Non-seismic Design Research Articles

Performance of Seismically-Compatible Fin Plate Joints under Fire Conditions

This paper compares the performance of fin plate joints designed with and without seismic considerations under gravity loading and fire conditions. The non-seismic design, following British detailing provisions, has a thicker fin plate located higher on the beam web and it positions the beam web closer to the column face compared to the seismic design detail based on New Zealand provisions. Finite elements in ABAQUS are used to model the subassembly, which is subjected to the ISO 834 fire with and without a cooling phase. The analyses indicate the same failure mode in both subassemblies, with yielding at the beam web top bolt hole in bearing and fracture of the top bolt in shear. However, under the same fire regime, peak compressive and moment demands of the seismic detail were approximately 25% less than those for the non-seismic detail. When subjected to heating only, time to runaway failure was similar for the seismic and non-seismic detail, occurring at 15.0 and 14.8 min into the analyses respectively. When a cooling phase was included, beginning 10 min after initial fire exposure, both subassemblies recovered without failure. A parametric study showed a larger gap between the beam end and column face decreased compression in the beam but did not significantly affect the failure characteristics of the joint. Use of thicker fin plates was also found to increase the time to failure. The results show that the seismic detailing provides limited improvement over the non-seismic detail for the analysed fin plates.

Structural Non-Seismic Design of Post-Tensioned CLT Shear Walls

Structural Non-Seismic Design of Post-Tensioned CLT Shear Walls

Cost Estimation of Structural Work for Residential Building with Seismic Design Consideration

The Sumatra-Andaman earthquakes had triggered local earthquakes in Malaysia by reactivation of ancient inactive faults. Previously on 5thJune 2015, Ranau, a region located in Sabah, Malaysia, had experienced a moderate earthquake of Mw6.1. The structural failures occurred because all existing buildings only designed for gravity load without any seismic provision. Recent research work exhibits the seismic designs’ impact on the cost of material and its parameters thatimpact the cost. There are two types reinforced concrete residential buildings called Type 1 and Type 2 for two storey and four storeywhich had been used as models. This research applied four seismicity levels to the reference peak ground acceleration value, αgR= 0.07g, 0.10g, 0.13g & 0.16g, and two soil types: Soil Types B and D. The result shows that for twostorey reinforced concreteresidential buildings on soil types B and D, seismic design increases structural work costs, which is around 0.62% to 1.31% and 0.61% to 2.16%, respectively,for Type 1 modelcompared to non-seismic design. Besides,model Type 2, the increment is around 0.24% to 1.22% and 0.20% to 1.71%, respectively.Otherwise, for reinforced concreteresidential building with four storeyon soil types B and D,the result shows that seismic design tends to have a higher structural work’s costaround 0.41% to 2.48% and 0.98% to 11.23%, respectively, for Type 1 model. Besides, for model Type 2 the increment is around 1.80% to 2.05% and 2.34% to 8.53%, respectively, compared to non-seismicdesign.

Dynamic progressive collapse response of multi-storey frame structures with masonry infills

The response of reinforced concrete (RC) frame building structures to exceptional events like explosions or impacts causing the loss of a primary structural element depends on the robustness of the structural configuration. In the case of a sudden column loss, the resisting mechanism of the involved spans substantially changes, while a progressive collapse mechanism can develop under the arising dynamic loads. The presence of masonry infill walls can substantially modify the overall response to a sudden column loss scenario. In this context, this paper investigates the response of reinforced concrete frame structures undergoing instantaneous column losses in order to assess the influence of masonry infills on the progressive collapse response under dynamic load demands. A recently formulated equivalent-strut macro-modelling approach is employed to reproduce the mechanical interaction between infill walls and the frames. A ten-storey, six-bays 2D reinforced concrete frame is selected as a case study structure considering different reinforcement layouts (seismic or non-seismic design) and column loss scenarios (central column or corner column loss). The simulations are carried out using the fiber-section beam/column elements available in the OpenSees software platform, as they can account for the arching mechanism developing in the post-cracked regime. The dynamic responses of the case-study tests to the sudden column loss scenarios are assessed with and without the inclusion of masonry infills within the structural models. Results demonstrate that masonry infills introduce a substantial modification of the resisting mechanism and of the dynamic response, limiting the propagation of progressive collapse in most of the considered cases.

