design-oriented procedures.

Tensile behavior of TOBs bolted T-stub to circular steel tube with Reverse-Channel

The T-stub bolted to Circular Steel Tube strengthened by Reverse-Channel using Thread-fixed One-side Bolts (TOBs) under tension was studied in this paper. Through welding a reverse channel, the regular bolted flat endplate connection could be employed for the steel beam to circular steel tube column. At the same time, the reverse channel also strengthens the tube wall and extends the hole thread length. Four TOBs bolted T-stub to Circular Steel Tube strengthened by Reverse-Channel (CST-RC) specimens were designed and tested under tension. Critical parameters were determined as the outer diameter of the steel tube, the tube wall thickness, and the bolt gauge distance. Test results revealed three typical failure modes: complete yielding of the whale tube wall, thread shear failure, and complete yielding of the whole tube wall with the thread failure. As well as the tube wall thickness could effectively increase the load-bearing capacity of the connection, a larger bolt gauge distance could reduce the connection deformation. Finite Element Models (FEM) were developed to analyze the load carrying mechanism of TOBs bolted T-stubs to CST-RC. The connection deformation contour, the yield line patterns of tube wall, and the stress distribution on the threads were presented. The behavior of TOBs bolted T-stubs to CST-RC was compared to that of TOBs bolted T-stubs to Circular Steel Tube (CST), and that of TOBs bolted T-stubs to Square Steel Tube (SST). It was found that the reverse channel effectively reduces the circular tube wall deformation and increases connection load-bearing capacity.

Low-cycle fatigue behavior on the tensile region of Hollo-bolted angle connections

This paper presents the results of an experimental program to evaluate the low-cycle fatigue-related characteristics of the tensile region of Hollo-bolted angle connections. A summary of a total of 40 tension tests of equivalent T-stub connections is reported. The geometric parameters vary with the bolt gauge width, the column wall's thickness, the bolt type, and the angle's thickness. Based on the experimental test results, the typical failure mechanisms, the hysteretic load-deformation relationship, and the response characteristics such as degradations of strength and energy dissipation capacity of the connections are examined. It is shown that the bolt gauge width and the angle's thickness have significant influences on the failure mode. Energy-based model is proposed to overcome certain geometric limitations and five commonly used damage models are used to predict the damage behavior of connections. Moreover, the low-cycle fatigue life test results are compared with the codified S–N curves through a transformation of the displacement range into the effective stress range. Furthermore, the cumulative damage mechanism is analyzed and the fatigue life formula is obtained. Finally, the results are evaluated and verified by regression analysis. The 90% confidence level was used to test the availability of the regression equation, and the equivalent level of fatigue strength of the tensile region of angle connections is not less than Category 40 (ΔσC = 40 N/mm2). The EC3, BS7608, and AISC-LRFD-1999 specifications are used to evaluate the low-cycle equivalent fatigue strength, and it is found that there is a certain safety reserve when using Category 36.

Tensile behavior of cruciform stubs with four bolts per row

SummaryThe stiffened top‐and‐seat angle connection is widely used in earthquake‐prone areas, and additional tensile bolts on angles' column leg effectively improve its bending behavior. However, such design and construction are not governed by any regulations. It is urgent to figure out the mechanical behavior and develop accurate theoretical methods. Based on the component method, this paper first conducted an experimental study on the extracted cruciform stubs with four bolts per row. It compared the tensile properties and damage modes for different thicknesses. After that, the further parametric analysis compared the impact of stub thickness, bolt arrangement, and whether or not the bolt was pretensioned after validation. Stub thickness and bolt gauge were observed with a greater impact than the bolt distance on the plastic resistance. Furthermore, a prediction model for the plastic resistance of the cruciform stub with four bolts per row is proposed by integrating approaches for classic stiffened and unstiffened angles.

Yield and ultimate strengths determination of a blind bolted endplate connection to square hollow section column

This paper evaluates the yield and ultimate strengths of a blind bolted endplate to square tubular column connection in joint tensile region. It outlines a research work of eleven connection tests with focus on the strengths of the connection components under tensile loads. The influences of the bolt gauge width, slenderness of tubular columns and bolt size details on the strengths of the connections in three failure modes are reported. Based on the experimental test results, yield strength determination methods are examined and discussed on the basis of deformations of the tube connecting face and the overall connection. Finite element models explicitly allowing for the configuration details of the Hollo-Bolt are then presented and compared with the test results. Subsequently, an analytical model is proposed for the prediction of yield strength with due consideration given to the plastification of SHS column and combined action of the blind bolt related to three failure modes. Based on an augmented consideration of membrane effect and circumferential locking action of the Hollo-Bolt, the analytical model is also extended for the prediction of ultimate strength. Additionally, two geometric parameters in characterizing the failure modes of the connection are discussed from a numerical parametric study. The analytical results presented in this paper provide some essential information for the strength design recommendations of such a blind bolted endplate connection to square tubular column.

