In this paper, it was aimed to evaluate the effectiveness of four different types of filler materials with particle sizes below 63 mu m in sustainable geopolymer mortars. For this purpose, 25%, 50%, and 75% limestone powder (LSP), basalt powder (BP), waste marble powder (WMP), and recycled aggregate powder (RAP) were substituted with river sand and 13 different mixtures including reference were obtained. Metakaolin was used as the main binder material, and sodium hydroxide/sodium silicate was used in a ratio of 1:2 as an activator. In addition, blast furnace slag was added to the mixture as a reaction accelerator at a rate of 13% of the amount of metakaolin. To determine the mechanical properties of the produced geopolymer mortars, compressive strength, flexural strength, splitting strength, porosity, ultrasonic pulse velocity (UPV), and abrasion tests were performed. Also, SEM and XRD analyses were performed to examine the microstructures of the specimens. The satisfactory results obtained proved that all four types of filler materials can be used in metakaolin-based geopolymer mortars. Optimum rates for limestone powder, basalt powder, waste marble powder, and recycled aggregate powder were obtained as 50%, 50%, 25%, and 25%, respectively.

To determine the load-bearing capacity of cold-formed steel (CFS) beam-column members, closed formed interaction formulas are generally used in most current design guidelines by linearly combining axial load and biaxial bending moment effects. However, this approach ignores the nonlinear interactions between these actions. To evaluate this issue, in this research the structural behaviour of eccentrically loaded beam-column CFS lipped and sigma channel profiles are investigated experimentally and analytically under simultaneous effects of axial loads and biaxial bending moments. Detailed Finite Element (FE) models are developed using ABAQUS software by considering geometric imperfections and actual material properties obtained from coupon tests, and validated against experimental data to estimate the strength and buckling behaviour of CFS beam- column elements. A total of 4480 FE analyses are then performed on 500 mm and 2000 mm long CFS members with different lipped and sigma channel sections subjected to a wide range of eccentricity values in various directions. The results of the analyses indicate that the failure modes are mainly dependent on the stress distribution of the cross-section generated by the combined actions. It is also demonstrated that regardless of the selected load combination, using sigma sections for the short beam-column members generally results in higher strength by up to 42% compared to those with lipped channel sections. It is shown that AISI and Eurocode underestimate the capacity of CFS beam-column members, on average, by around %50 and %25, respectively. However, the recently proposed extended Direct Strength Method (DSM) can generally provide more accurate strength predictions, especially in the case of short beam-column elements.

Precast structures are increasingly used in modern construction since they offer advantages such as costefficiency, better material quality, and fast construction due to their mass production compared to cast-in-situ structures. However, development of monolithic-like precast connections to ensure adequate seismic performance is still a challenging task. This study aims to introduce a monolithic-like column-foundation precast connection, which is easy to assemble and disassemble and therefore is replaceable in case of excessive damage. To investigate the efficiency of the proposed system, four full-scale precast and monolithic column-foundation connection specimens are tested under constant axial load and lateral reversed cyclic loading. Experimental results are then used to obtain seismic performance parameters such as failure mode, flexural capacity, initial stiffness, ductility, energy dissipation and curvature distribution. The results indicate that, in general, the proposed precast connections exhibit similar structural performance as their monolithic counterparts. Subsequently, experimentally validated finite element (FE) models are developed to provide practical tools for seismic design and performance assessment of the proposed precast connection system. It is shown that the developed models can accurately estimate the load-bearing capacity, initial stiffness and post-peak behaviour of both precast and monolithic column-foundation connections.

High-temperature exposure can considerably affect the structural performance and load-carrying capacity of reinforced concrete (RC) structural elements, leading to a partial or total collapse. This study aims to characterize the structural behaviour of RC columns exposed to high-temperature (about 1150 degrees C) and axial load simultaneously subject to different heating-cooling scenarios. An advanced electric furnace and cooling system is developed to subject RC columns under constant axial loads to high-temperature effects in accordance to ISO 834 standard. In total 16 large scale tests are conducted on 250 x 250 x 1200 mm column specimens. The main parameters of the study are concrete strength (13.7 MPa and 41.4 MPa), heating time (30, 60 and 120 min) and cooling method (water-cooling and air-cooling). A continuously high-temperature exposing scenario is also considered to represent a fire event with no-firefighting intervention. The changes in the stiffness and bearing capacity of the column specimens are investigated for each case. The results indicate that 120 min of high-temperature exposure could reduce the axial load carrying capacity of the specimens up to 9.5% and 35% using air-cooling and water-cooling systems, respectively. It is also shown that the normal and low-strength column specimens experienced a sudden lost in their load-bearing capacity after 210 and 240 min of continuous high-temperature heating, respectively, leading to collapse. The experimental results are then used to develop detailed non-linear finite element (FE) models in ABAQUS as practical tools for the design and assessment of RC columns exposed to high-temperature and axial loading using different cooling methods.