Effect of seismic design on the cost of structural works for two-storey residential building

Malaysia's low to moderate seismic threat should not be disregarded, and seismic design in structures should be considered. The region has previously seen significant earthquakes, especially in Sabah, as evidenced by the current increase in the frequency of minor earthquakes every day, where a current moderate earthquake magnitude of Mw 6.0 struck on 5th June 2015 in Ranau. Although the Ranau earthquake was not high-level. Malaysia suffered fatalities and millions of dollars in infrastructure and building destruction. This is mainly caused by the fact that structural design in Malaysia only considers gravity loads and does not account for seismic practices. Recent research has demonstrated how seismic designs affect material prices and cost-influencing parameters. In this study, Type 1 and Type 2 two-storey reinforced concrete residential buildings were chosen as models. Four seismicity levels were employed, each corresponding to the reference peak ground acceleration value, αgR= 0.07g, 0.10g, 0.13g, and 0.16g, as well as two soil types, Soil Types B and D. According to observations, seismic design increases the cost of structural works, ranging from 0.62% to 2.16% higher than nonseismic design for Type 1 models. Furthermore, the increment for Type 2 models ranges from 0.24% to 1.71%.

Repair and retrofitting of external RC beam-to-column joints using the hybrid NSM + EBR method

In this study, the repair and retrofitting of external reinforced-concrete (RC) beam-to-column joints using FRP composites is investigated by performing experimental tests. The seismic design detailing for the panel zone is not considered in the design of the tested joints. The test program was performed in three stages. At the first stage, the specimens were loaded until reaching different levels of damage. Subsequently, the damaged specimens were repaired and retrofitted by the NSM and hybrid EBR + NSM methods using FRP composites. Finally, the retrofitted joints were loaded cyclically until their failure. This study is intended to investigate the influence of the utilized retrofitting methods on improving load carrying capacity, stiffness, and ductility of damaged RC joints. For this purpose, eight RC beam-to-column joints, including seven non-seismically designed (NS) and one seismically designed joint (S), were cast and tested. The attained experimental results for the load-carrying capacity, stiffness reduction, and the cumulative dissipated energy of NS specimens were compared with the S specimen. The results showed the proposed hybrid retrofitting methods can recover the lost capacities of joints and even increase their capacities to levels higher than the seismic control specimen. In addition, it is found that according to Park and Ang damage index, the tested specimens are repairable up to 2.6% drift ratio.

Simplified Approach for the Seismic Assessment of Existing X Shaped CBFs: Examples and Numerical Applications

The capacity of a structure can be assessed using inelastic analyses, requiring sophisticated numerical procedures such as pushover and incremental dynamic analyses. A simplified method for the evaluation of the seismic performance of steel Concentrically Braced Frames (CBFs) to be used in everyday practice and the immediate aftermath of an earthquake has been recently proposed. This method evaluates the capacity of an existing building employing an analytical trilinear model without resorting to any non-linear analysis. The proposed methodology has been set up through a large parametric analysis, carried out on 420 frames designed according to three different approaches: the first one is the Theory of Plastic Mechanism Control (TPMC), ensuring the design of structures showing global collapse mechanisms (GCBFs), the second one is based on the Eurocode 8 design requirements (SCBFs), and the third is a non-seismic design, based on a non-seismic design (OCBFs). In this paper, some examples of the application of this simplified methodology are proposed with references to structures that are supposed to exhibit global, partial, and soft storey mechanisms.

Increment of material usage in construction of four storey reinforced concrete building due to seismic design

Malaysia is fortunate because it is located outside the Pacific Ring-Fire region which is seismically active. However, it still exposes to earthquake hazard from Far-Field earthquake from neighbouring countries. In Peninsular, it is exposes to Sumatra-Andaman earthquake from Indonesia. In East Malaysia, to states namely as Sabah and Sarawak are expose to Philippines earthquake. Besides, Malaysia also experienced earthquakes from local faults such as Bukit Tinggi in 2007. On 5th June 2015, a moderate earthquake with Mw6.1 occurred in Ranau, Sabah which caused 18 fatalities. The same event also caused damage to 61 buildings around Ranau and Kundasang. For the sake of safety, construction of new buildings in Malaysia has to consider seismic design. This paper presents a study to evaluate the increment of construction materials used due to consideration of seismic design. A typical four-storey generic reinforced concrete school building had been used as model. This study adjusted the value of reference peak ground acceleration, α gR in modelling, analysis, and design process. The concrete grade was fixed as C30. Four soil types had been considered for all models with seismic design consideration. Findings from this study demonstrate that the consideration of seismic design caused the increment of steel reinforcement around 16% to 32% for beam and 1% to 14% for column. In term of cost of structural work, consideration of seismic design increases the cost in range of 2% to 5% compared to the nonseismic design. Therefore, it is worth for Malaysia to fully implement the seismic design in new development.

