The Investigation of the Sustainability of the Existing Steel Pedestrian Overpasses According to the New Steel Structure Regulation: The Sample of Ankara City

*Gökhan Durmuş and Akın Ünal* 

#### **Abstract**

The current state of the steel pedestrian overpasses, which were selected from different regions of Ankara, was designed in terms of engineering. Three pedestrian overpasses, which are important in terms of loss of life and property of the city, have been identified. In this study, it will be determined whether pedestrian overpasses dimensioned according to linear analysis primarily meet the design criteria according to the old steel structure regulation. In addition, the conformity of the design rules in the regulation on principles of design, calculation, and construction of steel structures entered into force in 2016 will be investigated. The conformity of crosswalk that is the ductility level of the steel frame and high ductility steel frame entered into force in 2016 will be investigated. As a result, internal forces of selected column and beam elements are given in graphs and tables at the result of the study comparatively.

**Keywords:** steel structure design, linear analysis, nonlinear analysis, overpass, steel construction

#### **1. Introduction**

Turkey is located on an active earthquake zone and has recently entered a rapid construction process. Especially in the recent years, there has been an increase in the application area of steel structures. However, the design rules of steel structures are particularly important. In this direction in Turkey, on September 1, 2016, Design, Calculation and Construction Principles of Steel Structures (ÇYTHY), and on January 1, 2019, Turkey Earthquake Building Regulation (TBDY) entered into force.

The ratio of steel structures to all structures is about 50% in Europe and America. This ratio is a very small value, such as 0.3% in Turkey. Although the exact values are not known, it is thought that steel structures are used in industrial buildings by 6% and in residential buildings by 1–2%. In Turkey, most of the steel structures are industrial-type structures [1, 2]. The remaining part consists of towers, energy infrastructures, bridges, pedestrian overpasses, and commercial structures. Application of multistory steel structures is very little. The reason of

this situation is being high cost of steel structures. Even if this statement applies to normally reinforced concrete structures, steel structures should be preferred in earthquake-resistant construction designs and weak floors. The hard part of the steel structures is the process of production, construction, and assembly. More skilled workers, engineers, and architects are required in this process. Although these stages are difficult, the advantages of steel structures should not be ignored. Steel structures:


 As a whole, steel structures are more advantageous. The cost of the buildings is usually taken as the unit area price and the unit price of the materials. But when we look at this point of view, we ignore all the advantages of steel structures. When the factors such as sustainability, earthquake effect, building net usage area, and basic cost are added to the comparison, steel structures are more advantageous [3–6].

#### **2. Comparison of regulations**

 When we look at the regulations regarding the steel structure design in Turkey up to the present day, most known, which is TS648, which entered into force in 1980, is the Regulation of Calculus and Construction Rules of Steel Structures. In addition to this, TS 4561, which entered into force in 1985, was used for calculation of steel structures according to the plastic theory. Then TS 4561 was repealed and replaced by the TS EN 1993-1-1 standard. TS 648 is outdated, and a new regulation has been published after 36 years. On September 1, 2016, the Regulation on Design, Calculation and Construction of Steel Structures (ÇYTHYE) entered into force. The new steel structure regulation has been developed based on the American Regulations AISC 360–10 and AISC 360–16 (draft), which are up to date and valid at the international level. Design of steel structures is made according to boundary conditions. There are two boundary conditions, one for strength limit and one for usability limit. The structures are first dimensioned for the boundary condition based on external influences and then checked for usability limit condition [7, 8]. The main approaches aiming the design of the building systems as earthquake resistant are divided into two, according to the *strength* and *performance* [7].

**Design according to strength:** there are three basic components in this approach—resistance criterion, stiffness criteria, and system ductility.

*The Investigation of the Sustainability of the Existing Steel Pedestrian Overpasses… DOI: http://dx.doi.org/10.5772/intechopen.87836* 

**Design by performance:** This design approach consists of three parts. First of all, the structure is projected to design earthquake load. Second, service loads are also included in the dimensioned depressant load. Finally, the largest earthquake loads are applied to the structure. This approach is one of the most suitable methods for evaluating the performance of high-rise buildings, floor-insulated buildings, and other existing private buildings.

#### **2.1 Design with TS 648**

The TS 648 covers element designs in general. Safety stresses are based on the calculation method. This regulation is only appropriate for buildings. Nonbuilding structures are not covered [9].

