Mid-rise RC Research Articles

3D Methods for Examining Soil–Building Interaction for Nonlinear Soil Behavior Based on an Input Wave Field

AbstractThis paper proposes three-dimensional (3D) simplified nonlinear methods for examining the soil–building interaction for nonlinear behavior of soils based on an input seismic wave field. A seismic wave field is defined as seismic waves propagating in a 3D medium. The proposed 3D methods were developed on the basis of the 3D linear method, which was recently proposed to adequately treat seismic surface waves trapped by a several-kilometer-deep underground structure. To demonstrate the feasibility of the proposed methods, interaction analyses of a midrise RC building and a wood building were performed in the reclaimed zone of Tokyo Bay in the cases of soils with linear, nonlinear, and liquefaction behavior for the 1923 Kanto earthquake. These interaction analyses provide a reasonable evaluation of building performance. In particular, building responses became excessively large, following extremely large increases in the amplitudes of surface waves in liquefied soils. The building responses provide si...

FRP versus traditional strengthening on a typical mid-rise Turkish RC building

This paper investigates the limits and efficacies of the Fiber Reinforced Polymer (FRP) material for strengthening mid-rise RC buildings against seismic actions. Turkey, the region of the highest seismic risk in Europe, is chosen as the case-study country, the building stock of which consists in its vast majority of mid-rise RC residential and/or commercial buildings. Strengthening with traditional methods is usually applied in most projects, as ordinary construction materials and no specialized workmanship are required. However, in cases of tight time constraints, architectural limitations, durability issues or higher demand for ductile performance, FRP material is often opted for since the most recent Turkish Earthquake Code allows engineers to employ this advanced-technology product to overcome issues of inadequate ductility or shear capacity of existing RC buildings. The paper compares strengthening of a characteristically typical mid-rise Turkish RC building by two methods, i.e., traditional column jacketing and FRP strengthening, evaluating their effectiveness with respect to the requirements of the Turkish Earthquake Code. The effect of FRP confinement is explicitly taken into account in the numerical model, unlike the common procedure followed according to which the demand on un-strengthened members is established and then mere section analyses are employed to meet the additional demands.

Determination of lateral strength and ductility characteristics of existing mid-rise RC buildings in Turkey

This paper presents a comprehensive work on determination of yield base shear coefficient and displacement ductility factor of three to eight story actual reinforced concrete buildings, instead of using generic frames. The building data is provided by a walkdown survey in different locations of the pilot areas. Very detailed three dimensional models of the selected buildings are generated by using the data provided in architectural and reinforcement projects. Capacity curves of the buildings are obtained from nonlinear static pushover analyses and each capacity curve is approximated with a bilinear curve. Characteristic points of capacity curve, the yield base shear capacity, the yield displacement and the ultimate displacement capacity, are determined. The calculated values of the yield base shear coefficients and the displacement ductility factors for directions into consideration are compared by those expected values given in different versions of Turkish Seismic Design Code. Although having sufficient lateral strength capacities, the deformation capacities of these typical mid-rise reinforced concrete buildings are found to be considerably low.

SEISMIC HAZARD ASSESSMENT OF SCHOOL BUILDINGS IN PENINSULAR MALAYSIA

Peninsular Malaysia is located on the southern edge of the Eurasian Plate. However, it is close to a seismically active plate boundary, the inter-plate boundary between the Indo-Australian and Eurasian Plates. Occasionally, tremors can be felt throughout the region even when active faults are located several hundred kilometers away. Lessons learnt from past events, active earthquakes located far from the existing building can cause potential damage. Thus, fragility curves become an essential tool to estimate probability of building damage caused by seismic ground motions. In this study, the response of low-rise and mid-rise RC school buildings located in various soil conditions within Peninsular Malaysia under earthquake excitation was investigated by performing dynamic response spectrum analysis. These buildings were analysed using DIANA 9.3 structural analysis program and subjected to a range of low to high seismic ground motions to determine the performance damage state of each type of building. All structural elements were modeled using solid brick finite-element. Correspondingly, the fragility curves were developed using the log-normal distribution for structural response. The effects of various soil conditions on the response of the buildings were also investigated. The results indicated that the effect of soil parameters had a significant effect on the outcome of the fragility curves. However, the risk of these existing school buildings at a location in the northern part of Peninsular Malaysia showed the highest probability of exceeding each damage state. On the contrary, the risk of the existing school buildings at a location in the central part of Peninsular Malaysia was the lowest.
 