Shear Strength of Reinforced Concrete Columns Retrofitted by Glass Fiber Reinforced Polyurea

Aged structures and structures constructed based on outdated non-seismic design codes should be retrofitted to enhance their strength, ductility, and durability. This study evaluates the structural performance of reinforced concrete (RC) columns enhanced via polyurea or glass fiber reinforced polyurea (GFRPU) strengthening. Four RC column specimens, including a reference specimen (an unstrengthened column), were tested to evaluate the parameters of the strengthening materials and the strengthened area. The tests were carried out under a combined constant axial compressive load and quasi-static cyclic loading. The experimental results show that the composite strengthening provides lateral confinement to the columns and leads to enhanced ductility, shear-resistance capacity, and dissipated energy. The shear strength provided by the composites depends on the degree of lateral confinement achieved by the composite coating. The specimens finally failed through the development of diagonal tension cracks within the potential plastic hinge regions. The specimen treated with GFRPU strengthening showed greater strength and dissipated more energy than the specimen treated with polyurea strengthening. Furthermore, by modifying ATC-40, this study proposed an equation to estimate the shear capacity provided by the composites.

Global Retrofitting Strategies for an Existing Three-storied RC School Building in Mandalay, Myanmar

Low to severe earthquakes occur around the world every year, damaging and causing structural failure in buildings. Consequently, seismic improvements are required for existing buildings that are vulnerable to damage by seismic forces. The objective of this study was to investigate retrofitting strategies in terms of their sustainability. Mandalay, Myanmar, was selected as the study area as it is located near the Sagaing fault, which itself is in a strong earthquake zone (seismic zone 4). A three-storied RC building with a non-seismic design was selected as a case study building. An investigation was carried out into the performance and vulnerability of the building under three earthquake hazard levels. The vulnerability index value was calculated using the Priority Index method. Meanwhile, non-linear static pushover analysis was performed to investigate the performance of the existing building using SAP2000 V14 software. Four different types of retrofitting strategies were considered, namely reinforced concrete shear walls with openings, reinforced concrete shear walls without openings, steel plate shear walls, and finally steel bracing. Among these, it was found that the use of steel plate shear walls was the best retrofitting technique, owing to it having the best performance along with the lowest displacement. Its performance level reached up to the Immediate Occupancy (IO) level even under the conditions of a Maximum Consider Earthquake (MCE).

A simplified performance based approach for the evaluation of seismic performances of steel frames

Recent earthquakes have underlined the need for a prompt classification of buildings in terms of seismic performances. The capacity of a structure can be assessed by means of inelastic analysis, requiring sophisticated numerical procedures. Therefore, a simplified method for the evaluation of seismic performance of steel frames to be used in the everyday practice is proposed in this paper. This method can evaluate the capacity of an existing building without resorting to any static non-linear or dynamic non-linear analyses. To set up the method, an extensive parametric analysis was carried out on 420 frames designed according to 3 different approaches: the first is the Theory of Plastic Mechanism Control and ensures the design of structures characterized by global collapse mechanism (Global Moment Resisting Frames (GMRFs)), the second is based on the application of the Eurocode 8 requirements (Special Moment Resisting Frames (SMRFs)) while the third is a non-seismic design, based on sizing for vertical loads only (Ordinary Moment Resisting Frames (OMRFs)).

Numerical Modelling and Simulation of the In‐Plane Response of a Three‐Storey Masonry‐Infilled RC Frame Retrofitted with TRM

A numerical study was conducted to investigate the in‐plane behavior of a masonry‐infilled reinforced concrete (RC) frame retrofitted with textile‐reinforced mortar (TRM). A two‐dimensional finite element model was developed using DIANA finite element analysis (FEA) software to simulate the 2 : 3 scaled three‐storey masonry‐infilled RC frame retrofitted with TRM that was studied experimentally in the past. The three‐storey structure used in the test was with a nonseismic design and detailing, and was subjected to in‐plane displacement‐control cyclic loading. The current study evaluates the capabilities of a representative numerical model to simulate the results of the experimental test, and after the calibration of the numerical model sensitivity analysis and parametric study were performed. In order to create an accurate numerical model, suitable constitutive models, based on the smeared crack approach, were used to characterize the nonlinear response of concrete, masonry infill, and TRM. The calibration of the models was based on the experimental results or inverse fitting based on optimizing the simulation of the response. The numerical model proved capable of simulating the in‐plane behavior of the retrofitted masonry‐infilled RC frame with good accuracy in terms of initial stiffness, and its deterioration, shear capacity, and cracking patterns. The calibrated model was then used to perform sensitivity analysis in order to examine the influence of infill‐frame interface properties (tangential and normal stiffness) on the behavior of the retrofitted infilled frame. The numerical results showed that the gap opening is influenced significantly by the stiffness of the interface. In addition, a parametric study was performed in order to evaluate the importance of the full‐bond condition between the TRM and the masonry‐infilled RC frame. The numerical results indicate that the composite action between the TRM and the masonry‐infilled RC frame improves the global stiffness and lateral resistance of the infilled frame, and it reduces the gap opening between the masonry infill and the RC frame.