#### *2.1.1 Tensile force effect*

 The tensile safety stress (σ<sup>ç</sup>*em*) is calculated with the following formula in the useful section:

$$
\sigma\_{\mathfrak{g}em} \le 0.6 \,\sigma\_a \tag{1}
$$

 In addition, this value should not be more than half of the tensile strength (σ*d*):

$$
\sigma\_{\text{ç}em} \le \mathbf{0}.\mathsf{G}\sigma\_d \tag{2}
$$

 Depending on the load situation, TS 648 suggests that the slenderness of the steel profile according to tensile strength, the minimum, should not be less than 250 mm (λ ≤ 250).

#### *2.1.2 Pressure force effect*

In central pressure-driven bars, buckling calculation method is given in the regulation. The bars under the effect of pressure outside the conditions in the regulation are determined according to the rules required by that situation. The slenderness of the bars under pressure must not be more than 250. The safety stresses are calculated by the following formula:

$$
\alpha \* \frac{S}{F} \le \sigma\_{\xi^{em}} \tag{3}
$$

#### *2.1.3 Bending moment effect*

If three or more support continuous roof beams and purlins can be calculated with other methods, the load and support openings can be calculated with the following bending moment formulas:

$$\text{Edge spans for distributed load:} \, M = q \cdot l^2 / \mathbf{11} \tag{4}$$

$$\text{Inside spans:}\\M = q \cdot l^2 / 18 \tag{5}$$

#### *2.1.4 Axial pressure and bending moment effect*

The buckling verification and the non-buckling stress determination in the bars running Mx and/or My bending moments with a central pressure force or eccentric pressure force are calculated by the related formulas.

#### *2.1.5 Buckling effect*

If the loads causing the bending in addition to torsional loads do not pass through the slip center of the cross section of the element, the bar is subjected to torsional loads. Normal stresses and shear stresses occur due to torsional loads. These stresses are added to the stresses of the other effects, and the maximum stress values are calculated.

#### **2.2 Design with ÇYTHYE**

There are two methods of design according to the strength limit condition in ÇYTHYE. One of them is load and resistance factor design (LRDF). The other is allowable strength design (ASD) method, which is similar to the safety stress method [10, 11].

 **Load and resistance factor design:** LRFD is based on the principle that the design strength ∅R*n* is equal to or greater *than the value* R*u*, calculated by the load combinations to be used in this design method. According to this design method, the equation is expressed as follows:

$$\mathbf{R}\_u \preceq \mathcal{Q} \,\mathbf{R}\_n \tag{6}$$

 **Allowable strength design:** ASD is based on the principle of safe strength, and R*n*/Ω value is equal to or greater than the value of *Ra*, calculated by the load combinations to be used in this design method (**Figure 1**). According to this design method, the equation is expressed as follows:

$$R\_{\mathfrak{a}} \subset \mathbb{R}\_n / \mathfrak{Q} \tag{7}$$

 Design strength must be equal to or greater than the required strength value for the building to remain in the safe zone. In both methods, the loads on the structure are multiplied by the load coefficients, and the required strength is determined. But the load combinations of the two methods are different from each other. In ASD method, load coefficients are generally considered to be 1.0. By adjusting the safety coefficients, the same results are achieved in both methods.

**Figure 1.**  *Design strengths.* 

*The Investigation of the Sustainability of the Existing Steel Pedestrian Overpasses… DOI: http://dx.doi.org/10.5772/intechopen.87836* 

#### *2.2.1 Axial tensile force effect*

 The slenderness ratio in the elements subjected to tensile force should be less than 300 ( *Lc*/*i* ≤ 300). However, this condition is invalid for steel cables and shafts. The tensile force strength; the design tensile force strength for LRFD; the tensile force strength of ∅*t*/*Tn*, or ASD; the minimum strength value calculated according to *Tn*/Ω*t*; axial tensile force element; yield boundary status; and breaking boundary conditions shall be taken.

#### *2.2.2 Axial pressure force effect*

 These elements are classified according to cross-sectional conditions as delicate and non-delicate cross sections. The slenderness rate calculated according to the rules in the regulation should be less than 200 (*Lc*/*i* ≤ 200). Pn shall be taken as the smallest of the resistances to be calculated from the bending, torsional buckling and/or torsional bending boundary conditions around any of the cross-sectional axes of the element under axial pressure force, with characteristic axial compressive force strength.