 Keywords: Interaction, fragility curves, soil-structure

Seismic response of RC frame structures strengthened by reinforced masonry infill panels

The performance of masonry infilled frames during the past earthquakes shows that the infill panels play a major role as earthquake-resistant elements. Experimental observations regarding the influence of infill panels on increasing stiffness and strength of reinforced concrete structures reveal that such panels can be used in order to strengthen reinforced concrete frames. The present study examines the influence of infill panels on seismic behavior of RC frame structures. For this purpose, several low- and mid-rise RC frames (two-, four-, seven-, and ten story) were numerically investigated. Reinforced masonry infill panels were then placed within the frames and the models were subjected to several nonlinear incremental static and dynamic analyses. In order to determine the acceptance criteria and modeling parameters for frames as well as reinforced masonry panels, the Iranian Guideline for Seismic Rehabilitation of Existing Masonry Buildings (Issue No. 376), the Iranian Guideline for Seismic Rehabilitation of Existing Structures (Issue No. 360) and FEMA Guidelines (FEMA 273 and 356) were used. The results of analyses showed that the use of reinforced masonry infill panels in RC frame structures can have beneficial effects on structural performance. It was confirmed that the use of masonry infill panels results in an increment in strength and stiffness of the framed buildings, followed by a reduction in displacement demand for the structural systems.

Load carrying system characteristics of existing Turkish RC building stock

Seismic performance and loss assessment studies for stock of buildings are generally based on representative models due to extremely large number of vulnerable buildings. The main problem is the proper reflection of the building stock characteristics well enough by limited number of representative models. This study aims to provide statistical information of structural parameters of Turkish building stock for proper modeling using a detailed inventory study including 475 low and mid-rise RC building with 40351 columns and 3128 beams for member properties. Thirty-five different parameters of existing low and mid-rise Turkish RC building stock are investigated. An example application is given to express use of given statistical information. The outcomes of the current study and previous studies are compared. The comparison shows that the previous studies have guidance for limited number of parameters while the current study provides considerably wide variety of structural and member parameters for proper modeling.

Seismic Responses of Two RC Buildings and One Wood Building Based on an Input Wave Field

AbstractA recently proposed three-dimensional (3D) linear method for examining soil-building interactions based on an input seismic wave field is, after some improvements, applied to estimate seismic building responses in the reclaimed zone of Tokyo Bay, where ground motions include a considerable amount of surface waves, thus reconfirming the effects of the method in a different situation. A seismic wave field involves seismic waves propagating in a 3D medium. The proposed method was developed with the goal of adequately treating seismic surface waves trapped by a (several-kilometers) deep underground structure in a soil-building interaction system. Two simulations were carried out. The first simulation successfully reproduced surface, downhole, and building accelerograms that were recorded at one borehole station during two medium-sized earthquakes. In the second simulation, seismic responses of a midrise RC model building and a wood model building were favorably calculated at the other borehole station...

高密度常時微動計測に基づく軟弱地盤に立地する杭基礎中層RC造建物の振動特性と動的相互作用効果

We performed high density microtremor measurements and earthquake observation for a mid-rise RC building which is prepared for seismic retrofitting. S-wave velocity profile of surface around soft ground is estimated and the soil-structure interaction effect on the dynamic characteristics of the building is indicated. Based on the high density measurement, we estimate that the foundation-input-motion and denote the complex three-dimensional vibration characteristics including out-of-plane deformation of the first floor slab.

Flexure and Shear Deformation of GFRP-Reinforced Shear Walls

AbstractExperimental results of midrise RC shear walls under quasistatic cyclic loading were used to investigate the interaction of flexural and shear deformations. Four large-scale shear walls—one reinforced with steel bars and three totally reinforced with glass fiber–reinforced polymer (GFRP) bars—were tested to failure where the behavior was dominated by flexure. It was found that relying on the diagonal displacement transducers tended to overestimate shear deformations by 30 to 50%. To correct the shear deformations, the center of rotation of the tested shear walls was evaluated. Based on experimental results, the fundamental equation of flexural deformation obtained values of the center of rotation (α). Using the suggested values of α produced consistent results for the flexure and shear deformations. Decoupling the total deformation of the tested shear walls into flexural and shear deformations was discussed. Using elastic materials (GFRP bars) gave uniform distributions of shear strains along the ...

Selection of the Most Unfavorable Real Ground Motions for Low- and Mid-rise RC Frame Structures

The goal of this article is to select those real (or recorded) ground motions capable of exposing the low- and mid-rise reinforced concrete frame structures to an extreme limit state. By performing correlation analyses, two optimal intensity measures are first selected to represent the ground motion damage potential. Then based on each record's damage potential, four subsets of strong ground motions, referred to as the most unfavorable ground motions, are identified and preliminarily confirmed to be applicable to the low- and mid-rise RC frame structures.