In this study, bond behavior of ordinary concrete and rebars with different diameters and development length was investigated by using Hinged Beam Test (HBT) and Eccentric Pull-Out Test (EPT) comparatively. For this purpose, three different rebar size and development length depending on rebar diameter were chosen as variables. Three specimens were produced for each series of specimens and totally 54 specimens were tested. At the end of the tests it was observed that obtained results for both tests were quite similar. On the other hand, increased bar size, especially for the specimen with 14 mm bar size and 14 development length (lb), caused shear failure of test specimens. This situation infers that when bigger bar size and lb are used in such test, dimensions of test specimens should be chosen bigger and stirrups should be used for producing of test specimens to obtain more adequate result by preventing shear failure. Also, a nonlinear regression analysis was employed between HBT and EPT results. There was a high correlation between the EPT values, lb, rebar diameters and estimated theoretical HBT. In addition, at the end of the study an equation was suggested to estimate bond strength for HBT by using EPT results.

The main purpose of this study is to examine the behavior of the brick masonry and infill walls under cyclic horizontal loads, irrespective of reinforced concrete frames. For this purpose, the test walls, which are produced as non-plastered (plane), two side plastered and two side plastered and strengthened with zinc coated steel wire mesh by using vertical and horizontal hollow brick walls were tested in a rigid hinged steel loading frame under lateral cyclic loading. The findings were evaluated in terms of load carrying capacity, ductility and energy dissipation capacities. The tests carried out showed that the expected increases were provided any type of plastered walls in terms of stiffness with respect to the reference non-plastered walls. Besides this, wired mesh used in plastered walls increased significantly the ductility and consequently the energy dissipation capacity of the walls by maintaining wall integrity in an advanced stage of the loading. Also, both hollow brick and vertical brick infill walls strengthening with wired mesh increase load carrying capacity of the wall test specimens. Load carrying and energy dissipation capacities of wire meshed specimens almost five times more than those of plane test walls.

: Reinforced concrete structures are traditionally designed to carry service loads and lateral forces caused by seismic events. However, recent incidents such as Grenfell Tower fire in London highlighted the fact that fire and high-temperature should be also taken into account as hazardous phenomena that can significantly affect the safety of the reinforced concrete structures. High-temperature exposure can considerably affect the structural performance and load carrying capacity of reinforced concrete members, and therefore lead to a partial or total collapse. To address this issue, this study aims to investigate the axial load bearing capacity of reinforced concrete columns exposed to high temperature. A custom made high-temperature electric furnace was used to test reinforced concrete columns under simultaneous effects of axial load and high temperature. In addition, thanks to its twin unit design, the furnace allows investigating the effects of both water-cooling and air-cooling on the axial loading capacity of the columns after high temperature exposure. Also, an advanced computer control system was designed using Arduino micro-controller to apply any kind of heating curves to the test specimens. In this study, ISO-834 standard fire curve was used for the experimental tests. The main parameters considered within the study are heating duration, and cooling scenario. Dimensions of the column specimens were chosen as 250 × 250 × 1200 mm. The specimens were subjected to a predefined constant axial load during heating and cooling process. Subsequently, in order to obtain the post-fire residual capacity of the reinforced concrete columns using different heating durations and cooling scenarios, loading was continued up till the failure. The results of this study, can be used to develop more efficient methods to design reinforced concrete columns exposed to high temperature.

Cold-formed steel (CFS) sigma profiles generally used as purlins or portal frame members are shown in the literature to exhibit higher load carrying capacities compared to standard channel section profiles. However, currently CFS channel sections are more widely used, especially in residential buildings, due to ease of installation and also the knowledge about their structural performance gained through numerous experimental and numerical studies over last decades. To bridge the knowledge gap in using CFS sigma beam-column sections in common practice, this study aims to investigate the characteristic behaviour of these elements including their stiffness and strength under axial load and biaxial bending. In general, to determine the capacity of beam-column members, most existing design guidelines (e.g. AISI S213-07, AISI S100-12, AS/NZS 2005) suggest closed formed interaction formulas as a linear combination of axial load, and strongand weak-axis bending moment effects. However, this approach ignores the nonlinear interactions between these actions. To address this issue, in this study, the structural behaviour of eccentrically loaded beam-column elements with CFS sigma profiles is investigated under simultaneous effects of axial loads and strong-and weak-axis bending (P-Mx-My). To this end, CUFSM software is used to determine the dominant buckling mode (i.e. local, distortional or global) and load carrying capacity of CFS sigma beam-column elements with different lengths. Material parameters are also implemented in the detailed finite element models developed in ABAQUS software. The models are then used to estimate the strength and buckling behaviour under monotonic loadings. A total of 315 finite element analyses are performed on different CFS beam-column elements with sigma profile and the results are compared with existing codes.