#### *2.2.3 Bending moment effect*

In the case of a simple bending effect, the loads must be in the plane parallel to the main axis passing through the shear center, or the load on the element must be supported against torsion at the action points and supports. Cross-sectional parts of the bending moment effect elements shall be classified as compact, non-compact, and delicate, determined from the relevant table in the regulation. The characteristic bending moment strength of the element under bending, Mn, the smallest of the strengths for each boundary condition to be calculated, will be selected. For bending elements,

$$
\mathfrak{Q}\_b = \text{0.90 (LRFD)} \text{ or } \mathfrak{Q}\_b = \text{1.67 (ASD)} \tag{8}
$$

 admissible, the design bending moment strength for LRFD, the bending moment strength for ∅*bMn* or ASD, *Mn*/Ω*b*, will be determined according to the required conditions.

#### *2.2.4 Shear force effect*

 In the shear force effect elements, shear force affected elements, LRFD method for the design of the shear force strength ϕ*vVn*, or ASD method for safe shear force strength *Vn*/Ω*v*. All elements exposed to shear force other than special cases in ÇYTHYE,

$$
\mathfrak{Q}\_v = \text{0.90 (YDRKT)} \text{ or } \mathfrak{Q}\_v = \text{1.67 (GKT)}\tag{9}
$$

 admissible, will be calculated according to the rules given in the regulation. The characteristic shear force resistance Vn will be determined as shown in the regulation.

#### *2.2.5 Compound effects*

The elements under bending (compound oblique bending) and axial force and without torsion or torsion will be designed according to the rules in the relevant chapter.

### **3. Material and methods**

 In this study, Ufuk University pedestrian overpass on Mevlana boulevard in Çankaya district of Ankara was investigated. Measurements of pedestrian overpass were taken with the help of meter and laser meter. The system is modeled in the SAP2000 program. Loads have been added to the system using TS 498 (Design loads for buildings), TS EN 1991-1-3 (Eurocode 1 – Actions on structures—Part 1–3: General actions – Snow loads), and TS EN 1991-1-4 (Eurocode 1 – Actions on structures—Part 1–4: General actions – Wind actions) regulations. Load combinations were first entered according to TS 648. In the program, the system was analyzed by selecting AISC-ASD89 regulation. Then, according to ÇYTHYE, which entered into force in 2016, analysis was made. For the new regulation, analysis was carried out by selecting AISC 360–10 regulation (**Figures 2–4**). Load and resistance factor design was chosen as the method of calculation and load combinations to be used for this calculation method which are defined in the program. Finally, according to the two regulations, the results are compared in terms of performance. All properties are given in **Tables 1**–**3**.

**Figure 2.**  *Location of pedestrian overpass (Google Earth).* 

**Figure 3.**  *General view and bottom and internal views of pedestrian overpass.* 

*The Investigation of the Sustainability of the Existing Steel Pedestrian Overpasses… DOI: http://dx.doi.org/10.5772/intechopen.87836* 

#### **Figure 4.**

*3D and X-Y axis views of pedestrian overpass [12].* 


#### **Table 1.**

*Properties of Ufuk University pedestrian overpass [13–16].* 


#### *ISBS 2019 - 4th International Sustainable Buildings Symposium*


**Table 2.** 

*Load patterns.* 


#### **Table 3.**

*Load combinations.* 

#### **4. Results and suggestions**

After the system was modeled with SAP2000, it was analyzed by two regulations, and the sections were checked for performance.

#### **4.1 Analysis with AISC-ASD89 (TS 648)**

 In the system analyzed by the old regulation, all the sections provided the necessary conditions, and the system was confirmed to be in the safe zone. However, although the system is in a safe zone, the degree of safety is very close to the limit. The most stressed sections were determined to be the L profiles in the middle of the slab. The most stressed L90 × 90 × 9 mm steel profile uses 98% percent of its capacity (**Figures 5** and **6**). The combination that caused the most stress was the "G + Q + Wy + 0.5S" load combination.