Low cycle fatigue response of bolted T-stub connections to HSS columns — Experimental study

Characterization of the low cycle fatigue response of the connection dominated by the hollow structural section (HSS) column in flexural bending and the bolt in tension are necessary to the design of its constitutional semi-rigid joints under earthquake scenarios. This paper presents the results of an experimental programme to evaluate the low cycle fatigue related characteristics of bolted connections to HSS columns. A summary of a total of 69 tension tests of T-stub connections is reported. The geometric parameters were varied as the bolt gauge width, the tube wall slenderness, the bolt size and the tube sidewall depth. Based on the experimental test results, the typical failure mechanisms, the hysteretic load-deformation relation and the response characteristics such as degradations of strength and energy dissipation capacity of the connections are examined. It is shown that the bolt gauge width and the tube wall slenderness have significant influences on the failure mode, the tensile capacity and stiffness which prompt two design parameters; namely, bolt gauge width to tube width ratio (β) and the tube wall thickness-to-half wall width ratio (Ψ0), in quantifying most influential geometric details of the connection. Moreover, the low cyclic fatigue life test results are compared with the codified S–N curves through a transformation of displacement range into effective stress range. It demonstrated a better contrast with test results by further allowing for the geometric parameters of β and Ψ0. Finally, the damage model analysis is employed to study the deterioration progress of the test connections through a comparison with typical damage indices available in the literature. The deficiencies of referred index are identified thereby promoting the proposal of a new model incorporating the stiffness and the energy dissipation in the representation of damage under constant amplitude loading condition. It is shown that the proposed model can give a reasonably well prediction of experimental evidences.

Bolts Gauge Effect on the Face Bending Behaviour of Concrete-Filled Hollow Section for Hollo-Bolted Connections

This paper investigates the effect of bolt gauge on the face bending behaviour of concrete-filled Square Hollow Sections (SHS) in Hollo-Bolted connections. A set of full-scale experiments were undertaken to examine the effects of varying the bolt gauge on the SHS face bending behaviour while controlling all other parameters. Typical experiment involved one row of two bolts pulled out of concrete-filled SHS. A special dummy bolts were manufactured to the exact size and geometry of open Hollo-Bolts, and were used in the experiments to remove the influence of any deformation associated with the real Hollo-Bolts, and isolate the face bending behaviour. Non-contact video-based equipment was used to record the SHS face deformation. This deformation is recorded as force-displacement relationship which is commonly used to represent the structural behaviour of similar components, and typically defined by initial stiffness, yield force and post yield stiffness. Across the range considered in this investigation, it was found that varying the bolt gauge to SHS width ratio have a significant effect on the concrete-filled SHS face in bending component. Both the initial stiffness and the yield force of the component were found to increase with the increase of the bolt gauge. The Post-Yield stiffness was not affected by the change in bolt gauge.

Detection of Small Stress Relaxation in Tightened Metallic Structures by Ultrasounds

Experimental data are presented here to highlight the performances of ultrasounds for the control or the better understanding of the quality of the mechanical contact between tightened plates. Thus, variations of the mechanical load as small as those induced by creep or stress relaxation are potentially detectable by simply monitoring the amplitude of the reflected acoustic plane wave reflected at this interface.To illustrate this, two 3cm thick aluminium plates are firstly tightened with a given torque and next, the amplitude of the acoustic wave is monitored for several days. All long this test, the temperature of the sample is controlled as well as the compression load applied to the plates using a thermocouple and a bolt gauge sensor. The reflected amplitude decreases quickly during first hours and then stabilises after a week approximately. The total variation reaches –28% of the initial value of the reflected amplitude. During this test, temperature is remained almost constant and its fluctuation around the ambient temperature is not correlated with the reflected amplitude. As expected from classic stress relaxation tests, the compression load has slowly decreased by an amount of only –1% but this should have logically increased the reflected amplitude. Further investigations have shown that instrumentation drift were negligible. Consequently, this large decrease of the reflected amplitude has been interpreted as the indication of the increase of the contact area between the two tightened plates. This test attests the high sensitivity of ultrasonic reflection measurement to investigate quality of mechanical contacts for non destructive testing.