This study aims to develop a novel monolithic-like precast beam-column connection for reinforced concrete (RC) structures. The proposed connection system has several advantages such as rapid assembly and disassembly, reusability, and replaceability if damaged during an earthquake event. An experimental investigation was first carried out to determine the seismic performance of the proposed connections. In total, six full-scale precast and monolithic T-shape beam-column connection specimens with different reinforcement ratios, specimen dimensions and detailing were tested under displacement controlled cyclic loading, while the axial load on the column was kept constant. The cyclic behaviour, curvature distribution, failure mode, energy dissipation capacity and ductility of the specimens were obtained using the experimental outputs. Detailed non-linear finite element (FE) models were then developed using ABAQUS. It is shown that the FE models can accurately predict the overall performance of the precast connections in terms of initial stiffness, lateral load-bearing capacity and post-peak behaviour. The results indicate that, in general, the precast connections exhibited considerably higher (up to 34%) ductility and ultimate drift ratio (deformability) compared to similar monolithic connections. For the same drift ratio, monolithic connections exhibited slightly higher (on average 10%) energy dissipation capacity, while the precast connections generally dissipated higher energy at their ultimate point (post-peak lateral drift corresponding to 15% loss in lateral strength). It is demonstrated that the monolithic-like precast connections can satisfy the ACI 318-14 acceptance criteria, while they also sustain the ASCE 41-17 Collapse Prevention (CP) limits. Therefore, the proposed connection system is considered to be suitable for RC structures in seismic regions.

Various failure criterions have been used for the nonlinear analysis of concrete and reinforced concrete structures. To get more accurate results from the analyses, the selected failure criterion must be appropriate with the characteristics of problem and the assumptions made in the criterion should comply with the characteristics of problem. In this study, an experimental investigation was carried out to determine the cohesion (c) and internal friction angle (.) values, which are in the compressive strength range of 14.4 MPa <= f(cm) (cube) <= 47.0 MPa (2.03 ksi <= f(cm) (cube) <= 6.82 ksi) that are used in failure criterions such as Mohr-Coulomb and Drucker-Prager preferred in end unit analyses for concrete and reinforced concrete structures. Tests are performed by using the direct shear test system, which is designed and produced for this study. Finally, cohesion and internal friction angle were determined between 2.94 and 12.34 MPa (0.43 and 1.79 ksi) and 29.8 and 41.7 degrees, respectively.

In this study, bolted moment connection model for precast reinforced concrete column-beam joint was developed and tested experimentally in order to obtain and compare its bearing capacity with traditional cast-in-place monolithic joint. With this purpose, a bolted moment connection behaving like a monolithic connection were designed. A full-scale T-shape beam and column were produced separately and assembled by using high strength bolts. This specimen was tested under constant axial load on column and quasi-static reverse cyclic lateral loading on beam end. Identically same monolithic specimen was also tested under the same conditions. Test results showed that bearing capacity of bolted specimen is approximately 20% higher than the capacity of monolithic one. In addition, it is observed that the shear and moment capacity of bolted joint has increased. Hence it is obtained that it is possible to build moment resisting frame structures by using the bolted moment connection suggested within this study and this system can be used for structures in seismic regions.

In this study, parameters which define Drucker-Prager yield criterion were investigated experimentally for both normal strength concrete (NSC) and high strength concrete (HSC) by triaxial compression tests. Total 16 concrete series with different concrete strength were produced. While 8 concrete series were produced as NSC (20MPa<fcm<55MPa), other 8 series were produced as HSC (55MPa<fcm<85MPa). Each series contains 16 specimens. Triaxial compression tests were performed on these concrete specimens. Concrete compressive strength of the specimens were measured under 4 different lateral compression level (0, 1, 2 and 4MPa). After Mohr circles were drawn by using the data obtained from triaxial compression tests, the values of cohesion were determined between 5MPa and 13MPa for NSC and 13MPa and 19MPa for HSC. The values of internal friction angle were also obtained between 27° and 34° for NSC, 34° and 39° for HSC from the Mohr circles. The parameters defining the Drucker-Prager yield criterion were determined by using the values of cohesion and internal friction angle. Finally, after some equations were proposed to calculate the parameters by using concrete compressive strength, the validation of these equations were also proved in this study.

In this study, the change of the behaviour of high-strength reinforced concrete (HSRC) columns under axial and eccentric load based on the ratios of transversal and longitudinal reinforcements was investigated. To do this, 2100mm height and 200mm x 300mm cross-sectional sizes reinforced concrete columns which have different transversal and longitudinal reinforcement ratios were produced with high-strength concrete. On these produced columns, two different eccentricity (e = 25mm and e = 50mm) and axial (e = 0) loadings were done. The experimental and theoretical moment-curvature (M-K) relations were determined and compared with each other. Test results showed that in the HSRC columns, the ratio of longitudinal reinforcement did not changed the fracture type which was brittle, but when the ratio of transversal reinforcement increased, the type of fracture was changed. The M-K relation obtained from the experiments and the M-K relation calculated theoretically were in harmony. This showed that the material model which was used to determine theoretical M-K relation was suitable for HSRC.