*The Investigation of the Sustainability of the Existing Steel Pedestrian Overpasses… DOI: http://dx.doi.org/10.5772/intechopen.87836* 

**Figure 5.**  *Check of structure (AISC-ASD89/TS 648).* 


**Figure 6.**  *Highest stress check information (AISC-ASD89/TS 648).* 

#### **4.2 Analysis with AISC 360-10/LRFD (ÇYTHYE)**

 In the system which is analyzed with the new regulation, errors were detected in almost all sections. Sections are insufficient in terms of slenderness. The Lb value should not exceed 0.095 *r <sup>y</sup>*∗ *E*/(*Ry* ∗ *Fy*), and the slenderness ratio kl/r should not exceed 200 [11, 17, 18]. The "Lb" means "length between points which are either braced against lateral displacement of compression flange or braced against twist of the cross section," "r" means "radius of gyration," and the "kl" value expressed here is "effective length of member." In the old regulation, the limit of slenderness ratio was 250, but in the new regulation, this value was reduced to 200. Therefore, errors in the system can be eliminated by changing these values of the sections. These errors in the system can be eliminated by using the relevant tables in the regulation. These design errors in the system can be resolved by using the relevant tables in the new regulation. Errors are shown in **Figures 7** and **8**.

#### **4.3 Comparison**

As a result, while the system is appropriate according to the old regulation, it is insufficient according to the new regulation. These and similar systems should be reinforced or rebuilt in order not to endanger the safety of life and property (**Figure 9**).

**Figure 7.**  *Check of structure (AISC 360-10/ÇYTHYE).* 

**Figure 8.**  *Design errors.* 

#### **Figure 9.**

*Shear, moment, and axial force graphics on AISC-ASD89 (TS 648) and AISC 360-10 (ÇYTHYE).* 

At the same time, structural deteriorations were detected in the pedestrian overpass. In some areas, the paints were flaked off and corrosion occurred. In these rusty areas, the necessary precautions should be taken before the corrosion proceeds further (**Figures 10** and **11**).

*The Investigation of the Sustainability of the Existing Steel Pedestrian Overpasses… DOI: http://dx.doi.org/10.5772/intechopen.87836* 

**Figure 10.**  *Structural deteriorations.* 

**Figure 11.**  *Ufuk University pedestrian overpass (Google Earth, date: September 2017).* 

Ufuk University overpass is located in one of the most crowded boulevards of Ankara. In those cities with traffic and pedestrian crowd, pedestrian overpasses have great importance. In this respect, pedestrian overpasses should not be forgotten for both pedestrian safety and traffic safety.

#### **Author details**

Gökhan Durmuş\* and Akın Ünal Department of Civil Engineering, Gazi University, Ankara, Turkey

\*Address all correspondence to: gdurmus@gazi.edu.tr

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **References**

[1] Yapı. Steel Structures Should Widespread Use in Turkey. [Internet] 2015. Available from: http://www. yapi.com.tr/haberler/turkiyede-celikyapi-kullanimi-yayginlasmali\_133407. html [Accessed: 2019-02-23] (In Turkish)

[2] Yapı Magazin. Tiryakioğlu NY; The biggest advantage of the steel construction sector is that the steel sector, on the one hand, and the construction sector on the other hand, take place in the common area where the intersects. [Internet] 2016. Available from: http://www. yapimagazin.com/Haber/4528/ prof-dr-nesrin-yardimci-tiryakioglu- %E2%80%9Ccelik-yapi-sektorununen-buyuk-avantaji-bir-taraftan-celiksektorunun-diger-taraftan-insaatsektorunun-kesistigi-ortak-alandayer-almasidir [Accessed: 2019-02-23] (In Turkish)

[3] Yardımcı N. Steel structures in Turkey. Türkiye Mühendislik Haberleri. 2005;**435**:22-24 In Turkish

[4] Yardımcı N. Design and design of steel structures. Türkiye Mühendislik Haberleri. 2005;**435**:46-50 In Turkish

[5] Altay G, Güneyisi EM. Structural steel sector in Turkey and new developments. In: Antalya Region Civil Engineering Problems Congress, 22-24 September, Antalya, 2005. pp. 27-35 In Turkish

[6] Özer E. Developments in steel building design and new turkish earthquake regulation. Türkiye Mühendislik Haberleri. 2016;**492**: 41-46 in Turkish