Prediction models for the initial rotational stiffness and ultimate plastic moment for a double split tee connection

As a partially restrained connection, a double split tee connection has demonstrated various behavioral characteristics based on the combination of T-stub thickness, high-strength bolt gauge distance, and beam and column stiffness ratio, among other characteristics. Accordingly, many researchers have proposed an analysis model that would determine the behavioral characteristics, stiffness, and strength of a double split tee connection by selecting T-stub thickness and high-strength bolt gauge distance as parameters. However, such a model has not yet been proven to be accurate due to complicated stress distribution, contact and bearing phenomena, as well as prying action on high-strength bolts. Therefore, this study proposed an improved prediction model for the initial rotational stiffness and ultimate plastic moment to implement double split tee connections in the domestic steel structures market. Toward this end, this study performed the three-dimensional nonlinear finite element analysis, and validated the proposed model by comparing and reviewing its test results from the works of other researchers.

Analytical models for the initial axial tensile stiffness and ultimate tensile load of a T-stub, including the effects of prying action

A T-stub with a thin flange and a wider high-strength bolt gauge distance generally fails due to the yield of the flange. Since prying action greatly influences a T-stub with such failure characteristics, its effects must be considered in estimating the failure aspects, stiffness, and strength of a T-stub. To accurately determine the effects of a prying action applied to a T-stub and to reflect them in a design, however, the contacts, bearing, concentrated stress, and plastic hinges, among complex submaterials, should first be accurately examined and quantified. Thus, this study aimed to explain better the complex phenomena that influence the effects of prying action by conducting an axial tensile force test and a three-dimensional nonlinear finite element analysis of a T-stub and proposing an improved analytical model for estimating the initial axial tensile stiffness and the ultimate tensile load of a T-stub, including the effects of prying action on it.

IDM을 이용한 강구조의 구조설계 단계별 정보전달 요구 분석

Abstract In construction project, it is important to exchange and share the digital information generated by their own professional softwares. So this paper analyzed the information delivery requirements of steel structure according the structural design stages using IDM methodology. For schematic design stage and detailed design stage, the structural design information to share in each design stages is abstracted by defining the PM, ER, and FP. The new ERs and FPs are proposed by defining the new property sets(Psets), suchlike bolt gauge line, weld, scallop, and cope, to complement the structural design information of IFC2×3. Finally, the reasonability of the proposed new ERs, FPs are verified by applying them to represent the standard steel connection sample in detailed design stage. As a result, the structural design information of standard steel connection could be stored and managed sufficiently by using the proposed new ERs and FPs. Key Words : BIM, IDM, IFC, Interoperability, Structural information

A Finite Element Model for the Prediction of the Behavior of an Unstiffened Top and Seat Angle Connection with Various Top Angle Bolt Gage Distances

This study aimed at proposing a finite element model for predicting the initial rotational stiffness and plastic moment capacity of the Type A top and seat angle connection without double web angles. The main parameter of the 3D nonlinear finite element analysis was the bolt gage distance of the top angle. The finite element analysis resulted not only in the rotational stiffness and the plastic moment capacity, but also in the stress distribution and the plastic hinge location. The study verified the applicability of the finite element model by comparing the results of the finite element analysis with those of existing experimental studies.

Yield Line Analysis of Bolted Connections to I-Section Webs

The yield line analysis method is adopted to develop expressions for predicting yield load of bolted I-section web as the connecting face governs the failure of such connection. The proposed expressions are studied by varying the ratio, , of the bolt gauge width to the effective width of the web. By introduction of connecting face deformation limit, the comparison of the yield loads predicted by theoretical expressions and finite element analysis are demonstrated a satisfactory result for practical design. Thus, the yield load predicted by proposed expressions can be used as the basis for design of the bolted connections to I-section webs.

Design moment of shear connections at the ultimate limit state

Shear connections develop moment under the rotational demand imposed on them by the supported beam. This paper proposes a semi-analytical approach for computing the moment of single-angle, double-angle and end-plate shear connections corresponding to the strength limit state of their supported beam. The connection moment equations are derived based on the observed yieldline mechanisms from various experimental tests on the shear connections. The approach takes into account major parameters such as connection plate thickness, angle length, bolt gauge and steel yield strength. The obtained equations can also be used to estimate the compression zone depth and tension zone force. Good agreement between the theoretical analysis results and the various test data is demonstrated. Finally, suggestions are given for applying the approach to design shear connections.