Numerical Modeling of Masonry-infilled RC Frame

Background:The behavior of masonry-infilled Reinforced Concrete (RC) frame structures during an earthquake, has attracted the attention of structural engineers since the 1950s. Experimental and numerical studies have been carried out to investigate the behavior of masonry-infilled RC frame under in-plane loading.Objective:This paper presents a numerical model of the behavior existing masonry-infilled RC frame that was studied experimentally at the University of Patra. The objective of the present study is to identify suitable numerical constitutive models for each component of the structural system in order to create a numerical tool to model the masonry infilled RC frames in-plane behavior by accounting the frame-infill separation.Methods:A 2D masonry-infilled RC frame was developed in DIANA Finite Element Analysis (FEA) software and an eigenvalue and nonlinear structural cyclic analyses were performed. It is a 2:3 scale three-story structure with non-seismic design and detailing, subjected to in-plane cyclic loading through displacement control analysis.Results:There is a good agreement between the numerical model and experimental results through a nonlinear cyclic analysis. It was found that the numerical model has the capability to predict the initial stiffness, the ultimate stiffness, the maximum shear-force capacity, cracking- patterns and the possible failure mode of masonry-infilled RC frame.Conclusion:Therefore, this model is a reliable model of the behavior of masonry-infilled RC frame under cyclic loading including the frame-infill separation (gap opening).

Validation of Corner Beam-column Joint’s Hysteresis Loops between Experimental and Modelled using HYSTERES Program

The beam - column joint is an important part of a multi-storey RC building as it caters for lateral and gravitational load during an earthquake event. The beam-column joints should have a medium to high ductility for transferring the earthquake load and gravity load to the foundation. By designing multi-storey RC buildings using Eurocode 8 can avoid any diagonal shear cracks in column which is a major problem in non-seismic design buildings using British Standard (BS8110). This paper presents the experimental hysteresis loops of monolithic corner beam-column joints of multi-storey building which had been designed using Eurocode 8 and tested under in-plane lateral cyclic loading. The experimental hysteresis loops of corner beam-column joint was compared with modelled using the HYSTERES program. The full-scale corner beam-column joint of a two story precast school building was designed, constructed, tested and modelled is presented herein. The seismic performance parameters such as lateral strength capacity, stiffness, ductility and equivalent viscous damping were compared between experimental and modelled hysteresis loops. The experimental hysteresis loops have similar shape with the modeling hysteresis loops with small percentage differences between them.

Estimation on amount of steel reinforcement for six storey hospital building with seismic design consideration in Malaysia

A series of earthquakes such as Sumatra-Andaman earthquake on 26 December 2004, Nias earthquake on 28 March 2005, and Bengkulu earthquake on 12 December 2007 had influences to a series of subsequence local earthquake in Peninsular Malaysia. Recently, East Malaysia especially Sabah has become earthquake prone region due to local fault. Hence, Malaysia is not totally free from seismic activities. Therefore, in 2009 Malaysian Public Work Department had concluded that it was worthwhile to consider seismic design input in new building which are located in medium to high risk earthquake zone. The effect of seismic design implementation on cost of materials has become an interesting topic to discuss. This study presents the estimation of steel reinforcement required for six storey hospital building in Malaysia with seismic design consideration. Two parameters namely as reference peak ground acceleration and class of ductility has been considered as variable. The result shows that the total amount of steel reinforcement is increased from 6%, 116%, 257%, and 290% for peak ground acceleration equal to 0.04g, 0.08g, 0.12g, and 0.16g, respectively compared to the non-seismic design counterpart. Beside, total amount of steel reinforcement is increase around 6% and 145% for ductility class medium and ductility class low, respectively compared to its non-seismic design counterpart.