[7] Özer E. Basic principles of earthquake resistant steel building design and new turkish earthquake regulation. In: 6. Steel Structures Symposium. Eskişehir; in Turkish

[8] Özer E. Under earthquake effect design of steel buildings [Internet]. 2018. Available from: http://www.imo.org.tr/resimler/ dosya\_ekler/894fd882ceb0011\_ ek.pdf?tipi=79&turu=X&sube=15 [Accessed: 2019-02-23] (in Turkish)

[9] Turkish Standards Institution. Building Code for Steel Structures (TS 648:1980). Turkish Standards Institution; 1980 (in Turkish)

[10] Öz D. Steel structures design according to design, calculation and construction requirements of steel structures code and Turkish Building Earthquake Code [MSc thesis]. Eskişehir: Eskişehir Osmangazi University; 2018 (in Turkish)

[11] Ministry of Environment and Urban Republic of Turkey. Design, Calculation and Construction Principles of Steel Structures. Ministry of Environment and Urban Republic of Turkey; 2016 (in Turkish)

[12] SAP2000. Structural Software for Analysis and Design. Computers and Structures Inc

[13] Tekla Structures, Trimble Solutions Corporation

[14] Turkish Standards Institution. Design Loads for Buildings (TS 498:1987). Turkish Standards Institution; 1987 (in Turkish)

[15] Turkish Standards Institution. Eurocode 1—Actions on Structures— Part 1-3: General Actions—Snow Loads (TS EN 1991-1-3:2007). Turkish Standards Institution; 2007 (in Turkish)

[16] Turkish Standards Institution. Eurocode 1—Actions on Structures— Part 1-4: General Actions—Wind Loads (TS EN 1991-1-4:2007). Turkish Standards Institution; 2007 (in Turkish) *The Investigation of the Sustainability of the Existing Steel Pedestrian Overpasses… DOI: http://dx.doi.org/10.5772/intechopen.87836* 

[17] AISC. Seismic Provisions for Structural Steel Buildings (ANSI/AISC 341-16). American Institute of Steel Construction; 2016

 [18] AISC. Specification for Structural Steel Buildings (ANSI/AISC 360-16). American Institute of Steel Construction; 2016

**513**

**Chapter 42**

**Abstract**

fast construction and campus

**1. Introduction**

historical buildings [1].

A Non-Conventional Spatial

Architecture Campus

*Paula Cano Vergara and Caori Takeuchi*

Intervention: Bamboo in a Modern

The increase of fast building development and the need of restructuring heritage

complexes have unleashed as much in strong environmental consequences as set concepts of life expectancy and conservation policies, hence the need to prioritize and drive sustainable development such as constructions of bamboo in configured environments made of concrete and brick as in Universidad Nacional de Colombia (UNAL), a heritage architecture campus which several studies and projects have started to focus on environmental issues and the lack of public space. The Wood and Bamboo Structures Research Group (SEMBU) from the UNAL, Bogota, campus has proposed a *Guadua* bamboo (*Guadua angustifolia*) bus stop with a green roof system, as a partial solution to these problems and a chance to research. The project is a visible structure, which is daily used by a large part of the university community, therefore, making it easier to publicize the effectiveness of the construction with non-conventional materials. This proposal will mark the beginning of a path toward sustainability in building a complex made of architectural language, through the assistance of the transfer of technology and sustainable development in the campus.

**Keywords:** Guadua bamboo structure, sustainable heritage, ephemeral architecture,

A spatial intervention is an interaction between nature, geography, and culture, which exhibits temporary and permanent dynamics. Both dynamics mark territorial identity. For instance, urban space and buildings emphasize customs and are the

Our context, the UNAL, Bogota, campus, is an architectural heritage campus created by the architect Leopold Rother (1936). It was established as a modern architecture paradigm (**Figure 1a** and **b**), divorced from the Spanish colonial and

The campus is located on a 3025-acre area (355,000 sq. meters) (**Figure 2**) in the center of the city, and it is one of the main green areas in Bogota. It has 127 buildings, of which half present serious structural damage, and 17 are registered as

In order to keep the design language and urban configuration, present in our campus' context, spatial interventions are conceived in the following ways: First, there are long bureaucratic processes related to heritage and construction

republican design and construction common in Colombia at that time.

first step toward identifying basic needs related to living.

#### **Chapter 42**