Assessment of seismic fragility curves for existing RC buildings in Algiers after the 2003 Boumerdes earthquake

The main purpose of this paper is to develop seismic fragility curves for existing reinforced concrete, RC, buildings based on the post earthquake field survey and the seismic performance using capacity design. Existing RC buildings constitute approximately 65% of the total stock in Algiers. This type of buildings, RC, was widely used in the past and chosen as the structural type for the future construction program of more than 2 millions apartments all over Algeria. These buildings, suffered moderate to extensive damage after the 2003 Boumerdes earthquake, on May 21st. The determination of analytical seismic fragility curves for low-rise and mid-rise existing RC buildings was carried out based on the consistent and complete post earthquake survey after that event. The information on the damaged existing RC buildings was investigated and evaluated by experts. Thirty four (34) communes (districts) of fifty seven (57), the most populated and affected by earthquake damage were considered in this study. Utilizing the field observed damage data and the Japanese Seismic Index Methodology, based on the capacity design method. Seismic fragility curves were developed for those buildings with a large number data in order to get a statistically significant sample size. According to the construction period and the code design, four types of existing RC buildings were considered. Buildings designed with pre-code (very poor structural behavior before 1955), Buildings designed with low code (poor structural behavior, between 1955-1981), buildings designed with medium code (moderate structural behavior, between 1981-1999) and buildings designed with high code (good structural behavior, after 1999).

Influence of infill distribution and design typology on seismic performance of low- and mid-rise RC buildings

A growing attention has been addressed to the influence of infills on the seismic behavior of Reinforced Concrete buildings, also supported by the observation of damage to infilled RC buildings after severe earthquakes (e.g. L’Aquila 2009, Lorca 2011). In this paper, a numerical investigation on the influence of infills on the seismic behavior of four different case study buildings is carried out: four- and eight-storey buildings, designed for seismic loads according to the current Italian technical code or for gravity loads only according to an obsolete technical code, are considered. Seismic capacity at two Limit States (Damage Limitation and Near Collapse) is assessed through static push-over analyses, within the N2 spectral assessment framework. Different infill configurations are considered (Bare, Uniformly Infilled, Pilotis), and a sensitivity analysis is carried out, thus evaluating the influence of main material and capacity parameters on seismic response, depending on the number of storeys and the design typology. Fragility curves are obtained, through the application of a Response Surface Method. Seismic performance is also expressed in terms of failure probability, given a reference time period.

Effect of Shear Wall Area to Floor Area Ratio on the Seismic Behavior of Reinforced Concrete Buildings

AbstractAn analytical study is performed to evaluate the effect of shear wall area to floor area ratio on the seismic behavior of midrise RC structures. For this purpose, 24 midrise building models that have five and eight stories and shear wall ratios ranging between 0.51 and 2.17% in both directions are generated. Then, the behavior of these building models under earthquake loading is examined by carrying out nonlinear time history analyses. In the analyses, seven different ground motion records are applied to the building models, and the average of the obtained data is used in the evaluation of the seismic performance. Main parameters considered in this study that affect the overall seismic performance of the buildings are the roof and interstory drifts and the base shear responses. The analytical results indicate that at least 1.0% shear wall ratio should be provided in the design of midrise buildings to control the drift. In addition, when the shear wall ratio increases beyond 1.5%, it is observed th...

Experimental study on seismic behavior of mid-rise RC shear wall with concealed truss

In this paper, mid-rise shear wall with concealed truss was proposed. This new composite shear wall includes two kinds of composition: one is the composition of two bearing systems, including truss and shear wall, and the other is the composition of two materials, including steel and concrete. Therefore, it is a double composite shear wall. The experimental study on the seismic behavior of six 1/3 scale mid-rise shear walls, including an ordinary mid-rise shear wall, a mid-rise shear wall with steel frame, and four mid-rise shear wall with concealed truss made of different materials, was studied. Based on the experimental study, the stiffness and its attenuation, bearing capacity, ductility, hysteretic property, energy dissipation, and failure phenomena of each shear wall were contrastively analyzed. The formulas of bearing capacity and stiffness were established. The results obtained from the formulas and those from experiment are in good agreement. Some suggestions for seismic design of shear wall are given in this paper. The experimental results show that the seismic behavior of the mid-rise shear wall with steel frame and that of every truss with different materials is obviously improved.