In this paper, experimental and theoretical studies performed on apex connection of an industrial portal frame constructed with cold-formed back-to-back double sigma profile rafters are presented. By those experiments performed, local buckling behavior of the apex plate and load–displacement behavior of the system were investigated under monotonic vertical loading. This investigation was conducted for conditions that the gap between rafter ends at the apex plate are 90, 180, 360, and 450mm and apex plate is unstiffened/stiffened. Experimental results for the model with 360mm gap were compared to those of nonlinear quasi-static finite element analyses performed using a finite element software and a good agreement between those results was observed. The connection׳s behavior is controlled by the apex plate. No significant damage occurred on the profiles after the tests. According to the results, it is sufficient to increase the gap between rafter ends up to not higher than 360mm in order to maximize the general load carrying capacity of the system and the stability of out of plane local buckling behavior of the apex plate. Furthermore, although stiffener plate significantly restricted local buckling of apex plate, no remarkable effect of this enhancement was observed on the flexural capacity of the system.

One of the most important structural components of steel structures is the column-base connections which are obliged to transfer horizontal and vertical loads safely to the reinforced concrete (RC) or concrete base. The column-base connections of steel or composite steel structures can be organized both moment resistant and non-moment resistant leading to different connection styles. Some of these connection styles are ordinary bolded systems, socket systems and embedded systems. The structures are frequently exposed to cycling lateral loading effects causing fatal damages on connections like columns-to-beams or columns-to-base. In this paper, connection of steel column with RC base was investigated analytically and experimentally. In the experiments, bolded connections, socket and embedded connection systems are taken into consideration by applying cyclic lateral loads. Performance curves for each connection were obtained according to experimental and analytical studies conducted and inelastic behavior of connections was evaluated accordingly. The cyclic lateral performance of the connection style of embedding the steel column into the reinforced concrete base and strengthening of steel column in upper level of base connection was found to be higher and effective than other connection systems. Also, all relevant test results were discussed.

In past few decades, the interest in using pultruded fiber reinforced polymeric (PFRP) composites in construction applications has grown rapidly. Several research studies were conducted and focused on the performance of PFRP beams, columns and frame structures. The results of the majority of previous studies highlighted a major problem associated with the deficiency of the off-the-shelf, unidirectional open-web pultruded profiles. In this regards, a common conclusion was drawn by many researchers; that is: the inherent structural deficiency of commercially produced unidirectional PFRP profiles, especially at the flange/web(s) junction(s) that lacks fiber continuity. The lack of fiber continuity creates a "resin-rich" zones at the junctions that were shown to be responsible for rapid degradation of both axial and rotational stiffness as well as the strength of the majority of PFRP profiles. Another related problem is the use of incorrect framing connection details, currently being used by industry.Such connection details mimic those associated with steel structures. This approach ignores both the anisotropic and the viscoelastic nature of composites as well as the aforementioned inherent junction deficiency that, in most cases, lead to a greater risk with regard to the safety, reliability and economic aspects of such structures. This paper presents a summary of an experimental study aimed at evaluating both axial and rotational stiffnesses and strengths of web-flange junctions, which may affect stiffness, buckling, post-buckling, torsional and overall strength of PFRP structures. In particular, three sizes of commercially-produced unidirectional pultruded H-profiles and two sizes of L-profiles were evaluated under both service and ultimate loads. Using full-scale experimental data, P-delta and M-theta relations and idealized expressions for each pultruded profile were developed that can be used for accurate modeling and for establishing design limit-states for PFRP structures. In addition, two special test fixtures were designed, fabricated and validated that can be adopted by ASTM/ISO standards for characterizing such critical mechanical properties that are essential for reliable design of pultruded composite structures. Conclusions and design recommendations are also presented. (C) 2014 Elsevier Ltd. All rights reserved.

This paper presents an experimental study on socket base connections of precast reinforced concrete columns. The main purpose of this study is to determine socket base connection which has the closest behavior to monolithic casted column-base joints. For this purpose, six specimens having different column-socket base connection details were tested under cyclic loading. For each test, strength, stiffness, ductility and drift ratios of the specimens were determined. Test results indicated that a suggested connection type is 10% - 30% stronger than the other type of connections under lateral loading. The welded connection (PC-5) had better lateral load carrying capacity and ductility. On the other hand, performance of standard connection (PC-1) which is commonly used in construction was weaker than other connections. Thus, decision of connection type should be referred not only performance but also applicability.