Establishing new brittle fracture provisions for the Australasian steel structures standards

This paper develops a new method to select steel grades manufactured to Australian and New Zealand standards. The current materials selection procedure is currently given in the design standards AS 4100, NZS 3404.1 and AS/NZS 5100.6, which is based on test data on the notch toughness characteristics from a previous generation of steel products originally manufactured in Australia or New Zealand. The existing procedure is limited to temperatures down to −40 °C. Moreover, it does not consider the effect of welding, detailing, stress utilisation, seismic loading rates, defects and other important factors. This paper includes a critical review of other international material selection procedures, before preparing a new design method based on fracture mechanics. The method extends the temperature range down to −120 °C, which is much lower than considered in many other international standards. It also includes New Zealand specific requirements for seismic loading rates. In comparison with the new method, it is demonstrated that the current materials selection procedure is much more conservative for plate thickness up to 75 mm for non-seismic design. The paper presents selection tables that can be considered for the development of new brittle fracture provisions for future versions of the Australian and New Zealand steel structures design standards.

Seismic retrofit of beam–column joints using prestressing wire

An effective external prestressing technique is presented for the seismic retrofit of reinforced concrete beam–column joints with prestressed high-strength steel wires. This method is to improve the seismic performance and enhance the shear strength of beam–column joints with non-seismic design as well as to overcome the shortcomings of traditional seismic retrofitting techniques for the joints. Six large-scale interior beam–column joints were tested under reversed cyclic loading, where five were strengthened by the proposed technique and one was un-retrofitted as a control specimen. Particular emphasis was placed on the effects of the ratio of prestressed high-strength steel wires, prestressing level of wires and polymer grout layer. Test results showed that the joint shear capacity was increased significantly and cracks in beam–column joints were controlled effectively after retrofitting. All retrofitted joint specimens failed in a ductile mode of beam flexural failure, whereas the control specimen failed in a brittle mode of joint shear failure. In addition, the energy dissipation capacity as well as ductility of the retrofitted joint specimens was enhanced significantly compared with the un-retrofitted specimen.

Ductility design of RC columns. Part 2: extent of critical zone and confinement reinforcement

ABSTRACTThe current Hong Kong concrete design code (HKConcrete2013), which is a non-seismic design code, includes provisions of the design of confinement zone in reinforced concrete (RC) columns. Whether or not these provisions can be adopted in the development of the new design code of structures for seismic resistance remains uncertain. A thorough scientific investigation with a comprehensive statistical analysis on the seismic behaviour of RC columns under different levels of the axial compression ratio (ACR) and concrete confinement has been conducted and presented in the companion paper [1], where the use of the ACR limits for controlling the seismic performance of various types of RC columns is proposed. The present paper addresses the important aspect of the confinement zone length and the design of confinement reinforcement in RC columns under different levels of the ACR. The theoretical background of the confinement zone is presented and the requirements of the prevailing design standards for des...

Behavior of Damaged Exterior RC Beam-Column Joints Strengthened by CFRP Composites

This paper presents an experimental investigation on the behavior of retrofitted beam-column joints subjected to reversed cyclic loading. The experimental program comprises 8 external beam-column joint connection subassemblages tested in 2 phases; one was the damaging phase and second was the repairing phase. The Beam-column joints were designed only for gravity loads. The joints had no beam-column joint transverse reinforcement and special stirrups in beam and column critical zones. These Non-Seismically designed (NS) joints were damaged with different levels at the first phase of the experiment. In the second phase, the damaged joints were strengthened with externally bonded carbon-fibre-reinforced polymers (C-FRP) sheets. From the observed responses of the examined specimens it can be deduced that the technique of externally bonded retrofitting (EBR) using C-FRP sheets is appropriate for the rehabilitation of the joints seismic capacity. This technique had a significant improvement of the energy dissipation and the performance level and finally it leads to improved type of damages compared with the damage modes of the specimens during the initial loading. Shortcomings of the application of C-FRP sheets for practical use are also pointed out.

Experimental investigation on the seismic anchorage behavior of headed bars based on full-size specimens of exterior and interior beam–column joints

The design of headed bars in interior and exterior beam–column joints to ensure satisfactory seismic anchorage performance has recently become a very important issue. This work investigates the seismic anchorage behavior of headed bars using 12 groups of full-size specimens of exterior and interior beam–column joints and suggests design requirements for headed bars in such joints. On the basis of the experimental investigation, this work comprehended the seismic anchorage behavior of headed bars using full-size specimens of exterior and interior beam–column joints and suggested design requirements for headed bars in such joints. Additionally, the application of headed bars with spliced and butted types on interior beam–column joints is also proved in this work. Therefore, based on the experimental results, the minimal required net spacing of headed bars can be set at 2.2 db, instead of 4.0 db, for seismic designs, and the minimal required anchorage length in ACI 318-11 for non-seismic design members can be used in seismic members.