Research on end-plate connection with non-completely penetrated welds

A series of tests were executed for H-shaped beams whose flanges were connected to end-plate by non-completely penetrated welds. The welds were designed by equal capacity rule and the beams were mainly composed of non-compact or slender elements. The parameters introduced are width–thickness ratios of beam flange and web, end-plate thickness, angle between flange plane and end-plate plane and so on. 24 pieces of specimens were tested to failure under monotonic loading and 6 under cyclic loading. For comparison, a few of the specimens are those with completely penetrated groove welds. Finite element (FE) analysis was also carried out to study the effect of parameter change on the resistance of the welds. The parameters involved end-plate thickness, weld size, column flange thickness and bolt gauge. The results show that thinner end-plate and greater bolt gauge will deteriorate the resistance of weld. As long as the components are properly designed, as done in tests, the connections will not fail at the welds no matter what kind of weld form is adopted. In addition, weld form has no obvious effect on the ultimate loads and cyclic behavior of specimens. It is confirmed that the non-completely penetrated welds connecting flanges of H-shaped beams and end-plates can be used both under static loading and seismic loading in low-rise building structure where local buckling of the member is the predominant factor.

A New Concept for Structural Health Monitoring of Bolted Composite Joints

This study provides a practical method regarding the development of a complete self-diagnostic technique for monitoring the bearing damage of bolted composite or metallic joints. The basic concept is based on making BG (Bolt Gauge) measurements that has been proposed in earlier work [1,2]. That is, bonding a strain gauge onto the surface of bolt head to monitor the bolt strain changes that would identify bearing damage. Extensive tests using double lap bolted joint specimens are performed to verify the health monitoring technique, including the effects of the bolt clamp-up, material response, joint geometry and loading history. The results have shown that the bearing damage detected by BG measurements agreed well with acoustic emission (AE) measurements. Finite element analysis is performed to discuss the monitoring mechanisms.

健全性診断機能を付与した機械的継手部の革新設計

The primary objective of this study is to address a key research challenge for improving tradi-tional joint design, which develop functions and structures that can monitor their own structural integrity. A self-sensing technique using the bolt itself to monitor the bearing damage in bolted composite or metallic joints is proposed. The basic concept is based on making Bolt Gauge (BG) measurements. That is, have only to bond a strain gauge onto the surface of bolt head to reflect changes in the bolt strain, which would identify the state of bearing damage. Novel system can maintain not only the peculiar structures and functions of the mechanical fastener, but more importantly, also can provide the self-diagnostic function for component damage. And, it can be contributed directly to technology development for structural health monitoring (SHM) to address these issues, and to meet demanding goals in increasing aerospace vehicle safety and reliability while reducing operating costs. Extensive tests using double lap bolted joint specimen are performed to verify this technique in the various joint cases. The investigations include the effects of the bolt clamp-up, material response, joint geometry and loading history on the detection sensitivities for the bearing damage. The onset and progress of the bearing damage monitored by BG measurements are also compared with acoustic emission (AE) measurements that used in traditional NDE method. A further consideration of the detection mechanisms by BG including an axial loading test and a three-dimensional finite element analysis is performed. The behavior of bolt deformation and stiffness degradation due to the bearing damage initiation and progression are estimated using damage mechanics approach.

Cyclic Load Tests and Analysis of Bolted Top-and-Seat Angle Connections

The behavior of angles in a bolted angle beam-to-column connection is experimentally investigated. The purpose of this investigation is to determine how the angle size and bolt gage length, defined as the distance between the bolt line passing through the column and the heel of the angle, affect the connection stiffness, strength, energy dissipation capacity, and resistance to low-cycle fatigue. The test results show that the angles are capable of considerable strength beyond the point at which a yield mechanism occurs. The associated stiffness, i.e., postyield stiffness, is approximately linear and comprised of both geometric and material hardening. The bolt gage length greatly influences all connection characteristics studied. A larger amount of energy can be dissipated for connections with smaller bolt gage lengths. However, connections with smaller bolt gage lengths generally have a lower fatigue life. An analytical model is presented that predicts the behavior of bolted beam-to-column angle connections. The correlation with test results is good.

Moment–rotation behavior of double angle connections subjected to shear load

Double angle connections, which are welded to the beam web and bolted to the column flange, are studied to establish the effect of bolt gage distance and angle thickness. An analysis is performed to establish the moment–rotation relationship for the double angle connections and the stress distribution of each specimen is observed. They are subjected to shear loads and the elastic–perfectly plastic constitutive law is assumed. The software package ABAQUS is used to analyze the nonlinear behavior of a double angle connection. To verify the finite element model analysis, experimental tests with the same geometric and material conditions as the analysis are also conducted.