볼팅 고정 채널 형강 보강재를 이용한 비좌굴 Knee Bracing System의 내진성능에 대한 실험 연구

본 연구에서는 1층 1경간 실제크기의 가력 프레임에서 내진보강에 적합한 비좌굴 knee brace을 설치하여 주기하중을 통해 가새의 지진저항능력을 실험하였다. 볼트 고정 채널이 이용된 비좌굴 knee brace는 지진력에 저항하는 코어와 두 개의 철골 플레이트로 만들어졌고 단면의 형태는 코어의 국부좌굴과 횡좌굴에 저항하도록 하였다. 비좌굴 kneebrace는 현장에서 조립이 용이하고, 시공방법 또한 간단하여 공간에 제약이 있는1층에 필로터를 가진 중저층 RC건물의 내진 보수/보강에 효과적으로 사용할 수 있다. 각 실험체에 대한 변수로 중심코어의 크기와 외부 보강재의 크기, 가이드 플레이트의 유무 등으로 정하였으며, 실험을 통해 얻어진 힘-변위 이력곡선을 통해 중심코어의 크기가 가장 큰 영향을 미치는 것으로 나타났다. 또한 가이드 플레이트의 유무에 따라 압축강도 수정계수와 파괴형태가 달라지는 것을 알 수 있었다. 각 실험체에 대한 결과는 AISC 2005 Seismic Provisions 규정에서 제시한 누적 연성도와 누적 소산에너지 측면에서도 충분한 효과를 발휘하는 것으로 나타났다. In this study, the seismic performance of the Buckling Restrained Knee Bracing (BRKB) system was evaluated through a pin-connected 1-bay 1-story frame. The BRKB system using a bolted channel section developed was composed of a steel plate as a load-resisting core member and two channel sections as a restrainment of the local and global buckling of the core plate. The main purpose of the BRKB system is to be used as an effective tool to re-strengthen/rehabilitate old low- and mid-rise RC frame buildings, which do not have enough seismic resistance to earthquake loadings. The main variables for the test specimens were the size of the core plates, stiffeners and the use of guide plates. The test results showed that the size of the core plate, which was the main element for the load-resisting member, was the most important parameter to achieve ductile behavior under tension as well as compression, until the maximum displacement exceed twice the design drift limit given by the AISC Seismic Provisions.

Comparative performance of sub-standard interior reinforced concrete beam–column connection with various joint reinforcing details

This paper discusses the effect of some important parameters on cyclic behavior of sub-substandard interior beam–column connection. The objective is to investigate the effect of joint shear stress, anchorage bond of longitudinal beam bar within the joint and horizontal joint reinforcements on the joint performance. The experiment consisted of five half-scale beam–column specimens. The control specimen (J1) represented a typical non-ductile beam–column joint in mid-rise RC buildings constructed in low seismic zone. In specimen J2, the bond between concrete and longitudinal bars was completely removed initially. In specimen J3A and J3B, a substantial amount of horizontal joint reinforcement was provided in joint core. In specimen J4, the column size was enlarged to reduce shear stress in joint. The experimental result demonstrated brittle joint shear failure in control specimen (J1), specimens J3A and J3B, beam splitting failure in specimen J2 and ductile flexural failure in specimen J4. Based on experimental results, it was found that the initial lost of bond did not cause a substantial reduction in joint capacity. Moreover, provision of substantial horizontal joint reinforcements in specimen J3A and J3B did not produce a comparable improvement in the seismic performance. With increased column size in specimen J4, the energy dissipation characteristics were greatly improved as indicated by large spindle-shaped cyclic loops.

Preliminary report: Kocaeli (Izmit) earthquake of 17 August 1999

The M w 7.4 Kocaeli (Izmit) earthquake occurred at 3:01 am local time 17 August 1999 on the east–west trending north strand of the North Anatolian Fault Zone (NAFZ), about 100 km SE of Istanbul, Turkey. The approximately 125 km long fault rupture and high damage area follows or is close to the south shore of Izmit Bay, and the extension of that line to the east, and has predominantly 2.2 m right lateral displacement, from Adapazari in the east to Yalova in the west. Significant vertical fault scarps of as much as 2 m occur at several locations. Peak ground accelerations of approximately 0.4 g were recorded near the fault, and liquefaction and subsidence were observed on the shores of Izmit Bay and Lake Sapança. Several million persons live in the Izmit region, which has experienced rapid growth and heavy industrialization in the last two decades. The predominant building type is mid-rise non-ductile RC frames with hollow clay tile infill, thousands of which collapsed in a ‘pancake’ mode. Confirmed dead are approximately 17,000. Estimates of population requiring short to long-term shelter range from 400,000 to 600,000. Lifelines generally performed well, with the exception of underground piping in the heavily affected areas, where major damage is reported. Electric power, highways, rail and telephone were generally functional within several days following the earthquake, and the modern Izmit Water Project (the regional water supply and transmission system) was only lightly damaged and fully functional. The modern Izmit gas distribution system similarly sustained relatively little damage. Fires occurred in a number of collapsed buildings but were generally confined to building of origin. Two fires broke out at the Tupras oil refinery, one of which burned for several days.